活性炭颗粒对超细颗粒物的过滤性能

UFPs(超细颗粒物)对人体危害较大且难以脱除,但活性炭颗粒床利用多孔结构可以提高其过滤效率. 为探究试验条件对UFPs过滤效率的影响以及活性炭孔隙结构和UFPs过滤效率之间的关系,以实验室发生UFPs为研究对象,活性炭为过滤介质,对活性炭颗粒粒径、滤层厚度以及表观风速等条件对过滤UFPs的影响进行了研究,并通过对比过滤前后活性炭的孔径分布,分析活性炭多孔性与UFPs的关系. 结果表明:当活性炭颗粒平均粒径由2.50 mm减至0.45 mm、滤层厚度由20 mm增至100 mm、表观过滤风速由4.25 cm/s降至0.84 cm/s时,总过滤效率分别由41.87%、49.39%、68.24%升至86.27%、89.29%、83.04%；但从活性炭的单颗粒过滤效率和过滤质量角度来看,在活性炭颗粒粒径大、滤层厚度小、表观过滤风速低的条件下,更有利于单个活性炭颗粒的过滤作用的发挥；当UFPs粒径小于14.3 nm时,UFPs发生“热反弹”效应,并且主要过滤机理是扩散效应,但随着UFPs粒径增大,拦截和惯性碰撞对过滤效率的作用增强；活性炭500 nm以下的孔隙结构对脱除UFPs起着重要作用. 研究显示,选择含有更多500 nm以下孔隙的多孔材料更有利于过滤UFPs. 

Filtration Performance on Ultrafine Particles of Activated Carbon Granules

Abstract: Ultrafine particles (UFPs) can result in serious damage to human health, and they cannot be easily removed from the atmospheric environment. A granular bed filter with activated carbon granules (ACs) can observably improve the filtration efficiency of UFPs removal due to their porosity. In order to study the relationship of pore size distribution of ACs and experimental conditions with the purification efficiency of UFPs removal, ACs were used as filtration materials, and the effects of granular size, bed thickness and superficial velocity on the removal efficiency were investigated in detail in this study. The experimental results showed that the average filtration efficiency could be enhanced from 41.87% to 86.27%, from 68.24% to 83.04% and from 49.39% to 89.29%, when the ACs sizes decreased from 2.50 mm to 0.45 mm, the superficial velocity decreased from 4.25 cm/s to 0.84 cm/s, and the filtration bed thickness increased from 20 mm to 100 mm. Moreover, a single ACs particle worked more robustly with bigger ACs, less thickness and lower velocity. There was thermal bounce when the particle size was smaller than 14.3 nm, which was mainly a result of the diffusion effect. However, the interception and inertial impaction played larger roles in filtration efficiency when the size of UFPs increased. Furthermore, the purification of UFPs was greatly influenced by the ACs pores below 500 nm, therefore it is favorable for porous materials with more of these pores to collect UFPs.