Conceptual design of reactive distillation columns with pre-reactors

During the past decade reactive distillation (RD) has received intensive attention due to the well-known benefits of integrating distillation with reaction in a single unit. Recently, a design methodology to assess feasibility of a proposed RD column is presented, using intersection of stage composition lines (SCL) in transformed composition variables. Hybrid RD columns, in which one or more column sections perform non-reactive distillation, are addressed by considering the feasibility of liquid compositions at the reactive - non-reactive interface. Reaction equilibrium is assumed on each reactive stage, and VLE is assumed on all stages. Systems with two degrees of freedom are considered, which represent an important class of systems for reactive distillation. In heterogeneously catalyzed reactive distillation columns, one often needs to maximize the catalyst volume inside the column. This requirement might lead to situations where the interfacial area needed for mass transfer is difficult to realize. A detailed cost function will be used to rank the feasible designs. For chemical equilibrium, the column designs have to be calculated only once. The method assumes isothermal pre-reactors and heat exchangers upstream and downstream of the reactor. A case study is presented to illustrate the approach. This is an abstract of a paper presented at the 7th World Congress of Chemical Engineering (Glasgow, Scotland 7/10-14/2005).