| Fuel ethanol is an important source of biomass and has attracted more and more attention, because it has many advantages such as clean and renewable. Now the correlative study has become a hot research field of energy. However, the fuel ethanol industrialization still faces many challenges. At present, food starch and sugar cane are used as main raw materials in the industrial production of fuel ethanol, putting it in dilemma because of competing food with human. In the future, this technology could be limited according to the sustainable development. As an alternative, lignocellulose attracts close attention and becomes popular in international energy area for widely available and environmental pollution-free production of ethanol. Corn stover is a very rich source of cellulose in our country, so the production of cellulose ethanol from corn stover has broad prospect. In the light of the problems of low conversion and high production costs existing in fuel ethanol production, this thesis optimizes the producing process of cellulose ethanol from corn stalks, considering the by-products based on the techno-economic analysis. Moreover, novel technics were further developed to produce fuel ethanol using mixed raw materials of starch with corn stover or corn cob on the basis of ingredients analysis. Preliminary experimental optimization and corresponding techno-economic analysis were also carried out to provide scientific guidance and technical support.Firstly, the fuel ethanol production from corn stalks was investigated, and the techno-economic and sensitivity analysis were conducted on an annual capacity of50000t ethanol. The simulation shows that the energy consumption of crude distillation tower is obviously low when the ethanol concentration in fermentation broth is higher than4%(o). Direct fixed capital of the process is about137million yuan and the lowest cost for cellulosic ethanol is8425(?)/t. The annual by-product output of37500t CO2and215t fusel oil would bring additional revenue23.86million yuan. The economic sensitivity analysis shows that the price of cellulase is relatively sensitive to the production cost of ethanol, and the recovery and utilization of CO2is obviously favorable for profit of process. Energy integration among the various processes of the biorefinery and multi-product coproduction is expected to reduce costs, while the costs can be further reduced when the technology for cellulosic ethanol production reaches such a perfect degree.Secondly, the feasibility of fuel ethanol production from mixed raw materials of starch with corn stover was investigated. The lignocellulose content in corn stover was measured and the operating conditions for pretreatment were optimized. Then, the performances of three fermentation processes using corn starch, corn stover and mixed materials were evaluated respectively. The results showed that the ethanol concentration from mixed materials was66.4g/L, which was far higher than other two fermentation processes. This means that the fermentation using corn starch and corn stover as raw materials is feasible. After that, we calculate the costs of three processes. The cost of process using mixed material is close to that using corn starch. It is feasible replacing corn stover with mixed material to produce fuel ethanol and avoiding the dilemma of competing food with human.Finally, we discussed the feasibility of fuel ethanol production from mixed raw martial of starch with corn cob. We detected the lignocellulose content in corn cob before and after acid hydrolyzation. The results showed that there are some changes in the chemical composition. The change in hemicellulose content is remarkable, from41.5%to7.7%; while the change in lignin content is very limited, from7.8%to11.6%. Afterwards, the fermentation processes using corn starch, corn cob and mixed material were studied respectively under the optimized enzymatic hydrolysis conditions. After enzymatic hydrolysis, the reducing sugar concentration was198.62g/L, the glucose concentration was87g/L. The final ethanol concentration in fermentation was50.86g/L, which was higher than that from corn starch by5.3%. |
PDF Full Text Request