炉排式垃圾焚烧炉燃烧与SNCR系统优化设计的模拟研究

发布时间：2018-03-12 16:33

本文选题：焚烧炉　切入点：氮氧化物　出处：《华东理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：氮氧化物是大气的主要污染物之一,对环境危害极大。垃圾焚烧炉排放的尾气中含有氮氧化物。随着我国对氮氧化物排放的管控力度加大,排放标准提高,如何有效地控制炉排式垃圾焚烧炉氮氧化物的排放是一个重要问题。在现有的NOx控制技术中,选择性非催化还原(SNCR)工艺因其经济型和有效性而应用在垃圾焚烧炉烟气处理。但是,由于SNCR反应温度窗口具有严格要求,在垃圾焚烧炉实际运行中存在脱硝效率低等问题,如何改善垃圾焚烧炉燃烧状况,控制炉内温度分布,优化SNCR系统运行是实际运行中亟待解决的问题。本文采用数值模拟方法,利用计算流体力学软件对某城市日处理量750t的炉排式垃圾焚烧炉进行建模计算,根据模拟结果对垃圾焚烧炉内SNCR系统的优化设计提供了参考依据。本文研究包括以下方面：1.建立焚烧炉的燃烧模型,通过FLIC程序与商业软件FLUENT结合,模拟垃圾焚烧炉内燃烧的过程。具体地,就是利用FLIC程序模拟炉排上燃烧过程；得到床层表面烟气的相关数据,以此作为FLUENT模拟炉膛燃烧的入口边界条件,模拟计算得到焚烧炉内温度场、浓度场及流场的分布情况。2.在垃圾燃烧模拟的基础上建立焚烧炉SNCR脱硝反应模型,采用简化的SNCR反应机理模拟焚烧炉内SNCR还原反应,考察不同工艺参数对SNCR运行的影响。根据模拟计算结果,对工艺参数优化组合,确定焚烧炉SNCR系统的最佳运行条件。3.通过对焚烧炉二次风喷射对炉内燃烧及SNCR脱硝的影响分析,探索二次风喷射角度变化,使炉内温度分布更加均匀,脱硝效率得到提高。4.以某地垃圾焚烧炉为例,应用以上模型,模拟分析焚烧炉燃烧室结构对炉内结焦的影响。研究结果表明：垃圾热值的变化会对焚烧炉内燃烧状况产生影响,垃圾热值下降导致炉内辐射强度降低,导致炉排着火相对滞后,燃烧不充分。通过对SNCR系统工艺参数影响的分析,最终确定当雾化角45°,50m/s喷射速度,NSR=I.5,在Rosin-Rammler粒径分布的条件下,位于前墙上的两个喷嘴的组合为SNCR系统的最佳运行条件。通过对二次风喷嘴角度的调整,设计了合理的二次风喷射,能够使焚烧炉内温度分布均匀,脱硝效率最大可提高近20%。数值模拟计算结果表明,垃圾焚烧炉中间隔板的设计有助于低质垃圾炉内燃烧的进行,中间隔板的设计是影响炉内结焦的主要原因。
[Abstract]:Nitrogen oxide is one of the main pollutants in the atmosphere, which is harmful to the environment. There is no oxide in the tail gas of waste incinerator. It is an important problem how to effectively control the nitrogen oxide emission from the grate type waste incinerator. In the existing NOx control technology, The selective non-catalytic reduction (SNCR) process has been used in flue gas treatment of waste incinerators due to its economic efficiency and efficiency. However, due to the strict requirements of the SNCR reaction temperature window, there are some problems such as low denitrification efficiency in the actual operation of the MSW incinerators. How to improve the combustion condition of MSW incinerator, how to control the temperature distribution in the furnace and how to optimize the operation of SNCR system are the problems to be solved urgently in actual operation. By using the computational fluid dynamics software, the waste incinerator with a daily treatment capacity of 750 tons per day in a certain city is modeled and calculated. According to the simulation results, the paper provides a reference for the optimization design of SNCR system in MSW incinerator. The research includes the following aspects: 1. Establish the combustion model of incinerator, and combine it with commercial software FLUENT through FLIC program. To simulate the combustion process in the MSW incinerator. Specifically, the combustion process on the grate is simulated by using the FLIC program, and the relevant data of flue gas on the bed surface are obtained as the inlet boundary conditions for the FLUENT to simulate the furnace combustion. The distribution of temperature field, concentration field and flow field in incinerator was obtained by simulation. 2. Based on the simulation of MSW combustion, the SNCR denitrification reaction model of incinerator was established, and the SNCR reduction reaction in incinerator was simulated by simplified SNCR reaction mechanism. The effects of different process parameters on the operation of SNCR were investigated. According to the results of simulation and optimization of process parameters, the optimum operating conditions of SNCR system of incinerator were determined. 3. The effect of secondary air injection on combustion and SNCR denitrification in incinerator was analyzed. The change of the angle of secondary air injection is explored to make the temperature distribution in the furnace more uniform and the denitrification efficiency improved .4.With a waste incinerator in a certain place as an example, the above model is applied. The influence of combustor structure on coking in incinerator is simulated and analyzed. The results show that the change of waste calorific value will affect the combustion state in incinerator, and the decrease of waste calorific value will decrease the radiation intensity in incinerator. By analyzing the influence of process parameters of SNCR system, it is determined that when the atomization angle is 45 掳~ 50 m / s and the injection velocity is 45 掳~ (50) m / s ~ (-1), under the condition of Rosin-Rammler particle size distribution, the ignition of the grate is relatively delayed and the combustion is not sufficient. The combination of the two nozzles on the front wall is the best operating condition for the SNCR system. By adjusting the angle of the secondary air nozzle, a reasonable secondary air jet is designed, which can make the temperature distribution in the incinerator uniform. The results of numerical simulation show that the design of intermediate combustor of MSW incinerator is helpful to the combustion of low-quality MSW, and the design of intermediate partition is the main reason that affects the coking in the furnace.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X705

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