Biogas Production Rfom Corn Stover In An Intergraded Two-phase Anaerobic Reactor

Since energy crisis and environmental pollution have become the restriction factors ofhuman social development, many countries have attached much attention to explore highefficiency, low carbon and renewable energy. As a kind of quantitative, low cost and easilyacquired agricultural wastes, stover-like biomass has presented the huge potential to serve asthe suitable substrate of new energy. However, low degradation efficiency has become thebottleneck during the common utilization process of stover-like biomass. Recently, two-phaseanaerobic digestion presents the advantages of low cost, environmental friendly, highefficiency for utilizing corn stover, thus the related researches and development are of greatapplication value and practical significances. On the base of this, the thesis includes threedifferent research works, i.e. the fermentation pretreatment of corn straw, biogas productionfrom corn stover in an intergraded two-phase anaerobic reactor and a pilot-scal design ofintergraded two-phase anaerobic reactor.For enhancing the fermentation efficiency of corn stover in two-phase anaerobic reactor,orthogonal tests were used to investigate the effects of important factors on acid and alkalipretreatment of corn stover. Experimental results indicated that temperature was the keyfactor in the process of acid and alkali pretreatment, and the saccharification efficiency of acidpretreatment was much higher than that of alkali pretreatment. The gas production by usingsaccharification liquid of acid pretreatment was slightly above the alkali pretreatment, and theproduction time was significantly shortened. In summary, the gas yield of acid pretreatmentachieved53ml/g-stover, which was about15.1times of alkali pretreatment. Acidpretreatment was proved to be the suitable method for treating corn stover.The gas production tendency of a small intergraded two-phase anaerobic reactor was alsoobserved. The modified start-up plan was put forward to make cheap molasses as thesubstitute substrate, and the corresponding start-up characteristics were studied. Theexperimental results show that: the sludge inoculation in acidogenic phase was set to9.7g-VSS/L, and the methanogenic reactor was inoculated by anaerobic sludge. The fast start-upprocess was successfully achieved within28days, and the gas release was observed at the14th day and the18th day for acidogenic reactor and methanogenic reactor, respectively. Theresults indicated that the rapid start-up can be achieved by using molasses as the substrate and mature anaerobic sludge.After the successful start-up period, the small intergraded two-phase anaerobic reactor wasused for corn stover laboratory level gas production experimental study. At the influent cornstover0.74g/L, volumetric loading0.678kg-COD/m3·d and HRT96h, the optimum gasyield was1.06L/d. The retention time of corn stover in acidogenic phase should be at least16h. Furthermore, the decrease of the corn stover size and the extension of HRT could increasethe utilization efficiency of anaerobic reactor. Experimental results indicated that theintergraded two-phase anaerobic reactor was of strong shock-resist ability. The methanogenicphase could steadily produce gas during substrate exchange, suggesting that this reactor formwas capable for the utilizaiton of complex substrate.For further discussing the bioenergy production characteristics of corn stover by two-phaseanaerobic digestion, intergraded anaerobic fermentation device was optimized and thenconstructed in pilot-scale. During the course of optimization, MATLAB software was used tore-design the insulation system. Based on the calculation results, the new insulation system ofonly568W could make the whole system meet the temperature requirements under the mostadverse working conditions. By using computational fluid mechanics methods, the Fluentsoftware was used to optimize sludge-stirring structure to enhance the performance of thereactor. By the design process, the universal computational methods were founded, and can beemployed to other kinds of anaerobic reactors after proper adjustment.