有效去除微粒污染物的濕式靜電集塵器

Abstract

本研究設計一個有效的wire-in-plate濕式靜電集塵器，用於控制半導體製程排放之奈米、次微米以及微米級微粒。濕式靜電集塵器使用-15 kV之高壓電產生電場，同時使線徑為0.36 mm之鎢絲放電電極產生電暈放出離子。濕式靜電集塵器前端有一核凝成長腔，當中之常溫細水霧用來將高溫廢氣急速冷卻，以加強奈米微粒的凝結成長，並促使奈米微粒之收集效率提升。實驗結果顯示，沒有細水霧時奈米微粒之收集效率為67.9 – 92.9 %，當核凝成長腔中有細水霧時，奈米微粒之收集效率被大大的提升到99.2 – 99.7 %。 在濕式靜電集塵器中，間歇式的洗滌水用來維持集塵板以及放電電極線之清潔。在沒有水洗的實驗中，靜電集塵器操作20 min後效率已降到小於21 %。在有間歇水洗的實驗中，靜電集塵器連續操作6小時微粒之收集效率仍高達93.1 – 96.9 %。實驗證實間歇式的洗滌水確實可以維持集塵板以及放電電極線之清潔。因此，使得本研究之靜電集塵器在長時間使用時仍可以保持在高的收集效率。 實廠長時間測試在A及B兩個半導體廠進行，本研究之濕式靜電集塵器分別連續運轉35及22天，其總平均之微粒收集效率則維持在98.7 %及97.3 %。由實廠測試可知，集塵板之洗滌水確實可以有效地清除集塵板以及放電電極線上之粉塵。而細水霧也可以確保本研究之濕式靜電集塵器，可以長期維持在高效率的運轉。 本研究建立了一個推估ESP集塵效率η (%)之模式，其方程式為 ,其中α、β及γ是迴歸係數，而N*De是Deutsch number。此模式計算之結果，與本研究及文獻之實驗值均相當地吻合。

An efficient wire-in-plate single-stage wet electrostatic precipitator (WESP) was designed and tested to control nanoparticles, submicron and micron-sized particles emitted from semiconductor manufacturing processes. Tungsten-wires of 0.36 mm in diameter were used as discharge electrodes and a fixed voltage of -15 kV was supplied to generate the electric field and corona ions. Fine water mist at room temperature was used to quench the high temperature exhaust gas to enhance particle condensation growth and improve the collection efficiency of nanoparticles. Experimental results showed that without fine water mist, nanoparticle collection efficiency was 67.9 – 92.9 %, which was greatly enhanced to 99.2 – 99.7 % when the WESP was operated with fine water mist. For longer term operation, the periodic wall-cleaning water was used to clean discharge electrodes and collection electrodes regularly. The collection efficiencies decreased substantially to less than 21.0 % when WESP was tested without wall-cleaning water after continuous operation for 20 min. With the application of wall-cleaning water, the collection efficiency of the WESP was measured to be 93.1 – 96.9 % after continuous operation for 6 hrs. Therefore, this laboratory loading test shows that a high collection efficiency of the present WESP can be maintained with the aid of periodic wall-cleaning water spray. In the field tests, the total collection efficiencies (40 ≤ dp ≤ 8100 nm) of the WESP were found to maintain greater than 98.7 and 97.3 % for continuous operation for 35 and 22 day at fab A and fab B, respectively. These field test results conclude that wall-cleaning water is able to maintain both discharge and collection electrodes clean and ensure that the present WESP with fine water mist can operate at a high particle removal efficiency for long-term. A predictive method was developed to calculate the particle collection efficiency equation η (%) in the form as , in which α, β and γ are regression coefficients and N*De is the modified Deutsch number. Good agreement was obtained between present predictions and experimental data.