| The condensate will be produced in the production process of ethanol and the Distillers Dried Grains with Solubles（DDGS）,when distilleries use corn or staled grains as raw materials,and the COD value of condensate is around 1 g·L-1,which make the condensate cannot be directly discharged.There is no doubt that the water resources can be fully utilized and the production cost can be reduced by reutilizing the condensate in ethanol fermentation,in order to realize the reutilization of condensate,the ozone oxidation combined with ion exchange method was explored in this thesis.（1）The results showed that when condensate was directly reutilized,it could reduce the ethanol yield by 19.4%.To elucidate this phenomenon,the by-product glycerin and yeasts number were determined.The results showed that the condensate could increase the yield of glycerin by 82.6%,and could decrease the yeast number by18.8%.（2）In order to realize the reutilization of condensate,the components of the condensate were analyzed subsequently.The results showed that the total number of alcohols,furans and organic acids in condensate reached to 60,which take up a ratio of 53.3%.In order to determine the substances which could inhibit ethanol fermentation in the condensate,the inhibition of phenylethanol,furfural,acetic acid,propionic acid,butyric acid,valeric acid and hexanoic acid to ethanol fermentation were measured.The results of response surface experiment showed that there was a synergistic effect among inhibitors.It was also found that acetic acid,propionic acid,butyric acid,valeric acid could increase the final ethanol yield of1.3%,4%,1.7%and 3.9%respectively without affecting the fermentation rate.（3）In order to realize the reutilization of condensate,ozone was used to treat the condensate.The results showed that the contents of inhibitors phenylethanol and furfural in the condensate decreased 99.5%and 100%respectively and the concentration of acetic acid and propionic acid increased by 13.3%,22.4%respectively after oxidation.The inhibition of oxidized condensate alleviated but due to the excessively accumulation of organic acids,it could not completely eliminated.The organic acids became the main inhibitors in condensate after ozone oxidation.（4）D303 anion resin was used to eliminate the negative influence of organic acids,while the ratios of residual acetic acid and propionic acid were 77%,73.2%respectively,the condensate treated by ozone oxidation combined with ion exchange（IE）can increase the ethanol yield by 2.5%.In order to investigate the reasons of the promotion effect on ethanol fermentation by condensate treated by ozone oxidation combined with ion exchange,the activity of yeasts were statistically analyzed.The results showed that the condensate treated by ozone oxidation combined with ion exchange could increase the yeasts number equate to90%of the control.Also increased the proportion of active yeasts’cells from 90%of the control to 95%.Therefore,the ozone oxidation combined with ion exchange can realize the total reutilization of condensate. |
