Design and control of coupled reactor/column systems .1. A binary coupled reactor/rectifier system

This is the first in a series of papers that explore the challenging problems associated with the design and control of coupled reactor/column systems. The individual unit operations of distillation and reaction have been widely studied, but processes in which these units are coupled remain virtually unexplored in the literature. In this paper we study the simpliest possible coupled system in which component A reacts reversibly to form product B. In this binary system, component B is more volatile, so the process consists of a rectifying column sitting above a continuous stirred-tank reactor. Vapor from the reactor passes directly into the column. Subsequent papers will present results for systems with different volatilities and multicomponent reactions, which require much more complex process flowsheets, i.e. multiple columns and recycle streams. Some interesting and unexpected results were uncovered in this simple process. In the area of steadystate design we show that, in addition to having a minimum reflux ratio and a minimum number of trays, there exists a minimum reactor volume below which the process is infeasible for a specified product purity. In the area of dynamics and control, we show that the effective openloop (with level loops closed) stability of this system depends on the inventory control structure chosen. Multiple steadystates can occur. The best control scheme was one in which reactor temperature was nor controlled. Copyright (C) 1996 Elsevier Science Ltd