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  • Electronic Resource  (328)
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  • 2005-2009
  • 2000-2004
  • 1990-1994  (58)
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  • 1
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Formaldehyde is produced industrially from methanol by partial oxidation of oxidative dehydrogenation. In these processes, water is formed as a by-product. Anhydrous formaldehyde is required for many syntheses and, therefore, its production is of potential interest. In the present study, catalysts based on alkali compounds were found to be active in the dehydrogenation of methanol if absence of oxygen. Sodium carbonate doped with indium shows a selective of up to 75% for methanol conversion not exceeding 60%.
    Additional Material: 10 Ill.
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  • 2
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Copper and potassium containing Fe/Mn oxide catalysts for Fischer-Tropsch synthesis were investigated by X-ray microprobe technique, scanning electron microscopy, low-temperature argon sorption and carbon monoxide and carbon dioxide chemisorption at -80°C. The specific surface areas of the catalysts depend on the preparation method, e.g. addition of K or Cu by coprecipitation leads to an increase while impregnation results in a decrease in surface area. The resulting samples are inhomogeneous, as shown by all method. Mn and especially K accumulated on the surface of the catalysts. Addition of Cu and K considerably altered the selectivity and activity of the Fe/Mn oxide catalyst. High potassium contents produced high olefin to paraffin ratios but these catalysts became rapidly deactivated. Copper and a very small addition of potassium led to a very low olefin to paraffin ratio but showed a high and constant activity.
    Additional Material: 4 Ill.
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  • 3
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new model of suspended bed of droplets for describing the vaour or gas the vapour or gas velocity at the flooding point in packed of columns for rectification and absorption under vacuum and normal pressure is presented metallic, ceramic and plastic packings with diameters of 8-90 mm as well on sheet metal and gauze packings, in a wide range of liquid and vapour loads. Approximately 650 literature measurements and own data were evaluated. The mean relative error in determining the gas velocity at flooding point is less than ±5%. On the basis of the double layer model, a new equation was derived for the hold-up at flooding point, which is needed for the calculation of the flooding gas velocity. An example of calculations for sample applications is also included.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 229-237 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new laboratory plant for batch cooling crystallization is described, which allows to maintain the supersaturation at a constant level during an experimental run. A method for continuous supersaturation measurements has been developed, using a density meter and a hydrocyclone. Experimental results obtained from a seeded solution in constant supersaturation cooling mode and at constant cooling rate are compared. In the case of a constant cooling rate, the supersaturation passes through a sharp maximum, whereby effective nucleation is enhanced. As a consequence, a smaller median crystal size is obtained than for cooling at constant supersaturation. Equation for controlled cooling at a constant supersaturation require an accurate description of the effective rate of nucleation. Therefore, the mechanical stress, to which the crystals are subjected, must be included as the main source of new nuclei. This is shown by the influence of stirrer on batch time.
    Additional Material: 9 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 241-251 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pyrolysis of 2,3-dimethyl butane (DMB) was carried out in a quartz flow reactor in the temperature range from 740 to 1032 K at normal pressure. The input concentration of DMB was 3.3 × 10-3 mol/1 using argon as diluent. Reaction time ranged between 3.1 and 3.9 s. The following products were analyzed by two-column gas chromatography: hydrogen, methane, ethene, propane, propene, butenes, butadiene, 2-methyl-2-butene, isoprene, benzene and toluene. Compared to thermal decomposition of n-hexane under similar experimental conditions, the main difference concerned the formation of ethylene, ethane and branched alkanes. A reaction model, based on elementary reactions, was developed to predict the experimental results and to verify our data basis of elementary reactions under different conditions. The model gives a quantitative description of the complex chemistry of the process. In addition, an algorithm is presented for model reduction.
    Additional Material: 6 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 264-272 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper describes general, asymptotic and speculative relationships which can be deduced directly from the time-averaged form of the basic, partial-differential model for the conservation of mass and momentum in fully developed turbulent flow of constant-property fluids through round and parallel-plate channels. Such relationship are shown to provide insight as well as useful forms for correlation. Several analogies for flow in round tubes and between parallel plates which have generally been overlooked are reexamined and extended. A generally overlooked anomaly which occurs for flow in concentric, circular annuli, for flow between plates of non-identical roughness, and for the combination of forced and wall-Ind.uced flow between parallel plates is also is noted. The data needed to test the above analogies and to quantify the deviations, if any identified, as well as those needed to generalize the anomalous behavior.
    Additional Material: 1 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 298-303 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Adsorption isotherms for n-hexane and methanol in mordenite and ZSM5 in the temperature range from 323 K to 473 K were found to be of type 1. The adsorbate-adsorbent interaction (C1) and adsorbate-adsorbate interaction (C2) wee computed according to Bradley and Wilkins model, whereas the Rees and Williams model predicts the adsorption characteristics. Finally, the thermodynamic parameters such as ΔGo, ΔSo, ΔHo, K, K+ have been evaluated for the sorption of n-hexane in mordenite and ZSM5.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Incineration processes are critical for the environment. SO2 and NOX removal with processes is nowadays commonplace. Up to now, heavy metal were recovered via precipitation. The alternative use of liquid ion exchange techniques offers an easy re-use of the heavy metals, which are obtained as concentrates. A separation process is described, starting from laboratory experiments and ending with pilot plant field tests. A cost comparison for extraction, permeation and precipitation gives the scope of the necessary expenses for such environmentally controlled processes.
    Additional Material: 13 Ill.
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  • 9
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In industrial processes, the reduction of nitrogen oxides by ammonia on activated carbons is carried out at temperatures between 90 and 190 °C. Adsorption of NO and NH3 on the catalyst was investigated separately. Reactions models for NO-reduction by carbon and ammonia were derived from experiments carried out in an integral reactor. In each case, the formation of an adsorbed (NO2)-complex is an important step. The kinetics of both reactions was described by modified Langmuir-Hinshelwood equations.
    Additional Material: 20 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 289-297 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new stage-to-stage method has been developed for the calculation of NXx absorption columns. Each stage of the absorption column is simulated as a combination of a bubble column reactor (absorption) and an adiabatic plug for reactor (oxidation). The bubble column reactor is modelled as two single stirred tank reactors, one as a gas-phase and one as a liquid-phase reactor, both coupled by mass and heat transfer. In this hydrodynamic model, a dynamic approach is adopted, in which the gas-phase transport of N2O4 is the limiting step for the absorption. A gas-phasepseudo-enhancement for factor for N2O4 is therefore introduced. The balance equations for a single phase of the bubble column are solved with a Newton-Raphson algorithm. The entire column calculation is divided into a gas and a liquid side. On both sides, the stage-to-stage method is applied in such way that the overall calculation is performed as a loop process. The direction of the loop calculation follows that of the flow: gas-side upwards and liquid-side downwards.
    Additional Material: 5 Ill.
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  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 376-383 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A theoretical and experimental study of the electrohydrodimerization process to produce adiponitrile is used to determine an appropriate reaction model. From numerical simulations of five proposed reaction schemes and subsequent comparison with experimental data, the most favoured route is via an anion, intermediate of acrylonitrile. This route, a five step reaction involving electrochemical and chemical reaction in a diffusion/reaction layer, gives good predictions of product distributions over a wide range of current densities and acrylonitrile concentrations of product distributions over a wide range of current densities and acrylonitrile concentrations.
    Additional Material: 12 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 397-402 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents a method of transforming the non-liner regression problem in the kinetic study of complex heterogeneous catalytic reactions into a linear regression problem. Application of this method reduced the number of parameters to be estimated by n-1, where n is the number of independent reactions. In addition, a stepwise model discrimination strategy in introduced to reduce the number of equation sets ad equations in the set undergoing parameter estimation. These two new approaches are very advantageous in reducing the computation effort, especially when the number of independent reactions is large. The linear regression method and the stepwise model discrimination strategy are successfully applied in the kinetic study of the methanol synthesis system in which the formation rates of methanol, methane, ethanol and ethane are considered.
    Additional Material: 4 Tab.
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  • 13
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 41-49 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This contribution presents the mechanical data of high performance carbon fibres currently available on the market, based on experimental studies on stabilization and pyrolysis of PAN (SAF) from Courtaulds. The effects of stabilization and carbonization temperatures on the properties as well as on the ultra- and crystalline structures of the fibres are shown in more detail.
    Additional Material: 22 Ill.
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  • 14
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The residence time distribution in liquid phase was measured in a cocurrent upflow packed bed reactor for the system methanol-hydrogen at low Reynolds numbers and at elevated pressure. The plug flow with axial dispersion model was used to describe mixing in the system. The imperfect pulse method was used to measure the system response to a tracer pulse input. The parameters were calculated using the weighted moments method. The influence of the weighting factor was investigated. The experimental and theoretical outputs, as calculated by convolution, agreed very well. Different types of correlations were used for the Bodenstein number and liquid hold-up. From these correlations, the optimal one was selected for each parameter. A comparison was made between the ordinary moments and the weighted moments methods which led to the conclusion that the latter method is superior with respect to the accuracy of the estimated parameters and therefore strongly recommended.
