Some aspects in the design of multicomponent reactive distillation columns including nonreactive species

Abstract

Some aspects related to the design of reactive distillation columns are addressed in this paper. A new set of transformed composition variables is proposed for mixtures including one or more components that are inert under the process conditions. This set corresponds to an extension of that suggested by Barbosa and Doherty (1988a, Chem. Engng Sci. 43, 1523–1537) and allows to compute by means of any traditional procedure, the concentration profiles along the column and therefore, the minimum reflux ratio. The compositions of product streams of a reactive distillation column are subject to constraints of thermodynamic nature that can be determined before any attempt to design the column. These thermodynamic constraints do not have a counterpart in conventional distillation and become an essential piece of information in order to select the design variables and specify their values. A parametric analysis of the simultaneous chemical reaction and liquid-vapor equilibrium is suggested as a very useful instrument to select thermodynamically feasible design specifications. In this work, we also present an initial discussion about possible columns sequences to obtain the reaction product free of inert species. The selection and calculation of the relevant variables that are common in the first steps of the design and synthesis of reactive distillation processes are discussed through examples. Finally, throughout the entire paper several interesting physical and operational conclusions regarding inert components in reactive distillation are given. The main conclusion is that the inerts play a key role in the design of a reactive column.