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  • Industrial Chemistry and Chemical Engineering  (658)
  • Wiley-Blackwell  (658)
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  • 1
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The variation in the behaviour of bulk solids as a result of sudden pressure changes in the surrounding gas phase is of interest in the application of lock hoppers for transfer of bulk solids into pressure vessels. By using such sluice systems, problems occur due to consolidation of the pressurized bulk solids. This paper presents the results of experimental and theoretical research, which allow to describe the influence of several parameters on pressure compensation and the degree of consolidation. With reference to the forces and mechanisms responsible for consolidation, it is possible to describe the different consolidation behaviour of incompressible (limestone) and compressible (hard coal) bulk solids.
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  • 2
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    Chemical Engineering & Technology - CET 14 (1991), S. 65-72 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A study was made of the flow characteristics of large oscillating drops of pure liquid-liquid systems, using a thermostatically-controlled, rising drop column, 50 mm in diameter and 1000 mm in length. Mirrors in the jacket enabled front and side views of drops to be photographed simultaneously. Single drops in the size range 5-10 mm were investigated with both mutually-saturated phases and when the solute was being transferred from the dispersed phase. The systems studied were (1) toluene and acetone (dispersed)-water (continuous), and (2) n-heptane and acetone (dispersed)-water (continuous). Acetone concentrations were varied up to 3.75 kmol/m3. The oscillations of a travelling drop were asymmetrical; therefore, the amplitude cannot be expressed accurately in terms of only two axes. The area change of the drop compared to that of a sphere of equal volume ‘ε’, was shown to represent the amplitude accurately. The periods of droplet oscillation were uniform for the mutually saturated systems of constant physical and flow properties but changed when mass transfer was taking place. The interfacial tension exerted a marked effect on the amplitude, which also depended upon the oscillation frequency. The amplitude changed with droplet size in a similar manner to the terminal velocity, i.e. it increased with increasing size until it reached a maximum, subsequently decreasing less rapidly. The drag coefficient increased with increasing rate of mass transfer from the drop. Correlation of the results and the area eccentricity ‘ε’ by dimensional analysis embracing all possible parameters and physical properties affecting drop oscillation, resulted in the correlation ε = 0.22 Sr0.42 We-0.53 M0.13 with a mean deviation of ± 14%. This will facilitate more accurate prediction of the interfacial area for mass transfer calculations, relating to equipment containing droplets in the oscillating regime.
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  • 3
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 14 (1991), S. 113-117 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The reduction of nitric oxide with ammonia on iron oxide catalysts has been studied in a continuous-flow recycle reactor using simulated flue gas in the temperature range from 573 to 673 K. NO and HN3 concentrations were varied between 0 and 1000 vpm, O2 and H2O concentrations between 0 and 9 vol.-%, the remainder being nitrogen. In the presence of oxygen, the formulated reaction rate equation describes the measured rates of the main reaction NO + 2/3 NH3 ⇄ 5/6 N2 + H2O. Its form corresponds to the Langmuir-Hinshelwood type. The rate equation well fits the data, which cover the whole industrial temperature and concentration range. In the absence of oxygen, the measured reaction rates can be best described by a power law.
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  • 4
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new transport system has been developed which combines vibration of the conveying pipe with amplitudes of the order of fractions of a millimetre with rather low superficial velocities of the carrier gas. This new system was specially designed for gentle transport of fragile particulate materials.
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  • 5
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    Chemical Engineering & Technology - CET 14 (1991), S. 147-161 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this study, we investigated the limits of safe operation for a cooled reactor, operated batchwise. As an example of a single-phase reaction, we studied the decomposition of t-butyl peroxypivalate, a well-known organic peroxide, undergoing self-heating at relatively low temperatures. If sufficiently diluted, it can be supplied to a polymerization process from large, cooled but unstirred vessels. We present a number of extensions to the existing homogeneous explosion theory, namely a practical definition of the critical condition, its calculation, and expressions for the available time before runaway in the case of a supercritical condition, taking into account the effects of natural convection inside the vessel and the reactant conversion. The extensions of the theory were confirmed by adiabatic and non-adiabatic runaway experiments on bench scale, and natural convection cooling experiments with liquids in various packages.
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  • 6
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This contribution deals with the consequences of the decrease in diffusion coefficients at the boundaries of miscibility in fluid systems and its effect on the mechanisms of mass transfer. The liquid-liquid (1-1) extraction involving several components is taken as an example for the discussion of this topic. A short review of Hampe's theory on transport mechanisms in the transition regions of interfaces [1] explains the intrinsic interdependence between mass and momentum transfer. Finally, a discussion of the peculiarities of resistances to mass transfer in boundary layers, based on the changes in molecular transport properties, is presented.
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  • 7
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    Chemical Engineering & Technology - CET 14 (1991), S. 200-208 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The catalytic properties of wide-pore zeolites, namely Ni- and Cu-doped faujastie H-Y and H-mordenite (H-M) are compared on the example of conversion of n-hexane. After thermal pretreatment of ion-exchanged zeolites, reduction with hydrogen (PH2 ≤ 40 bar) leads to a large number of metallic clusters and crystallites as well as ionic species in the zeolites. Notwithstanding this variety, the different types of catalysts can be divided into three classes: classical bifunctional catalysts (for example NiHM, NiHY) with ion exchange degrees 〉 30%, monofunctional catalysts, such as CuHM and CuHY with high copper contents (ion exchange degree 〉 40%) and metal-doped (Ni and Cu) zeolites which, depending on the conditions of pretreatment, act as bifunctional and/or monofunctional compounds and, therefore, show very unstable reaction behaviour. In addition to the extent of reduction, the cation distribution affects the activity and deactivation behaviour and, to a lesser extent, the product selectivity. The reaction mechanism of bifunctional catalysis is similar to that observed in platinum-doped catalysts, while the mechanism of monofunctional catalysis resembles the process on undoped zeolites.
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  • 8
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This work investigates the thermodynamically based assumption that diffusion at binodal states of unstable fluid systems vanishes. It is shown experimentally that a scaling law, which describes the fall in diffusion near critical points, may also be applied in an extended form to its abatement at the limits of solubility. These results may profoundly affect the modelling of mass transfer between phases whose bulks exhibit states of saturation.
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  • 9
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    Chemical Engineering & Technology - CET 14 (1991), S. 240-247 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A systematic method of controller design is introduced to determine the overall charcteristic behaviour developed on process pole removal. The time delay compensation is automatically incorporated in the proposed control law. The implemented tuning parameters in the law are confined to the range between 0 and 1 to guarantee the stability of the overall control system. Subsequently, the fixed and adaptive control strategies are implemented to simulate a batch PVC reaction system. The adaptive control scheme provides good, roubust control of this simulated reactor notwithstanding the wide range of operating conditions and non-linear dynamics of the system. However, the fixed control scheme performs well only for a noise-free system. In addition, two limiting control laws, derived from the proposed method, are also used to simulate the reactor. The results indicate that these laws are not suitable for this non-linear reaction system.
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  • 10
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article describes the effects which occur during three-component mass transfer in liquid-liquid extraction between saturated and undersaturated phases of the system glycerol-acetone-water. The description is based on experiments in a countercurrent spray column. The physical modelling starts with the balance equations of phase flows, taking into account the variation of concentrations and mass flow rates along the column axis as well as backmixing effects. In addition, recent findings on the mechanisms of mass transfer in saturated and undersaturated phasses, deduced from theoretical and experimental results, were used to formulate mass transfer coefficients. These are valid for the region near the interface of drops in a fluid and are inserted into the balance equations. A comparison between experiments and calculations of the observed phenomena is presented.
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  • 11
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    Chemical Engineering & Technology - CET 14 (1991), S. 275-287 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Those chemical and photochemical characteristics of a photochromic system which are necessary for successful application to flow visualization studies in water are identified. The properties of a number of photochromic and photosensitive systems are discussed, and critically examined, with regard to these requirements.
