Study On Enhancing Biogenic Coalbed Methane By Chemical Pretreatment

As an unconventional energy resource,the exploitation and utilization of coalbed methane can greatly reduce the exploitation cost of coal resources.On the other hand,it can ensure the sustainable development of energy resources.Coalbed methane can be divided into two kinds according to their forming reasons: biogenic coalbed methane and thermogenic coalbed methane.It is generally believed that the generation process of biogenic CBM in coal seam is mainly composed of the origin of methanogens macromolecular organic compounds in coal gradually transformed into small molecular organic compounds,and then converted into bio methane.Therefore,biogenic coalbed methane can realize "regeneration" of coalbed methane to a certain extent.It plays an important role in changing the energy structure of "rich coal and less gas" in China,and is of great scientific and practical significance.However,its low efficiency gas producing,seriously limits the development of biological coalbed methane industry.At present,it is generally accepted that the limiting factors of biodegradation of coal are the complexity and degradability of coal structure.In order to improve the efficiency of coalbed methane production,in this paper,an effective method is adopted to pretreat coal before biotransformation,to reduce the complexity of coal molecules and enhance the biological effectiveness of coal molecules to improve the efficiency of biological coalbed methane production.This article from the output of coalbed methane in the Qinshui Basin water obtained by using the method of anthracite degrading bacteria subculture,enrichment,and optimal growth conditions were determined by FTIR? X-RD? GC-MS technology,through 3 aspects of coal,functional groups,nucleus degradation,intermediates are analyzed to study the degradation mechanism of bacteria.Based on the study of the biological methane yield increasing effect of different concentrations of nitric acid,Potassium Permanganate,hydrogen peroxide,sodium hydroxide pretreatment of coal to gas production as the core of the evaluation index,select the optimal pretreatment conditions,and analyzed the pretreatment and subsequent gas production in the process of functional groups and the change of coal nuclei by FTIR?X-RD technology,a preliminary analysis of the pretreatment mechanism of biogenic methane production.Findings are as follows:?1?Successful breeding of high efficient bacteria degradation of anthracite,the best gas production conditions are as follows: temperature is 35?;saluity is 1.1%¹.2%;particle size is 0.15⁰.25mm;.PH is 8⁹;coal?g?and bacteria?ML?ratio is 1:5;optimal vaccination time is 20 d.In the degradation process of coal methane production,phenol,alcohol,ether,ester C-O stretching vibration and benzene skeleton vibration absorption peak area gradually decreases;crystal structure of coal decreases,the aromatic ring structure of coal expansion becomes loose;cultivate intermediate metabolites in liquid aromatic substances,long chain fatty acid,formic acid,acetic acid,phenol,alcohol,ether,ester material.The whole degradation process follows the model of anaerobic biological typical fermentation theory,that is,the large molecules of coal are constantly degraded into small molecules,and finally utilized by microorganisms to produce methane.?2?The best coal pretreatment conditions were as follows: 30% H₂O₂ treatment 12 h and 1.5M NaOH treatment 12 h,gas production increased by 12.5% and 15.5% respectively.?3?In the process of H₂O₂ pretreatment,coal group mainly decreases in substituted aromatic and benzene skeleton vibration absorption peaks,crystal structure of coal is mainly reflected in its volume reduction,this is the external molecules with hydrogen peroxide oxidation is the premise to complete,which is a small molecule the oxidation of the shedding process.In the process of NaOH pretreatment,coal group mainly decreases in the absorption peak of methyl,Ya Jiaji,this is the result of base mechanism,and the crystal structure of coal decreases,is mainly caused by the corrosive reason of sodium hydroxide.?4?Coal gas production process after H₂O₂ pretreatment in the coal group is mainly embodied in phenols,alcohols,ethers substance C-O absorption peak and absorption peak of the benzene skeleton vibration area is decreasing,indicating that after H₂O₂ treatment,phenols,alcohols,ethers and aromatic the material as the main gas producing matrix material is more easily used;crystal structure of coal showed a decreasing trend,suggesting that the microorganisms under the pile height and the ductility is reduced,which is corresponding to the degradation process of organic matter in coal methane production process.Coal gas production process after pretreatment of NaOH in coal is mainly reflected absorption peaks in the functional groups containing benzene skeleton vibration decreases,indicating that the coal macromolecular continuous degradation,and then transformed into phenol,alcohol and other substances,and then by using gas production;crystal structure of coal was decreased,but the reduction is not particularly significant.?5?H₂O₂ pretreatment can increase the coalbed methane,mainly because of its oxidation.NaOH pretreatment can increase the coalbed methane,which is mainly the result of alkali action.?6?The process of coal biodegradation is very complicated.It is effective to improve the efficiency of biological methane production by the pretreatment of coal before the bioconversion of coal.For example,H₂O₂ and NaOH are good for the production of biological methane.