脉冲喷吹滤筒除尘器的清灰响应机制及清灰机理研究

Recently, the use of pleated filter cartridges in dust collectors has attracted great attention because the pleated filter cartridges offer a larger filtration surface and a higher filtration efficiency compared to flat-sheet filter bags (if both filters are used in housing of the same size). However, cleaning way of pleated filter cartridges is more difficult compared to this of the flat-sheet filter bags because of the higher pleated ratios of the filter cartridges. The complexity of different stages and influencing factors makes it very difficult to investigate the dynamic process of dust cake dislodgement from the filter cartridge and influencing factors of cleaning efficiency during pulse-jet cleaning. Therefore, the cleaning response mechanisms and cleaning mechanisms of filter cartridges are required to investigate immediately. The whole processes are monitored during pulse-jet cleaning. The internal flow fields of filter cartridge are calculated using CFD software and the pressures on the filter cartridge are measured using the pressure transducers. The influence of pulse airflow on internal flow fields of filter cartridge is studied. Combined with the dynamic process of dust cake dislodgement from the filter cartridge using a high-speed camera, the cleaning response mechanism of cleaning stages is revealed to pulse airflow. The relativities of dust cake dislodgement from the filter cartridge, the pressure-varied process as time, pressure distribution over the full height of filter cartridge and dust residues of the filter cartridges are investigated. The influencing factors of dust residues of the filter cartridges and systematic pressure drops are discussed. The influencing factors of cleaning efficiency and cleaning mechanism are revealed. This research can provide a theoretical basis for the use of applications and a long time operation of filter cartridges.

滤筒除尘器比袋式除尘器在相同的箱体结构内具有更大的过滤面积与更高的过滤精度而受到广泛的关注，而滤筒清灰问题是限制其广泛应用的瓶颈。脉冲喷吹滤筒清灰影响因素与清灰各个阶段交错发生，脉冲气流瞬间非稳态喷吹引起粉尘从滤筒上剥落的动态过程及清灰影响因素尚不明确，因此迫切需要对脉冲气流与滤筒相互作用发生的清灰响应机制及清灰机理进行研究。本项目通过调节脉冲喷吹清灰影响因素实施整个过程监控，采用数值计算滤筒内部流场与测试滤筒侧壁压力研究脉冲气流对滤筒流场变化的影响，结合高速摄影仪记录粉尘从滤筒上剥落的动态过程，探讨滤筒清灰过程对脉冲气流的响应机制。进而对比研究粉尘从滤筒上剥落的动态过程、滤筒侧壁压力随时间的变化过程、滤筒侧壁压力在滤筒长度方向上的变化与粉尘残留量的关系，探讨影响粉尘残留量及系统压力降变化的主要贡献因素，揭示滤筒清灰效果贡献的主要因素及机理，为滤筒除尘器广泛应用与长期稳定运行提供科学依据。

滤筒除尘器比袋式除尘器在相同的箱体结构内具有更大的过滤面积与更高的过滤精度而受到广泛的关注，而滤筒清灰问题是限制其广泛应用的瓶颈。本项目建立脉冲喷吹性能实验台，以滤筒为研究对象，首先对滤筒侧壁压力测定，对比研究了操作参数和工况参数不同下滤筒侧壁压力的变化，滤筒侧壁压力峰值是评价滤筒清灰效果的重要参数，建立了喷吹距离S与喷吹孔径d的函数关系S=(D-d)/2 tan〖(22.433-0.8675d+0.1089d^2)/2〗，同时，针对脉冲喷吹的孔管截面积比，采用侧壁压力和加速度作为清灰性能指标，得到最优的孔管截面积比为38.72%。通过滤筒侧壁压力峰值变化过程得出：喷吹距离50mm，诱导喷嘴孔径为16mm时，滤筒从上到下五个测点的压力峰值分别为3793、12235、3720、6619和1131Pa，滤筒从上到下的压力峰值合理，诱导喷嘴解决了上部不完全清灰的问题。过滤风速在0.4m/min以下时，滤筒底部侧壁压力峰值很小，过滤风速在0.4m/min以上时，滤筒底部侧壁压力峰值在增大，过滤风速的变化会改变滤筒下部的侧壁压力峰值。其次通过高速摄影仪拍摄滤筒清灰的动态过程，揭示滤筒清灰动态过程与脉冲气流变化的关系，滤筒清灰过程从有粉尘开始剥落到整个粉尘从滤筒上脱落需要372ms。通过滤筒侧壁压力峰值测试结果与粉尘从滤筒上剥落的过程的实验研究，滤筒的侧壁压力峰值及持续时间与粉尘从滤筒上剥落的过程一致，滤筒清灰主要是侧壁压力峰值及其对滤料持续冲击作用，因此，滤筒的侧壁压力峰值及持续时间评价滤筒清灰效果的主要机制。基于滤筒清灰动态过程和滤筒侧壁压力变化过程的实验结果，对比分析了滤筒与滤袋清灰的动态变化过程及压力峰值与清灰效果的规律，并结合实验室研究的结果与滤筒工业生产使用中的差异性，验证了对滤筒清灰效果贡献的主要是滤筒侧壁压力峰值及其持续时间，建立了粉尘残余量与侧壁压力峰值的关系，在过滤风速为0.6，0.8和1m/min时，粉尘残余量与侧壁压力峰值的关系分别为：y=1.0715e^(-0.0004x)，y=1.4043e^(-0.0005x)，y=1.5476e^(-0.0005x)。此项目完成为滤筒除尘器广泛应用与长期稳定运行提供科学依据。