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  • 12
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This contribution demonstrates the possibility of using a thermodynamic description of electrolyte solutions directly for computer simulation of distillation columns. Coefficients are determined for a combination of a solvation model with a local composition equation for the activity coefficient. The use of one set of coefficients yields good results of calculation of vapour pressure, vapour phase composition and caloric data of hydrochloric acid. Solution of material and heat balance equations of distillation columns is achieved on an IBM PC with the above description. Two illustrative examples of an absorption and a rectification calculation are presented
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  • 13
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The knowledge of multicomponent adsorption equilibria is of great importance for the industrial design and application of adsorptive purification and separation processes. As the experimental determination of the required data is time-consuming and costly, theoretical help is desirable. This contribution presents and assesses the most common theoretical approaches to the calculation of multicomponent adsorption equilibria. The models are based on the assumption of an adsorbed solution, extension of the volume filling of micropores theory or statistical thermodynamics. These models are applied to different adsorptive/adsorbent systems with ideal and non-ideal equilibrium behaviour. It is established that, at low coverages of adsorbent surfaces, all theories provide good estimates of the adsorbed phase composition and total loading while, at high saturations, no model is completely satisfactory.
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  • 14
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    Chemical Engineering & Technology - CET 14 (1991), S. 347-352 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simplified model has been developed to describe ammonia stripping process in spray towers. The effect of various operating parameters including air flow rate, contact time, droplet size, liquid to gas ratios and tower height on the performance of such systems has been studied in detail. The results obtained for ammonia stripping have been compared with the limited experimental data available in literature. The predicted results agree reasonably well with the reported experimental data.
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  • 15
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    Chemical Engineering & Technology - CET 14 (1991), S. 357-362 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of particle size (layer thickness), BET surface area and pore size distribution on the reactivity of CaO derived from limestone were studied by using a pH-stat and the BET method. Visual analysis was obtained with SEM, and X-ray diffraction was used to determine the crystalline components present. It was found that the pore size distribution, including pore volume and pore surface distribution, affected the sulphatization behaviour. The larger pores (D 〉 50 Å) with their pore volume and pore surface were to some extent responsible for both initial reactivity and ultimate capacity of CaO.
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  • 16
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    Chemical Engineering & Technology - CET 14 (1991), S. 376-378 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Activity coefficients of hydrocarbons and chloroparaffins at infinite dilution in methyl phenyl ether, butyl ether and methyl iso-butyl ketone at 293.15 K have been obtained by the retention-time method in a modified gas chromatograph. The experimental data are compared with predictions of the UNIFAC and MOSCED models. Selectivities for the 1,1,1-trichloroetane-1,2-dichloroetane separation process are reported.
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  • 17
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A semi-empirical gas-liquid equilibrium model for the absorption of CO2 in aqueous 3M AMP (2-amino-2-methyl-1-propanol) is presented. It applies to high CO2 loadings (y 〉 0.5) in the temperature range between 20 and 50 °C, and is based on experimental solubility and pH determinations. For a given amine concentration, it yields the equilibrium partial pressure of CO2 as a function of only two variables: the CO2 loading and temperature. The model correlates the expressions for the chemical equilibria involved as follows: pCO2 = m y × 10x, where pCO2 is the equilibrium partial pressure, x = logK - pH, m is the amine molarity, y the CO2 loading, and K is a parameter involving Henry's law constant, H, and the first dissociation constant, K1, of carbonic acid. pH is found to depend on both temperature and CO2 loading while logK depends only on the CO2 loadIng. Correlations for pH and logK are presented. The model fits own data for 3M AMP very well as well as the equilibrium data found in recent literature.
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  • 18
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    Chemical Engineering & Technology - CET 15 (1992), S. 91-98 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The transport of corrosive liquids containing solids, in conventional energy and process technology as, for example, in oil and gas production, places high demands on the selection of materials for plant construction. A discussion on the chemo-mechanical load demonstrates the significance of hydrodynamics in selecting the test method. Choosing a pipe with an abrupt expansion of cross-section as a flow model yields a new method of simulating operation conditions. By subjecting ferrous materials used for hydraulic machinery to representative media from three important industries, a broad spectrum of results can be obtained. Classification of the results leads to four basic types of mass loss behaviour in materials as functions of flow rate. These findings yield guidelines for the selection of materials and the dimensioning of flow equipment.
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  • 19
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    Chemical Engineering & Technology - CET 15 (1992), S. 124-130 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The adsorption of p-nitrophenol (PNP) from an NaOH, H3PO4-buffered, aqueous solution on activated carbon was studied at pH 2, 7, and 8.5. Comparative studies were then carried out on ozonized carbon and ozonized PNP solution. In the latter case, PNP adsorption was performed from an ozonized solution, and also after exposing the activated carbon to the ozonized PNP solution for 24 h. At acid pH, PNP adsorption was found to be markedly higher than at neutral and weakly basic pH's. Ozonization of carbon affects the results only at pH 7 and 8.5. Ozonization of PNP led to a small decrease in adsorption, irrespective of the method of contect between carbon and ozonization reaction products. The rate was faster at acid than at basic pH, and the ozonization speeded up the adsorption slightly but only at pH 8.5. Application of a mathematical model indicated that mass transfer in bulk solution controls the rate of adsorption.
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  • 20
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    Chemical Engineering & Technology - CET 15 (1992), S. 162-167 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new model is derived to establish the effective nucleation rate in terms of the MSMPR-theory. The model is based on the concept of two-step crystal growth, secondary nucleation, nuclei activation and metastable supersaturation. A comparison between model prdictions and experimental data from different crystallizers is presented. This model, which integrates hydrodynamics directly into its theory, proves to be extremely suitable for describing the MSMPR-crystallization process.
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  • 21
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    Chemical Engineering & Technology - CET 15 (1992), S. 193-201 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A laboratory fixed-bed reaction column is presented, in which a heterogeneouslyl catalyzed reversible fluid-phase reaction and the separation of the reaction product from unreacted or inert components by distillation are performed simultaneously. The rection studied, the formation of methyl tertiary butyl ether (MTBE) from methanol and isobutylene, is catalyzed by strongly acidic macroreticular ion exchange resins. Packing elements are Raschig rings, manufactured for the first time from the above-mentioned ion exchange resins. This in-house made catalyst shows practically the same ion exchange capacity as the commercial products. The control system installed in the equipment is capable of correcting strong disturbances os the steady state. As shown by expwrimental results, the superimposed distillation process occurs in such a way that the chemical equilibrium of the MTBE synthesis does not limit isobutylene conversion.
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  • 22
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    Chemical Engineering & Technology - CET 16 (1993), S. 24-25 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Measurements of surface tension of flame-, plasma- and UV-treated PP-EPDM samples show that all three methods of pretreatment significantly increase the surface tension. The flame or plasma pretreatment increases especially the polar element of surface tension while the UV-treatment enhances the disperse element. The measurements were carried out with a new fully automatic unit for determining contact angles (AURAM).
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  • 23
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    Chemical Engineering & Technology - CET 16 (1993), S. 35-39 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental data are reported for ion exchange equilibria of binary systems on Amberlite IR-120 resin, at different temperatures and total ionic concentrations in aqueous solutions. These systems exhibit non-ideal behaviour in both phases, and the equilibrium characterization has been based on the law of mass action, using Wilson and Meisssner, and Kusik equations to correlate the activity coefficients in the resin and aqueous solutions, respectively. Equilibrium constants, standard thermodynamic properties (Gibbs free enthalpy changes, enthalpy and entropy) and Wilson binary parameters were obtained as functions of temperature.
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  • 24
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    Chemical Engineering & Technology - CET 16 (1993) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 25
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    Chemical Engineering & Technology - CET 16 (1993), S. 62-67 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of methane oxidative coupling (OCM) was studied using 1 g of Na-Mn2O3 catalyst at 1073 to 1123 K, in an integral flow reactor (I.d. = 10 mm), at atmospheric pressure with methane and oxygen partial pressures of 0.27 and 0.13 bar, respectively, so that the ratio of CH4 to O2 was 2. The flow rate range was 50 to 200 ml/min. the kinetic data were analyzed by the Rideal-redox type of rate equation assuming the methyl radical and active surface oxygen to be the steady-state intermediates. Oxidation and reduction rate constants (Kox, Kred) for methane consumption were calculated from experimental catalysis results by computer simulation using the multiple least squares method. The activation energies at rate constants Kox and Kred for this type of catalyst were reported as 43.26 and 62.2 kcal/mol, respectively.
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  • 26
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    Chemical Engineering & Technology - CET 15 (1992), S. 69-81 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The photochemical reaction SiHCl3+Cl2→SiCl4+HCl is of industrial importance in the production of pure silicon for the semiconductor industry. The present paper deals with an experimental investigation of the kinetics of this purification step. The main reaction occurs in the liquid phase and is initiated by light. In this gas-liquid reaction system, all components, which are present in both phases, were analyzed by gas chromatography. Reaction progress was monitored by recording the pressure rise. Apart from the influence of wavelength and radiation intensity on the above photoreaction, reactions in the absence of light and on the wall were also investigated.