    Additional Material: 11 Ill.
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  • 15
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the first part of this paper, a mathematical model is presented for a liquid fluidized bed bioreactor using immobilized enzymes with reversible Michaelis-Menten kinetics. The model is based on the axial dispersion model for the bulk liquid phase. Inter- and intraparticle mass transfer as well as enzyme catalyzed reaction inside the porous beads are considered. The overall efficiency of the biocatalysts is calculated by a numerical routine. For the calculation of the concentration profile inside the reactor, a semi-analytical solution is derived which takes into account the height dependence of the effectiveness factor.
    Additional Material: 2 Ill.
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  • 16
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Even though the influence of solids concentration in the feed on the separation efficiency of hydrocyclones has long been recognized, a systematic research on the change in pressure drop across the hydrocyclone and the latter's separation characteristics has thus far been lacking. If all other operating parameters are kept constant, an increase in feed concentration generally leads to a coarser cut size, reduced sharpness of separation and a rise in pressure drop. Apart from the particles hindering one another's radial motion, the limited capacity of the apex valve and the changes in the flow field within the hydrocyclone cause additional particles to be entrained by the overflow. The flow ratio thus becomes an additional parameter in determining the cyclone efficiency. A theoretical model, which takes these effects into account, has been developed and successfully tested against experimental data.
    Additional Material: 12 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 63-71 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bench scale experiments and computer simulations of transient crystal size distributions obtained in a 1.4 m3 sucrose crystallizer, which prove the existence of nuclei stock, are presented. This stock represents a large number of non-growing nuclei, which can be activated at increased supersaturations. The nuclei stock attenuates the dynamic behaviour of crystallization process.
    Additional Material: 8 Ill.
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  • 18
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Supersaturation is the driving force for crystallization from solution. For design and operation of crystallization processes, it is necessary to apply a set of criteria for the determination of appropriate or even optimum supersaturation. In this paper we present and discuss the results of our experimental and theoretical investigations on supersaturation during crystallization from solution. While the determination of the metastable zone width of the solution is frequently applied as a fast check on solution behaviour, we demonstrate that the determination of the induction period of the supersaturated solution is a useful aid in ascertaining the maximum allowable supersaturation. Theoretical considerations and experiments confirm that the induction period dependssoley on growth kinetics if secondary nucleation is the predominant mechanism. In order to avoid uncontrollable spontaneous value of between 70 and 130 μm during crystallization. Since growth kinetics turns out to be the only important system property for the determination of maximum possible supersaturation, we conclude the paper with some arguments concerning a closed representation of growth kinetics.
    Additional Material: 15 Ill.
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  • 19
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An airlift-loop reactor with a fluidized bed was used for the microbiological removal of a complex mixture of aromatic substances originating from coal tar process waters. A specially adapted mixed microbial culture derived from several soil and sludge samples was immobilized on fluidized sand particles and retained in a reactor at high biomas concentrations of 3 to 16 g dry matter per liter, depending on the COD-load. In a two-stage pilot plant, those aromatic substances which passed through the first stage either unaltered or only partially oxidized were effectively eliminated by the immobilized biomass in the second stage. Whereas most of the waste water components such as phenols and quinoline were already degraded by a conventional activated sludge system in the first stage, the majority of nitrogen-containing aromatic bases could be sufficiently eliminated with specially adapted micro-organisms in the second stage. Although the COD-feed load was increased to 12 and 15 kg m-3 d-1 in the first and second stages, respectively, it was removed to the extent of 87% on the average with an overall residence time varying between 11.5 and 29 h.
    Additional Material: 9 Ill.
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  • 20
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 86-96 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The first part of this paper presents a relationship for the minimum velocity of rotating installations for foam breaking. The derivation is based on equilibrium of inertia and surface forces. Inertia forces occur during the acceleration of foam bubbles and act mainly at the plateau borders. High and definite acceleration can be obtained with a deformer composed of a rotor and a stator. The surface force is due to the dynamic surface tension because surface-active solutions react to a rapid change in surface area by altering their surface tension. The theoretical relationship is compared with experimental results of minimum velocities needed to break foams produced from aqueous solutions of detergents. The equation presented here explains why measured minimum velocities often range between 10 and 20 m/s. The second part of the paper deals with condensation of continuously generated foam in a closed system. In the process of condensation, foam is not completely separated into liquid and gas phase but turns into foam with small bubbles and high density. The collapse of this condensed foam must be considered for the control of persistent foams in a closed system. The collapse of foams made of aqueous solutions of different surface-active agents has been investigated. Different highly surface-active agents show small variations in times of coalescence. A relationship for the lifetime is given, which is based on laminar flow along plateau borders. Recommendations are made with respect to the geometry of the foam breaker, scale-up and operating variables such as rotational speed of the foam breaker and gas flow rate.
    Additional Material: 15 Ill.
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  • 21
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 349-356 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Owing to imperfect mixing, the theoretical prediction of CSD for an MSMPR crystallizer deviates from the experimental results. In the present work, different modelling approaches were adopted to account for incomplete mixing in DTB and FC crystallizers. For DTB crystallizers, compartmental model, based on an earlier work of Nyvlt et al. has been proposed. For FC crystallizers, a mixed model comprising perfectly mixed and plug flow regimes has been put forward. This is based on the tracer response studies reported by de Jong. Predicted results were compared with experimental data of Bennett and van Buren for continuous urea crystallizers.
    Additional Material: 2 Ill.
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  • 22
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Compared to chemical reactors, there are additional requirements to be considered when selecting and designing a bioreactor. The cultivated organisms and most of the desired products are to a greater or lesser extent sensitive to temperature, pH and Shear stress. Furthermore, sterilization often plays an important role in maintaining a monoseptic process. Many design procedures for chemical reactors can be applied but requirements which are relevant to the biological system are sometimes decisive. Consequently, it is useful to first consider the essential features of the organisms with respect to the selection and design of bioreactors. Attention must be paid to the fermentation medium because its flow behaviour can range from slightly viscous and Newtonian to highly viscous, non-Newtonian. Many papers deal with low viscosity fermentation broths [1-5]. However, little is known about the design of bioreactors for highly viscous non-Newtonian liquids. Fundamentals for the design of bioreactors are presented. It has been attempted to apply theoretical equations suitable for both, low viscosity Newtonian and high viscosity non-Newtonian fermentation broths. Apart from the calculation procedure for the OTR-values, the difference between global and local values within bioreactor is demonstrated by means of velocity and shear stress profiles. Special requirements for bioreactors such as prevention of excessive foaming, shear sensitivity of micro-organisms and cell-lines and effective sterilization are also discussed.
    Additional Material: 15 Ill.
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  • 23
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 392-397 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Monte Carlo simulation scheme is proposed for transient crystal size distribution in a continuous crystallizer. The suggested scheme can taken into account dispersion effects of growth rate, shape factor and birth size on crystal size distribution. This method is simple and more versatile than solution of the number balance equation or the finite-state Markov chain model. The proposed algorithm of the process has a very simple structure and can be easily implemented on a personal computer. The present contribution is extension of an earlier work of Sen Gupta and Dutta.
    Additional Material: 3 Ill.
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  • 24
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The presented contribution reports on comprehensive hydrodynamic investigations in two pulsed sieve-plate extraction columns (PSE) on a pilot scale. The experiments were conducted with three different sieve plate geometries employing test systems recommended by EFCE, under varying pulsation conditions and throughputs. The results of the investigation add to the existing knowledge of relationships between hydrodynamic parameters, drop size, hold-up, flooding throughput and mixing and operating parameters. They also provide useful information for scale up, selection of sieve-plate geometry, most favorable operating range, and constructive design of equipment. On the basis of measurements, analytical methods are recommended for prediction of PSE hydrodynamics.
    Additional Material: 15 Ill.
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  • 25
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 304-312 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Some properties of carboxylic acids are reviewed, with emphasis on recent experimental data, Qualified, consistent latent heat of vaporization data were developed for the series and a two-population viewpoint is suggested. The equation of state formulated by Grenzheuser [1] is also recommended as a practical tool, and its further development is urged.
    Additional Material: 16 Ill.
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  • 26
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 328-332 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The linear algebraic character of the formal representation of chemical species and their reactions is compared with the procedure of searching for dimensionless numbers in a set of physical quantities. A straightforward algorithm is presented to find a finite set of solutions to the relevant system of “balance equations”, the so-called minimal (or simple) solutions. At the third stage of the hierarchy thus established, “mechanisms” among reactions as well as “representations” among dimensionless group can also be defined.
    Additional Material: 2 Ill.
