湿法烟气脱硫除雾效率和流场优化的数值模拟研究

发布时间：2018-01-15 20:43

本文关键词：湿法烟气脱硫除雾效率和流场优化的数值模拟研究　出处：《东南大学》2015年硕士论文　论文类型：学位论文

【摘要】：环境形势的日益严峻和环保要求的进一步提高,使粉尘、酸雾等大气污染物的治理日益受到人们的重视。除雾器作为燃煤电厂烟气除雾的主要设备,其除雾性能好坏决定除雾后烟气能否达到排放标准。为了研究提高除尘、除雾效率的有效方法,本文对燃煤电厂湿法脱硫系统中广泛使用的折流板除雾器和近年发展起来的应用在湿法脱硫塔后,在脱除PM2.5、硫酸雾、微细粉尘、汞金属等方面取得了良好效果的湿式电除(雾)尘器进行了数值模拟研究。分析了不同参数对折流板除雾器除雾效率的影响；研究了提高湿式电除尘器内部流场均匀性的流场调节的常规方法和新方法。本文的主要研究内容包括以下几个方面：(1)针对目前燃煤电厂湿法脱硫系统中广泛使用的折流板除雾器,本文利用欧拉—格朗日法对湿法脱硫折流板除雾器内气液两相流动建立数学模型。参考已有实验研究对本文所建立模型进行验证。通过模拟计算得到除雾器叶片间距、板型、流速对不同粒径雾滴的分级除雾效率和总除雾效率的影响,得到不同粒径雾滴的运动轨迹和捕集规律：流速在2-7 m·S-1,板间距在20,26,38mm范围的梯形和三角形叶片除雾器,粒径小于16μm的雾滴去除效率随流速增加呈现不规律的波动,随着板间距的增加而下降的趋势不明显,几乎不受叶片形状变化的影响；粒径大于16μm的雾滴去除效率随流速增加而增大,随着板间距增加显著下降；在板间距为38mm时,梯形板除雾效率大于三角形板,在板间距较小的情况下,两种板型的性能相差不大；流速小于3 m·s1时,粒径小于20μm雾滴的去除对气流均匀性要求较高,气流扰动增强利于小雾滴的碰撞聚并；流速高于3 m·S-1时,气流扰动增强增加了小雾滴运动的随机性,不利于小雾滴的碰撞聚并。(2)针对湿式电除尘器在工业应用中存在流场分布不均导致的除尘、除雾效率降低等问题,本文以某电厂湿式电除尘器改造项目为案例,对湿式电除尘流场进行了数值模拟计算,将模拟结果与现场实验测试结果对比,验证了模拟的准确性。通过流场分析得到除尘器入口流量分配不均和电场区流场分布不均的原因,利用流场调节的常规方法,通过设置导流板,气流分布板等措施,对入口烟道,进气喇叭等结构进行改造,使得入口流量分配均匀,电极迎风面流场分布得到改善。分析得出：为使入口流量均匀分配,应综合采用以下措施：增加入口烟道宽度、在入口烟道转弯处增设圆弧导流板、在联箱内增加斜导流板；圆弧导流板能对烟道内的气流流动起到良好的组织作用,进气喇叭的锥度不能过小,否则会引起气流对湿式电除尘器内部电场区的直接冲刷,且增加系统压降；进气喇叭内设置角度沿锥度较小一侧倾斜的导流斜板,将气流导向锥度较小一侧区域,可改善由于喇叭原始结构的缺陷造成的喇叭出口流场分布不均的问题；常规的流场调节方法虽然能在一定程度上改善气流分布,降低流速峰值,其调节过程需要反复调试,且调节后的流场仍然无法满足一些湿式电除尘器对流场均匀性的高要求。(3)基于数值模拟方法研究探讨了一种调节流场均匀性的新方法,利用横向和纵向隔板相互交错在喇叭口内形成梯形导流结构,根据喇叭出口截面某区域流量与对应的喇叭入口该区域面积的关系,能够分别在两个方向对喇叭口出口截面流场进行调节。与常规方法相比能够有效降低流速偏差,使电极迎风面流速在2～3m/s的区域面积占78%,流速偏差达到0.19,提高目标截面的流速均匀性；为了避免两个方向的流量调节相互干扰,喇叭口内的横向隔板与纵向隔板的高度应保留一定的高度差,差值根据喇叭尺寸确定；横向与纵向隔板数量或梯形蜂巢结构导流栅格的数目的设定,是根据对流场均匀性的要求来确定的,其数目越多,可实现的均匀性越高。
[Abstract]:The increasingly severe environmental situation and environmental requirements to further improve the management of dust, mist and other atmospheric pollutants has attracted more and more attention. As a coal-fired power plant flue gas demister main equipment in addition to fog, the fog removal performance determines whether in flue gas can reach the discharge standard after the fog. In order to study the effective method to raise the dust, mist in this paper, efficiency, widely used in coal-fired power plant wet FGD system in baffle demister and developed in recent years in the application of wet desulfurization tower, the removal of PM2.5, sulfuric acid mist, dust, and other aspects of mercury has achieved good results in wet electric dust collector (FOG) is simulated study on the analysis of the different parameters. Besides the effect of baffle mist mist removal efficiency; to study the wet electrical precipitator internal flow field of the conventional method of uniform flow field adjustment and new methods to study in this paper. The content includes the following aspects: (1) according to the current widely used in coal-fired power plant wet FGD system in baffle demister, the wet desulfurization baffle in gas-liquid two-phase flow in the mist, the mathematical model is established. Using the Euler Lagrange method experimental study on reference has been established in this paper to verify the model. Demister blade spacing plate, by simulation, velocity of different size droplet classification demisting efficiency and total efficiency of the demister, the motion trace of different particle size and droplet trapping Law: velocity in 2-7 m S-1, the distance between the trapezoidal plate in the range of 20,26,38mm and triangular blade mist eliminator the diameter of less than 16 m, the droplet removal efficiency decreased with the increase of flow rate in irregular fluctuations decreased with increasing trend of the plate spacing is not obvious, hardly affected by leaf shape change; particle size larger than 16 m fog Droplet removal efficiency decreased with the increase of flow rate increases, with