Non-linear characteristics of a membrane fermentor for ethanol production and their implications

An experimentally verified five-dimensional model for anaerobic fermentation is used to explore the complex non-linear behaviour of a continuous membrane fermentor. Detailed modeling and detailed static/dynamic investigation are carried out with special emphasis on static/dynamic bifurcation and the effect of selective ethanol removal. Possible increase of sugar conversion and ethanol yield/productivity under autonomous periodic operation at high sugar concentrations was found for continuous stirred tank fermentors with/without ethanol removal membranes. The investigation shows that the ethanol selective membrane does not act only as an ethanol production enhancer but also as a stabilizer for the unstable fermentor. The present paper covers a wide range of parameters showing the non-linear richness of the process and the implication of the complex non-linear steady state and dynamic characteristics on the process ethanol yield and productivity.