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  • Articles  (11,700)
  • Chemical Engineering  (11,634)
  • continuous culture  (66)
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  • Process Engineering, Biotechnology, Nutrition Technology  (11,700)
  • 1
    Electronic Resource
    Electronic Resource
    Use of cell cycle analysis to characterise growth and interferon-γ production in perfusion culture of CHO cells (1999)
    Springer
    Cytotechnology 30 (1999), S. 59-69 
    Details
    ISSN: 1573-0778
    Keywords: cell cycle ; CHO ; continuous culture ; flow cytometry ; perfusion culture ; spin-filter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The importance of cell cycle analysis in cell culture development has been widely recognised. Whether such analysis is useful in indicating future performance of high cell density culture is uncertain. Using flow cytometric approach to address this question, we utilised the fraction of cells in the S phase to control specific growth rate and productivity in spin filter perfusion cultures and found a significant increase in the accumulated interferon-γ over that obtained from the nutrient-based controlled fed culture. While a general decrease with time exists in both percentage of S phase cells and specific growth rate, a clear oscillatory behaviour of both parameters is found in perfusion cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008055904642
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  • 2
    Electronic Resource
    Electronic Resource
    Hybridoma cell behaviour in continuous culture under hyperosmotic stress (1999)
    Springer
    Cytotechnology 29 (1999), S. 71-84 
    Details
    ISSN: 1573-0778
    Keywords: bioreactor ; continuous culture ; hybridoma cells ; hyperosmolality ; monoclonal antibody production ; non-producing subpopulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In this paper, we propose an alternative strategy to the ones proposed before (Oh et al., 1993; Øyaas et al., 1994a) to get real increases of global final antibody titer and production at hyperosmotic stress, by reducing the detrimental effect of such a stress on cell growth, and conserving the stimulating effect on antibody production. It consists of cultivating the cells in continuous culture and increasing the osmolality stepwise. In this way, the cells could progressively adapt to the higher osmolality at each step and antibody titers could be nearly doubled at 370 and 400 mOsm kg-1, compared to the standard osmolality of 335 mOsm kg-1. Surprisingly, the stimulation of antibody production was not confirmed for higher osmolalities, 425 and 450 mOsm kg- 1, despite the minor negative effect on cell growth. Intracellular IgG analysis by flow cytometry revealed at these osmolalities a significant population of non-producing cells. However, even when taking into account this non-producing population, a stimulating effect on antibody production could not be shown at these highest osmolalities. It seems to us that osmolality has a significant effect on the appearance of these non-producing cells, since they were not observed in continuous cultures at standard osmolality, of comparable duration and at an even higher dilution rate. The appearance of the non-producing cells coincides furthermore with modifications of the synthesised antibody, as shown by electrophoretic techniques. It is however not really clear if these two observations reflect actually the same phenomenon. Hyperosmolality affects the cell behaviour in continuous culture in multiple ways, independently of the growth rate, counting all at least partially for the observed stimulation of antibody production: acceleration of the amino acid, and in particular the glutamine metabolism, increase of the cell volume, increase of the intracellular pH and accumulation of cells in the G1 cell cycle phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008014909474
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of the use of fortified medium in continuous culture of mammalian cells (1999)
    Springer
    Cytotechnology 31 (1999), S. 243-254 
    Details
    ISSN: 1573-0778
    Keywords: continuous culture ; growth inhibition ; osmolality ; perfusion culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Continuous culture is frequently used in the cultivation of mammalian cells for the manufacturing of recombinant protein pharmaceuticals. In such operations a large volume of medium is turned over each day, especially in the case where cell recycle, or perfusion cultivation, is practiced. In principle, the volumetric throughput of medium can be reduced by using a more concentrated feed while maintaining the same nutrient provision rate. Overall, the medium components are divided into two categories: ‘consumable nutrients' and ‘unconsumable inorganic bulk salts’. In such fortified medium, the concentrations of consumable nutrients, but not bulk salts, are increased. With a stoichiometrically-balanced medium, the large amount of nutrients fed into the culture is largely consumed by cells to give rise to residual concentrations of these nutrients in their optimal range. However, unless care is taken to initiate the continuous culture, overshoot of nutrients may occur during the transient period. The high nutrient concentration during overshoot may be inhibitory by itself, or the resulting high osmolality may retard the growth. Using a mathematical model that incorporates the growth inhibitory effect of high osmolality we demonstrate such a potentially catastrophic effect of nutrient and osmolality overshoot by simulation. To avoid overshoot a controlled nutrient feeding scheme should be devised at the initiation of continuous culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008026613975
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  • 4
    Electronic Resource
    Electronic Resource
    Kinetic characterization in batch and continuous culture of Escherichia coli mutants affected in phosphoenolpyruvate metabolism: differences in acetic acid production (1999)
    Springer
    World journal of microbiology and biotechnology 15 (1999), S. 587-592 
    Details
    ISSN: 1573-0972
    Keywords: Acetic acid production ; carbon metabolism ; continuous culture ; Escherichia coli ; metabolic engineering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The growth kinetics of an Escherichia coli wild type strain and two derivative mutants were examined in batch cultures and in glucose-limited chemostats. One mutant (PB12) had an inactive phosphotranferase transport system and the other (PB25) had interrupted pykA and pykF genes that code for the two pyruvate kinase isoenzymes. In both batch and continuous culture, important differences in acetic acid accumulation and other metabolic activities were found. Compared to the wild type strain, we observed a reduction in acetic acid accumulation of 25 and 80% in PB25 and PB12 strains respectively, in batch culture. Continuous culture experiments revealed that compared to the other two strains, PB25 accumulated less acetic acid as a function of dilution rate. In continuous cultures, oxidoreductase metabolic activities were substantially affected in the two mutant strains. These changes in turn were reflected in different levels of biomass and CO2 production, and in oxygen consumption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008934810150
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  • 5
    Electronic Resource
    Electronic Resource
    Continuous cultivation of the yeast Candida utilis at different dilution rates on pineapple cannery effluent (1999)
    Springer
    World journal of microbiology and biotechnology 15 (1999), S. 115-117 
    Details
    ISSN: 1573-0972
    Keywords: Candida utilis ; pineapple cannery effluent ; continuous culture ; steady-state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Candida utilis was grown on a pineapple cannery effluent in a chemostat at dilution rates ranging between 0.05 and 0.65 h−1 to establish optimal conditions for biomass production and chemical oxygen demand (COD) reduction. Sucrose, fructose and glucose were the main sugars in the effluent. Maximum value for cell yield coefficient and productivity were (0.686, gx/gs) and (2.96, gx/l/h) at a dilution rate of 0.425 and 0.475 h−1, respectively, while maximum COD reduction (98%) was attained at a dilution rate of 0.1 h−1. The maintenance coefficient attained a value of (0.093, gs/gx/h). An increase in dilution rate produced a higher protein content of the biomass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008870228213
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  • 6
    Electronic Resource
    Electronic Resource
    Reassessment of the bioenergetic yield of Arthrospira platensis using continuous culture (1999)
    Springer
    World journal of microbiology and biotechnology 15 (1999), S. 235-238 
    Details
    ISSN: 1573-0972
    Keywords: Arthrospira platensis ; bioenergetic yield ; continuous culture ; irradiance ; specific growth rate ; mixotrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Reassessement of bioenergetic growth yield of Arthrospira platensis was performed by using continuous culture under both autotrophic and mixotrophic conditions. Continuous culture was carried out at dilution rates of 0.017, 0.023 and 0.030 h−1. Under these dilution rates bioenergetic yields ranged between 4.45–6.03 × 10−3 g biomass kJ−1 and between 5.42–7.46 × 10−3 g biomass kJ−1, under autotrophic and mixotrophic conditions respectively. A maximum bioenergetic yield of 8.1 × 10−3 g biomass kJ−1 using an autotrophic culture can be calculated. Pigment accumulation (chlorophyll a and carotenoids) may be related to light irradiance, reaching a maximum pigment concentration under light saturation irradiance. Phycocyanin concentration increased during light limitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008841605798
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of CO2 and osmolality on hybridoma cells: growth, metabolism and monoclonal antibody production (1998)
    Springer
    Cytotechnology 28 (1998), S. 213-227 
    Details
    ISSN: 1573-0778
    Keywords: antibody production ; carbon dioxide ; cell metabolism ; continuous culture ; inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract CO2 partial pressure (pCO2) in industrial cell culture reactors may reach 150–200 mm Hg, which can significantly inhibit cell growth and recombinant protein production. Due to equilibrium with bicarbonate, increased pCO2 at constant pH results in a proportional increase in osmolality. Hybridoma AB2-143.2 cell growth rate decreased with increasing pCO2 in well-plate culture, with a 45% decrease at 195 mm Hg with partial osmolality compensation (to 361 mOsm kg- 1). Inhibition was more extensive without osmolality compensation, with a 63% decrease in growth rate at 195 mm Hg and 415 mOsm kg-1. Also, the hybridoma death rate increased with increasing pCO2, with 31- and 64-fold increases at 250 mm Hg pCO2 for 401 and 469 mOsm kg- 1, respectively. The specific glucose consumption and lactate production rates were 40–50% lower at 140 mm Hg pCO2. However, there was little further inhibition of glycolysis at higher pCO2. The specific antibody production rate was not significantly affected by pCO2 or osmolality within the range tested. Hybridomas were also exposed to elevated pCO2 in continuous culture. The viable cell density decreased by 25–40% at 140 mm Hg. In contrast to the well-plate cultures, the death rate was lower at the new steady state at 140 mm Hg. This was probably due to higher residual nutrient and lower byproduct levels at the lower cell density (at the same dilution rate), and was associated with increased cell-specific glucose and oxygen uptake. Thus, the apparent effects of pCO2 may vary with the culture system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008010605287
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  • 8
    Electronic Resource
    Electronic Resource
    Engineering Chinese hamster ovary (CHO) cells to achieve an inverse growth – associated production of a foreign protein, β-galactosidase (1998)
    Springer
    Cytotechnology 28 (1998), S. 73-80 
    Details
    ISSN: 1573-0778
