摘要:

As in continuous distillation systems, the design of batch distillation begins with the selection of a sequence of separations. This paper considers the usual case where the column processes multicom-ponent mixtures with the recycle of intermediate cuts. It is proved that this cyclic operation does converge to a “steady state” balance. This permits to model batch distillation with recycle as a function of the steady state variables, i.e. without the need of successive simulations to obtain the steady state. Furthermore, we use simplified analytical models which permit a quick approximation to the optimal design of a given sequence, thus aiding the designer in the screening of alternative separation sequences, to preselect one, or a small set of good sequences.

ISSN:0098-6445    

DOI:10.1080/00986449308936104

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Investigations were made on the effect of the presence of polyvinylpyrrolidone (PVP) additive in the casting solution on the performance of polyethersulfone (PES) ultrafiltration membranes in the range of PVP/PEs weight ratio below 0.5. It was further attempted to investigate the effect of PVP additive on the size of PES polymer in the casting solution and the pore size and the pore size distribution of PES membranes. It was found that the presence of PVP additive decreases both the polymer size and the membrane pore size. Discussions were made on the mechanism of the formation of the pore based on the correlation between the polymer size and the pore size.

ISSN:0098-6445    

DOI:10.1080/00986449308936105

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The adsorption of hexachloroplatinic acid on γ-Alumina coatings is investigated in order to prepare monolithic structure catalysts for carbon monoxide oxidation. For acid concentrations in the range 0.25-1.5 mM the adsorption is examined in a batch process and a kinetic model is proposed and evaluated. The pH of the solution has a major impact on the adsorption rate and dispersion of Pt on Al2O3and when acidity becomes lower than 1.5 pH value the deposition of Pt on the catalyst by pore volume impregnation is favourable. The catalytic properties of Pt-alumina as oxidation catalyst for CO depend strongly on the adsorption rate of H2PtCI6. A difference of 80 °C at the light off temperature is observed for catalysts prepared by adsorption from solutions with different acidity.

ISSN:0098-6445    

DOI:10.1080/00986449308936106

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Solid-liquid mass transfer in three phase fluidized beds is reported for column diameter up to 0.3 m. The range of superficial gas and liquid velocities studied were 0.03-0.2 m/s and 0.026-0.07 m/s, respectively for a 0.015 m diameter column and 0.015-0.11 m/s and 0.01-0.05 m/s, for a 0.3 m diameter column. The mass transfer coefficient increased with increase in gas flow rate and was independent of liquid flow rate over the range studied. The mass transfer coefficient seemed to depend on particle size; the dependance was unaffected by reactor scale-up. Kslincreased with column diameter according to relation KSL∞ D0.26.

ISSN:0098-6445    

DOI:10.1080/00986449308936107

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A theoretical approach to analyze robustness of feedback linearization is developed. Specifically, sufficient conditions for boundedncss and convergence of the system trajectories are found when feedback linearization based on a nominal mathematical model is applied to an uncertain real plant, which may have parametric and structural uncertainties. The developed approach does not require the restrictive matching condition, a global Lipschitz condition, nor the same equilibrium point for mathematical model and real plant for all possible model-plant mismatch. An example of an unstable chemical reaction in a CSTR demonstrates the utility of the developed approach in analyzing robustness of feedback linearization for nonlinear chemical processes.

ISSN:0098-6445    

DOI:10.1080/00986449308936108

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The steady-state performance, mainly with respect to substrate conversion, of a bubble column bioreactor with substrate limited microbial growth and cell recycle through a membrane filter is investigated numerically. The dispersion model and the Monod equation are employed for describing flow behaviour and cell growth rate in the reactor, respectively. Moderate longitudinal mixing causes a favourable effect on the substrate conversion. Such an effect is enhanced with increasing recycle ratio and separator concentration efficiency. There exists an optimum Peclet number to maximize the substrate conversion. The relation between the critical recycle ratio at which the optimum Peclet number becomes zero and the corresponding exit substrate concentration is presented.

ISSN:0098-6445    

DOI:10.1080/00986449308936109

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this paper we analyze a ternary reactive distillation system, where an equilibrium chemical reaction occurs in the liquid phase. By using a set of transformed variables proposed by Barbosael al. (1988b) and well known graphical procedures for non-reactive systems; the minimum reflux ratio, minimum number of equilibrium stages, mass and energy balances for a reactive column and flash can be easily obtained. The procedures developed in this paper are applied to ISOBUTYLENE-METHANOL-MTBE system.

ISSN:0098-6445    

DOI:10.1080/00986449308936110

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Niederlinski's theorem essentially provides a method for recognizing the lack of structural stabi-lizability in multiloop integral control systems. The purpose of this study is to complement Niederlinski's original theorem by relaxing some of the restrictions it encounters for its application. The fact that Niederlinski's index can be applied to the plants exhibiting time delays and unstable poles in their diagonal (controlled) elements is noted in this paper. It is also shown that Niederlinski's original assumption, that in order to apply the NI to the problem of integral instability all the elements of the loop transfer matrix must be strictly proper, can in fact be relaxed to the condition that all the triangular elements of the loop transfer matrix must be strictly proper. Thus even in a case where some elements of plant transfer matrix, and consequently of loop transfer matrix are not strictly proper, the NI still remains applicable if in fact the triangular elements of the loop transfer matrix are strictly proper. This same simplification of conditions is likewise shown to be applicable in the case of Relative Gain Array (RGA). Finally, an application of pairing criteria, by use of NI and RGA, to unstable plants under multiloop integral control is proposed.

ISSN:0098-6445    

DOI:10.1080/00986449308936111

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Reactions of methylene chloride and methane in nitrogen bath were studied in tubular flow reactors of different diameters (4, 10, and 16 mm ID) over a temperature range of 750 to 1042°C at atmospheric pressure. The concentration ratio of methylene chloride/methane/nitrogen was kept constant at 1:4:10. Acetylene, ethylene, benzene, carbon, and hydrochloric acid were the major products for residence times of 0.08 to 2-5 sec at temperatures above 950°C. Stable chlorinated hydrocarbons detected at lower temperatures (<900°C) include chloromethane, trichloroethylene, and vinyl chloride. Significant wall effect was observed for surface to volume (S/V) ratios of greater than 10cm-1. The impact was unimportant at lower S/V (4, and 2.5cm-1’) ratios.

ISSN:0098-6445    

DOI:10.1080/00986449308936112

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The kinetics of ozonation of the sulfur dye Methylene Blue in aqueous solution is studied. The experiments have been carried out in a bubble column, using a single nozzle as gas sparger. The influence of the operating variables (initial concentration of Methylene Blue, ozone partial pressure, temperature and pH) on the oxidation process is established. A stoichiometric ratio of 3 moles of ozone consumed per mol of dye reacted is deduced. A reaction scheme based on the direct ozone attack to the dye is suggested, and it agrees with the found stoichiometry. The overall reaction orders and rate constants as a function of pH and temperature are determined following the film theory which is applied to the experimental data. The process develops in the fast pseudo mth order kinetic regime of absorption.

ISSN:0098-6445    

DOI:10.1080/00986449308936113

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor