Study Of Vhg Ethanol Fermentation And The Inhibitors In The Ethanol-methance Coupled Process

The practiced of ethanol-methane coupled process, could save plenty of water resources, and prevent wastewater discharging to the environment. We detected that there were inhibitors, which have negatively effect on the ethanol fermentation, in the anaerobic digestion effluent. The SO42-, which joined in the system to ensure that the mash adjusted to pH 4.0-4.2, would be harmed to the methane fermentation. As a result, we studied the inhibitors which would be have negatively effect on the ethanol-methane coupled process, and found solutions to the problems. This paper provides fundamental base for the further industry production of the ethanol-methane coupled process.The effect of propionic acid on the ethanol fermentation depend on the concentration of propionic acid and the initial medium pH. Under the moderate concentration of propionic acid, the final ethanol concentration increased 7.6%compared to the control. Conversely, the biomass production decreased 76%, the glycerol production decreased 39.6%compared to the control as well as. However, when the propionic acid was high, the ethanol fermentation was inhibited totally. At the same concentration of propionic acid, the inhibition of propionic acid to the ethanol fermentation would be enhanced with the pH of the mashing depressed.The dosage of sulfate reduced by 50%through elevating the initial medium pH to 6.0 in the simultaneous saccharification and fermentation (SSF) without pre-saccharification, resulted in the concentration of sulfate under 3 g/L, which was safe to the methane fermentation. The very high gravity ethanol fermentation conditions:cassava mixed water at 1:2.2 (w/w) ratio, the dosage of glucoamylase was 140 U/g cassava, fermentation time 54 h, and the final ethanol concentration was 14.7%(v/v). In the optimized process, the glucoamylase dosage increased 20 U/g cassava compared to that in the traditional process.The VHG ethanol fermentation not gone as well as the regulation when the ethanol-methane coupled process working, especially, at the fourth to eighth batch, the starch utilization rate was only 80%. However, the cycle went more stable after the methane fermentation rearranged. This cycle has been operated 15 batches, the fermentation time was 54 h, the final ethanol concentration was above 14.5%(v/v), and the starch utilization rate was above 87%. The performance of the water for mashing had been rapidly accumulated at the prophase of the cycle, however, which had been stabled after the methane fermentation rearranged, such as the concentration of COD, NH4+-N, alkalinity and the concentration of inorganic ions.The effect of inorganic ions, such as Ca2+, Na+, Mg2+, K+, on the ethanol fermentation were determined. It was shown that the inhibit concentration of Ca2+was 10 g/L, and the inhibit concentration of Na+was 5 g/L. The final ethanol concentration had been increased when the concentration of Mg2+below 5 g/L, and the effect of K+ on the ethanol fermentation was not obvious.