Effect Of Small Molecule Organics On Enhancing Gas Occurrence In Coal

Coal is a kind of complex organic rock which consists of not only macromolecule skeleton but also soluble small molecule organics. They inhabit in matrix pores and macromolecule networks. By adopting microwave extraction, this paper analyzed matrix pore structure and adsorption capacity of functional groups before and after extraction. And this paper tries to reveal the effect of small molecule organics on gas occurrence.THF played as solvent when committing microwave extraction. Gas chromatography and mass spectroscopy(GC/MS) were introduced to analyze extract, the change of functional groups in coal sample is analyzed by infrared spectrum. It was found that extract mainly contains aromatic hydrocarbons, fatty hydrocarbon and other compounds. Besides, extract was detected full of methyl, hydroxyl and carbonyl. The total content of functional groups decreases obviously after extraction,it is showed that small molecules organic in raw coal occupies a certain proportion, the contents of coal after extraction changes, and the pore structure and dissolved characteristics of coal are affected. After extraction, total pore volume and specific surface area of each residual coal decreased when comparing to their raw counterparts, but not mean pore size. Therefore, it is concluded that small molecule organics do help increase coal specific surface area.Methane isothermal adsorption experiment was performed to uncover methane adsorption pattern of coal before and after extraction. Relevant analysis shows that methane adsorption volume of each residual coal cannot reach the high level set by their raw counterpart previously. Therefore, it is way acceptable that small molecule organics do enhance methane adsorption capability of coal.After analyzing the proportion of various small molecule organics in coal, diesel oil, lubricating oil and coal tar were selected as similar models of small molecule organics to perform methane dissolution experiment. The outcome shows that methane dissolving volume goes up as gas pressure(ranging from 1 to 5MPa) increasing at 30℃. While on the contrary, when under identical gas pressure, methane dissolving volume goes down as temperature(30 to 70℃) rising.A combination of porous media, model materials and methane was established to simulate coal skeleton, small molecule organics and gas, respectively. Its methane isothermal adsorption experiment demonstrates that carrier with addictive, diesel and lubricants, adsorbs more methane. And larger diesel amount results more methane adsorption. Thus,it is reasonable to believe that small molecule organics can boost methane adsorption capacity of porous media.Based on pore system and adsorption pattern of raw coal and residual one, small molecule organic and its impact on coal pore structure and subsequent adsorption pattern change has been perspectively investigated. It was found that small molecule organics can enhance coal specific surface area and boost its gas adsorption capability. Meanwhile, as being capable of dissolving gas, small molecule organics and its abundant functional groups made it essier for gas adsorption. The joint force has made small molecule organics a catalyst to gas occurrence in coal seam consequently.