Optimal reactor design from a geometric viewpoint - III. Critical CFSTRs

For a specified network of chemical reactions and a specified feed, the attainable region is the full set of outputs (in some suitable state space) that can be realized by means of all possible reactor configurations (within a generally broad class). The boundary of the attainable region and, in particular, its extreme points represent the outer limits of what is achievable. In a previous article we showed that, for the class of steady-state isothermal designs involving only reaction and mixing, critical combinations of plug flow reactors, sidestream reactors, and CFSTRs invariably play a crucial role in shaping the attainable region's boundary. In still another article, we deduced special design equations that critical sidestream reactors must respect. Here we show that CFSTRs giving rise to attainable region extreme points must also conform to certain special design equations. For a specified CFSTR feed, these equations indicate that there are only very exceptional (and generally, computable) values of the residence time for which the effluent composition can be extreme. Moreover, these equations indicate how, for the specified kinetics, only certain exceptional compositions can serve simultaneously as CFSTR effluents and as attainable region extreme points. (C) 2000 Elsevier Science Ltd.;UI rights reserved.