| 摘要: | 焚化法對於揮發性有機廢氣的處理，在眾多的空氣污染防制手段是目前處理效率最高的程序。為節省燃料的之故而發展出的蓄熱式焚化法，藉由閥件切換將VOCs導入焚化爐內，而造成部份VOCs洩漏，其中又以兩塔型蓄熱式焚化爐因切換閥件作動而造成處理效率下降的問題最嚴重，本研究以設置緩衝模組進行兩塔型RTO處理效率的提升。其設計的構想是在蓄熱塔的切換閥件作動以前，將脫附風機途經焚化爐爐膛的空間充滿乾淨的外氣。雖然洩漏現象依然會發生，但經過切換程序而洩漏的並非高濃度的VOCs而是乾淨的外氣，因此可避免焚化爐系統的總處理效率降低的狀況發生。本研究選擇兩套RTO設備，其中RTO#A的設計處理風量為166.3 CMM，RTO#B的設計處理風量為87.2 CMM。兩套RTO系統經過質量平衡計算後得到焚化爐系統入口、沸石濃縮轉輪出口和焚化爐出口等質量流率，再以質量流率進行處理效率的計算，以此還原系統的真實處理效率。設置緩衝模組前RTO#A系統於切換閥件作動時的處理效率會降低至72.66%，設置緩衝模組後RTO#A系統於切換閥件作動時處理效率提升至91.59%，RTO#A爐體進出口的平均排放量則降低0.3 kg/hr。本研究也另外探討緩衝模組設計錯誤的案例RTO#B，導致設置緩衝模組後未如RTO#A的設置結果般所預期的效果，其中RTO#B在切換閥件作動期間的處理效率，也與RTO#A未設置緩衝模組時的效率接近。此外，RTO#B因設計錯誤而引入過多的外氣，相當於三塔型RTO引入外氣進行掃氣程序的2倍，使得耗能問題加劇。在兩種爐型的製造成本比較方面，兩塔型RTO的成本較三塔型RTO低約70萬餘元，若加入緩衝模組設置費用約45萬餘元，整體製造成本則不如預期的低廉。對於污染源在新建設備的考量，建議設置三塔型或旋轉型RTO，避免後續改善工程增加額外的施作時間。;Thermal oxidation is one of the most effective processes for the treatment of VOC-containing gas stream. Especially, regenerative thermal oxidizer (RTO) has been developed to reduce energy consumption. For the operation of RTO, the VOC removal efficiency achieved with two-canister RTO is greatly reduced during valve switching. In this research, buffering module is applied to improve the VOC removal efficiency achieved with two-canister RTO. The concept is to fill the volume between the desorbing fan and the RTO with clean air prior to valve switching. Although leakage may still occur, high-concentration VOCs is not leaked. Because clean air is purged through the switching process, overall VOC removal efficiency achieved with the RTO system can be maintained. In this study, two facilities equipped with two-canister RTO were selected for investigation. The capacity of RTO#A was 166.3 CMM as designed, while the capacity of RTO#B was 87.2 CMM. Mass balance of the RTO system is performed to get the mass flow rates at the RTO system inlet, the zeolite concentrator outlet and the RTO outlet, respectively. The removal efficiency was calculated on the basis of the mass flow rate to restore the true removal efficiency of the system. Before the buffering module was installed, the overall removal efficiency of VOC achieved with RTO#A was 72.66%. After the installation of buffering module, the removal efficiency of VOCs achieved with the RTO#A system was increased to 91.59%. The mass flow rate of VOCs emitted from RTO#A was reduced to 0.3 kg/hr. The case of RTO#B was also investigated and it was a wrong design. The effectiveness of the buffering module is not as expected as the result of RTO#A. The VOCs removal efficiency achieved with RTO#B decreases during the actuation of the valve switching process, which is similar to the RTO#A before buffering module was installed. In addition, RTO#B also leads to too much air due to improper design and it, is equivalent to double of purge air in the three-canister RTO to perform the purge process. It aggravates the energy consumption problem. Regarding the manufacturing cost, the cost of the two-canister RTO is about NT$700,000, which is less expensive than the three-canister RTO. If the buffering module is added, the extra cost is about NT$450,000. The overall manufacturing cost is not as low as expected. Thus, three-canister RTO or rotary-type RTO is recommended for the new facility when considering RTO as the option for VOC removal to avoid additional cost and implementation time for subsequent improvement. |
