Ja. Asenjo et al., Strategies for the simultaneous optimization of the structure and the process variables of a protein production plant, COMPUT CH E, 24(9-10), 2000, pp. 2277-2290
Process performance models for a multiproduct batch protein plant are used
to exploit alternative strategies in the optimization of both the process v
ariables and the structure of the plant. Simple process performance models
are used to describe the unit operations, which renders explicit expression
s for the size and time factor model in the design of batch plants. In the
proposed approach the process variables are optimized regardless the plant
structure constraints, which are left as a posterior decision. This optimiz
ation is done in a single product-free intermediate storage (SP-FIS) scenar
io, unbiased with any plant structure. The approach is compared to the case
of recipe values for the process variables and to the best optimal solutio
n for the nonconvex mixed integer nonlinear program (MINLP), which arises w
hen simultaneously optimizing the structure and the process variables. This
last optimization model is hard to solve and its global solution remains a
s an open problem. The proposed approach generates solutions Very close to
the ones obtained from nonconvex MINLP and is quite superior than simply re
sorting to recipes. We also study the role of process variables in this app
roach. It is found that they behave as in continuous processes by trading o
ff cost components, with a smooth dependence on the overall cost. Moreover,
for feasible designs that include the size and time constraints that corre
spond to the plant structure, the process variables accommodate the size an
d time factors to reduce idle rimes and equipment under-occupancy. (C) 2000
Elsevier Science Ltd. All rights reserved.