变负压环境下颗粒煤瓦斯解吸动力学特性研究

Gas content in coal seams is a basic parameter of coal mine gas disaster control and coalbed methane calculation of reserves. There are three main limitations for measuring gas content by sampling in coal seam accurately: precise location, lost gas content extrapolation and time consumption. Although the sampling equipment in negative-pressure environment formed by the pressed air ejector can complete accurate location and short-time sampling, due to the less-understood dynamics of gas desorption under the negative pressure conditions, the normal pressure gas desorption law is still applied instead of the negative pressure when extrapolating gas loss. In order to solve the problem of compensating gas loss during sampling under negative pressures, the project is going to conduct simulations to study the desorption process of granular coal under constant and varying negative pressures by self-developed negative-pressure desorption simulation equipment. The approaches combine theoretical analysis and experiments. The gas adsorption-desorption kinetics theory and flow theory, gas desorption characteristics are to be studied under varying negative pressures. Then the gas desorption model of granular coal and method of compensating gas loss during sampling are to be built under varying negative pressures. And both models will be verified by experiments. The studies in the project will provide theoriees for measuring gas content in certain locations quickly and accurately.

煤层瓦斯含量是煤矿瓦斯灾害治理、煤层气储量计算的基础参数。难以实现定点取样、取样过程中瓦斯损失量推算不合理和取样时间过长是制约煤层瓦斯含量准确测定的主要因素。利用压风引射原理形成的负压能够实现定点取样，且取样时间较短，因有关负压条件下瓦斯解吸动力学特性研究还不够深入，取样过程中损失瓦斯量依旧采用常压环境下获得的瓦斯解吸规律进行推算。为了解决负压取样过程中损失瓦斯量补偿的问题，项目拟运用理论分析和实验室实验相结合的方法，利用自行研制的负压解吸模拟装置对恒定负压环境中及负压变化过程中颗粒煤瓦斯解吸过程进行模拟测试，结合瓦斯吸附解吸动力学理论和空气流动理论，研究负压变化过程中颗粒煤瓦斯解吸动力学特性，构建负压变化过程中颗粒煤瓦斯解吸模型和负压取样过程中损失瓦斯量推算方法，并在实验室进行验证。本项目的研究，将为实现定点、快速、准确测定煤层瓦斯含量提供理论支撑。

煤层瓦斯含量是评价和预测瓦斯储量与瓦斯涌出量的基础数据，是区域预测的主要指标，煤层瓦斯含量的准确测定与煤矿的安全生产息息相关。定点快速的取样以及取样过程中的瓦斯损失量推算是煤层瓦斯含量准确测定的关键技术，负压取样可以实现较长钻孔快速定点的取样，其特点是煤样在负压的作用下迅速从孔底取出。但是该方法在推算取样过程中损失瓦斯量时，依旧采用常压环境下颗粒煤瓦斯解吸规律获得的经验公式，其合理性值得商榷。.为了获得负压取样过程中煤的瓦斯解吸规律，准确推算负压取样过程中的瓦斯损失量，搭建了一套负压稳定、可调，具有解吸数据自动采集功能的瓦斯解吸规律模拟测试装置。利用该装置对吸附平衡压力为0.5MPa、1.0MPa、1.5MPa、2.5MPa的无烟煤煤样，在负压分别为10kPa、20kPa、30kPa、40kPa的条件下进行瓦斯解吸模拟测试，结果表明：相同吸附平衡压力条件下，负压越大，相同时间段内煤的瓦斯解吸量和解吸速度越大，负压对煤的瓦斯解吸具有明显的促进作用。负压对试验初始20min内的瓦斯解吸速度影响较大，至20min时，瓦斯解吸速度最大衰减超过90%，超过20min后，负压对瓦斯解吸速度的影响较小。取样负压由0kPa变至40kPa时，解吸量比常压下解吸量增大了7.76%，取样负压由40kPa变至0kPa时，解吸量比常压下解吸量增大了11.40%，环境负压由高到低时解吸量比常压下解吸量增幅大。.对负压取样阶段（前3min）及模拟实验全过程（360min）进行回归分析得出七类公式用来描述负压取样过程中煤的瓦斯解吸规律的合理的。负压取样条件下， 采用巴雷尔法推算的瓦斯损失量存在较大的误差，随着取样负压的增大，推算的瓦斯损失量误差逐渐增大；根据解吸数据，构建了负压取样过程中损失瓦斯量推算方法。