【作者】 王晓娟；

【导师】 史月涛；

【作者基本信息】 山东大学 ， 动力工程及工程热物理， 2017， 硕士

【摘要】 近几年来,PM2.5等颗粒物污染日益严重,对人类的生存环境和身体健康构成了严重的威胁,所以提高除尘器的除尘效率势在必行。本文以袋式除尘器为主要研究对象,旨在为除尘器的优化发展提供一定的帮助与支持。本文分别通过实验研究与数值计算两种手段对传统式和旋转式两种结构下的袋式除尘器展开了研究。并通过对获得的运行阻力结果的比较确定了实验与数值模拟的统一性。文中结合湿式除尘技术提出了将袋式除尘器的干式滤袋改进为湿式滤袋的湿式除尘技术。理论分析认为,对滤袋加湿以后,可以降低滤袋的孔隙率,过滤时筛分效应增强,并减少了粉尘颗粒对滤料纤维孔隙的填充,促使过滤模式更早的过渡到表层过滤,可以有效提高除尘效率而且清灰更加方便。同时喷水加湿以后,粉尘颗粒表面的粘附力增大,细小颗粒物团聚成为大颗粒从而更容易被捕集。综上,采用湿式袋式除尘器可以有效地提高除尘器的除尘效率,但也会使运行阻力上升。所以本文主要对两种结构除尘器的运行阻力和对粉尘的捕集效率两种除尘特性进行了研究。对于传统式袋式除尘器,气流分布的均匀性是衡量袋式除尘器设计优劣的标准之一。文中通过数值计算对其内部的流场进行分析,得到气流的流动与分配规律,并根据评价气流均匀性的三个指标—对进行定量的评价。结果显示,各项指标均在允许范围之内,可以认为气流分布基本均匀。对于传统式除尘器共计研究了介于1.00m/min～3.00m/min之间的九种过滤风速下,分别采用干式与湿式滤袋时除尘系统的运行阻力和过滤效率变化规律。研究结果显示随着过滤风速增加,在干式与湿式滤袋状态下,运行阻力都在逐渐增加,而除尘效率呈现出先降低后升高的规律。采用湿式滤袋时,系统的运行阻力约变为干式滤袋时的3倍左右,除尘效率有明显的提高,增幅约在0.6%～0.8%之间,粉尘排放浓度降低至干式时的75%到82.9%之间不等。对于文中新提出的旋转式袋式除尘器,首先通过数值计算对两个结构参数比间距和充填比进行最优化设计计算,并最终选取比间距为20,充填比为14时的参数组合进行实验研究。实验中对介于0.3m/s～1.4m/s之间的8种迎面风速下,分别采用干式和湿式滤袋时除尘器的运行阻力和对粉尘的捕集效率进行研究。结果显示采用干式和湿式滤袋时系统的运行阻力和对粉尘的捕集效率都随着风速的增加而逐渐提高。采用湿式滤袋后,旋转式的运行阻力和除尘效率都有所增加,其中运行阻力约上升为干式滤袋的2.6～2.7倍,除尘效率的增幅约在0.4%～0.6%之间,除尘器出口排烟粉尘浓度降为干式的82.8%～91.8%之间不等。文中提出的湿式滤袋除尘技术可以有效地提高除尘器的除尘效率,大幅度降低排烟的粉尘浓度,但是阻力增幅较大,适用于作为除尘器的二级或者末级除尘设备,用于除去细小的粉尘颗粒,并避免过大的阻力和发生结露。对于本文中提出的旋转式袋式除尘器,其运行阻力低,但是也在一定程度上降低了除尘效率。所以旋转式袋式除尘器适用于对粉尘的性质和除尘效率要求不高的场合,也可以用作除尘器的初级除尘单元,或者通过适当的增加滤层数目在控制阻力的前提下提高除尘效率。本文的研究对湿式滤袋除尘技术和袋式除尘器的优化设计提供了参考,具有一定的理论研究和实际应用价值。更多还原

【Abstract】 The flue gas emission of coal-fired power plant is one of the major sources of atmospheric pollutant.Especially in those years,pollution of fine particles like PM2.5 is getting worse,which has brought great threats to the health of human beings.It’s imperative to improve the collection efficiency of particles especially to fine particles.The paper investigated on bag filter in order to offer help for the design optimization of bag filters.Both methods of experiment tests and numerical simulations were investigated on the traditional and rotating bag filters.The results of two methods were proved to be consistent with each other by comparing the running resistance.A new method of wet bag filter was put proposed in this paper.Theoretical analysis shows that when wetting the filter bag,the porosity decreases,the screening effect gets enhanced.At the same time,water droplets occupy the space of pores of the filter bags,which will reduce the filling of dust particles.As a result of that,the filter mode will transit from depth filtration to surface filtration much earlier.The mode of surface filtration can improve the dust removal efficiency effectively,and it’s easier to clean the dust layer on the surface of filter bags.What’s more,when spraying water into the system,the adhesion force of dust particles increases.Small particles will agglomerate into larger ones,which is favorable for the dust removal.In summary,the wet type bag filter can improve the dust removal efficiency,but the working resistance will increase with it too.So this paper investigated on the working resistance and dust removal efficiency under different conditions of bag filters.The uniformity of airflow is one of the evaluation standards for the design of traditional bag filters.The paper analyzed the flow low and uniformity of airflow according to the simulation results.Three standards of Flow Distribution Coefficient,Maximum Flow Amplitude and Average Flow Amplitude were applied to evaluate the uniformity of airflow.The results showed that,all the targets meet the request,so it could be reckoned to be uniform.For the traditional bag filter,nine filtration velocities between 1.00m/min and 3.00m/min were investigated.The effects of velocity on the pressure drop and dust removal efficiency were analyzed.The results indicated that with the increasing velocity,the working resistance increased,dust removal efficiency decreased firstly and then increased.When using the wet bag filter,the working resistance increased about three times of the dry bag filter.There was an obvious increase in the dust removal efficiency.The growing rate was among 0.6%to 0.8%.The dust emissions decreased,the decreasing rate was among 75%-82.9%.For the rotating bag filter,the numerical simulation method was firstly used for the structural optimum design.According to the simulation results,the specific spacing of 20 and the filling ratio of 14 were selected for experimental investigation.Eight face velocities between 0.3m/s to 1.4m/s were investigated by the experiment.The results showed that both the working resistance and dust removal efficiency increased with the face velocity.When using the wet bag filter,both the working resistance and dust removal efficiency increased.The working resistance of wet bag filter was 2.6～2.7 times of the dry.The dust removal efficiency growing rate was among 0.4%-0.6%.The dust emissions decreased to 82.8%～91.1%.The wet bag filter technology presented in this paper could enhance the dust removal efficiency,reduce the dust emissions.But it also leaded to a sharp increase in the working resistance.So the wet bag filter can be used as a secondary dust removing equipment,aiming at trapping the fine particles in the gas.Considering the performance of the rotating bag filter,the working resistance was low,and it was remarkable in dealing with huge amount of gas flow.But the dust removal efficiency dropped.Above all,the rotating bag filter was suitable for conditions whose requests for dust removal and dust characteristics were low.It could be also used as a primary dust collector.Besides,it was also feasible to improve the dust removal efficiency of rotating bag filter by adding the number of filtering layers.The investigations in this paper offered some help for the development and application of the wet bag filter technology and optimization design of bag filters.So the study has a certain reference research and practical value.更多还原