Gustavo Pérez

Parametric sensitivity in fixed-bed catalytic reactors

Abstract This paper introduces a criterion for runaway in fixed-bed catalytic reactors based on the behaviour of sensitivity coefficients along the reactor. The criterion can be used when the temperature variation in a co-current cooling medium is taken into account; and also, it is not restricted to simple kinetics. In addition, multiple reactions may be analysed. Some examples of industrial significance are studied and the results are compared with those obtained by other authors.

Production of occlusion bodies of Anticarsia gemmatalis multiple nucleopolyhedrovirus in serum-free suspension cultures of the saUFL-AG-286 cell line: Influence of infection conditions and statistical optimization

The influence of the conditions of infection on the yield of occlusion bodies (OBs) of the Anticarsia gemmatalis multiple nucleopolyhedrovirus (AgMNPV), produced in serum-free suspension cultures of saUFL-AG-286 cells, was investigated by two 2(2) full factorial experiments with centre point. Each experiment tested the effects of the initial cell density and the multiplicity of infection at two levels, in the four possible combinations of levels and conditions, plus a further combination with each condition set at the middle of its extreme levels. The yield of occlusion bodies proved to be sensitive to the modification of infection conditions. Maximum yield as high as 3 x 10(8) OBs mL(-1) was attained provided that the maximum density of viable cells was in the range between 4 and 8 x 10(5) cells mL(-1). The optimum value of the maximum density of viable cells could be reached by the combination of several values of initial cell density and multiplicity of infection. A regression model was established and validated in order to optimize the infection conditions. These results demonstrate the importance of an adequate selection of infection conditions, and they could be useful in the development of a feasible in vitro process to produce the AgMNPV insecticide in a new serum-free medium.

Graphical procedure for reactive distillation systems

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 Barbosa el 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. The main objective in developing this model is to obtain, as much as possible, rigorous information for the analysis of one reactive distillation column in a Process Simulator with capability of handling this type of new operation.

DYNAMIC BEHAVIOR OF REACTIVE DISTILLATION COLUMNS. EQUILIBRIUM SYSTEMS

This paper deals with the dynamic behavior of simultaneous reaction-separation systems which operate at or near the chemical equilibrium in the liquid phase. The process under study comprises a whole set of “instantaneous”, and very fast reversible reactions where the difference in volatilities favors both the progress of reaction and product separation. The main aim of our study is to gain a deeper understanding of the dynamic behavior of distillation columns by using a model that is simple and efficient, yet informative. This kind of model is outstanding for synthesis and design of control schemes which require a careful modelling and understanding of process response to different changes in the environment. We use a suitable transformation of variables (after Barbosa and Doherty, 1988b) in order to define a new set of state variables; as a result, the balance equations become identical to those for conventional distillation. Also, an efficient physicochemical algorithm that can handle both the original...

A GENERALIZATION OF TWO INTRINSIC CRITERIA FOR RUNAWAY IN FIXED BED CATALYTIC REACTORS PART I DEVELOPMENT OF THE CRITERIA

The paper introduces an extension of the two intrinsic criteria for runaway in fixed bed catalytic reactors based on the occurrence of characteristic points in the temperature profile along the reactor, that were developed by Van Welsenaere and Froment. The criteria have been generalized in order to consider general order reactions and thermal gradients in the shell side of the reactor. Keeping their original simplicity, they can deal with the co-and counter-current flow models, treating the constant wall temperature case as a particular one.

A GENERALIZATION OF TWO INTRINSIC CRITERIA FOR RUNAWAY IN FIXED BED CATALYTIC REACTORS PART II CRITERIA PERFORMANCE ANALYSIS CO-CURRENT VERSUS COUNTER-CURRENT OPERATION

In this part II, the derived criteria are applied to an o-xylene oxidation reactor, and some considerations about their comparative behaviour, conservativity and agreement with true critical values are presented. In addition, some typical results are compared with the ones obtained by other authors. For the co-current flow model the criteria are contrasted with the ones reported by Soria Lopez et al. (1981) and the criterion of Henning and Perez (1986). For the counter-current case the comparison is performed considering the critical inlet conditions derived by applying Akella and Lee (1983) and Henning and Perez (1986) criteria. Finally, an analysis of the co-current versus counter-current operation that considers economical and operability aspects is presented

Metodología de optimización de procesos industriales relacionando las inversiones con los costos operativos

The optimization of processes is a work area that has progressed in recent years, considering each superstructure independently, the results reflect cost constraints, since the auxiliary services and the heat exchange network would come data as the result of the plant itself, or as a function of it, and not in terms of the resulting investment for the best synthesis alternative of the analyzed process. This work proposes to compare different methodologies applicable to the optimal design of a fluid milk processing facility, using the Ultra High Temperature (UHT) sterilization mechanism, using an available commercial simulator (SuperPro Designer, V 8.5). The results show that the relative weight of investments in relation to operating costs is essential to establish an optimization methodology; Or to discard a complicated method versus a solution taken with more common sense engineers, than optimization tools, in their different versions. As for the results obtained, it is concluded that rigorous economic optimization has to be taken into account in conjunction with the best efficiency of pinch networks, and not each separately.

Horizontes de planificación diferentes. Una discusión necesaria

El horizonte de planificacion, o ciclo de vida del proyecto, es una importante variable independiente, tanto como la tasa de descuento elegida, usual en todos los metodos de flujo de fondos descontados, siendo su eleccion fuertemente dependiente del caso especifico tratado. La comparacion entre inversiones que tienen vidas diferentes es un tema complicado. La mayoria de los metodos hallados en la literatura tienen hipotesis que, o no son totalmente claras, o no guardan el necesario rigor, a causa del problema siempre presente de la consideracion de repetitividad. En este trabajo se concluye que el conocido metodo del beneficio (o costo) anual equivalente es una buena opcion, y su defensa se basa en la simplicidad y el uso universal que se le ha dado al mismo. Por otra parte, tambien, se ha propuesto otra alternativa para llevar adelante esta tarea de decision, como una contribucion mas a la cuestion aqui planteada.

Metallurgic process simulation: heat transfer model, with a mushy zone, in a coke oven

Abstract The coking process is based on the transformation of coal into coke due to heat transfer. This problem is characterized by the existence of a mushy zone. The resolution of the proposed model was carried out by the use of a numerical technique. The simulations results are satisfactory when contrasted with those given by steel industry procedures.