    Keywords: adenovirus major late promoter ; β-galactosidase ; Chinese hamster ovary cells ; continuous culture ; G1 phase expression ; inverse-growth associated production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Protein synthesis in mammalian cells can be observed in two strikingly different patterns: 1) production of monoclonal antibodies in hybridoma cultures is typically inverse growth associated and 2) production of most therapeutic glycoproteins in recombinant mammalian cell cultures is found to be growth associated. Production of monoclonal antibodies has been easily maximized by culturing hybridoma cells at very low growth rates in high cell density fed- batch or perfusion bioreactors. Applying the same bioreactor techniques to recombinant mammalian cell cultures results in drastically reduced production rates due to their growth associated production kinetics. Optimization of such growth associated production requires high cell growth conditions, such as in repeated batch cultures or chemostat cultures with attendant excess biomass synthesis. Our recent research has demonstrated that this growth associated production in recombinant Chinese hamster ovary (CHO) cells is related to the S (DNA synthesis)-phase specific production due to the SV40 early promoter commonly used for driving the foreign gene expression. Using the stably transfected CHO cell lines synthesizing an intracellular reporter protein under the control of SV40 early promoter, we have recently demonstrated in batch and continuous cultures that the product synthesis is growth associated. We have now replaced this S-phase specific promoter in new expression vectors with the adenovirus major late promoter which was found to be active primarily in the G1-phase and is expected to yield the desirable inverse growth associated production behavior. Our results in repeated batch cultures show that the protein synthesis kinetics in this resulting CHO cell line is indeed inverse growth associated. Results from continuous and high cell density perfusion culture experiments also indicate a strong inverse growth associated protein synthesis. The bioreactor optimization with this desirable inverse growth associated production behavior would be much simpler than bioreactor operation for cells with growth associated production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008069312131
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  • 9
    Electronic Resource
    Electronic Resource
    Biooxidation capacity of the extremely thermoacidophilic archaeon Metallosphaera sedula under bioenergetic challenge (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 617-624 
    Details
    ISSN: 0006-3592
    Keywords: thermoacidophile ; chemolithotroph ; heat shock ; chemical stress ; continuous culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The biooxidation capacity of an extremely thermoacidophilic archaeon Metallosphaera sedula (DSMZ 5348) was examined under bioenergetic challenges imparted by thermal or chemical stress in regard to its potential use in microbial bioleaching processes. Within the normal growth temperature range of M. sedula (70-79°C) at pH 2.0, upward temperature shifts resulted in bioleaching rates that followed an Arrhenius-like dependence. When the cells were subjected to supraoptimal temperatures through gradual thermal acclimation at 81°C (Han et al., 1997), cell densities were reduced but 3 to 5 times faster specific leaching rates (Fe3+ released from iron pyrite/cell/h) could be achieved by the stressed cells compared to cells at 79°C and 73°C, respectively. The respiration capacity of M. sedula growing at 74°C was challenged by poisoning the cells with uncouplers to generate chemical stress. When the protonophore 2,4-dinitrophenol (5-10 μM) was added to a growing culture of M. sedula on iron pyrite, there was little effect on specific leaching rates compared to a culture with no protonophore at 74°C; 25 μM levels proved to be toxic to M. sedula. However, a significant stimulation in specific rate was observed when the cells were subjected to 1 μM nigericin (+135%) and 2 μM (+63%); 5 μM levels of the ionophore completely arrested cell growth. The ionophore effect was further investigated in continuous culture growing on ferrous sulfate at 74°C. When 1 μM nigericin was added as a pulse to a continuous culture, a 30% increase in specific iron oxidation rate was observed for short intervals, indicating a potential positive impact on leaching when periodic chemical stress is applied. This study suggests that biooxidation rates can be increased by strategic exposure of extreme thermoacidophiles to chemical or thermal stress, and this approach should be considered for improving process performance. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 617-624, 1998.
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  • 10
    Electronic Resource
    Electronic Resource
    Transportation of hazardous wastes (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 61-67 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Risk assessments have been performed to determine the risk associated with the transportation of hazardous wastes through a city. In the course of these assessments, a number of modeling issues arose relating to transportation accident rates, the characterization of incidents, the effect of thermal radiation, the impact of exposure to toxic chemicals, and the threshold for acceptable risk. This paper discusses these issues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prs.680170112
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  • 11
    Electronic Resource
    Electronic Resource
    Process safety update (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. S3 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prs.680170202
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  • 12
    Electronic Resource
    Electronic Resource
    Burst resistant ribbon wound pressure vessels for ammonia plants (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 98-103 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents the design of ribbon wound pressure vessels useful for Ammonia, Urea and Methanol plants. The design is to create a thin shell of 1/5 the total wall thickness required, weld it to the end pieces, and wind 4 to 8 mm thick ribbons of 80 mm width at an angle of 15 to 30 degrees on the inner shell, using a prestress. The ribbons are welded at the ends and an even number of layers are wound cross-helically on to the shell. With more than 7000 vessels over the pressure range of 50 to 350 atmospheres in use in the various chemical industries in China over the past 30 years, their safety record has been excellent. Of particular interest has been the application of this technology in the Ammonia and Urea plants, where the design allows fabrication of these vessels at substantial reduction in cost, and early delivery, when compared to the mono wall technology.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prs.680170205
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  • 13
    Electronic Resource
    Electronic Resource
    Safety surveys - looking at key activities in depth (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 20-22 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Most audits try to look at a representative selection of the plant procedures and equipment. An alternative is a survey, a look in depth at selected procedures (such as those for testing alarms and trips, issuing permits-to-work, controlling modifications, taking samples or testing relief devices) or selected equipment (such as level glasses or equipment for handling LPG). If the procedure or equipment is well-chosen, surveys may make a bigger contribution to safety, per person-hour, than a conventional audit.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prs.680170106
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  • 14
    Electronic Resource
    Electronic Resource
    Pressure relief system documentation: Equipment based relational database is key to OSHA 1910.119 compliance (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 39-42 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Under OSHA 1910.119, all Process Safety Management (PSM) facilities are required to keep their pressure relief system design information current. This article demonstrates why a pressure relief system design verification effort must be based on an equipment list, rather than a relief device list, in order to ensure that every piece of equipment is adequately protected. The formerly common practice of simply checking the design bases of all existing relief devices is deficient is deficient since this technique does not systematically ensure that every piece of equipment is protected.The “Berwanger Method” is a step by step process for designing or analyzing a pressure relief system to meet OSHA 1910.119 Process Safety Information (PSI) and Process Hazard Analysis (PHA) mandates. The method uses a relational database which tracks the relationships between protected equipment, potential overpressure scenarios, and protective devices.The challenge facing an operating company does not end once the design basis has been “verified” - the design basis information must also be maintained and be readily accessible to avoid costly reinvention of the wheel down the road. The “Berwanger Method” also addresses these maintenance issues.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prs.680170109
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  • 15
    Electronic Resource
    Electronic Resource
    A detailed reaction study of phosphorus trichloride and water (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 49-60 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper reports on a comprehensive literature search and small scale experimental work on the reaction characteristics of phosphorous trichloride and water. More than 30 tests were conducted, including both closed and open test cells. The water to phosphorus trichloride molar ratio was varied from 1 to 25. When in contact, water and phosphorus trichloride will form two liquid layers with a reaction starting at the interface. The impact of variables on reaction rates including the interface surface area, layer depth, and stirring were investigated experimentally. A reaction rate model that fits all the measured data is presented. Case studies illustrating the use of this data for emergency relief systems and vent containment design are presented in reference. [1].
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    URL: http://dx.doi.org/10.1002/prs.680170111
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  • 16
    Electronic Resource
    Electronic Resource
    The influence of the geometry of the hot surfaces on the autoignition of vapor/air mixture: Some experimental and theoretical results (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 68-73 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two major accidents in the 80's: the summit Tunnel Fire, England and Piper Alpha disaster, an offshore platform in the North Sea; and very recently, possible explosion of the Boeing, TWA flight 800 at New York, makes it imperative that further research into the mechonisms of the ignition of flammable vapor/air mixture in contact with hot surfaces needs to be done. There have been a number of studies of ignition by hot surfaces, but in all these studies the ignition sources were wire, sphere or strip, i.e., most of them were flat surfaces. But to the authors' knowledge, other variables which affect the ignition mechanism such as irregular geometrical shapes have not been studied. The purpose of this paper is to examine how the degree of confinement (or, configuration), size and orientation, of the heated surface affects the ignition temperature of the flammable vapors. The results were obtained by experimentnal and by computational fluid dynamics.
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    URL: http://dx.doi.org/10.1002/prs.680170113
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  • 17
    Electronic Resource
    Electronic Resource
    Plasmid stability of recombinant Pseudomonas sp. B13 FR1 pFRC20P in continuous culture (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 62-70 
    Details
    ISSN: 0006-3592
    Keywords: plasmid stability ; recombinant microorganism ; continuous culture ; Pseudomonas sp. B13 FR1 pFRC20P ; degradation of aromatic compounds ; chlorobenzoate ; methylbenzoate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Plasmid stability of recombinant Pseudomonas sp. B13 FR1 pFRC20P, a strain capable of mineralizing 3- and 4-chlorobenzoate and 4-methylbenzoate, was investigated in continuous culture. The hybrid cosmid pFRC20P enables the strain to mineralize 4-methylbenzoate. Rapid plasmid loss was observed under nonselective conditions using 3-chlorobenzoate as the substrate. Plasmid stability decreased with increasing dilution rate. Despite the growth advantage of the generated plasmid free cells a total depletion of plasmid bearing cells was not observed. After approximately 50 generations the fraction of plasmid bearing cells reached a constant level of 10%, which was stably maintained during the next 25 generations. Cells from this stage were used to inoculate a new culture that resulted in a stable level of 50% plasmid bearing cells. By a temporary substrate change to selective conditions (4-methylbenzoate), this level could be further increased to 70%. Literature models on plasmid stability could not be applied to describe the experimental data. Therefore, a new but unstructured model was developed to describe the experimental results. The model is based on the existence of three subpopulations: a plasmid free one, an original plasmid bearing one with a growth disadvantage compared to plasmid free cells, and a second plasmid bearing subpopulation with increased stability that is generated from the original one and has a growth rate comparable to the plasmid free cells. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 62-70, 1998.
