煤发酵联产氢气-甲烷过程液相产物变化及其机制

以煤为原料进行氢气-甲烷联产是一种具有探索性的生物发酵工艺,研究该工艺发酵过程液相产物变化和机理可实现对煤中高附加值液态产物的利用与产气效率的提高,并进一步丰富煤生物产气理论。以义马千秋矿长焰煤为研究对象,义马煤层矿井水为菌种来源,在适宜环境条件下开展联产模拟实验,并运用气相色谱法,气质联用法等对联产过程中的气体组分、中间液相产物等进行检测分析,以揭示其液相产物变化特征及其机制。结果表明:①H_2和CH_4高峰期产量分别为66.29μmol/g(第3天)和55.78μmol/g(第16天),分别占H_2与CH_4总产气量的25.78%和25.47%,反应结束后产氢、产甲烷的底物转化率分别为2.4%和4.9%;②产氢阶段的pH呈现出先增加后降低又增加的趋势,COD在反应周期内逐渐升高,在第6天时出现最大值857.82 mg/L,而OD_(600)在第4天达到最大值0.52。产甲烷阶段的COD变化趋势明显,在第15天时达到最大值873.73 mg/L,pH,OD_(600)则维持在一个相对较为稳定的范围内。pH,COD与OD_(600)的变化过程与关键有机中间液相产物的变化特征一致,液相产物的生成、降解直接地影响了pH,COD与OD_(600)的变化趋势;③产氢阶段和产甲烷阶段均有挥发性脂肪酸、直链、支链烷烃、烯烃、含氮、含氧有机物及吡嗪、嘧啶类杂环化合物积累,产氢结束后的直链烷烃、支链烷烃含量较低,分别是67.05μg/mL和21.16μg/mL,且残留有大量的丁酸、丙酸等挥发性脂肪酸(332.63μg/mL),经产氢预处理之后的煤样为产甲烷过程提供了更多的有效可利用体,且产甲烷过程在液相产物中检测到更多的直链(最高为216.63μg/mL)、支链烷烃(最高为112.28μg/mL)、含氧(最高为110.49μg/mL)、含氮大分子有机物(最高为108.65μg/mL)及环烷烃、腈类、腙类、4-甲基芴等新生有机物。联产过程的液相产物变化特征进一步反映了煤发酵联产氢气-甲烷的优越性,有可能提高煤的总体能源利用率并优化产气过程。

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 respectively by gas chromatography and gas chroma tography mass spectrophotometry for revealing the change characteristics 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 reaction 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 (maximum value was 112.28 μg/mL),oxygen bearing (maximum value was 110.49 μg/mL) and nitrogenous organic compounds (maximum value was 108.65 μg/mL) were formed in the methane production phase.The change characteristics 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.