大型链条炉SNCR脱硝试验及数值模拟

发布时间：2018-05-22 11:03

本文选题：链条炉 + 脱硝　；参考：《中国计量学院》2015年硕士论文

【摘要】：针对我国氮氧化物(NOx)排放现状及各种脱硝技术的比较分析,提出工业链条炉可应用选择性非催化还原(SNCR)技术进行低氮改造的方案。本文对某35t/h链条炉的热态燃烧及SNCR的脱硝特性开展了数值模拟与试验研究。首先,进行了链条炉燃烧数值计算,获取了流场、温度场、气相组分场等结果。以此为基础,考察了锅炉负荷与给煤停留时间变化对计算结果的影响,并分析了床层燃煤温度与质量的变化,随后统计了链条炉的燃尽率。结果表明:高负荷时,CO与O2的浓度降低,CO2浓度和烟气温度升高;给煤停留时间较短时,出口烟温降低,氧量增加,燃尽率变小,给煤停留时间是50 min、60 min、70 min时对应的燃尽率依次是90.5%、92.9%、93.6%;床层高度变低时,燃煤温度也在下降;给煤粒径不应太大,否则不易燃烧完全;链条炉的燃尽率是93.3%,效果较好;沿程燃尽率分析中,挥发分在给煤运行距离是2.5 m处就已燃尽,固定炭在灰渣出口处的燃尽率是92.8%。其次,探究了链条炉SNCR过程数值计算。计算结果显示:布置8支喷枪时的脱硝效率为46.2%,效果已较好;氨氮比越大,脱硝效率越高;最佳雾化粒径在300~400μm之间,脱硝效率最大值是54.7%;雾化角度越小越好;还原剂喷射速度越大脱硝效果越好,喷射速度从15 m/s增到60 m/s时,脱硝效率增长了7.4%;喷枪向下倾斜布置可改善脱硝效率;喷枪布置方式1且错列布置的脱硝程度最好,脱硝效率是54.9%。最后,开展了SNCR试验研究,考核了还原剂种类、还原剂流量、喷枪布置位置对脱硝程度的影响。结果表明:应用SNCR技术能达到13%~32%的脱硝效率;尿素的脱硝效率比氨水约高4%~10%;喷射流量越大脱硝效率越高;喷枪布置在5500 mm标高处的脱硝效率较高。试验结果可较好的吻合于数值计算结果。
[Abstract]:According to the present situation of no _ x emission in China and the comparative analysis of various denitrification technologies, a scheme of low nitrogen transformation using selective non-catalytic reduction (SNCR) technology in industrial chain furnace is put forward. In this paper, the thermal combustion of a 35t/h chain furnace and the denitrification characteristics of SNCR are studied numerically and experimentally. Firstly, the combustion numerical calculation of chain furnace is carried out, and the results of flow field, temperature field and gas component field are obtained. On this basis, the influence of boiler load and residence time of coal feed on the calculation results is investigated, and the variation of coal temperature and quality in the bed is analyzed, and the burnout rate of chain grate furnace is counted. The results showed that the concentration of CO _ 2 and O _ 2 decreased and the flue gas temperature increased at high load, and when the residence time of coal was short, the outlet smoke temperature decreased, the oxygen content increased, and the burnout rate became smaller. The corresponding burnout rate of coal feeding time is 50 min ~ 60 min ~ 70 min. The corresponding burnout rate is 90.5% and 92.9%. When the bed height becomes lower, the coal temperature is also decreasing, the coal particle size should not be too large, otherwise it is not easy to burn completely, the chain furnace burnout rate is 93 3%, and the effect is better. In the analysis of burnout rate along the process, the volatile matter was burned up at the distance of 2.5 m from the coal feed, and the burning out rate of the fixed carbon at the ash and slag outlet was 92.8%. Secondly, the numerical calculation of chain furnace SNCR process is discussed. The results show that the denitrification efficiency is 46.2 when the eight spray guns are arranged, the higher the ammonia nitrogen ratio is, the higher the denitrification efficiency is, the better the denitrification efficiency is when the optimum atomization diameter is between 300 渭 m and 400 渭 m, and the maximum denitrification efficiency is 54.7, the smaller the atomization angle is, the better the denitrification efficiency is. The greater the injection speed of reducing agent, the better the denitrification effect. When the injection speed increased from 15 m/ s to 60 m/ s, the denitrification efficiency increased by 7.4%; the downward slanting arrangement of the spray gun improved the denitrification efficiency; and the denitrification degree was the best in the misaligned arrangement of the spray gun layout 1. The denitrification efficiency is 54.9. Finally, SNCR test was carried out to examine the effect of reducing agent type, reducing agent flow rate and spray gun arrangement on denitrification degree. The results show that the denitrification efficiency of SNCR can reach 13%, the denitrification efficiency of urea is about 4% higher than that of ammonia water, the higher the jet flow rate is, the higher the denitrification efficiency is, and the higher the denitrification efficiency is when the gun is arranged at the height of 5500 mm. The experimental results are in good agreement with the numerical results.
【学位授予单位】：中国计量学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X701

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