摘要:

AbstractThe behaviour of an adiabatic packed bed reactor with periodic flow reversal has been studied by means of model calculations. A heterogeneous model as well as a pseudo‐homogeneous model have been developed. It is shown that a high degree of conversion can be obtained in an autothermal process even with very low adiabatic temperature rises of some 10 to 20 K. The reactor is insensitive to fluctuations in inlet concentrations and in through‐put. Short‐cut methods proposed in the literature for calculating the plateau temperature in the pseudo‐steady state are studied. The so called countercurrent‐flow reactor approach showed reasonable agreement with the plateau temperature obtained by dynamic calculations with the full reac

ISSN:0930-7516    

DOI:10.1002/ceat.270170402

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractConcentration profiles are measured during the mixing process of carbon dioxide and air, which were injected into the rectangular cross section of a duct. The volume flow rates of both components differ considerably. The non‐stationary and three‐dimensional concentration fields are measured by optical tomography using holographic interferometry as the measuring principle. Projection data from four different viewing angles are used for tomographic reconstruction by the ART method. Pressure losses due to mixing processes are also measured. Results are presented for different angles of injection and different ratios of momentum flow rate for single and multiple jets of carbon dioxide which were injected into the carrier gas stream of

ISSN:0930-7516    

DOI:10.1002/ceat.270170403

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractA spray dryer simulation program is described. It is based on the known conservation laws and permits determination of temperature and moisture profiles and droplet trajectories inside spray dryers. An industrial spray dryer used in the manufacture of detergents serves as an example to demonstrate the applicability of the program; this approach required prior experimental determination of the flow field and an axial temperature profile. On the basis of a rough estimate of the drying rate in the spray dryer, good agreement was observed between experiment and simulation.

ISSN:0930-7516    

DOI:10.1002/ceat.270170404

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe purpose of this paper is to investigate the swelling of emulsion liquid membranes using dithio‐DEHPA as carrier. The application of interest was the removal of zinc from a synthetic aqueous solution which simulates a zinc plant effluent. The effect of several variables such as the concentration of carrier in the membrane, stirring speed and permeation time on the swelling of the emulsion is reported. Experimental results show that occlusion depends mainly on the amount of carrier in the membrane and can be significant when the concentration of carrier is lower than 6.0%. The interfacial tension analysis confirms that the size of globules is influenced by the concentration of carrier in the membrane. Stirring speed and permeation time are related to the water transport and must be kept at low value

ISSN:0930-7516    

DOI:10.1002/ceat.270170405

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractAn automatic apparatus has been developed and set up for the study of drop‐interface coalescence. Most other studies have concentrated on events when the drop arrives at the interface with its terminal velocity. In our case, the drop is maintained fixed at the tip of a needle, and the interface is moved towards the drop at a controlled speed. The coalescence times are measured by means of a vectorial video camera focused on the drop. Several times are measured by means of a vectorial video camera focused on the drop. Several parameters have been investigated, such as the drop diameter, the relative drop‐interface velocity, the phase system, the presence and the direction of mass trans

ISSN:0930-7516    

DOI:10.1002/ceat.270170406

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper describes the development of a dynamic simulation model for stirred tank batch or semi‐batch chemical reactors fitted with an alternative heating‐cooling system. Heat and mass balances are established for the reactor and its jacket. Since the general purpose of our research is the thermal control of these reactors, special attention is devoted to the behaviour of the heating‐cooling system. In this article, we are particularly concerned with an alternative system, i.e. different fluids at a constant temperature can be alternatively delivered to the jacket. The computer simulation programme is flexible, enabling simulation of a batch or semi‐batch reaction vessel, ranging from a laboratory pilot plant to a full‐scale production plant. A control algorithm is included which allows reactor operation with open or closed‐loop temperature control. To demonstrate the good performance of the simulation model, experimental results are presented for both a pilot plant and an industr

ISSN:0930-7516    

DOI:10.1002/ceat.270170407

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper presents a new procedure for optimization of continuous mixed suspensionmixed product removal (MSMPR) crystallizing systems. Owing to the difficulties of theoretical modelling, simulation of the MSMPR crystallization process is based on the use of artificial neural networks (ANN). The optimization criterion is a compound objective function corresponding to an intended mean crystal size dimension and a minimal dispersion. The presence of multiple local minima has called for investigation by several optimization techniques. Ultimately, Luus' and Jaakola's random adaptive method proved to be most effective. The results obtained lend support to the general procedure proposed.

ISSN:0930-7516    

DOI:10.1002/ceat.270170408

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractA rigorous one‐dimensional heterogeneous model is developed for a secondary reformer in an ammonia plant with special emphasis on the catalyst particle models. These are based on the effective diffusivity model and the Stefan‐Maxwell model in the catalyst pore and the film around the catalyst particle. The performance of these four models is evaluated for the data collected from a commercial reformer in the complete operating range and recommendations are made regarding the use of appropriate particle models. The models for the catalyst particle show considerable deviations at the particle level but the reformer simulations produce almost identical results at the global level for all the four particle models. The need for a rigorous treatment of interphase resistance to mass transfer has been clearly demonstrated by comparison of the present model with the model of Singh and Sa

ISSN:0930-7516    

DOI:10.1002/ceat.270170409

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe classical two‐film model for mass transfer between two fluid phases can only be used to describe the steady state mass transfer mechanism. Both the penetration and the film‐penetration model are also valid solely when only one diffusion boundary layer exists at the interface between the phases. With a view to surmounting the limitations of the above models a new model has been developed for the mass transfer between two fluid phases with two diffusion boundary layers at the interface. The new model is based on the two‐film concept and the Danckwerts distribution function, and is also able to simulate the unsteady state mass transfer mechanism between two fluid phases with two different boundary l

ISSN:0930-7516    

DOI:10.1002/ceat.270170410

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractIn this study, a simple and effective technique for determining overall mass transfer coefficients in fixed bed sorption columns with recycle is presented. This new technique is free of the assumption of negligible time rate of solute concentration change in the fluid, i.e. (∂c/∂t) = 0, which has been widely used in former fixed bed sorption column analy

ISSN:0930-7516    

DOI:10.1002/ceat.270170411

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY