Combustion characteristics and reactions of stacked wet pulverized magnesium

Experiments were conducted to investigate the combustion of stacked wet pulverized magnesium. The flame spread over the stack was imaged by infrared camera. The flame shape, flame height, flame spread speed and combustion duration were extracted from infrared images and analyzed. It turned out that the flame spread behavior was closely related to the particle size and moisture content. The smallest particle size at 27 μm had the most violent combustion compared to 61 μm and 90 μm at the same moisture content. With constant particle size, the flame intensity was reinforced as increasing the moisture content reaching the maximum between 20% and 25%. The flame spread would be attenuated instead with higher moisture content. It was believed to be resulted from the competition of chemical (positive) and thermal (negative) effect of water on magnesium combustion. The combustion process and reactions were scrutinized through direct observation and characterization of collected products. The product would either remain original prism-like strip shape or break down to scattered powders. During flame spread, the magnesium would react with oxygen, nitrogen, carbon dioxide and water in air yielding products with disparate colors. Finally, the combustion mechanism was deeply interpreted based on product morphology and reaction analysis.