大型垃圾焚烧炉低氮燃烧优化以及SNCR数值模拟研究

发布时间：2018-05-29 07:55

本文选题：垃圾焚烧炉 + 低氮燃烧　；参考：《华南理工大学》2016年硕士论文

【摘要】：经济的快速发展造成了我国城市化进程的加速,人口的大量聚集,使得产生的垃圾变成困扰城市的严重问题之一。目前垃圾处理方式主要有卫生填埋、堆肥和焚烧三种,其中填埋、堆肥处理均会占用大量宝贵的土地资源,对土壤和水源造成污染。焚烧处理因其具有减量化、无害化、稳定化的优点而越来越受到人们的重视,且可以燃烧产生的热量进行利用。但垃圾焚烧会有氮氧化物产生,污染环境。为了减少氮氧化物的排放以达到国家标准,各垃圾焚烧电厂对NO_x的生成及脱除十分重视。综合考虑各项脱硝技术的成本和效率,目前在焚烧烟气净化系统中SNCR的应用最为广泛。因此,有必要研究垃圾焚炉的低氮燃烧及SNCR脱除效率问题。本文利用FLIC床层计算程序、CFD数值模拟软件ANSYS 14.0对广州市某台750t/d大型城市生活垃圾焚烧炉进行数值模拟研究,对比验证其100%负荷实际运行工况数据,各项参数均在工程误差范围,符合模拟要求。模拟结果与实际燃烧工况结果相符合。利用验证后的焚烧炉模型,分析变负荷下的炉膛数值模拟结果,结果表明,随着焚烧炉负荷的降低,炉膛内整体温度水平下降,炉膛内高温区域逐渐抬升,且向炉膛中部靠拢,减轻了炉膛后墙的高温腐蚀。NO的高浓度区主要在炉排的后半段区域以及在炉膛内的高温区,主要是由于热力型和燃料型NO的生成,以及在还原性气氛的抑制作用三者协同下形成的。随着负荷的降低,CO的高浓度区域分布向第二级炉排前移,尾部烟道NO_X的排放浓度随着负荷的降低呈现明显上升趋势。对MCR工况下的垃圾焚烧炉进行深度空气分级配风优化,调整焚烧炉二次风口和燃尽风口配风比例,结果表明,二次风与燃尽风的比例为SA:OFA=0.65:0.35时,焚烧炉内燃烧状况较好,燃尽风占比的增加,有利于尾部烟道出口NO_X减排。研究不同还原剂(氨水和尿素)对SNCR反应的影响;对焚烧炉内温度场和烟气组分浓度场进行分析,并比较SNCR脱硝前后的NO_X排放浓度变化,同时分析垃圾焚烧炉SNCR脱除效率随不同负荷的变化规律,模拟分析结果表明,氨水溶液在锅炉能效和脱氮率以及安全因素方面都占有明显优势,适合作为SNCR喷射的最佳还原剂。MCR工况下的数值模拟结果显示,第一烟道SNCR反应效果十分明显,最终尾部烟道出口平面NO浓度为131.9mg/Nm3(转化为11%含氧量下),相较于未采用SNCR脱硝时的排放浓度273.1mg/Nm3(转化为11%含氧量下),脱硝率达到51.7%,是较为理想的脱硝效果。不同负荷下(50%、65%、80%、100%)的SNCR脱硝效果,除了50%负荷工况下的脱硝效果不理想以外,65%、80%、100%负荷下脱硝效率分别达到了45.1%、26.3%和51.7%。在焚烧炉MCR工况下,分别对喷嘴位置、喷射速度以及分层喷射比例对SNCR的脱硝效果影响进行模拟研究,结果表明,从第一烟道下部SNCR喷嘴喷入的还原剂可以与烟气进行充分的混合,还原反应较为充分,NO的脱除效果较好。而靠近第一烟道上部喷射的氨水会在烟气流的带动下流入第二烟道而发生漏氨现象。对喷嘴流速的研究结果显示,原始喷射速度工况(13.8m/s)的混流效果较好,还原剂反应较为充分,脱硝率达到51.7%,此工况的喷射速度可以作为比较适合的SNCR设计参考。另外,在还原剂总流量一定的情况下,增加下层SNCR喷嘴流量,有利于SNCR脱硝效率的提高,SNCR-1:SNCR-2:SNCR-3=6:3:1的流量配比使得垃圾焚烧炉脱硝效率达到53.3%,是比较良好的SNCR设计参数。
[Abstract]:The rapid development of economy has caused the acceleration of the urbanization process in our country. The mass accumulation of the population makes the waste become one of the serious problems that plague the city. At present, three kinds of garbage disposal methods are mainly sanitary landfill, composting and incineration, in which the landfill and composting will occupy a large amount of precious land resources and make the soil and water source. Pollution. Incineration treatment has attracted more and more attention because of its advantages of reduction, harmlessness and stabilization. The burning of heat can be used. But waste incineration will produce nitrogen oxides and pollute the environment. In order to reduce the emission of nitrogen oxides to meet the national standard, the generation of NO_x in various waste incineration plants and The removal of SNCR is the most widely used in the incineration flue gas purification system. Therefore, it is necessary to study the problem of the low nitrogen combustion and SNCR removal efficiency of the waste incinerator. This paper uses the FLIC bed calculation program and the CFD numerical simulation software ANSYS 14 to a 750t/d large in Guangzhou. The numerical simulation study of the municipal solid waste incinerator is carried out, and the actual operation data of the 100% load are compared and verified. All the parameters are in the range of engineering error and conform to the simulation requirements. The simulation results are in accordance with the actual combustion conditions. With the decrease of the load of the incinerator, the overall temperature level in the hearth is reduced, the high temperature area in the furnace is gradually lifted and closer to the middle of the furnace. The high concentration area of the high temperature corrosion.NO of the rear wall of the furnace is mainly in the second