摘要:

AbstractThe parameters of lactic acid separation from fermentation broths by Emulsion‐Liquid Membranes (ELMs) have been optimized. Using these parameters, lactic acid can be separated up to 90%, concentrated up to 3 times and cleared of most of its by‐products. Only about 1% of glucose and amino acids is permeated together with the lactic acid. With these parameters, not only lactic acid but also other monocarboxylic acids can be separated, the better and faster the lower the pKa‐value of the acid the fewer polar side groups it carries. When separating dicarboxylic acids, the mass transfer is hindered by the second carboxylic group. The smaller the distance between the two carboxylic groups, the slower is the separation of the acid. When several organic acids are separated from the same fermentation broth, their mutual influence is not very strong, at least when the concentrations of the acids are about 100 mmol/l. However, sulphuric acid which is added to the fermentation broth throughout permeation to maintain the broth at a constant pH, does exert a strong influence. In order to reduce the competition between the organic and sulphuric acids during permeation to a minimum, as little as possible sulphuric acid is used. However, a certain quantity of sulphuric acid is necessary to maintain the pH of the fermentation broth during permeation at 4.5, otherwise organic acid separation would become too

ISSN:0930-7516    

DOI:10.1002/ceat.270150602

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractA two‐dimensional pseudo‐homogeneous model with axial dispersion of heat has been solved numerically with different boundary conditions at the inlet and outlet of the packed bed. The model solutions are fitted to experimental temperature profiles, determined in a wall‐cooled packed bed in which a hot gas is cooled down, and best fit values of the effective axial and radial thermal conductivities and the wall heat transfer coefficient are obtained. In the range of Reynolds numbers employed, Re sp>50, the axial dispersion of heat is found to be of no significance for the description of heat transport in wall‐cooled packed beds without reaction, provided that the inlet boundary conditions are chosen appropriately. If a radially flat inlet temperature profile is assumed, while the actual profile is curved, an apparent improvement in the description of heat transport is observed when axial dispersion is incorporated into the heat balance and high effective axial thermal conductivities are obtained. If a Danckwerts type inlet boundary condition is used, assuming a flat temperature profile immediately in front of the inlet, an apparent improvement is also found on incorporation of axial dispersion of heat. This is caused by the temperature jump at the inlet, compensating for the overestimation of inlet temperature, in the case of cooling. The latter also explains why the inclusion of axial dispersion may eliminate the so‐called “length effect”, often related to the effective radial thermal conductivity and the wall heat transfer coefficient. It is shown for the outlet boundary condition that deletion of the axial dispersion term from the heat balance at the outlet is a convenient boundary condition for the model being sol

ISSN:0930-7516    

DOI:10.1002/ceat.270150603

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractSince SLP catalysts can become irreversibly deactivated due to evaporation of the solvent used to prepare the contacts, a saturation technique is proposed to stabilize the catalysts' activity. Application of this technique requires isothermal reaction conditions which can be achieved directly in fluidized bed reactors. Although the fluidization properties of SLP catalysts are mainly determined by interparticle forces, it can be shown that this type of reactor is suitable for an SLP‐catalyzed gas reaction provided that a number of prerequisites are fulfilled. Taking a hydroformylation reaction catalyzed by an Rh complex dissolved in dimethyl glycol phthalate as an example, it is demonstrated that the activity of the prepared SLP catalyst can, indeed, be stabilized by saturation of the reactant gas mixture with the employed solven

ISSN:0930-7516    

DOI:10.1002/ceat.270150604

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractBubble properties in stirred tank bioreactors equipped with standard radial flow Rushton turbines have been investigated. Bubble velocity patterns within a stirred tank reactor were derived from measured local bubble velocity distributions. Local information on specific interfacial areas, bubble number densities and bubble diameters together with local gas hold‐ups, measured in a model medium at gas flow rates which are employed in practice, is presented. All measurements were performed with two new ultrasound pulse techniques which can be used in model as well as during real cultivation processe

