Study On Start-up And Operational Parameters Of Biohydrogen Production In CSTR Reactor

Energy from hydrogen is widely appreciated in the energy, field because of its prominent advantage of cleanness and high efficiency etc. The technology of biohydrogen production has many advantages such as not consuming fossil resource, low cost and so on. It is a new technology which accords with the strategy of continuous development. Among the ways of biohydrogen production, biohydrogen production from fermentation is more prominent than biohydrogen production from photosynthesis because of its better stability and ability of hydrogen production. Therefore a lot of research has been done on biohydrogen production from fermentation. The common fermentation types of biohydrogen production from fermentation include propionic acid type fermentation, butyric acid type fermentation and ethanol type fermentation, and the last is regarded as the optimal one for the biohydrogen production from fermentation process. Ethanol and acetic acid are the liquid primary product of ethanol-type fermentation which has achieved the highest quantity of biogas and content of hydrogen. Furthermore, ethanol type fermentation can keep the fermentation course of biohydrogen production from fermentation more steadily than the other two fermentation types.In order to make biohydrogen production from fermentation process achieved ethanol fermentation type as quickly as possible, control parameters of the start-up process were investigated by running different organic loading rate (OLR) and the theory of biohydrogen production from fermentation was discussed in this paper.The results indicated that hydrogen producing ability of aerobic activated sludge was stronger than non-handled sludge.In this paper, taking molasses as the substrate and COD of the influent was 10000 mg/L, temperature was 35℃, VSS was 17.74 g/L and VSS/SS was 63.72% after 2 weeks cultured. The sludge which had the high ability of producing hydrogen could used as inoculants.A certain acidogenic fermentation type could be obtained by controlling the organic volume loading rate (OLR) and the pH of biohydrogen production from fermentation process. When OLR was at about 16 kg COD/m~3d in the initial stage of start-up process with HRT 6h and 35±1℃, the effluent pH dropped below 4 rapidly. When the OLR turned into 8 kg COD/m~3 d, ethanol type fermentation would come out with the pH within 4.0-4.5. The reactor could reach the balance after 12d operation when the biogas was 3L/d with the pecentage of hydrogen 75.77%. The major production of liquid fermentation was ethanol and acetic acid indicated that the reactor achived the quick start-up of ethanol fermentation type successfully. However, when the OLR was much higher in start-up stage, a superacid state of biohydrogen production reactor would occur and it would result in the failure of start-up process. Based on the CSTR reactor achived the ethanol fermentation, the stability of the biohydrogen producing system was examined by the variation of OLR. When the OLR added from 8 kg COD/m~3 d to 24 kg COD/m~3 d, the system would reach another stability the COD removal was 20% and the biogas was 12L/d in 9 days. As the aim production, the total prodcution of ethanol and acetic acid accounted for 83% in the liquid fermentation production with ethanol 54%-59% which mainteined the feature of ethanol fermentation.