Economic Tradeoffs involved in the Design of Batch Fermentation Processes with Environmental Constraints

GABRIELA CORSANO; OSCAR IRIBARREN; JORGE M. MONTAGNA; PÍO A. AGUIRRE; ERENIO GONZALEZ SUAREZ

Chemical Engineering Research and Design

The Institution of Chemical Engineers

Lugar: Rugby, UK; Año: 2006 vol. 84 p. 932 - 942

0263-8762

A process model is used for analyzing the economic tradeoffs involved in the synthesis, design and operation of a typical batch fermentation plant involving batch and semicontinuos operations with the recycle of the otherwise waste stream that results after recovery of the product of interest from the fermentation broth. This recycle contributes to a more complete substrate consumption, water reuse and reduction of the environmental impact of the process. Process variables are optimized simultaneously with the plant structure, by formulating the whole optimization problem as a Non Linear Program NLP, an approach that for this case is shown to be robust in finding a good economical solution of this non convex optimization problem. The environmental concern about producing large amounts of fermentation broth waste was accounted for by penalizing its production combined with allowing their recycle to the different types of fermentors based on process considerations. Optimal design and operation for different studied cases are shown, analyzing the economic tradeoffs involved in selecting the number and operation mode of biomass grow and metabolite fermentors, the sugar substrate blending to each fermentor, the recycle of fermentation broth waste, the initial and final concentrations of biomass, substrate and metabolite, and the role of idle times in the process that operates on a Zero Wait batches transfer policy. The paper reports some optimal plant structures and figures for process variables not implemented in industrial practice but backed by sound process analysis arguments, thus suggesting that they may be worth to be explored.