the increase of plate spacing decreased significantly; the plate spacing is 38mm, trapezoidal plate demisting efficiency is greater than the triangular plate, the plate spacing is smaller, the performance of two plate types had little difference; flow rate is less than 3 m - S1, the diameter of less than 20 m droplet the removal of the airflow uniformity higher, air turbulence enhanced collision to small droplet coalescence; flow rate is higher than 3 m - S-1, the increase of airflow disturbance random droplet movement, is not conducive to the collision of small droplet coalescence. (2) for removal of wet electric dust collector has the flow field distribution in industry application in the poor, in addition to the fog and low efficiency, in a power plant wet electrical precipitator retrofit project as a case of wet ESP flow field is simulated, the simulation results and experimental test results verified the simulation of quasi Sure. The flow field analysis by flow distribution in ESP entrance and uneven electric field causes the uneven distribution of the flow field, the conventional method using the flow field in the control by setting the guide plate, the airflow distribution board and other measures of entrance flue of intake horn structure, the entrance flow distribution, flow field distribution of the windward side electrode improved. Analysis shows that: in order to make the entrance flow uniform distribution, should adopt the following measures: increase the flue entrance width, adding arc guide plate in the corner entrance flue, increasing inclined guide plate in headers; arc guide plate can flow in the flue gas flow on the organizations have played a good role, air horn does not taper too small, otherwise it will cause the flow of direct erosion of wet electric dust collector of internal electric field area, and increase the system pressure drop; angle along a small inlet horn side inclined taper Guide board, one side of the air guide taper smaller area can be improved due to the defects of original horn horn outlet flow field structure of the problem of uneven distribution; conventional flow field regulating method although can improve the flow distribution in a certain extent, reduce the peak velocity, the adjusting process requires repeated debugging, and still can not be adjusted flow meet some of the wet electrical precipitator flow field uniformity requirements. (3) numerical simulation method to study a new method for adjusting the flow uniformity based on the horizontal and vertical baffles are mutually staggered to form trapezoidal diversion structure on the bell mouth, according to the relationship between horn outlet section a regional flow and the corresponding speaker entrance the area of the region, can be respectively in the two directions of the bell flow at the exit section. The adjustment can effectively reduce the velocity deviation compared with the conventional method, the electrode of attack The wind velocity in the area of 2 ~ 3m/s accounted for 78%, flow rate deviation reached 0.19, the goal of improving the uniformity of the velocity in cross section; in order to avoid the two direction regulating the flow of mutual interference, the transverse clapboard and a longitudinal baffle the bell mouth height should retain a certain height difference, the difference according to the number of horizontal and horn size determination; the number of longitudinal baffle or trapezoidal honeycomb structure diversion grid set, according to the flow field uniformity requirements to determine, the number of the more uniformity can be achieved more.

【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X773

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