經異相核凝增長去除次微米微粒之文氏洗滌器之研究

Abstract

本研究擬利用高溫飽和蒸氣混合常溫廢氣（含有氯化鈉微粒）使次微米微粒產生異相核凝增長，再以文氏洗滌器去除增長後之微粒，藉以提高去除效率，並考量總能量的消耗，以期此法經濟實用。 在傳統文氏洗滌器的實驗中，對應最低去除效率的粒徑約為20nm，在400lpm、2.5l/m3的操作條件下其去除效率僅約20%，但仍比理論預測來得大，顯示理論模式仍有不足之處；而在經核凝成長後，20nm的微粒在200lpm、2.5l/m3的操作條件下即可提升至62∼71%，整條效率曲線更是在60∼90%之間，效率已大幅提升，而此時的壓降僅9.3in.H2O左右。 針對低質量混合比0.0046的情況模擬，預測去除效率亦能在55%以上，且此時無廢熱產生，整體的耗能也比傳統文氏洗滌器低，若能有效提升蒸氣與廢氣的混合，此法將能應用於實際處理上。

A Venturi scrubber to remove submicron particles in the exhaust is investigated in this study. Using high temperature and saturated steam to mix with normal temperature gas, which was composed of NaCl particles, those submicron particles would grow in particle diameter by heterogeneous nucleation, so removal of submicron particles is possible. In the traditional experiment of Venturi scrubber (without adding steam), the particle diameter for lowest removal efficiency is about 20nm, where the efficiency is only about 20% in the operating condition for the flowrate of normal temperature gas and the liquid to gas ratio are 400 lpm and 2.5 l/m3, respectively. However, the removal efficiency is greater than theoretical prediction. When particles grow by heterogeneous nucleation, the removal efficiency of 20nm particles is promoted to the range of 62% to 71% in the operating condition of 200 lpm and 2.5 l/m3. In this study, the removal efficiency is between 60% to 90%, and the pressure drop is only 9.3 in. H2O. The removal efficiency is above 55% for the computer simulation of mixing ratio is as low as 0.0046. In this simulation, total energy consumed is used to heterogeneous nucleation of submicron NaCl particles, so there is no waste heat generated. This method can be applied to remove submicron particles for industrial application after improving the mixing for saturated steam and exhaust.