长袋脉冲袋式除尘器清灰压力场及除尘流场的模拟分析

发布时间：2018-04-25 22:12

本文选题：袋式除尘器 + 脉冲喷吹清灰　；参考：《兰州交通大学》2015年硕士论文

【摘要】：在大气污染十分严峻的背景下,各行业的排放标准越来越严格,而长袋脉冲袋式除尘器可以比较容易的适应新标准,应用越来越广泛。在此过程中袋式除尘器越来越大型化,需要对其进一步的研究,特别是清灰系统和流场分布的研究,以提高设备的整体效率及寿命。目前很难对除尘器内部复杂的气固两相流场进行测试,而CFD数值模拟方法可以得到喷吹清灰过程和除尘时内部流动情况,可以为袋式除尘器的改进提供一些依据。清灰效果是影响除尘器能否正常工作的重要因素,中箱体内的气流分布对除尘器寿命的影响也很大。本文使用ICEM网格划分软件对喷吹区域和整个除尘器分别建立1:1的几何模型,并划分结构化网格;利用计算流体力学方法分别对脉冲喷吹清灰过程中压力分布和除尘时气流分布情况进行模拟分析。通过脉冲喷吹过程模拟结果和实验数据的对比,验证了数值模拟过程的合理性,并对文丘里管、喷吹压力和滤袋长度对滤袋壁面压力分布的影响进行了模拟分析,得出:文丘里管对滤袋壁面峰值压力影响较大,在相同的喷吹条件下使滤袋壁面最大峰值压力由16.9kPa减小至15.7kPa,降低了7%,出现峰值的位置向后推移0.5m,滤袋中下游的峰值压力由7.5kPa减小至5.4kPa,降低了28%;脉冲喷吹压力对滤袋壁面各位置的峰值压力影响都很大,在不设文丘里管的情况下,当喷吹压力为0.35MPa时,峰值压力为18.5kPa,下游压力为8kPa;当喷吹压力为0.2MPa时,峰值压力为13.7kPa,下游压力为3.8kPa;最大峰值压力和下游峰值压力分别降低了26%和53%;在相同的喷吹条件下,滤袋长度对距袋口1m范围内的压力影响很小,对中下游的峰值压力影响较大,当滤袋长度由6m增加到9m时,下游峰值压力由8kPa下降到2kPa。将YTALS-03-60型袋式除尘器滤袋加长至8m后进行数值模拟,结果表明流场分布不均匀,各列滤袋的流量分配系数相差很大,清灰前后A列、P列滤袋的流量分配系数分别为1.42、1.14和1.21、1.62,清灰前后的最大不均匀系数分别为0.61、0.75;靠近箱体壁面处的流速大于滤袋矩阵中心的速度,远离进口区域的流速大于进口区域流速,进气口的射流对滤袋底部形成直接喷吹。对原模型袋式除尘器进行增加挡风板的改造后重新建模计算,得出挡风板高度为1m、2m时气流分布要好于原模型,清灰前后的最大不均匀系数分别为0.47、0.57和0.52、0.78;进气口对滤袋底部的直接喷吹被消除,但在进风口下侧形成了涡流,不利于粉尘的沉降。改变挡风板横向尺寸,当挡风板高度为3m时,清灰前后的最大不均匀系数达到最小,为0.37、0.35,除清灰前A列滤袋、清灰后P列滤袋不满足平衡要求外,其余滤袋都能满足;改变灰斗与中箱体的连接位置后,进风口下侧的涡流被消除;挡风板对除尘器内部流场的影响很大,增加挡风板后流场较原模型有很大改善。
[Abstract]:In the background of severe air pollution, the emission standards of various industries are becoming more and more strict, while the long-bag pulse bag filter can easily adapt to the new standards, and its application is becoming more and more extensive. In order to improve the overall efficiency and service life of the equipment, it is necessary to further study the bag dust collector, especially the ash removal system and the flow field distribution. At present, it is difficult to measure the complex gas-solid two-phase flow field in the dust collector, and the CFD numerical simulation method can get the internal flow in the process of soot cleaning and dust removal, which can provide some basis for the improvement of the bag dust collector. The ash removal effect is an important factor to influence the normal operation of the dust collector, and the airflow distribution in the middle box has a great influence on the life of the dust collector. In this paper, the 1:1 geometric model of the injection area and the whole dust collector is established by using the ICEM mesh division software, and the structured grid is divided. The pressure distribution and air flow distribution in the process of soot cleaning by pulse injection were simulated and analyzed by computational fluid dynamics (CFD) method. The rationality of numerical simulation is verified by comparing the simulation results of pulse injection process with experimental data. The effects of Venturi tube, injection pressure and filter bag length on the pressure distribution on the wall of the filter bag are simulated and analyzed. The results show that Venturi tube has great influence on the peak pressure of filter bag wall. Under the same injection conditions, the maximum peak pressure on the filter bag wall was reduced from 16.9kPa to 15.7 KPA, and the peak position of the filter bag decreased by 0.5 m, the peak pressure of the middle and lower reaches of the filter bag decreased from 7.5kPa to 5.4 KPA, and the peak pressure of the filter bag decreased by 28%. The peak pressure at every position of the bag wall has a great influence on it. When the injection pressure is 0.35MPa, the peak pressure is 18.5 KPA, the downstream pressure is 8 KPA, and the injection pressure is 0.2MPa. The peak pressure was 13.7 KPA, the downstream pressure was 3.8 KPA, the maximum peak pressure and downstream peak pressure were reduced by 26% and 53%, respectively. Under the same injection conditions, the filter bag length had little effect on the pressure within 1m distance from the pocket mouth, but had a great effect on the peak pressure in the middle and lower reaches. When the filter bag length increased from 6 m to 9 m, the downstream peak pressure decreased from 8kPa to 2 KPA. After the filter bag of YTALS-03-60 bag filter is extended to 8 m, the numerical simulation results show that the flow field is not uniform, and the flow distribution coefficient of each filter bag is very different. Before and after ash cleaning, the flow distribution coefficients of A column P filter bags were 1.42U 1.14 and 1.21g 1.62, respectively, and the maximum non-uniform coefficients before and after ash cleaning were 0.61m 0.75, respectively. The velocity near the wall of the box was greater than that at the center of the filter bag matrix. The velocity far away from the inlet area is larger than the inlet velocity, and the jet from the inlet directly injects the bottom of the filter bag. After the retrofitting of the original model bag dust collector with the addition of the windshield, it is obtained that the airflow distribution is better than that of the original model when the height of the windshield is 1 m ~ 2 m. The maximum inhomogeneity coefficient before and after cleaning is 0.47U 0.57 and 0.52U 0.78.The direct injection of air inlet to the bottom of the filter bag is eliminated, but vortex is formed at the lower side of the inlet, which is not conducive to dust deposition. When the height of the baffle is 3 m, the maximum non-uniform coefficient before and after cleaning reaches the minimum, which is 0.37 ~ 0.35. Except for the A-column filter bag before ash cleaning and the P row filter bag after ash cleaning, all the other filter bags can be satisfied. The vortex at the lower side of the inlet is eliminated by changing the connecting position of the ash bucket and the middle box, and the influence of the windshield on the internal flow field of the dust collector is great, and the flow field after the increase of the baffle is greatly improved than that of the original model.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X701.2

【参考文献】