以氨氣去除焚化爐燃燒廢氣中氯化氫酸氣可行性分析

Abstract

本研究旨在探討氨氣注入法去除焚化排放廢氣中氯化氫酸氣之可行性。氨 氣注入法乃屬乾式空氣污染防治方法，除可降低初設費用及操作成本，避 免溼式法所產生廢水處理問題，更可預防氯化氫酸氣在低溫冷凝時所引起 之焚化設備腐蝕現象。此外因其乃是直接注入氨氣，不須其他酸氣去除裝 置，而節省了空間之需求。在焚化系統中直接注入氨氣，可和焚化廢氣中 氯化氫氣直接反應生成氯化銨顆粒，因此以氨氣注入法去除氯化氫氣之可 行與否，決定於其去除效率之高低，以及其所生成氯化銨固體顆粒大小是 否能隨焚化灰燼被集塵設備所收集。研究首先發展了一數學模式，探討各 種不同焚化狀況下，以氨氣去除氯化氫酸氣之效率，以及其所形成氯化銨 顆粒大小。應用一熱力學平衡模式，以預估氯化氫酸氣之去除效率隨溫度 與進氣濃度之關係。此外產物顆粒大小則藉由一氣體至固體生成模式( Gas- to- Particle Formation Model)，來模擬其在各種操作條件下粒子 形成過程。並建立實驗進行氯化氫氣去除率之研究。模式結果發現當操作 溫度在120oC以下，且氨氣與氯化氫氣注入比為1:1時，氨氣注入法可有效 去除氯化氫氣，以符合目前排放標準，且在適當操作條件下，產物顆粒可 凝結在既存飛灰上，使飛灰平均粒徑增加，此將有利於集塵設備收集。實 驗初步完成了停留時間、溫度、進氣濃度及NH3/HCl注入莫耳濃度比對氯 化氫氣去除效率影響。在本實驗操作條件下所得結果顯示，氯化氫氣去除 效率可由模式預測得相同變化趨勢 The purpose of this paper is to develop a mathematic model for studying the feasibility of ammonia injection for the removal of HCl gas from incineration process. Ammonia injection is one of dry treatment of air pollutions. It has the advantages of low installation and operation costs. It prevents the waste water treatment problem and corrosion problem of wet scrubbing method. In addition, the ammonia injection method dose not require other handware installation devices, therefore reduce the space requirement of the incineration process. The product of ammonia injection to react with Hydrogen chloride is ammonium chloride particles. Therefore the feasibility of ammonia injection depends mainly on the removal efficiency of HCl and the particle size of NH4Cl products. The fist portion of this study focuses on the theoretical study of the removal efficiency of HCl as well as the particle size distribution. A thermodynamic model has been applied to predict the HCl removal efficiency as a functions of inlet HCl concentration and operation temperature. In addition, a gas- to- particle formation model has also been developed to evaluate the evolution of particle size distribution. Laboratory scale study of HCl removal efficiency has also been conducted. The theoretical results indicate that high removal efficiency of HCl is possible, which can meet the current emission standard of HCl gas, at operation temperatures under 120oC. In addition, under proper operation conditions, the product vapor may condense on existing fly ash particle. This will increase the average size of fly ash, and enhance its collection by articulate control devices. The first stage of experiment has accomplished the effects of residence time, temperature, inlet HCl concentration and NH3/HCl inlet molar ratio on the HCl removal efficiency.The results show that HCl remoal efficiency is high and similar to theoretical prediction.