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

• Published in: Energy (Oxford) 2021-07, Vol.226, p.120393, Article 120393
• Main Authors: Shi, Wei, Sun, Yunlan, Zhu, Baozhong, Liu, Jianzhong
• Format: Article
• Language: English
• Subjects: Aluminum; Burning; Carbon dioxide; Combustion; Combustion efficiency; Combustion products; Cryolite; Delay time; High speed cameras; Ignition; Micron-sized aluminum powder; Morphology; Oxidation; Post-processing; Sodium; Sodium fluoroaluminate
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2021.120393

To improve the ignition and combustion performance of micron-sized aluminum powder (m-Al) in CO2, a self-made pipe furnace experimental platform was established to study the effects of sodium fluoroaluminate (Na3AlF6) on the ignition delay times, combustion processes, combustion efficiencies, and combustion products of 1–2, 5, and 30 μm aluminum (m-Al1, m-Al5, and m-Al30) powders in CO2 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 Na3AlF6 has a lower initial reaction temperature and a shorter ignition delay time than those of m-Al without Na3AlF6 addition. The effect of Na3AlF6 content on the ignition delay time is different for m-Al with different sizes. The ignition delay times for m-Al1 and m-Al5 increase with increasing the Na3AlF6 content, while the corresponding values of m-Al30 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 Na3AlF6, thereby promoting its ignition and burning. The combustion efficiency of m-Al is significantly enhanced, especially for m-Al30. The effect mechanism of Na3AlF6 on the ignition and combustion of m-Al in CO2 was discussed. •Na3AlF6 can decrease the initial reaction temperature and ignition delay time of Al.•Na3AlF6 addition amount influences on the ignition delay time of Al powder.•Particle self-heating and fluorination degree lead to the different variation of ignition delay time.•Al combustion efficiency increases significantly with Na3AlF6 addition.