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  • 18
    Electronic Resource
    Electronic Resource
    Activity and stability of a recombinant plasmid-borne TCE degradative pathway in suspended cultures (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 287-296 
    Details
    ISSN: 0006-3592
    Keywords: expression ; plasmid ; stability ; TCE ; continuous culture ; activity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The retention and expression of the plasmid-borne, TCE degradative toluene-ortho-monooxygenase (TOM) pathway in suspended continuous cultures of transconjugant Burkholderia cepacia 17616 (TOM31c) were studied. Acetate growth and TCE degradation kinetics for the transconjugant host are described and utilized in a plasmid loss model. Plasmid maintenance did not have a significant effect on the growth rate of the transconjugant. Both plasmid-bearing and plasmid-free strains followed Andrews inhibition growth kinetics when grown on acetate and had maximum growth rates of 0.22 h-1. The transconjugant was capable of degrading TCE at a maximum rate of 9.7 nmol TCE/min · mg protein, which is comparable to the rates found for the original plasmid host, Burkholderia cepacia PR131 (TOM31c). The specific activity of the TOM pathway was found to be a linear function of growth rate. Plasmid maintenance was studied at three different growth rates: 0.17/h, 0.1/h, and 0.065/h. Plasmid maintenance was found to be a function of growth rate, with the probability of loss ranging from 0.027 at a growth rate of 0.065/h to 0.034 at a growth rate 0.17/h. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 287-296, 1998.
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  • 19
    Electronic Resource
    Electronic Resource
    Kinetic models for the growth of Escherichia coli with mixtures of sugars under carbon-limited conditions (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 99-107 
    Details
    ISSN: 0006-3592
    Keywords: Monod kinetics ; mixed substrate growth ; continuous culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In natural environments, heterotrophic microorganisms encounter complex mixtures of carbon sources, each of which is present only at very low concentrations. Under such conditions no significant growth could be expected if cells utilized only one of the available carbon compounds as suggested by the principle of diauxic growth. Indeed, there is much evidence that microbial cells utilize many carbon sources simultaneously. In order to predict bacterial growth under such conditions we developed a model describing the specific growth rate as a function of the individual concentrations of several simultaneously utilized carbon substrates. Together with multisubstrate models previously published, this model was evaluated for its ability to describe growth of Escherichia coli during the simultaneous utilization of mixtures of sugars in carbon-limited continuous culture. Using the μmax and Ks constants determined for single substrate growth with six different sugars, the model was able for most experiments to adequately describe the specific growth rate of the culture, i.e., the experimentally set dilution rate, from the measured concentrations of the individual sugars. The model provides an explanation why bacteria can still grow relatively fast under environmental conditions where the concentrations of carbon substrates are usually extremely low. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:99-107, 1998.
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    Multiplicity and stability analysis of microorganisms in continuous culture: Effects of metabolic overflow and growth inhibition (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 251-261 
    Details
    ISSN: 0006-3592
    Keywords: continuous culture ; metabolic overflow ; multiplicity ; stability analysis ; dynamics ; growth inhibition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Metabolic overflow (enhanced uptake of substrate and secretion of intermediates) is a phenomenon often observed for cells grown under substrate excess. Growth inhibition by substrate and/or product is also normally found for this kind of culture. An effort is made in this work to analyze the dynamic behavior of a continuous culture subject to metabolic overflow and growth inhibition by substrate and/or product. Analysis of a model system shows that in a certain range of operating conditions three nonwashout steady state solutions are possible. Local stability analysis indicates that only two of them are stable thus leading to multiplicity and hysteresis. Further analysis of the intrinsic effects of different terms describing the metabolic overflow and growth inhibitions reveals that for the model system and the parameters considered, the combined effects of product inhibition and an enhanced formation rate of product under substrate excess cause the multiplicity and hysteresis. Growth inhibition by substrate and/or an enhanced substrate uptake appear not to be necessary conditions. The combined effects of enhanced product formation and product inhibition can also lead to unusual dynamic behavior such as a prolonged time period to reach a steady state, oscillatory transition from one steady state to another, and sustained oscillations. Using the occurrence of multiplicity and oscillation as criteria, the operating regime of a continuous culture can be divided into four domains: one with multiplicity and oscillation, one with unique steady state but possible oscillatory behavior, the other two with unique and stable steady state. The model predictions are in accordance with recent experimental results. The results presented in this work may be used as guidelines for choosing proper operating conditions of similar culture systems to avoid undesired instability and multiplicity. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 251-261, 1998.
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    Process safety update (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. S3 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prs.680170102
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    KG: New data and analysis (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 9-15 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The design and deflagration pressure relief vents is based on correlations developed for various types of combustible materials and for enclosures of different strengths. The primary guideline for deflagration vent design in the US is NFPA 68 Guide for Venting of Deflagrations [5]. That document gives guidance for the design of vents for enclosures containing flammable gases, specifically hydrogen, coke oven gas, propane, and methane. Application of the guide to other gases is achieved using the KG value. Values of KG are published for a relatively small number of gases, as seen in Table D-1 of NFPA 68. This work present KG data on several additional gases obtained in a laboratory scale test vessel along with analysis of the results with respect to published values of fundamental burning velocity.
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    NFPA 30: An update and a look into the future (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 23-31 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In May 1996, the Flammable and Combustible Liquids Code Committee of the National Fire Protection Association (NFPA) proposed for adoption by the Association a new edition of NFPA 30, Flammable and Combustible Liquids Code. This new edition was the culmination of two and one-half years' work by the Committee and included one of the most significant changes to that document in some twenty years: the incorporation of mandatory fire protection criteria for warehouses and other inside areas that store flammable and combustible liquids in containers and portable tanks.
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    Risk based prioritization of maintenance repair work (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 32-38 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper describes the development of a risk ranked Inspection Recommendation procedure that is used by one of Exxon's chemical plants to prioritize repairs that have been identified during equipment inspection.As part of the Company's Safety Management Practices initiative in the late 1980's a procedure was put into place to ensure that an Inspector's repair recommendations were properly addressed by the organization. The initial procedures were successful at “systematizing” the documentation and stewardship-to-completion of the Inspector's recommendation, however, there were complications with the original process: (1)The Inspector made a simple High, Medium or Low assessment of the priority/criticality of the recommendation. Frequently, this resulted in disagreements with Operations about the true priority of the recommendation.(2)If there was agreement on the priority of the recommendation, there was still disagreement on the relative rank within the priority-which high priority was the highest priority?(3)With limited funds to spend on repairs, it was (and is) important to make sure that the money was being spent on the highest risk items that had the greatest risk reduction/cost benefit ratio.To address these concerns, the procedure was modified to incorporate a risk assessment of the recommendation by both the Inspector and Operations. In the new procedure, the Inspector describes the deficiency that he/she finds and assesses the probability of failure within a certain time-frame. Operations must assess the consequences, from an environmental, safety and economics standpoint, were the failure to occur. These assessments are combined in the typical risk equation (risk = probability × consequences) to arrive at a severity index which serves to rank the recommendation relative to the other recommendations. Because Operations participates in the assessment there is very little disagreement about the priority of the recommendation. The severity index puts the recommendations in order so it is quite clear which are the highest priority recommendations. This process has helped to focus the entire organization on those deficiencies that represent the greatest risk with the result that less time and money is spent correcting items that have a low risk/cost benefit ratio, allowing these savings to be used to reduce the higher risks in the plant.
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    Short communication: Estimating the minimum ignition energy of hybrid mixtures (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 124-126 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple analytical method is presented for estimating the hybrid minimum ignition energy (HMIE) of dust-gas mixtures, based on the assumed generality of Bartknecht's well-known test data for mixtures of propane with a series of dusts in air. Since the HMIE equation requires input data which might be unavailable, the use of conservative default methods is discussed.
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    Flammability hazards of lower aliphatic aldehydes at elevated pressure and temperature (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 138-148 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A large and potentially hazardous decrease in aldehyde autoignition temperature (AIT) occurs with increased pressure. The AIT-pressure curve determined in a 5 L stainless steel sphere was similar for propionaldehyde and butyraldehyde in air, falling from about 185°C at atmospheric pressure to 90°C at 140 psia. Reduction of oxygen concentration had little effect on propionaldehyde AIT. At 100°C and 140 psia, autoignitions accompanied by at least a doubling of pressure were observed above 4% oxygen. In the presence of a few grams of free liquid, propionaldehyde vapor ignited in air at initial conditions significantly below the AIT. The mechanism appears to involve rapid Fe-catalyzed exothermic liquid-phase oxidation leading to autoignition of the adjacent heated gas layer. An acetaldehyde vapor-air mixture in the presence of free liquid and rust exploded at room temperature when air pressure was increased to 95 psia; this result is discussed with reference to a cylinder overpressurization that occurred while making up an ostensibly sub-LFL calibration mixture with compressed air. Propionaldehyde's limiting oxygen concentration (LOC) was investigated in the near-autoignition region using the same 5L apparatus; the findings are discussed with reference to an overpressurization incident in an air-liquid partial oxidation reactor. The general results are used to illustrate the application of LOC in partial oxidation processes subject to autoignition and to discuss elements of the current ASTM draft test method for LOC, which does not address test difficulties associated with condensable and/or reactive gas systems.
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    Process safety update (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. F3 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    URL: http://dx.doi.org/10.1002/prs.680170302
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    Multivariate hazard identification and ranking system (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 157-170 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Risk analysis in chemical process industries is an elaborate exercise involving several steps from preliminary hazard identification to development of credible accident scenarios, to preparation of strategies for prevention or control of damage.All this requires substantial inputs of time and money. In order to get an approximate yet workable assessment of risk at much lesser costs, indices have been developed which link typical findings of elaborate risk analysis to scales of risk. The scales, in turn, provide workable measures of hazards/risks/safety.In the past, indices have been reported for swift risk assessment - the noteworthy among them include Dow fire and explosion index, Mond fire, explosion and toxicity index, IFAL index, and mortality index. A few rapid ranking techniques have also been proposed.This paper presents a new system of methodologies for Hazard Identification and Ranking (HIRA). The system consists of two indices: one for fire and explosion hazards and another for the hazard due to likely release of toxic chemical. The magnitudes of these indices indicate the severity of the likely accident; in terms of the size of the impacted area.HIRA has been applied to a typical chemical process industry - a sulfolane plant - and its performance has been compared with that of the Dow's and the Mond's indices. The study reveals that HIRA is more sensitive and accurate than the other indices.
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    Experiences with non-destructive testing of static equipment in ammonia plants at DSM (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 200-208 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    Analysis of hydrogen fluoride release at Texas city (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 213-218 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: On October 31, 1987 a crane lifting a heat exchanger convection section failed and severed a 4″ loading line and a 2″ pressure relief line to an HF alkylation reactor settler drum at a petroleum refinery in Texas City, Texas. Vapors were emitted under pressure for about two hours and the vessel was plugged and drained aproximately 44 hours later. A plume from this accidental release passed through residential areas, damaging some vegetation (brown lawns), and spawning a class action law suit. An extensive analysis was conducted to determine the total inventory loss and to model the blowdown process and the concentrations of HF in the plume. Since the discharge rate was decreasing with time, a peak concentration of HF in the emitted vapors occurred just before the water spray mitigation system became fully operative. Consequently, the mitigation efforts were more effective late in the response when concentrations were already low. The predicted plume concentrations are consistent with observed vegetation damage effects, with concentrations below Emergency Response Planning Guideline Level 3 past 3/4 mile from the source. These results support a policy of sheltering in place during such an event.
