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  • Articles  (2,924)
  • Wiley  (2,924)
  • 2010-2014  (2,924)
  • 1945-1949
  • Chemical Engineering and Technology  (1,272)
  • 4519
  • 1
    Publication Date: 2013-09-07
    Description: The generation of gaseous singlet oxygen by gas-liquid reaction of chlorine with alkaline solution of hydrogen peroxide in spray form was studied experimentally on the originally designed device with a fast separation of reacted liquid from gas. The singlet oxygen yield, residual chlorine, and water vapor content in gas were measured under different experimental conditions of the centrifugal spray singlet oxygen generator (CSSOG) using nitrogen as a dilution gas. A characteristic feature of the CSSOG is a high utilization of the chemicals and production of singlet oxygen at a very high total pressure even near the atmospheric pressure. This generator developed originally for driving a chemical oxygen-iodine laser (COIL) could be employed also as an efficient singlet oxygen source in material science, chemical synthesis, and others. A centrifugal spray generator of singlet oxygen was optimized for operation with nitrogen buffer gas and high total pressure. This generator is able to successfully operate at much higher pressure compared to other types. Due to the very high hydrogen peroxide utilization the consumption of input liquid chemicals is substantially reduced.
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  • 2
    Publication Date: 2013-09-11
    Description: Ionic liquids (ILs) are recyclable acid catalysts for transesterification reactions. In the present study, different acidic ILs were examined in this reaction, with special focus on their recyclability. Furthermore, the IL-catalyzed transesterification reaction was realized in continuous operation. A miniplant reactor with technically representative design and operating characteristics was used for this study. The applied rig has a volume of 5 L and an external thermosyphon reboiler. The miniplant reactor can be operated in batch and in continuous mode. ILs functionalized with a sulfonic acid group were found to be the most suitable IL catalysts for the transesterification reactions under investigation. Using these ILs, reaction rates as high as for H 2 SO 4 could be realized. Moreover, the IL catalyst was demonstrated to be active for at least 1000 h of operation time. Ionic liquids are suitable catalysts for acid-catalyzed transesterifications. Acidic ionic liquids were used as recyclable and durable catalysts for this reaction. The performances of the benchmark catalysts were obtained for at least 1000 h of operation in a miniplant reactor, which is representative of industrial processes.
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  • 3
    Publication Date: 2013-09-25
    Description: A mathematical model based on 34 days continuous operation of an industrial isomerization unit was developed. The unit involves a radial-flow reactor with a catalyst capable of converting xylenes and ethylbenzene to mixed xylenes. The catalyst contains EU-1 zeolite, platinum, and alumina as binder. Two reactions are considered, i.e., ethylbenzene isomerization and xylene isomerization. The rates are based on the Hougen-Watson model according to the literature. An optimization procedure based on the trust-region-reflective algorithm was carried out in order to obtain new kinetic constants that minimize the difference between the actual and the calculated values. The standard error of the parameters estimated was calculated through the deleted-one Jackknife method. A simplified mathematical model for simulating the reactor operation of an industrial isomerization unit was developed. A relatively new type of catalyst allowed milder conditions to reduce side reactions. The kinetic constants were obtained through an optimization procedure. The model may be applied to simulate larger systems due to its simplicity.
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  • 4
    Publication Date: 2013-09-25
    Description: An industrial-scale reactor for ethylene production was modeled using the oxidative dehydrogenation of ethane (ODHE) in a multi-tubular reactor system, examining a variety of parameters affecting reactor performance. The model showed that a double-bed multi-tubular reactor with intermediate air injection scheme was superior to a single-bed design, due to the increased ethylene selectivity while operating under lower oxygen partial pressures. The optimized reactor length for 100 % oxygen conversion was theoretically determined for both reactor designs. The use of a distributed oxygen feed with a limited number of injection points indicated a significant improvement on the reactor performance in terms of ethane conversion and ethylene selectivity. This concept also overcame the reactor runaway temperature problem and enabled operations over a wider range of conditions to obtain enhanced ethylene production. High demands for ethylene call for more efficient reactor designs. This model for the oxidative dehydrogenation of ethane for a Ni-Nb-O mixed-oxide catalyst showed that a double-bed multi-tubular reactor with air injection is superior to a single-bed design, due to an increased ethylene selectivity while operating under lower oxygen partial pressures.
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  • 5
    Publication Date: 2013-09-25
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  • 6
    Publication Date: 2013-09-25
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  • 7
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    Wiley
    Publication Date: 2013-09-25
    Description: Pilot Setup for Dynamically Enhanced Membrane Emulsification This setup allows the production of emulsions with narrow drop size distributions. A disperse liquid phase is pushed through a porous membrane into another immiscible fluid phase. A rotor above the membrane induces laminar shear flow, which detaches the drops from the membrane pores. A narrow shear gap and micro engineered membranes help to maintain good control over drop detachment. The sub pictures show drops detaching from membrane pores (top) at different shear flow conditions acquired in a separate visualization setup. The bottom picture shows a cut through a micro engineered silicon membrane, which was specifically designed and fabricated at ETH Zurich for the emulsification setup. The apparatus was designed and built by the Bühler AG, Uzwil, Switzerland in close collaboration with the ETH Zurich, Switzerland. DOI: 10.1002/ceat.201300256 Drop Detachment from a Micro-Engineered Membrane Surface in a Dynamic Membrane Emulsification Process S. Holzapfel*, E. Rondeau, P. Mühlich, E. J. Windhab* Chem. Eng. Technol. 2013 , 36 (10) , 1785–1794
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  • 8
    Publication Date: 2013-06-07
    Description: Typically, the product fineness in a dispersion process is determined by the strength of the agglomerates and aggregates, the properties of the homogeneous phase and its interaction with the surface of the disperse phase, the stress mechanism itself as well as its intensity and frequency acting on the particles. The objective of this study is to characterize the efficiency of a dispersion process in terms of stress frequency and intensity using a newly developed dispersing machine called dispermeter. This dispersing machine is capable of processing suspensions with a broad range of viscosities. Furthermore, due to highly defined geometries, the rheological behavior of suspensions as an important parameter for processability and suspension stability can be characterized during the dispersion process. By utilizing the rheological properties the dispermeter can be used for the selection of an applicable electrostatic or steric stabilizer for an optimal dispersion process. With the dispermeter two different types of pyrogenic metallic oxide particles, nanosized alumina and silica, are processed. The progress in deagglomeration is monitored by particle size analysis and compared with that in a dissolver. A theoretical process model is used to characterize both processes. Moreover, this model is used to predict the dispersion results obtained in the dissolver. To characterize the rheological properties and dispersion stability as well as the efficiency of a dispersion process in terms of stress frequency and intensity, a new dis-persing machine was developed. A theoretical process model was used to characterize the dispersion process in the dispermeter and in a dissolver. Moreover, this model was used to predict the dispersion results obtained in the dissolver.
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  • 9
    Publication Date: 2013-06-07
    Description: Visualization of local mass transfer coefficients over the dry surface of corrugated-sheet structured packing is essential for optimizing the existing geometry of structured packing and for improving mass transfer efficiency to develop new structured packing. The local flow patterns between packing sheets and the gas-phase mass transfer coefficient at each point over the surface are illustrated by employing a wall-surface reaction model. Different turbulence models are utilized, i.e., a standard κ-ϵ model and three different low-Re-κ-ϵ models. The numerical calculation results with the Lam-Bremhorst low-Re-κ-ϵ turbulence model is found to agree well with experimental data. There are three similar regions with enhanced mass transfer efficiency in each mass transfer unit cell of structured packing. Local mass transfer coefficients at each point over the dry surface in a symmetric mass transfer unit cell of corrugated-sheet structured packings were determined. Computational fluid dynamics simulation results with a Lam-Bremhorst low-Re-κ-ϵ turbulence model and a wall-surface reaction model corresponded well with previous experimental data.
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  • 10
    Publication Date: 2013-06-07
    Description: The drying process of organic solid waste is investigated, based on an experimental study involving its drying kinetics. The experiments were conducted in a thin-layer fixed-bed dryer under various operational conditions. The problem of selecting the best fit for solid waste moisture content as a function of time is addressed as well, using artificial neural network (ANN) models and four well-known drying kinetics correlations commonly applied to biological materials. According to the statistical analysis employed, the simulations showed good results for the ANN, and the Overhults model provided optimum agreement with experimental data among all other models evaluated. Empirical correlations between the Overhults model parameters and the drying operational conditions using nonlinear regression techniques were determined. The kinetics of the drying process of solid citrus wastes in a thin-layer fixed-bed dryer under different operational conditions is investigated. By means of artificial neural networks and four well-known drying kinetics correlations, the problem of selecting the best fit for solid waste moisture content as a function of time is addressed as well.
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  • 11
    Publication Date: 2013-06-07
    Description: Lavandin essential oil has been encapsulated in poly-(ϵ-caprolactone) (MW: 4000 g mol –1 ) by means of the particles from gas saturated solutions (PGSS) process. The influence of process conditions, i.e., pre-expansion temperature and pressure, and oil/polymer mass ratio, on the morphology of particles and the efficiency of encapsulation has been analyzed. Spherical particles with particle sizes of 100–700 μm were obtained, with increasing particle sizes and more agglomeration as the oil/polymer ratio was increased. The efficiency of encapsulation was increased by conditions that favored a fast solidification of the polymer shell, including high pre-expansion pressures, reaching efficiencies up to 50 % with oil loads up to 120 mg oil/g particles. Essential oils can be used as natural cattle growth promoters or biocides, but a formulation is required in order to protect the essential oil from evaporation and degradation, and to provide a controlled delivery. The encapsulation of lavandin essential oil in polycaprolactones by a particles from gas saturated solutions (PGSS) process is presented, analyzing the influence of process parameters on the morphology of particles and the efficiency of encapsulation.
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  • 12
    Publication Date: 2013-06-07
    Description: CO 2 /N 2 gas separation was performed over a nanocrystalline zeolite tetraethylammonium (TEA)-beta membrane prepared on a stainless-steel porous disc by repeated hydrothermal crystallization. Two to three consecutive hydrothermal syntheses were required to form a membrane comprised of a continuous and compact layer of zeolite beta nanocrystals on the support. The membrane TEA-BEA3 obtained by three consecutive syntheses, in which the membrane from two consecutive syntheses was used as support, exhibited the highest structural order. When the separation experiment was performed over this membrane without applying any external applied pressure, 100 % selectivity of CO 2 over N 2 was observed. The separation was driven by differences in chemical potentials of the molecules generated only by the adsorption-desorption behavior of the gases into the membrane. The novel zeolite TEA-beta membrane provided promising results for the separation of small gas molecules due to the combined influence of diffusion and sorption selectivity. Nanocrystalline zeolite tetraethylammonium (TEA)-beta membranes were prepared by repeated coating of zeolite nanocrystals via hydrothermal crystallization from a colloidal solution over a porous stain-less-steel disc support. When the separation experiment was performed without applying any external pressure, a CO 2 selectivity over N 2 of 100 % could be achieved.
