Study On The Fuel-Ethanol Production From Lignocellulose Materials And Wastewater Zero Discharge Technology

Environmental pollution and energy crisis have brought a large number of concerns on the research of fuel ethanol as a kind of clean and renewable energy. Wide range of lignocellulosic materials as raw materials for the production of fuel ethanol can effectively avoid the food crisis. But the process was complex, with high cost and environmental pollution. Forestry wastes such as corn straw was selected as the basic raw material for the ethanol production research, and the fermentation inhibition of the hydrolyzate from electro-catalytic hydrolysis treatment was controlled and separated. The mixed yeasts immobilized fermentation process was designed and biological flocculation wastewater treatment were constructed in order to realize wastewater zero-discharge.The inhibitory effects of the hazardous materials in lignocellulose acid-hydrolysates on glucose fermentation and yeast growth were studied. The results showed that acetic acid, furfural, formic acid, and phenol had the inhibition of growth and reproduction of yeast, and the four substances on the yeast growth inhibition strength was in the order of formic acid> furfural> phenol> acetic acid, at the same time, four substances inhibition on alcoholic fermentation was followed by formic acid> furfural> phenol> acetic acid. The yeast after domestication showed better stability.The inhibitory effects of the hazardous materials in lignocellulose acid-hydrolysates on xylose fermentation were studied. Through the growth curve of yeast and the fermentation rate, the inhibitions of the hazardous materials were measured. The result showed that these inhibitions could make the yeast stop their growth and fermentation. And the strain after domestication showed stronger anti-inhibitor capability than unacclimated strain.The detoxification of acid hydrolyzate was studied in this paper. CTS was confirmed as the biological flocculant which has a good detoxification effect. The detoxification process was that the hydrolyzate after filtration was treated to get the solution with pH of 6, and then 0.1 g/L CTS was added to the solution. After reaction, the solution was filtrated and the detoxification process was finished. The best detoxification rate was 78.5%. The Box-Behnken design was accurate, reliable and with practical value. The yeast showed good adaptability with hydrolyzate after detoxification.In order to achieve a higher ethanol fermentation capacity and faster ethanol fermentation rate, the co-immobilized fermentation was used. At the same time, the immobilized particles were modified. The result showed that the CTS-calcium alginate was the best immobilized material when the CaCl2 concentraion was 3% and particle size was 5.3 mm. The optimum fermentation conditions at 30℃and 150 rpm in shaking flasks were as follows:pH 5.03 and reducing sugar 82 g/L. The final ethanol concentration was 20.04 g/L. At the same time the fermentation of different yeast was compared. The ethanol yield of yeast fermentation under optimum conditions was in this order:CTS-calcium alginate immobilized mixed yeasts> Al2O3-calcium alginate immobilized mixed yeasts> free-state mixed yeasts> CTS-calcium alginate immobilized Saccharomyces cerevisiae> CTS-calcium alginate immobilized Pachysolen tannophilus> Al2O3-calcium alginate immobilized Saccharomyces cerevisiae> Al2O3-calcium alginate immobilized Pachysolen tannophilus> free-state Saccharomyces cerevisiae> free-state Pachysolen tannophilus.In the present study, a wastewater treatment system for the ethanol fermentation industry was developed by recycling distillery wastewater and the wastewater zero discharge was achieved. Bio-flocculation was shown to be an effective way to diminish the content of inhibitory compounds drastically when the waste was recirculated. The recycle of wastewater without flocculation showed negative effects on ethanol yield as recycling was repeated. This new process was confirmed to have stable operation over ten recycles.Exploratory study of lignocellulosic cyclic catalytic treatment was studied. The lignocellulose materials was treated by 70% concentrated sulfuric acid at 80℃to get a gel state and then the acid was diluted to 35% and the reaction was continued for one hour at boiling situation. The filtrate was treated by stong acid resin to get the acid and sugar separation. And the result showed the final separation of sugar and acid reached a certain extent.