改进型(SNCR+SCR)混合脱硝工艺气液多组分混合特性的数值模拟  被引量:9

Simulation Study of Multicomponent Mixing Characteristics Between Flue Gas and Droplet for Improved (SNCR+SCR) DeNO_x Technology

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作  者:周英贵[1] 金宝昇[1] 

机构地区:[1]东南大学能源与环境学院,南京210096

出  处:《燃烧科学与技术》2012年第4期359-366,共8页Journal of Combustion Science and Technology

基  金:国家自然科学基金资助项目(51076029)

摘  要:提出了改进型(SNCR+SCR)混合法脱硝工艺,建立了省煤器出口烟道NH3逃逸的摩尔分数分布模型和SCR入口烟道流场均流导流组件模块装置,基于Fluent平台,对大型燃煤锅炉改进型(SNCR+SCR)混合脱硝工艺在锅炉转向角处还原剂液滴与烟气的混合过程进行数值模拟,并进一步掌握SNCR后段烟气流场的氨氮混合特性和分布特性,同时考虑了混合过程与复杂温度场的相互作用,并探讨了其对SCR反应段的脱硝效果影响.计算结果表明,在喷枪位置固定条件下,传统SNCR反应区脱硝效率在尿素溶液喷射初期随喷射量增加而增大,但不是线性关系,当氨氮物质的量之比大于1.15后,增长减缓,且氨逃逸量与增加的尿素溶液量也非线性关系,改进型工艺在转向角补充尿素溶液喷射后,省煤器出口NH3摩尔分数与补充尿素溶液流量呈线性关系,大大降低了尿素耗量,新型均流导流组件解决了SCR反应器入口界面的回流、二次流以及入射角过大问题,优化后催化剂入口界面烟气速度标准偏差小于10%,浓度场偏差小于5%,在(SNCR+SCR)脱硝总效率70%条件下,综合考虑漏氨,氨氮物质的量之比可控制在1.5以下.最后通过应用该模型计算实际燃煤机组电厂运行反馈信息来验证数学模型的正确性和可靠性.This paper proposes a model of NH3 concentration distribution at the outlet of boiler economizer and a new uniform flow component module for the second generation (SNCR + SCR) hybrid de-nitrification technique. Numerical study on the mixing process between urea-water-solution droplet and flue gas in the steering room of the second generation (SNCR + SCR) system of a large scale coal-fired boiler was conducted based on Fluent platform, the effect of the mixing and distribution characteristics behind the SNCR reaction region was studied, and meanwhile the correlations of mixing process and complex temperature field were discussed. The simulation shows that SNCR de- nitrification efficiency and NH3 leakage are not in a linear relationship with urea-water-solution emitted-dose, which will significantly decrease de-nitrification efficiency when the molar ratio of NH3 to NO is greater than 1.15. The second generation (SNCR + SCR) system greatly reduces the consumption of urea-water-solution as a result ofpostinjection of urea in the steering room of boiler. The new uniform flow component module solves the problems of vortex and secondary flow and improves the uniformity of molar ratio of NH3 to NO. The flue gas velocity deviation is less than 10% and the concentration field deviation is less than 5% at the first catalyst layer inlet. However, considering NH3 leakage in the SCR outlet, molar ratio of NH3 to NO should be controlled bellow 1.5 when the general (SNCR+SCR) denitrfication efficiency is 70%. Finally, the correctness and reliability of the CFD mode are verified by feedback information from power station.

关 键 词:第二代 SNCR+SCR 混合 导流均流组件 氨氮物质的量之比 氨逃逸 液滴 

分 类 号:X511[环境科学与工程—环境工程]

 

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