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  • 13
    Publication Date: 2013-06-06
    Description: Ad- and desorption are common techniques for the purification of natural substances. The main drawback is the tedious experimental procedure for resin and solvent screening. An approach of fully automated batch experiments is presented. In order to fulfill all requirements like automation of flexible dosing of loose resins, handling organic solvents, and providing reproducible conditions, these experiments are performed on a custom-built modular robotic platform. The batch ad- and desorption experiments were fully automated for the determination of essential process parameters like kinetics, isotherms, and thermodynamic parameters without the need of manual intervention. Thus, the hands-on time could be significantly reduced by more than 90 % which contributes to improved health and safety outcome by preventing the contact of operators to potentially hazardous materials. A fully automated and highly flexible ad- and desorption method for batch resin, solvent, and condition screening experiments was developed and implemented on a robotic platform, enabling the determination of essential process parameters without manual intervention. The hands-on time was significantly reduced, contributing to improved health and safety outcome for operators.
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  • 14
    Publication Date: 2013-06-07
    Description: In situ radio-frequency heating (ISRFH) combined with soil vapor extraction was demonstrated at a contaminated field site of a former hydrotreatment plant in Zeitz near Leipzig. The project was carried out in several phases including cold soil vapor extraction for comparison. During the test, a soil volume of about 300 m 3 was heated to an average temperature of 54 °C. As expected, the extraction rate for hydrocarbons (especially the main contaminant benzene) was markedly enhanced by soil heating. Furthermore, microbial degradation of organic compounds was supported. Although a total amount of approximately 1.4 t of hydrocarbons was removed from the soil, the demonstration project was not aimed at complete remediation of the site. Conditions limiting the extent of cleanup are discussed in detail and conclusions for an efficient application of ISRFH in soil remediation are derived whereas experiences from other sites are also implied. Potential and limitations of the combination of in situ radio-frequency heating (ISRFH) and soil vapor extraction are exemplarily discussed for a demonstration project carried out at a former industrial site. Conditions restricting the extent of cleanup are discussed and conclusions for an efficient application of ISRFH in soil remediation are deduced.
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  • 15
    Publication Date: 2013-06-07
    Description: The physical stability of emulsions can be related to changes in the droplet size distribution over time. Stability control of emulsions used as metal working fluids is an important factor for the machining industry due to the decreased performance of aged and broken emulsions. Results of turbidimetric spectra measurements of metal working fluids for process control purposes and emulsion stability monitoring are discussed. Metal working emulsions were artificially destabilized by admixing salts which resulted in droplet coagulation. The destabilization process was investigated by measuring the droplet size distribution and the turbidity spectra over time. The results were evaluated based on quantitative criteria proposed in the literature. The applicability of these criteria to evaluate metal working fluids during machining operations is discussed. The destabilization process of a commercial metal working fluid (MWF) emulsion artificially aged with CaCl 2 was characterized by UV-Vis-NIR spectroscopy. The wavelength exponent proved as a quantitative criterion in monitoring of the emulsion destabilization. This simple method can be applied to in situ characterization of MWF quality in machining processes.
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  • 16
    Publication Date: 2013-06-08
    Description: A scale-down study of an industrial reactor for the production of polyvinyl chloride (PVC) via an emulsion polymerization process was performed in order to understand the source of batch-to-batch variations in product quality. In Part 2 of this series of three papers, it is demonstrated that a large excess of base is required to control the particle size distribution of the seed process. Although differences exist between the critical micelle concentration and the surface area occupied by a surfactant molecule for linear and branched isomers of the surfactant sodium dodecyl benzene sulfonate, the characteristics of the molecules from different suppliers were reasonably similar. A scale-down study of an industrial reactor for PVC production by means of emulsion polymerization is presented with the aim to identify the source of batch-to-batch variations in product quality. In Part 2 of this series of papers, the necessity of a large excess of base to control the particle size distribution of the seed process is demonstrated.
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  • 17
    Publication Date: 2013-06-08
    Description: SO 2 and NO are the main precursors for acid precipitation. Experimental studies on desulfurization and denitrification were carried out using microwave irradiation over activated carbon carried catalyst. The results show that adsorption capacities and removal efficiencies of activated carbon carried Cu-based catalyst were higher than Mn-based or Zn-based ones. The adsorption capacity of SO 2 improved with the increasing moisture in flue gas, but the adsorption capacity of NO had a peak at 6.23 mg g –1 and then began to drop. The desulfurization efficiency increased with O 2 content in flue gas, but no noticeable change of denitrification efficiency was observed from the experimental data. The desulfurization efficiency descended with the increase of moisture in flue gas, while the denitrification efficiency augmented earlier and reached a plateau later with the addition of the water steam. In addition, characterization of activated carbon confirmed that the main active component of Cu-based catalyst is CuO. The addition of a catalyst can improve the removal efficiencies for SO 2 and NO and lower the reaction temperatures. Optimum experimental parameters were determined. The characterization of activated carbon by X-ray diffraction confirmed that the main active component of the catalyst is CuO, which has different valences in the reductive atmosphere, resulting in high microwave absorption ability.
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  • 18
    Publication Date: 2013-06-08
    Description: A scale-down study of an industrial reactor for the production of polyvinyl chloride (PVC) via an emulsion polymerization process was carried out in order to understand the cause of batch-to-batch variations in product quality. The results in Part 2 of this series of papers indicated that a large excess of base is required to control the particle size distribution (PSD) of the seed process. Here, it is demonstrated that the flow rate of the initiator and the second-stage surfactant are the most important parameters for PSD control. Altering the time point at which the initiator and surfactant are injected allows controlling the relative volume fractions of large and small particles. In Part 3 of a scale-down study on an industrial reactor for PVC production, the flow rate of initiator and second-stage surfactant proved to be the most important parameters for particle size distribution control. Changing the time point of injection of initiator and surfactant enables controlling the volume fractions of large and small particles.
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  • 19
    Publication Date: 2013-04-06
    Description: The potential of binderless briquetting as a means of transforming low-rank coals into low moisture high grade solid fuel products has been studied. Using two dried low-rank coals, binderless briquettes with high mechanical strength have been successfully produced through mechanical compression. An increase in heating value was achieved as a result of moisture reduction in the briquettes compared to as-received coals. The residue moisture content in the briquettes had a predominant effect on briquetting characteristics and there existed an optimum moisture content for the maximum briquettes strength. The chemical structure and wettability of binderless briquettes were analyzed using FTIR and contact angle measurement. The results showed that hydrophobicity and chemical structure significantly affected the briquette properties. High mechanical strength binderless briquettes using two dried low-rank coals were successfully produced. Drying of low-rank coals prior to briquetting resulted in 30–50 % increase in calorific value. The optimum moisture content for high compressive strength was 12–15 %. The aromaticity of the briquettes was higher than raw coals as a result of decomposition of oxygen functionalities and aliphatic hydrogen groups.
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  • 20
    Publication Date: 2013-04-06
    Description: The effect of pressure on the possible existence of multiple steady states in bubble column reactors is investigated. A mathematical model involving fast pseudo first-order kinetics is employed to describe the performance of non-isobaric, non-isothermal reactors. The numerical analysis reveals that the existence of multiplicity is sensitive to pressure variation, yet high-pressure operating conditions do not necessarily lead to a higher likelihood of multiplicity in these contactors. Bubble column reactors are widely used in industry for a variety of gas-liquid and biochemical reactions. The occurrence of steady-state multiplicity in non-isobaric bubble column reactors is examined using a mathematical model and the sensitivity of the reactor performance to pressure variation is investigated.
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  • 21
    Publication Date: 2013-04-06
    Description: The present work reports the effect of bentonite clay on methane hydrate formation and dissociation in synthetic seawater of salinity 3.55 % of total dissolved salts. Extensive observations of pressure-temperature equilibrium during formation and decomposition of methane hydrate under different conditions have been made. It is observed that phase equilibrium conditions of hydrate are affected on changing the concentration of bentonite clay in synthetic seawater. Induction time for hydrate nucleation has been measured under different concentrations of clay and subcooling conditions. The presence of bentonite clay in synthetic seawater reduces the induction time of hydrate formation. Enthalpy of hydrate dissociation is calculated by Clausius-Clapeyron equation using measured phase equilibrium data. The amount of gas consumed during hydrate formation has been calculated using real gas equation. It is found that a larger amount of gas is consumed upon addition of bentonite clay in synthetic seawater. Bentonite clay is used for methane hydrate formation in synthetic seawater. Reaction kinetics and hydrate formation pressure and temperature are studied under different conditions. Bentonite clay is further-more investigated in terms of surface morphology, chemical changes due to hydrate formation and particle size distribution in suspension.
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  • 22
    Publication Date: 2013-04-05
    Description: An engineered process for scalable manufacture of a calcium aluminum carbonate CO 2 sorbent with production amounts of about 1000 g per hour has been developed. The process includes mixing and heating, solid-liquid separation, drying and extrusion, crushing and conveying, and calcined molding steps. The sorbent preparation involves the coprecipitation of Ca 2+ , Al 3+ , and CO 3 2– under alkaline conditions. By adjusting the Ca:Al molar ratio, a series of Ca-rich materials could be synthesized for use as CO 2 sorbents at 750 °C. A calcium acetate-derived sorbent exhibited better cyclic stability than sorbents originating from CaCl 2 and Ca(NO 3 ) 2 . The initial sorption capacity increased with CaO concentration. High stability of more than 90 % was maintained by the Ca:Al sorbents after 40 looping tests. The main advantages using CaO-based sorbents for high-temperature CO 2 capture are their high capacity and advanced CO 2 uptake characteristics. A novel process for scalable manufacture of a calcium aluminum carbonate CO 2 sorbent is introduced. Using this method, CO 2 sorbents with significantly improved performance can be produced in kg-batches.
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  • 23
    Publication Date: 2013-04-05
    Description: Amine solutions were applied in carbon dioxide removal from a model mixture of biogas, carried out in a loop reactor system. In addition, the effect of CO 2 absorption acceleration in the presence of piperazine was confirmed and quantified, relating the obtained CO 2 loading with the piperazine concentration. Further, the interactions of CO 2 and water in aqueous amine solutions were discussed. The obtained acid gas loadings were accurately described taking into account the effect of the dissolved CO 2 on the equilibrium constant. A logarithmic absorption isotherm that follows from such considerations and a saturation-type isotherm were compared. In describing the experimental data, advantages and disadvantages of both approaches are discussed. The absorption performance of piperazine-containing amine solutions to be used for biogas upgrading was investigated in terms of CO 2 capture. The suggested approach was utilized to describe the non-ideality of the absorption isotherms and proved to be suitable also for data reported by other research groups.
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  • 24
    Publication Date: 2013-04-06
    Description: An ultrasonic enhanced salt-containing hydrodistillation (UESHD) method for separating essential oil from lavender ( Lavandula angustifolia ) flowers was investigated using response surface methodology (RSM). The experimental data obtained from a 27-run experiment were fitted to a second-order polynomial equation. The optimal conditions were determined by the 3D response surface and the contour plots derived from the models. The efficiency of UESHD and conventional hydrodistillation (HD) was compared. The extraction yield of UESHD was two-fold higher than that of HD. In addition, GC-MS results indicated some differences in composition and content between the two essential oils from UESHD and HD. An ultrasonic enhanced salt-containing hydro-distillation (UESHD) method was developed to separate lavender essential oil. The extraction yield of the oil was optimized by statistical software, the separation conditions by the Box-Behnken design. UESHD enabled a more than two-fold yield of essential oil than conventional hydrodistillation.
