台灣在能源轉型與淨零排放目標下，燃煤發電短期內仍具穩定供電功能，然而燃煤燃燒會產生 CO2、NOx 與 CO 等排放。現行燃煤電廠多仰賴 SCR 或 SNCR 等後端脫硝技術控制 NOx，但需額外設備與藥劑成本。因此，本研究將 Urea 作為固態含氮輔助燃料與爐內原位脫硝還原劑，直接於燃燒器內探討 Coal/Urea 混摻與分級燃燒下，對燃燒特性及污染物排放的影響。本研究藉由對 Coal 與 Urea 進行熱值、近似與元素分析，再利用 TGA、TGA-FTIR 與 TGA-GCMS 探討不同比例 Coal/Urea 混摻燃料於空氣與 N2 氣氛下的熱分解特性、氣相產物、協同效應與反應動力學變化，並透過單顆燃料錠燃燒實驗分析 Urea 混摻比例對燃燒時序與煙道氣排放影響，後續於 3 kWth 鼓泡式流化床（Bubbling Fluidized Bed）中進行底部混摻、燃料分級、空氣分級實驗，並藉由綜合排放指數（Comprehensive Emission Index, CEI）、 NOx 濃度降低效率（NOx concentration reduction efficiency）、溫度分佈均溫指數（Temperature Uniformity Index, UI）與 SNCR有效反應溫度偏離指數(SNCR Temperature Deviation Index, STDI)指標進行結果量化，以利篩選出較佳的操作條件。
TGA 與協同效應分析結果顯示，Coal/Urea 混摻燃料呈現兩階段反應特徵，低溫區具有促進作用，於 220-290°C 區間轉為抑制，推測與 Urea 熱分解形成縮二脲、氰脲酸等熔融相中間產物有關，進而影響 Coal 揮發份釋放與後續氧化反應。單顆燃燒結果顯示，Urea 混摻會延長點燃延遲並縮短氣相燃燒時間，當 Urea 混摻比例提高至 BR30% 以上時，燃料表面形成碳化熔融層，顯示高比例 Urea 會改變燃料表面結構，並可能抑制揮發份釋放，但碳轉化率仍維持於 95% 以上。流化床結果顯示，在固定總 Urea 熱輸入比例 UBR10% 時，較佳操作參數為 FSCR30%C、SAR40% 與 USR30%，CEI 值為 0.259，NOx 濃度降低效率為 70.28%，UI 為 94.63%，STDI 為 4.71%。此結果顯示，該操作條件可在維持爐內溫度均勻性的同時，使反應區溫度接近 SNCR 有效反應溫度範圍，促進 Urea 分解產物參與 NOx 還原，並兼顧 CO 排放控制，其中 NOx 與 CO 分別為 117.11 ppm 與 365.11 ppm，皆低於固定污染源排放參考基準，代表此分級配置可兼顧 NOx抑制、CO 控制與燃燒穩定性。在本研究實驗設備規模下且當量比 0.71的條件下，若後續要提高 Urea混摻比例，建議維持底部 90%C+10%U 配置，並以分流方式於流化床下游增加 Urea，可有效兼顧 NOx排放控制與促進 CO 氧化。

Solid urea was evaluated as a nitrogen-containing auxiliary fuel and an in-furnace NOx-reducing agent for staged coal combustion. Coal/urea blends were characterized by proximate and elemental analyses, TGA, TGA-FTIR/GCMS, and single-pellet combustion, followed by staged combustion experiments in a 3 kWth bubbling fluidized-bed combustor. TGA results showed that urea shifted the reaction toward lower temperatures, while condensed-phase intermediates caused alternating promoting and inhibitory effects. Single-pellet tests showed delayed ignition and shorter gas-phase combustion, with a carbonized molten layer forming at BR ≥ 30%; carbon conversion remained above 95%. In the fluidized bed, the preferred configuration was UBR10% + FSCR30%C + SAR40% + USR30%, yielding 117.11 ppm NOx, 365.11 ppm CO, a CEI of 0.259, a NOx concentration reduction efficiency of 70.28%, a UI of 94.63%, and an STDI of 4.71%. ICP-MS analysis indicated no substantial change in the overall elemental composition of fly ash and bottom ash under staged coal/urea combustion. Overall, effective use of solid urea requires coordinated control of urea input, fuel staging, air staging, and furnace temperature to balance NOx reduction, CO control, NH3 slip, and combustion stability.

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