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  • 27
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A heterogeneous fluid dynamic model has been developed to describe the complex flow structure of two-phase in bubble columns. The equation of continuity and momentum balances form the basis of the model. Coupling of the two phases occurs via an interaction force, deduced by a force balance around a single rising bubble. Multiphase flow mixing processes are taken into consideration by introducing turbulent viscosities of the two phases involved. The Simulation program was extended to reactive system, taking into account the mass balances of a second order gas-liquid chemical reaction as well as the different absorption/reaction regimes. The gas phase concentration profiles show pronounced axial and radial dependences, while the liquid phase can be regarded as a CSTR with respect to the liquid component. With reference to the gaseous component, which is being absorbed in the liquid phase, the degree of back mixing does not show CSTR behaviour as the influence of different absorption conditions in different axial and radial reactor positions is superposed on that of turbulent motion of the liquid carrier of the dissolved gaseous component.
    Additional Material: 13 Ill.
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  • 28
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 29
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 119-125 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dynamic mathematical model has been developed which is suitable for thermally coupled distillation processes. An algorithm known as the equation-decoupled method was used for simulation. EPISODE software and LU decomposition method were adopted to solve the ordinary differential and algebraic equations of the model, respectively. The initial conditions, viz. a solution for the steady state of the process in dynamics simulation were obtained by means of modified Naphtali-Sandholm algorithm. Research on the dynamic behaviour of thermally coupled distillation processes was carried out on two examples. It was found, via the dynamic simulation, that a disturbance in the distribution of vapour coupled stream has a large effect on the composition of vapour side withdrawal and, similarly, for liquid coupled stream, on that of liquid side withdrawal when the fraction of side withdrawal is fixed, and a smaller effect when the quantity of side withdrawal is fixed.
    Additional Material: 6 Ill.
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  • 30
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 196-202 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Random Crystal Growth (RCG)model is proposed to predict CSD in a continuous MSMPR crystallizer when the crystals exhibit growth rate dispersion. RCG model links two well-known models of growth rate dispersion, namely the Random Fluctuation (RF) and Constant Crystal Growth (CCG) Models. Monte Carlo simulation has been employed to solve the model equations. Predicted results are compared with experimental CSD data on sucrose reported by Bennett.
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  • 31
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The well-known formulae for efficiency and mean temperature difference of a heat exchanger as functions of its numbers of transfer units, or dimensionless lengths, can be written in a more compact form by introducing the auxiliary function ϕ(x) = x/(1 - e-x). The resulting new formulae show a number of advantages: They are shorter, easier to memorize, and in many cases the limiting values can be seen more directly. They may therefore contribute to easier and faster heat exchanger design, and to reduced probability of errors in the relevant calculations.
    Additional Material: 3 Ill.
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  • 32
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 258-264 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Deasphaltization of heavy crude oils and distillation residues may reduce the metal content of these oils to such an extend that the upgrading of deasphaltized oil in a catalytic process becomes economically feasible. Experimental results of deasphaltization of Boscan crude from Venezuela, using subcritical and supercritical carbon dioxide as deasphaltizing agent, are presented. Deasphaltization and demetalling with CO2 in the supercritical state is more effective. Under favorable conditions, the deasphaltized oil contains practically no asphaltenes and the metal content is reduced by 690 wt-%. The influence of n-heptane or n-pentane addition to the crude, which lowers viscosity and promotes flocculation, is also discussed. Furthermore, a multistage deasphaltization process is more efficient than a single stage process.
    Additional Material: 14 Ill.
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  • 33
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 277-288 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The present paper is a case study of an application of sensitivity analysis in chemical kinetics. Emphasis is laid upon chemical interpretation of sensitivity information and on identification of the most important model important model parameters. The kinetic model for reforming of C6 hydrocarbons proposed by Mobil [14] is extended to the analysis of the behavior of n-hexane conversion in an adiabatic reactor. The importance of six initial conditions (feed composition and initial temperature) is analyzed by the computation of normalized first order sensitivity gradients (y1o/y) (δyi/δy1o). The relative importance of 21 model parameters αj is estimated by the computation of normalized sensitivity gradients of the type (αj/yi) (δyi/δαj). The influence of the decisive model parameters ΔH6o and ΔH3o (activation enthalpies of benzene hydrogenation and methyl cyclopentane isomerization, respectively) as well as operating parameters is presented. The problem of uncertainly in the value of ΔH6o and its influence on the model solution is also sown. Finally, some advantages of the application of normalized gradients of the explanation of process behavior are discussed.
    Additional Material: 11 Ill.
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  • 34
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 319-322 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model based on experimental results is set up for a typical model reaction of hydrocarbon reforming, namely the dehydroisomerization of methyl cyclopentane. Computer simulations shows that the existing theory about the reaction path of hydrocracking reactions involving bifunctional catalysts may be only partly valid.
    Additional Material: 6 Ill.
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  • 35
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 322-327 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Deposition of particles from gas flows on ribbons in normally expected on the front side. Collision efficiencies of ribbons are presented for this case, obtained by means of single particle trajectory computation, which is based on numerically determined flow fields in the Reynolds number range between 2 and 50 and on the potential flow model. Further, it is shown, that deposition of particles on the rear side can be caused by eddylike motion of the fluid in the wake of the ribbon. For this to occur, two conditions must be fulfilled: the free shear layer between the wake and the outer flow must be turbulent to cause lateral transfer of particles into the wake and the Stokes number may not exceed 0.5.
    Additional Material: 6 Ill.
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  • 36
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 371-375 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A solution of 0.1 M 1,2-dichloroethane in 1 M H2SO4 was anodically converted to CO2, Cl2 and HCIO4 as the main products at smooth platinum. The current efficiency for CO2 exceeds 60% at low current densities, while HClO4 is obtained with about 20% current efficiency. Chlorinated products such as 1,2′,2-trichloroethane are formed in negligible amounts. Platinum plays a distinctive role as anode material and shows a reaction limited anodic prewave. Our experimental findings lead to a mechanism, whereby DCE is initially hydroxylated to form chloroacetaldehyde chlorohydrin which releases HCl and becomes rapidly further oxidized to monochloroacetic acid. The cleavage of the C—C bond proceeds via its anodic decarboxylation. Possible practical applications in the field of anodic water purification and in the direct electrosynthesis of vinyl chloride are discussed.
    Additional Material: 6 Ill.
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  • 37
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The collection of reactive and therefore extremely adhesive and cohesive fine particles (〈 1 μm) by means of bag filters with pulse-jet cleaning may present problems. The electron-beam dry scrubbing (EBDS) process, used to remove SO2 and Nox in a power plant of the Badenwerk AG, Karlsruhe, serves as an example. To solve the occurring problems and achieve a satisfactory filter performance, extensive know-how of process engineering is necessary. This contribution deal with the following aspects: construction of the cleaning system, selection of filter medium, precoating, and dosage of an auxiliary dust during filtration.
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  • 38
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Holographic interferometry is used for the determination of surface deformation of items of equipment. The material failure which caused the surface deformation can then be identified. Because a double-pulsed laser is used to plot the hologram, non-vibration stabilized holographic equipment is necessary. Thus, non-destructive testing of equipment components is also possible during plant operation. In this report, we present the experimental results of non-destructive testing of composite materials. We examined centrifugally cast pipes and filament wound pipes, which were made from glass fibre reinforced plastic and carbon fibre reinforced graphite. As a rule, the severity of failure is characterized by the apparent perturbation of its holographically stored fringe pattern. In this report, we present the experimental results which yield the relationship between the perturbation of interference fringes and the extent of the specific types of failure. Measurement results were compared with displacements calculated by the finite element method. By using the interferogram, and with the knowledge of tension stress beneath the surface, the size of the crack can be estimated. The size of the smallest detectable flaw was clearly smaller than the critical flaw size. Thus, holographic interferometry is suitable for detecting damage to cylindrical containers.
    Additional Material: 15 Ill.
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  • 39
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This contribution reports on the breakthrough behaviour of binary gas mixtures with ideal and non-ideal multicomponent adsorption equilibria. Investigations were carried out on mixtures CO2/C2H4 and C2H4/C2H6, both adsorbed on molecular sieve 5A (ms5A). The adsorption equilibrium of the system CO2/C2H4/ms5A may exhibit azeotropic behaviour, which subsides with decreasing active pressure (= sum of partial pressures of adsorbable components) or on raising the temperature. In contrast, the system C2H4/C2H6/ms5A maintains its ideal behaviour also at higher active pressures or lower temperatures. Attempts to calculate the non-ideal adsorption equilibrium from measured single component isotherms have failed when known models were applied. The investigation of the effect of azeotropic equilibrium on the fixed bed adsorption led to intersecting breakthrough curves of the two components. This behaviour is due to a displacement of equilibrium caused by the change in the active pressure and partial pressures, and a superposed temperature effect. This can be shown by calculating the breakthrough curves with the equilibrium model.
    Additional Material: 9 Ill.
