Study On The Enhancement Of Biogenic Methane In Coal Seam Using Stmw Biomass

Coal bed methane（CBM）is a kind of clean and high quality unconventional natural gas resource.Its exploitation and utilization can alleviate the tense energy situation in China.Therefore,some people put forward the technology of increasing coal bed methane production by microorganism,using anaerobic microbial flora to degrade coal to increase coal bed methane,at the same time,the degradation of coal can improve the permeability of coal to a certain extent,thus improve the extraction rate.However,there are still many limiting factors in the study of increasing CBM production by microorganism,including the complexity of coal structure,the difficult degradation of coal molecules,and the instability of microbial community activity.In this paper,the anaerobic co-degradation of straw biomass with coal is proposed to maintain the activity of microbial community and to promote the degradation of coal molecules,thus improving the production efficiency of bio-coalbed methane.In this paper,the high efficiency methanogenic bacteria enriched in water from coalbed methane field in Qinshui Basin were used to decompose rice straw with high order coal,middle rank coal and low rank coal with different mass ratio.Combined with SEM technology,the co-degradation of straw and coal could promote the production of bio-methane,and the best mass ratio of coal to straw with different coal rank was determined.Rice straw,corn straw,sweet sorghum straw and wheat straw were selected for anaerobic co-degradation with high-order coal.On the basis of this,the two kinds of straw were pretreated separately to select the best straw addition scheme to promote the co-degradation of methane.The results show that:（1）In the process of anaerobic co-degradation of rice straw and coal with different rank of coal,biomethane production can be promoted significantly.For high-order coal,adding a small amount of straw can produce more biological methane,and the highest methane yield can reach 1001.27 mol/g coal,which is2029.80 higher than that of the control group which is degraded by coal alone.The results of SEM also showed that there was a synergistic effect in codegradation of rice straw and coal.（2）The co-degradation of four kinds of straw and high-order coal can promote the production of bio-methane,among which the rice straw and sweet sorghum straw have the best promoting effect,which can increase the methane yield of coal degradation by 1355.32%and 870.21%,respectively.At the same time,the result of CO2 is that CO degradation can reduce the production of CO2while promoting methane production,and promote the utilization of carbon.（3）For sweet sorghum straw pretreatment,NaOH pretreatment is better than H₂SO₄ pretreatment,and the lower the concentration of pretreatment solution,the better the pretreatment effect.The co-degradation of straw and coal after 2%（w/w）NaOH pretreatment not only increased the methane yield of coal degradation,but also increased 55.92%compared with untreated ones.After pretreatment with H₂SO₄ solution,the methane yield was higher than that of coal degradation,but lower than that of untreated methane.（4）The methane yield of rice straw co-degraded by NaOH and H₂SO₄ was higher than that of coal,and the lower the concentration of the solution was,the better the methane yield was.However,for the two pretreatment methods,the yield of co-degraded methane after pretreatment was lower than that of untreated ones,which indicated that pretreatment was not suitable for co-degradation of rice straw and coal.Co-degradation of straw biomass with high-order coal can significantly promote methane production,and different straw can promote methane production.The optimal results are sweet sorghum straw and rice straw.For pretreatment,sweet sorghum straw after alkali treatment was the best,and also improved compared with no treatment.