煤炭在當今全球能源系統中仍占有重要的地位，短期內難以被完全取代。而其燃燒過程中所造成之二氧化碳與空氣污染物排放，仍是低碳能源轉型時亟需克服的關鍵挑戰。鐵粉作為無碳燃料，燃燒過程不直接排放CO2，且具有循環再生潛力，近年來被視為具減碳潛力之替代燃料。因此，本研究透過以部分鐵粉取代煤炭，探討煤炭與鐵粉共燒之燃料特性與污染物排放。首先，針對煤炭(Coal)與鐵粉(IP)進行燃料特性分析，包括熱值分析、近似分析與元素分析；接著再利用熱重分析儀探討燃料在空氣環境下的受熱行為，並進行活化能分析。最後，將煤炭與鐵粉以不同比例混合，利用鼓泡式流體化床進行共燒實驗，實驗參數包括鐵粉混摻比(0~40%)與二次空氣比例(0~30%)，探討不同操作條件下的煙道氣組成、爐體溫度分佈、飛灰排放與氧化鐵組成，並進行可用能分析。熱重分析結果顯示，煤炭與鐵粉混摻後主要呈現兩個反應階段，分別為200~500°C之失重階段與500~1000°C之增重階段。使用Coats-Redfern法進行活化能分析，隨著鐵粉混摻比提升整體活化能呈現增加的趨勢，然而在BR=20%時具有較低的活化能。在流化床實驗方面，隨著鐵粉混摻比的提升使得密相區溫度提高。在BR=30%具有較低CO2、CO、NOx與SO2的排放，但同時具有最高飛灰排放。當混摻比提升至BR=40%時會導致密相區燒結影響流化效果，使CO排放提高。隨空氣分級比例提高，在分級比例20%時NOx排放顯著降低。此外，於BR=20%條件下空氣分級比例20%時，呈現最低CO2、CO排放與最高可用能效率，而空氣分級亦顯著降低飛灰排放量。

This study investigated the co-combustion characteristics of coal and iron-powder (IP) in a 10 kWth bubbling fluidized bed reactor. Coal, with a higher heating value of 27.16 MJ/kg, was partially replaced by carbon-free iron-powder, which has an estimated heating value of 6.69 MJ/kg based on oxidation to Fe3O4. Thermogravimetric analysis revealed two major reaction stages: a mass-loss stage between 200 and 500 °C associated with coal combustion, followed by a mass-gain stage between 500 and 1000 °C due to iron oxidation. Activation- energy analysis using the Coats-Redfern method showed that the apparent activation energy generally increased with increasing iron-powder blending ratio. Co-combustion experiments were conducted with iron-powder blending ratios of 0-40% and air-staging ratios of 0-30%. A blending ratio of 30% reduced CO2, CO, NOx, and SO2 emissions while achieving the highest exergy efficiency (33.26%) without air staging. However, excessive iron-powder addition (40%) induced bed sintering, deteriorated fluidization, and increased CO emissions. An air-staging ratio of 20% effectively suppressed NOx formation and reduced fly ash emissions. Under a 20% iron-powder blending ratio combined with 20% air staging, the lowest CO2 and CO emissions were obtained, and the highest exergy efficiency was achieved (36.8%). These results demonstrate that appropriate iron-powder substitution combined with air staging can simultaneously reduce pollutant emissions and enhance exergy efficiency, providing useful guidance for the application of iron-powder co- combustion in existing fluidized bed combustion systems.

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