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  • 40
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the first part of this contribution, a mathematical model was presented for a liquid fluidized bed using immobilized enzymes, with reversible Michaelis-Menten kinetics. This part is focused on the experimental results. The reaction kinetics of native and immobilized enzymes was determined in continuous stirred tank reactors under comparable conditions. The influence of external mass transfer was investigated in a fixed bed reactor column. The extend of pore diffusional resistance was examined in a continuous stirred tank reactor and with a numerical simulation. Hydrodynamics was measured in different reactor columns (diameter dt = 0.052 - 0.225 m; length L: 1.0-2.0m) and with a static mixer. Further, the concentration profile was determined in a fluidized bed reactor with side stream analysis for different biocatalyst samples, fluid velocities and bed heights. The simulation of experimental results indicates that they are well described by the developed model. Furthermore, the model is well suited to predicting the influence of specific parameters on the effective kinetics of the biocatalyst and the expansion of the fluidized bed.
    Additional Material: 8 Ill.
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  • 41
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    Chemical Engineering & Technology - CET 13 (1990), S. 97-101 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Laboratory-scale measurements were performed on the absorption of NO2 gas into diluted nitric acid. The concentration of NO2 gas, which represents an NO2/N2O4 equilibrium, varied from 1000 to 20000 ppm, the carrier gas being nitrogen. The concentration of nitric acid ranged from 15 to 60 mass-%. The absorption experiments were carried out in a double stirred cell, with a defined gas/liquid interface as the mass transfer area. The liquid phase was conducted periodically and the gas phase continuously. Mass flow rates were determined. The well-known film model of absorption was used for analyzing the experimental results. Only the N2O4 species was considered to pass the gas/liquid interface. The measured data yielded values of HN2O4(k D1)1/2 as well as their variation with temperature and nitric acid concentration.
    Additional Material: 5 Ill.
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  • 42
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The BF-Uhde-Mitsui Process uses active coke for SO2- and NOx-removal from flue gases in the temperature range between 100 and 190 °C, Experimental methods of thermal regeneration were applied to the evaluation of the state of the adsorbent after use in flue gas cleaning and of the parameters for disrober design. A reaction model was derived from experiments carried out in differential and back-mix reactors. The parameters were evaluated by adaptation of the model to the adsorption spectra. The model was successfully applied to the regeneration of active coke in a fluidized bed reactor.
    Additional Material: 16 Ill.
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  • 43
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 113-118 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The hydrodynamic and mass transfer characteristics in countercurrent, cocurrent and liquid batch operations with various Newtonian liquids were studied experimentally using the same bubble column. Taking the effect of gas sparger geometries, operating variables and liquid properties into account, empirical correlations were obtained for the gas hold-up and the volumetric liquid-phase mass transfer coefficient.
    Additional Material: 8 Ill.
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  • 44
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 125-130 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Critical temperatures and pressures have been determined experimentally for the four lowest n-alcohols, 2-propanol, 2-butanol, and 2-methyl-1-propanol, and are given in the penultimate line of Table 3. The last line of Table 3 lists the weighted mean critical pressures, with the corresponding critical temperatures obtained from he vapour pressure equation. Comparison with the corresponding data from standard reference books reveals deviations from the experimental data in some [2, 4] and incorrect critical pressure for ethanol in all five reference books quoted in Table 3. In addition, vapour pressure data were obtained for the same alcohols in the temperature range approaching the critical point. The measurements are reproduced by the simplified Clausius-Clapeyron equation with the constants and standard deviation given in Table 2.
    Additional Material: 4 Ill.
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  • 45
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 131-135 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The sulphur dioxide to sulphur trioxide oxidation process in a fixed bed catalytic reactor is simulated in the case of cyclic change in the direction of the reaction mixture feed. It is shown that, for transient condition, the amount of catalyst in the reactor may be substantially reduced by its partial substitution with inert material of suitable form, dimensions and thermophysical properties, at the end of the layer. This makes the direct regenerative heat transfer process in these zones controllable, producing the same conversion and overall height of the layer. The results are significant for sulphuric acid production from gases poor in sulphur dioxide.
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  • 46
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 136-143 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For the dimensioning of condensers in film condensation, the heat transfer coefficient between film surface and cooled tube wall must be known. Generally, Nusselt equations are used which have been verified by experiments. When there is no significant gas flow, a large number of equations correlate the experimental. data very well. The description of heat transfer enhancement by a significant gas flow is not sufficiently covered by the available literature. For film wise condensation in a vertical tube, a calculation method is presented which reproduces this phenomenon characterized by the interfacial shear stress at the film surface. This method is based on the assumption that, in the proximity of gas flow, the condensation process also affects the interfacial shear stress. A comparison with known experimental local Nusselt numbers showed a good agreement with water as the fluid. For test fluid MWA, which was used by Blangetti, the measured values show only a moderate agreement with theoretical calculations. Possibly, this is related to entertainment which occurred during measurements at film Reynolds numbers of over 80.
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  • 47
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 150-156 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental set-up is presented for the measurement of steady-state reaction rates in the liquid phase methyl tertiary butyl ether (MTBE) synthesis from isobutene and methanol using ion exchange resin as catalyst. This apparatus was used for a separate investigation of the main side reaction, i.e., the formation of isobutene dimers (DIB), in the temperature range between 60 and 90°C. The reaction catalyzed by Amberlyst 15 (A15) showed no steady-state behaviour, but the catalytic activity declined at a rate dependent on the reaction conditions. Time constants for activity loss were determined in the range from 3.5 to 30 h. The deactivated A15 catalyst could be regenerated through MTBE synthesis experiment. Deactivation is assumed to be caused by blocking of the microparticle gel phase by higher isobutene oligomers. The DIB formation, using 1-butene as solvent, was of 2nd order with respect to isobutene and showed an apparent activation energy of about 40 kJ/mol.
    Additional Material: 8 Ill.
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  • 48
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 161-171 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Knowledge of modelling and computer simulation is an essential prerequisite for type design and operation of packed bed systems. Unfortunately, the existing models are based on a number of weak assumptions of which plug flow can be considered as a common deficiency. Such a simplification would inevitably have a noticeable bearing on the accuracy of the final design and consequently calls for the development of a coherent mathematical description of the packed bed systems so that reliable design information can be explored. A two-dimensional heterogeneous transient model has been developed which allows for the radial variations of velocity and void age. The model equations have been solved using numerical approximation. The simulated results reveal significant differences between the present refined data and those established from existing plug flow models.
    Additional Material: 11 Ill.
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  • 49
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many experimental studies reveal that suspended solids considerably alter the coalescence behaviour and hydrodynamic functions of wo-phase flow. But no systematic efforts have yet been undertaken to separate the effects of different particle properties on local gas hold-up, bubble size and interfacial area gas/liquid. The aim of this paper is to present the local values of these parameters in three-phase fluidized beds of different solids, using miniaturized optical fiber and conductivity needle probes. It is shown that particle concentration, size and, in particular, density are decisive for the change in coalescence behaviour. Ranges of normal (ϱS 〉 ϱL) and inverse fluidization (ϱS 〈 ϱL) must be distinguished and the flow regime also exerts a strong influence on the interactions between the dispersed phases, the transition point itself being a function of particle properties can be observed, This effect is evaluated for different column diameters, between 0.1 and 0.3 m.
    Additional Material: 13 Ill.
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  • 50
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aerated emulsions are gaining significance in fermentation as well as in inorganic and organic chemistry. In these processes, liquid-liquid mass transfer can be the limiting step. Therefore, the effect of gassing rate on droplet size was investigated as a function of dispersed liquid phase concentration and power input in different vessels. At high power inputs, the droplet size decreased. With increasing dispersed phase concentration and gassing rate, the droplet size increased and its dependence on power input subsided.
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  • 51
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    Chemical Engineering & Technology - CET 13 (1990), S. 214-220 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental investigations of thermal bulk polymerization of styrene in pilot plants of different sizes have been performed. Each pilot plant is composed of a tubular recycle reactor, connected in series with a tubular reactor, both completely filled with Sulzer motionless mixers. Kinetic, reactor and viscosity models have been verified in a wide range of styrene conversions (up to 96%) temperatures (up to 210 °C) and polystyrene molar masses (up to 360 000). Scale-up studies were carried out which confirmed that multitubular reactors of special design can be applied for industrial polymerization process.
    Additional Material: 11 Ill.
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  • 52
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Warm concentrated industrial wastewaters are preferably treated in an anaerobic reactor for reasons of energy generation and low surplus sludge production. Problems to be solved in the practical application concern a low growth rate of the micro-organisms, their low settling rate, process instability and the need for after treatment of the noxious anaerobic effluent which often contains NH4+ and HS-. The use of biomass immobilized on small suspended carriers (〈 0.5 mm) has proven to be a suitable means to overcome most of these problems. Results are presented on pilot and full-scale pretreatment of industrial wastewater in an anaerobic 2-state fluidized bed reactor for CH4-production and laboratory and pilot scale post-treatment of the anaerobic effluent, which contains NH4+ and HS- in an aerobic air-lift suspension reactor for the production of NO3- and SO42-.
