Studies On Flash-Strip Fermentation Process For Ethanol Production

Ethanol is one of the most widest used and heaviest demanded chemical, which may most possible become the substitute for gasoline. With the development of the agriculture and the requirement of environment protection ,the drying up tendency of gasoline resource, importance has been attached to the regenerate clean energies. Among them, the fuel ethanol is the focus of the research today. Ethanol can't compete with the gasoline, due to the high production cost, which can be reduced by optimizing the process and intensifying the technology.Ethanol fermentation process is a typical product-inhibiting process. the in-site ethanol separating process processes can efficiently increases the productivity of the fermentation, basing on which a new ethanol fermentation process, coupled with gas stripping and vacuum flash and named as flash-strip fermentation, is proposed in this paper. This process is provided the advantages of both strip-fermentation and flash-fermentation, and improves the ethanol productivity by increasing the in-situ ethanol removal. The experiments and theoretically analysis indicate that the strip-flash fermentation process, comparing with the gas stripping or vacuum flash process, is more effective, and the sugar(substrate) can be fed at high level of concentration, thus the usage of water can be reduced and the cost in liquid waste disposal is cut. In addition, using the thermophilic yeast to raising the fermentation temperature, as well as increasing the gas flux or the rate of feeding to the flash tank can enhance the fermentation efficiency further.To insure that the strip-flash fermentation can work smoothly, a side-looptype bioreactor is designed. By extending side-arms, the problem of deaeration can be resolve.In this paper, the microorganism reaction kinetics is investigated. through using the catalyzed reactivity mechanism to explain the physical meaning of the Monod Equation, a new model of cell growth kinetics was propound. The result in experiments show that the new model inosculate accurately with the experiment value.In this paper, the ethanol fermentation process, which is coupled with gasstripping and vacuum flash, is modeled. Firstly, the method of striping calculation is improved. Secondly, it can be seen that in the experiment, with the increasing of gas flux, the cell growth process will be accelerated at the beginning and restrained later. By seeing the phenomenon, a gas flux factor is put forward and its expression is defined to modify the model of cell growth kinetics under the gas stripping condition. Using the method listed above, the simulation computing result is consistent with the result got in the experiment of the ethanol fermentation process coupled with continuous gas stripping and vacuum flash .