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  • 25
    Publication Date: 2013-09-07
    Description: The effects of operating conditions on radial variation of gas holdups, bubble swarm rising velocity, and Sauter mean diameter were investigated in a bubble column reactor under elevated pressures using a conductivity probe method. Air served as gas phase and tap water as liquid phase with varying gas velocity and pressure. All three parameters increased constantly with higher superficial gas velocity. Maximum holdup, velocity, and Sauter mean diameter were found at the center of the cross section. Two different cases for Sauter mean diameter distribution were observed. The gas holdups increase continuously with higher system pressure, but decrease for bubble swarm rising velocity and Sauter mean diameter. According to experimental results, an empirical correlation of the gas holdup profiles is presented. Experimental data on the distribution of gas holdup, bubble swarm rising velocity, bubble size distribution, and Sauter mean bubble diameter in an air-water system are presented. The effects of operating conditions were evaluated in a bubble column reactor under elevated pressures and churn-turbulent flow regime applying a conductivity probe method.
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  • 26
    Publication Date: 2013-09-07
    Description: Drying is considered as an intensive operation that consumes large quantities of energy. Usually, baker's yeast is obtained using freeze drying or fluidized-bed drying, both of which are considered as expensive technologies. So, exploring other techniques such as contact drying could limit this disadvantage. In addition, no work dealing with contact drying of baker's yeast has been accomplished yet. Therefore, here, the behavior of baker's yeast during vacuum agitated contact drying is presented. The results show that the drying process can be divided into three phases: the pasty phase, the lumpy phase, and the granular phase. The influence of the drying parameters, such as the temperature, the impeller velocity, and the initial mass, was also studied. It was found that the wall temperature and the impeller velocity have a positive effect on the drying kinetics, as their increase allows a reduction in the drying time. Nevertheless, an increase in the pressure level or the initial mass of the product caused the drying time to increase. The behavior of baker's yeast during vacuum agitated contact drying is studied. The wall temperature and the impeller velocity have a positive effect on the drying kinetics, as their increase leads to a reduction in the drying time, whereas an increase in the pressure level or the initial mass of the product increases the drying time.
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  • 27
    Publication Date: 2013-09-07
    Description: Nucleation kinetics and a growth model of penicillin sulfoxide in butyl acetate were studied. Nucleation parameters such as energy per unit volume, radius of critical nucleus, critical free energy barrier, and nucleation rate were evaluated. A laser method was selected to detect the first crystal in induction period studies. By means of scanning electron microscopy and surface entropy factor, the growth model of penicillin sulfoxide developed from butyl acetate could be determined. According to the results of nucleation kinetics and the growth model of penicillin sulfoxide in butyl acetate, production process parameters can be optimized. The products of penicillin sulfoxide exihibit high purity and provide long-lasting forms of storage. The results are essential for crystallization process control of penicillin sulfoxide in industry.
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  • 28
    Publication Date: 2013-09-07
    Description: Oxygen mass transfer from air to the liquid phase in bioreactors with aerobic cultures has long been a serious impairment to the productivity of various bioprocesses. An increase of the oxygen mass transfer rate (OTR) can be the key to overcome oxygen limitation. The influence of higher air pressure on OTR was measured and a significantly enhanced OTR could be obtained. The oxygen volumetric mass transfer coefficient ( k L a ) was described by a function of the air pressure in a stirred lab-scale pressurized bioreactor. The correlation obtained proved that k L a slightly decreased with higher air pressure, following a power function. The oxygen mass transfer rate (OTR) and oxygen volumetric mass transfer coefficient ( k L a ) must be known to achieve optimum design operation and avoid oxygen transfer limitations. An increased air pressure is an important approach to enhance OTR and k L a . The proposed correlation could be valuable for further process optimizations where oxygen transfer is a limiting factor.
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  • 29
    Publication Date: 2013-09-07
    Description: A MnCu-mixed oxide catalyst supported on a cordierite monolith was synthesized. The catalyst showed very good stability and high homogeneity and presented an excellent catalytic activity in the combustion of ethyl acetate, n- hexane, and its mixture. The total conversion temperature of the mixture was determined by the temperature at which the most difficult molecule was oxidized. An excellent catalytic activity in the combustion of ethyl acetate, n- hexane and its mixture was obtained with a MnCu/cordierite monolith catalyst. The monolithic catalyst was synthesized using a simple and reproducible method. Catalysts with homogeneous and well-adhered coatings were obtained. The simplicity of the method used favors scaling for industrial applications.
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  • 30
    Publication Date: 2013-09-07
    Description: Nano-alumina powders containing yttrium oxide were synthesized via the sol-gel method using aluminum chloride hexahydrate as catalyst precursor. Fourier transform infrared analysis showed the presence of Al-O and Al-O-Al bands in the powder structure and X-ray diffraction spectra proved that the alumina was in the amorphous phase. The amorphous nano-alumina powders were shown to be mesoporous with a high surface area, and both spherical and slit-shaped particles were found in the calcined powder. A high percentage of conversion of oil to biodiesel was obtained in the transesterification reaction and the synthesized nano-alumina powders could be easily regenerated for further use. The amorphous nano-alumina powder can thus be recommended for use as active catalyst in the transesterification reaction for biodiesel production on the industrial scale. A novel catalyst for use in the transesterification reaction for biodiesel production was synthesized and characterized. A simple, reliable and cost-efficient sol-gel technique is proposed, leading to amorphous alumina powders with high surface area and nano-sized particles, appropriate for industrial applications.
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  • 31
    Publication Date: 2013-09-07
    Description: A series of Mg-modified SBA-15 mesoporous silicas with different MgO contents were successfully synthesized by a simple one-pot synthesis method and further impregnated with Ni. The Mg-modified SBA-15 materials and supported Ni catalysts were characterized by N 2 physisorption (BET), X-ray diffraction (XRD), temperature-programmed desorption of CO 2 (CO 2 -TPD), temperature-programmed H 2 reduction (H 2 -TPR), and temperature-programmed hydrogenation (TPH) techniques and used for methane dry reforming with CO 2 . CO 2 -TPD results proved that the addition of Mg increased the total amount of basic sites which was responsible for the enhanced catalytic activity over the Mg-modified Ni catalyst. The excellent catalytic stability of Ni/8Mg-SBA-15 was ascribed to less coking and higher stability of the Ni particle size due to the introduction of Mg. Mg-modified SBA-15 mesoporous materials with varying Mg contents were successfully synthesized by a one-pot approach and applied as support for Ni-based catalysts. The incorporation of Mg to Ni/SBA-15 catalyst remarkably decreased the active Ni particle size via metal-support interaction and yielded a high resistance ability to coke deposition.
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  • 32
    Publication Date: 2013-09-11
    Description: Methanation of CO under unsteady-state operation conditions was studied systematically based on a simplified mathematical model for an integral reactor using steady-state kinetics available in the literature. The inlet composition of CO and H 2 was changed stepwise and the step response of the system was monitored in order to study the dynamic behavior of the reactor. Furthermore, periodic changes were applied with different cycling times. It was observed that the time average reaction rate could not be improved by cycling the feed composition. Moreover, the reactor appears to be self-stabilizing, since the amplitude at the outlet is reduced, leading to a steady state for high cycling frequencies. The results allow conclusions on principles to design a methanation reactor for unsteady-state operation. However, it also becomes obvious that unsteady-state kinetics is mandatory in order to describe the experimental results obtained under dynamic conditions. Methane is one important backbone for the energy supply in today's western world. Methanation under unsteady-state operation conditions was studied based on a mathematical model. The inlet composition of CO and H 2 was varied stepwise to study the dynamic behavior of the reactor for different cycle periods. It was observed that the reactor behaves in a self-stabilizing manner.
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  • 33
    Publication Date: 2013-09-11
    Description: Polyethersulfone (PES) dope solutions were prepared from mixtures of two solvents containing N , N -dimethylformamide (DMF) as core solvent and acetone as co-solvent (CS) in a closed heating system. PES asymmetric membranes were cast by a dry/wet phase inversion process. Complete miscibility of PES with the fixed mixture of acetone and DMF under atmospheric pressure could be achieved. The kinetic and thermodynamic properties indicated that interaction of DMF and acetone is strongest when their mole ratio is unity, pointing to the phenomenon of true co-solvency for PES dissolution. These results were supported by determination of the water uptake, contact angle measurement, and SEM analyses. Membrane performance, pore volume, and total pore volume on the membrane surface were also investigated. From mixtures containing N , N -dimethylformamide (DMF) as core solvent and acetone as co-solvent, polyethersulfone (PES) dope solutions were prepared. Membranes produced from such dope solutions containing acetone turned out to be superior in terms of permeation flux rates, rejection rates, and quality compared to membranes prepared without acetone.
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  • 34
    Publication Date: 2013-09-11
    Description: Alginate hydrogel beads are widely used as an encapsulation medium for biomedical, bioprocessing, and pharmaceutical applications. The size and shape of the beads are often critically controlled since in many usages the beads are monodisperse in size and spherical in shape. Extrusion dripping is a well-known method to produce alginate beads. Nevertheless, the production of beads of desired size and spherical shape is often achieved based on one's experience or trial and error. An overview is provided on alginate properties, formulation and preparation of alginate and gelling solutions, production conditions, and post-production treatment that may influence the bead size and shape. Various methods of bead size and shape measurement are also discussed. The influence of significant process variables like alginate properties, formulation and preparation of alginate and gelling solutions, production conditions, and post-production treatment on size and shape of Ca-alginate beads is reviewed. Various methods for bead size determination and shape analysis are described in detail and discussed.
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  • 35
    Publication Date: 2013-09-11
    Description: The influence of mechanical stress on the crystal size distribution of lysozyme crystal slurries in a dynamic cross-flow device is discussed. The reduction of crystal size may have an influence on mass and resistance of the fouling layer. A filter test device with a filter area of 130 cm 2 is used for thickening. After thickening, a model impurity, namely bovine serum albumin, is washed out of the suspension. A reduction of crystal size due to stirring and a reduced fouling layer with increasing stirrer speed is observed. Furthermore, a higher stirring speed increases the specific filtrate flux. In the presence of the impurity, more crystal aggregates than single isometric crystals are formed and, hence, the decrease of crystal size due to shear forces is more pronounced than without impurity. Protein crystals are in comparison to other organic and nonorganic crystals very soft and fragile. During separation in a dynamic cross-flow device a decrease of the crystal size is observed due to crystal breakage which could influence the separation and following product formulation steps. The impact of stirring speed and residence time is discussed for lysozyme crystals.
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  • 36
    Publication Date: 2013-09-25
    Description: The kinetics of bioethanol production using mono- and co-cultures of Saccharomyces cerevisiae and Pichia stipitis with glucose, xylose, and glucose-xylose sugar mixtures were investigated. A MATLAB® program was formulated for simulation of experimental results in order to get predicted values of ethanol production and sugar consumption and for kinetic parameter estimation. Kinetic parameters implied less extent of substrate and/or product inhibition when the co-culture scheme of immobilized S. cerevisiae and free P. stipitis was employed for fermentation of mixed sugars. In addition, a high ethanol yield was achieved by applying this co-culture strategy to wheat straw hydrolysates. The kinetics of bioethanol production with single and mixed-sugar fermentation employing mono- and co-cultures of Saccharomyces cerevisiae and Pichia stipites were determined. Bioconversion of concentrated wheat straw hydrolysates to ethanol was successfully performed using a co-culture of immobilized S. cerevisiae and free P. stipitis .