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    Peroxide drum explosion and fire (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 225-231 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A fifty-five gallon steel drum of a liquid organic peroxide pressurized and ruptured in the mix room of a manufacturing plant. The head of the drum blew off and the ejected material ignited. The resulting fire was extinguished by the building sprinkler system and operating personnel. Although there were no injuries, the fire caused significant damage in the mix room. The investigation of this incident, its likely cause, and the corrective actions will be discussed.
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    Making RMP hazard assessment meaningful (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 238-242 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Brazoria County Petrochemical Council, 13 companies that are working together to enhance relations between industry and the community, united in a joint effort at complying with the EPA's Risk Management Program. One of the significant issues the group had to address was the need to develop meaningful hazard assessment for presentation to the public. The EPA's “Table Look-Up Approach” found in the Offsite Consequence Analysis Guidance document is certainly a good tool; however, the built-in conservatism results in over-estimates of potential hazard areas. Much more meaningful results are shown to be obtained using one of the hazard release models.The value of using a credible scenario with realistic meteorological data is demonstrated through the consistently smaller areas predicted by the PHAST Model for planning purposes. Realistic scenarios/failure modes and realistic model parameters are important so that the risk to the public is not overstated. Proprietary models such as PHAST are invaluable in providing more meaningful consequences for planning purposes.
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    The effects of valve wheel size, operation position and in-line pressures on required torque for gate valves (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 263-271 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Some of the hazards encountered by process plant operators involve the operation of in-line valves to control, start, and to stop flow. Torque required to operate valves may vary according to valve wheel size, in-line pressure, and valve flange position (open/closed). This study determined how valve wheel size, in-line pressure and valve position (open/closed) affect torque required to actuate a valve. Data were gathered with each combination of size, pressure and position for 336 valves in an operating petrochemical process facility. The results indicate that the main effects of valve wheel size, the in-line pressure, and open/closed valve position significantly affect operational torque requirements. In addition, the interaction between position and pressure was significant for operational torque. The implication of these results is that operators are exposed to operational torque requirements that exceed maximum acceptable capabilities that have been determined in previous studies.
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    Measures taken to ensure safe operation of an ammonia storage tank (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 288-296 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An ammonia storage tank was built at the BASF Antwerp site in 1969 on land reclaimed from the sea. After several years of operation uneven foundation settlement, of up 2, occurred. In order to assure stability of this area for the next operation period (at least 10 years) measures were taken to ensure continued safe operation. One key measure was strain gauge monitoring at the location of maximum stress.
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    Recent developments in the Baker-Strehlow VCE analysis methodology (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 297-301 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Baker-Strehlow methodology was developed to provide an objective approach to prediction of blast pressures from vapor cloud explosions. The complete methodology was first published in 1994 [1]. Since then, it has evolved through ongoing research and use in VCE hazard analyses, facility siting studies and accident investigations. This article gives a brief overview of a paper on recent developments in the Baker-Strehlow methodology presented at the 31st Loss Prevention Symposium in Houston on March 9-13, 1997. Because the entire paper is too lengthy to be presented here, the following discussions may be lacking in some details. A copy of the complete paper can be obtained from the American Institute of Chemical Engineers (AIChE).Since the Baker-Strehlow method was first published, it has been used extensively in VCE hazard assessments in refineries and chemical plants. As expected, many practical lessons have been learned during the course of the hazard assessments, and the Baker-Strehlow method has evolved as a result. The changes have been evolutionary, not revolutionary. In keeping with the goals of the original study in which the methodology was developed, all changes have been incorporated with the intent of achieving an objective methodology to provide consistent prediction of VCE blast effects.The revisions to the Baker-Strehlow method resulting from experience gained during plant walk-downs and hazard assessments include: Systematic identification of “potential explosion sites” or “PESs,”Selection of the level of confinement for mixed zones of 2D and 3D confinement,Deciding on flame expansion when confinement is elevated above the vapor cloud,Selecting the reactivity for a fuel that is a mixture of fuels with differing reactivities,Predicting blast loads when there are multiple PES's within a vapor cloud considering different ignition source locations.
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    Safety, health and loss prevention in AIChE (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 83-85 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Safety, health and loss prevention are major areas of interst for the American Institute of Chemical Engineers (AIChE). There has been an evolution of these concerns over the years in the Institute just as it has in industry. This article chronicles this evolution.
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    Masthead (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998) 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    URL: http://dx.doi.org/10.1002/prs.680170101
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    Improving the effect of atmospheric stability class for dispersion modeling (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 1-8 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recent guidelines released by the U.S. EPA define a worst-case scenario as a release under stable atmospheric conditions defined as Pasquil-Gifford stability class F. Unfortunately, very few tests at F stability have been available heretofore to provide a basis for models. Recent test data with propane releases by the German research organization TUV provide a set of 60 experiments conducted specifically to define the effects of atmospheric stability class on dispersion. Of these, 25 tests were at F stability. A comparable number were at each other stability class A through E. In addition 23 tests were at wind speeds under 1.5 m/s in stable atmospheres. This paper reports on adjustments made to our models based on these new data by reducing the originally-postulated sensitivity to stability class. In spite of considerable scatter in the TUV data, particularly between two different types of propane analyzers, the model allows us to extract information by averaging over the tests.
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    Vent access restriction for solids handling systems (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 16-19 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A multi-disciplinary team developed a guideline for determining access restriction zones around vented solids handling equipment. The guideline provides a method for ensuring the discharge from a vented explosion will not cause injury to personnel. The steps in this method include: calculating the extent of external hazards from vented explosions; identifying potential areas where personnel could be exposed to a hazard; identifying ways to eliminate or reduce the hazard area; and establishing and documenting any access restrictions needed. Hazard zone calculations use the latest knowledge from research into fireball size, flame length and external pressure equations in VDI 3673. The guideline provides guidance for using this information. Options for mitigating or reducing external hazards from vented explosions are also described. As part of the project, the team audited several solids handling systems to look for potential oversights in existing restricted access areas. Some of the team's learnings from these audits are reviewed.
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    Team situation awareness for process control safety and performance (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 43-48 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper defines situation awareness (SA) and discusses its importance to operator-machine system safety and functioning in the context of process control activities. Specifically, identified are relationships of human detection of critical process cues converying the status of automated control systems and operator interpretation of the meaning and relevance of such information to the potential for negative incidents in chemical processing. Beyond individual operator SA in interacting with control systems, intra- and inter- work team SA are discussed for supporting individual attainment of process control responsibilities. Factors critical to team SA are discussed. “Road blocks” to team SA are also analytically examined. Lastly, methods for assessing individual and team SA are reviewed and vehicles for relating outcomes of these methods to changes in process control operator and team behavior to improve human-machine system safety and performance are relayed.
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    Masthead (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998) 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prs.680170201
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    Determination, prevention and mitigation of potential hazards due to the handling of powders during transportation, charging, discharging and storage (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 74-81 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The knowledge of the ingition behavior of dust-air mixtures due to electrical sparks (MIE, Minimum Ignition Energy) and hot surfaces (MIT, Minimum Ignition Temperature) is important for risk assessments in chemical production plants. The ignition behavior determines the extent and hence the cost of preventive protection measures.This paper describes the use of the minimum ignition energy and minimum ignition temperature as very important safety indexes in practice.Based on the latest results from large scale experiments on pneumatic filling of silos with polymeric materials and new results of full scale filling tests using Flexible Intermediate Bulk Containers (FIBC) manufactured from a variety of materials, guidance can be given to ensure safe operation in different situations such as filling, emptying operations, type of powder handled.The aim of this paper is to assist people dealing with product. It reflects the present state of the art and current knowledge of the assessment and measures associated with powder handling.
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    Integrating hazard analysis into the implementation of advanced process control (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 104-106 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In mid-1997, an Advanced Process Control (APC) scheme was implemented at a resins manufacturing complex with the goal of minimizing flare fuel gas usage while maintaining sufficient energy (BTU/SCF flare gas) to be in environmental regulatory compliance. Prior to APC implementation, the flare system was manually controlled by plant operators with minor attention paid to the minimization of fuel gas usage. Since implementation, APC has saved the plant thousands of dollars in fuel gas costs and reduced unnecessary combusted fuel gas emissions.Hazard analysis techniques were used in the development of the control scheme. An overview of the APC used, the economic evaluation, and the hazard analysis techniques used in the project are presented here.
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    Models for domino effect analysis in chemical process industries (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 107-123 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the risk assessment parlance, especially with reference to chemical process industries, the term “domino effect” is used to denote “chain of accidents,” or situations when a fire/explosion/missile/toxic load generated by an accident in one unit in an industry causes secondary and higher order accidents in other units. The multi-accident catastrophe which occurred in a refinery at Vishakhapatnam, India, on September 14, 1997, claiming 60 lives and causing damages to property worth over Rs 600 million, is the most recent example of the damage potential of domino effect.But, even as the domino effect has been documented since 1947, very little attention has been paid towards modeling this phenomena. In this paper we have provided a conceptual framework based on sets of appropriate models to forecast domino effects, and assess their likely magnitudes and adverse impacts, while conducting risk assessment in a chemical process industry. The utilizability of the framework has been illustrated with a case study.
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    Masthead (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998) 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prs.680170301
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    Fire tests of rack storage of water miscible liquids in plastic containers (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 149-154 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article deals with fire protection for water miscible flammable liquids stored in plastic containers packaged in boxes located on pallets. A series of fire tests was conducted with palletized rack storage arrangements using in-rack sprinkler protection at various levels. The intent of the paper is to present data from this test series for these types of commodities. The paper will identify various existing water miscible flammable liquid products stored in this fashion and provide background information for protecting this type of storage as it relates to NFPA 30 Flammable and Combustible Liquids Code. The test data indicates that further research work is needed in the area of plastic containers for use with the storage of combustible and flammable liquids. Included in the paper are discussions concerning possible protection strategies and suggestions for future research which would benefit those involved in risk management of this type of commodity.
