Effects of Different Additives on the Ignition and Combustion Characteristics of Micrometer-Sized Aluminum Powder in Steam

To improve the ignition and combustion characteristics of micrometer-sized aluminum powder in steam at 900 °C, the present study focuses on the effects of adding different contents of Mg, NaF, and NaBH4. Experiments were conducted in two high-temperature tubular resistance furnaces to measure ignition temperatures, maximum combustion temperatures, and ignition delay times and to understand the combustion features of all samples. The experimental results show that Mg addition results in a reduced ignition temperature and ignition delay time of the micrometer-sized aluminum powder and causes two burning stages (a double-peak feature) because the Mg powder preferentially ignites before the micrometer-sized aluminum powder. The maximum combustion temperature increases with increasing Mg content. The ignition temperature and the ignition delay time are also significantly decreased with increased NaF or NaBH4 addition. However, the addition of NaF or NaBH4 lowers the maximum combustion temperature. The morphology, components, and residual aluminum contents of the solid combustion products are analyzed by scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis. The combustion efficiency is slightly improved with the addition of NaF. The different mechanisms by which the additives influence the ignition and combustion of micrometer-sized aluminum powder are believed to underlie these experimental results.