奈米微粒的充電及靜電沈降效率的提昇

Abstract

奈米微粒的採樣及控制技術往往需要仰賴奈米微粒的帶電, 但是由於目前單極、單一電 極線-圓管型(unipolar single wire-in-tube)微粒充電器內部的微粒靜電損失很多，造成奈米 微粒的充電效率不高，因此如何提昇微粒充電器對奈米微粒的充電效率是一個重要的課 題。本計畫擬透過理論的模擬及實驗的印證, 設計一個新型的多電極線-圓管型微粒充電 器，本設計利用4 條放電電極線增加空氣離子的濃度, 以及利用接地電極圓管內壁上的 包覆空氣以減少帶電微粒的損失，藉以提昇奈米微粒的充電量及收集效率。另外由於放 電電極線附近有分散空氣，預期微粒將不容易附著在電極線上，因此可以延長充電器的 使用時間。乾式靜電集塵器有奈米微粒之去除效率不佳，粉塵負荷於收集板上會降低收 集效率，粉塵餅敲落時會有揚塵發生影響收集效率，高電阻係數粉塵容易產生背電暈， 以及黏著性粉塵及液滴微粒無法利用敲擊方法去除等多項問題，因此可解決這些問題的 濕式靜電集塵器是一個重要的設備。本計畫擬結合新型多電極線-圓管型微粒充電器與 平板型濕式靜電收集裝置作成雙級式濕式靜電集塵器，以提高奈米微粒的集塵效率，並 在實驗室完成高濃度微粒收集效率的測試, 及利用餐廳的油煙及高科技廠排放之高濃度 粉塵完成模廠實驗，以增進雙級式濕式靜電集塵器的實用性。

Sampling and control techniques of nanoparticles often require that nanoparticles are charged. However, nanoparticle charging efficiency is low for the unipolar, single wire-in-tube particle charger due to its severe internal particle electrostatic loss. Therefore, it is important to improve the charging efficiency of nanoparticles by using an efficient particle charger. Based on theoretical modeling and experimental validation, this project intends to develop a new multiple wires-in-tube particle charger, which makes use of 4 discharge wires to increase the ion concentration, and sheath air around the collector tube to avoid charged particle loss. The charger is expected to improve the amount of charges and charging efficiency of nanoparticles. In addition, there is dispersion air surrounding the wires such that particles do not deposit on the wires easily. Therefore, it is expected that the life time of the charger can be extended. Dry electrostatic precipitators have several problems such as low collection efficiency for nanoparticles, drop of collection efficiency as dust particles are loaded on the collector plates, influence of collection efficiency due to reentrainment of rapped dust cake, back corona generated by particles of high resistivity, removal of sticky dust and liquid particles by rapping is not possible. All these problems can be solved by wet electrostatic precipitators. This project intends to combine the new multiple wires-in-tube particle charger and the plate-type wet collector electrodes to make a two stage wet electrostatic precipitator to improve the collection efficiency of nanoparticles. Experimental study will be conducted in the laboratory to determine the collection efficiency using test particles of high concentration. Oily particles from the restaurants and high concentration dust particles from the high-tech companies will be used in the pilot testing of the two stage electrostatic precipitator to improve its applicability.