ISSN:0930-7516    

DOI:10.1002/ceat.270150605

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThis work describes the development of a fuzzy estimator for determining copolymer composition (F1) in a semibatch solution copolymerization reactor. Membership functions, fuzzy ranges for input (ζ1mole fraction of monomer 1 in polymerizing mass) and output (F1mole fraction of monomer 1 in copolymer) are defined. A fuzzy rule base is constructed relating input to output, based on the operator's knowledge. A defuzzification method is selected and the non‐fuzzy values ofF1are obtained. The results are compared with the actual values ofF1which are obtained by rigorously solving the model equations of the system. The fuzzy ranges and limits for input and output are altered separately so as to test the estimator's performance. Thus obtained standard estimator is tested for other operating conditions. The developed estimator performed well also for wider operating conditio

ISSN:0930-7516    

DOI:10.1002/ceat.270150606

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractNew data are presented on the crystallization of potash alum (KAl(SO4)2·12H2O) from solution, in a continuously operating MSMPR cooling crystallizer, 61 in volume. Population density distributions were determined by sieve analysis. Highly polydispersed product was obtained, with median crystal size,L50, in the range between 264 and 607 μm. Suspension density was varied betweenmT= 7 and 98 kg/m3. The results were evaluated according to an attrition model and the obtained kinetic efficiency should be valid for other types of crystallizer

ISSN:0930-7516    

DOI:10.1002/ceat.270150607

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractA mathematical model of a packed bed distillation column is presented and applied to a binary system in a full scale industrial distillation column with structured packings. The model is reduced by orthogonal collocation to sets of ordinary differential and algebraic equations. A linearized large state space model is then obtained and further reduced by the optimal Hankel norm method in order to obtain a model of manageable size. The model is studied under three different operating conditions in order to cover the feasible operating ranges during the experiments. The experiments carried out with a monoethanolamine‐diethanolamine system show a good agreement with the model implying that a control design based on the model is satisfactory. It is also shown that the control configuration to be used can be easily analyzed by the model, since different input and output structures can be studied. Furthermore, models based on one‐film and two‐film theories are compared in the frequency domain and show that, due to its simplicity, the one‐film theory should be used in control

ISSN:0930-7516    

DOI:10.1002/ceat.270150608

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractA detailed analysis of the effect of local heat transfer distributions, which were determined experimentally, on temperature distributions in the fins and in the fluid between two adjacent fins of finned tube heat exchangers is presented. The heat transfer distributions, obtained by a mass transfer technique, prove to be very inhomogeneous over the fin surface, leading to variable results for fin efficiency calculated by the conventional method. In addition, the effect of temperature variation in the fluid, which is usually neglected in fin analysis, is shown in many cases to exert a very strong influence on fin efficiency and total heat flux. For the optimization of fin designs, a combined analysis of local heat transfer, conduction resistance in the fin and temperature variation in the passage is indispensable.

ISSN:0930-7516    

DOI:10.1002/ceat.270150609

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe microbial polysaccharide xanthan was produced by cultivation ofXanthomonas campestrisin four stirred tanks with volumes ranging from 0.072 to 3 m3. Many of the previously suggested correlations for the volumetric mass transfer coefficient described the present data very unsatisfactorily. When Rushton turbines were employed as stirrers, the experimental results agreed well with a correlation suggested by Kawase and Moo‐Young; for the more energy‐efficient INTERMIG impellers, this correlation was modified by a factor of three. Constant specific oxygen transfer rate was found to be the appropriate scale‐up criterion for constant space‐time yield and constant product quality, specifically, the molar mass which determines the viscosit

ISSN:0930-7516    

DOI:10.1002/ceat.270150610

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractMass transfer between liquid and vapour phases in packed distillation columns has been investigated by the two‐film theory for binary associated systems. The effects of association reaction in systems with the association of one component in both phases, taking into account a concentration‐dependent liquid‐phase association constant, were examined. The mass transfer coefficients are modelled, taking into account the association constant. The experiments were carried out at atmospheric pressure with acetic acid‐benzene and acetic acid‐toluene systems in a column packed with Rasch

ISSN:0930-7516    

DOI:10.1002/ceat.270150611

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY