Change and mechanism of liquid phase products in coal fermentation cogeneration of hydrogen and methane

The cogeneration of hydrogen and methane,with coal as substrate,is an exploratory biological fermentation technique. This research can provide a reference for the liquid products utilization with high additional value in coal and the improvement of biogas-producing efficiency,further enriches the theory of biogenic gas production from coal. The simulation experiments of biogenic gas production were carried out by using the long flame coal and mine water from Qianqiu mine under the suitable environment. The gas production,intermediate liquid products were tested re- spectively by gas chromatography and gas chroma-tography-mass spectrophotometry for revealing the change character- istics and mechanism of liquid products. The results show that ① the maximum H2 ,CH4 production were 66. 29 μmol /g (3 d) and 55. 78 μmol / g (16 d),respectively,which accounted for 25. 78% ,and 25. 47% of the total H2 and CH4 production,respectively. The substrate conversion of coal reached 2. 4% and 4. 9% ,respectively;② At the hydrogen production stage,the pH shows a trend of increased-decreased-increased,the COD increased gradually within 7 d reac- tion period and the maximum value was 857. 82 mg / L (6 d),the maximum of OD600 was 0. 52 (4 d). The COD had significant change trend at the methanogenic stage and the maximum value was 873. 73 mg / L (15 d). The pH and OD600 kept a certain level. The change trend of pH,COD and OD600 is consistent with that the key intermediate liquid products,and the change of liquid products is an important internal factor for pH,COD and OD600 ;③ The volatile fatty acid, straight-chain alkanes, branched alkanes, alkene, oxygen-bearing and ni-trogenous organic compounds and pyrazine,prymidine heterocyclic compounds were accumulated in the co-production period. There were low content of straight-chain alkanes and branched alkanes at the end of hydrogen production experiment,their content reached to 67. 05 μg / mL and 21. 16 μg / mL,respectively. Neonatal organic compounds such as cycloalkane,nitrile,hydrazine,4- methyl-9H-fluorene and more straight-chain alkanes (maximum value was 216. 63 μg / mL),branched alkanes (maxi- mum value was 112. 28 μg / mL),oxygen-bearing (maximum value was 110. 49 μg / mL) and nitrogenous organic com- pounds (maximum value was 108. 65 μg / mL) were formed in the methane production phase. The change characteris- tics of liquid products further reflects the cogeneration superiority of hydrogen and methane production with coal as substrate,which may improve the overall energy utilization of coal,and optimize the biogas generation process of coal.