煤矿乏风催化氧化固碳的理论及实验研究

发布时间：2018-05-23 23:24

本文选题：煤矿乏气 + 蜂窝陶瓷　；参考：《华中科技大学》2015年硕士论文

【摘要】：煤矿开采过程中矿井乏风的排放给环境带来了严重的污染,加剧了温室效应。煤矿乏风有气流量大,气体中甲烷浓度很低,流量不稳定等特点,这些特点限制了其在工业上的应用,目前常采用直接氧化的手段进行处理,并未对煤矿乏风进行利用,是能源的极大浪费。由此,针对煤矿乏风,开发一种新型技术,使之能够应用于生产实践,对环境保护与能源的可持续发展有重要意义。本文首先介绍了煤矿乏风排放现状,综述了国内外在实验研究方面所开展的各项工作,介绍了乏风甲烷作为主要燃料的典型技术:热逆流氧化技术、热逆流催化氧化技术以及整体式催化氧化技术,分析比较三种技术的优势及其不足。在分析的基础上,选用整体式催化氧化技术,设计新型燃烧系统,通过催化剂的选用及固碳段的布置,试验对煤矿乏风的减排作用。基于CHEMKIN软件,对煤矿乏风甲烷在蜂窝陶瓷内的催化氧化过程进行模拟计算,对比有无催化剂甲烷转化率的变化,分析预热温度、进气浓度、气流速度、催化剂比表面积以及催化剂孔道密度对氧化过程的影响规律。结果表明,催化剂可以有效降低煤矿乏风甲烷完全转化所需温度;甲烷浓度提高有利于反应区域前移,同时受气流速度影响变小,燃烧更稳定;操作条件不变,催化剂比表面积增加与催化剂孔道密度提高,有助于甲烷转化率升高。采用溶胶凝胶法和浸渍法制备了Pd/Al2O3整体式催化剂和LaMnO3/MgO整体式催化剂,运用XRD、SEM等方法对催化剂进行了表征,对催化剂催化活性及热稳定性进行评价。结果表明,对CH4浓度为0.5%的煤矿乏风,Pd/Al2O3整体式催化剂具有更好的低温起燃活性;催化剂800°C焙烧24h,LaMn O3/MgO整体式催化剂甲烷转化率达97.12%,具有更好的热稳定性。煤矿乏风分级氧化,第一级设置为Pd/Al2O3整体式催化剂,第二级设置为LaMnO3/MgO整体式催化剂,可以有效降低起燃点,促进反应发生,保证高温段的热稳定性。尾部设置固碳段,预热温度为500°C,CH4浓度为1%时,尾气中CO2浓度低于0.2%,实现温室气体的近零排放。设计煤矿乏风催化氧化供热系统,分析了各设备反应温度的变化及各过程对温度的需求,通过对余热进行利用,提高经济效益,避免能源浪费。分析碳减排收益与热利用收益的经济性,系统静态投资回收期短且投资回报率很高,具有广阔的市场前景。
[Abstract]:In the process of coal mining, the exhaust of mine air brings serious pollution to the environment and intensifies Greenhouse Effect. The characteristics of low air flow rate, low methane concentration and unstable flow in coal mine restrict its application in industry. At present, direct oxidation is often used to treat coal mine exhaust air. Is a great waste of energy. Therefore, it is of great significance for environmental protection and sustainable development of energy resources to develop a new type of technology to be used in production practice in the light of lack of wind in coal mines. In this paper, the current situation of exhaust air emission from coal mines is introduced, and the research work in the field of experiment is summarized. The typical technology of the spent wind methane as the main fuel is introduced, which is heat countercurrent oxidation technology. The advantages and disadvantages of thermal countercurrent catalytic oxidation and integral catalytic oxidation are analyzed and compared. On the basis of analysis, a new combustion system was designed by using integral catalytic oxidation technology. Through the selection of catalyst and the arrangement of carbon sequestration section, the emission reduction effect of coal mine spent wind was tested. Based on CHEMKIN software, the catalytic oxidation process of coal mine exhaust methane in honeycomb ceramics was simulated and calculated. The methane conversion rate was compared with or without catalyst, and the preheating temperature, inlet air concentration and air velocity were analyzed. The effect of specific surface area and pore density of catalyst on the oxidation process. The results show that the catalyst can effectively reduce the temperature required for the complete transformation of methane from coal mine, and the increase of methane concentration is beneficial to the forward movement of the reaction zone, and the combustion is more stable because of the influence of the airflow velocity, and the operating conditions are not changed. The increase of specific surface area of catalyst and the increase of pore density of catalyst contribute to the increase of methane conversion. Pd/Al2O3 monolithic catalyst and LaMnO3/MgO monolithic catalyst were prepared by sol-gel method and impregnation method. The catalytic activity and thermal stability of the catalyst were evaluated. The results show that the monolithic catalyst with 0.5% CH4 concentration has better ignition activity at low temperature, and the methane conversion rate of LaMn O3/MgO monolithic catalyst calcined at 800 掳C for 24 h is 97.12 and has better thermal stability. The first stage is Pd/Al2O3 monolithic catalyst, the second stage is LaMnO3/MgO monolithic catalyst, which can effectively reduce the ignition point, promote the reaction and ensure the thermal stability of the high temperature section. When the carbon sequestration section is set in the tail and the preheating temperature is 500 掳C ~ (-1), the concentration of CO2 in the tail gas is lower than 0.2, and the emission of greenhouse gas is near zero. The heating system of coal mine is designed by catalytic oxidation of spent wind, and the change of reaction temperature of each equipment and the demand of temperature in each process are analyzed. Through the utilization of waste heat, the economic benefit is improved and energy waste is avoided. By analyzing the economic benefits of carbon emission reduction and thermal utilization, it is found that the return period of system static investment is short and the return on investment is very high, so it has a broad market prospect.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD712;O643.32

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