No More Runaways in Fine Chemical Reactors

Abstract

In this paper after a literature surveyin which we describe previous development of the theory and the experimental work to prove the theorieswe discuss the so-called safety diagram and practical values of the relevant parameters in laboratory and plant equipment. We explore when operating conditions are inherently safe and prove that the findings of the safety diagram also apply to batch reactors. We explain the safety diagram data can also be applied to reactions with orders different from 1 for each component and to multiple reactions. All criteria in the literature, developed to determine safe operating conditions to prevent runaway in semibatch and batch reactors, are based on the knowledge of the kinetics of the reactions concerned. In fine chemical industries, however, usually it is impossible to determine kinetics due to economic and time constraints. Previous work on so-called safety diagrams, therefore, has been extended to the full range of all practical cooling number values as they occur in plant reactor operations. From the results obtained two diagrams are presented for the minimum value of the so-called exothermicity, below which no runaway will occur, as well as for the minimum reactivity, above which no runaways are possible, both as a function of the cooling number: one diagram is for the reactions taking place in the dispersed phase, and the other is for those in the continuous phase. With these diagrams inherently safe operating conditions can be determined for high reactor productivities. It is demonstrated that the data obtained can be used also for a multiple-reaction scheme, except for autocatalytic reactions. Further it is discussed how the necessary information can be obtained by reactor tests in the plant, by experiments in standard laboratory equipment, and from the literature. A rapid procedure is developed which leads to safe operating conditions without costly and time-consuming kinetic studies.

Kinetics of catalytic hydrogenation of β-ionone and application of a presaturated one-liquid flow reactor for the production of fine chemicals

“…According to literature [16,20], values of the overall heat transfer coefficient U for a jacketed vessel and a cooling coil are typically 450 and 750 W/(m 2 K), and the cooling areas per unit volume A C are given for good agitation and a vessel equipped with baffles by the ratio 4=d R (jacketed cylinder with diameter d R ) and about 6=d R for a coil. In total, this leads to a value of 1/ d R Â 6000 W/(m 2 K) for the term A C U.…”

“…This is underlined by statistics of safety authorities in one of the countries of the European Union revealing that on a total number of around 2000 installed batch and semibatch reactors an average of around 110 runaways occur annually [15,16], whereby of course this lead in most cases only to production loss and some equipment damage. Thereby, one should realize that according to WEsterterp around 80% of the reactions executed in fine chemical plants have so low heat release potential that a runaway is impossible [16]. Therefore, the frequency of runaways for reactions with high exothermicity -e.g.…”

Sensibilidad Paramétrica y Condiciones Seguras de Operación de la Hidrólisis del Anhídrido Acético en un Reactor Batch

“…Por otro lado, los criterios para establecer condiciones seguras de operación se pueden clasificar en tres categorías: el método de sensibilidad paramétrica (Morbidelli y Varma, 1988;Varmaet al, 1999); el método de la divergencia basado en la teoría del caos (Strozzi, y Zaldivar, 1994) y el método de la extensión de trayectorias (Bosch et al, 2004). Además, Westerterp y Molga (2004) propusieron una metodología basado en diagramas de operación segura para reactores batch y semibatch. Este tipo de diagramas posteriormente fueron implementados por Maestri y Rota (2005) y por Milewska y Molga (2010) quienes incorporaron modelos de dispersión usando CFD.…”

Adiabatic behavior of thermal unstable compounds evaluated by means of dynamic scanning calorimetric (DSC) techniques

“…1,2 A closer look at the causes of these incidents reveals that one of the major reasons can be ascribed to the lack of knowledge of the thermal behavior of the substances involved. 3,4 This lack of knowledge has different origins.…”