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  • 學位論文

奈米微粒穿透海綿濾材與旋風分離器特性研究

Nanoparticle Filtration Characteristics of Foams and Cyclones

指導教授 : 陳志傑

摘要


無論從理論或實驗中均可發現: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,在靜電集塵器之中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100-7 nm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、填充密度之下,孔隙度較大的海綿具有較小的纖維直徑,較多的纖維表面積,奈米微粒的穿透率會隨海綿孔隙度的增加而降低 (15 nm的微粒在60 ppi海綿其穿透率為62 %,且隨著孔隙度增加為100 ppi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 (15 nm的微粒表面風速由9.5 cm/s增加至66 cm/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,因此填充密度愈大其奈米微粒穿透率愈小。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

並列摘要


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 shorter interstitial distance and the more surface area for aerosol deposition by diffusion. Aerosol penetration increased with increasing filtration velocity due to shorter retention time within the filter foam. 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

並列關鍵字

nanoparticles filtration cyclone filter foams

參考文獻


Hinds, W.C.: Aerosol Technology, New York, John Wiley and Sons Inc. pp. 182 – 205 (1999).
Huang, S.H. and Chen, C.C.: Ultrafine Aerosol Penetrate through Electrostatic Precipitators. Environ. Sci. Technol. Vol. 36, pp. 4625 – 4632 (2002).
Huang, S.H. and Chen, C.C.: Filtration Characteristics of a Miniature Electrostatic Precipitator. Aerosol Sci. Technol. Vol. 35, pp. 792 – 804 (2001).
Ichitsubo, H.; Hashimoto, T.; Alonso, M.; Kousaka, Y.: Penetration of Ultrafine Particles and Ion Clusters through Wire Screens. Aerosol Sci. Technol. Vol. 24, pp. 119 – 127 (1996).
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被引用紀錄


黃志宏(2015)。旋風集塵器氣流流場模擬與碳化矽微粒特徵分析〔博士論文,國立屏東科技大學〕。華藝線上圖書館。https://doi.org/10.6346%2fNPUST.2015.00254

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