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    Application of the flammability diagram for evaluation of fire and explosion hazards of flammable vapors (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 176-183 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The safest method to prevent fires and explosions of flammable mixtures in the first place. This method requires detailed knowledge of the flammability region as a function of the fuel, oxygen, and nitrogen concentrations. A triangular flammability diagram is the most useful tool to display the flammability region, and to determine if a flammable mixture is present during plant operations.This paper describes how to draw and use a flammability diagram. A procedure to estimate the flammability region using the available and sometimes limited data is discussed. The paper also shows how to use the flammability diagram with plant operations involving inerting and purging, and from bringing vessels into and out of service. A compilation of flammability diagrams for 30 materials, based on previously published data is provided.An automated apparatus for acquiring data for a flammability diagram is described. The apparatus consists of a 20-L sphere with an automated gas mixing system, a fuse-wire ignition system, and a high speed pressure measurement and data acquisition system. Data derived from the apparatus includes flammability limits, maximum pressure during combustion, and the maximum pressure rate. The effect of fuse-wire ignitor dynamics on the results is studied. A flammability diagram for methane drawn from data obtained from the apparatus, is presented.
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    A model for the calculation and the verification of closed cup flash points for multicomponent mixtures (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 86-97 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Regulatory issues related to material safety have made the accurate measurement and/or prediction of flash points essential. The flash point is one of the major physical properties used to determine the fire and explosion hazards of a liquid. Flash points are used by virtually all governmental entities worldwide to define “flammable” and “combustible” materials for shipping and safety regulations.A model is described here for the calculation of closed cup flash points for multicomponent, single liquid phase, mixtures. The model is based upon rigorous vapor/liquid equilibrium calculations supplemented with information about the lower flammable limits (LFL's) and heats of combustion (ΔHc's) for the mixture's constituent components. The closed cup flash points predicted with this model are typically within ± 5°C of the experimentally reported values. Such a model is useful as a means of verifying experimental data and as a tool for screening product formulations prior to experimental flash point determination. The model should considerably enhance the safety evaluation portion of the product development cycle, thus leading to shortened product time-to-market cycles. While flash points calculated with this model are in excellent agreement with experiment, experimental determination is still encouraged for critìcal safety applications.
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    Emergency planning: Critical evaluation of proposed AEGLs for ammonia (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 134-137 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: National Advisory Committee's Acute Exposure Guideline Levels (AEGLs) for ammonia are critically evaluated. The technical bases for concern about AEGL-2 and AEGL-3 values derived by the committee are summarized recommendations made.
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    Investigation of an explosion and flash fire in a fixed bed reactor (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 127-133 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An explosion and flash fire in a fixed bed reactor occurred at a municipal wastewater treatment plant (WWTP). Two employees were injured in the accident. The accident occurred in an ozone treatment building where ozone was used to treat odors from the offgas of the sludge concentration units. Excess ozone manually was routed to the fixed bed reactor (ozone destruct unit) where the ozone is catalytically transformed into oxygen before being discharged to the atmosphere.An investigation of the accident was conducted to determine the root cause of the explosion and flash fire and identify corrective actions which the WWTP management could undertake to prevent a recurrence. This investigation included site inspections, interview with the injured employees, sampling and analysis of various materials, an explosion dynamics analysis, and a root cause analysis.It was concluded that cooling oil from one of the ozone generation units entered the main ozone gas line due to a crack in one of the reactor's dielectric tubes. The cooling oil was vented into the ozone destruct unit when an employee opened a ball valve on the main ozone gas line. The cooling oil, essentially a saturated hydrocarbon mixture, reacted exothermically when it contacted the manganese dioxide catalyst. The exothermic reaction resulted in an explosion which propelled the access panel outwards and dispersed the catalyst pellets. A flash fire followed the explosion. The flash fire burned two employees and caused thermal damage to a nearby control panel.Although this accident was the first of its kind at this facility, this was not the first time that the ozone generator had experienced a failure of a dielectric tube. Thus, there was a significant probability that a dielectric tube failure could leak cooling oil into the main ozone gas line. This failure event could, in turn, result in another explosion and flash fire. The WWTP staff neither designed nor fabricated the ozone generator-destructor system. Therefore, it did not seem appropriate for the WWTP staff to modify the ozone system. Instead, it was recommended that the ozone destruct unit be taken out of service. The WWTP management acted on this recommendation.
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    Investigation of a steam explosion in a petroleum product storage tank (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 171-175 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An explosion occurred in a petroleum product storage tank at a refinery. The liquid petroleum product was a heavy oil used as an asphalt extender. There were no injuries, but the cleanup was costly. The storage tank was one of several which received the product stream from a dehydration unit. The accident occurred shortly after the refinery was brought back on-line following a shutdown for schduled maintenance.This was the first incident of this kind to occur at this facility. Analysis of the process data and eyewitness observations indicated that the dehydration tower, which was supposed to be maintained at a minimum of 100°C during the shutdown, was allowed to drift below 100°C for an unknown period of time. This deviation enabled liquid water to enter the storage tank. Three operational factors contributed to the accident. Corrective actions were recommended to prevent a recurrence of a similar incident.
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    Dust explosion mitigation using Q-Rohr and exkop (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 184-189 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dust explosions have been with us for a long time. The first record of a dust explosion occurred in Turin, Italy, on December 14, 1785 [1]. The detailed record of this event is left to us by Count Morozzo. The event took place in Mr. Giacomelli's bakery. We know from his account that the weather was unseasonably dry, that a boy who worked in the bakery was using a shovel to stir and transfer the flour to a chute from a store room to the bakery and he had a lighted lamp to work by. The rest, as the saying goes, is history. No one was killed, and the building was saved by the sagacious fact of having plenty of windows. Since that first record, of course, there have been many explosions with much loss of life and significant economic consequences.
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    The reactive system screening tool (RSST): An easy, inexpensive approach to the DIERS procedure (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 190-195 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The RSST DIERS vent sizing methodology is revised to provide realistic design equations for reactive systems consistent with available large-scale experience. Using easy to obtain RSST data such as rate of temperature rise and rate of pressure rise excellent agreement is illustrated for hybrid, vapor and gassy reactive systems.
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    Making safety second nature (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 196-199 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: From the 1960s onwards, the chemical and oil industries developed and used a number of new safety techniques which, in time, became second nature to those who applied them. They included the use of QRA for deciding priorities, Hazop and audits for identifying problems, inherently safer design for avoiding hazards, and more thorough investigation of incidents for identifying underlying causes. However, it has not yet become second nature to remember the accidents of the past and the actions needed to prevent them happening again.I joined industry in 1944 and moved to production in 1952. Then, and for at least 15 years afterwards, safety was a non-technical subject that could be left to arts graduates and elderly foremen. There was concern that people should not be hurt - great attention was paid to the lost-time accident rate - but there was no realization, that it was a subject worthy of systematic study by experienced technologists.This view changed at the end of the 1960s. A new generation of plants had been built, operating at higher temperatures and pressures and containing larger inventories of hazardous chemicals; the result was a series of fires and explosions and a worsening fatal accident rate. Figure 1 shows the situation in ICI, at the time the UK, s largest chemical company. Other companies experienced a similar state of affairs.As a result in 1968, I was appointed one of the company's first technical safety advisers, an unusual appointment at the time for someone with my experience, and if the reason for my appointment had not been so obvious I would have wondered what I had done wrong. I and my colleagues tried to apply the same sort of systematic thinking to safety that we applied in our other professional work. We developed some new concepts and techniques and adopted others. A common feature of our ides, realized only in restrospect, was that they consisted of more than mere problem-solving techniques. Once people had got used to these new concepts and used them a few times, they began to look at a whole range of problems in a different way.
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    Process safety update (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. W3 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prs.680170402
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    Case studies of incidents in runaway reactions and emergency relief (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 259-262 
    Details
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Case histories of 65 incidents in runaway reactions and emergency relief in Taiwan were analyzed and classified into several categories according to their causes, materials involved, equipment types, reaction types, and ignition sources. The cases in reactors and storage tanks were examined in more detail owing to the higher probability or larger potential hazard in these two types of equipments. The most common consequence of the incidents are explosions, fires, and atmospheric release of toxic chemicals. The most severe case was a thermal explosion from an organic peroxide storage area which caused the death of 33 persons. Popping and direct releasing of process chemicals to the atmosphere from relieving devices cause the greatest environmental concerns to the community close to the plants. Runaway reactions in batch type reactors occur frequently due to various operational mistakes. Heat of reaction is the most frequent ignition source of runaway reactions and emergency relief.
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    RMP hazard assessment for compliance with EPA's risk management program regulation: OxyChem's experience (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 272-277 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: EPA's Risk Management Program regulation, promulgated in June 1996 as 40 CFR Part 68 requires subject industries to submit Risk Management Plans by June 1999. This plan requires hazard assessment of the operations of a facility using worst case scenarios and alternative releases. EPA has provided an Off-site Consequence Analysis (OCA) guidance to help facilities in their hazard assessment.OxyChem will be significantly impacted by the RMP rule. This paper outlines OxyChem's general experience and its strategy in planning to comply with this rule. OxyChem's approach in the development of the scenarios required by the rule is described in this paper. Limitations involved in the use of EPA's look-up tables or a single modeling solution for conducting all of the OCA are discussed. A three tiered OCA approach is presented as a possible alternative.
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    Suppression of class a fires with HFC-227ea (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 209-212 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: HFC-227ea (CF3CHFCF3;1, 1, 1, 2, 3, 3, 3-heptafluoropropane) is an effective replacement for Halon 1301 in fire suppression systems, providing rapid extinguishment of flames through a combination of physical and chemical mechanisms. The vast majority of applications for HFC-227ea involve the protection of Class A hazards, which are characterized by low fuel loadings and low energy output, with fire sizes often in the range of 5-10 kW. Mid- and large-scale testing has demonstrated that HFC-227ea, at its minimum design concentration of 7.0% v/v, is effective at extinguishing fires typical of those expected to occur in electronic data processing (EDP) facilities, telecommunication facilities and anechoic chambers. The levels of HF produced following extinguishment of typical Class a fires with HFC-227ea were well below the estimated mammalian LC50 and the human Dangerous Toxic Load (DTL), and do not appear to present a threat to electronic equipment.