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  • 37
    Publication Date: 2013-09-25
    Description: In order to find alternative low-cost adsorbents for volatile organic liquids, the effectiveness of nickel oxide nanoparticles-modified diatomite (NONMD) in removing benzene was assessed. The impact of different operation parameters such as pH, contact time, initial benzene concentration, and adsorption dosage on the adsorption process was evaluated and optimum experimental conditions were identified. Surface area and morphology of the nanoparticles were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) isotherms, X-ray diffraction (XRD), Fourier transform infrared (FTIR), and energy dispersive X-ray (EDX) analysis. The isotherm and kinetics effect of the adsorbent were evaluated. The efficiency of NiO nanoparticles-modified diatomite for benzene removal from an aqueous medium was evaluated in order to find alternative low-cost adsorbents for volatile organic liquids. The impact of different operation parameters on the adsorption process was assessed and optimum experimental conditions for nearly 100 % benzene removal were defined.
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  • 38
    Publication Date: 2013-09-25
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  • 39
    Publication Date: 2014-11-08
    Description: The possibility of predicting the droplet size distribution from the particle size distribution was investigated. For that purpose, suspensions of different types of materials were dried in a laboratory-scale spray drier. Drying of suspensions was performed with different sizes of two-fluid nozzles. Droplet size distribution was evaluated from the data obtained for spray drying of bismuth molybdate suspension. The method was validated experimentally with other tested materials. Investigated systems involve processes of drying, crystallization, and coating. The proposed methodology can be applied when nonagglomerated particles, spherical particles, or spherical agglomerates were obtained by spray drying. Spray drying is a unique drying process since formation of solid phase and drying occur simultaneously. Droplet size distribution produced by a two-fluid nozzle during spray drying of bismuth molybdate suspension was evaluated simply from the particle size distribution. The proposed methodology enables prediction of the particle size distribution obtained by spray drying.
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  • 40
    Publication Date: 2014-11-08
    Description: The influence of vibration parameters on the segregation phenomenon of a binary mixture in a vibration fluidized bed is investigated. Initially, the mixture composed of spherical balls with different densities but same diameter is in a perfect mixing state in the bed. The motion of particles is simulated based on the discrete element method. The effects of friction coefficient, vibration frequency, amplitudes, and gas velocity are analyzed. The coefficient of segregation to the degree of particle segregation is calculated for different operating conditions. The segregation degree in the vibration fluidized bed is found to be higher than that in the bed without vibration. The curve for the segregation degree exhibits a single peak value which represents the optimal segregation result. The impact of vibration on gas phase- and particle flow is not yet clarified due to the complex motion of particles in vibrated fluidized beds. Discrete particle simulation is used to investigate the segregation behavior of binary mixtures in a fluidized bed. The effect of vibration parameters and suitable operating conditions for segregation, particle distribution, and particle motion are evaluated.
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  • 41
    Publication Date: 2014-11-08
    Description: The effects of a turbulence-generating grid on fluid mixing and a passive chemical reaction are experimentally investigated in a liquid shear mixing layer under a nonpremixed condition. The grid is installed at three streamwise locations to find the optimal location to promote the chemical reaction. The results show that the grid generates disturbances at small scales that enhance fluid mixing and the chemical reaction. However, the turbulence intensity and mass diffusion in the mixing layers with the grid decrease rapidly and become even smaller than those in the mixing layer without the grid in a downstream region. Therefore, in the present study, the chemical production is maximized when the grid is installed at where the flow is turning to a developed mixing layer. Installation of a turbulence-generating grid is advantageous to promote fluid mixing and chemical reaction in a free shear flow in which the reactive fluids are introduced under a nonpremixed condition. Special attention is needed regarding the location of the grid to maximize the promotion effect since it could be better to install it in the downstream region rather than the upstream region.
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  • 42
    Publication Date: 2014-11-08
    Description: Bubble splitting in 2D gas-solid freely bubbling fluidized beds is experimentally investigated using digital image analysis. The quantitative results can be applied for the development of a new breakage model for bubbly fluidized beds, especially discrete bubble models. The variation of splitting frequency with bubble diameter, new resulting bubble volumes, positions, and also the assumptions of mass and momentum conservation for bubbles after breakage are studied in detail. Small bubbles are found to be more stable than large ones and nearly all mother bubbles split into two almost equally sized daughter bubbles. The momentum of gas bubbles in the vertical direction remains approximately constant after breakage, whereas that of bubbles in the horizontal direction changes with no clear trend. The effect of fluidizing gas velocity in breakage frequency is also examined. The behavior of gas bubbles plays a key role in heat- and mass-transfer operations in fluidized beds. Bubble splitting for Geldart B-type particles under varying conditions was investigated in a pseudo-2D gas-solid fluidized bed by digital image analysis. The quantitative results can facilitate the development of new breakage models for bubbly fluidized beds and are particularly relevant for discrete bubble modeling.
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  • 43
    Publication Date: 2014-11-08
    Description: For the application of microreactors in industrial processes, more scaling-up strategies are still required except of the original concept, the numbering-up. A more maneuverable and economic approach, combining both similarity-up and numbering-up, is introduced as an example for an innovative strategy. CFD simulation is also applied to assist analysis and optimization of fluid distribution. Based on this concept, named similarity-up + numbering-up + simulation, a pilot-plant microsieve dispersion minireactor used to proceed the reaction of cyclohexanecarboxylic acid and oleum is designed and tested experimentally. With the contribution of similarity-up, the treating capacity of the core unit is significantly increased. Ten parallel units are integrated to form a correspondingly enhanced capacity of the microreactor which exhibits low pressure drop, stable operating performance, and excellent main product selectivity. For industrial applications of microreactors, more flexible and economic scaling-up strategies are required. A scale-up approach for a microsieve dispersion reactor is proposed, combining similarity-up and numbering-up of the core unit with CFD simulation-based device structure optimization. Low fabrication cost, low pressure drop, and excellent main product selectivity can be achieved by this strategy.
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  • 44
    Publication Date: 2014-12-19
    Description: A new design of conjugated heat transfer in double-pass parallel-plate laminar countercurrent operations of power law fluids under wall isoflux was investigated experimentally and theoretically. The analytical solutions were obtained with a superposition model by introducing an eigenfunction expansion in terms of a power series for the homogeneous part and an asymptotic solution for the inhomogeneous part. The influence of the power law index on the average Nusselt numbers with the various design and operating parameters is also delineated. The theoretical predictions of the experimental results are represented graphically. The heat transfer performance was considerably improved when compared with a single-pass parallel-plate heat exchanger (without inserting a solid separator sheet). Suitable adjustments of the solid separator sheet position can effectively enhance the heat transfer efficiencies for such a recycling double-pass device, as compared with the efficiencies of single- and double-pass devices.
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  • 45
    Publication Date: 2011-06-10
    Description: Several issues pertinent to intermittent drying of clay-like materials were analyzed with respect to energy consumption, quality of dried products, and drying time. Experimental tests were performed on the cylindrically-shaped kaolin samples for batch convective drying realized with both periodically alternated temperature and humidity of the drying air. To assess the benefits from intermittent drying, a series of tests were carried out at both parameters kept constant. The net energy necessary for material heating and moisture evaporation was numerically calculated based on the authors' model of drying kinetics, and related to the experimentally measured total electric energy consumption to evaluate the effectiveness of intermittent drying. The quality of dried samples was quantified in terms of crack intensity and magnitude. It was found that intermittent drying permits much better product quality with comparable drying time and energy consumption when drying occurs under constant conditions. Intermittent drying of clay-like materials was studied with respect to energy consumption, quality of dried products, and drying time. The kinetics of intermittent drying was determined experimentally for kaolin KOC samples of cylindrical form and a mathematical model of drying kinetics was used to numerically calculate the corresponding kinetic curves.
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  • 46
    Publication Date: 2011-06-16
    Description: A stochastic Monte Carlo method was used to solve the population dynamics of fluidized-bed granulation. Special emphasis was put on the addition of liquid to the process and on the microprocess of droplet pre-drying. Pre-drying can occur during the flight of droplets from the tip of the nozzle to the fluidized bed, especially in top-spray configuration. A single-droplet drying model that considers the change of droplet diameter and of the radial concentration profile of binder in the droplet was developed and validated by experiments in an acoustic levitator. Combined with spray flow field considerations, this model can be used to retrieve an initial droplet diameter from spray measurements. Integrated in the Monte Carlo simulation, it shows that pre-drying can significantly decrease the agglomeration rate due to overspray and premature solidification instead of successful droplet deposition. The Monte Carlo method is used to describe agglomeration in spray fluidized beds. Special focus is put on the pre-drying of droplets during their flight from the nozzle tip to the expanded particle bed. Pre-drying is modeled, validated by experiments on single droplets in an acoustic levitator and integrated in the MC simulation. The latter shows that excessive pre-drying may prevent droplet deposition and thus inhibit agglomeration.
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  • 47
    Publication Date: 2011-06-29
    Description: The objective of this study is to describe moisture distribution in a rotating porous cylinder. Variable orientation of the gravitational and centrifugal forces during rotation causes rather complex, unsteady distribution of the moisture content. The optimal speed of rotation which provides the minimum nonhomogeneity of the distribution can be found. A cell model for this purpose is proposed. The model is based on the theory of Markov chains. Transition probabilities in the chain of cells are conditioned by pure diffusion and convection caused by the forces. The basic features of the process are investigated and the optimal process parameters are found. A model that describes moisture distribution in a horizontal rotating porous cylinder is proposed. For the case of no rotation, moisture concentrates at the bottom of the cylinder; at rotations that are too fast, it concentrates at the periphery of the cylinder. In both cases, its distribution is very nonhomogeneous. At optimal speed, the most homogeneous distribution can be reached.
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  • 48
    Publication Date: 2011-06-29
    Description: An improved mesoscopic model is presented for simulating the drying of porous media. The aim of this model is to account for two scales simultaneously: the scale of the whole product and the scale of the heterogeneities of the porous medium. The innovation of this method is the utilization of a new mass-conservative scheme based on the Control-Volume Finite-Element (CV-FE) method that partitions the moisture content field over the individual sub-control volumes surrounding each node within the mesh. Although the new formulation has potential for application across a wide range of transport processes in heterogeneous porous media, the focus here is on applying the model to the drying of small sections of softwood consisting of several growth rings. The results conclude that, when compared to a previously published scheme, only the new mass-conservative formulation correctly captures the true moisture content evolution in the earlywood and latewood components of the growth rings during drying. A new mesoscopic model was proposed for simulating the drying of porous media. Applying the new model to cross-sections of a pinewood board, the distribution of water within each control volume is correctly captured, which provides a better representation of the true moisture content distribution during drying.
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  • 49
    Publication Date: 2011-06-29
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  • 50
    Publication Date: 2011-06-29
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  • 51
    Publication Date: 2011-06-29
    Description: The prediction of droplet size distributions for atomization nozzles is important for process design and improvement of industrial spraying processes. However, especially for non-Newtonian liquids, the published research applicable for engineering purposes is rare. To derive fundamental correlations for droplet size distributions in the future, the multiphase flow inside the spray nozzle is investigated by computational fluid dynamics, and measurements of droplet size distributions are done under the same flow conditions. In the present paper, two different hollow-cone nozzles were investigated using the volume-of-fluid method with large-eddy turbulence modeling inside the open source software OpenFOAM®. An experimental test rig suitable for spraying organic solvents was built. To derive fundamental correlations for droplet size distributions for non-Newtonian liquids in atomization nozzles, the multiphase flow inside the spray nozzle is investigated by computational fluid dynamics; measurements of droplet size distributions are done under the same flow conditions. Two different hollow-cone nozzles were investigated using the volume-of-fluid method with large-eddy turbulence modeling. An experimental test rig suitable for spraying organic solvents was built.
