660MW超临界墙式切圆燃烧锅炉烟温偏差数值模拟及优化

发布时间：2018-05-13 14:01

本文选题：墙式切圆燃烧 + 数值模拟　；参考：《华中科技大学》2015年硕士论文

【摘要】：切圆燃烧方式具有许多优点,在我国得到广泛的应用。切圆燃烧方式主要特点是炉内气流旋转,引起炉内旋转中心低压区卷吸高温烟气,让气流充分混合,形成良好的着火条件和稳定的燃烧环境,并且颗粒在炉内停留时间长,有利于燃尽。但由于炉膛高度有限,炉膛出口仍然存在气流的残余旋转,导致水平烟道处左右侧出现烟速偏差与烟温偏差的现象,使过热器与再热器的管屏左右侧吸热不均匀,出现热偏差现象,情况严重时,导致受热面出现超温爆管事故。因此,研究炉膛出口烟温偏差对提高锅炉运行的安全性、可靠性及经济效益均具有重要意义。本文针对一台660MW的墙式切圆燃烧超临界锅炉开展了烟温偏差优化的数值模拟,并对基准工况炉膛出口参数的模拟结果与实验结果进行了对比,模拟值与实验值相符合。结果表明:炉内形成了良好的切圆燃烧,煤粉颗粒停留时间长,有利于燃尽,NOX排放量较低,在进入分隔屏底前,炉内气流的温度场和速度场分布比较对称;但由于炉内形成逆时针旋转气流,在炉膛出口存在着气流的残余旋转,炉膛出口截面出现比较明显烟温偏差,温度高的区域集中在截面的右下角,炉膛出口截面的速度分布与温度分布呈现左低又高的分布。在基准工况的基础上,依次进行改变SOFA风水平摆角、二次风挡板开度、SOFA风挡板开度的模拟实验和试验研究,分析了其三种变工况对炉膛出口烟气速度与烟温偏差的影响。结果表明:随着SOFA风水平摆角逆时针摆动,炉膛内气流旋转强度减弱,出口截面水平分速度及切圆直径减小,烟温偏差随之减小;随二次风挡板开度增加时,炉膛内气流旋转强度较强,出口切圆直径及水平分速度增大,烟温偏差随之增大;随SOFA风挡板开度增加,其结果与二次风挡板开度增加相反。通过对三组变工况的调整,有效的降低了炉膛出口左右两侧的烟温偏差。
[Abstract]:Tangential combustion has many advantages and has been widely used in China. The main feature of tangential combustion is that the air flow in the furnace rotates, which causes the high temperature flue gas to be absorbed in the low pressure region of the rotary center in the furnace, so that the air flow can be fully mixed to form a good ignition condition and a stable combustion environment, and the particle stays in the furnace for a long time. In favor of burnout. However, due to the limited height of the furnace, there is still a residual air flow rotation at the outlet of the furnace, which leads to the deviation of the smoke velocity and the smoke temperature at the left and right side of the horizontal flue, resulting in uneven heat absorption between the left and the right side of the tube screen of the superheater and the reheater. The phenomenon of thermal deviation, when the situation is serious, lead to the accident of overheated tube explosion on the heating surface. Therefore, it is of great significance to study the deviation of flue gas temperature at furnace outlet to improve the safety, reliability and economic benefit of boiler operation. In this paper, the numerical simulation of flue gas temperature deviation optimization for a 660MW wall tangent circle combustion supercritical boiler is carried out. The simulation results of furnace outlet parameters under the standard operating conditions are compared with the experimental results, and the simulation results are in good agreement with the experimental results. The results show that a good tangential combustion is formed in the furnace, and the residence time of pulverized coal particles is long, which is beneficial to the low emission of no _ x from burn-out. Before entering the bottom of the separator screen, the distribution of the temperature field and velocity field of the gas flow in the furnace is relatively symmetrical. However, due to the formation of counterclockwise rotating air flow in the furnace, there is a residual rotation of the gas flow at the furnace outlet, and the section of the furnace outlet has a relatively obvious deviation of smoke temperature, and the high temperature area is concentrated in the lower right corner of the section. The velocity distribution and temperature distribution of the outlet section of the furnace show the left low and high distribution. On the basis of the reference condition, the simulation experiment and experimental study of changing the horizontal swing angle of SOFA wind and the opening degree of secondary windshield board and the opening degree of sofa windshield board are carried out, and the influence of three different working conditions on flue gas velocity and flue gas temperature deviation at furnace outlet is analyzed. The results show that with the counterclockwise swing of the horizontal swing angle of the SOFA wind, the intensity of the air flow in the furnace decreases, the horizontal velocity of the exit section and the tangential diameter decrease, and the deviation of smoke temperature decreases with the increase of the opening degree of the secondary windshield. With the increase of the opening degree of the SOFA windshield, the result is contrary to the increase of the opening degree of the secondary windshield plate with the increase of the air flow rotation intensity in the furnace and the increase of the tangential diameter and horizontal velocity of the outlet. By adjusting the three sets of variable working conditions, the deviation of flue gas temperature on the left and right sides of the furnace outlet is reduced effectively.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK229.2

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