洁净煤技术

2020, v.26;No.130(06) 175-181

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活性焦脱硫脱硝反应器模拟及内构件优化
Simulation and internal component optimization of active coke desulfurization and denitrification reactor

张云雷;梁大明;孙仲超;熊银伍;
ZHANG Yunlei;LIANG Daming;SUN Zhongchao;XIONG Yinwu;Coal Chemistry Branch of China Coal Research Institute;Beijing Key Laboratory of Coal Based Carbon Materials;State Key Laboratory of Coal Mining and Clean Utilization;

摘要(Abstract):

随着环保政策的收紧,烟气排放要求日趋严格,工业废气污染物脱除形势严峻。活性焦烟气净化工艺与传统烟气净化工艺相比具有节水节能、无二次污染的技术特点。作为工艺的核心,反应器的研究已经成为了制约该项技术发展的关键。以某工程活性焦联合脱硫脱硝反应器为研究对象,建立了数值分析模型,对比了不同工况条件下模型压降与现场装置压降值,二者平均偏差5.9%,模型能够在一定程度上反映装置实际运行情况。在此基础上利用CFD软件对反应器内部流场以及关键组分浓度场进行了模拟分析。根据模拟结果,反应器进气室内烟气流动紊乱,出现了涡流以及空腔现象,进而导致烟气在活性焦层中停留时间出现差异;由喷氨区氨气质量分数分布云图可知,氨气分布不均匀,对系统污染物脱除效率造成负面影响。针对以上问题,采取在反应器内添加内构件的方式来提高系统污染物脱除效率。为提高反应器入口烟气的均布性,在反应器烟气入口位置设置导流板并对比分析了3种不同形式导流板的优化效果,结果表明烟气入口加装等距阶梯型弯曲导流板时,烟气均布效果最好,系统内气流均布性较未添加导流板前提高了11%,压降降低了267 Pa;由于活性焦烟气脱硝所采用的方法为氨选择性催化还原法,脱硝过程中需要喷入氨气作为还原剂,在喷氨量一定条件下,氨气在反应器脱硝区浓度分布是否均匀直接影响系统最终的脱硝效率。为了提高氨气浓度分布均匀性,在原有喷氨格栅的基础上添加多孔板,利用多孔板对氨气的分流及均布作用,达到短距离内氨气与烟气混合的目的。加装多孔板与传统的缩小喷氨孔孔径、增加喷氨管数的方式相比,降低了装置运行过程中格栅堵管的风险,提高了装置运行稳定性。模拟结果显示喷氨格栅上方加装多孔板使装置喷氨均匀性提高了21%。经优化后,系统污染物脱除效率达到了85%以上,满足污染物排放要求且系统运行稳定性提高,堵灰堵管风险降低。模拟结果和现场实操数据相关性较好,表明模拟结果可靠性较高,对实际生产有一定借鉴意义。
With the tightening of environmental protection policies,the requirements for flue gas emissions are becoming more and more strict,and the removal of industrial exhaust pollutants faces a serious situation.Compared with the traditional flue gas purification process,the activated coke flue gas purification process has the technical characteristics of water saving,energy saving and no secondary pollution.As the core of the process,the research of the reactor has become the key to restrict the development of this technology.Taking the active desulfurization and denitration reactor of a certain project as the research object,a numerical analysis model was established and the pressure drop values between the model and the field device under different working conditions were compared.The average deviation between the two is 5.9%.The model can reflect the actual operation of the device to a certain extent.On this basis,CFD software was used to simulate and analyze the flow field inside the reactor and the concentration field of key components. According to the simulation results,the flue gas flow in the inlet chamber of the reactor is turbulent,and eddy currents and cavities appear,which leads to a difference in the residence time of flue gas in the active coke layer.In addition,according to the distribution map of ammonia mass fraction in the ammonia injection area,it can be seen that the uneven distribution of ammonia gas has a negative impact on the removal efficiency of system pollutants.In view of the above problems,the method of adding internal components in the reactor is adopted to improve the removal efficiency of the system pollutants.In order to improve the uniformity of flue gas at the inlet of the reactor,a deflector was installed at the flue gas inlet of the reactor and the optimization effects of three different types of deflector were compared and analyzed.The results show that the equidistant stepped curved deflector is installed at the flue gas inlet,the effect of uniform distribution of flue gas is the best.The uniformity of air flow in the system is increased by 11% and the pressure drop is reduced by 267 Pa compared with that before adding deflector.As the ammonia selective catalytic reduction method is adopted for flue gas denitrification of activated coke,ammonia gas needs to be injected as a reducing agent during the denitration process.Under a certain amount of ammonia injection,whether the ammonia gas concentration distribution in the denitration zone of the reactor is uniform directly affects the final denitration efficiency of the system.In order to improve the uniformity of ammonia concentration distribution,a porous plate is added on the basis of the original ammonia spray grid,and the porous plate is used to split and distribute the ammonia gas to achieve the purpose of mixing ammonia gas and flue gas in a short distance.Compared with the traditional method of reducing the diameter of the ammonia injection hole and increasing the number of ammonia injection tubes,the installation of perforated plate can reduce the risk of grid blockage during operation of the device and improve the stability of the device.The simulation results show that addition of porous plates above the ammonia spray grid improves the uniformity of ammonia spray by 21%.After optimization,the system's pollutant removal efficiency has reached more than 85%,meeting pollutant discharge requirements and improving system's operating stability,reducing risk of ash and pipe plugging. The correlation between simulation results and actual field operation data is good,indicating that simulation results are highly reliable and have some reference significance for actual production.

关键词(KeyWords): 活性焦;脱硫脱硝;反应器;数值模拟;导流板;喷氨格栅
actived coke;desulfurization and denitrification;reactor;numerical simulation;guide plate;spraying ammonia grille

Abstract:

Keywords:

基金项目(Foundation): 国家重点研发计划资助项目(2016YFC0204100)

作者(Author): 张云雷;梁大明;孙仲超;熊银伍;
ZHANG Yunlei;LIANG Daming;SUN Zhongchao;XIONG Yinwu;Coal Chemistry Branch of China Coal Research Institute;Beijing Key Laboratory of Coal Based Carbon Materials;State Key Laboratory of Coal Mining and Clean Utilization;

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DOI: 10.13226/j.issn.1006-6772.19070301

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