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    A thematic approach to system safety (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 219-224 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Sandia National Laboratories (Sandia) has refined a process for developing inherently safer system designs based on methods used by Sandia to design detonation safety into nuclear weapons. The process was created when Sandia realized that standard engineering practices did not provide the level of safety assurance necessary for nuclear weapon operations, with their potential for catastrophic accidents. A systematic approach, which relies on mutually supportive design principles integrated through fundamental physical principles, was developed to ensure a predictably safe system response under a variety of operational and accident-based stesses. Robust, safe system designs result from this thematic approach to safety, minimizing the number of safety critical features. This safety assurance process has two profound benefits: the process avoids the need to understand or limit the ultimate intensity of off-normal environments and it avoids the requirement to analyze and test a large array of accident environment scenarios (e.g., directional threats, sequencing of environments, time races, etc) to demonstrate conformance to all safety requirements.
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    Masthead (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998) 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    The assignment of safety systems addressing workplace hazards (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 233-237 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new method is described to enhance the management of process safety risks such that the number and type of safety systems protecting against any hazard are consistently predicated upon risk. Further, that such an assignment of safety systems can be made consistent throughout an organization. This consistency is gained through standardization of qualitative risk ranking and by setting company guidelines.
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    Reactivity and ignition characteristics of silane/air mixtures (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 243-258 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Research was carried out to develop improved protection guidelines for silane handling systems through enhanced understanding of the behavior of releases of this pyrophoric gas. The approach involved addressing three aspects of the problem: the prompt ignition behavior of silane; the reactivity characteristics of quiescent silane/air mixtures; and the rates of reaction of silane leaked into enclosures with and without explosion venting, in the presence of ventilation air flow. A first conclusion, reached from tests in a ventilated cabinet, was that, contrary to prevailing belief, the ventilation flow has no measurable effect on the prompt ignition of the release. From experiments in a 5.1-liter (311-in.3) sphere it was found that silane/air mixtures of concentrations between 1.4 and 4.1% (by volume) are explosive but stable. In this case, piloted ignition tests yielded laminar burning velocities up to 5 m/s (1000 ft/min). Mixtures between 4.5 and 38% (the maximum reached in the tests) were found to be metastable, and would undergo spontaneous ignition after a delay ranging from 15 to 120 seconds, with the shorter values corresponding to higher silane concentrations. Experiments were also performed in a 0.645-m3 (22.8-ft3) vessel both with and without explosion venting, to measure the rates of energy release associated with impulsively-started silane leaks from 1/8 and 1/4-in. (3.2 and 6.4-mm) lines. A method for the prediction of the venting requirements of partial-volume deflagrations (PVD) was evolved into a tool to quantify the pressure rise from ignition of silane leaks in enclosures. These results represent a significant step toward updating existing design recommendations which prescribe ventilation requirements that are based on outdated and, in some instances, misinterpreted data.
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    Properties of simulated gas explosions of interest to the structural design process (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 278-287 
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    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Gas explosion simulators are often used as tools in process plant design. This article presents some properties of gas explosions found using the EXSIM simulation software on three offshore modules with a total of nearly 10,000 simulations. The selected results are chosen for their supposed applicability to structural design in the process industries.Generalized data are presented for the effect of gas cloud size, explosion impulse vs. explosion pressure, pressure and impulse vs. duration, the probability of a “short” explosion, loading rate, pressure-time “shape” function, and the effect of introducing louvers.
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    URL: http://dx.doi.org/10.1002/prs.680170409
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    Glucoamylase production in continuous cultures of Aspergillus niger with special emphasis on growth parameters (1997)
    Springer
    World journal of microbiology and biotechnology 14 (1997), S. 113-118 
    Details
    ISSN: 1573-0972
    Keywords: Aspergillus ; continuous culture ; glucoamylase ; growth ; fungi ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Maltose-limited continuous culture of Aspergillus niger was carried out with potassium nitrate to investigate growth and glucoamylase formation characteristics. Glucoamylase production was dependent on the specific growth rate. The maximal amount of glucoamylase (units/l and U/g dry weight) was obtained at μ=0.08h−1, and the maximum specific rate of production (units/g/dry weight per hour) was at μ=0.2h−1. The maintenance coefficients (ms and mATP) were higher than for some other fungi. Maximal growth yields on substrate, oxygen and ATP (Yxsm, YxO2m and Yxam) were very efficient (high) and the value of Yxam, which cannot exceed the theoretical maximal value, is obtained when a P/O ratio of 1:1 is assumed. This indicates that biomass formation is energetically inexpensive and most of the expended energy has to be invested in the process of glucoamylase excretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008840904246
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    Simulations of a LDPE reactor using computational fluid dynamics (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 104-117 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Computational fluid dynamics methods are used to provide three-dimensional simulations of a low-density polyethylene (LDPE) autoclave reactor under normal operating conditions. For the conditions used, the reactor is not very well mixed; thus, the common model approximation of a perfectly stirred reactor is not warranted. The simulations verify the sensitive nature of the polymerization reactors and indicate a need for optimizing operating parameters.
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    Simulation of decoking of thermal cracking coils by steam/air-mixtures (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 118-126 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A rigorous approach was developed for the simulation of the decoking of an industrial cracking furnace. A one-dimensional heterogeneous reactor model, which accounts for the interfacial gradients between the process gas and the coke surface, was used to simulate reactor coils. Both the combustion and steam gasification of the coke layer were taken into account. The reactor model for the decoking was coupled with a detailed firebox simulation model. The initial profile of the coke layer thickness, required for the decoking calculations, was obtained by a run-length simulation. The evolution with time of the temperature distribution inside the cracking coil and in the furnace was generated simultaneously, which made it possible to understand the decoking operation in detail and to predict its duration accurately.
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    Dynamics of semibatch polymerization reactors: II. Pilot-plant study (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 157-165 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A semibatch flow scheduling strategy proposed by Teymour and Ray (1989, 1996) is evaluated for a polymerization reaction conducted in a pilot-plant reactor. The reaction used is the free radical terpolymerization of styrene, α-methyl styrene, and acrylic acid monomers initiated by an organic peroxide initiator and carried out in the presence of a reactive glycol ether solvent. This strategy was tested in both single batch and sequential semibatch modes. The process was shown to produce polymer of constant molecular weight properties and composition as inferred from acid number and monomer conversion measurements. This process could be used for obtaining polymer products from a semibatch reactor that are of comparable quality to CSTR products. Results indicate success of this process at meeting this objective; however, practical considerations relating to agitation and temperature control need to be properly addressed to ensure this success.
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    Steady-state multiplicity in cocurrently cooled autothermal reactors (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 127-134 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The steady-state simulation of a cocurrently cooled autothermal fixed-bed reactor was carried out using a 2-D heterogeneous mathematical model. The ammonia synthesis was chosen as a case study. Unlike the not-autothermal cocurrent reactor, which is unconditionally stable, the autothermal cocurrent reactor shows multiple steady states within a broad range of operating conditions. This finding, not reported in the literature, is explained through the mass transport from the bottom to the top of the reactor, associated with a feedback of energy. The feedback of heat, which is inherent to autothermal reactors, leads to an ignition-extinction phenomenon similar to that found in the countercurrent configuration. The influence of different parameters on the stability of the autothermal cocurrent reactor was analyzed. The regions where steady-state multiplicity occurs were compared with those presented by the autothermal countercurrent reactor. The influence of an additional heat exchanger on the reactor stability was considered.
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    Analysis of νi/κTx in solvent mixtures at the critical line (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 277-280 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430133
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    Rheological simulation of in-line bubble interactions (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 265-267 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430130
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    Analysis of nucleation and crystal growth data using the interfacial supersaturation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 268-272 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430131
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    Boiling heat transfer of Nitrogen in a thermosyphon condenser-reboiler (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 339-344 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental investigation was conducted to determine the boiling heat-transfer characteristics in a thermosyphon condenser-reboiler of air-separation plants. The test section was a plate-fin heat exchanger of practical size of 0.106 m width and 2.56 m length. The testing fluid was nitrogen. Experiments were carried out within a range of pressure from 150 to 300 kPa, submergence from 1.95 to 2.80 m, and heat flux up to 11 kW/m2 under constant wall-temperature condition. The liquid superheat at the onset of boiling was rather significant. The boiling heat-transfer coefficients obtained agreed well with Chen's correlation modified by Colburn's J factor within a mean deviation of 9.3%.
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    Masthead (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997) 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430101
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    Efficient sampling technique for optimization under uncertainty (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 440-447 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The concept of robust design involves identification of design settings that make the product performance less sensitive to the effects of seasonal and environmental variations. This concept is discussed in this article in the context of batch distillation column design with feed stock variations, and internal and external uncertainties. Stochastic optimization methods provide a general approach to robust/parameter design as compared to conventional techniques. However, the computational burden of these approaches can be extreme and depends on the sample size used for characterizing the parametric variations and uncertainties. A novel sampling technique is presented that generates and inverts the Hammersley points (an optimal design for placing n points uniformly on a k-dimensional cube) to provide a representative sample for multivariate probability distributions. The example of robust batch-distillation column design illustrates that the new sampling technique offers significant computational savings and better accuracy.
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    URL: http://dx.doi.org/10.1002/aic.690430217
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    Analysis of cake growth in cake filtration: Effect of fine particle retention (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 33-44 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Equations were derived that describe the dynamics of cake growth in cake filtration, and methods for their solutions were developed. In deriving the equations, the moving boundary nature of the cake formation process and the effect of fine particle retention were considered. It was shown that fine particle retention may contribute significantly to the decrease of cake permeability and thus alters the performance of cake filtration even if the amount of fine particles involved is small. Through numerical examples, it was also demonstrated that fine particle retention in filter cakes may cause serious errors in determining the constitutive relationships from filter test data.
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    Characteristics of high-pressure liquid-solid fluidization (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 45-57 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fundamental characteristics of liquid-solid fluidization at high pressures (up to 21 MPa) and moderate temperatures (up to 89°C) are investigated. Properties under study include minimum fluidization velocity (umf), bed voidage at minimum fluidization, and bed expansion. Devices for in-situ measurements of physical properties of the liquid in the bed are developed, and measurements are carried out to quantify the pressure and temperature effects on the fluidization behavior. The results indicate that under high pressures and moderate temperatures, liquid-solid fluidization behavior is affected significantly by the variation of liquid density and viscosity with pressure. As the pressure increases, the liquid viscosity and density increase, yielding an increased drag force and buoyancy force on the particles, and hence a decreasing umf and an increasing bed expansion for a given liquid flow rate. An increase in temperature has an opposite effect on the physical properties of the liquid, increasing umf and decreasing the bed expansion for a given liquid flow rate. Various correlations proposed in the literature for umf and bed expansion, including those by Richardson and Zaki (1954) and Chitester et al. (1984), are applicable to high-pressure and high-temperature conditions when proper account is made of the liquid physical properties under bed operating conditions.
