双室型煤矿乏风预热催化氧化装置试验及模拟研究

发布时间：2018-03-14 19:29

  本文选题：双室型乏风预热催化氧化　切入点：导流分配　出处：《山东理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：煤矿乏风瓦斯中蕴含着巨大的潜在能源,但由于其甲烷浓度极低的特点,通常难以利用而被直接排空。据统计,目前我国每年通过煤矿向大气中排放的瓦斯已经超过250亿m3,造成了严重的环境污染和能源浪费,由此可见实现煤矿乏风瓦斯的有效利用具有非常重大的现实意义。本文基于此现状,设计搭建了双室型煤矿乏风预热催化氧化试验装置,对其结构原理、系统组成及操作过程进行了详细介绍,并基于试验装置进行了一系列模拟及试验研究。利用数值模拟的方法对氧化床入口的导流分配系统进行了设计,通过加装导流板、优化结构参数改善了氧化床入口的流动均匀性。结果表明,当导流板的圆角半径为140mm、数量为3块、相对距离在0.3~0.4之间时导流效果较好,最优方案的流动不均匀性系数降至0.2以下。通过加热启动实验对氧化床的稳定性进行了研究,结果表明:反应室良好的对称性为氧化床的稳定运行提供了条件;陶瓷散热损失的存在使氧化床轴向温度呈现逐渐降低的状态,温度高于700℃时散热量较大;加热启动初期热漂移现象较明显,温度不均匀系数较高,系统稳定后温度不均匀系数低于0.05;升温工况比降温工况的稳定时间短,保持升温工况更容易实现氧化床的稳定。在保持电加热开启的状态下实验研究了空速、氧化床入口温度和甲烷浓度对氧化过程的影响,结果表明:甲烷的催化氧化主要集中在第一层催化陶瓷中,空速的增大使主要反应区域增大,空速由3800 h-1增至7100 h-1时,有效反应长度增加了约31%,空速大于7100 h-1时,有效反应长度增大的速率加快,转化率略有下降;氧化床入口温度的升高使主要反应区域减小,温度由422℃升高至485℃时,有效反应长度减小了约53%,转化率上升,温度高于485℃后影响的作用逐渐减弱;甲烷浓度的增加对氧化过程的影响较小,有效反应长度略有减小,转化率略有上升。通过总结实验数据,得到了有效反应长度的经验公式。对装置自维持运行状态下的热平衡进行了研究,计算分析了不同甲烷浓度和空速下的热平衡情况,结果表明:甲烷浓度越高时,系统的富余热量越多,散热损失所占的比重越大,浓度高于1.05%时,高于排气损失占据主导地位;空速越大时,实现自维持所需的浓度越高,系统的排气损失占得比重越大,空速大于7000 h-1时,高于散热损失开始占据主导地位。因此应针对高甲烷浓度工况着重控制散热损失,针对高空速况着重控制排气损失,对预热器和保温层进行合理设计,以增大能量的富余、提高余热资源的利用率。
[Abstract]:Coal mine exhaust gas contains huge potential energy, but because of its extremely low methane concentration, it is usually difficult to use and is directly emptied. At present, China has discharged more than 25 billion m3 of gas into the atmosphere each year through coal mines, which has caused serious environmental pollution and energy waste. Therefore, it is of great practical significance to realize the effective utilization of the exhausted air gas in coal mine. Based on the present situation, this paper designs and builds a two-chamber test device for catalytic oxidation of coal mine exhaust air preheating, and gives the structure principle of the device. The composition and operation process of the system are introduced in detail, and a series of simulation and experimental research are carried out based on the test device. The flow diversion distribution system at the entrance of the oxidation bed is designed by numerical simulation, and the flow guide plate is added to the system. The flow uniformity at the inlet of the oxidation bed is improved by optimizing the structural parameters. The results show that when the radius of the guide plate is 140 mm, the number of the plate is 3, the relative distance is between 0.3 and 0.4, the flow diversion effect is better. The flow inhomogeneity coefficient of the optimal scheme is reduced to less than 0.2. The stability of the oxidation bed is studied by heating start-up experiment. The results show that the good symmetry of the reaction chamber provides the conditions for the stable operation of the oxidation bed. Due to the existence of ceramic heat loss, the axial temperature of the oxidation bed decreases gradually, and when the temperature is higher than 700 鈩，

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