Experimental And Mechanical Research On Dry Anaerobic Digesfipn Of Corn Stover Pretreated With Eiogas Slurry

Dry anaerobic digestion has many advantages, such as wide range substrate source, high unit volume production ability, low water consumption and low moisture content in waste residue, but the low moisture content of substrate will lead to the difficulty in stirring and the slowness in mass transfer, which make the digestion process unstable. As a try to solve these problems, in this article, the effects of the pretreatment with biogas slurry and different fermentation parameters on dry anaerobic digestion results were studied by experimenting, and the changing regularity of each characteristic in the digestion of corn stover pretreated with biogas slurry was also studied, and a laboratory bench was designed and set up for the study of dry anaerobic digestion. Main research contents and conclusions are as follows:1. The corn stover pretreated with biogas slurry was used in the dry anaerobic digestion as substrate to research the effect of the pretreatment with biogas slurry. Results showed that though this pretreatment couldn't noteworthily increase the percentage of CH4in biogas, it could make the digestion speed faster, and the daily gas production bigger, and the cumulative gas of30days was44.22%more. Hydraulic retention time was shortened markedly and fermentation efficiency was improved.2. An orthogonal test was done at different initial pH, material bulk density, height-diameter ratio of fermentation tanks and inoculating pattern of inoculum, using corn stover pretreated with biogas slurry as substrate to optimize the digestion process. Results are as follows:the influencing degrees of initial pH and material bulk density were stronger than height-diameter ratio of fermentation tanks and inoculating pattern of inoculum, and the optimum technological conditions were initial pH at8, material bulk density in the range of0.55-0.60, height-diameter ratio of fermentation tanks at1:1and inoculating pattern of inoculum was quinquesection of both substrate and inoculum. All the parameters had significant effect on basicity, but not on pH. Initial pH, material bulk density, height-diameter ratio of fermentation tanks had significant effect on TS, VS, but not the inoculating pattern of inoculum. Initial pH, material bulk density and inoculating pattern of inoculum had significant effect on the shift of CH4percentage, daily gas production and cumulative gas, but not on the shift of CO2percentage, and the height-diameter ratio of fermentation tanks acted in the opposite wav.3. The substrate and inoculum were layered in fermentation tanks in the dry anaerobic digestion of corn stover pretreated with biogas slurry to research the changing regularity of each substrate characteristic. The results were:the material characteristics of the substrate and inoculum had different variation trend. And the upper substrate was very different from the underneath substrate in the variation trend of TS and VS, though they had similar trend in the shift of pH and basicity, they were obviously different in degrees. The percentages of CO2and CH4had different variation trend. Daily gas production rapidly increased at first and decreased after the first peak on the third day, and the biogas was mainly composed of CO2, then it come to the stationary phase after another rapid increase, the percentage of CH4went up to50%gradually and kept stationary till the end of digestion process. The acetic acid in every substrate layer had similar variation trend, increased and decreased fast, the time when its concentration was0was same to the beginning of the stationary phase of gas generation because of the prompt utilization. No acetic or propionic acid were detected in inoculum. The trend of propionic acid was similar to the acetic acid, but the time when its concentration was0was same to. the beginning of the decrease of daily gas production. It suggested that in stationary phase the daily gas production was decided by acetoxylation speed, but in exhaustion stage it was decided by the hydrolysis speed of substrate and acidification speed principally.4. A laboratory bench which can realize the real-time on-line inspection of substrate temperature and pH and is convenient for sampling to analyze the substrate characteristic and biogas generationat any time was designed and set up for the study of dry anaerobic digestion.