Study On Heating And Deformation Effect Of Coalbed Methane Exploitation

Coalbed methane whose main component is methane,is an efficient,clean energy which is associated with the coal and mainly occur in the state of adsorption.Meanwhile,gas disaster is one of the great hidden hazards of coal production safety.In addition,coalbed methane is a kind of devastating greenhouse gases towards the ecological environment.Therefore,the rational exploitation and utilization of coalbed methanes is crucial in the related fields of energy,security,ecology and so on.In the process of CBM exploitation,the gas undergo the desorption from the surface of coal and the diffusion and flow in the pore structure and fracture structure of coal.In the process of the desorption from the surface of coal,the gas will absorb some heat named adsorption heat.The adsorption heat will drop the surrounding temperature and hinder the desorption ability.In the process of desorption,diffusion and flow in the coal,the coal body will generate shrinkage deformation.The shrinkage deformation will change the channel of the diffusion and flow.As far as the coal structure without destruction,coalbed methane mining methods mainly include:methods of reducing pressure and increasing temperature.The pressure and temperature is an important indicator of the CBM process,and the study of pressure and temperature’s variation can effectively predict gas desorption.Therefore,the study of heat effect and the deformation effect in coal adsorption(desorption)is important to CBM exploitation.This paper has done the following works:(1)Microscopic mechanism of condensation heat,adsorption heat and deformation’s generation was expounded systematically.The physical nature of the condensation and adsorption phenomena was revealed.(2)Cited two-energy-state model to calculate adsorption heat,and gave a clear physical picture.(3)On the basis of the Langmiuir monolayer model,from perspective of adsorption,the fractal features of coal surface was studied,the two-dimensional flat surface adsorption to the fractal surface adsorption was extended,and a fractal dimension based on De Broglie thermal average wavelength was got.(4)The adsorption heat and deformation when coal is adsorbing gas are measured with direct and indirect experimental methods.(5)Cite dimensionless quantities to choose theory model,and pointed out the relationship and difference among the various models.(6)Point out the adsorption heat can predict gas reserves.(7)The adsorption heat of different types of coal towards the same gas is different,and the adsorption heat of the same types of coal towards different gas is different.(8)The adsorption heat of coal towards methane and carbon dioxide was got by measured experimental methods.The adsorption heat of different types of coal towards methane is got through isovolumetric desorption experiment.Under standard atmospheric conditions and at room temperature,the adsorption heat of Xiangning coal is-9.87kJ/mol,the adsorption heat of Tunliu coal is-13.72kJ/mol,the adsorption heat of Kaiyuan coal is-14.07kJ/mol.The adsorption heat of anthracite towards carbon dioxide is-12.71kJ/mol through measuring equipment of temperature and deformation effect.(9)In a certain range,there is a positive relationship between two of temperature,deformation and adsorbance.(10)In the process of absorption,surface energy decrease and turn into adsorption heat and deformation energy.