Thesis (M.Eng.)--Chulalongkorn University, 2007

Increases in imported crude oil prices have led to seeking alternative resources. One of the possible solutions is to use the ethanol as an alternative. Ethanol can compete with gasoline, without any intervention, if its total production cost is lower than the gasoline's price. Therefore, this research presented the application of an optimal control for the temperature profile of a batch reactor in ethanol fermentation. The optimal temperature control strategy was applied to obtain the maximum amount of the desired ethanol product at the end of the operation. The solution of the optimal temperature control problem was computed using a sequential approach. It was found that the optimal temperature control provides the best value of final ethanol concentration among other processes. Later on, the effects of time interval were investigated in order to improve the control performance. In addition, preliminary economic analysis on the operating cost was used to compare the results between the system with the optimal temperature control and the isothermal process (31.02oC). The results showed that the unit operating costs of the system with optimal temperature control was relatively lower than that of the isothermal process and the unit profit of the system with the optimal temperature control was to a certain extent higher than that of the isothermal process. These results demonstrated that the optimal temperature control technique assist the ethanol fermentation process operates effectively.