摘要:

AbstractSuspension polymerization of styrene was performed in the loop reactor. In order to allow wide change to the polymer particle size, a sub impeller was included within the main impeller. The sub impeller served to increase the fluid velocity and to uniformly disperse the polymer droplets during polymerization.It was investigated how the double agitation method by the main and the sub impellers affected the transient droplet diameter distribution and the final particle size distribution. The particle size could be changed widely by the double agitation method without the decrease in degree of the uniformity of the particle size.

ISSN:0930-7516    

DOI:10.1002/ceat.270190202

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractComparative calculations of several methods of characterization for three multicomponent mixtures that include paraffin, naphthene, and aromatic fractions are shown. Each method requires different experimental information about the mixtures but all use the numerical Gauss‐Legendre quadrature. The results show that characterization making direct use of the TPB distillation curve is the most suitable approach for characterizing complex multicomponent mixture

ISSN:0930-7516    

DOI:10.1002/ceat.270190203

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA three‐step catalytic reaction (TSCR) mechanism is considered. It involves the steps of adsorption of two different reactants and the bimolecular reaction between adsorbed species. For this mechanism the rates of elementary reactions were assumed to be dependent on the surface coverages of two adspecies due to the repulsive mutual interactions between adsorbed species. The surface electronic gas model was chosen for the description of surface inhomogeneity. It is demonstrated that for such a TSCR mechanism sustained oscillations cannot exit. The application of the model to evaluation of kinetic data is discusse

ISSN:0930-7516    

DOI:10.1002/ceat.270190204

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractWhen appropriate membrane was used for the assistance of chemical and biochemical equilibrium reactions, it is possible to enhance the yield and the purity of the reaction product by selectively adding educts or selectively removing products and to a lower the energy input and the reaction time compared to conventional process.In this paper a review on membrane reactors with special emphasis on membrane‐assistance of esterification reactions and a continuous tube membrane reactor for the pervaporation‐assistance of the esterification are presented. The heterogeneously catalyzed esterification of ethanol and acetic acid to ethyl acetate and water was investigated as a typical chemical equilibrium reaction.The selective and simultaneous water separation from the reaction mixture of the esterification with polyvinyl alcohol pervaporation membranes is considered to be an interesting process alternative to the conventional distillation process. Compared to the distillation process, for the pervaporation‐assisted process a decrease of the energy input of over 75% and of the investment and operating coasts of over 50% each was calcu

ISSN:0930-7516    

DOI:10.1002/ceat.270190205

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractVanillin can be produced by oxidation of kraft lignin, with air, in alkaline medium. The optimal conditions for vanillin production strongly depend on pH and temperature. This paper addresses the effect of temperature and pH on vanillin degradation by oxidation. Experiments were carried out in a wide range of vanillin concentration, oxygen partial pressure, temperature and pH. Simple models are proposed to explain the observed rate of vanillin consumption under conditions of high alkalinity (pH>12) and lower alkalinity (pH12,the reaction rate of vanillin oxidation is first order in dissolved oxygen concentration [O2] and in vanillin concentration [C], i.e., (−rC) ∝[O2][C]; at pH<12, the rate is zero order in oxygen concentration and second order in vanillin concentration, i.e., (−rC)∝f(

ISSN:0930-7516    

DOI:10.1002/ceat.270190206

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe equilibria and kinetics of adsorption of lysozyme and bovine serum albumin on the Fractogel‐EMD tentacle‐type cation exchanger and the Fractogel‐TSK conventional cation exchanger have been studied experimentally by batch stirred‐tank method. Adsorption equilibrium data corresponded well to the Langmuir isotherm. For both proteins, the tentacle‐type exchanger exhibited a higher binding capacity than the conventional exchanger. This is attributed to the flexibility of the functional groups in the tentacle‐type exchanger which enhance optimal electrostatic interactions. The dynamic data were analyzed by a simplified data model which lumped mass transfer resistances and intrinsic adsorption kinetics into a single rate constant. For both proteins, it was found that the tentacle‐type exchanger showed a smaller lumped rate coefficient than the conventional exchanger. The difference in the values of the lumped rate coefficients was shown to be due to the influence of nonlinear equilibrium constants rather than due to any difference in rate

