煤层气再燃降低分解炉NO_x排放特性的模拟研究

发布时间：2018-05-11 16:28

本文选题：煤层气再燃 + 分解炉　；参考：《湘潭大学》2017年硕士论文

【摘要】：改革开放近四十年来,长期的“粗放式”经济发展模式致使我国面临的能源与环境问题日益严峻,国家对大气污染物排放的整治力度也连年提高。面对愈加严格的水泥行业NO_x排放标准,开发高效、低成本的水泥生产脱硝技术已刻不容缓。为此,本文提出了煤层气再燃降低分解炉NO_x排放的低氮燃烧技术并对其展开数值模拟研究,旨在为水泥生产脱硝技术的开发与应用提供指导和参考。主要内容和结论如下:(1)以某厂TDF型分解炉为对象建立仿真计算模型,利用Fluent软件对运行工况下分解炉内速度场、温度场以及组分浓度分布特性进行模拟和分析,获得再燃改造依据,并通过现场实测验证模型的可靠性。(2)提出分解炉煤层气再燃改造方案,依次模拟分析主燃区长度、再燃区长度、再燃区过剩空气系数以及煤层气量对再燃效果的影响规律,结果表明:随着主燃区长度的增加,脱硝效率先升高后降低,而燃料燃尽率变化较小;随着再燃区长度的增加,脱硝效率逐渐上升,分解炉不完全燃烧热损失却逐渐加重;随着再燃区过剩空气系数的升高,脱硝效率先升高后降低,出炉生料分解率则逐渐提高;随着煤层气量的增多,脱硝效果逐渐变好,但分解炉燃烧效率却小幅降低。(3)通过正交法探究四个再燃因素同时变化对分解炉生料分解率及脱硝效率的影响,结果表明若要提高再燃脱硝效率,则须以牺牲出炉生料分解率为代价。综合平衡分析得到较优分解炉煤层气再燃改造方案为:煤层气喷入高度7 m、燃尽风喷入高度10.5 m、再燃区过剩空气系数α=0.75、煤层气发热量占比12.5%。(4)通过对比分析再燃工况与运行工况的模拟结果可知,再燃改造后:炉内速度场更利于气-粉混合和换热;主燃区温度有所降低,利于抑制燃料型NO的生成;分解炉出口烟气温度有所降低,表明分解炉热效率升高;燃料燃尽率为91.57%,仅下降1.06个百分点;出炉生料分解率为94.60%,提高2.94个百分点;分解炉出口NO浓度为378.15mg/Nm3,脱硝效率为49.27%,达到现行国家标准。煤层气再燃技术能够满足水泥生产脱硝需求。
[Abstract]:In the past forty years since the reform and opening up, the long-term "extensive" economic development model has made our country face increasingly serious energy and environmental problems, and the national regulation on the discharge of atmospheric pollutants has been improved year after year. In the face of more stringent NO_x emission standards in cement industry, it is urgent to develop high efficiency and low cost denitrification technology in cement production. In this paper, a low nitrogen combustion technology for reducing NO_x emission from calciner by coal bed methane reburning is proposed and numerical simulation is carried out in order to provide guidance and reference for the development and application of denitrification technology in cement production. The main contents and conclusions are as follows: (1) taking the TDF type calciner in a factory as the object, the simulation model is established. The velocity field, temperature field and component concentration distribution in the calciner under operating conditions are simulated and analyzed by Fluent software. The reburning reconstruction basis is obtained, and the reliability of the model is verified by field measurement. The scheme of reburning of calciner coal bed methane is put forward. The length of the main combustion zone and the reburning zone are simulated and analyzed in turn. The results show that the denitrification efficiency increases first and then decreases with the increase of the length of the main combustion zone, while the fuel burnout rate changes slightly, and with the increase of the length of the reburning zone, the effect of the excess air coefficient and the coal bed gas volume on the reburning efficiency increases. With the increase of excess air coefficient in the reburning area, the denitrification efficiency increases first and then decreases, and the decomposition rate of raw material increases gradually. With the increase of coal bed methane, the denitrification efficiency increases gradually, while the heat loss of the calciner increases gradually, and with the increase of excess air coefficient in the reburning zone, the denitrification efficiency increases first and then decreases. The effect of denitrification was improved gradually, but the combustion efficiency of calciner decreased slightly. 3) by orthogonal method, the effects of four factors of reburning on the decomposition rate and denitrification efficiency of raw meal of calciner were studied. The results showed that if the denitrification efficiency was to be increased, At the expense of the raw meal decomposition rate. Comprehensive equilibrium analysis shows that the optimal retrofit scheme of coal bed methane reburning in calciner is as follows: coal bed methane injection height is 7 m, burnout air injection height is 10.5 m, excess air coefficient 伪 = 0.75 in reburning zone, and the ratio of coal bed methane heat value to 12. 5%. The simulation results of the conditions and operating conditions show that, After reburning, the velocity field in the furnace is more favorable for gas-powder mixing and heat transfer, the temperature in the main combustion zone is lower, the formation of no is restrained, the flue gas temperature at the outlet of the calciner is decreased, which indicates that the thermal efficiency of the calciner is increased. The fuel burnout rate was 91.57 percent, which was only 1.06 percent lower; the decomposition rate of raw meal was 94.60 percent, which increased 2.94 percent; the no concentration at the outlet of calciner was 378.15 mg / Nm ~ 3, and the denitrification efficiency was 49.27 percent, which reached the current national standard. Coal bed methane reburning technology can meet the demand of denitrification in cement production.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ172.625;X781.5

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