使用富氧燃燒之燃氣鍋爐與燃油鍋爐之性能比較研究

Abstract

本實驗研究富氧燃氣及燃油鍋爐之燃燒主軸中，主要以進行燃氣(瓦斯)及燃油(超級柴油)鍋爐之測試，並在尾氣部分連接選擇性觸媒還原系統進行脫硝效率的研究。除了兩種鍋爐找到最佳之燃燒參數(EA為1.3)外，在富氧燃燒之研究中，將氧氣濃度控制在分別為21%, 23%, 24%, 26%以及28%。由實驗結果顯示，氧濃度越高使燃氣鍋爐內高溫區擴大，但最終在氧濃度達至26及28%時，其高溫區將停止擴大。因此，使最高溫度及廢氣溫度也隨之上升。在進行微富氧燃燒，使燃料燃燒更完全，減緩了一氧化碳及二氧化碳的濃度，其中後者因被氧氣稀釋。氮氧化物的生成主因為熱式氮氧化物(Thermal NOx)，故爐內溫度隨著氧濃度增加而使氮氧化物濃度增加。而燃氣與燃油鍋爐都會因當氧氣濃度增加可提升其燃燒效率(分別提升至71.3%及69.6%)，進而達到節能的效果。此外，將燃燒後之廢氣引入選擇性觸媒還原系統進行處理，可發現脫硝之效率高達98%。

This experimental research uses gas (Liquefied petroleum gas)-fired and oil(Diesel)-fired boilers to investigate the oxygen-enriched combustion. In addition, the flue gas pipe is connected with Selective catalytic reduction system (SCR) to study the DeNOx effect. The varying parameter is oxygen concentration (Ω), consisting of 21% (regular air), 23%, 24%, 26% and 28%, respectively. The excess air is always fixed 1.3 for every burning experiment. Based on the experimental results, high temperature region grows with an increase of oxygen concentration (Ω). Eventually, it reaches a saturation state that such region is almost invariant for Ω= 26% and Ω=28%. So do for the maximal and exhaust flue gas temperatures. CO and CO2 generations are decreased as Ω increases. The former one is that the combustion is more completed, whereas the latter one is diluted by extra oxygen. The major reason for increase of Thermal NOx generation is due to the resultant higher boiler temperature caused by increasing the oxygen concentration. The increase of oxygen concentration leads to improve the combustion efficiencies for both cases (from 68.6 and 64.4 up to 71.3% and 69.6%, respectively) that can save energy. Finally, the exhaust gas is treated by SCR system after combustion, and DeNOx efficiency is up to 98%.