| Both anaerobic digestion and gasification are regarded as one of the best available technologies for either digestible or refractory biomass resource recovery in terms of biogas and syngas respectively. However, biogas and syngas （consists mainly of CO, CO2, and H2） belong to low quality fuel gas, it cannot be efficiently utilized if only via upgrading and purification. One of the important ways of biogas upgrading was using the principle of hydrogenotrophic methanogenesis to make conversion of CO2 to CH4. A novel technology was proposed for simultaneous biogas upgrading and syngas utilization in one anaerobic reactor, which made use of syngas as the additional hydrogen source for microbial upgrading.Three steps were designed to assess the feasibility of biologically simultaneous biogas upgrading and syngas utilization. Batch and long-acclimated experiments were done firstly as the preparation research to investigated the degradation performance of CO on anaerobic microorganisms and the feasibility of syngas methanation. Secondly, the effects and mechanism of simultaneous utilization about three kinds of sludge were studied under the condition of simulated gas, which employed compounded biogas and syngas as sole carbon source. Finally, experimental system of simultaneous biogas upgrading and syngas utilization was established to investigate the effects and problems of this technical route, while continuous stirred tank reactor （CSTR） was operated with restaurant garbage as substrate, upgrading ractor was operated by using syngas as external hydrogen source. The main results of this study were outlined as follows.（1） CO could be degraded by anaerobic microorganism completely and the time required was positively related to initial CO concentrations. Sludge types and gas-liquid mass transfer were the restrictive factors to syngas degradation, the degradation effect of three types sludge was granule sludge, carbon felt-based biofilm, and flocculent sludge respectively. CO had explicit inhibition on flocculent sludge microbes and the inhibition declined significantly after long-term cultivation. Three sludges could degraded syngas completely in 1.0 d with the product of CH4. Syngas seemed to be degraded mainly via acidogenic bacteria for flocculent sludge. Nevertheless, degradation of syngas by anaerobic granules and carbon-felt based biofilm were possibly attributed to syntrophic operation of acidogenic bacteria and methanogens.（2） For flocculent sludge group, the content of CH4 was 85%、82% with hydrogen source of pure H2 and syngas respectively, which showed the feasibility of simultaneous utilization preliminarily. The best results of methanation for simulative gas was granule sludge group, besides, the content of CH4 reached 93% in mixture under steady operation stage, which showed great promise in simultaneous biogas upgrading and syngas utilization.（3） At practical biogas-production of simultaneous utilization experiment, the content of CH4 reached 93% in mixture, which with the starting load of 0.5 gVS/L-d for anaerobic digester reactor, with the syngas flow of 2.20 L/d. Furthermore, the concentration of CH4 also remained more than 80% at high-load phase. The pH of up-grading reactor was 7.5-8.5, effective alkalinity was 3900～5000 mg/L during the experimental period of 110 d, basically realizing a long-term stable operation of the simultaneous utilization system. |
PDF Full Text Request