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  • 52
    Publication Date: 2011-06-10
    Description: The formation and distribution of condensed vapor during the freeze drying of porous polymer hydrogels are numerically evaluated. The sublimation-condensation model is developed by CFD simulation to investigate phase change in the freeze drying process. Scanning electron microscopy (SEM) was used to investigate the structure of cross-linked gelatine and an idealized geometry model was applied to determine interconnected pore structure. The simulation explores the influence of various parameters on condensation and drying rate, including temperature, pressure, pore diameter, liquid volume fraction, and porosity. The optimum temperature is estimated to enhance drying rate and decrease condensation in the freeze drying process. The results show that condensation in porous materials depends on capillary forces and cause invasion percolation patterns. A CFD model was generated to simulate phase change in the freeze drying process with a two-phase mixture model. Slip flow, buoyancy, and capillary forces in micropores were analyzed with suitable boundary conditions. Numerical methods were extensively used to solve mass transport, continuity, and momentum and energy equations with the finite volume method.
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  • 53
    Publication Date: 2011-06-22
    Description: The critical slip planes at the silo filling state are compared with the flow channel boundary during silo discharge for semi-mass flows. The static critical slip planes are determined by using the dynamic programming method based on the stress field of granular solids stored in silos at the filling state. The flow channel boundary is estimated through the finite element analysis of the silo discharge. The results indicate that the critical slip line lies above the flow channel boundary. This characteristic can be attributed to the changeover of major principal stress directions of granular solids from the silo filling to the silo discharge. The analysis demonstrates that the silo wall friction tends to lift up the critical slip plane and flow boundary. A simple correlation is developed between the positions of critical slip planes and flow boundaries and is experimentally verified. Identifications of flow channel boundaries in silos are studied by using a static slope stability analysis and the dynamic finite element method. A simple approach is developed and experimentally verified to identify positions of flow channel boundaries. The disagreements of diverse assumptions of flow channel boundaries in numerical computations concerning silo discharges are identified.
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  • 54
    Publication Date: 2011-06-29
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  • 55
    Publication Date: 2011-06-29
    Description: A nonequilibrium model was developed and simulated by adopting a dual-scale pore network approach. The distributions of temperature, moisture, and pressure in drying air, as well as the temperature and moisture content profiles in grain kernels were obtained from the pore scale model and the kernel scale model, respectively. A small test bin was built to conduct in-bin drying experiments and to validate the model. The results from the experiments and the simulations indicate that the dual-scale pore network approach could explain the drying process of the deep-bed grain drying process well. The influences of grain bulk porosity and cereal particle size distribution were also investigated by numerical simulations. A non-equilibrium model was developed and simulated by adopting the dual-scale pore network approach. The distributions of temperature, moisture, and pressure in drying air, as well as the temperature and moisture content profiles in grain kernel were obtained from the pore scale model and the kernel scale model, respectively. A small test bin was built to conduct in-bin drying experiments and to validate the model.
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  • 56
    Publication Date: 2011-06-29
    Description: Several fallacies commonly appear in articles or papers on drying. They fall into two main categories: inadequate or discredited theory which continues to be repeated, and theoretical models which are too complex for practical use, generate results in the wrong form, or do not take account of measurement limitations. Cases are highlighted where published theory is inadequate (e.g., Page's equation) and where simplified models can have better fitness for purpose than complex ones (e.g., in fluidized bed drying). The universal drying curve (UDC) is a useful concept for rapid evaluation of drying in deep well-mixed beds. Simplified drying models can be superior to complex models requiring extensive data. Effective models include the universal drying curve (UDC) as a useful concept for rapid evaluation of drying in fluidized beds and for other convective dryers, scale-up relationships, and energy analysis methods. Conversely, the widely used Page's equation for drying kinetics is an inaccurate oversimplification.
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  • 57
    Publication Date: 2011-06-29
    Description: This work proposes routes to produce dairy-based multi-component powders that meet nutritional and dissolution performance requirements. The effects of processing and composition on the physical properties of dairy powders were investigated and the relationship between such powder properties and dissolution performance was established. A spray-dried milk-based formulation was used as base powder, into which a carbohydrate, either starch or maltodextrin, was incorporated in varying proportions by dry mixing or fluid-bed agglomeration. Physical properties such as particle size, density and flowability of the resulting powders were analyzed and particular attention was given to their dissolution behavior. Incorporation of either maltodextrin or starch in the final powder composition, without compromising the dissolution performance, was achieved by fluid-bed agglomeration, provided that the amount of maltodextrin was less than 25 % or the amount of starch did not exceed 15 % and that the final agglomerate size was in the range of 250–300 μm. The effects of drying and agglomeration conditions on the physical properties of dairy-based multi-component powders were investigated, as well as the relationship between powder properties and dissolution performance. This work proposes routes to produce dairy powders containing starch or maltodextrin with good reconstitution properties.
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  • 58
    Publication Date: 2011-06-08
    Description: A mathematical model was developed to evaluate the influence of structural and operational factors on convective desorption processes (desorption of a liquid from capillary-porous material). The possibility to utilize this model for the case of water desorption from the polystyrene cation resin CG-8 is presented. The model accounts for unsteady one-dimensional simultaneous heat and mass transfer between the gas (humid air) and the solid phase (CG-8 resin). The identification of effective transport properties for the considered packed bed of material (CG-8 resin) is discussed. To this purpose, data from the literature are used. A mathematical model was developed to evaluate the influence of structural and operational factors on convective desorption processes. The possibility to utilize this model for the case of water desorption from the polystyrene cation resin CG-8 is presented. The model accounts for unsteady one-dimensional simultaneous heat and mass transfer between gas and solid phase. The identification of effective transport properties for the considered packed bed of material is discussed.
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  • 59
    Publication Date: 2011-06-10
    Description: The performance of a draft-tube conical spouted bed for drying fine particles under batch operating conditions has been assessed at several temperatures using nonporous and open-sided draft tubes, and the results have been compared with those obtained when operating without a draft tube. In order to ascertain the influence of temperature on drying, experimental runs have been carried out in the 25–300 °C temperature range. The open-sided draft tube provides the best performance due to the excellent gas-solid contact attained with this device, which enables shorter drying times. A maximum air temperature of 200 °C is recommended for energy optimization. An open-sided tube protruding above the stagnant bed by at least 2/3 of the latter's height produces much lower and denser fountains than a tube flush with the upper surface of the bed. The drying process of building sand in a bench-scale plant at different temperatures was analyzed. The performance of a draft-tube conical spouted bed for drying fine particles under batch operating conditions was assessed using nonporous and open-sided draft tubes and compared to results obtained without a draft tube. The open-sided draft tube provided the best performance due to the excellent gas-solid contact.
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  • 60
    Publication Date: 2011-06-10
    Description: A novel drying system based on self-heat recuperation (SHR) technology, which recuperates both sensible and latent heat, was developed to reduce effectively the energy consumption for biomass drying. A fluidized bed dryer with internal heat exchangers was selected as the main dryer. Square wood chips of Pinus radiata with average dimensions of 10 mm were selected as biomass sample. The relation between the required energy input and fluidization velocity and a comparison with the available mechanical vapor recompression (MVR)-based drying technology were evaluated. The results prove that the proposed SHR technology could reduce the required energy consumption for biomass drying significantly at all evaluated fluidization velocities to about 2/3 of that required for MVR-based drying technology. A novel drying system based on self-heat recuperation (SHR) technology, able to effectively recover both the sensible and latent heat, was developed. The proposed SHR-based fluidized bed dryer could significantly reduce the required energy consumption for biomass drying at all evaluated fluidization velocities to about 2/3 of that required for mechanical vapor recompression-based drying technology.
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  • 61
    Publication Date: 2011-06-29
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  • 62
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    Unknown
    Wiley
    Publication Date: 2011-06-29
    Description: Dried Particles. Courtesy: E. Tsotsas
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  • 63
    facet.materialart.
    Unknown
    Wiley
    Publication Date: 2011-06-29
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  • 64
    Publication Date: 2011-06-29
    Description: Drying has become an important step within the context of sludge management. Sometimes, sludges from several wastewater treatment plants are centralized in order to dry them at an acceptable cost. Depending on sludge supply, there can be a delay between delivery and feeding into the dryer. The impact of sludge storage duration on the drying kinetics and on the exhaust emissions of volatile organic compounds (VOCs), and ammonia is investigated. Results show that, after 20 days of storage, the drying time is multiplied by 1.5, and the emissions of VOCs and NH 3 are multiplied by 5 and 40, respectively. The impact of sludge storage duration on the drying kinetics and associated gaseous emissions of volatile organic compounds (VOCs) and ammonia at 4 °C and 12 °C is investigated. The results indicate that after 20 days of storage the drying time is multiplied by 1.5 and the emissions of VOCs and NH 3 by 5 and 40, respectively. The drying rate decreases with storage time, whereas economic and energy costs increase.
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  • 65
    Publication Date: 2011-05-12
    Description: A CO 2 capture process for an integrated gasification combined cycle (IGCC) power plant using the calcium looping cycle was proposed. The CO 2 capture process using natural and modified limestone was simulated and investigated with the software package Aspen Plus. It incorporated a fresh feed of sorbent to compensate for the decay in CO 2 capture activity during long-term cycles. The sorbent flow ratios have significant effect on the CO 2 capture efficiency and net efficiency of the CO 2 capture system. The IGCC power plant, using the modified limestone, exhibits higher CO 2 capture efficiency than that using the natural limetone at the same sorbent flow ratios. The system net efficiency using the natural and modified limestones achieves 41.7 % and 43.1 %, respectively, at the CO 2 capture efficiency of 90 % without the effect of sulfation. A CO 2 capture process for an integrated gasification combined cycle (IGCC) power plant using the calcium looping cycle was proposed. The CO 2 capture efficiency and system net efficiency for the IGCC power plant using natural and modified limestone were simulated and investigated with the software package Aspen Plus.
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  • 66
    Publication Date: 2014-12-19
    Description: In order to study emulsification phenomena, devices generating well-defined flow conditions are essential. Thus, emulsification of drop collectives under laminar shear flow is commonly performed in cylindrical Couette or Searle devices. In these devices, the flow conditions in the shear gap and in the volume underneath the rotor are often different, which can lead to inhomogeneous product properties and may complicate sample taking. Here, a novel cone-cone shear cell is presented to study emulsification processes. The flow inside the device is examined using numerical simulations. The numerical simulations indicate that simple shear flow is realized all over the sample volume in the cone-cone shear cell. The experimental results show that the drop breakup in the cone-cone shear cell is equivalent to the breakup under simple shear realized in the shear gap of a conventional device, i.e., the Searle device. Critical capillary numbers are calculated from the experimental data and show breakup behavior as predicted by single-drop experiments. Thus, the cone-cone shear cell proved to be suitable to study emulsification mechanisms in simple shear flow. Emulsion-based products are widely used in the food, chemical, and pharmaceutical industries. A novel cone-cone shear cell to study emulsification characteristics is described. The flow conditions inside the shear cell are validated via numerical simulations and experimental results.