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  • 27
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    Chemical Engineering & Technology - CET 15 (1992), S. 114-118 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A bubble column absorber was used to investigate kinetics of the reaction between carbon dioxide and aqueous solutions of diisopropanolamine (DIPA), by means of gas absorption experiments. These were conducted in the temperature range of 20 to 40°C, with DIPA concentrations from 5 to 500 mol/m3, and CO2 partial pressures between 5 and 101 kPa. A model based on the Danckwerts' surface reneval theory was used to analyze the experimental results and to determine the rate constant. The obtained data support the assumption of a second-order overall reaction, with the rate constants being well correlated by the Arrhenius equation: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_2 = 1.112 \times 10^{10} \exp \left({ - {{4848} \mathord{\left/ {\vphantom {{4848} T}} \right. \kern-\nulldelimiterspace} T}} \right).$$\end{document}
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  • 28
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    Chemical Engineering & Technology - CET 16 (1993), S. 130-146 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new set of rate equations for gas desorption has been derived from the laws of thermodynamics and motion and the kinetic theory of gases. The equations assume that gas desorption or absorption originally represents an isothermal change at the interface, similarly to condensation or vaporization. The mass transfer in gas desorption or absorption is initially caused by external work being done on the system and takes place as work done by the system which instantly develops a concentration gradient, increases in internal energy and temperature, and a deviation from the ideal gas behaviour inside MTZ in the process of mass transfer. After cessation of external work, these conditions disappear following the transfer of a small residual mass at a constant velocity and a decrease in internal energy inside the MTZ.
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  • 29
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Theoretical and experimental investigations were performed with cold water models of bottom-blown metallurgical ladles in order to develop a mathematical description of the mixing processes in such reactors. This analytical model is based on the subdivision of the reactor into interacting subspaces, whereby each subspace is regarded as an ideal mixer. The convective mass transfer between the subspaces is represented by constant coupling coefficients, and the mass balance for the material to be mixed in provides a homogeneous system of differential equations to determine the time dependence of concentration in the individual subspaces. Different combinations of interacting subspaces are represented. The flow field and the distribution of turbulence intensity measured by LDA in water models and the concentration profiles in mercury models measured by EMF cells show that a subdivision into five subspaces is adequate. Size, position and interaction coefficients are also determined by experiments. The calculated mixing times agree well with those measured.
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  • 30
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    Chemical Engineering & Technology - CET 16 (1993), S. 200-205 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Henry's law is often used to correlate the solubility of a gas in water. Such an approach is frequently employed to calculate the solubility of hydrogen sulphide in water. However, Wright and Maass [1] clearly demonstrated that the strict Henry's law did not apply to the solubility of hydrogen sulphide in water. That is, the solubility of hydrogen sulphide is not directly proportional to its partial pressure, even at seemingly low pressures. By accounting for the non-idealities in the vapour phase, Carroll and Mather [2] showed how a simple modification of Henry's law could be used for moderate pressures (up to 1 MPa). In this paper, a further extension of Henry's law is used to model the vapour-liquid equilibrium at higher pressures and temperatures. It is also applied to liquid-liquid and vapour-liquid-liquid equilibria, areas where Henry's law is rarely used.
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  • 31
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    Chemical Engineering & Technology - CET 15 (1992), S. 269-277 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The chemical and photochemical properties of a photochromic water soluble triaryl methane dye sulphite, acid magenta monomethyl magenta sulphite, (AMMM · SO3)4-, have been examined, and the application of this photochromic system to the visualization of water flows is discussed. Addition of sulphite to an aqueous solution of the parent dye acid magenta monomethyl magenta, AMMM2-, (a methylated derivative of acid magenta, C.I. acid violet 19) leads to formation of the colourless sulphite complex, (AMMM · SO3)4-. Pulsed irradiation of a solution of this compound, with light of wavelength shorter than ≈ 340 nm, causes transient production of the parent dye, whose lifetime is influenced by pH, sulphite concentration, temperature and ionic strength. Longest useful lifetimes are of the order of a few seconds and a general equation is presented for the calculation of dye lifetimes for a variety of conditions. The complex formation constant for (AMMM · SO3)4- is 1.8 (± 0.2) × 105 M-1, while that for the weakly photochromic hydroxide (AMMM · OH)3- is 1.3 (± 0.3) × 106 M-1. The quantum yield of dye production at 308 nm is ≈ 0.5 - 1.0, and this is discussed along with the absorption spectra of AMMM2- and (AMMM · SO3)4- with respect to the penetration characteristics of a pulse of 308 nm laser radiation with an energy of a few millijoules. The action spectrum for dye production from (AMMM · SO3)4- suggests that there is a non-photochromic absorption band at about 350 nm, an assumption which is supported by the failure to detect efficient dye production when using 355 nm excitation from a Nd/YAG laser.
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  • 32
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    Chemical Engineering & Technology - CET 15 (1992), S. 300-312 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Thick-walled components subjected to pulsating internal pressure are widely applied in high-pressure technology and in manufacturing processes such as fluid-jet cutting and high-pressure cleaning, mainly in conjunction with reciprocating pumps. Corrosive fluids require high-strength and tough chrome-nickel steels with soft martensitic or semi-austenitic structure. This contribution reports on the fatigue of thick-walled plain and cross-bored pipes made from high alloy chrome-nickel steels such as X5 CrNiMoCu 21 8 and X5 CrNiMo 16 5. The speciments, uniaxial standard form and thick-walled pipes, were cut from forged blocks in the three axial directions. For loading with pulsating pressure, a suitable, high-frequency piston pulsation machine has been developed. The fatigue tests on pipe specimens show typical Woehler characteristics with only slight scatter and relatively good isotropy. The surprisingly large admissible pulsating pressure can be explained for the applied steels by dynamic generation of residual stresses as a result of shake-down effects. Presentation in a Smith digram explains the occuring dynamic shake-down and its favourable results in comparison to the more brittle highly tensile steels. It also reveals that heat treatment to higher tensile strength does not always yield an increase in the admissible pulsating pressure. It will be shown that static autofretting and shake-down affect the fatigue strength of thick-walled pipe specimens in the same way. Tests with internal liners in the tube specimens provide indications on the sensitivity of material failures towards fluids. The investigation aids the understanding of the fatigue behaviour and the design of components made of modern high-strength corrosion resistant steels.
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  • 33
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    Chemical Engineering & Technology - CET 16 (1993), S. 213-217 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Treatment of a given multicomponent cationic mixture was studied applying the emulsion liquid membrane (ELM) separation technique for Zn recovery. Experimental apparatus and conditions are described. Comparative studies using two zinc-selective ion exchangers (thio-DEHPA and dithio-DEHPA) were carried out whereby the composition of the liquid membrane and the operating conditions were investigated for both extractants. A useful method of representing the concentrations of the feed and the receiving aqueous phase is proposed, which allows the occurrence of break-up and/or osmosis to be easily detected.
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  • 34
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    Chemical Engineering & Technology - CET 16 (1993), S. 238-242 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This contribution presents a method of evaluating electrical conductivities of pure organic liquids. Emphasis is placed on the methodology of selection, correlation and analysis of experimental data. The proposed method brings order out of conflicting, confusing and chaotic experimental observations. It is also shown that the consistent and evaluated data are generated at a fraction of the cost and time required for producing the original raw experimental data.
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    Chemical Engineering & Technology - CET 16 (1993) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 36
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Based on the dispersion model rather than on the conventional pluf-flow model, a method of predicting the transient behaviour of parallel and counterflow heat exchangers is developed, whereby the effects of shell-side flow maldistribution and the finite heat capacities of both fluids, tube bundle and shell are considered. The final solution has been obtained by numerical inversion of the Laplace transform, to determine the transient responses to arbitrary inlet temperature variations. The experiment was carried out in a one pass tube heat exchanger. The comparison between therotical and experimental results is presented and the feasibility of this method is discussed.
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    Chemical Engineering & Technology - CET 16 (1993), S. 413-421 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This contribution reviews the models for equilibrium and kinetics of the system Zn/D2EHPA/n-dodecane (and other diluents), published during the past decade, as well as values of the appropriate model parameters, i.e. of equilibrium and reaction rate constants. The reviewed kinetic models comprise those for kinetic, diffusional and mixed mass transfer regimes. It is shown that, under certain conditions, the rate equation within the kinetic regime has the same mathematical structure as the equations for the overall mass transfer rate within the diffusional and mixed mass transfer regimes. This means that the same equation interprets experimental data from each of the three regimes. Thus, a fit of experimental data to a model is not sufficient for discriminating between the mass transfer regimes. Results of kinetic experiments, using a stirred mass transfer cell with constant interfacial area, are presented.
