火电厂燃煤锅炉超低排放流场优化分析及工艺研究

发布时间：2018-08-04 10:29

【摘要】：雾霾已成为我国北方冬季挥之不去的阴影,严重影响人们的身心健康,燃煤排放是造成雾霾的罪魁祸首之一。虽然煤炭燃烧污染物减排机理研究已非常成熟,各种减排措施也较为完善,但是在具体实施过程中却不尽人意,究其缘由,主要是减排工艺研究和实施过程不够精致,再加之系统稳定性不高,造成污染物超标排放。本文针对20余处火电厂燃煤锅炉烟气超低排放工程实施案例中抽化出的共性工艺及系统可靠性问题进行研究,主要研究内容如下：(1)在SCR脱硝系统中首层催化剂入口处烟气流场和氨浓度分布情况是影响脱硝效率的关键因素,为提高其烟气流场和氨浓度的均匀性,需对AIG上游的烟道进行优化设计。本文基于CFD数值模拟结合工程案例对AIG上游异径烟道内的不同导流板布置进行研究得到优化烟道布置方案,针对异径烟道需在其入口、出口布置非均匀导流板,在其上游添加直型引流板、下游添加直型整流板,确定额定烟气量下导流板位置、结构、尺寸等的优化配置方案。(2)在SCR脱硝过程中使烟气温度保持在催化剂最佳活性温度窗口是延长催化剂寿命和提高脱硝效率的有效方式,为此需保持烟气温度并使流场分布均匀。本文基于CFD数值模拟分析,通过设置省煤器高温段烟气旁路,将高温烟气与省煤器出口低温烟气混合,使混合烟气的温度达到催化剂的最佳反应温度区间。旁路烟道与主烟道的接口布置形式,是高低温烟气充分混合的关键。通过对包括圆柱形旁路烟道插入主烟道方案、矩形旁路烟道插入主烟道方案、文丘里喉管方案、静压箱方案等典型布置方案进行大量数值模拟研究,借鉴“静压箱”原理,确定了主烟道接口处上侧、左右两侧布置与旁路烟道等高“∏”形静压箱烟道方案。(3)在湿法脱硫系统中维持烟气与浆液“气-液”平衡是提高脱硫效率的关键控制要素,本文基于CFD数值模拟,对脱硫系统及内部构件进行优化设计,研究设置浆池分区装置、湍流强化装置、塔壁增效装置,并对脱硫塔内部的气液两相流动情况进行数值模拟,实现脱硫系统的匀质增效。数值模拟结果显示,脱硫塔内开启喷淋后在湍流强化装置、塔壁增效装置和喷淋层的联合作用下,消除了烟气偏流现象,实现了烟气流场的均布。(4)为保障脱硫系统可靠运行,需在脱硫塔入口设置保护措施,防止因烟气温度突升烧毁脱硫系统。本文基于CFD数值模拟,建立包含减温水喷射、湍流混合、传热传质等过程的数值模拟方法,通过计算分析烟道内喷水冷却后的烟气温度分布情况,确定喷嘴的最优布置形式,保障脱硫系统的可靠达标运行。(5)超低排放系统各处理单元之间的联络烟道内的流场特性对其下游处理单元的达标提效具有重要影响。引风机出口至WGGH间联络烟道(方圆节烟道)加装导流板后换热管区域烟气充满度大幅提高使得换热效果达到设计要求。脱硫塔出口至湿式静电除尘器入口间联络烟道(双向异径烟道)加导流板后使得WESP极板区域烟气分布均匀,工程应用中应对WESP入口烟气均布偏差系数和气流方向性均做考察。基于协同理论系统考虑减排要素,基于大量工程案例不断优化设计各子系统及各组件并进行系统优化配置,对各工程进行实地测量验证设计方案,通过对所测数据进行横向、纵向综合分析总结规律发现问题,以反馈至下个工程方案的设计再优化,不断改进,在周而复始过程中力求极致。本文研究成果已在20余个燃煤电厂的大气污染物处理工程得到应用,系统运行平稳,各项指标达到预期要求。该研究方案在山西某电厂#1机组超低排放改造工程得到实施。据《山西某电厂#1机组废气污染源现状监测报告》报告显示NOx排放浓度在10～14mg/Nm3,SO2排放浓度在16-19mg/Nm3。研究表明,本文研究成果经得起工程检验,各项指标均达到《火电厂大气污染物排放标准》(GB13223-2011)所规定的燃气机组排放限值,实现了超低排放。
[Abstract]:Haze has become the shadow of winters in the north of China, which seriously affects people's physical and mental health. Coal emission is one of the leading causes of fog and haze. Although the mechanism of coal combustion pollutant emission reduction is very mature and various measures are more perfect, but in the implementation process, it is not satisfactory. The main reason is the reason. The research and implementation process of the emission reduction technology is not delicate, and the system stability is not high, and the pollutant discharge is exceeding the standard. In this paper, the common process and system reliability problems extracted from more than 20 coal-fired boiler flue gas ultra low emission projects in thermal power plants are studied. The main contents are as follows: (1) the SCR denitrification system The flue gas flow field and the concentration distribution of ammonia at the entrance of the middle first layer of catalyst are the key factors affecting the denitrification efficiency. In order to improve the flue gas flow field and the uniformity of ammonia concentration, the optimization design of the flue of the upstream of AIG is needed. Based on the CFD numerical simulation combined with the project case, the layout of different diversion plates in the upstream different diameter flue of AIG is studied. In order to optimize the layout scheme of flue gas channel, the non uniform flow plate is arranged in the outlet, the outlet is arranged in the outlet, the direct type drainage plate is added to its upstream, the straight rectifying plate is added to the downstream, the optimal configuration of the diversion plate position, structure and size under the rated flue gas amount is determined. (2) the flue gas temperature is kept in the catalyst most during the SCR denitrification process. The good active temperature window is an effective way to prolong the life of the catalyst and improve the denitrification efficiency. Therefore, it is necessary to keep the temperature of the flue gas and make the distribution of the flow field evenly distributed. Based on the CFD numerical simulation analysis, the flue gas of the high temperature section of the economizer is mixed with the low temperature flue gas at the exit of the economizer to make the temperature of the mixed flue gas catalyze. The optimum reaction temperature range of the agent, the layout of the interface between the bypass flue and the main flue, is the key to