基于Fluent软件模拟水泥分解炉内SNCR脱硝过程

发布时间：2018-05-19 05:10

本文选题：分解炉 + 模拟　；参考：《济南大学》2015年硕士论文

【摘要】：分解炉是水泥窑外预分解技术的核心设备之一,承担着煤粉燃烧、碳酸盐分解等多种复杂的化学反应。作为水泥工业烟气中主要污染物之一的NOx,会对环境造成严重的破坏。本文基于Fluent软件对某厂5000t/d水泥熟料生产线的DD型分解炉进行了数值模拟,得到了分解炉的流场信息及NOx的生成特性,并以尿素作为还原剂采用选择性非催化还原法(SNCR)对分解炉内NOx进行脱除。同时,优化设计了SNCR脱硝工作参数,以提高脱硝性能,获取更合理的脱硝工作参数,为水泥分解炉脱硝提供理论指导。本文的主要研究内容如下：(1)根据DD型分解炉实际尺寸,采用Gambit软件建立物理模型,利用布尔运算将分解炉分成若干形状规则的几何体,采用分块网格划分技术进行网格划分,获取较高质量的网格。(2)建立分解炉数学模型,采用标准k-ε模型模拟气相湍流流动,采用组分输运模型模拟煤粉燃烧及化学反应,采用P-I辐射模型模拟辐射换热,获得了分解炉内流场信息,模拟结果表明：流体运动速度沿分解炉中心轴线对称,多处出现涡旋现象；煤粉燃烧后产生大量的热量,分解炉内温度从主燃烧室至出口处呈抛物线形梯度递减,最高温度在煤粉燃烧器上侧,约为1800K,出口处温度约为1150K；煤粉燃烧后挥发份、O2、CO和CO2的浓度场分布符合燃烧基本规律,燃烧状况良好,分解炉配风比例恰当。(3)利用后处理的方法,采用污染物生成模型模拟了分解炉内NO的生成,获得了NO的分布规律,模拟结果表明：NO大量生成于主燃烧室内,是煤粉燃烧的结果,其生成浓度与煤粉用量相吻合,在流体的不断扩散下,最终均匀地弥漫在分解炉内,若只考虑分解炉内煤粉燃烧产生的燃料型NOx,出口处NO的浓度约为450ppm,综合考虑实际工况中窑尾烟气携带入炉的NO,分解炉出口处NO的浓度约为850ppm。(4)以尿素为还原剂,采用SNCR模型模拟了分解炉内SNCR脱硝过程,结果表明,尿素的喷入能降低烟气中NO的浓度。为提高脱硝效率,获取适合该模型的最佳脱硝工作参数,对尿素喷射参数进行了优化设计,结果表明,尿素喷射角度为分解炉Z轴方向水平向下60°、喷射速度为25m/s、喷射高度距分解炉入口26m时,脱除NO的能力最强；为获取较佳的脱硝效果和较低的NH3逃逸,尿素与NO的摩尔比不宜超过1.0,最佳范围在0.8～0.95之间。
[Abstract]:Calciner is one of the core equipments of precalciner technology in cement kiln. It undertakes a variety of complex chemical reactions such as pulverized coal combustion, carbonate decomposition and so on. As one of the main pollutants in the flue gas of cement industry, no x will cause serious damage to the environment. Based on Fluent software, the DD type calciner of 5000t/d cement clinker production line in a factory is numerically simulated in this paper. The flow field information of the calciner and the generation characteristics of NOx are obtained. The NOx in the calciner was removed by selective non-catalytic reduction with urea as reducing agent. At the same time, the working parameters of SNCR denitrification are optimized to improve denitrification performance, obtain more reasonable denitrification parameters and provide theoretical guidance for denitrification in cement calciner. The main contents of this paper are as follows: (1) according to the actual size of DD type calciner, the physical model is established by using Gambit software, and the calciner is divided into some regular geometric bodies by Boolean operation. The mathematical model of calciner is established. The standard k- 蔚 model is used to simulate the gas phase turbulent flow, the component transport model is used to simulate the combustion of pulverized coal and chemical reaction, and the P-I radiation model is used to simulate the radiation heat transfer. The flow field information in the calciner is obtained. The simulation results show that the velocity of the fluid moves symmetrically along the central axis of the calciner, and vortex phenomenon occurs in many places, and a large amount of heat is produced after the combustion of pulverized coal. The temperature in the calciner decreases from the main combustion chamber to the outlet with a parabolic gradient, the highest temperature is about 1800K on the top side of the pulverized coal burner, and the temperature at the outlet is about 1150k.The distribution of the concentration fields of CO and CO2 in the volatile matter of pulverized coal combustion accords with the basic combustion law. The combustion condition is good and the air distribution ratio of calciner is proper. 3) by using the method of post-treatment, the no generation in the calciner is simulated by using the pollutant generation model, and the distribution of no is obtained. The simulation results show that a large number of no is produced in the main combustion chamber. It is the result of pulverized coal combustion, and its formation concentration is consistent with the amount of pulverized coal. Under the continuous diffusion of the fluid, it eventually diffuses uniformly in the calciner. If only the fuel-type no produced by pulverized coal combustion in the calciner is considered, the concentration of no at the outlet is about 450 ppm.The concentration of no at the outlet of the calciner is about 850ppm.m4, and the concentration of no at the outlet of the calciner is about 850ppm.m.4) Urea is used as reductant. The process of SNCR denitrification in calciner was simulated by SNCR model. The results show that the injection of urea can reduce the concentration of no in flue gas. In order to improve the denitrification efficiency and obtain the best denitrification parameters suitable for the model, the optimum design of urea spray parameters was carried out. When the injection angle of urea is 60 掳horizontally down the Z axis of the calciner, the injection velocity is 25m / s, and the injection height is 26m from the inlet of the calciner, the ability of no removal is strongest, in order to obtain better denitrification effect and lower NH3 escape, The molar ratio of urea to no should not exceed 1.0, and the optimum range is between 0.8 and 0.95.
【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X781.5;TQ172.6

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