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    URL: http://dx.doi.org/10.1002/aic.690430107
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    Asymptotic models for H2S absorption into single and blended aqueous amines (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 58-63 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Asymptotic power series solutions for the mass-transfer enhancement factor for absorption of a gas component into a liquid where it undergoes irreversible instantaneous chemical reaction(s) with one and two liquid-phase reactants are developed in this work. The Padé technique is used to extend the region of applicability (accelerate the convergence) of the four-term asymptotic power series solutions. The resulting modified asymptotic expressions for the enhancement factor show excellent accuracy over a wide range and can be used to predict enhancement factors as low as 2 with an error of about 5% compared to the exact numerical solution. Predictions of these new asymptotic solutions are compared with experimental absorption data for H2S absorption into aqueous methyldiethanolamine and H2S absorption into aqueous mixtures of methyldiethanolamine and diethanolamine obtained in a laminar-jet absorber. The absolute mean deviations of the predictions from the experimental absorption data for the single and mixed amine solutions were 4.6% and 2.4%, respectively.
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    Analysis of rate enhancement in a periodically operated trickle-bed reactor (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 166-172 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When a trickle-bed reactor (TBR) is operated periodically, the bed is fed with liquid on and off, while the gas phase passes continuously. Rates and conversions could be higher than those corresponding to the steady-state operation. In the “dry cycles” the heat generated by the reaction can drive the vaporization of the liquid phase, and a much more rapid “gas phase” reaction may occur. There is a trade-off between the potential for hot-spot formation and the fact that overall rates are higher during cycling. A qualitative understanding of the phase transition in TBRs is obtained by a simple phenomenological model that takes into account different transport and reaction mechanisms occurring in a catalytic particle under different cycling conditions. A mathematical model is used to predict results.
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    Recent advances in modeling thermodynamic properties of aqueous strong electrolyte systems (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 180-195 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Theoretical and engineering models for the thermodynamic properties of strong electrolyte solutions have advanced significantly since 1985. This progress is notable in the ability to calculate selected properties of single and mixed strong electrolyte solutions over a wide range of temperatures and compositions, including effects of various nonelectrolytes, solvents and supercritical components. Theoretical studies have begun to consider more realistic fundamental interactions between various components in these systems. There have been several successful conversions of theories based on the mean spherical approximation and perturbation methods into engineering equations, without large numbers of empirical parameters. Other theoretical models seem almost ready for application to real systems. The capability to estimate a wide variety of thermodynamic properties accurately with a consistent set of equations and a small number of adjustable parameters has been achieved by several groups over limited temperature and composition ranges. Much work remains to be done, however, to understand completely the interplay and relative importance of various contributing energy effects.
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    Vapor-liquid equilibria of the ternary mixture CH4 + C2H6 + CO2 from molecular simulation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 212-217 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The NpT + test-particle method for the calculation of vapor-liquid equilibria by molecular simulations is extended to ternary mixtures. It is applied to the system methane + ethane + carbon dioxide, for which all binary molecular interaction models are available from previous work. Methane is described as one-center Lennard-Jones fluid, ethane as two-center Lennard-Jones fluid, and carbon dioxide as two-center Lennard-Jones plus point quadrupole fluid. The unlike interactions are treated in the same way as the binary mixtures, using two parameters for each binary interaction. No ternary parameters are introduced. Vapor-liquid phase equilibria are calculated for the ternary mixture at the following temperature-pressure pairs: 233.15 K - 2 MPa; 250.5 K - 2 MPa; and 250.5 K - 3.04 MPa. Comparison of the simulation data with experimental and equation-of-state results shows excellent agreement. Bubble and dew densities are also reported.
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    Recovery and purification of paclitaxel using low-pressure liquid chromatography (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 232-242 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An efficient and economical low-pressure liquid chromatography process has been developed for paclitaxel recovery and purification directly from plant-tissue culture (PTC) broth. PTC broth is first diluted with ethanol to ensure padlitaxel dissolution and then passed through a column packed with a high-capacity polystyrene divinyl-benzene sorbent. A step increase in ethanol concentration in the mobile phase (ethanol:water) is used to concentrate and compress the taxane bands to as high as 29-fold of influent concentrations (about 1 mg/L). A recycle technique is then used to separate the concentrated paclitaxel band from other taxane bands, achieving 95% purity with more than 90% recovery and 99% purity with more than 80% recovery. In this process, the same low-pressure columns are used to capture, concentrate and purify paclitaxel. Theoretical predictions agree closely with the stepwise elution and recycle chromatography data. After validation, simulations are used to explore various design and operating alternatives. Analysis of the alternatives shows that the process cost can be further reduced by using higher feed concentration, larger loading volume, smaller particle size, and optimal gradient and recycle strategies.
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    Phase equilibria for the mean-force potential of globular protein solutions (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 218-231 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When polymers are added to a solution containing proteins, the protein may deposit as an amorphous precipitate or as crystals. Experimental evidence indicates that from a thermodynamic viewpoint, an amorphous precipitate should be treated as a liquid phase dense in the protein and crystals as true solids. To understand the conditions under which protein precipitation or crystallization may occur, Gibbs-ensemble Monte Carlo simulation and Gibbs-Duhem integration techniques are used to calculate the liquid-liquid and liquid-solid phase boundaries for protein precipitation induced by polymers. In these simulations, the system is modeled using the pseudo-one-component approximation with an appropriate potential of mean force. The critical point for fluid-fluid phase equilibrium disappears as the attractive part of the mean-force potential becomes very short ranged. The accuracy of the second-order Barker and Henderson perturbation theory is examined by comparing the phase diagram predicted using this method with the simulation results. Perturbation theory is able to predict the general trends observed in the simulations but not with quantitative accuracy. Perturbation theory is then used to examine a broader range of conditions for protein deposition.
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    Influence of particle-size distribution on entrainment solid rate in fluidized bed (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 260-262 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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    Simulated moving bed under linear conditions: Experimental vs. calculated results (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 935-945 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simulated moving bed (SMB) was operated for the separation of mixtures of 2-phenyl ethanol and 3-phenyl-1-propanol on columns packed with Zorbax C18 bonded silica, using a 60:40 (v/v) solution of methanol and water as the mobile phase. Series of four or eight columns were used. The experiments were carried out with low concentration mixtures, that is, under linear conditions. Band profiles of both compounds eluted from one of the columns during successive periods after steady state had been reached were recorded, as were the concentration histories at the extract and raffinate ports. These experimental results are compared to those predicted by two models: the linear ideal and the linear equilibrium-dispersive models of chromatography, applied to the SMB separator. These two models give excellent agreement between the experimental profiles and those calculated with the model. As expected, the profiles predicted by the ideal and the equilibrium-dispersive models differ only by the lack of dispersion in the profiles given by the former. The latter model is demonstrated to be a solid, reliable tool for further studies of the SMB design and optimization.
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    Gas holdup in slurry bubble columns: Effect of column diameter and slurry concentrations (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 311-316 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To study the influence of particle concentration on the hydrodynamics of bubble-column slurry reactors operating in the heterogeneous flow regime, experiments were carried out in 0.10, 0.19, and 0.38-m-dia. columns using paraffinic oil as the liquid phase and slurry concentrations of up to 36 vol. %. To interpret experimental results a generalization of the “two-phase” model for gas-solid fluid beds was used to describe bubble hydrodynamics. The two phase identified are: a dilute phase consisting of fast-rising large bubbles that traverse the column virtually in plug flow and a dense phase that is identified with the liquid phase along with solid particles and entrained small bubbles. The dense phase suffers backmixing considerably. Dynamic gas disengagement was experimented in the heterogeneous flow regime to determine the gas voidage in dilute and dense phases. Experimental data show that increasing the solid concentration decreases the total gas holdup significantly, but the influence on the dilute-phase gas holdup is small. The dense-phase gas voidage significantly decreases gas holdup due to enhanced coalescene of small bubbles resulting from introduction of particles. The dense-phase gas voidage is practically independent of the column diameter. The dilute-phase gas holdup, on the other hand, decreases with increasing column diameter, and this dependence could be described adequately with a slight modification of the correlation of Krishna and Ellenberger developed for gas-liquid systems.