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  • 67
    Publication Date: 2014-12-19
    Description: Hydrocracking of a bitumen-derived asphaltene over NiMo/ γ -Al 2 O 3 was investigated in a microbatch reactor at varying temperatures. The molar kinetics of asphaltene cracking reaction was examined by fitting the experimental data. Below a defined temperature, the molar reaction showed the first-order kinetic feature while at higher temperatures secondary reactions such as coke formation became significant, causing deviation of the reaction behavior from the proposed first-order kinetic model. Selectivity analysis proved that dominant products varied from gases to liquids to gases with increasing temperature, shifting the dominant reaction from C–S bonds cleavage to C–C bonds cleavage. Catalytic hydrocracking could be a proper choice for asphaltene upgrading but the reaction conditions still need to be optimized. Hydrocracking of a bitumen-derived asphaltene over a NiMo/ γ -Al 2 O 3 catalyst in a microbatch reactor at varying temperatures was analyzed. The molar kinetics of asphaltene cracking reaction was evaluated by fitting the experimental data.
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  • 68
    Publication Date: 2014-11-06
    Description: Two different types of metals (Cu and Ni) and the effect of CeO 2 addition to produce a CeO 2 -ZrO 2 co-supporter were investigated through the water-gas shift (WGS) reaction. It was found that the WGS activity could be enhanced with CeO 2 addition. At relatively high temperature, Ni-loaded catalysts exhibited higher CO conversion while Cu-loaded catalysts demonstrated better performance at low temperatures. The stability and yield of the CO 2 and H 2 products of the Cu catalysts were higher than those of the Ni catalysts. These results may be caused by an irreversible adsorption of CO on Ni and the reverse WGS reaction occurring on the Ni catalysts. In situ diffuse-reflection infrared Fourier transform spectroscopy data suggests that the WGS mechanism likely proceeded via formate species. The water-gas shift reaction (WGS), as an alternative way to produce H 2 and convert poisonous CO into CO 2 , was carried out using Cu and Ni loaded onto CeO 2 -ZrO 2 as catalysts. The Ni-loaded catalysts exhibited higher CO conversion at high temperature while the Cu-loaded catalysts performed better at low temperature. The WGS reaction was found to occur via the formation of formate species.
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  • 69
    Publication Date: 2014-11-29
    Description: Power ultrasound is applied for cooling crystallization to control and modify the particle size and crystal habit of an active pharmaceutical ingredient, phenacetin. Operating parameters including sonication intensity and duration, solution concentration, and cooling rate are studied and compared. With respect to mean particle size, the effect of sonication intensity is most significant. In addition, the crystal habit of recrystallized phenacetin is modified substantially and shows an elliptic shape. Recrystallized phenacetin also provides an enhanced dissolution rate compared with the original sample. These results prove that ultrasonic crystallization is an efficient tool for controlling the solid-state properties of an active pharmaceutical ingredient. Ultrasonic crystallization is a promising process for controlling the different stages of crystallization. Cooling crystallization applying power ultrasound is adopted for recrystallization of a nonsteroidal anti-inflammatory drug, phenacetin. The mean particle size can be managed by adjusting sonication intensity and duration. Phenacetin crystals with a regular crystal habit and an elliptic shape are obtained.
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  • 70
    Publication Date: 2014-11-29
    Description: In a variety of reactions in the chemical industry, eggshell catalysts with a thin active layer are applied; they are often crushed for laboratory testing. The destruction of the shell can be avoided by a special reactor design. The presented advanced TEMKIN reactor is a further development of the reactor system for testing eggshell catalysts on the laboratory scale published by Temkin and Kul'kova in 1969. It is suitable for kinetic studies and for the detailed investigation of deactivation processes, as shown on the example of selective hydrogenation of acetylene. The advanced TEMKIN reactor is well suitable for testing of uncrushed industrial eggshell catalysts because of its defined flow pattern and excellent mass and heat transport properties. Because of its simple and robust design, all technical requirements are fulfilled for a fast, competitive, and accurate optimization of prototypes as well as already established catalysts for industrial applications.
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  • 71
    Publication Date: 2014-11-29
    Description: A bench-scale submerged membrane bioreactor (SMBR) was employed to treat vegetable oil plant wastewater with complete sludge retention. Treatment performance and membrane fouling of the SMBR were investigated. The system stably removed high amounts of total organic carbon, oil, and ammonia from vegetable oil wastewater and reduced the chemical oxygen demand, demonstrating the great potential of the SMBR in removing pollutants. The membrane fouling layer was not only governed by deposition of organic substances composed of extracellular polymeric substances like proteins, polysaccharides etc., and oil substances but also by inorganic elements. Organic foulants coupled to inorganic precipitation enhanced the formation of a gel layer and triggered severe membrane fouling in the SMBR. Treatment and disposal of vegetable oil wastewaters (VOWs) represents one of the principal problems for vegetable oil producing countries. A bench-scale submerged membrane bioreactor was applied to treat VOWs with complete sludge retention. Treatment performance and membrane fouling were investigated. The experimental results demonstrated the great potential of this membrane bioreactor in removing pollutants.
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  • 72
    Publication Date: 2014-11-29
    Description: Adsorption processes are frequently applied to separate traces of hazardous and toxic substances from gas streams. Hence, knowledge of sorption characteristics of these substances on standard adsorbents is essential. Sorption of hexanal and acetaldehyde from a nitrogen gas stream in trace concentrations on activated carbon and ordered mesoporous carbon-based adsorbents (CMK) is studied. A magnetic suspension balance and an attached gaschromatograph-mass spectrometer were used to analyze the sorption process both gravimetrically and spectrometrically. Both types of adsorbents show a higher capacity for hexanal than acetaldehyde. The activated carbon exhibits considerable differences in regard to desorption of hexanal compared to the mesoporous CMK. Information on sorption characteristics of hazardous substances is essential to design separation processes. Adsorption and desorption of the toxic acetaldehyde and the intensely odorous hexanal on activated carbon and periodic mesoporous carbon were studied. Magnetic suspension balances were used to analyze the sorption processes. Both adsorbents exhibit a higher capacity for hexanal than acetaldehyde.
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  • 73
    Publication Date: 2014-11-29
    Description: High-solids biomass slurries exhibit non-Newtonian behavior with a yield stress and require high power input for mixing. The goals were to determine the effect of scale and geometry on power number P 0 , and estimate the power for mixing a pretreated biomass slurry in a 3.8 million L hydrolysis reactor of conventional design. A lab-scale computational fluid dynamics model was validated against experimental data and then scaled up. A pitched-blade turbine and A310 hydrofoil were tested for various geometric arrangements. Flow was transitional; laminar and turbulence models resulted in equivalent P 0 which increased with scale. The ratio of impeller diameter to tank diameter affected P 0 for both impellers, but impeller clearance to tank diameter affected P 0 only for the A310. At least 2 MW is required to operate at this scale. High-solids biomass slurries are characterized by non-Newtonian behavior with a yield stress and high power input demand for mixing. A computational fluid dynamics model was developed to predict power requirements of non-Newtonian lignocellulosic slurry in an industrial-scale hydrolysis reactor with conventional mixing impellers. The lab-scale model was validated against experimental data and then scaled up.
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  • 74
    Publication Date: 2014-11-29
    Description: The effect of NaCl added in different quantities on thermodynamic properties, granulometric characteristics, and structure of glycine in a crystallization process was investigated. Solubilities of α - and γ -polymorphs in the presence of varying amounts of NaCl were analyzed. In order to examine the impact of the additive on granulometric properties of glycine, crystal morphology was examined by observing crystals under a scanning electron microscope. Crystal size distribution was determined by sieve analysis. By X-ray diffraction analysis, the critical concentration of NaCl at which the structure of glycine changed, could be defined. The purity of obtained polymorphs was confirmed by Fourier transform infrared spectroscopy. Interactions between additives and crystallizing phase influence crystallization processes. Batch-cooling crystallization of glycine with different amounts of added NaCl is described, causing changes in solubility, metastable zone width, supersaturation, final mass of crystals, granulometric properties, and structure. Process conditions for a conversion of α- into a γ- glycine structure are defined.
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  • 75
    Publication Date: 2014-11-29
    Description: Cryogenic air separation as the most important part of an integrated gasification combined cycle is a widely used operation unit for producing large quantities of high-purity oxygen and nitrogen. However, cryogenic distillation requires a large amount of energy due to the work needed to compress the air feed. An improved heat-integrated air separation column (HIASC) is proposed. The requirements of high-purity separation in the industrial cryogenic air separation process are achieved. An optimization model of the heat transfer coefficient ( UA ), a key parameter in column structure design and operation, is presented. The optimized UA value is obtained within the accepted value range reported in the international open literature, which ensures the practicability of the improved HIASC. An improved heat-integrated air separation column is proposed. With the new heat-integrated and thermally coupled structure, the pressure of the high-pressure column and the energy consumption decrease significantly compared with the conventional air separation column. The mathematic model and parameter analysis are presented. An optimization model for the heat transfer coefficient is proposed.
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  • 76
    Publication Date: 2014-11-29
    Description: Functional mesoporous Mo–SiO 2 materials were synthesized by a one-pot and facile room-temperature procedure, and characterized by X-ray diffraction, TEM, Raman spectroscopy, FT-IR, diffuse reflectance spectra, and BET analysis. The experimental results demonstrated that the mesoporous materials presented a high dispersion of molybdenum species and excellent catalytic activity for the removal of dibenzothiophene (DBT) without organic solvents as extractants. The catalytic performance on different sulfur-containing compounds was also investigated in detail. After recycling for eight times, the removal of the oxidation desulfurization system could still reach high values. GC-MS analysis detected the oxidation product of DBT. A mechanism was proposed for the absorptive oxidation process of sulfur compounds. The removal of sulfur compounds from petroleum is of utmost importance for stringent fuel specifications and environment pollution. Functional mesoporous Mo–SiO 2 materials were synthesized by a facile procedure and were characterized by a high dispersion of molybdenum species and excellent catalytic activity for the removal of dibenzothiophene under mild conditions without organic solvents as extractants.
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  • 77
    Publication Date: 2014-11-29
    Description: The level set method is combined with the concentration transformation method to solve the interphase mass transfer process. However, the artificial diffusion generated in the mass transfer convection term across the interface is inevitable, especially when large shape deformation is encountered at high Reynolds numbers. A semi-Lagrangian advection scheme is introduced to overcome this disadvantage. The methyl isobutyl ketone (MIBK)-acetic acid-water system is adopted to study the unsteady mass transport process accompanied with the Marangoni effect of a single deformable drop ascending in the infinite continuous phase. The predicted overall mass transfer coefficients agree with experimental data very well. The configuration of Marangoni convection is revealed and its effect on the interphase mass transfer process is investigated. The solute-induced Marangoni effect on an ascending drop driven by buoyancy is numerically simulated based on the level set method. The semi-Lagrangian convection scheme is introduced to eliminate the artificial diffusion. Compared with literature data, the present algorithm with the semi-Lagrangian convection scheme significantly suppressed the numerical diffusion and achieved much better predictions.
