COMPUTER CONTROL AND OPTIMIZATION OF A REPEATED FED-BATCH BIOREACTOR
Abstract
The optimization of a repeated fed-batch biological reactor for the purpose of producing biomass was considered. This type of operation, in which the reactor is cycled through filling, batch, and harvesting stages, is optimal for certain types of microbial growth kinetics. The organism used for this investigation is a methanol-utilizing bacterium isolated in this laboratory. The problem was mathematically formulated and then analyzed using variational calculus techniques. A previously developed growth model for the organism was used to conduct numerical optimization studies based on the variational calculus analytical solution. The effects of the initial or pump-down volume, the final substrate concentration, and the feed substrate concentration were ascertained. The easily implemented bang-bang policy, in which the reactor is filled as quickly as possible, was considered along with the optimal policy. These results formed the basis for experimental implementation. An automated fermentation system was developed so that sophisticated control strategies, including repeated fed-batch, could be implemented. The system, consisting of a computer-compatible and highly instrumented fermentor and a real-time computer, has complete data acquisition and control capabilities. The computer system was configured to operate many fermentors while permitting data analysis and program development to be conducted at the same time. Substantial software was developed in support of the experimental effort. Various schemes were devised to operate the reactor in a repeated fed-batch mode. One technique utilized a predicted substrate concentration as the basis for control during the filling stage. The substrate concentration, not easily measured on-line, was estimated from oxygen uptake rate and carbon dioxide production rate data. The effect of the initial volume was measured for both the optimal and bang-bang policy implementations. The results were then compared with those obtained from the numerical analysis.
Degree
Ph.D.
Subject Area
Chemical engineering
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