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  • 38
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The separation of ethoxylated aliphatic amines from zinc containing effluents with macroporous polymeric adsorbents Wofatit EP 61, EP 62, Y 59, Y 77 and active carbons has been examined. The adsorption behaviour has been investigated as a function of temperature, time and concentration of Na2SO4, ZnSO4 and H2SO4. The macroporous polymers EP 61, Y 77 and Y 59 are capable of separating ethoxylated aliphatic amines from effluents of viscose fibre industry at higher temperatures and under weakly acidic conditions. In contrast to active carbon, inorganic components are not adsorbed on the investigated macroporous resins. Data obtained in a concentration range of 0 to 10 g of adsorbate per litre produced a Langmuir profile for adsorption of ethoxylated aliphatic amines by polymeric adsorbents.
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  • 39
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The present work investigates the energy consumption of a solids production process. Such a process consists of three different operation units: crystallization/precipitation, solid-liquid separation by centrifuges or filters and drying of wet crystals. Each unit is analyzed with the objective of minimizing the energy consumption. Operating conditions, process design and other characteristic parameters (crystal size, porosity and physical proporties) are discussed with the aim to evaluate their influence on the process.
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  • 40
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    Chemical Engineering & Technology - CET 16 (1993), S. 102-108 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Power consumption under non-aerated and aerated conditions was measured in a 0.45 m diameter tank containing a range of xanthan gum solutions, using the Scaba 6SRGT impeller. Well-mixed caverns were measured in a transparent Carbopol solution. The data are compared with previous results obtained with a Rushton turbine in the range of Reynolds numbers, Re, between 1 and 2000. In each case, the non-aerated power numbers were similarly related to Re except that the Po values of the Scaba 6SRGT were 3 to 4 times smaller. Under aerated conditions, the aeration rate does not affect the power number, Pog, with the actual value falling as a result of increasing xanthan concentration. The Pog/Po vs Re curve passes through a minimum which is lower at higher xanthan concentrations. At the same Reynolds number, the decline in power consumption of the Scaba agitator due to aeration is 20 to 50% smaller than that observed with a Rushton turbine. Well-mixed cavern shapes and sizes are also very similar to those observed with Rushton turbines and can be predicted from equations available in literature. However, instabilities in torque could present a problem in broths containing xanthan in concentrations above 35 kg m-3. Nevertheless, the Scaba agitator offers an interesting retrofitting possibility for xanthan fermentation, which could lead to improved performance.
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  • 41
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    Chemical Engineering & Technology - CET 16 (1993) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 42
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    Chemical Engineering & Technology - CET 16 (1993), S. 153-160 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Large recirculation cyclones with high concentrations of particulate solids have gained considerable importance in the field of circulating fluidized bed technology. To calculate a combustion process, the influence of the cyclone on the circulating quantity of solids and their grain size distribution must be known. Measurements in a 105-MW-plant in 1989 showed that the existing cyclone theory was not sufficient for this purpose. In a laboratory cyclone (900 mm in diameter), the separation and classification of solids in a gas flow was investigated. The cyclone was fed from a fluidized bed and operated with cold air and quartz of various grain size distributions. Based on this experimental device and the theory of momentum transfer between solids and gas flow, a new, more accurate method of calculating the separation efficiency was developed.
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  • 43
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    Chemical Engineering & Technology - CET 16 (1993), S. 186-190 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A kinetic model for the oxidation of phenol in high-pressure water has been developed and compared with experimental data taken from literature. The model assumes a chain reaction propagated by O⋅ and OH⋅. Production of the hydroxyl radical by the reaction of atomic oxygen and water induces a chain-branching effect, which is particularly effective at low temperatures and high pressures. The proposed model gives a fair correlation of the experimental data in the whole examined temperature and pressure range and appears significantly better than a simpler, power-law kinetic model. The relibility of the model is strengthened by the consideration of values obtained for the kinetic parameters (in particular for the activation energies) which compare well with the literature.
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  • 44
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    Chemical Engineering & Technology - CET 16 (1993), S. 206-212 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Interfacial tension of the binary systems pelargonic acid/ethane, pelargonic acid/carbon dioxide, linoleic acid/ethane, and linoleic acid/carbon dioxide was measured at 313, 333, and 353 K and pressures ranging up to 250 bar, using the capillary rise and Du Nouy ring methods. Both these methods yield similar values. The surface excess of supercritical components is deduced from the measurement results with the aid of Gibbs adsorption equation. The surface excess concentration increases with increasing gas activity, runs through a pronounced maximum, later decreasing rapidly to very small values. Near the surface excess maximum, a falling film of fatty acids disintegrates into a mist of tiny droplets.
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  • 45
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    Chemical Engineering & Technology - CET 16 (1993), S. 234-237 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A comparison is made between two different methods using laser induced fluorescence spectroscopy for measuring local concentration fluctuations in the same stirred tank. The first method using a single inert fluorescent tracer yields a segregation index quite different from that determined by the second method, which requires two inert tracers, a fluorescent one and a fluorescence quencher. By recalling the theoretical background, it is demonstrated that the characteristic segregation indices should be equal for the experiments under consideration. According to the discussion, it is likely that the double tracer method gives more reliable results.
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  • 46
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    Chemical Engineering & Technology - CET 16 (1993), S. 243-251 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using the micromixing concepts of Danckwerts and Zwietering, the Peclet number Pe has been correlated mathematically to the degree of segregation J for the axial dispersion model. The results were applied to compare the micromixing effects on a model, mixed-order parallel reaction system in continuous flow reactors. Axial dispersion model, and Ng and Rippin's two-environment model were used to find the micromixing effects in tubular and stirred tank reactors, respectively. The performance of these reactors, with varying geometries, has been evaluated in terms of overall conversion, selectivity, and yield under identical operating and reaction conditions. The overall conversion increases in a tubular reactor with the increase in J, irrespective of the kinetic orders. However, in a stirred tank reactor, the conversion is found to be micromixing-sensitive, depending on the order of reaction. For m = 1 and n = 2 (case 1), the conversion is fairly insensitive to micromixing effects while it decreases for m = 0.5 and n = 1 (case 2) with increasing J. For the same extent of micromixing, a tubular reactor gives, in both cases, a higher conversion than a stirred tank reactor. The selectivity, in either case, decreases in both reactors with increasing segregation effects. However, in each case, the selectivity of a tubular reactor was fairly close to that of a stirred tank reactor at the same value of J. As far as the yield is concerned, both reactors achieve nearly the same value, without significant micromixing effects.
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  • 47
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    Chemical Engineering & Technology - CET 17 (1994) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 48
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    Chemical Engineering & Technology - CET 17 (1994), S. 149-160 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Several kinds of diesel soot filters and filter materials of high melting points with eleven different catalytic coatings were prepared. They were calcined at a maximum temperature of 1000°C. The reaction rate and the kinetic parameters of the combustion of diesel soot were determined in a closed loop laboratory reactor. A packed bed of alumina particulates was the most active filter in soot combustion. Catalytic coatings with oxides of vanadium, copper or cerium accelerated the reaction. In each case the effect of the coating was dependent on specific interactions between the catalyst and the filter material. The manner of filtration and the nature of the soot filter are found to be more important for the overall result than the nature of the catalytic coating.
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    Chemical Engineering & Technology - CET 17 (1994), S. 179-186 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The conversion of ethanol over H-ZSM-5 was studied as a function of ethanol partial pressure, reaction temperature, weight hourly space velocity and Si/Al ratio. The results obtained were in qualitative agreement with most of those in the literature. Combination with all published results to give a significant regression model was not possible due to the large scatter of the data from various scientific groups. In mechanistic investigations, temperature programmed reaction measurements of ethanol, diethyl ether and ethene were performed. The formation of ethene from ethanol via direct elimination or from diethyl ether as intermediate could be confirmed. In the conversion of ethanol/water mixtures, the product distribution did not change significantly up to a water content of 60 wt%. Then, a pronounced increase of ethene formation and a considerable decrease of the yields of aromatics was observed. When several reaction mixtures from syngas conversion to ethanol were converted over H-ZSM-5, the coking rate depended on the product distribution in the feed. Product mixtures from processes with higher amounts of compounds having an unfavourable C/H ratio led to rapid deactivation of the zeolite.
