Influence Of Inorganic Mineral Components In Daliuta Changyan Coal On Biogas Formation

China has important biogenic coal-bed methane reservoirs.In the context of seeking to efficiently develop my country’s abundant lignite resources,the use of microorganisms to convert lignite into methane is getting more and more attention from researchers.However,there are few reports on the role of inorganic mineral components in coal in the process of coal biogas formation.This paper selects the long-flame coal from Daliuta,Shaanxi Province as the research object,and takes the mixed microorganisms collected from anaerobic sludge as the starting flora.First,the coal of different density levels is obtained by the method of large floatation and sinking of the coal,and the physical and chemical properties of the coal are characterized.Through the biological gas production test,the influence of coal of different density grades on biological gas production is analyzed,and representative minerals that may have an impact are screened out,and then the influence mechanism of several representative minerals on biological gas production is studied.In the coal ups and downs experiment,Daliu Tower long flame coal was prepared into 5 pieces,including 1.3-1.4 g/cm³,1.4-1.5 g/cm³,1.5-1.6 g/cm³,1.6-1.7 g/cm³,1.7-1.8 g/cm³,etc.Coal samples of different density levels are characterized by industrial analysis,XRD,XRF,and infrared spectroscopy to characterize the differences in physical and chemical properties of the five density coal samples.The results show that the ash content in coal samples of various density levels increases with the increase of the density level,and the fixed carbon content presents the characteristics of higher coal samples at low density levels and lower coal samples at high density levels,and low-density coal samples（1.3-1.4 g/cm³）,medium-density（1.5-1.6 g/cm³）,and high-density（1.7-1.8 g/cm³）coal samples have detected three minerals:quartz,calcite,and kaolin.As the density level increases,the content of calcite,pyrite,and aluminosilicate minerals in the coal also increases.From low-density level to high-density level,it represents the peak average of alkane C-H stretching vibration（2850,2919,2920,2966）,hydroxyl-OH or amino-NH-（3430,3342）and ether C-O stretching vibration（1227,1267）Disappeared,It shows that as the density level of coal samples increases,the corresponding functional groups in the coal also tend to decrease.The biological gas production test of coal samples of different density grades showed that the ash,volatile matter,and fixed carbon content in the coal have a significant impact on the cumulative methane production.Among them,the ash content and fixed carbon content have an extremely significant effect（p<0.05）.The content of five elements such as Fe,Ti,K,Ca,Sr,etc.has a significant impact on the cumulative methane production.Combined with XRD analysis,it can indirectly show that the presence of pyrite,calcite,and kaolinite has a significant effect on biomethane production.For the lower ash group（1.3-1.4 g/cm³,1.4-1.5 g/cm³）and the higher ash group（1.6-1.7 g/cm³,1.7-1.8 g/cm³）,the bacteria and archaea in the two groups are multi-species Differences between groups were tested,Desulfobacterota in bacteria at the phylum level and Geobacter,Clostridium,Smithella and norank＿f＿＿Bacteroidetes＿vadin HA17（belonging to pseudobacteria）in bacteria at the genus level The distribution of 5 genera in the lower ash group and the higher ash group,including Methanofollis in the phylum Bacillus and Archaea,has a generally significant statistical difference（p<0.05）,which may have caused the difference in gas production between groups.Six different mass fractions of pyrite,kaolin,and calcite were added to the coal biogas production system to determine the dynamic change of CH₄ content during the gas production process,the VFA concentration in the fermentation broth after gas production,and the activity of coenzyme F₄₂₀.As an evaluation index,to study the influence of the addition of different minerals on coal biogas production.The results show that the addition of pyrite in the anaerobic system promotes the production of VFA and increases the activity of coenzyme F₄₂₀ in the fermentation broth.However,the addition of pyrite in the anaerobic environment will inhibit the production of gas for a period of time（29 days）.The rate of coal bio-production of CH₄ may be related to the hindrance of the production of methanogenic precursors.The addition of kaolin at about 2%is most conducive to the process of gradual decomposition of coal by microorganisms.The addition of kaolin can increase the activity of coenzyme F₄₂₀ in the fermentation broth.The addition of calcite can inhibit the bio-utilization process of coal in an anaerobic environment,and its coenzyme F₄₂₀ activity is approximately normally distributed among the addition gradient groups.Less calcite addition（0.5%,1%）or more（8%）is not conducive to the production of coenzyme F₄₂₀.The final gas production results show that the addition of calcite can promote the biological CH₄production of coal.In the process of gas production,the alcohol or phenol-OH or-NH-,-NH₂ on the surface of the coal is cut off.The addition of the three minerals had certain effects on the species diversity of bacteria and archaea in the process of coal biogas production.As for bacteria,Firmicutes,Bacteroidota and Campilobacterota were the three phyla with the highest content in the gas production system of the pyrite test group.However,Firmicutes,Desulfobacterota and Bacteroidota have the highest content in the gas production system of the kaolin test group and the calcite test group.At the genus level,Proteiniphilum and Paraclostridium are relatively rich in the gas production system in the pyrite and calcite experimental groups,while Desulforhabdus is relatively rich in the kaolin and calcite experimental groups.In addition,Geobacters with high abundances have been detected in the gas production systems of three experimental groups of exogenous minerals.Therefore,the addition of pyrite,kaolin,and calcite has a certain effect on the activity of key enzymes in the process of coal biogas production and the degree of utilization of coal by microorganisms.These effects together determine the final methane production.The paper has 33 pictures,14 tables,and 95 references...