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    Intraparticle diffusion in hydrogenation of 3-hydroxypropanal (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 475-485 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Strong intraparticle diffusion resistance was observed and the apparent effectiveness factors were measured for the hydrogenation of 3-hydroxypropanal (HPA) to 1,3-propanediol (PD) over Ni/SiO2/Al2O3 catalyst pellets at 45 to 80°C and 2.60 to 5.15 MPa in a stirred reactor with a spinning basket. A mathematical model was proposed to describe the intraparticle diffusion and to estimate the effective diffusion coefficients of HPA, PD and hydrogen under reaction conditions by a maximum likelihood function of the apparent effectiveness factors of HPA and PD. The calculated concentration distributions of HPA, PD and hydrogen in catalyst particles reveal an excess of hydrogen at 80°C and higher temperatures, but an excess of HPA at 45°C. It results in a weak dependence of the consumption formation rate of HPA and PD on the partial pressure of hydrogen at high temperature.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430220
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    Perturbation solution to the convection-diffusion equation with moving fronts (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 631-644 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Electrophoresis of a solute through a column in which its transport is governed by the convection - diffusion equation is described. Approximate solutions to the convection - diffusion equation in the limit of small diffusion are developed using perturbation methods. The diffusion coefficient and velocity are assumed to be functions of space and time such that both undergo a sudden change from one constant value to another within a thin transition zone that itself translates with a constant velocity. Two cases are considered: (1) the thickness ∊f of the transition zone is negligible compared to the diffusional length scale, so the zone may be treated as a singular boundary across which the diffusion constant and velocity suffer discontinuous changes; (2) the transition zone is considerably wider than the diffusional length scale, so the diffusion coefficient and velocity, although sharply varying, are smooth functions of position and time. A systematic perturbation expansion of the concentration distribution is presented for case 1 in terms of the small parameter ∊ = 1/Pe. A lowest order approximation is given for case 2. A suitably configured system analyzed here can lead to progressive accumulation, or focusing, of the transported solute. The degree of focusing in case 1 scales with ∊-1, whereas in case 2 it scales with (∊f∊)-1/2, and thus increases much more weakly with increasing Pe. A separation based on this concept requires development of materials and devices that allow dynamic tuning of the mass-transport properties of a medium. This would make it possible to achieve progressive focusing and separation of solutes, such as proteins and DNA fragments, in electrophoretic media with an unprecedented degree of control.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430309
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    Continuous drying of a solid wetted with ternary mixtures (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 681-692 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence on drying selectivity of the continuous-contact mode between a solid wetted with ternary mixtures and a gas stream was theoretically studied. The liquid mixtures, ethanol-isopropanol-water and water-ethanol-acetone, were used. A mathematical model describing a gas-phase-controlled process was developed, and the influence of the process variables was studied by simulations. In addition to the inlet composition of the moisture and temperature of the solid, gas composition has the most important effect on selectivity. Small changes of gas composition, either imposed or spontaneous, may modify completely the process trajectory. The extent of these effects depends on the ratio between the flow rates of inlet gas and liquid contained in the solid. Because of their effects on the evolution of temperature and composition, the operating pressure and energy sources other than convection are also useful in controlling the selectivity. Since all these variables determine the composition of the remaining liquid and thereby product quality, their influence should be predictable. The model may be a valuable tool for exploring the process, provided that drying is gas-phase-controlled.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430314
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    Sherwood number for a swarm of adsorbing spheroidal particles at any peclet number (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 844-846 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430330
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    Finite-element simulation of mixing: 1. Two-dimensional flow in periodic geometry (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 577-587 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Complex mixing flows and mixing parameters are calculated to evaluate mixing quality on the basis of kinematic parameters together with a statistical analysis. The results allow for a comparative evaluation in terms of geometry and flow parameters. The evaluation is limited to two-dimensional flows with moving boundaries in periodic motion such as the flow in the cross section of a twin-cam mixer. The finite-element calculation requires a remeshing procedure for every time step with special techniques to upgrade mixing variables from one time step to the next. The relative mixing quality of single cam and co: or counterrotating cam devices are compared by evaluating segregation scale, length stretch, and efficiency. The numerical results exhibit a good correspondence with their experimental counterpart.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430303
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    Resonant microwave power absorption in slabs and cylinders (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 615-624 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Resonant power absorption is an important phenomenon during microwave heating. The resonances that occur when plane electromagnetic waves are incident on infinitely long cylinders and slabs are investigated as a function of sample dimensions. For cylinders two kinds of incident waves are studied: TMz when the electric field is oriented along the axis of the cylinder and TEz when the magnetic field is oriented along the axis. At a resonant condition the overage power absorbed by the sample is a local maximum. Due to attenuation within the sample the resonances decrease in intensity as the sample size increases. Using the dielectric properties of water, resonances are found to be a function of the ratio of the sample dimension to the wavelength of radiation, λs, in the sample. For slabs of thickness L and integer values of n, resonances occurred at L/λs = 0.5n; for cylinders of diameter D, resonances occurred at D/λs = 0.5n - 0.257. The generality of these relations to predict resonances in other food samples are shown using existing dielectric data. Resonances in cylinders for both polarizations occurred at similar radii. However, the radius at which the first resonance occurred for the TMz case was absent in the TEz case.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430307
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    Transient behavior of pulsed particulate fluidized beds (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 625-630 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient phenomena in solid-liquid fluidized-bed systems are important in designing pulsed, countercurrent (multistage) fluidized-bed contactors of the Cloete-Streat type at high-solids flow rate. Of particular interest are the residence times or corresponding velocities of porosity gradients in the bed and the excess or overshoot height of the bed after refluidization. Theory assuming local equilibrium between holdup and velocity of the phases (local-equilibrium model) for stepwise perturbations in the liquid flow is readily available. It is investigated whether the local-equilibrium theory can be used for more complex perturbations and whether inertia effects, such as are encountered in countercurrent multistage fluidized-bed systems, can be ignored. Therefore, the detailed particle-bed model of Foscolo and Gibilaro, which incorporates inertia effects, was applied to investigate the transient behavior of fluidized-bed systems. Transient fluidization experiments were performed with a broad range of water-fluidized particles in a laboratory-scale multistage fluidized-bed contactor. The operating conditions corresponded to those for countercurrent contact.Numerical simulations with the particle-bed model predict satisfactory experimental results. The “overshoot” heights of the fluidized bed were estimated correctly by the particle-bed model, whereas the local-equilibrium model only provides a conservative estimate. However, the local-equilibrium model allows an analytical solution that is more interesting for design, as it avoids tedious calculations. The residence time of the last perturbation before the fluidized bed relaxes to steady state was estimated with similar accuracy by both models.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430308
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    Steady spontaneous capillary flow in partially coated tubes (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 645-654 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A spontaneous, steady capillary flow is produced for a liquid index in a circular tube that is partially coated with a surface modifier to create a discontinuous wetting condition between upstream and downstream portions of the tube. As a means of demonstrating that the flow configuration may prove useful as a diagnostic tool in studies concerning capillarity and the physics associated with the moving contact line, average steady velocities are predicted and compared against a large experimental data set that includes the effects of tube dimensions and fluid properties. To access a wider range of tube diameters (0.516-9.88 mm), experiments are performed employing “U-tubes” tested in the low-gravity environment of a drop tower, in addition to straight capillary tubes tested horizontally in a laboratory. The sensitivity of the steady capillary flow to surface cleanliness is dramatic.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430310
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    Permeability of filter cakes of palm oil in relation to mechanical expression (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 673-680 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Permeability and compressibility data are required for an adequate process model for compressible-cake filtration and mechanical expression. Experimental and modeling results of the permeability of palm-oil filter cakes (a highly compressible viscoelastic material) are combined with compressibility data, leading to a model for the expression step. Permeability measurements show that permeability depends strongly on the quantity of fine particles in the cake. Removal of fine particles from the slurry before expression significantly increases the solid-phase content during expression due to higher permeability. Modeling results of the expression step show that for palm-oil filter cakes there is a pressure above which the attainable mass fraction of solids becomes independent of pressure. Decrease in specific cake resistance has two effects: a higher mass fraction of solids at the same pressure and a higher pressure at which the mass fraction of solids is not affected further.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430313
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    Modeling and optimization of a semiregenerative catalytic naphtha reformer (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 740-753 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Modeling and optimization of a semiregenerative catalytic naphtha reformer has been carried out considering most of its key constituent units. A detailed kinetic scheme involving 35 pseudocomponents connected by a network of 36 reactions in the C5-C10 range was modeled using Hougen-Watson Langmuir-Hinshelwood-type reaction-rate expressions. Deactivation of the catalyst was modeled by including the corresponding equations for coking kinetics. The overall kinetic model was parameterized by bench-marking against industrial plant data using a feed-characterization procedure developed to infer the composition of the chemical species in the feed and reformate from their measured ASTM distillation data. For the initial optimization studies, a constant reactor inlet temperature configuration that would lead to optimum operation over the entire catalyst life cycle was identified. The analysis was extended to study the time-optimal control profiles of decision variables over the run length. In addition, the constant octane case was also studied. The improvement in the objective function achieved in each case was determined. Finally, the sensitivity of the optimal results to uncertainty in reactor-model parameters was evaluated.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430319
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    Microwave heating of the continuous flow catalytic reactor in a nonuniform electric field (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 754-760 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Temperature profiles in the continuous-flow reactor with a fixed bed placed in a nonuniform microwave field are predicted by considering specific on - off regulation of the microwave power and local distribution of the electric-field intensity. The spatial and temperature dependence of the electric-field intensity affects the heating appreciably, as shown by indirect measurements. Results of numerical calculations agree with experimental data of outlet temperature and explain temperature oscillations in the outlet flow. The model developed allows an accurate description of microwave heating in the continuous-flow reactor associated with specific regulation of microwave power. The hydrolysis of sucrose catalyzed by the strongly acidic cation-exchange resin Amberlite 200C in R-H form was chosen as the reaction system. Calculated conversions of sucrose based on predicted temperature profiles agree with experimental data.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430320
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    Oxidative dehydrogenation of butane using membrane reactors (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 777-784 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxidative dehydrogenation of butane was studied at temperatures between 450 and 550°C using a conventional fixed-bed reactor and inert membrane catalytic reactors with different feed arrangements. When inert membrane reactors were employed, a ceramic membrane was used to distribute oxygen to a fixed bed of V-Mg-O catalyst. The membrane reactor was found to be more efficient than a fixed-bed reactor under most of the conditions investigated. In addition, in the membrane reactor the formation of hot spots decreased considerably, leading to a more stable and safer operation.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430322
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    Reaction rates in fractal vs. uniform catalysts with linear and nonlinear kinetics (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1691-1699 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pore fractal objects are expected to be optimal catalysts, since material is supplied to the narrower pores, which are also shorter through the larger pores where diffusion resistance is smaller. To demonstrate this, diffusion and reaction were simulated on Sierpinski-gasket-type fractal objects and on the corresponding nonfractal uniform-pore structures of the same size, porosity and reactive area. Positive order reactions limited by Knudsen diffusion were shown to exhibit larger rates in fractal than in uniform-pore objects. Fractal catalysts also exhibited a new intermediate domain in which the rate depends only weakly on the kinetics parameters. In nonmonotomic kinetics the branching point (bifurcation point) was extremely sensitive to the pore structure.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430706
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    Electrochemically modulated complexation process for ethylene/ethane separation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1709-1716 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An electrochemically modulated complexation (EMC) process was designed to selectively extract and concentrate ethylene from a feed-phase mixture with ethane. Unlike previous EMC processes, where the separation was based on equilibrium solubility differences, this separation was based on differences in the rate of complexing with copper(I) solution between the two gases. The EMC process employed flowthrough electrolysis cells that electrochemically modulate aqueous-phase copper chlorides between high, copper(I), and low, copper(II), affinity states. The liquid phase in the high affinity form contracts a feed gas phase in a hollow-fiber membrane module for selective extraction and contacts the receiving gas phase in the low affinity form for concentration. Experimental results and modeling of the process are reported.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430708
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    Synthesis of crystallization-distillation hybrid separation processes (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1751-1762 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A systematic method to synthesize crystallization-distillation hybrid separation processes is presented. Two classes of hybrids are identified for binary mixtures. The first bypasses azeotropes and tangent pinches, while the second bypasses eutectics. Guidelines for flow-sheet selection are proposed based on an analysis of simple eutectic, constant relative volatility systems. In addition, the hybrids are compared to both extractive and adductive crystallization in order to determine the conditions under which solvent-based crystallization techniques outperform the proposed hybrid configurations. The method is extended to ternary mixture. The use of stream combination and complex distillation columns is also considered.
    Additional Material: 20 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430712
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