the full mixing of the high and low temperature flue gas. A large number of typical layout schemes, including the main flue, the rectangular bypass flue into the main flue, the Venturi throat scheme and the static pressure box scheme, are numerically simulated. Based on the principle of "static pressure box", this paper determines the upper side of the main flue interface, the layout of the left and right sides and the bypass flue. (3) to maintain the gas liquid balance between the flue gas and the slurry in the wet desulphurization system is the key control factor to improve the desulfurization efficiency. Based on the CFD numerical simulation, the desulfurization system and the desulfurization system are used in this paper. The internal components are optimized, the partition device of the slurry pool, the turbulence intensifying device, the tower wall synergistic device, and the numerical simulation of the gas-liquid two phase flow in the desulfurization tower are simulated to achieve the uniformity and efficiency of the desulfurization system. The numerical simulation results show that the turbulence intensification device, the tower wall synergist and the spray in the desulphurization tower are opened in the desulphurization tower. In order to ensure the reliable operation of the desulfurization system, the protection measures should be set up at the entrance of the desulphurization tower to prevent the desulphurization system from burning up because of the temperature rise of the flue gas. Based on the CFD numerical simulation, this paper establishes the process of setting up the heat and mass transfer process including the cooling water jet, the turbulence mixing and the heat and mass transfer. The numerical simulation method, through the calculation and analysis of the distribution of the flue gas temperature after the water spray cooling in the flue, determines the optimal arrangement of the nozzle, and ensures the reliable operation of the desulfurization system. (5) the flow field characteristics in the contact flue between the treatment units of the ultra low emission system have an important influence on the efficiency of the downstream processing unit. After the outlet of the air blower to the contact pipe between the WGGH and the pipe (the square section flue), the heat transfer effect reaches the design requirement after the diversion plate is added to the diversion plate, which makes the heat exchange effect reach the design requirements. The flue gas distribution in the WESP plate area is evenly distributed after the exit of the desulfurizer outlet to the inlet of the wet electrostatic precipitator entrance (two way flue) and the diversion plate, and the engineering application is applied. On the basis of a large number of engineering cases, we should optimize the design of the subsystems and components and optimize the system configuration based on a large number of engineering cases. Based on a large number of engineering cases, we carry out a field measurement verification plan for each project, through the horizontal and longitudinal measurements of the measured data. The research results have been applied in the air pollutant treatment project of more than 20 coal-fired power plants, and the system runs smoothly and the targets have reached the expected requirements. The research scheme is in the mountain. The ultra low emission transformation project of #1 unit of a power plant in a power plant is implemented. According to the report of the status monitoring report of the exhaust gas pollution source of the #1 unit in a power plant in Shanxi, the emission concentration of NOx is from 10 to 14mg/Nm3, and the SO2 emission concentration in the 16-19mg/Nm3. study shows that the results of this study can stand the engineering test, and all the indexes have reached the emission of the air pollutants in the thermal power plant. The emission limits of gas generating units stipulated in standard (GB13223-2011) have achieved ultra-low emission.
【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：X773

【参考文献】