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    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Titanium silicalite-1 samples of different particle size are synthesised and characterised by X-ray diffraction (XRD), photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), Raman and infrared spectroscopy. Size histograms are taken from transmission electron micrographs. Temporal changes of activity and selectivity for the hydroxylation of phenol and anisole are monitored. It is postulated that the p/o product ratios are due to the greater chemisorption of the ortho molecule.
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    Chemical Engineering & Technology - CET 17 (1994), S. 358-363 
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    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cooling breakdown in highly exothermic reaction processes may lead to runaway. The sensitivity and the safety assessment of a batch process on cooling breakdown are studied. The dependence of the minimum cooling time and the maximum allowable time of cooling breakdown for safe operation on the process parameters is investigated.
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Gas diffusion electrodes, made of PTFE-bonded carbon with precious metal catalysts, were investigated as hydrogen consuming anodes in sodium sulphate electrolysis. The catalysts used were platinum and palladium and mixtures of both metals, prepared by two different methods. Various metal meshes were used as current collector. The electrodes performed well in pure sulphuric acid (5-15 wt-%) and in mixtures with sodium sulphate (10 wt-%) at temperatures of 30 to 70°C and current densities up to 5 kA/m2. In long-term experiments, at a current density of 2.6 kA/m2, the electrodes were stable over three months. The electrodes were characterised by stationary current density/potential curves and by galvanostatic current interruption measurements.
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    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Process models are used to formulate knowledge about process behaviour. They are applied, e.g., to predict the process' future behaviour and for state estimation when reliable on-line measuring techniques to monitor the key variables of the process are not available. There are different sources of information available for modelling, which provide process knowledge in different representations. Some elements or aspects may be described by physically based mathematical models and others by heuristically obtained rules of thumb, while some information may still be hidden in the process data recorded during previous runs of the process. Heuristic rules are conveniently processed with fuzzy expert systems, while artificial neural networks present themselves as a powerful tool for uncovering the information within the process data without the need to transform the information into one of the other representations. Artificial neural networks and fuzzy technology are increasingly being employed for modelling biotechnological processes, thus extending the traditional way of process modelling by mathematical equations. However, a sufficiently comprehensive combination of all these techniques has not yet been put forward. Here, we present a simple way of combining all the available knowledge relating to a given process. In a case study, we demonstrate the development of a hybrid model for state estimation and prediction on the example of a yeast production process. The model was validated during a cultivation performed in a standard pilot-scale fermenter.
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    Chemical Engineering & Technology - CET 17 (1994), S. 50-60 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Knowledge of transport processes is of considerable practical importance in the design and performance evaluation of packed bed reactor systems. Acquisition of the required information necessitates a realistic mathematical description of the system. In this study, numerical analysis is performed for forced convective non-Darcian, non-isothermal compressible flow and heat transfer in cylindrical packed beds. Local structural and transport properties are considered. The influence of compressional work as well as viscous dissipation on the thermal field is evaluated and a general criterion provided for assessing the effect of expansion.
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    Chemical Engineering & Technology - CET 17 (1994), S. 73-80 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Due to induced turbulent interactions between particles to be separated and the scrubbing liquid present as droplets, very good collection efficiency down to submicron particle size can be achieved as shown by detailed studies [1]. Assumed are suitable flow conditions, a long residence time and a certain droplet size distribution or a special liquid dispersion system. As the name implies, the cyclone scrubber basically consists of a cyclone. This cyclone serves as a contact space in which the interaction between dust particles and scrubbing liquid droplets takes place, and as a droplet separator. Thus, under normal conditions, a water saturated but dust- and droplet-free gas stream leaves the cyclone. The droplets are generated by a pneumatic atomization nozzle, arranged at the cyclone inlet in the direction of flow. A complete theoretical description of the three-dimensional, three-phase, non-steady turbulent flow in the cyclone scrubber has not been possible up to now. The detailed experimental investigations presented in this work, and covering multiple parameters, led to physically based conclusions about the dominant interactions and separation mechanisms involved. Grade efficiencies which did not fall below 0.75, down to a particle size of 0.5 μm, could be measured by an optical particle counter. Collection efficiency of 99.2% was determined by gravimetric analysis of the dust load, according to VDI-guideline 2066, in the raw and clean gas sections of the dust load, according to VDI-guideline 2066, in the raw and clean gas sections of the cyclone scrubber.
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    Chemical Engineering & Technology - CET 17 (1994), S. 108-111 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It has been shown that, after a partial deactivation, γ-alumina (γ-Al2O3) is a good catalyst for selective methylation of 1,2-benzenediol in the temperature range of 260-310°C. The main products are the desired 3-methyl-1,2-benzenediol and 2-methoxyphenol, which may be converted in another step into 3-methyl-1,2-benzenediol, giving an overall selectivity for the desired products of 80 to 90%. The catechol forms a strongly chemisorbed surface species on γ-alumina and its steric adsorption model correlates with the kinetic data.
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    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A batch reactor directly combined with an ultrahigh vacuum apparatus, which is equipped with facilities for catalyst preparation and Auger electron spectroscopy, was used to answer some questions which had arisen in recent studies concerning carbon dioxide hydrogenation on pure metallic and supported Co catalysts. Both oxygen incorporated during oxidation/reduction cycles and carbon deposited when CO2 is hydrogenated penetrate deep into the bulk. This kind of carbon can easily be hydrogenated. CO strongly hinders the reduction of the oxidized Co surface in the H2/CO2 reaction mixture (4 : 1). CO hydrogenation is favoured over CO2 hydrogenation and leads to a higher percentage of C2 to C4 hydrocarbons as compared with CH4 formation.
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    Chemical Engineering & Technology - CET 17 (1994), S. 414-421 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Computer-aided design of a packed column to remove ethanol from aqueous solution with dibutyl butylphosphonate (DBBP) was accomplished with a programme based on the Pratt method and on the slip velocity equation. Reliable data for successful computation were obtained from literature correlations (drop size, hold-up and axial mixing coefficients for different types of packing) and from experimental work (equilibria and kinetics). Equilibrium studies on the H2O-ethanol-dibutyl butylphosphonate system were performed at different temperatures. A decrease in temperature increased the selectivity of the extractant while the distribution coefficient of ethanol, KD ≈ 1.0, remained constant. The behaviour of the system kinetics towards temperature is assessed in order to determine the initial mass transfer flux (892 × 10-3 kg m-2s-1, 30°C) and the activation energy, 22.9 kJ/kmol. The process is governed by the diffusion of the species involved. The influence of the type of packing of the column on its design is analyzed from the inventory volume of the solvent, the total volume of the column and the axial dispersion coefficients under normalised inlet and outlet conditions.
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    Particle and Particle Systems Characterization 1 (1984), S. 37-43 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Iterative numerical analysis methods, similar to those used for ray tracing in electron and ion guns, have been employed to calculate the electrical potential distribution in the vicinity of the orifice of an electrical sensing zone (esz) instrument. In particular, the electrical potential across the mouth of the orifice is considered and the effects of numerically bevelling the sharp peripheral edge are demonstrated.The results support the empirical equation: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm d}\phi {\rm /d}x \sim 1 + \alpha '\{(r/R)/(1 - r/R)\} ^{\beta '} $$\end{document} for the axial component of the potential gradient, dφ/dx, at the mouth of the orifice expressed as a function of the radial distance, r, from the centre of the orifice of radius R; α′ and β′ are empirical constants. This equation was derived from previously reported experimental data on relative shifts and heights of artefact peaks apparent on the coarse side of size distributions measured via the esz method on a series of latex copolymers.
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    Particle and Particle Systems Characterization 1 (1984), S. 143-152 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper deals with the influence of particle shape and particle size distribution on the fluidisation behaviour of granular activated carbon in the aqueous phase. Methods for relating the degree of expansion, as a function of liquid velocity, to particle shape and particle size distribution are discussed and tested. Two different types of activated carbon, both containing irregularly shaped particles but with differences in shape, are used to test the models discussed. A tentative method which takes into account the influence of water temperature on fluidisation behaviour is proposed.
