DEVELOPMENT OF ECONOMICAL AIR FILTERS WITH HIGH COLLECTION PERFORMANCE.

随着高科技行业对高净化空间的需求不断增加，ULPA（超低渗透空气）过滤器已取代传统的HEPA（高效微粒空气）过滤器用于洁净室。此外，在半导体工业中，膜过滤器的收集效率远高于ULPA和HEPA，目前用于消除加压工艺气体中的颗粒物。在这种情况下，对这些空气过滤器的下一个要求是在不牺牲其高收集效率的情况下降低其压降。本文引入颗粒穿透率与压降的对数之比作为过滤器性能指标，综合考虑过滤器的收集效率和压降，评价各种空气过滤器的收集性能。在过滤性能指标的基础上，研究了纤维过滤器和膜过滤器的过滤结构对收集性能的影响。此外，对利用静电电荷收集微粒的驻极体过滤器的收集性能进行了评价，以检验其是否可以作为一种经济的高收集性能空气过滤器。结果表明：(1)减小纤维直径，(2)增加与气流方向平行的纤维比例，(3)减少粘结剂用量，可以提高纤维式空气过滤器的集尘性能。对于膜过滤器，我们根据其结构将其分为五类，发现纤维状结构的膜过滤器比孔状结构的膜过滤器具有更高的收集性能。在此基础上，提出了一种基于内流收集模型的新模型，预测了较高填料密度下膜过滤器的收集效率。针对驻极体过滤器的收集性能，提出了计算初始收集效率的理论模型，实验结果表明，在潮湿空气中，纤维上的驻极体电荷是稳定的，对固体颗粒和大气颗粒的收集效率不随粉尘负荷的增加而降低。然而，当使用驻极体过滤器过滤有机雾粒子时，电荷在短时间内被中和，导致收集效率显著降低。少

With increasing demand for highly-purified space in high-tech industry, ULPA (Ultra low Penetration Air) filters have been used in clean rooms in place of the conventional HEPA (High Efficiency Particulate Air) filters. Further, in semiconductor industry, membrane filters which have collection efficiency much higher than the ULPA and HEPA are currently used to eliminate particulate matter from pressurized process gases.Under these present situations, the next requirement for these air filters is to reduce their pressure drop without sacrificing their high collection efficiency.In the present work, an index for filter performance, defined as the ratio of logarithm of particle penetration to pressure drop was introduced to evaluate collection performance of various air filters by taking account of both the filter collection efficiency and the pressure drop. On the basis of the filter performance index, the influence of filter structure of fibrous and membrane filters on the collection pe … More rformance was investigated. Furthermore, the collection performance of electret filter which utilizes electrostatic Charge to collect particles was evaluated in order to examine whether it can be used as an economical high collection performance air filter.As a result, it was found that the collection performance of fibrous air filter can be improved (1) by reducing the fiber diameter, (2) by increasing the fraction of fibers which lie parallel to airflow direction, and (3) by reducing the amount of binder. Concerning the membrane filters, we classified them into five groups according to their structure, and found that the membrane filters with fiber-like structure have a higher collection performance than those with pore-like structure. Further, the collection efficiency of membrane filters with a relatively high-packing density was predicted by a newly proposed model based on internal flow collection model. Concerning the collection performance of electret filters, we presented a theoretical model to calculate initial collection efficiency, and experimentally showed that the electret charge on the elect fiber is stable in humid air and that the collection efficiency for solid and atmospheric particles do not decrease with dust load. However, when the electret filter was used for organic mist particles, the charge was neutralized in a short time, leading to a significant decrease in the collection efficiency. Less