陳志傑2006-07-252018-06-292006-07-252018-06-292005-07-31http://ntur.lib.ntu.edu.tw//handle/246246/4917無論從理論或是實驗中均可以發現在某些情況之下，粒徑小的微粒，尤其是粒徑 小於1 µm 的微粒，常會有充電不足的現象。不帶電的微粒在電場中並不會受到庫侖 力的作用而被收集，以致於當微粒小至某一程度之後，靜電集塵器的收集效率反而會 有下降趨勢。換句話說，從質量濃度的觀點，靜電集塵器雖然有相當高的效率，不過 卻無法有效地收集奈米粒徑的微粒。本實驗的目的即在於尋找適合的海綿濾材，以期 有效收集從靜電集塵器脫逃的奈米微粒。實驗中使用定流量噴霧器(Constant Output Atomizer)產生粒徑100 ∼7nm 的固體測試微粒並利用掃瞄式電移動度微粒分徑儀 (Scanning Mobility Particle Sizer, Model 3085)分別量測海綿及靜電集塵器上、下游 的微粒濃度與分佈，藉此探討海綿濾材對於奈米微粒的收集效率如何受到孔隙度、表面風速及填充密度等條件所影響。實驗的結果顯示，在相同厚度與相同填充密度的條件下，由於較大孔隙度的海綿 具有較小的纖維直徑，較多的纖維表面積，微粒的穿透率會隨海綿孔隙度的增加而降 低(15nm 的微粒在60ppi 海綿其穿透率為62 ％，而隨著孔隙度增加為100ppi 穿透率 減少至9 ％)。另外，由於停留在海綿濾材時間長短不同，因此奈米微粒對於海綿的穿 透率會隨著表面風速的減小而降低(15nm 的微粒表面風速由9.5cm/s 增加至66cm/s 時，所得到穿透率由10.5 ％上升至62.5 ％)。海綿填充密度的影響與孔隙度類似，較 高填充密度意味著有較多濾材表面積因此填充密度越大其奈米微粒穿透率越小。從研 究中可發現，低孔隙度、低填充密度且低過濾風速可以得到較高的過濾品質。在實驗 中靜電集塵器處理風量設計為100 L/min 。微粒粒徑小於最易穿透粒徑(大約0.3 µ洩 其穿透率隨著粒徑減少而降低。不過在15 nm（穿透率為19 ％）以下，微粒因為部分 充電的原因使得微粒穿透率上升。利用海綿濾材(110 ppi ，填充密度 0.04 ，厚度 25.4 mm)串接於靜電集塵器之後可以有效控制奈米微粒(穿透率由 19%%降低至 2.5%)。由於靜電集塵器所造成的壓降幾乎可以忽略，即使奈米微粒經過靜電集塵器 時有部分充電而無法完全收集的情形，從過濾品質而言靜電集塵器仍是優於海綿濾材。Due to the partial charging effect, the collection efficiency of an ESP tends to decrease with decreasing particle size. In other words, the collection efficiencies in terms of number density for nanoparticles of an ESP may be relatively low, although high mass collection efficiency is well achieved by a conventional ESP. The main objective of this study was to search the right types of filter foams that could efficiently collect those fugitive uncharged nanoparticles. In order to conduct the aerosol penetration tests of filter foams, a constant-output aerosol atomizer was used to generate challenge aerosol particles in the size range of 7 to 100 nm. A scanning mobility particle sizer (SMPS 3085) was used to measure the aerosol concentrations upstream and downstream of the ESP unit and/or the filter foams. Among the operation parameters were the foam porosity, foam solidity, foam thickness and filtration velocity. The results showed that aerosol penetration through filter foams decreased with increasing foam porosity, apparently due the more surface area for aerosol deposition by diffusion. Aerosol penetration increased with increasing filtration velocity due to shorter retention time. The effect of foam packing density on aerosol penetration was very similar to foam porosity (fiber diameter) because higher packing density means more filter materials and therefore, more surface area for aerosol deposition. To take into account the air resistance together with aerosol penetration, we found that low porosity, low packing and low filtration velocity resulted in higher filter quality factor. The ESP unit tested in this work had a designed flow rate of 100 L/min. For particles smaller than the most penetrating size (about 0.3 µm), the aerosol penetration through ESP decreased with decreasing aerosol size until the size reached about 15 nm (19%). Aerosol penetration of particles smaller than 15 nm increased due to partial charging. Filter foam (110 ppi, packing density of 0.04 and thickness of 25.4 mm) removed most of the fugitive ESP nanoparticles (penetration from 19% down to 2.5%). The air resistance induced by the ESP was almost negligible. Therefore, ESP is superior to the filter foams from the perspective of filter quality, even for small particles with partial charging effect.zh-TW國立臺灣大學公共衛生學院職業醫學與工業衛生研究所過濾奈米微粒海綿濾材穿透率FiltrationNanoparticlesFilter foamsreport