Experimential Study On Physicochemical Properties And Molecular Simulation On Methane Adsorption Properties Of Gas-outburst Coal In Guizhou Area

Gas disaster is not only the major disaster in Guizhou province but also in thewhole country. Coal mining disasters become more and more serious as the miningdepth increases. The gas disasters severely impact the safety of coal mining industry.Gas disaster is a complicated problem and the coal and gas outburst mechanism is stillnot completely clear. But, it is generally believed that the physical properties of coal,the gas in coal seam and the ground stress are the three major factors that impact thegas disaster. However, every factor is synthetically influenced by the many combinedfactors. This paper investigates the physicochemical properties of the outburst coal inGuizhou province by the method of theoretical analysis, physical experiments andnumerical simulation. The gas prevention and control technology is proposed basedon the physicochemical properties of outburst coal.The locations of experiment samples were determined by analyzing theformation and distribution law of the outburst coal in Guizhou province. SinceGuizhou province is influenced by the coal accumulating basin, the sedimentaryenvironment, the coal forming conditions, the geological movements, the coalcontrolling structures and other factors. Its major coal rich zones are Liupanshui coalfield, Zhina coal field, Qinbei coal field, Xinyi coal field, whose coal seams aremostly the outburst coal seam.Through the aspects of industrial analysis, elemental analysis, macromolecularstructure analysis, destruction type, microstructure, pore structure, specific surfacearea, the physicochemical properties of the samples in Guizhou province wereattainted by the field test and laboratory test. The outburst coal of Guizhou province ismostly the strongly destructive type of class Ⅲ coal. There exists crystal substancesparallel to the stratification plane, and many pores or fractures exist in stratificationplanes and joint planes, whose apertures are generally between0~10nm. Amongthem, apertures between3~5nm are the most common, which are the most importantgas adsorption space.Adsorption theory and molecular simulation models were adopted to investigatethe properties of methane adsorption on the coal. According to the methane adsorptioncharacteristics of the outburst coal in Guizhou province, the molecular adsorptionmodel was adopted based on the physical model of slit pore and the adsorptionmechanism of microporous filling. Using the Monte Carlo simulation method in grandcanonical system, the adsorption and desorption of coal methane molecules was realized through the insertion and deletion of particles, and so were the influence lawof aperture, temperature, ash content, moisture and other factors on methaneabsorption.The software specifically for methane adsorption was developed. Comparing theresults of molecular simulation with physical test, the adsorption isotherms areconsistent. By using the molecular simulation software, the simulation of methaneadsorption was made under the conditions, in which the data were based on the fieldtest and laboratory test. Simulation results show that the porosity of the coal, thetemperature, the content of ash and water all have influence on the adsorptioncharacteristics of coal. Among them, the ash content is the most important one.From the aspect of molecular lever, the research results provided a new way tofrom the Angle of molecular predicting the adsorption characteristics of coal, andimproved the reliability of the molecular simulation technique, which could be used toprovide theoretical basis for forecasting gas pressure, gas content and other gasparameters.