half of the hearth and the high temperature zone in the furnace, mainly due to the formation of the thermal and fuel type NO. With the reduction of the reduction of the reduced atmosphere, with the reduction of the load, the high concentration distribution of CO is moving forward to the second grade grate with the decrease of the load. The emission concentration of the tail flue NO_X is obviously rising with the decrease of the load. The depth air distribution of the waste incinerator under the MCR condition is optimized and the incinerator two is adjusted. The results show that when the proportion of the secondary air inlet and the burning vent is proportional to the air, the combustion status in the incinerator is better and the burning exhaust ratio increases when the proportion of the two air and the burnout wind is SA:OFA=0.65:0.35, which is beneficial to the emission reduction of the tail flue outlet NO_X. The effect of the different reductant (ammonia and urea) on the SNCR reaction is studied, and the temperature field and the smoke composition in the incinerator are also studied. The concentration field is analyzed, and the change of NO_X emission concentration before and after SNCR denitration is compared. At the same time, the change law of SNCR removal efficiency with different loads is analyzed. The simulation analysis shows that the ammonia solution has obvious advantages in the energy efficiency, the denitrification rate and the safety factors of the boiler, and is suitable to be the best reductant.M for the SNCR injection. The results of numerical simulation under CR condition show that the effect of SNCR reaction in the first flue is very obvious, and the final NO concentration in the exit plane of the tail flue is 131.9mg/Nm3 (converted to 11% oxygen content), and the denitrification rate of 51.7% is higher than that of 273.1mg/Nm3 (converted to 11% oxygen content) without SNCR denitrification, which is an ideal denitrification effect. The denitrification effect of SNCR under the same load (50%, 65%, 80%, 100%) is not ideal except for the 50% load condition, and the denitrification efficiency under 65%, 80% and 100% is 45.1%, 26.3% and 51.7%. respectively under the MCR condition of the incinerator, and the effect of the nozzle position, the jet speed and the stratified injection ratio on the denitrification effect of SNCR, respectively, is simulated. The results show that the reducing agent injected from the SNCR nozzle in the lower part of the first flue can be fully mixed with the flue gas, the reduction reaction is more sufficient and the removal effect of NO is better. And the ammonia water near the top of the first flue will flow into the second flue under the drive of the flue gas flow. The mixing effect of the original injection speed (13.8m/s) is better, the reducing agent reacts more fully and the denitrification rate reaches 51.7%. The injection speed of this working condition can be used as a reference for the suitable SNCR design. In addition, the increase of the lower SNCR nozzle flow rate is beneficial to the increase of the SNCR denitrification efficiency in the case of the total reducing agent flow rate, SNCR-1:SNCR-2:SN The discharge ratio of CR-3=6:3:1 makes the efficiency of denitration in MSW incinerator reach 53.3%, which is a good SNCR design parameter.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X705

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