【作者】 张哲；

【导师】 魏晨慧；

【作者基本信息】 东北大学 ， 采矿工程， 2021， 硕士

【摘要】 地下煤层气的开采、利用煤层封存二氧化碳以及预防瓦斯突出事故的发生,都与气体在煤层中吸附、解吸和扩散的特性有关。突出过程会对煤层产生破坏,也伴随着不同粒径煤粒的产生,研究气体在不同粒径煤粒中的运移规律,对了解煤粉突出过程具有重要意义。煤粒中包含有多个孔隙,这些孔隙的孔径、形状和连通度等不尽相同,又表现为煤粒孔隙度等参数的不同。煤粒尺寸改变会导致孔隙结构也发生变化。煤在不同温度、压力和地质条件作用下,变质程度发生改变,这也会影响煤的微观结构,煤粒尺寸和变质程度都会影响到气体在孔隙中的扩散能力。因此,本文进行了以下研究工作:(1)选取烟煤和无烟煤这两种变质程度的煤,并破碎为合适的粒径,针对这些煤样设计解吸扩散实验方案。(2)测量煤粒基本参数,在30℃、不同压力条件下下开展恒温实验,在30℃、1MPa吸附平衡条件下进行绝热实验,同时测量实验过程中温度的变化。在获得较为准确的实验数据基础上,研究不同变质程度条件下粒径对气体扩散规律的影响机理。(3)将煤的孔隙结构对气体扩散的影响用扩散因子这个参数来表示,用扩散因子修正随温度、压力变化的扩散系数,从微观方面建立考虑扩散因子的数学模型,研究不同变质程度下扩散因子、扩散系数随煤粒径变化的规律。(4)基于实验结果和数值模拟,分析不同条件下气体扩散系数随粒径的变化规律,并根据扩散因子模型,反演不同粒径下的扩散系数,与实验数据进行对比,验证模型的准确性,分析实验和模型中可能会存在的问题。更多还原

【Abstract】 The exploitation of underground coalbed methane,the use of coal seams to seal carbon dioxide and the prevention of gas outburst accidents are all related to the characteristics of gas adsorption,desorption and diffusion in coal seams.Outburst process will destroy the coal seam,and it is also accompanied by the generation of coal particles with different particle sizes.It is of great significance to study the migration law of gas in coal particles with different particle sizes for understanding the coal powder outburst process.There are many pores in coal particles,which are different in pore size,shape and connectivity,and also show different parameters such as porosity of coal particles.The change of coal particle size will lead to the change of pore structure.Under different temperature,pressure and geological conditions,the metamorphic degree of coal changes,which will also affect the microstructure of coal.The size and metamorphic degree of coal particles will affect the diffusion ability of gas in pores.Therefore,this paper has done the following research work:(1)Bituminous coal and anthracite coal are selected and crushed to suitable particle size,and the desorption and diffusion experiment scheme is designed for these coal samples.(2)Measure the basic parameters of coal particles,carry out constant temperature experiments at 30℃ and different pressures,and carry out adiabatic experiments at 30℃and 1 MPa adsorption equilibrium.meanwhile,measure the temperature changes during the experiments.On the basis of obtaining more accurate experimental data,the influence mechanism of particle size on gas diffusion law under different metamorphic conditions was studied.(3)The influence of coal pore structure on gas diffusion is expressed by diffusion factor,and the diffusion factor is used to modify the diffusion coefficient changing with temperature and pressure.The mathematical model considering diffusion factor is established from microscopic aspect,and the laws of diffusion factor and diffusion coefficient changing with coal particle size under different metamorphic degrees are studied.(4)Based on data processing and numerical simulation,analyze the variation law of gas diffusion coefficient with particle size under different conditions,and according to the diffusion factor model,invert the diffusion coefficient under different particle sizes,compare with the experimental data,verify the accuracy of the model,and analyze the possible problems in the experiment and model.更多还原