The Study Of High Efficient Biogas Fermentation Of Straw

Based on corn and wheat straw for materials, setting 30℃, 35℃and 40℃three medium temperature gradient and 48℃, 54℃, 51℃and 57℃four high temperature gradient, we studied the anaerobic digestion biogas potential and characteristics, and determined the appropriate temperature as dynamic anaerobic digestion operating temperature. Then on appropriate temperature, we studied the fermentation reactors and control conditions of dynamic fermentation, and pursued the supreme gas yield of per unit digester volume. Main conclusions are as follows:(1) The best fit temperature range of medium temperature static anaerobic fermentation is 35～40℃. The biogas yield of corn and wheat straw at 35℃are 0.492m³Â·kg^-1 and 0.499m³Â·kg^-1 respectively; 0.515m³Â·kg^-1 and 0.517m³Â·kg^-1 respectively at 40℃. The best fit temperature range of high temperature static anaerobic fermentation is 51～54℃. The biogas yield of corn and wheat straw at 51℃are 0.572m³Â·kg^-1 and 0.576m³Â·kg^-1 respectively; 0.528m³Â·kg^-1 and 0.530m³Â·kg^-1 respectively at 54℃.(2) The proper fermentation temperature of medium temperature dynamic anaerobic fermentation is 40℃. Under 40℃, SRT17～18d, gas yield of per unit digester volume of the ideal state is 2.3～2.4m³Â·m^-3·d^-1, biogas yield is 0.41 m³Â·kg^-1. The proper fermentation temperature of high temperature dynamic anaerobic fermentation is 51～54℃. Under 51℃, SRT17～20d, gas yield of per unit digester volume of the ideal state is 2.3～2.7 m³Â·m^-3·d^-1, biogas yield is 0.46 m³Â·kg^-1. Under 54℃, SRT14～15d, gas yield of per unit digester volume of the ideal state is 2.8～3.0 m³Â·m^-3·d^-1, biogas yield is 0.42 m³Â·kg^-1.(3) Dynamic anaerobic reactors present "upper straw-lower liquid sludge" distribution, thus we design a top mouth for the bottom material feeding reactor and a low mouth for the top feeding reactor.(4) For top feeding reactor, appropriate stiring can significantly increase the biogas production, the average gas yield of per unit digester volume improved 65%.(5) Relative to the bottom feeding reactor, top material feeding reactor showed no operation advantagement. We suggest that straw dynamic anaerobic fermentation can use "bottom feeding-upper discharging" pattern without stirring.(6) Under SRT17d, the highest organic load of high temperature (52±1℃) and medium temperature (39±1℃) dynamic anaerobic digestion is 4.71 kgTS/(m3·d), supreme gas yield of per unit digester volume are 1.92m³Â·m^-3·d^-1 and 1.63m³Â·m^-3·d^-1 respectively, biogas yield are 0.41 m³Â·kg^-1 and 0.35 m³Â·kg^-1 respectively. Gas yield of per unit digester volume and biogas yield of the high temperature anaerobic digestion increased 17%. Considering the cost of heating, we suggest that the feasible fermentation temperature of large straw biogas project is 40℃.