【作者】 邓浩鑫；

【导师】 肖云汉；

【作者基本信息】 中国科学院研究生院（工程热物理研究所） ， 工程热物理， 2014， 博士

【摘要】 甲烷是一种重要的温室气体来源,其排放量仅次于二氧化碳,温室效应是二氧化碳的二十多倍。有效的处理和利用煤矿通风甲烷,具有温室气体减排和节约能源的重要意义。目前通风瓦斯处理技术应用最广的是采用蓄热氧化的方式实现低浓度甲烷的氧化处理。通风瓦斯蓄热氧化过程的参数影响分析是这一技术走向应用的基础。然而,实验规模和散热等约束条件使得参数影响的研究范围受到限制,实验分析的结果也不具有普遍的适用性。同时,面对通风瓦斯蓄热氧化装置的设计需求,实验和数值模拟研究难以满足快速的工程设计需要,也难预测设计参数变化带来的装置稳定运行范围变化问题。针对以上两方面的问题,本文对煤矿通风瓦斯蓄热氧化过程开展了实验、数值模拟和理论分析的研究,具体研究内容和结果如下：1.针对通风瓦斯蓄热氧化过程的参数影响问题开展了无量纲化的实验参数分析研究。建立了通风瓦斯蓄热式热氧化实验系统以及低浓度甲烷氧化固定床反应器,同时建立了实验装置中蓄热式换热过程的无量纲分析模型。提出低浓度甲烷在氧化装置中氧化的基本条件,结合蓄热式换热过程的无量纲计算结果对实验中各个参数的影响进行了分析,结果表明和无量纲时间相关的切换时间对装置的影响较小,而与无量纲长度相关的气流速度对装置内温度分布的影响较大。2.开展了通风瓦斯蓄热式热氧化装置的一维模型化研究。建立了通风瓦斯蓄热氧化装置的一维计算模型。利用开源的Matmol程序,基于线法对通风瓦斯蓄热氧化装置的运行过程进行了模拟计算,模拟结果和实验符合较好。计算结果表明,氧化装置的蓄热条件涉及气流流速、甲烷浓度、蓄热体结构等诸多因素,是装置能否稳定运行的关键。流速的影响存在有多重影响的机制,这一多重影响机制会使得通风瓦斯蓄热氧化装置在实际运行中既有通风量的下限也有通风量的上限。3.开展了通风瓦斯蓄热式热氧化装置的三维建模研究。基于多孔介质的连续分布假设,利用Fluent软件的自定义标量方程等功能模块建立了通风瓦斯蓄热氧化过程的三维计算模型,利用这一计算模型研究了通风瓦斯蓄热氧化装置中流动分布、温度分布等问题。计算结果表明,蜂窝蓄热体区域的整流作用,使得工业装置设计中两端入口的结构对装置内流动分布的影响很小。散热会影响装置内的温度分布甲烷转化率,实验结构下的空腔有较小的气流混合作用。由于气流的滞留效应,装置切换时间缩短会降低装置的综合甲烷转化率,根据无量纲切换时间的计算,可以选择装置切换时间为60s-120s。4.针对目前通风瓦斯蓄热氧化装置的设计需求,开展了基于蓄热式换热过程的蓄热氧化装置设计方法研究。提出一种蓄热氧化装置内最低稳定运行甲烷浓度的计算方法,并与部分实验结果进行了比较验证,计算模型的预测结果与实验符合较好。基于这一方法进一步计算了装置内通风量范围、蓄热体的需求量等参数。计算结果表明装置存在主要由散热决定的通风量下限以及由蓄热性能决定的通风量上限。烟气分流计算结果和稳定运行试验运行结果表明,本文提出的设计方法可以用于工业装置的设计。更多还原

【Abstract】 Methane is an important source of greenhouse gas, as it is the second leading greenhouse gas, next to CO2, in contribution to global warming. The global warming potential(GWP) of methane is20times of CO2on the condition of the same mass. The methane emission of coal mining industry accounts for22%of the whole energy industry. About30billion m3methane are discharged from the worldwide coal mining process, while the amount of20billion m3are generated by China. Among this emission, more than70%comes from ventilation air methane(VAM). An effective treatment and utilization of ventilation air methane have an important meaning for greenhouse gas reduction and energy saving. The oxidation process of methane can realize the reduction of greenhouse gas. As the concentration of methane in ventilation air methane are far lower than the combustion limit, the oxidation process is hard to achiever in conventional condition. The most prospective technology applied to the treatment of ventilation air methane is thermal flow-reversal reactor(TFRR). This paper established a TFRR experimental device and a dynamic TFRR simulation model to show the parameter influence, and then a TFRR design model was put forward and had been verified by experiments:1. Parameter analysis of thermal flow-reversal reactorExperimental system of the regenerative thermal oxidation for ventilation air methane and the fixed bed reactor of lean methane-air mixture oxidation were established. The fundamental condition of the lean methane-air mixture oxidation process is proposed. The effect factors on the regenerative thermal oxidation process of ventilation air methane were analyzed with the help of dimensionless analysis.2. One dimensional model of regenerative thermal oxidation of VAMAn one-dimensional model was proposed for the regenerative thermal oxidation of VAM, and it was employed to simulate the working conditions, and compared with the experiment. The governing equations were solved by the method of lines using an open source software(MatMOL) based MATLAB language. Results show that the regenerative heat exchange conditions involving feed gas velocity, periodic switch time, structure of honeycomb ceramics are critical for stable operation of the reactor. The feed gas velocity has multiple influence on the steady of the reactor because of the relatively fixed heat loss of the reactor.3. Three dimensional model of regenerative thermal oxidation of VAMA heterogeneous three dimensional continuum model of the reactor was established using the user defined scalar in the commercial software Fluent. Flow distribution, temperature profile and concentration profile of the reactor were studied. The calculation results show that the rectifying effect of the honeycomb ceramic zone is very obvious. Heat loss of the reactor will affact the methane conversion, and improvement of central cavity on the methane conversion was very limited. The switch time should be properly prolonged due to the gas-trap effect.4. Design method of thermal flow-reversal reactor for VAMA method of calculating the stable operating parameters of thermal flow-reversal reactor was proposed. The regenerative heat exchange model and the criterion of the stability were established in thermal flow-reversal reactor. Based on the solution of the established model, the lowest self-sustaining methane concentration of the reactor was calculated. The calculated results are basically consistent with the experimental results, which shows the validity of the proposed model. The ventilation rate ranges of the reactor’s stable operation, the flow rates of the withdrawal gas, the self-sustaining honeycomb ceramic demands are also calculated using this model.更多还原