- 學位論文
高溫固定床中石灰吸附無水氯化氫反應動力學控制研究
A Study on Kinetic Control of CaO Adsorbing Dried HCl in a Fixed-Bed Reactor at High-Temperature
摘要
焚燒含氯物質過程中，如：都市垃圾焚化爐、廢棄物衍生燃料(Refuse Derived Fuel, RDF)鍋爐，所產生的氯化氫，對設備具有腐蝕現象。由於氯化氫的強氧化性，一般用於焚化爐、燃燒爐或鍋爐的設備，皆無法避免氯化氫的腐蝕，為了解爐內高溫去除氯化氫，本研究設計一高溫去除氯化氫之實驗。鈣基吸附劑常用於焚化系統中，藉以去除煙氣中的酸性氣體，如：氯化氫、二氧化硫等。本研究於小型固定床反應器中操作，探討氧化鈣與氯化氫的初期反應行為，並以未反應縮核模型分析實驗所得之實驗數據，由此方法計算氧化鈣與氯化氫於各溫度下之反應速率常數。反應溫度範圍是600-800℃，且本試驗之吸附劑平均粒徑分別為163及460μm。突破曲線為固定床反應器的重要指標之ㄧ，由突破曲線可了解吸附劑的利用率及質傳區域的大小。依本次實驗結果得知，當溫度為650℃時，吸附劑的利用率及質傳區域最高。 氣-固化學反應速率不僅與反應溫度的有關，亦受吸附劑粒子的種類、結構與床內床質孔隙度影響。本研究利用阿瑞尼士法則(Arrhenius’ Law)分析反應速率常數獲得氧化鈣與氯化氫表面化學反應活化能分別為7.75及8.19(kJ/mol)，其頻率因子分別為4.27×10-3 及 1.37×10-2。結合先前學者及本研究之實驗數據，氧化鈣與氯化氫之反應為一兩步驟串聯反應。高溫時(≧650℃)，反應機制控制步驟為氧化鈣與氯化氫反應生成中間產物，氫氧氯化鈣(CaClOH)；反之，低溫時(＜650℃)，反應機制控制步驟為氫氧氯化鈣與氯化氫反應生成氯化鈣。
並列摘要
Production of hydrogen chloride (HCl) in an incineration or combustion process, such as municipal solid waste (MSW) incinerator and RDF boiler shows an appearance of the apparatus being corroded. Due to the strong oxidation of HCl, the apparatus of an incinerator, combustor or boiler cannot avoid the corrosion by HCl. An experiment of removing HCl in high temperature was designed for the purpose to become more familiar with the process of removing HCl in situ furnace at high temperature. Ca-Based sorbents are commonly used in an incineration process to remove acid gases from flue gas such as HCl and sulfur dioxide (SO2). The purpose of this present study is to investigate the initial reaction behaviors of calcium oxide (CaO) and HCl. The experiments were carried out in a bench scale fixed-bed reactor and the experimental data were analyzed by unreacted shrinking-core model to calculate the reaction rate constants at each temperature. The tested reaction temperatures were operated in a range of 600-800 ℃ in this study. The average sorbent diameters were 163 and 460 μm, respectively. Breakthrough curve is an important index in fixed bed reactor. The utilization of sorbent and width of mass transfer zone can be understood from the breakthrough curve. By the results of this experiment, there was the most utilization and narrowest mass transfer zone before breakthrough time at 650 ℃. The reaction rate does not only relate to temperature, it is also affected by the type and structure of sorbent and bed porosity. The activation energy and frequency factors of the CaO and HCl surface reaction are 7.75 and 8.19 (kJ/mol), 4.27×10-3 and 1.37×10-2 for 163μm and 460μm sorbents was obtained from the analysis of the reaction rate constants in Arrhenius' law in this present. Combining the data of this present and previously, the reaction between CaO and HCl is a two steps mechanism in series. The controlling mechanism step is that CaO reacts with HCl to produce the mediate, calcium hydrochloride (CaClOH), at high temperature (>=650 ℃); on the other hand, CaClOH reacts with HCl to produce CaCl2 at low temperature (<650 ℃).