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    Particle and Particle Systems Characterization 1 (1984), S. 171-177 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental methods to determine minimum sintering temperatures of a variety of granules such as polymers, glass, coal, inorganic salts, etc. are presented. These methods include the use of a dilatometer in which the contraction-dilation characteristics of a small sample is measured, a differential scanning calorimeter test and an Instron machine by which yield strengths are measured. It is clearly shown that for the majority of materials studied, the different methods give similar values for the minimum sintering temperature but that the dilatometer experiment is the simplest as well as the most reliable method. Since the minimum sintering temperature is always less than the solid's melting point, an efficient method of measuring this temperature is very important for all fluidizable granules subjected to high temperatures. The danger of agglomeration during fluidization increases tremendously at temperatures higher than minimum sintering and therefore special precautions must be taken to avoid defluidization under these conditions.
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    Particle and Particle Systems Characterization 7 (1990), S. 1-5 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Practical experience of particle size analysers using the Coulter principle shows that for measurements made over a range of 2% to 60% of the aperture diameter, the aperture responds linearly to particle volume at least for spheres. In this paper it is shown that the response of a focussed aperture is not significantly different from an unfocussed aperture. It is also shown that a simple linear equation of response successfully applied to a COULTER COUNTER® model ZM in a previous paper, can be used to predict the calibration constant of a new wide range instrument, the COULTER® MULTISIZER.
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    Particle and Particle Systems Characterization 9 (1992), S. 125-137 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The possibilities and limitations of photon correlation spectroscopy (PCS) as a practical tool for particle sizing are reviewed. In this part the most frequently used methods of data analysis are briefly surveyed. The practical performances for the determination of particle size distributions were evaluated by a comparative study with different kinds of users (industrial and academic research groups and manufacturers). The PCS results were also compared with electron microscopy (EM) and static light scattering (SLS) results. Thereby it was confirmed that the amount of reliable information that can be obtained by PCS about particle size distributions with measuring times of the order of minutes is limited by the ill-conditioning of the data inversion procedure, among other factors. Nevertheless, the information obtained from the PCS measurements agrees essentially with the EM and SLS results.
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    Particle and Particle Systems Characterization 9 (1992), S. 144-150 
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    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Beam shape coefficients, gnm, are at the core of the generalized Lorenz-Mie theory describing the scattering of a shaped beam by spheres. A decrease in computation times is essential for systematic applications of the theory. This paper introduces a new formulation to compute beam shape coefficients, gnm, in the framework of the localized approximation and discusses symmetry relations between the coefficients. The new formulation permits computation times to be decreased by one to two orders of magnitude.
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    Particle and Particle Systems Characterization 9 (1992), S. 154-155 
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    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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    Particle and Particle Systems Characterization 9 (1992), S. 151-153 
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    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experiments on the suspension polymerization of styrene were conducted at various stabilizer concentrations, dispersed phase hold-up fractions, impeller types and impeller speeds. The experimental final particle size distributions obtained were almost always described by the upper limit number distribution. Plots of the maximum diameter, amax, and the mean diameters, a21 and a10, vs. the Sauter mean diameter, a32, gave straight lines with slopes of 1.24, 0.99 and 0.97, respectively.
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    Particle and Particle Systems Characterization 9 (1992), S. 171-175 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The size distributions of four samples of quartz dust, suspended in liquids of different refractive index (RI), were determined using a Malvern 2600 laser particle sizing instrument. As the relative RI, between particle and suspension media, approached unity the instrument over-estimated the mean particle size for the three finest quartz samples. An under-estimated mean particle size was recorded for the largest quartz sample indicating the complex nature of light scattering by small particles under conditions of low relative RI.A regime of relative refractive index is determined within which particle size analysis using laser diffraction, invoking anomalous diffraction theory, becomes prone to large errors and this range is compared with the van de Hulst criterion.
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    Particle and Particle Systems Characterization 9 (1992), S. 176-185 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Phase-Doppler experiments applied to optically absorbent (homogeneous and inhomogeneous) liquids are described. Simultaneous size and velocity measurements of single droplets were executed at three off-axis angles ψ. These angles were found to be suitable for the evaluation of the phase-Doppler technique by Mie theory. Both the sizes of the monodisperse droplets and their absorption properties were varied. At least with respect to homogeneous liquids, comparison of the droplet diameters obtained by phase-Doppler measurement and by photography (reference technique) showed good agreement. Concerning the optical properties of inhomogeneous liquids, additional phase-Doppler measurements were carried out using an alternative device based on a laser diode and photodiodes. The longer wavelength λ (830 nm instead of 488 nm) reduced the influence of the inhomogeneities on the droplets' scattering behaviour and thereby improved significantly the phase-Doppler results. It is concluded that phase-Doppler anemometry is suitable for the sizing of optically absorbent droplets of real process fluids. Such droplets result from atomization processes often used in various branches, such as the chemical, pharmaceutical and food industries (production of powders and granules, "spray drying"), automotive engineering (dispersing fuels for combustion) and agriculture (crop spraying). Mie scattering theory is a powerful aid for describing the scattering behaviour of dispersed droplets of real process fluids with more complicated optical properties compared with water, i.e. the behaviour of optically absorbent homogeneous liquids, and for determining the necessary parameters of the optical set-up.
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    Particle and Particle Systems Characterization 9 (1992), S. 207-207 
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    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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    Particle and Particle Systems Characterization 9 (1992), S. 231-236 
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    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The topical problem of pulsed recording of light-scattering particles in a flux has been studied. Along with the determination of the sizes of particles, this problem involves the simultaneous evaluation of their material composition. Such a task arises in analysing multi-component disperse systems. It is shown that it can easily be realized if the particle materials differ appreciably in absorption coefficients and closeness of their refractive indices to that of the dispersion medium. This is connected with the significant difference of the spatial distribution of the scattered light. A simple method for solving such a problem has been designed with regard to the peculiarities of recording weak light fluxes and the necessity for real-time optical measurement processing.
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    Particle and Particle Systems Characterization 9 (1992), S. 213-222 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Modern image analysis equipment has now made it possible to obtain detailed intensity profile information about objects imaged under the optical microscope. If the object contrast is generated by light absorption alone then the image profile of the object is a square wave and the size information is contained in the fundamental frequency of the Fourier components of that square wave. The period of the fundamental frequency lies very close to the intensity midpoint of the image profile. As long as the microscope objective numerical aperture (NA) is high enough to pass this fundamental the object can be sized to an accuracy which is chiefly dependent upon the signal to noise ratio of the system and independent of classical notions of microscope resolution.Thus for latex particle metal replicas it was possible to determine the diameter to a precision which was typically on the order of 13% of the classical Sparrow limit of resolution for the objective employed.By sizing the same particle replica with objectives of different NA it was demonstrated that the size obtained was independent of the objective NA used as long as the replica diameter was above the Sparrow limit. This is in accordance with optical theory.About mid-summer the Goldstein "Zernike" program became available to us through the kindness of Dr. Goldstein. With this program it was possible to model the effect of optical path difference. Unlike particle replicas, most real objects generate object profiles that are a function of refractive index difference and thickness or path difference in addition to object size and transmittance. Although the "Zernike" program can accommodate path differences, it assumes that the object has negligible thickness-an assumption not merited by most real microscopic objects.Although exact quantitative agreement could not always be obtained with reasonable assumptions, the predictions of the "Zernike" program nevertheless could help to define sample preparation conditions which enabled high accuracy sizing to be performed.This work thus demonstrates that an extremely high degree of accuracy and precision in particle sizing is available from the optical microscope which is independent of classical notions of microscope "resolution". The major requirements are that the objective NA be sufficiently high enough to pass the Fourier components which contain the size information and that features in the image can be identified which contain the size information.
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    Particle and Particle Systems Characterization 9 (1992), S. 237-251 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The application of the singular value analysis and reconstruction method (SVR) and of the Contin method for the collective analysis of multi-angle noisy photon correlation data sets was investigated. Provided the data are sampled equidistant in time and by proper tuning of the sampling time to the scattering angle, a collective multi-angle SVR analysis is feasible. For homogeneous spherical particles such an analysis does not require any prior knowledge of the angular dependence of particle scattering power (e.g. Mie scattering). SVR allows the information content to be separated from noisy intensity autocorrelation data. It is illustrated that the multi-angle SVR analysis enhances the recovery of the information content. Moreover, SVR can be used as a fast and accurate preprocessor for extracting the field autocorrelation function for a subsequent Contin analysis whereby prior knowledge of particle scattering power as a function of scattering angle is used as a constraint. Compared with the data analysis of multi-angle time-averaged scattered intensity measurements, the information that can be extracted from multi-angle PCS data in comparable accumulation times is poorer.
