膠結特性對靜電集塵器收集效率影響之研究

The Characteristics of Agglomeration to Collection Efficiency of Electrostatic Precipitator

連振廷(Chen-Ting Lien)

指導教授 ： 林文印

國立臺北科技大學/工程學院/環境工程與管理研究所/碩士(2010年)

摘要

一般性能佳的靜電集塵器對質量收集效率可高達99%，但對於次微米（0.1-1.0μm）粒徑其微粒穿透效率明顯的較高。而大量次微米微粒排放到大氣中會對環境造成一些負面影響。因此改善靜電集塵器對次微米微粒收集效率是一個重要的議題。利用靜電膠結技術可讓帶電微粒於交流電場下，使微小微粒碰撞膠結成較大粒子，因而提升微粒收集效率。
因此，本研究設置一套靜電膠結系統以氯化鈉（Sodium chloride, NaCl）為測試氣膠，改變操作參數以靜電膠結系統使小微粒形成具有電性之大微粒，改變之參數為交流電之電壓、頻率與停留時間，以探討不同參數對懸浮微粒之靜電膠結、集塵效率及臭氧產生量之影響。
研究結果顯示，於膠結區中微粒數目中位數粒徑、數目平均數粒徑及數目幾何平均粒徑隨操作電壓增加、頻率減少及膠結區平板長度越長而上升。於相同頻率30 Hz與操作電壓16 kV下，當停留時間從4.5 s增加到7 s時，次微米微粒膠結效率從9.84%增加到11.39%。且以整體之微粒穿透率來看，當頻率為30Hz停留時間7秒時，電壓從8 kV增加至16 kV後微粒之次微米穿透率從24.12%下降5.50%。由結果所示，靜電膠結系統設置對次微米微粒去除效率有明顯的提升。
此外本實驗系統中，臭氧產生量主要受充電區之電暈放電產生之電流值影響，其總臭氧產生量約為140 ppb。除此之外，微粒帶電量隨著電壓及微粒粒徑增加而增加，而當微粒小於50 nm時，平均帶電量小於1.6×10-19 coulomb，意味部份粒徑的微粒並沒有帶電，且隨著粒徑越小其比例越高。

關鍵字

靜電集塵器 ； 靜電膠結 ； 懸浮微粒

並列摘要

The total mass collection efficiency of modern well-designed ESP can be as high as 99 %. But for submicron particles its, collection efficiency may be much lower. Such particles emitted into the atmosphere may cause environmental pollution. Therefore, it is necessary to improve the collection efficiency of ESP for submicron particles. In an alternating electric field, different velocity and amplitude of the particles result in collisions. The particles collided with each other result in the small particle grown large one. The large particles are easily removed by electrostatic precipitator.
A combination of electrostatic agglomerate device and ESP was set up in this study. The objectives of this researched include studying the agglomerate characteristics, collection efficiency and ozone concentration of ESP by using alternating electric field.
The experimental results indicated that count median diameter, count mean diameter and geometric mean diameter increased as increasing voltage, decreasing frequency of alternating electric field, and increasing the length of agglomerator. When applied voltage was 16 kV and the frequency was 30 Hz, the submicron agglomeration efficiency was 9.84% and 11.39% for 4.5 and 7 seconds of residence time, respectively. When applied voltage raised from 8 kV to 16 kV, the submicron penetration through the ESP reduced from about 24.12% to 5.50% at frequency 30 Hz and residence time 7 seconds. These results showed that a significant reduction in submicron particle emissions after the electrostatic agglomerator applied.
The ozone concentration was about 140 ppb mainly resulted from the operation of charger. Besides, the particle charge was calculated by using Deutsch-Anderson Equation and terminal electrostatic velocity equation. The particle charge increased exponentially with increasing particle diameter. When the particle size was less than 50nm, the average particle charge was less than unit electron charge because some did not get charge.

並列關鍵字

Electrostatic precipitator ； Agglomerate ； Suspended particles

參考文獻

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