Experimental Study On Structural Characteristics And Mechanical Behavior Of Oil-rich Coal In Yushenfu Mining Area

Oil-rich coal can be converted into oil,gas and semi-coke through pyrolysis technology.It contains the properties of coal,oil and gas.Using it to get oil and gas is an major step to solve the problem of insufficient oil and gas in China.However,the exploitation and utilization of oil-rich coal in northern Shaanxi has not yet formed large-scale production.One of the limiting factors is:under the current coal mining technology,the extracted coal covers much pulverized coal and fine coal,and the lump coal output rate is low.The oil extracted by low-temperature dry distillation has high impurity content.To improve the mining rate of oil-rich lump coal,it is necessary to systematically master the pore structure,composition and strength of the oil-rich coal in northern Shaanxi,and it can provide a basic parameter for the later improvement of mining techniques and methods.Accordingly,this article relies on the key project of Shaanxi Provincial of "Study on the Formation Mechanism and Nonpolluting and High-efficiency Utilization of Oil-rich Coal in Northern Shaanxi"(No.:2019JL-01).First carry out the test of oil-rich coal in the Yushenfu area coal maceral,industrial composition and pore structure and systematically grasp the micro-micro fabric characteristics of rich oil coal;then,carry out the static mechanical test and impact crushing strength test of rich oil coal to obtain the mechanical characteristics of the crushing strength of rich oil coal;finally,based on The correlation analysis of the structural characteristics and mechanical strength of oil-rich coal is to clarify the controlling factors that affect the formation rate of oil-rich coal lump coal during the mining and crushing process,and then reveal the dynamic mechanism of oil-rich coal crushing.The research results can provide a basic parameter for the later improvement of mining techniques and methods in northern Shaanxi.The main research results include:(1)Based on the analysis of oil-rich coal composition and industrial composition in Yushenfu mining area,coal samples N22,H42,H52 and Z52 are all highly volatile coals,and their typical characteristics are:the proportion of volatile content exceeds 30%,the proportion of fixed carbon>50%,while the proportion of ash and moisture is relatively small,only less than 10%.The microscopic components are mainly vitrinite and inertite,and the chitin and mineral components account for a small proportion.(2)Based on the analysis of the pore test data of the oil-rich coal in the Yushenfu mining area,the coal samples have extremely developed micropores,followed by small pores,and low development degrees of microporous and mesopore.However,the pore development characteristics of oil-rich coal samples in different regions are slightly different at various scales.Taking micropores as an example,the proportions of micropores in N22,H42,H52,and Z52 coal samples are 73.4%,58%,76.3%,and 59.9%,respectively.The comparison of different pore structure analysis methods shows that the liquid nitrogen adsorption method is suitable for characterizing the micro-pore characteristics of coal samples,while the mercury intrusion method is suitable for characterizing the large-scale pores of coal samples,and the nuclear magnetic resonance method can characterize the full pores of coal samples,but it is better than oil-rich coal.The water content is closely related and is not suitable for characterizing the pore structure of oil-rich coals in a dry state or with low water content.(3)There are certain differences in the static mechanical properties of oil-rich coal in Yushenfu mining area.Among them,the compressive strength is ranked as N22 coal>H52 coal>H42 coal>Z52 coal,and the relationship between the tensile strength is H52 coal>Z52 coal.For coal sample>N22 coal sample>H42 coal,the order of shear strength is N22 coal>H42 coal>H52 coal sample>Z52 coal.(4)The overall appearance of the anti-shattering ability of oil-rich coal in Yushenfu mining area is as follows:Under different spatial development conditions,Ningtiaota coal samples have the strongest anti-fragmentation ability,followed by Hongliulin and Zhangjiamao coal samples;Under different coal seam conditions,the 2-2 coal seam has the best anti-fragmentation ability,and the 5-2 coal seam's anti-fragmentation ability is stronger than that of the 4-2 coal seam.(5)The structural characteristics of oil-rich coal have a great influence on the mechanical strength of crushing.Among them,tensile strength is greatly affected by ash;while the inert group and fixed carbon have influence on the mechanical properties of the coal sample.Both have an impact,and the porosity has the greatest impact on the crushing behavior.In terms of static mechanics,Impact crushing of large coal samples is mainly affected by tensile strength,while compressive strength have significant effects on impact crushing of small-size coal samples.(6)The characteristics of impact crushing of coal samples are mainly manifested in two forms:local crushing and whole crushing.Among them,the fragmentation height affects the local crushing of the coal sample,and whole crushing has a "threshold of crushing height".