    Additional Material: 13 Ill.
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  • 53
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The production of dioxins/furans during waste incineration, and particularly the development of measures for minimizing the amount of generated pollutants, continue to command a considerable scientific as well public interest. Experiments are reported which were performed at the TAMARA municipal solid waste pilot incineration, erected on the premises of the karlsruhe Nuclear Research Centre. These experiments show that the solid waste mass flow rate and moisture content influence the dioxin/furan formation, Good removal efficiencies of dioxins/furans have been In wet cleaning. Hydrogen peroxide added to the crude gas is an interesting “killer” reagent for dioxins/furans.
    Additional Material: 8 Ill.
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  • 54
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    Chemical Engineering & Technology - CET 13 (1990), S. 251-258 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Regeneration of diesel particulate filters can be accomplished by complete combustion of a collected particulate. A reactor has been developed for study of the regeneration in the presence of catalysts, additives and ignition aids. This reactor allows an accurate measurement of soot ignition temperatures and a kinetic study of soot oxidation with an undisturbed soot layer and under a defined gas composition. Results of various investigations carried out with this reactor are presented.
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  • 55
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    Chemical Engineering & Technology - CET 13 (1990), S. 273-277 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The majority of the fluidized-bed reactor models are models are rooted in the tacit assumption that transport between the bubble, cloud, and emulsion phases occurs in series with chemical reaction. A more realistic model that anticipates simultaneous transport and reaction is presented in terms of a fluid-bed effectiveness factor which embraces the limits between chemical and mass transport control. Analysis of the predictive capacity of this model vis-a-vis the Kunii-Levenspiel model reveals signal differences in chemical conversion.
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  • 56
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    Chemical Engineering & Technology - CET 13 (1990), S. 384-392 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Simultaneous measurements of power consumption P and heat transfer coefficient α for a jacketed, baffled, agitated vessel of diameter D = 0.45 m, equipped with a conical turbine, were carried out. The following geometric parameters of the agitator were tested: diameter d, blade width b and number Z, and distance from the bottom of the vessel to the lower edge of the blade h. The results of these investigations were generalized mathematically. On the basis of optimization, the best geometric parameters with respect to heat transfer are proposed for the conical turbine agitator.
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  • 57
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    Chemical Engineering & Technology - CET 13 (1990), S. 422-425 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Markov process approach, as used in the modelling of particle residence time distribution in a flow system of interlinked compartments, has been compared with the deterministic model of a complex reaction system of the first order. In the latter model, interfacial reactions take place between flowing phases, corresponding to the compartments in the stochastic model. It has been demonstrated that the two approaches are equivalent. A direct method of calculating the higher moments of the residence time distribution has been verified.
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  • 58
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    Chemical Engineering & Technology - CET 13 (1990), S. 426-431 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A general model is proposed to predict the crystal size distribution from multistage MSMPR Crystallizers taking into account shape factor, birth size and growth rate dispersions. Two cases, namely nucleation in the first crystallizer and the same process in all crystallizers have been considered. The developed equations can be solved easily by the Monte Carlo technique. The model represents an extension of the earlier work of Sen Gupta and Dutta.
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  • 59
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    Chemical Engineering & Technology - CET 10 (1987) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 60
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    Chemical Engineering & Technology - CET 10 (1987), S. 33-37 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: All the present experiments confirm that there is some liquid channelling on trays. Liquid channelling is extensive on trays of large diameters. It largely depends on the tilting of the plate, modifications of the inlet weirs and on non-uniform bubble cap spacing. Consequences of liquid channelling for plate efficiency are clear; the higher the degree of liquid channelling the lower the plate efficiency. However, own experimental and theoretical investigations indicate that plate efficiency never falls below the value of point efficiency. Therefore, liquid channelling only affects the crossflow on trays. Liquid channelling reduces the mass transfer performance to a similar extent as does the backmixing of liquid. Consequently, plate efficiency is not very sensitive to liquid channelling. Since the liquid is completely mixed in the downcomer, the effects of liquid channelling are restricted to a single tray. The behaviour of tray columns completely differs from that of packed columns, where the effects of liquid channelling are cumulative over the packed height. Consequently, trays represent a suitable design for columns of large diameters.
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  • 61
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    Chemical Engineering & Technology - CET 10 (1987), S. 16-27 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Although carbon dixoide is important as an abundant carbonaceous raw material, so far, its utilization in chemical processes has been rather limited. This review covers the reactions of CO2 employed in industry, such as the production of urea, the Kolbe-Schmitt reaction, the synthesis of cyclic organic carbonates and the use of CO2 in methanol synthesis. Interesting recent developments in CO2 chemistry, such as the reactions catalyzed by transition metals, are also described. Apart from the synthesis of polymers and hydrocarbons, the production of oxygen-containing substances appears to be very profitable and attractive for future industrial applications. Not only can derivatives of formic and carbonic acids be produced but also longer-chain carboxylic acids and their derivatives by reactions of carbon dioxide with hydrocarbons such as alkynes, alkenes and 1,3-dienes.
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  • 62
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The present contribution illustrates a way of developing a continuous separation process for near critical fluid extraction, on the example of separation of soya oil from lecithin. First, a suitable solvent was selected. Phase equilibria were measured in autoclaves. Operating conditions for a pilot plant were derived from the phase equilibrium data. The pilot plant experiments provided the necessary data for designing a production plant. Computer programs for phase equilibrium, stage to stage and mass and heat balance calculations were used in order to minimize the number of experiments. A production plant with a capacity of 500 t/a of raw lecithin was designed on the basis of experimental and computational results. A cost estimation, based on tenders, showed that it is more economical to produce lecithin by near critical fluid extraction than by conventional acetone extraction.
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  • 63
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    Chemical Engineering & Technology - CET 10 (1987), S. 56-63 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ideal flow conditions are generally assumed for the reactor design. If stoichiometry, reaction mechanism and kinetics are known, the balance equations for the ideal flow tube, the ideal steady-state continuous stirred tank reactor or the ideal, completely mixed stirred batch reactor are often applied. In many cases, formal kinetics, which forms the basis of reaction modelling, is so uncertain that the idealization of the flow field can be accepted. In practice, however, deviations from the ideally calculated conversions, yields and product qualities, often occur. In these cases, it is necessary to consider the real flow conditions. In general, a distinction is made between macroand micromixing processes.
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  • 64
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    Chemical Engineering & Technology - CET 10 (1987), S. 1-15 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using pilot-scale test plant, the interfacial area per unit volume was investigated in different gasliquid reactors, i.e. packed column, bubble column and free jet reactor. The interfacial area was studied as a function of liquid viscosity and of operating parameters. As a rule, identical test conditions were maintained in all the measurements, in order to obtain comparable results. The interfacial area was determined by chemical means using the sulphite system (a solution of sodium sulphite in water as model liquid and air as gaseous medium). The viscosity of the solution can be increased by adding carboxymethyl cellulose without significantly affecting the reaction kinetics. The addition of a surfactant to the sulphite system allowed comparative measurements at reduced surface tension. Based on a large number of measurements, the correlations of the interfacial area are expressed as power laws. The inclusion of experiments with a jet tube reactor and a stirring vessel allows an extensive comparison of all reactors. All tests were carried out with the same material system and the same method was used to determine the interfacial area per unit volume. Therefore, a comparison with respect to mass transfer is possible.
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  • 65
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    Chemical Engineering & Technology - CET 10 (1987), S. 27-32 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new measurement method for determining the local liquid-phase velocities in multiphase flows is presented. It is based on a tracer technique, using heat introduced into the flow, seemingly at random, instead of a material tracer. The input of heat pulses and measurement of temperature at an adjacent point is performed by small probes. As an intermediate result, the flow time distribution of the heat-labelled fluid elements is calculated on-line as a cross-correlation function between the pseudo-random input and the measured output signals. This calculation and the automatic control of measurements is carried out by a simple microprocessor unit. The device produced excellent results in gas-liquid flows at high gas throughputs and high liquid-phase velocities.
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  • 66
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    Chemical Engineering & Technology - CET 10 (1987), S. 63-72 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Among other processes, adsorption is used for the removal of hydrogen sulphide from natural gases. Hereby, competitive adsorption of the different gas components plays an important role, e.g., that of carbon dioxide. Data of equilibrium loading and adsorption kinetics are required for the design of adsorbers, filled with molecular sieve. In order to obtain these data under the prevailing operating conditions, hydrogen sulphide was removed from gas mixtures H2S/CH4 and H2S/CO2/CH4, in a pilot plant, by adsorption on molecular sieve 5A. The equilibrium loading, the height of transfer zone, and the length of unused bed were determined from the measured breakthrough curves of H2S. With these data, the breakthrough time and the optimum process conditions were calculated for a practical example.
