面對全球淨零碳排趨勢，尋求無溫室氣體排放之替代能源成為各國重要發展目標。相較於氫氣等氣態能源，鐵粉具備極高的體積能量密度與極低的安全風險（粉塵爆炸指數 Kst < 200），因此被視為極具潛力的新型「金屬密集能源載體」。然而，微米級鐵粉氣固懸浮微粒在連續燃燒系統中面臨嚴峻的流體力學挑戰。最新理論指出，鐵粉群集火焰極易受局部對流與熱傳遞限制，從穩定的「連續傳播模式」退化為不穩定的「離散傳播模式」，並伴隨火焰前緣的動力學粗糙化，導致燃燒效率低落甚至熄火。本研究旨在開發一套低碳鐵粉渦流燃燒系統，並透過流場調控克服上述物理限制以達到完全氧化。
本研究建置了包含鐵粉進料系統、游渦式燃燒器及後端旋風分離器之硬體架構。為解決較重鐵顆粒易因慣性迅速穿透燃燒區的痛點，本系統創新導入了「粉體擴散鈍體（半圓形與90度角）」設計。此舉從流體力學層面人為優化了局部的佩克萊數（Péclet number），強迫粉體減速並向外擴散，藉此延長氣固接觸時間，確保火焰能避開離散模式的熄火風險，穩定維持於連續傳播狀態。
實驗結果顯示，實驗結果顯示，本系統成功實現了連續的無碳燃燒程序。經 X 光繞射 (XRD) 分析證實，在充足的滯留時間下，原本不規則的純鐵粉完全氧化轉化為高純度的磁鐵礦 (Fe_3O_4) 晶相。此外，掃描式電子顯微鏡 (SEM) 顯示，鐵粉經歷非揮發性燃燒的熔融與再凝固後，轉變為緻密的圓球狀或橢圓狀，極有利於旋風分離器的高效捕捉。本研究進一步於石英腔體內置盤管熱交換器進行熱回收實證。結果顯示在 9.6 kW 之理論燃燒熱功率下，成功將工作流體加熱至突破沸點（103.34°C）產生蒸汽，實測顯熱轉換效率達 11% 至 14%，圓滿驗證了鐵粉火焰直接加熱應用於工業製程熱水與蒸汽供應之工程可行性。本研究成功驗證了透過流場優化以維持連續金屬燃燒的工程可行性，為未來工業零碳熱能系統奠定了重要基礎。

This study presents the development of a low-carbon iron powder vortex combustion system, investigating its flame propagation mechanisms and product characteristics. In the pursuit of net-zero emissions, "Dense Energy Carriers" (DEC) have emerged to overcome the low volumetric energy density and storage challenges of hydrogen. Among various combustible metals (e.g., Al, Si, Zn, Fe), iron powder is evaluated as the most promising DEC due to its superior volumetric energy density (up to 25.5 GJ/m3), high earth-crust abundance, and safe dust explosion index (Kst<200 bar⋅m/s). Furthermore, its non-volatile combustion mechanism prevents nano-dust pollution, yielding easily recoverable micron-sized oxides. However, maintaining a stable flame in micron-sized iron suspensions is challenging due to the discrete nature of the heat sources. Recent theories indicate that iron flames can transition from a stable "continuous mode" to an unstable "discrete mode" associated with flame front kinetic roughening, which is highly dependent on local convection (Péclet number). To counteract the high inertia of iron particles and prevent premature escape from the combustion zone, "powder diffusion bluff bodies" (semi-circular and 90-degree) were innovatively introduced in the vortex burner. This design effectively optimized the local Péclet number, forcing particle deceleration and radial diffusion, thereby enhancing oxygen mixing and residence time to sustain the flame in the continuous propagation regime. Experimental results demonstrate that the system successfully achieved continuous carbon-free combustion. Material characterizations via X-ray diffraction (XRD) confirmed the complete phase transformation from irregular pure iron (Fe) to high-purity magnetite (Fe_3O_4). Furthermore, Scanning Electron Microscopy (SEM) revealed that the non-volatile surface combustion caused the particles to melt and resolidified into dense, spherical, or elliptical shapes, enabling highly efficient recovery. Furthermore, a built-in coil heat exchanger within the quartz chamber was utilized to demonstrate heat recovery. The results showed that under a theoretical thermal power of 9.6 kW, the working fluid was successfully heated beyond its boiling point (103.34°C) to generate steam, achieving a sensible heat conversion efficiency of 11% to 14%. This study validates the engineering feasibility of manipulating local convection to stabilize continuous metal combustion for zero-carbon industrial applications.

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