ISSN:0930-7516    

DOI:10.1002/ceat.270190207

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractWhole mean gas hold‐up εg, liquid recirculation velocityU1dand mixing timetmwere measured in a 0.12 m3airlift reactor, with an external recirculation loop (ALR‐EL), which was used for the production of the exopolysaccharide, Scleroglucan, by cultivation of the filamentous fungus,Scleroticum glucanicum.Under identical fermentation conditions, the effects of air flowrate and the viscosity of the culture fluid on εg,U1d, andtmwere investigated. In the range studied, empirical correlation for εg,U1dandtmwith both superficial velocityUgrand consistency coefficientKwere obtained and expressed sepa

ISSN:0930-7516    

DOI:10.1002/ceat.270190208

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractProcess energy integration and continuous improvement of process technology are everlasting issues to ensure profitability of chemical productions. And both objectives become increasingly important due to long‐term environmental effects of energy degradation, such as resource depletion, emissions and the release of “waste” heat. The key success factor for process improvement lies in combining up‐to‐date expertise from different areas in an overall approach. One such approach is the systems engineering concept. It helps to structure and to organize problem‐solving process. We strongly believe that the increasing complexity of large and interlinked chemical production system and the tightening of global economic pressure force us to use more than ever systematic analysis and design methods to guarantee optimality throughout the entire product life. First we present a brief introduction to systems engineering in general. Then, in the main part of the paper, we give examples for optimizing the use of energy in chemical plants in order to illustrate advantages of the systems engineering concept. The examples range from improving the performance of individual pieces of equipment over changes in the process structure up to optimizing proce

ISSN:0930-7516    

DOI:10.1002/ceat.270190209

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe paper briefly reviews the historical development of exergoeconomics, the existing methodologies, and their application. Particular emphasis is placed on the optimization of the design of new energy‐conversion system

ISSN:0930-7516    

DOI:10.1002/ceat.270190210

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThis paper represents an attempt to explicitly map the conceptual activities which constitute a process design task into a series of well‐posed, complete and general numerical procedures. In spite of the fact that there is substantial number of design manuals and design procedures which process engineers can consult to choose the most proper approach to a particular problem, there is a remarkable lack of generality on the one side (procedures which apply to the design of a wastewater treatment process cannot be used even in principle to design a fluidized bed system), and an obvious receptivity on the other side (all procedures involve mass and energy balances at some point). With the advance of numerical techniques, virtually every procedure has been computerized, so that engineers can avail themselves of a multitude of computer tools in the majority of their process design activities: as a result of the lack of coordination among different producers though, the situation for what codes are concerned is very confusing: there are many codes which perform nominally the same task, giving (sometimes substantially!) different results when applied to the very same problem; each code sue its won set of property tables, its own I/O format, etc. Finally, with very few exceptions, these codes are not mutually compatible, i.e. the output from any of them cannot be used as the input to any of the other, not only because of the respective formats, but rather because the quantities taken to represent a certain physical process are not the same in different codes.This is a very unsatisfactory state of affairs, both for the final user and for the software producer. Unfortunately, this seems to be a problem for which commercial, technical and historical reasons make it very difficult to find a solution in the short term. The author is convinced that an early exposure to this problem and to a new approach to its solution can only benefit our engineering students, and has therefore endeavored, together with his coworkers, to devise a “modular approach” to the solution of process simulation problems. The material presented here has been originated by a series of lectures and seminars developed in the last three years for master and doctoral level students in Mechanical Engineering. The result of this “distillation” process maybe yet unripe, as they are definitely not complete: but the implications, also in terms of practical application, are very promising, and the approach deserves more attention in the future.The order of presentation of the material is historical/logical: it beings with the old fashioned slide‐rule calculations and proceeds towards the most recent developments of AI base methods. The path is made clear from the very beginning: we are trying to extract from the various engineering activities all the essential knowledge which pertains to the engineer himself, with the final goal of transferring this body of knowledge ‐ in some form suitable to machine communication ‐ to a “universal‐process simulator”, which can then be applied with a high degree of confidence to variety of particula

ISSN:0930-7516    

DOI:10.1002/ceat.270190211

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY