Sodium fluoroaluminate promoting the combustion of micron-sized aluminum powder with different particle sizes in carbon dioxide

To improve the ignition and combustion performance of micron-sized aluminum powder (m-Al) in CO 2 , a self-made pipe furnace experimental platform was established to study the effects of sodium fluoroaluminate (Na 3 AlF 6 ) on the ignition delay times, combustion processes , combustion efficiencies , and combustion products of 1–2, 5, and 30 μm aluminum (m-Al 1 , m-Al 5 , and m-Al 30 ) powders in CO 2 at 1000 °C. The combustion phenomenon was recorded by a high speed camera. The ignition delay time was obtained by post-processing the sequential images. m-Al containing Na 3 AlF 6 has a lower initial reaction temperature and a shorter ignition delay time than those of m-Al without Na 3 AlF 6 addition. The effect of Na 3 AlF 6 content on the ignition delay time is different for m-Al with different sizes. The ignition delay times for m-Al 1 and m-Al 5 increase with increasing the Na 3 AlF 6 content, while the corresponding values of m-Al 30 first increase and then decrease. The combustion products were subjected to the analyses of morphology, composition, and combustion efficiency. The oxidation shell of Al is fluorinated by Na 3 AlF 6 , thereby promoting its ignition and burning. The combustion efficiency of m-Al is significantly enhanced, especially for m-Al 30 . The effect mechanism of Na 3 AlF 6 on the ignition and combustion of m-Al in CO 2 was discussed.