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  • 78
    Publication Date: 2014-11-29
    Description: The surface properties of solvent-based (SB) and water-based (WB) coatings and their impact on fouling during convective heat transfer of CaSO 4 solutions were investigated. Experiments demonstrated that the SB coatings had generally better non-adhesive characteristics, especially at higher values of the electron donor component since the deposits could easily be washed away. For the SB coatings, a longer induction period compared to those of untreated surfaces was observed and a significant reduction of the fouling rate could be achieved. Further analysis of surfaces revealed that SB coatings enhanced the acid-base repulsive force and thus reduced the deposit/solid adhesion energy. For the WB coatings, the Liftshitz-van der Waals attractive force plays a decisive role in the adhesion process due to the higher apolar component of the surface energy. Recent technological advances have given impetus in altering surface properties to mitigate fouling of heat transfer surfaces. The attempted coatings in this study demonstrated that they can extend the induction period of the fouling processes of CaSO 4 deposits by four times. This was but mostly due to their higher electron donor component of the surface energy compared to stainless-steel substrate.
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  • 79
    Publication Date: 2014-12-05
    Description: Ultrasonic hot embossing of polymers is an alternative to reduce fabrication costs of microreactors. An ultrasonic welding machine is used to melt a stack of thermoplastic foils and adapting them to a short-time milled aluminum mold showing the inversed design of the desired microfluidic cavities. Two micromixers were fabricated this way providing a low degree of axial dispersion and pressure loss. Stability analysis is successfully performed for a wide temperature range and high pressure. Mixing of colored aqueous solutions and neutralization reactions are implemented to both systems for defined volume flow rates and optically investigated via microscope. Reaction progress is automatically determined with a MATLAB script by reference to the consequential color change of the neutralization reaction with a color indicator. Typical mixing characteristics are identified for both mixers. Ultrasonic hot embossing of chemically resistant polymers as a simple and cost-effective fabrication method of microstructures and an optical analysis tool for tracing the progress of chemical reactions are introduced and evaluated. The simplicity of the fabrication method itself and good similarities of produced polymer micromixers with conventional ones made of other materials are pointed out.
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  • 80
    Publication Date: 2014-12-05
    Description: The existing screening and characterization systems for biocatalysts operate in batch mode, which could make catalyst selection and process development inaccurate when continuous operation mode is required in industry. A significant improvement of an innovative screening system based on miniaturized multiple membrane reactors formerly presented by the author is outlined, which enables continuous feeding of substrates and continuous removal of products. Although the presented screening system was originally designed for homogeneous enzymatic reactions, it can be used without further modifications for continuous catalysis with polymer-bound chemical catalysts or for quasi-homogeneous systems like reverse micelles. Currently available screening and characterization systems for biocatalysis are not sufficiently suitable for process description and scale-up of results to pilot- or full-scale reactors often operated in continuous mode. Hydrolysis of N -acetyl- L -methio-nine served as model reaction for an innovative continuous characterization system, implementing a precise dosing system.
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  • 81
    Publication Date: 2014-12-06
    Description: The synthesis of n -butyl levulinate, one of the most important biodiesel additives, by catalytic esterification of biomass-derived levulinic acid (LA) with n -butanol over modified H-ZSM-5 (micro/meso-HZ-5) in a closed-batch system is reported for the first time. The optimization of the reaction conditions such as the reactant molar ratio, the catalyst loading, the reaction time and the temperature was performed in view to maximize the yield of n -butyl levulinate. Micro/meso-HZ-5 was found to be the most efficient catalyst, with 98 % yield of n -butyl levulinate and a reusability for six cycles, which is higher than reported in the literature. A possible catalytic mechanism for the esterification reaction is also proposed. A second-order pseudo-homogeneous model with R 2  〉 0.97 confirmed that the esterification reaction is performed in the kinetic regime due to the high activation energy of 23.84 kJ mol −1 . The modified zeolite catalyst H-ZSM-5 (micro/meso-HZ-5) was used as heterogeneous acid catalyst in the esterification of renewable levulinic acid with n -butanol to produce n -butyl levulinate in a closed system. Micro/meso-HZ-5 turned out to be an efficient catalyst with 98 % yield of n -butyl levulinate and high reusability.
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  • 82
    Publication Date: 2011-05-06
    Description: A continuous countercurrent supercritical CO 2 extraction-distillation dual-column process was developed to extract and concentrate natural vitamin E (VE) from soybean oil deodorizer distillate (SODD). The experimental results demonstrated that process parameters such as extraction pressure, temperature, and solvent-to-feed ratio significantly impacted on the extraction efficiency of natural VE. A new five-parameter mass transfer model for the continuous countercurrent supercritical CO 2 extraction-distillation dual-column process was presented based on the Penetration and Double-Film theories. The calculated values of the mathematical model agreed well with the experimental data, with absolute average relative deviation values of less than 25 %. A continuous countercurrent supercritical CO 2 extraction-distillation dual-column process was developed to extract and concentrate natural vitamin E from soybean oil deodorizer distillate. A new five-parameter mass transfer model for this process was presented based on the Penetration and Double-Film theories.
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  • 83
    Publication Date: 2011-05-06
    Description: The effect of Ca(NO 3 ) 2 ·4H 2 O and (NH 4 ) 2 HPO 4 primary solutions as the starting materials in the synthesis of a calcium phosphate phase was examined. Therefore, wet chemical reactions were investigated in solution at different temperatures by hydrothermal conditions aimed at hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HAp) synthesis. The powders were investigated by XRD, SEM, FE-TEM, HRTEM, EDAX, SAED, and FTIR. It is found that the HAp have diameters of 25–50 nm and lengths of 120�30 nm with different morphologies. As a matter of fact, the hydrothermal method guarantees the production of HAp for different applications. Hydroxyapatite (HAp) is the major component of natural bone minerals. Nanorod HAp with a good crystallinity was developed by a hydrothermal method. The nanorods have a high degree of crystallinity and are uniformly structured. These high-quality HAp nanorods represent a well-defined nanoscale structure needed for both fundamental studies and clinical applications.
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  • 84
    Publication Date: 2011-05-06
    Description: The residence time distribution (RTD) in a parallel-plate channel with staggered fins for both steady and pulsed flow conditions was experimentally determined. Dispersion and tank-in-series models were also adopted to characterize the system. The process fluid was water and the experiments were performed at room temperature. A steady Reynolds number Re ranging from 100 to 1000 was studied. The pulsating flow was generated using a frequency f of 6–20 Hz and an amplitude A of 0–2.3 mm. A pulse injection of sodium chloride solution was used as a tracer and the response in the form of electrical conductivity was measured at the outlet stream. The flow in the staggered finned channel approaches nearly plug-flow behavior with either higher steady-flow velocity or superposition of oscillation at low Re. Residence time distribution (RTD) in a parallel-plate channel with staggered fins for both steady and pulsed flow conditions has been studied. The flow in the staggered finned channel approaches nearly plug-flow behavior with either higher steady flow velocity or superposition of oscillation at moderately low Reynolds number.
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  • 85
    Publication Date: 2011-05-06
    Description: A new non-invasive visualization technology was successfully developed to determine the hydrodynamics parameters of Taylor flow in monolith channels. With the developed method, the gas and liquid slug lengths as well as the gas holdup in channels of different radial positions were measured. Accordingly, the average gas holdup in different radial zones and the mean slug lengths over the monolith cross-section were calculated with varying superficial gas and liquid velocities. By defining the maldistribution factor, the degree of non-uniform distributions of these parameters over the monolith cross-section was investigated quantitatively. The results showed that a moderate gas-to-liquid velocity ratio can result in uniform distribution for both gas holdup and slug lengths. In addition, the obtained mean slug lengths were well correlated with simplified Qian and Lawal correlations. A new non-invasive visualization technology was successfully developed. The gas and liquid slug lengths and the gas holdup in channels at different radial positions of a monolith were obtained by analyzing bubble images captured at the monolith outlet region. The maldistributions of the gas holdup and slug lengths were investigated. The mean gas and liquid slug lengths were well correlated with simplified correlations from literature.
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  • 86
    Publication Date: 2011-05-06
    Description: Rutile titanium dioxide (TiO 2 ) white pigment is prepared by a novel NaOH molten-salt process. Titanium slag is decomposited by NaOH molten salt to obtain sodium titanate which is then converted into hydrate titanium dioxide (H 2 TiO 3 ) through acid dissolution and hydrolysis. Finally, TiO 2 white pigment is prepared by H 2 TiO 3 doping and calcinations. H 2 TiO 3 prepared by this innovative method is characterized and the influencing factors of doping and calcination of H 2 TiO 3 on pigmentary properties of TiO 2 are investigated. H 2 TiO 3 with certain characteristics could be prepared through the controlled hydrolysis step in the NaOH molten-salt process. Good pigmentary properties of rutile TiO 2 white pigment are achieved by doping with suitable amounts of K 2 O, P 2 O 5 , Al 2 O 3 , and rutile nuclei, thereby approaching the quality of the commercial TiO 2 pigment standards. The preparation of rutile TiO 2 white pigment by means of a novel NaOH molten-salt process is demonstrated. Color performance was improved by the addition of K 2 O, P 2 O 5 , Al 2 O 3 , and rutile nuclei. The improved color performance of rutile TiO 2 white pigment approaches the quality of commercial TiO 2 pigment standards.
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  • 87
    Publication Date: 2011-04-03
    Description: The influence of magnetic field intensity and process parameters on the transient fluidization behaviors of magnetically stable fluidized beds (MSFBs) was studied. The local solid holdup distribution and magnetically stabilized regimes were carried out by experimental measurements in MSFBs. The scaling approach for MSFB hydrodynamics based on magnetic field and dynamic similitude with a limited number of dimensionless groups was tested. A dimensionless number for magnetic field has been developed. An experimental criterion for the magnetically stabilized fluidization is established based on random analysis of the void fluctuation signal. It includes two characteristic parameters of the main frequency of voidage fluctuation signals, i.e., the self-correlation function and variance. A dimensionless correlation to calculate the stable zone with three dimensionless groups of Er, Ar, and Re was proposed using dimensionless analysis. The influence of magnetic field intensity and process parameters on the transient fluidization behaviors of magnetically stable fluidized beds was investigated. A dimensionless correlation to calculate the stable zone with the three dimensionless groups, i.e., Archimedes number, Reynolds number, and ratio of magnetic potential and gravity potential energy, is proposed.
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  • 88
    Publication Date: 2011-04-05
    Description: Hydrodesulfurization (HDS) of dibenzothiophene in a batch reactor was performed at 5.5 MPa and 320 °C on CoMoS/Al 2 O 3 -TiO 2 using trans -1,2-cyclohexanediamine- N,N,N′,N′ -tetraacetic acid (CYDTA) as a complexing agent for the preparation method. The effects of titania, concentration of CYDTA, and preparation procedure were investigated by using X-ray diffraction, BET, Fourier transform infrared spectroscopy, and temperature-programmed desorption of ammonia experiments. The catalyst prepared by impregnation with γ -alumina and titanium isopropoxide as raw materials and a CYDTA/Co mole ratio of 1.2 provided an HDS activity (on a pseudo-first-order kinetic constant basis) value ∼3.8 times higher compared to that of a CoMo/Al 2 O 3 catalyst. Hydrodesulfurization (HDS) of dibenzothiophene in a batch reactor was performed on CoMoS/Al 2 O 3 -TiO 2 using trans -1,2-cyclohexanediamine- N,N,N′,N′ -tetraacetic acid (CYDTA). Combining alumina-titania mixed supports, an appropriate catalyst preparation, and the optimum proportion of CYDTA in the catalyst network led to a new catalyst for the HDS reaction.
