瓦斯发电尾气注入采空区防灾与封存一体化基础研究

Gas power generation is the effective way to solve the problem of promoting gas extraction and energy saving and emission reduction. Gas power generation exhaust contains carbon dioxide, nitrogen oxides, etc., and direct exhaust emissions from gas power plant will lead to the greenhouse effect. But the exhaust contains more than 85% N2, and it’s a good kind of fire prevention materials which costs almost zero. By using the theoretical calculation, such as chemistry, material science, and so on, and the experimental method, competition mechanism between coal, rock mass is researched from micro to macro in the project. The adsorption and storage mechanism of coal and rock on harmful gases and effection of exhaust injection on coal spontaneous combustion prosess are revealed. Through the method of numerical simulation and similarity simulation experiment, three-dimensional gas flow adsorption diffusion numerical model in goaf, multi-field coupling solution model and similarity simulation test bench stand are set up. Diffusion migration regularity of the exhaust in the goaf is studied. The influence of the exhaust injection on the concentration of main gas components in the goaf and the temperature of the residual coal is determined. And disaster prevention and displacement gas mechanism that the exhaust injected into the goaf is revealed. The research results provide theoretical support for the development of the integration new technologies about harmful gas storage, gas displacement and energy saving and emission reduction.

瓦斯发电是解决促进瓦斯抽采、节能减排的最有效途径。瓦斯发电尾气中含有二氧化碳、氮氧化物等，直接排放会污染空气并造成温室效应，但尾气中氮气的含量在85%以上，是一种很好的防灭火材料且成本近似为零。本项目利用化学、材料学等理论计算和实验的方法，从微观、宏观的角度研究尾气在煤、岩体中的竞争吸附机制，揭示煤、岩对有害气体的吸附封存机理，并确定尾气注入对煤自燃过程的影响；应用数值模拟和相似模拟实验的方法，建立三维采空区气体流动吸附扩散数值模型和多场耦合解算模型，构建相似模拟试验台，研究尾气在采空区内的扩散运移规律，确定尾气注入对采空区内主要气体成分浓度与遗煤温度的影响，揭示尾气注入采空区防灾与驱替瓦斯机理。研究成果为有害气体封存、瓦斯驱替与节能减排一体化新技术的开发提供理论支撑。

瓦斯发电尾气直接排放会影响空气质量造成温室效应。尾气中含有85%的氮气，其余为二氧化碳、氮氧化物等，是一种很好的防灭火材料且成本近似为零。本项目研究为揭示尾气注入采空区实现对有害气体的封存及开发矿井防灾新技术提供理论支撑。.根据分子模拟研究单组份气体在煤中吸附和多元混合气体吸附。根据二元气体的吸附选择性可得出竞争吸附能力CO2>CH4>O2>N2，且高压和高含量不利于吸附能力强的气体的竞争。得到CO2的吸附位最强，CH4、N2和O2的优先吸附位依次减弱，且CO2会竞争CH4、N2、O2的吸附位。电厂烟气以16.5% CO2+79% N2+4.5%O2的比例在煤中吸附，吸附量CO2>N2>O2，有利于CO2的封存和抑制O2的吸附。煤吸附多个NO2分子的过程吸附能是正值，为吸热过程。且随着吸附量的增加，吸附能逐渐增大。.根据常温常压条件下实验研究，得到煤样对NO2、CO2、N2的吸附为物理吸附，注入电厂烟气后，每吨无烟煤、烟煤、褐煤封存电厂烟气中的CO2约0.9917m3、0.9739m3 和0.9553m3，可封存NO2约0.04989m3、0.05379m3和0.05278m3。NO2的吸附时间最短。煤在混合气体条件下吸附量大于在单组分气体吸附量，但小于单组份气体吸附量之和。NO2、N2、O2的存在影响了煤样对CO2的吸附量，使得CO2的饱和吸附量降低。.电厂烟气与CH4的竞争吸附时，注入的烟气量越多，CO2、N2和O2的吸附量越大，CH4的吸附量越小。CO2/N2/O2/CH4四元气体竞争吸附时，CO2与煤的相互作用最强，优先吸附位强于CH4且与CH4竞争吸附位，N2和O2与CH4竞争孔隙空间。因此注入电厂烟气可以置换出CH4封存CO2，从而隔绝与O2的接触，且烟气含量越大，系统的相互作用能越强，系统越稳定，越不易与O2吸附发生自燃。.建立数值模型研究采空区内气体运移规律，尾气注入采空区内氧浓度场、温度场以及组分浓度场的耦合变化规律。得到在采空区的迎风面存在稀释和置换效应的平衡点，注入的烟气可以最小化烟气含氧量波动对温度场的干扰。这种定向惰化比注氮更有利于抑制遗煤氧化。并能够封存二氧化碳和氮氧化物，为解决尾气注入矿井采空区防灾封存的关键科学技术问题具有重要的理论和实际意义。