生活垃圾焚烧烟气脱硝模拟及在运行优化中的应用

发布时间：2018-06-25 23:47

本文选题：CFD + 垃圾焚烧炉烟气脱硝　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：随着城市化进程的发展,我国城市垃圾问题日益严重。垃圾焚烧技术以其减量化‖及资源化‖等优势,逐渐成为我国垃圾处理的主流技术。垃圾焚烧不可避免的会产生二次污染气体,其中NOx是垃圾焚烧产生的主要污染物之一。为控制垃圾焚烧NOx的排放,以达到最新国家和地方标准,应对现有垃圾焚烧炉进行脱硝改造。选择性非催化还原(SNCR)脱硝技术改造简单、运行成本相对较低,是目前较流行的生活垃圾焚烧炉烟气脱硝技术之一。本文以一台400 t/d生活垃圾焚烧炉为研究对象,利用计算流体力学(CFD)软件提出垃圾焚烧炉烟气脱硝优化改造方案。首先模拟焚烧炉内的气相燃烧过程和SNCR脱硝反应过程,并通过获取现场实测值、实验验证、文献佐证等方式验证所建立模型的可靠性。其次利用数值模拟方法,对垃圾焚烧的气相燃烧过程和SNCR还原剂喷射过程进行优化。最终提出并评估各垃圾焚烧炉烟气脱硝综合优化方案。本文在优化气相燃烧过程时,设计了6种二次风喷射方式优化方案,考察各喷射方式对炉内烟气运动及燃烧反应的影响。结果表明:优化二次风喷射方式可使炉内形成螺旋结构,并使二次风停留时间最高提升40.62%。以此为基础,优化二次风喷射速度,使一次风:二次风值为0.72:0.28时,达到优化喷射条件。利用SNCR模型,通过单因素模拟和正交模拟,研究喷枪喷射参数(喷射粒径、喷射速度、喷射角、喷射量、喷射浓度)对SNCR系统还原剂蒸发和混合的影响。根据研究结果,设计的最佳喷射参数为:喷射粒径为400μm,喷射速度为35 m/s,喷射角为30°,喷射量50 kg/h,喷射浓度为25%。应用最佳喷射参数,研究喷枪个数和喷枪位置对还原剂分布的影响。设计的喷射最佳排布方式为:8喷枪喷射,采用4墙对喷方式,每墙各2喷枪,喷枪在各墙壁上由中央向两侧依次排布。结合气相燃烧过程优化和SNCR过程优化,设计并筛选脱硝效果较好的综合优化方案进行工程成本及环境经济效益评估。各综合优化方案中,最佳脱硝效果方案的脱硝率可达55.52%。最低工程成本方案在改造15年时垃圾脱硝成本为5.46元/t。最佳环境经济效益方案在改造15年时吨NO去除成本为5 597元/t。以上方案的NO排放最高为183.8 mg/Nm3,满足《GB18485-2014生活垃圾焚烧污染控制标准》和欧盟2000标准,且漏氨体积分数均小于10-4。
[Abstract]:With the development of urbanization, the problem of urban garbage in China is becoming more and more serious. MSW incineration technology has gradually become the mainstream technology of garbage disposal in our country because of its advantages of reducing quantity and resources. MSW incineration will inevitably produce secondary pollution gas, among which NOx is one of the main pollutants produced by MSW incineration. In order to control NOx emission from MSW incineration to meet the latest national and local standards, the existing MSW incinerator should be denitrified. Selective non-catalytic reduction (SNCR) denitrification is one of the most popular flue gas denitrification technologies in domestic waste incinerators because of its simple revamping and relatively low operating cost. In this paper, a 400 t / d MSW incinerator is used as a research object, and a scheme for optimizing flue gas denitrification of MSW incinerator is proposed by using computational fluid dynamics (CFD) software. Firstly, the gas combustion process and SNCR denitrification process in the incinerator were simulated, and the reliability of the established model was verified by obtaining the field measured values, experimental verification and documentary evidence. Secondly, the gas combustion process and SNCR reducing agent injection process of MSW incineration were optimized by numerical simulation. Finally, a comprehensive optimization scheme for flue gas denitrification of waste incinerators is proposed and evaluated. In this paper, six optimization schemes of secondary air injection are designed to optimize the gas combustion process, and the effects of different injection modes on the flue gas movement and combustion reaction in the furnace are investigated. The results show that the helical structure can be formed by optimizing the secondary air injection mode and the residence time of the secondary air can be raised by 40.622. On the basis of this, the injection velocity of secondary air is optimized to reach the optimal injection condition when the secondary air value is 0.72: 0.28. The effects of spray parameters (particle size, injection velocity, injection angle, injection volume and injection concentration) on the evaporation and mixing of reducing agent in SNCR system were studied by single factor simulation and orthogonal simulation using SNCR model. According to the results of the study, the optimum injection parameters are as follows: the injection diameter is 400 渭 m, the injection velocity is 35 m / s, the injection angle is 30 掳, the injection amount is 50 kg / h, the injection concentration is 25%. The effects of the number and position of the spray gun on the distribution of reducing agent were studied by using the optimum injection parameters. The optimal arrangement of spray is designed as: 1: 8 spray gun, 4 wall jet on each wall, 2 guns per wall, and the spray gun is arranged from the center to the two sides on each wall in turn. Combined with gas combustion process optimization and SNCR process optimization, a comprehensive optimization scheme with better denitrification effect was designed and selected for engineering cost and environmental economic evaluation. Among the comprehensive optimization schemes, the denitrification rate of the best denitrification scheme can reach 55.52%. The minimum project cost is 5.46 yuan / t when the cost of waste denitrification is 5.46 yuan / t. The cost of no removal is 5 597 yuan / t when the best environmental economic benefit scheme is reformed for 15 years. The highest no emission of the above scheme is 183.8 mg / Nm ~ (3), which meets the < GB18485-2014 MSW incineration pollution control standard] and EU 2000 standard, and the ammonia leakage volume fraction is less than 10-4.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X701

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