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  • 67
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    Chemical Engineering & Technology - CET 10 (1987), S. 43-55 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxidation of carbon monoxide by air in a turbulent flow was investigated under experimental conditions where the rates of turbulent mixing and of chemical reaction are comparable. For this purpose, carbon monoxide was admixed into the completely burnt gas of a natural gas flame operated with excess of air. Measurements of mean values of axial velocity, temperature and volume fractions of carbon monoxide and oxygen were compared with computational simulations involving the k - ∊ turbulence model and several turbulent reaction models for the oxidation of carbon monoxide. The comparison of measurements and numerical calculations demonstrated that the k - ∊ turbulence model is suitable for prediction of the turbulent flow field in the flow system investigated. Furthermore, it could be shown that one-variable turbulent reaction models, such as the flamesheet or the eddy-break-up model, cannot explain the measured carbon monoxide volume fraction profiles. Two-variable turbulent reaction models with a probability density function closure of the source term of the transport equation for the mass fraction of the chemical species result in a better agreement between the measured and simulated volume fraction profiles, particularly in predicting the clear influence of the initial temperature on carbon monoxide volume fractions. Weighting of the kinetic rate expression for the oxidation of carbon monoxide with different presumed probability density functions yields slightly different predictions of the carbon monoxide volume fractions, reflecting the assumed different character of turbulent fluctuations.
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  • 68
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    Chemical Engineering & Technology - CET 10 (1987), S. 92-98 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Distillation columns with vertical partitions can separate a feed mixture into 3 or 4 pure fractions. Compared to other column arrangements, their investment costs and energy consumption are lower. Production columns show good results and are easily controlled. Conventional distillation columns produce only 2 pure product streams at the top and at the bottom of the column. Side products are contaminated by light or heavy components, depending on the location of the side stream in the rectifying or stripping section. This disadvantage is set aside by using a distillation column with a vertical partition. The internal separation wall prevents lateral mixing of liquid and vapour in the central part of the column, forming there separate feed and outlet sections. In the presence of a vertical partition, 3 or 4 pure fractions can be obtained in a single distillation step. This is particularly advantageous when heat sensitive components are to be separated. On account of good thermodynamic properties, the energy consumption is 20 to 35% lower than that of other distillation arrangements. The control behaviour is similar or better than that of conventional distillation columns.
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  • 69
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    Chemical Engineering & Technology - CET 10 (1987), S. 86-92 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Carman-Arnell equation relates the rate of flow of a fluid through a packed bed to the pressure drop across the bed. This equation is the basis for surface area determination by permeametry. It is found that the surface area measured at sub-atmospheric pressure varies with the bed porosity, so a porosity was selected where the rate of change was at a minimum. The study suggests that, at reduced pressures, the gas flow rate is a linear function of the mean pressure.
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  • 70
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    Chemical Engineering & Technology - CET 10 (1987), S. 104-112 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A 0.5 MW spray-dry scrubbing FGD pilot plant was used in the study of spray dryer performance over a wide range of operating conditions. Experimental findings were compared with a spray dryer model. During operation with large excesses of lime, the SO2 absorption was limited by gas phase diffusion. At operation with a shortage of lime, the rate limiting step was the dissolution rate of lime. In addition, the flow regime in a spray dryer can be best described as well mixed. The SO2 level in the flue gas was found to exert no direct effect on the efficiency of SO2 removal. The observed effects are attributed solely to the changes in the drying process, due to the inter-dependence of slurry composition and SO2 concentration.
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  • 71
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    Chemical Engineering & Technology - CET 10 (1987), S. 73-86 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: As a part of a research project on the mass transfer in liquid pulsed sieve-tray extraction columns (PSE), the diameters and hold-ups of the drops were measured: the drop size using a suction technique, with photoelectric detection, which was adapted to the special boundary conditions of the PSE; the integral hold-up by the pressure difference between the lower and upper parts of the column. Since experimental results cannot be described by known calculation formulae for the Sauter mean diameter and the hold-up, a new method of calculation was developed. It is phenomenologically based on high-speed photographs of the drop motion on a sieve tray. The mathematical-physical model allows the prediction of drop size and hold-up within certain limits, while the possible different operating regimes of the PSE, i.e. the mixer-settler and dispersion regimes can also be estimated.
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  • 72
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    Chemical Engineering & Technology - CET 10 (1987), S. 125-131 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When crude oil is vacuum distilled, about 30% of the feed remain as low value residue. Hydrocracking can upgrade this residue into valuable light hydrocarbons. The hydrocracking could be optimized catalytically, if the residue were not to contain the metals vanadium and nickel that poison the catalyst. This contribution shows that continuous extraction of the residue with ethyl acetate yields a fraction with low metal content, while an asphaltene fraction with the remaining metal content is filtered off.
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  • 73
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A one-stage model of the formation of primary bubbles is presented in which the bubble volume is deduced from an equilibrium of buoyancy, viscosity, inertia and surface tension forces. In contrast to the two-stage model, presented by Kumar and Kuloor, it was not assumed that the drag coefficient in bubble expansion can be described by the same constants as in the steady-state bubble ascent. The constants were adapted in such a way that the introduction of an additional bubble volume was not necessary. It was demonstrated that this model describes the bubble formation in gravitational and centrifugal fields equally well and, furthermore, is also applicable to structurally viscous liquids, provided that the effective shear gradient \documentclass{article}\pagestyle{empty}\begin{document}$$ \mathop {\rm \gamma }\limits^. = \frac{1}{6}({\rm \Delta \rho }gzd_{\rm B} /{\rm \eta }) $$\end{document} is calculated from the equilibrium of shearing and buoyancy forces. The model is based on the assumption of a constant volumetric flow rate during bubble formation and, for this reason, a minimum Froude number is necessary in analogy to the weeping limit for sieve plates. The normalized presentation permits simple operation. The possibility of applying the model to drop formation was confirmed by comparison of experimental values with those, predicted by the model.
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  • 74
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new equipment for the measurement of virial coefficients of pure substances and binary mixtures is described. It consists of an improved modification of the set-up proposed by Eucken and Meyer in 1929. The development is based on a critical review of the existing methods particularly with respect to adsorption effects. In order to reduce the influence of adsorption on the accuracy of virial coefficients, an optimum range for gas density is recommended. The accuracy of the virial coefficients is better than 20 cm3 mol-1. The set-up was employed for the measurement of virial coefficients of acetone and hexane in the range from 352.95 to 393.85 K. The results are in excellent agreement with data published in literature. Furthermore, cross-virial coefficients of the binary system acetone/hexane were measured and interpreted.
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  • 75
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    Chemical Engineering & Technology - CET 10 (1987), S. 113-125 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fouling and/or scaling of heat transfer surfaces causes serious problems in industry. Prevention of fouling is therefore essential for technical (considerable deterioration of heat transfer) and also economic reasons (increased costs). In order to provide successful countermeasures, it is, however, necessary to obtain more detailed information on the physical, chemical and biological processes which produce fouling. Based on the already known fouling mechanisms, it is shown that a satisfactory prediction of fouling behaviour of heat exchangers is not yet possible. This contribution presents a physical model for the description of fouling, caused by sedimentation and crystallization. It is assumed that, during fouling, deposition and removal processes overlap. In order to verify the theoretical considerations, experiments were carried out on a test rig, which could also be used for field experiments. Aqueous CaSO4 solutions served as experimental liquids. A comparison of experimental and calculated fouling factors shows a satisfactory agreement.
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  • 76
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    Chemical Engineering & Technology - CET 10 (1987), S. 157-164 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Based on a paper by Hein, a dimensioning program for tube-bundle heat exchangers with straight tubes and fixed tube sheets has been developed. The equipment to be dimensioned is tested at 14 critical points, with regard to permissible stresses. The optimum thickness of the tube sheet, the shell and channel are subsequently selected on the basis of economic criteria. Compared to dimensioning according to AD-data sheet, it is possible to save between 10 and 25% of production costs. With the aid of a finite-element (FE) program, complex structures such as heat exchangers can be calculated accurately. Several mesh-generation programs were written for the data input. The structure of a tube-bundle heat exchanger with straight tubes is generated with 3/D elements with only some geometrical data. An FE-calculation of a heat exchanger is explained with the aid of an example and stress analysis is presented.
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  • 77
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The present contribution reports on a new method for the simulation of the dispersed phase behaviour in liquid-liquid extraction columns. The fluid dynamic description is based on a mathematical model which explicitly takes into account drop transport, break-up and coalescence mechanisms, via a drop population balance along the column. Application of the model requires some simple measurements on single drops in order to determine transport and break-up laws, which are required by the model, and possibly also coalescence parameters. In this study the model is applied to pulsed sieve plate columns. The specific example considered here is based on systematic studies on the determination of break-up rates from the corresponding probabilities of break-up and the generated daughter drop size distributions by means of high-speed photography. The validity of the model was subsequently tested by comparison with some experimental results from studies on two different pulsed columns 80 and 225 mm in diameter for the water/toluene system without mass transfer. The satisfactory agreement between the results justifies the use of such a method for the description of the behaviour of liquid-liquid extraction columns in a wide range of operating conditions. Furthermore, application of the model may help to dispense with long and expensive pilot tests.