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    Particle and Particle Systems Characterization 9 (1992), S. 259-263 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An unexpectedly large additional three phase locking region, the outlaw area has been found where three phase, locked particle may be formed. This implies that in some ores, the number of three phase locked particles may be an order of magnitude larger than expected. The size of this outlaw region is sensitive to the angle at which the three phases meet. Since these higher order locked particles behave differently in separation circuits, it is proposed that in characterizing a solid or ore rock, these angles between the interfacial planes be both measured and included in a Textural Transform.
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    Particle and Particle Systems Characterization 10 (1993), S. 7-10 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An image analysis system for extracting on-line quantitative geometric and densitometric information from images of ore samples is described. The apparatus employs a pulsed semiconductor laser as the light source for illuminating of a flowing stream of particles and a non-interlaced solid-state TV camera as size measurement device in a shadowgraph imaging system. The problem of the sampling volume is discussed and several size distributions of solid particulates are presented. The particle size measurement range is 2-400 μm.
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    Particle and Particle Systems Characterization 10 (1993), S. 11-18 
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    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Accurate information on the size distribution of fly ash is needed to determine its role in the radiation transfer process in pulverized coal combustors. The Coulter Multisizer was used to determine the size distribution in the particle diameter range 1-200 μm. To size over such large diameter ranges, data must be obtained using several orifices, and then combined. In order to use the smaller orifices, the larger particles have to be removed from the sample. A wet-sieving apparatus, designed for accurate separation of the particles by size, is described. A scheme for combining data obtained using orifices of different diameters is presented. It appears from this study that the lower limit of size measurement using an orifice is set by sensitivity, rather than by signal/noise. A lognormal distribution function, truncated outside the measurement limits, fits the size distribution data well. This function allows detailed size information to be stored compactly using four parameters. Size parameters for six fly ashes representative of U. S. coals are presented.
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    Particle and Particle Systems Characterization 10 (1993), S. 38-38 
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    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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    Particle and Particle Systems Characterization 10 (1993), S. 26-32 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It is often necessary to estimate the properties of particle size distributions from limited samples taken from large populations. When the distributions are broad, and higher order moments required, as in the case of volume based particle size distributions, the inferred parameters d3,50 (volume median diameter) and GSD (geometric standard deviation) can have high intrinsic errors not immediately obvious to the measuring scientist. We show that there is a critical number of particles, Ncrit, which must be counted or else the error may blow up catastrophically. Ncrit is very sensitive to the width of the distribution, and is approximately proportional to GSD11 We develop formulae to estimate the random sampling error inherent in measured values of the d3,50 and GSD for the log-normal distribution; compare the predictions to a typical experimental particle size measurement; and then generalize to the median of any arbitrary moment, dr, 50.
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    Particle and Particle Systems Characterization 10 (1993) 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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    Particle and Particle Systems Characterization 10 (1993), S. 48-55 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The working principle of the single-fibre reflection (SFR) probe is that light emitted by a laser diode is guided into the measuring volume by the same fibre which receives the proportion of light reflected by the particles in the vicinity of the probe tip and transmits it back to a photosensitive element. In contrast to other configurations of fibre optical probes, the SFR probe is characterized by an unambiguous calibration graph over the entire range of solid volume concentration values. SFR probes have been successfully applied to different kinds of multiphase flow systems, e.g. fluidized beds, pneumatic conveying lines, elutriators and thickeners.A particular question for the interpretation of measurements has always been the effective size of the measuring volume, which is mainly determined by the solid volume concentration. In this paper a simplified mathematical model of the signal generation by backscattering of the emitted light at the particle surfaces is given. The theory takes into account the average optical properties of the solids and their particle size distributions.The particle properties are determined on the basis of this model, which finally delivers the shape, size and depth of the effective measuring volume. For particle sizes between 30 and 120 μm the depth of the measuring volume of a 600-μm fibre probe is between 0.2 mm for solid concentrations near the fixed-bed state and approximately 4 mm for solid volume concentrations as low as 0.1 vol.-%.
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    Particle and Particle Systems Characterization 10 (1993), S. 86-91 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To produce disperse products, the characterization of the disperse state and a knowledge of the property function are essential. Property functions are applied not only to characterize the quality of an end product, but also to determine the influence of different processing steps on its state. Hence it is necessary to know the property and process functions for quality assurance of the products and for safety of the processes.Good laboratory particle measuring technologies are available for investigating property and process functions. On the basis of these functions, process control takes place. On-line or, better, in-line measuring techniques are necessary to enable the accompanying process information to be obtained.
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    Particle and Particle Systems Characterization 10 (1993), S. 79-85 
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    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The paper discusses the interest in conventional triaxial tests widely used in soil mechanics for a better understanding of both the mechanical behaviour and flow characteristics of granular bulk materials. It proposes a rheological characterization of granular foodstuffs on diverse types of stress path using a conventional triaxial cell. The characteristic state concept, defining the disaggregation threshold of the granular structure, is found to be suitable and even indispensible for examining the mechanical behaviour and the flowability of stored bulk materials. The experimental results readily suggest, as an indicator of the arching effect, a rheological index that characterizes the particle interlocking breakdown and hence the flowability of the stored materials. In addition, this study offers a realistic physical meaning for parameters in use in constitutive models (yield conditions and flow rules) when describing granular flow in various hopper geometries. The case of silos equipped with vibrating hoppers necessitates additionally the study of the rheological behaviour of materials under cyclic and vibratory loadings in order to analyse the processes of densification or disaggregation conditioning the flowability of the stored materials during emptying operations.
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    Particle and Particle Systems Characterization 10 (1993), S. 111-117 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Extended Boundary Condition Method (EBCM), also known as the T-matrix method, is used to compute exactly the scattered intensities from homogeneous isotropic circular cylinders characterized by relative refractive index N, diameter D and length L. The domain of convergence of the method regarding the parameters N, D, L is established. The effect of the geometry of the fiber ends on the scattered intensities is considered. The incident field is assumed to be a linearly polarized plane harmonic wave.
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  • 83
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    Particle and Particle Systems Characterization 7 (1990), S. 127-130 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new particle size distribution function based on a simple model is presented. Data generated by the normal, log-normal and Rosin-Rammler distribution functions were fitted with this new distribution function and the fitted curves were, for all practical purposes, indistinguishable from all three distributions.The new distribution function can replace all the three functions and thus a means of presenting and comparing the different size distribution patterns in terms of a single mathematical expression is obtained. Additionally, the new distribution function provides the possibility of developing the discussion on the physical meaning of the particle size distribution.
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  • 84
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    Particle and Particle Systems Characterization 7 (1990), S. 136-143 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dispersion of monosized drops downstream a point injection in a grid-generated turbulence is studied. Influence of extra bodyforces is also investigated by use of ferrofluid drops and magnetic field. Datas are obtained through LDV and given for fluid and particles mean and fluctuant velocities. Presence probability repartition for particles downstream the injection is obtained by LDV counting.
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  • 85
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method based on the employment of an electrical sensing zone instrument (Coulter Counter) has recently been proposed for the combined measurement of the increase in particle volume (particle swelling) and granulometric characterization of pharmaceutical tablet disintegrants. The performance of the method, as far as its applicability to limited swelling materials is concerned, has been assessed. Both inert materials (polystyrene latices) and limited swelling disintegrants (maize starch and crospovidone in different granulometric fractions) were examined for total particulate volume in aqueous media. The accuracy and repeatability of measurements of both total particulate volume and particle volume increase were defined. The results obtained indicate that the method may be adapted for measuring the increase in particle volume of so-called limited swelling disintegrants.
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  • 86
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    Particle and Particle Systems Characterization 7 (1990), S. 121-126 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Various types of floor tile were tested in a controlled and isolated environment to determine quantitatively the wear rate and size characteristics of material generated from floor tile during operations of sanding, cutting, and breaking. Size characteristics were determined for the aerosolized fractions as well as the settled material worn from the tile surface. In addition to the vinyl composition tile, tests were also conducted with floor tile containing various amounts of glass fiber and sodium phosphate fibers. The tests were conducted in a specially designed glove box which allowed complete sampling and fractionization of the generated aerosol. Due to good measurement repeatability, aerosol generation differences from the various flooring types were determinable.A Frick-Taber accelerated wear machine was employed to establish comparative wear rates of the different flooring materials. Test results were repeatable and measured relative wear rates correlate well with published measurements. Results indicate that the presence of up to 13% glass fibers or phosphate fibers in the tile does not improve the tile's wear characteristics or significantly alter the size distribution of the generated material. Although asbestos-containing floor tile was not tested in this study, results from the simulant fiber tile tests may enable prediction of the behavior of vinyl-asbestos tile under the influence of similar wear mechanisms.
