Study On In Situ Biogas Upgrading And Its Reactor Design

As a renewable energy source,biogas has the potential to replace natural gas.It has become one of the important research directions to purify biogas in situ by hydrogenotrophic methanogenic.In this experiment,a series of studies were carried out to investigate the feasibility and purification effect of biogas upgrading in situ by using a self-designed new anaerobic reactor.And main works is as follows:(1)In anaerobic digestion experiment of food waste by adding exogenous hydrogen,the methane contentrations of Group A,B and C were 62.72%,19.09%and 26.56%,respectively.On the 5th day,the total acid content in Group C increased 15.95%relative to Group A,with the increase in acetic acid accounting for 47.1%of the total acid increase.(2)Four different metal powders were added to the mesophilic anaerobic fermentation experiment,then it was found that iron can effectively strengthen methane accumulation.After anaerobic digestion was stable,the average methane contentrations in the iron powder group and the control group were 85.20%and 67.56%respectively.The former improved 26.07%than the latter.And the highest methane contentrations in the iron powder group could achieve 98.87%at the end of anaerobic culture.Compared with the control group,the cumulative methane yield in the iron powder group improved 8.26%.The H2 reduced CO2 produced by the metal powder reduction reaction was converted into CH4 accounted for 12.67%of mathane growth.(3)In the process of designing a new anaerobic reactor,the Fluent software was used to simulate the flow field of gas-liquid two-phase flow,the number,width and spacing of baffle plates are investigated.It was concluded that the best combinations as the wideth was 31.5 mm,the distance between baffle plates was 75 mm and the number of baffle plates is 4.According to the three aspects of the velocity distribution of the vertical section,the gas volume fraction on the baffle plate's undersurface and the radial distribution of the hydrogen X in the lower surface of the flow plate.(4)The new anaerobic reactor applied in hydrogen-producing methane production.As a result,the average mathane contentrations was 66.39%,and the daily mathane yield was 0.73 L/d before upgrading.After upgrading the maxium mathane contentrations was 86.74%,and the daily mathane yield was 0.94 L/d,the contribution rate of mathane production by hydrogenotrophic approach increased from 17.16%to 29.21%,the conversion rate of hydrogen increased from 46.87%to 90.45%.Therefore,the hydrogenotrophic methanogenic reaction can significantly improve the mathane contentrations in the biogas.In the view of microbial community structure,the hydrogenotrophic methanogens were effectively enriched,while the acetoclastic methanogenesis methanogens were still dominant but their relative abundance showed a significant decline.