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  • 78
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Microbial desulphurization of coal by pyrite oxidizing enrichment cultures containing predominantly Thiobacillus ferrooxidans was performed in an air-agitated slurry reactor, 20 l in volume. A model of microbiological and chemical reactions, occurring at various points within the coal, was set up taking into account the pore structure of the coal. The influence of parameters relevant to industrial processes, such as superficial gas velocity, particle size, initial pyrite concentration, and slurry density of the coal, on the conversion of pyrite was examined. Variation of the superficial gas velocity in the range of 0.01 to 0.04 m/s confirmed that the reaction is not controlled by oxygen transfer from gaseous to liquid phase. The rate of pyrite oxidation depends mainly on the accessibility of pyrite to micro-organisms which is determined by the particle size of the coal as well as the distribution of pyrite crystals in the coal matrix. The accessibility of pyrite to the micro-organisms is described by the ratio of effective to maximum microbial activity, measured as oxygen consumption. Starting with higher initial concentration of pyrite in the coal increases the oxidation rate, according to first order kinetics. Enhanced slurry densities lead to a decrease of pyrite conversion, in spite of higher pyrite concentration. The maximum pyrite oxidation rate was measured at 15% (v/v) slurry density and 25°C as 1800 mg Spyr/kg coal per day, or 360 mg Spyr/l reactor volume per day.
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  • 79
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    Chemical Engineering & Technology - CET 10 (1987), S. 131-142 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of electrolytes, which are dissolved in the aqueous absorbent and do not react with nitrogen oxides, on the absorption kinetics of both these components was investigated experimentally. In addition to demineralized water, various salt solutions of different concentrations as well as sodium hydroxide solution were used as absorbents. The term H \documentclass{article}\pagestyle{empty}\begin{document}$ H\sqrt {k_1 D} $\end{document} for N2O4 and N2O3, which is important for the design of industrial absorbers, was determined as a function of composition and concentration of the absorbents. In the case of N2O4, the chosen measuring and evaluation methods permitted a separate determination of the rate constant k of the pseudo first order reaction and of the solubility H. The diffusion coefficient D of the gas in the absorbent can be obtained only by calculation. Experimental results showed that \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 4} } $\end{document} decreases with increasing ionic strength I, however, without a clear indication of any ion-specific effects. This decrease does not appear to be caused simply by a reduction in solubility (salting out effect), or in diffusion coefficient, but at least, to the same extent, through a decrease of the rate constant k with increasing electrolyte content in the absorbent. The measurements permitted the determination of the gas-based salting out parameter for N2O4. The investigations on the absorption of N2O3 in water and in an Na2SO4 solution showed no experimentally detectable influence of dissolved salts on \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 3} } $\end{document}. The numerical value of \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 3} } $\end{document} is six times that of \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 4} } $\end{document}.
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  • 80
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Slurry bubble columns are widely used in biotechnology. Therefore, the effects of solid particles on fluidization characteristics, gas hold-up and volumetric liquid-side mass transfer coefficient were measured in a slurry bubble column (i.d. 0.14 m). The density and diameter of the suspended particles were similar to those applied in biotechnology with immobilized bacteria. Based on models of turbulence and of liquid circulation induced by rising gas bubbles, equations for critical gas velocity, gas hold-up and volumetric liquid-side mass transfer coefficient were obtained by dimensional analysis.
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  • 81
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The detailed dynamic simulation of coupled process units in chemical plants is gaining an increasing importance as a useful tool in plant engineering and operation. The outline of the program package DIVA (Dynamische Simulation verfahrenstechnischer Anlagen) which is currently under development is presented in the following. The dynamic plant equations and the corresponding Jacobian matrix are generated automatically. The full exploitation of sparse matrix techniques in combination with stiff ODE (ordinary differential equation) solvers allows an efficient solution of all the equations simultaneously. The possibilities offered by the simulator are demonstrated by the simulation of two laboratory plants.
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  • 82
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    Chemical Engineering & Technology - CET 10 (1987), S. 190-203 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Spatially resolved oxygen concentration measurements were performed in premixed hydrocarbon flames by using laser induced spontaneous Raman scattering. The measurements demonstrate the performance of a relatively simple pulsed laser Raman probe for fundamental combustion studies and also for the control of the equivalence ratio in flames (best spatial resolution: 0.2 mm3; theoretical detection limit: 0.8% of O2). Comparison of the results with those obtained by a mechanical suction probe (Magnos 2 T) confirmed a good agreement. At present, control of different stoichiometric conditions is possible at a minimum O2 concentration of 1.3%.
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  • 83
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: During the sudden unheated vessel top venting of initially saturated two-component gas/liquid mixtures, in which the gas is also extensively dissolved in the non-evaporating liquid phase, a solubility inequilibrium develops between the phases; re-equilibration can set in only after a so-called desorption delay time. Laboratory measurements of this delay time were under-taken with model mixtures of CO2 and water and viscous aqueous (Newtonian) solutions by high speed cinematography. The parameters of the experiments are relief cross-section, initial liquid level, pressure, temperature, and concentration. The shortest deley time obtained lasts approximately 75 ms. It differs substantially from the minimum boiling delay time previously measured with various refrigerants in the same test facility. The experimental results are correlated by a semi-empirical dimensionless power relationship, which includes all independent primary design variables generally availble in a physically consistent interrelationship. Reasonable extrapolations to other test conditions and aqueous two-component systems with an acceptable accuracy systems can therefore be expected.
    Additional Material: 10 Ill.
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  • 84
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Correlations for pressure drop and upper capacity limit (flooding) are useful for the design of packed columns. Available correlations are based on the results of measurements made at atmospheric pressure. Extrapolation to higher pressures is not recommended. Therefore, systematic experimental investigations were carried out in a pilot plant at pressures of up to 100 bar. The experimental equipment and techniques, evaluation methods, and some characteristic experimental results are presented.
    Additional Material: 16 Ill.
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  • 85
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 224-230 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper describes a pilot plant for entrainment measurements on various types of column trays. The data obtained from different trays differ by up to a factor of 10. The measurements were compared with the theoretical model of Stichlmair. The Stichlmair entrainment diagram permits a fairly accurate prediction for most types of trays if the height of the two-phase layer is known. Prediction of the height and relative liquid hold-up in this two-phase system should be modified by a term reflecting the vapour flow profile, which requires further testing. These tests should examine the effect of tray spacing, fractional free area and, in particular, the influence of different media.
    Additional Material: 9 Ill.
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  • 86
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 204-215 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In three-phase systems, where the liquid constitutes the continuous phase, solid is the catalyst and gas represents the dispersed phase, there are decisive criteria which have to be observed in reactor design. These are e.g. the interfacial area per unit volume between gas and liquid, the volumetric mass transfer coefficient and the mass transfer coefficient. The basic aim of the present work was therefore the investigation of these parameters in relation to the main influencing parameters. Process parameters stirrer speed and superficial gas velocity were varied as well as the physical properties such as liquid viscosity, solids concentration, particle diameter and a geometrical parameter, i.e. reactor diameter. The sulphite method was employed for the determination of these values. The test results confirmed the known relationships of power consumption and superficial gas velocity. An increase in the liquid viscosity leads to a decrease in all the tested values. In most cases, suspended solid particles lead to a lowering of the test values. The influence of the tank diameter on the plots of the test values against specific power consumption turned out to be invariant so that a scale-up of geometrically similar systems can be carried out at constant power consumption, superficial gas velocity and liquid viscosity.
    Additional Material: 27 Ill.
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  • 87
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 242-248 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pool boiling data of multicomponent mixtures show that the heat transfer coefficients can be considerably lower than those of a corresponding pure fluid with the same physical properties as the mixture. The proposed model, which assumes maximum mass transfer resistance in the liquid boundary layer, is confirmed by the comparison between calculated and experimental data. The model allows the prediction of heat transfer coefficients in pool boiling of mixtures using only single component properties and vapour-liquid equilibrium data. Judging by experience with a number of different systems, the method should be sufficiently accurate for most practical applications.
    Additional Material: 10 Ill.
