Mathematical Modelling of Tower Fermentation Processes

Abstract

The Fermentation Industries are currently concerned with a number of large-scale processes, including single cell protein production, effluent treatment, and the production of alcoholic beverages. Successful design and optimisation of these new systems is becoming increasingly dependent upon the availability of mathematical models for use in simulation studies. The research described in the thesis has been concerned with the analysis and modelling of some of these microbial processes, in particular those involving tower fermenters. Because of the nature of such processes the work has involved considerable interaction between the basic disciplines of chemical engineering and microbiology. Models of specific aspects of tower fermentation processes are developed in the earlier sections of the thesis, including: (1) a model to describe liquid-phase mixing in bubble columns and tower fermenters; (2) an empirical method for predicting mixing parameters for both the backflow stirred tanks model and the axially-dispersed plug flow model; (3) a theoretical model describing oxygen mass transfer in bubble columns and tower fermentation systems; (4) a detailed review of deterministic kinetic models for microbial processes; (5) a brief review of continuous culture theory and mathematical descriptions of transient microbial behaviour; and (6) analysis and modelling of the batch beer fermentation process. The application of these concepts to the development of comprehensive models for tower fermentation systems is considered in the latter part of the thesis. First, a model describing a continuous beer fermenter is developed, and second, consideration is given to the design and modelling of aerobic tower systems. These models have been useful in: (1) directing current experimental programmes, and (2) high-lighting areas where more research effort is needed. It is hoped that ultimately the models will be suitable for the scale-up, design and optimisation of tower fermentation systems.