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  • 89
    Publication Date: 2011-08-04
    Description: Evaporators used in power plants for sugar production are vessels with two boxes of heat exchangers. These heat exchangers made of a low-corrosion resistance material are frequently replaced during the alcohol production process. In view of the growing production of cane, sugar, and alcohol, and the corrosion of materials used in power plants, it was necessary to find alternative materials for carbon steel applied in the evaporators. A comparative study of the corrosion resistance of stainless steel as well as unalloyed and alloyed carbon-manganese steels in neutral and acid sugar cane juice electrolytes is presented. The alloyed carbon steels showed the best corrosion behavior in an acid environment compared to a neutral medium. Among the alloyed carbon steels, ASTM T11 and ASTM T22 steels provided the highest corrosion resistance in sugar cane juice. The corrosion resistance of stainless steel as well as unalloyed and alloyed carbon-manganese steels in neutral and acid sugar cane juice electrolytes was determined. The alloyed carbon steels presented the best corrosion behavior in an acid environment compared to a neutral medium. Among the alloyed carbon steels, ASTM T11 and ASTM T22 steels provided the highest corrosion resistance in sugar cane juice.
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  • 90
    Publication Date: 2011-08-04
    Description: Cyclopentadiene and isoprene are produced in large quantities by the steam cracking of naphtha and gas oils to produce ethylene. At room temperature, cyclopentadiene slowly dimerizes in a Diels-Alder reaction to give dicyclopentadiene. This work presents a new method for accelerating the Diels-Alder reaction in the presence of ultrasonic irradiation under ambient conditions. The effects of various reaction conditions such as ultrasonic reaction time and reaction temperature on cyclopentadiene dimerization and oligomerization of cyclopentadiene and isoprene were investigated. The results showed that the two reactions could be significantly enhanced by ultrasonic irradiation. The kinetic results revealed that the introduction of ultrasonic irradiation lowered the activation energy of both reactions, but not to the same degree. The increased difference in activation energy between the two reactions is the driving force to produce more dicyclopentadiene in the presence of ultrasonic irradiation. Cyclopentadiene and isoprene are produced in large quantities by the steam cracking of naphtha and gas oils to produce ethylene. At room temperature, cyclopentadiene slowly dimerizes in a reversible Diels-Alder reaction to form dicyclopentadiene. A new method is presented for accelerating the Diels-Alder reaction in the presence of ultrasonic irradiation under ambient conditions.
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  • 91
    Publication Date: 2011-08-09
    Description: The addition of surfactants can influence extraction processes. In cases where the surfactant concentration is above the critical micelle concentration, the mass transfer rate increases due to the formation of inverse micelles and, thus, through the mechanism of micellar extraction of zinc. The influence of the added surfactant cetyltrimethylammonium bromide on zinc extraction with the cation exchanger di(2-ethylhexyl)phosphoric acid was analyzed based on extraction equilibrium and mass transfer experiments. The observed experimental results are explained phenomenologically. Improvements of metal extraction with regard to selectivity and output can be achieved by using surfactants. Addition of the surfactant cetyltrimethylammonium bromide can influence the mass transfer of zinc by the formation of micelles and inverse micelles. The advantages of the proposed micellar extraction are faster extraction of zinc and higher potential loadings of the organic extract phase.
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  • 92
    Publication Date: 2011-08-09
    Description: The key challenge in amine-based CO 2 capture from flue gases is to reduce the energy consumption required for solvent regeneration. Lipophilic amines exhibit a thermomorphic phase transition upon heating, giving rise to autoextractive behavior, which intensifies desorption at temperatures well below the boiling point of aqueous solutions. The low regeneration temperature of less than 80 °C together with the high cyclic CO 2 loading capacity of ∼0.9 mol  mol absorbent –1 of such thermomorphic biphasic solvent (TBS) systems permit the use of low-value and even waste heat at temperatures below 100 °C for desorption. In order to reduce the exergy demands still further, techniques for enhancing CO 2 release using extractive regeneration with inert solvent addition were investigated at temperatures of 40–50 °C to permit the use of waste heat at temperatures of ∼70 °C or less. The regeneration of 3 M absorbed lipophilic amine solutions with 0.93 mol mol –1 CO 2 loading by using various additional solvents and the evaluation of the extractive performance in multiple-stage crosscurrent and countercurrent configurations indicated the promise of adding certain hydrophobic solvents to enhance the low-temperature regeneration of TBS absorbents. Thermomorphic biphasic amine absorbents perform high loading capacity, good reactivity, excellent regenerability, and low regeneration temperature for CO 2 capture. Extractive regeneration using inert hydrophobic solvents can reduce the desorption temperature to 40–50 °C, thus enabling the use of waste heat for regeneration and facilitating thermal integration of CO 2 capture into the remaining process.
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  • 93
    Publication Date: 2011-08-09
    Description: The composite of carboxymethyl-modified β-cyclodextrin-intercalated ZnAl-layered double hydroxide (CMCD-LDH) was investigated for selective adsorption of phenol (Ph) and nitrobenzene (NB). The Freundlich model can be used to describe satisfactorily the adsorption isotherms of Ph and NB. The adsorption capacity of CMCD-LDH for Ph and NB increases with the increase of temperature, indicating the endothermic nature of this sorption process. CMCD-LDH exhibits preferential adsorption for Ph over NB at pH 6.5 due to the selective recognition of the interlayer CMCD cavity. Pseudo-first-order and pseudo-second-order kinetic models were applied to simulate the kinetics of the adsorption process. The calculated q e values based on the pseudo-second-order model are much closer to the experimental data q e,exp . As a result, the pseudo-second-order kinetic model is more reasonable to describe the adsorption process of Ph and NB onto the CMCD-LDH composite. CMCD-LDH can be potentially applied in selective adsorption and separation of wastewater pollutants. The composite of carboxymethyl-modified β-cyclodextrin-intercalated ZnAl-layered double hydroxide (CMCD-LDH) was investigated for selective adsorption of phenol (Ph) and nitrobenzene (NB). It displays preferable adsorption for Ph when Ph and NB are in a competitive environment and can be regarded as a potential adsorbent for selective separation of neutral aromatic pollutants in wastewater.
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  • 94
    Publication Date: 2011-08-09
    Description: A batch system is an inherently parametric sensitivity system where small changes of input parameters can induce large changes of output variables. In the present work, temperature and temperature sensitivity with respect to the initial temperature were investigated by parametric sensitivity analysis using a dimensionless batch reactor model. The influence of the Semenov number, the heat of reaction parameter and the Arrhenius-type number on reactor temperature and temperature sensitivity were studied. It is demonstrated that batch reactors can exhibit high sensitivity when small changes in input parameters lead to large changes in temperature and temperature sensitivity trajectories. A criterion is established for thermal runaway by analyzing temperature sensitivity trajectories and applied to some experimental examples. This criterion allows runaway and safe conditions to be identified, the results being in agreement with the experimental data. The proposed criterion can satisfactorily predict the safety limits of the operating conditions. Increasing attention has been paid to thermally safe operation of chemical reactors to avoid runaway accidents. A new and simple sensitivity-based criterion was developed for thermal runaway in batch reactors by analyzing temperature sensitivity trajectories and applied to experimental examples. The proposed criterion has proved to be very effective in predicting the critical conditions of thermal runaway.
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  • 95
    Publication Date: 2011-05-31
    Description: The reactive extractions of formic acid with tri- n -octylamine (TOA) dissolved in three solvents with different dielectric constants (dichloromethane, butyl acetate, n -heptane) without and with 1-octanol as phase modifier were comparatively analyzed. The results indicated that the mechanism of the interfacial reaction between acid and extractant (Q) is controlled by the organic phase polarity. In the absence of 1-octanol, the structures of the extracted complexes are (HA) 2 Q 2 for dichloromethane and butyl acetate, and (HA) 2 Q 4 for n -heptane. These structures are modified by adding 1-octanol and become (HA) 2 Q for extraction in dichloromethane or butyl acetate, and (HA) 2 Q 2 for extraction in n -heptane. Although the presence of 1-octanol improves the extraction efficiency, it leads to a reduction of the extraction constants for all considered solvents, an influence that is more significant for n -heptane. The study is an original approach of the reactive extraction of formic acid with tri- n -octylamine from the viewpoint of the extraction efficiency and mechanism, using solvents with different polarity (dichloromethane, butyl acetate, n -heptane). The effect of 1-octanol addition on the extraction efficiency and the mechanism was analyzed. The structures of the extracted compounds formed by the interfacial reaction between formic acid and amine were established.
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  • 96
    Publication Date: 2011-05-31
    Description: The spraying system is responsible for the particle formation and spray pattern. The most important features of sprays emerging from different atomizers are discussed. In the case of pneumatic atomizers the entrainment is low and a well-mixed jet with little segregation of fine and large particles occurs. A much stronger interaction of gas and spray takes place in the case of large spray angles as, e.g., produced by rotary atomizers. To some extent the particle morphology is known to depend on the drying speed and thus on the entrainment. The dependency of the quality and morphology of spray-dried products on the spray method is discussed. The generated liquid drops possess varying sizes and, therefore, are subject to different drying histories, finally resulting in products distributed in quality. The most important features of sprays emerging from different atomizers are reviewed.
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  • 97
    Publication Date: 2011-05-31
    Description: Fluidized-bed spray granulation is used to produce porous granular particles from suspensions, solutions, and melts. In this work, the adapted two-fluid model approach is used to simulate the fluid dynamics in the fluidized bed, and a simplified direct quadrature method of moments is adopted to mimic the full particle size distribution. The size-dependent growth kinetics is obtained by computational fluid dynamics simulation for short process times from the modeling of drop deposition on the particles. This kinetics is used in the population balance equation to predict the evolution of the full particle size distribution for long process times. Such a multiscale approach allows for a description of continuous granulation processes. In this investigation, a coupled computational fluid dynamics (CFD) and population balance equation (PBE) approach is used to simulate the growth of polydisperse particles in a fluidized-bed spray granulation process. The growth kinetics is used in the PBE to solve the development of the particle size distribution for a long process time without considering the fluid dynamics.
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  • 98
    Publication Date: 2011-05-31
    Description: Various types of fluidized bed equipments used in granulation were experimentally investigated in order to gain a more detailed insight in particle recirculation behavior and particle residence times in the two considered compartments, namely the spray compartment and the drying compartment. The investigated fluidized bed technologies comprise a top-spray process, a spout fluidized bed without and with internal riser, and a spouted bed. The measurements were conducted by using image analysis techniques on an almost 2D particle flow. From the results, conclusions about particle wetting and drying can be extracted, subject to fluidization velocity, nozzle mass flow rate, and facility/riser construction. An innovative approach for investigating various fluidized bed granulation equipments by applying two coupled image analyzing techniques is presented. State-of-the-art measurement techniques of particle image velocimetry in combination with a new algorithm of particle volume fraction determination are employed to experimentally identify local particle residence times in an unprecedented manner.
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  • 99
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    Wiley
    Publication Date: 2011-06-01
    Description: Turnkey plant for the production of high-quality vacuum gas oils. Copyright: ThyssenKrupp AG
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  • 100
    Publication Date: 2011-06-01
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