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  • 88
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 248-255 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The development of heat resistant permeation membranes has opened up new possibilities for the conversion of fossil energy resources. In steam reforming of natural gas, such membranes even permit a direct production of hydrogen at high temperatures during the conversion of feed hydrocarbons. Further gas processing, such as required for reformer gas in existing hydrogen production processes, is not necessary. Due to continuous hydrogen discharge directly in the reformer tube, the chemical equilibrium of the occurring reactions becomes displaced towards the products, resulting in more favourable process conditions and, consequently, in improved by 36% utilization of the feed hydrocarbons. At the same time, the hydrogen yield increases by 44%. The heat required, which is provided by a high temperature reactor, is 17% in excess of that in conventional plants. It can be expected that the simplified process design will produce substantial cost advantages over the existing processes for the production of hydrogen.
    Additional Material: 14 Ill.
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  • 89
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the present paper, models are developed for the description of coalescence and splitting of bubbles in gas fluidized beds. The distinction between slow and fast bubbles, which originates from the Davidson model of gas flow in and around a rising bubble, was found to be decisive for the modelling of coalescence processes. On the basis of the respective models, it is shown that a change in bed temperature does influence the mechanisms of both bubble coalescence and splitting. In cases of both slow and fast bubbles undergoing splitting, the theory predicts a decrease of bubble size with temperature whereas in the case of a non-splitting system with fast bubbles, typically encountered with Geldart type B particles, no significant temperature effect on bubble size is expected. The theoretical predictions are shown to be in agreement with own measurements as well as with the results of other workers.
    Additional Material: 15 Ill.
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  • 90
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 262-271 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pressure pulsations in hydraulic systems, generated by reciprocating pumps, can cause serious problems with regard to plant safety and reliability. In particular, fatigue problems arise in high-pressure piping systems. The available knowledge is not sufficient for an accurate computation of pressure peaks in the piping of reciprocating pumps. A number of calculation models are available which, however, neglect both fluid compressibility and friction. This contribution presents a calculation method which allows a precise modelling of various pump installations. Comparison of calculated and experimental data shows a good agreement and provides a validation of the computational model.
    Additional Material: 18 Ill.
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  • 91
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 256-261 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the separation of gaseous mixtures by gas permeation, it is in some cases impossible to achieve the desired product quality in a single stage and, therefore, several stages may be necessary. Multistage processes can be implemented by membrane modules arranged in the form of a cascade or by a membrane column design. On the basis of an economic analysis, this paper discusses different possible module arrangements for 2 cases, i.e. the enrichment of oxygen from air and the separation of methane from biogas. Present calculations indicate that, in the first case, two-stage cascades with or without recycle and, in the second case, one-stage cascade without recycle constitute the optimum module arrangements. However, depending on the selling price of the methane enriched gas, one- or two-stage cascades with recycle have to be considered. Finally, It was shown that, in the permeation of non-ideal gases, the Joule-Thomson effect has to be taken into account.
    Additional Material: 10 Ill.
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  • 92
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 281-289 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fundamental investigations of coalescence processes in settlers with plate packages for the separation of liquid-liquid dispersions prompted an analysis of the drop motion on the interface of a stratified two-phase flow. Therefore, a physical model was developed, which permits the calculation of drop velocity along the interface of an inclined trickling film. Starting from a balance of forces around a single particle, the model provides the equation of motion for a steady motion of single particles in a stratified two-phase flow. Several assumptions and considerations were necessary to solve this equation, such as taking into account the influence of the wall and of flow resistance. The model calculation assumes Newtonian liquids and laminar, smooth trickling films. A comparison with experimental results confirms that the drop motion behaviour is well reproduced.
    Additional Material: 14 Ill.
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  • 93
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 291-296 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of extraction processes with chemical reaction was studied experimentally on the system copper/Acorga PT 5050 and quantified according to meaningful kinetic models. These were coupled with other models describing the behaviour of dispersions in columns in order to permit a computer aided simultation of reactive extraction. Thus, a better prediction of column performance is achieved.
    Additional Material: 8 Ill.
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  • 94
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 312-322 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Existing heat exchanger design criteria do not satisfy the continually increasing requirements for greater efficiency or mass flux and energy throughput. Occasionally, failures appear even after only a few hours of operation, as shown in section 3. A long series of experiments, often carried out on original scale, did lead to the derivation of a large number of empirical expressions; however, physical explanations of the complex tube-failure interactions could not as yet be found. In contrast, experiments with a well defined simple model, whereby the tube deflections were recorded digitally and, at the same time, tube-fluid interactions were registered on a high-speed film, show that elementary “fluid transport mechanisms” control the stability behaviour of the heat exchanger tubes. Vibration excitation mechanisms such as “galloping”, “jet switching” and “whirling” (fluid elastic coupling) proved, with their characteristics, as typical for the vibration behaviour of single rows within the tube array, but not for the vibration phenomena of tube bundles.
    Additional Material: 17 Ill.
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  • 95
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 297-305 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Against the background of long-term availability of natural gas, its present technology and future prospects are described. Particular emphasis is put on the oxidative coupling of methane to C2+ hydrocarbons: (1) Catalyst development, activity, selectivity and deactivation as well as reactor operation are discussed; (2) a tentative process scheme is put forward and its economics evaluated with respect to ethylene production.
    Additional Material: 8 Ill.
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  • 96
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 323-329 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The conversion of a number of alcohols, ethers, ketones, aldehydes, carboxylic acids, esters, and cyclic compounds and their mixtures on H-ZSM-5 at 673 K was investigated. These compounds can be easily converted to aromatic hydrocarbons if the C/H ratio of the molecule fragment, remaining after elimination of oxygen as water, is less than 0.62. At higher C/H ratios, coking of the catalyst increases, thus reducing its lifetime, a difficulty which can be overcome by hydrogenation of these compounds prior to their conversion over H-ZSM-5. A procedure is proposed for converting at least a part of organic waste chemicals to valuable products instead of burning them.
    Additional Material: 8 Ill.
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  • 97
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental study of the flow of phosphate mine tailings was carried out in order to characterize these suspensions of fine particles for pipeline transport. Rheological measurements with a rotating cylinder viscometer indicate a viscoplastic behaviour which can be represented by a Herschell-Bulkley or by a Casson model. The variation of the parameters of these models with solids concentration reveals a change in the behaviour at a concentration of 10 to 15%. The pressure drops were measured during flow in capillary tubes, in both laminar and turbulent regimes. The variation of the pressure drop coefficient (Fanning friction factor) as a function of the generalized Reynolds number confirms the validity of the employed rheological models. The results are in good agreement with measurements made in pipes of industrial size. The velocity profiles measured with a novel ultrasonic velocimeter demonstrate the influence of the rheological behaviour on the yield and wall stresses.
    Additional Material: 10 Ill.
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  • 98
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 330-337 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The aim of this investigation is to show the demarcation of two possible mechanisms for surface deposition of fine particles on the rear surface of single spheres. By means of single particle trajectory computation, based on numerically determined flow fields (Remax = 103), it is shown that the mere existence of a wake is not in itself sufficient to produce eddy deposition. In addition, the particle's motion must undergo a lateral transfer promoted by fluid trubulence, in order to effect eddy deposition commencing at a Reynolds number of about 100. On the other hand, rear deposition, influenced by electrostatic forces, especially by the Coulomb force, is possible at any Reynolds number. Consequently, for Reynolds numbers of less than 100, only electrostatic effects can produce rear surface deposition. In the range of high Reynolds numbers, the coexistence of both mechanisms is possible. Very high Reynolds numbers (Re 〉 103) and low Stokes numbers indicated the predominance of the electrostatic effect over eddy deposition, whereas at very high Reynolds numbers and medium to high Stokes numbers the electrostatic effect is only predominant in presence of high electrostatic charges.
    Additional Material: 12 Ill.
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  • 99
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 349-352 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simplified reactor model can be used for predicting the performance of an industrial VGO-treater. Laboratory-scale experiments performed on the same feed and catalyst as those in the industrial unit lead to a reactor simulation which agrees well with the data from this unit. In the laboratory experiments, it is possible to overcome the specific hydrodynamic problems of tricklebed reactors by appllying the catalyst dilution technique. Results obtained by this technique allowed the development of a reactor model which enables the user to simulate the adiabatic behaviour of the industrial reactor. In this way, the significant gap between the reaction temperature in the isothermal laboratory reactor and the WABT of the industrial adiabatic reactor can be bridged.
    Additional Material: 4 Ill.
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  • 100
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 361-367 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rate behaviour of multi-step reaction systems is difficult to model. Concentration-controlled investigations in a recycle reactor provide new tools for this purpose, e.g. the possibility to decompose a network into single reaction steps. Methanation of carbon monoxide over a supported Ni catalyst could be shown to be accompanied to a considerable extent by the shift reaction, and to a lesser extent by direct hydrogenation of carbon dioxide. Deactivation of the catalyst was measured at definite gas compositions. The two main steps show different responses to deactivation: Separable kinetics was found only for the methanation step. Power law rate equations were fitted to the rate data of the individual reaction steps to represent the main features of their kinetic behaviour. Some aspects of deactivation kinetics are also discussed.
    Additional Material: 8 Ill.
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