- 學位論文
高溫固定床中探討二氧化碳對氧化鈣與氯化氫之反應性研究
The Effect of CO2 on the Reactivity between CaO and HCl in a Fixed-Bed Reactor at High Temperature
摘要
近年來環保意識抬頭，政府訂定垃圾強制分類、廚餘回收等相關之法規，雖有效地減少含氯物質進入焚化爐的量，但其造成環境問題仍不容小覷。而高溫下含氯物質經熱處理，如：廢棄物衍生燃料(refuse derived fuel, RDF)、都市固體廢棄物(municipal solid waste, MSW)、廚餘(leftovers)等，過程中會產生氯化氫。氯化氫極易溶於水，並與煙氣中凝結下來的水汽結合生成鹽酸，進而腐蝕鋼材設備，若未經處理即排放則對於環境有相當的影響。 氯化氫可藉由鈣基吸附劑(如:氫氧化鈣、碳酸鈣或氧化鈣)於煙氣中進行中和反應。而鈣基吸附劑亦常用於焚化系統中，藉以去除煙氣中其他酸性氣體，如：氟化氫、二氧化硫等。部分文獻指出，煙氣中的氣體組成，如:二氧化硫、水汽以及二氧化碳等，對氧化鈣吸附氯化氫之效率有明顯之影響。然而，煙氣中的氣體組成對於氧化鈣吸附氯化氫之影響的相關研究仍是相當稀少。 鑑於此，本研究主要目的為探討煙氣中二氧化碳對於氧化鈣吸附氯化氫(1000 ppm)之反應性的影響，並藉由即時監測反應器出口氯化氫濃度以得到吸附劑之總轉化率。為了研究二氧化碳對氧化鈣吸附氯化氫之反應性的影響，本研究回顧相關文獻及理論並結合流體化床燃燒爐之操作特性下，將實驗設計及流程分為兩大部分。根據本研究之實驗設計，第一部分為探討二氧化碳對於吸附劑的性質及反應之影響，實驗參數為溫度(500-800℃)及濃度(4-12%)；而另一部分則為探討煙氣中二氧化碳對氧化鈣吸附氯化氫之影響，實驗參數則依據第一部分的實驗結果及流體化床的操作特性下做實驗參數之擬定。 研究結果顯示，500-650℃的溫度下煙氣中二氧化碳濃度(4-12%)皆對氧化鈣造成明顯的碳酸化現象，且隨著濃度提高則碳酸化反應速率也越迅速。對於氧化鈣氯化反應方面，煙氣中二氧化碳氣體的存在會提高吸附劑之轉化率，但隨著濃度的提高，轉化率則會越低。
並列摘要
The incineration of waste containing chlorine (such as refuse derived fuel, municipal solid waste, leftovers) at high temperature will generate hydrogen chloride (HCl) and corrode the apparatus. Hydrogen chloride can be neutralized by the reaction with calcium-based sorbents (such as solid lime, limestone, and calcium oxide). Ca-based sorbents were usually used in incineration process to remove acid gas in the flue gas such as hydrogen chloride and sulfur dioxide. However, some literature pointed out the flue gas composition (such as SO2, H2O, CO2) influenced the efficiency of HCl absorption by CaO. For this reason, the purpose of this present was to investigate the influence of CO2 for the reaction behavior of calcium oxide and hydrogen chloride (1000ppm) and to monitor the outlet concentration of HCl immediately so as to calculate the conversion of CaO. In order to investigate into the effect of CO2 on the reactivity of CaO, the experimental design was divided into two parts: (1) carbonation reaction for CaO in CO2 atmosphere under 4-12% CO2 in temperature range of 500-800℃, (2) the influence of CO2 for the reactivity of HCl absorption by CaO and the experiment parameter will be decided by comparing the results of carbonation reaction of CaO and the operating characteristics of fluidized bed combustor. The results in this experiment show that the carbonation reaction of CaO is obvious in the presence of 4-12% CO2 in N2 at 500-700℃. With higher CO2 concentration, the higher the reaction rate of carbonation. The results also show that the conversion and reaction rate of CaO was markedly promoted in the presence of CO2 in the simulated flue gas at 650℃. But with higher CO2 concentration, the lower reaction extent of sorbents that was achieved.