Optimal reactor design from a geometric viewpoint. Part II. Critical sidestream reactors

For a specified set of available feed streams and a specified network of ch emical reactions, the attainable region is the full set of output states th at can be attained by means of all possible reactor designs (within a gener ally broad class). The boundary of the attainable region is of great intere st, for it represents the outer limit of what is actually achievable. In co nsideration of isothermal designs involving only reaction and mixing, it wa s shown in Feinberg and Hildebrandt (1997. Chemical Engineering Science, 52 , 1637-1665), how, independent of the reaction network or its kinetics, the attainable region's boundary is invariably shaped by classical plug flow r eactors, ideal CFSTRs and differential sidestream reactors (DSRs), each pla ying special roles. Differential sidestream reactors generally serve as cru cial precursors to plug flow reactors, which, in turn, provide final access to the attainable region's extreme points. Here we examine properties of c ritical DSRs - that is, DSRs whose products lie entirely on the attainable region's boundary. We show that critical DSRs must conform to highly detail ed design equations, equations that govern in a precise way the strategic a ddition of sidestream along the reactor's extent. In particular, the equati ons indicate how the sidestream addition rate, the sidestream composition, and the reaction rates must be orchestrated if the DSR is to give rise to p roducts at the outer limit of what is achievable. (C) 2000 Elsevier Science Ltd. All rights reserved.