Distillation column with reactive pump-arounds: an alternative to reactive distillation

Abstract

The hardware design of reactive distillation (RD) columns pose severe challenges with respect to the choice and design of the hardware; the requirements of reaction (i.e. high liquid or catalyst holdup) is not in consonance with the requirement of separation (high interfacial area). In this paper, we examine an alternative to the RD concept, namely a distillation column networked with a number of side (external) reactors. If each distillation stage is linked to a side reactor, the performance of the RD column is matched exactly. From a practical point of view, it is desirable to reduce the number of side reactors to below, say, six. The precise location of the chosen number of side reactors and the manner in which the liquid draw-offs and reactor effluent re-entry to the distillation column needs to be chosen carefully. We have developed an algorithm to determine an optimum configuration of the side-reactor concept in order to maximise conversion. For the case study of methyl acetate production, we see that it is possible to match the conversion level of an RD column by appropriate choice of the number of side reactors and the pump around ratio. The higher the conversion target the larger the number of side reactors and pump around ratios. For modest conversion levels, say <90%, even a 3-side-reactor configuration will be able to match the performance of the RD column. The study presented here reveals the potential, and limitations, of the side-reactor concept for use as an alternative to RD technology.