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  • 87
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    Particle and Particle Systems Characterization 7 (1990), S. 169-169 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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  • 88
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    Particle and Particle Systems Characterization 10 (1993), S. 252-261 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A review of existing and developing process tomographic instrumentation suitable for characterising dry and wet particulate systems is presented. Factors governing the selection of sensing techniques appropriate for static and dynamic imaging of a wide range of single and multiphase particulate processes are discussed. The paper presents a systematic comparison of different image reconstruction methods. Examples of existing, developing and proven applications are cited. Future needs and ways in which these needs can be met are suggested, including the use of multi-modality methods in which different types of sensing methods are embodied in a single tomographic instrument.
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  • 89
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    Particle and Particle Systems Characterization 10 (1993), S. 266-270 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: On-line characterization of powder and droplets during gas atomization of molten metals and alloys offers extensive opportunities for real-time process monitoring and control. The capability to make on-line measurements can significantly reduce tedious and costly powder classification, which, currently, is always carried out subsequent to the atomization process. Two laser-based particle sizing instruments, the EPCS (ensemble instrument) and PCSV (single particle instrument), were used during gas atomization of zinc with a double Coanda nozzle configuration. The laser instruments were positioned in the duct leading from the bottom of the atomization tower to the powder collection cyclone. The effect of gas to metal ratio on particle size was studied by varying the atomization gas pressure from 0.69 MPa to 1.03 MPa. Air was used as the atomizing gas for some of the 0.69 MPa runs, while nitrogen was used for all of the higher-pressure runs. Experimental apparatus and procedures for atomization and on-line powder sizing with the EPCS and PCSV are described. EPCS and PCSV measurements, which were compared with standard sieve analyses, indicate that the ensemble instrument is a good candidate for on-line process monitoring and control.
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  • 90
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    Particle and Particle Systems Characterization 10 (1993), S. 290-293 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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  • 91
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    Particle and Particle Systems Characterization 10 (1993) 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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  • 92
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    Particle and Particle Systems Characterization 10 (1993), S. 246-251 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method for the rapid on-line determination of surface area and solids content in flowing concentrated slurries using low field NMR spin-lattice relaxation measurements has been developed and demonstrated. The relationship between flow and spin-lattice relaxation time (T1) of protons in water at 20 MHz was examined using aqueous copper sulfate solutions. The ability to measure surface area and solids concentration in both stagnant (stopped flow) and flowing systems via NMR was demonstrated using several different concentrated aqueous titania and glass slurries (20 to 80 weight percent) for which the dried powder surface area was previously determined via nitrogen adsorption/BET analysis and the solids content determined gravimetrically. Surface areas were also calculated from particle size analysis and found to vary by up to an order of magnitude from the adsorption and NMR results.
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  • 93
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    Particle and Particle Systems Characterization 10 (1993), S. 239-245 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aggregates formed from colloidal particles will vary in shape according to the aggregation regime prevalent. Compact structures are formed when the aggregation is slow, whilst loose tenuous structures are formed when rapid (or diffusion limited) aggregation prevails. These structures can be fractal in nature, that is, there is a relationship between porosity and the number of primary particles making up the aggregate, and is described by the fractal dimension, dF. Fractal dimensions of hematite aggregates have been measured experimentally using the static light scattering technique. Fractal dimensions varied with aggregation regimes; for the rapid aggregation regime, dF was found to be 2.8, whilst for conditions in which aggregation was slow (retardation forces prevail), dF's of 2.3 were measured. For conditions which lead to aggregation in which both diffusion and retardation forces play a part, structures with fractal dimensions such that 2.3 〈 dF 〈 2.8 were found.The effects of adsorbed fulvic acid, a naturally occuring organic acid, on the kinetics of hematite aggregation and on the resulting structure of hematite aggregates were also investigated. The study of aggregate structure shows that the fractal dimensions of hematite aggregates which are partially coated with fulvic acid molecules are higher than those obtained with no adsorbed fulvic acid. The scattering exponents obtained from static light scattering experiments of these aggregates range from 2.83 ± 0.08 to 3.42 ± 0.1. The scattering exponents of greater than 3 indicate that the scattering is the result of objects that contains pores which are bounded by surfaces with a fractal structure, and can be related only to surface fractal dimension. The high fractal dimensions are due to restructuring within the aggregates, which only occured at low coverage by the organic acid.
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  • 94
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    Particle and Particle Systems Characterization 10 (1993), S. 234-238 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This work on imaging of particulate processes using electrical charge tomography uses two basic techniques: the multi-sensing of electrical charge in a cross-section of the flow pipe and a neural network based flow regime identification system to aid in the image reconstruction process.A measurement system, consisting of sixteen sensors, placed at equal distance from each other around the boundary of a circular 100 mm bore pipe, is used to determine the voltage profile of the flow for several artificially produced flow regimes: full, annular, core, half and stratified. A sand flow system is used to produce these different flow regimes, which are created artificially by using baffles of different shapes that obstruct the sand flow.The voltage profile from the sixteen sensors gives spatial information of the flow regime. These profiles are normalised and formed into patterns that are presented to a Kohonen neural network for classification. Two regime classification between clearly distinct regimes gives an accuracy of identification of 85%. Classification of closely similar patterns show much less accuracy of 30%.
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  • 95
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    Particle and Particle Systems Characterization 10 (1993), S. 262-265 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In-process measurement of particle size and concentration distributions provides continuous analysis and quality control of a product stream. Elimination of sample handling and operator manipulation is now possible for most pneumatic flows using optical methods which are properly interfaced with the process stream.The EPCS (Ensemble Particle Concentration & Size) described in the following has been used to obtain detailed size distribution measurements in powder production facilities at two second intervals, and has been successfully used for automatic feedback control.
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  • 96
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    Particle and Particle Systems Characterization 10 (1993), S. 271-274 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The paper discusses the application of image analysis to multiphase mineral particles. The emphasis is on the development of automatic and routine methods which provide reliable data for the process engineer. Optical systems are discussed briefly, but electron beam instruments are shown to offer many advantages for the identification and discrimination of mineral species. Image capture and analysis procedures are described together with the application of the measured data to aid our understanding of the processing properties of particles of complex structure. Examples are given from studies of beach sands, silver minerals, flyashes, ore characterisation, flotation of base metals, grinding and liberation.
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  • 97
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    Particle and Particle Systems Characterization 10 (1993), S. 279-289 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The response of the Partec laser backscatter particle size analyzer has been tested under a variety of conditions. Various materials posessing different light scattering characteristics have been examined and the response of the Partec instrument has been evaluated. In particular the system response to transparent particle systems (e.g. oil in water emulsions) tas been studied. It has been found that the Partec laser backscatter instrument provides reasonably accurate and reproducible results when used to characterize opaque, highly reflective particles such as hydrated alumina, but suffers from a lack of sensitivity to fine transparent particles such as oil droplets. The instrument does, however, readily detect the presence of opaque particle contaminants in oil-water emulsions.
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  • 98
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    Particle and Particle Systems Characterization 10 (1993), S. 357-363 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Concrete quality is influenced to a high degree by the granulometry of the aggregates used. In the construction industry, the grain size coefficient of K-coefficient is used as a quantity for the characterization of granulometry. In practice, this quantity is determined experimentally, and it is therefore a random variable influenced by material heterogeneity and errors in sampling, sample preparation and size analysis. Depending on the final use, in concrete production often an aggregate is required, the grain size coefficient of which can be adjusted to a given value Krequ with a prescribed precision. For this reason, continuous supervision of the aggregate quality is necessary using, e. g., automatic sampling and opto-electronic measuring equipment. In order to determine the optimum conditions for the installation of such equipment, the variances of the possible errors must be established. Further, methods for their restriction are necessary. In this paper, investigations involving hand sampling and hand sieving and on the example of a reference gravel plant are reported. The investigations reveal that, for the materials involved, primary samples of at least 1600 g were necessary, which then could be reduced to 200 g by sample splitting, in order to obtain the accuracy desired.
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  • 99
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    Particle and Particle Systems Characterization 11 (1994), S. 6-6 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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  • 100
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    Particle and Particle Systems Characterization 11 (1994), S. 5-5 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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