Magnesium particles combustion in CO₂-H₂O-N₂ mixtures

Magnesium powder is considered a highly promising high-density energy carrier capable of storing and transporting renewable energy while contributing to future CO₂ emission reduction. This work focuses on measuring the burning time of single magnesium particles in CO₂, H₂O, and CO₂–H₂O–N₂ mixtures, conditions scarcely investigated despite their relevance to solid rockets and metal-fueled ramjet applications. Magnesium was found to burn with a visible diffusion flame in both pure CO₂ and pure H₂O, with burning times following a power-law relation t=K·D₀ⁿ where n ranges from ∼1.4 in water vapor to about ∼2.0 in CO₂. Dilution with N₂ increases burning time, while increasing temperature and oxidizer concentration shorten it markedly. As the oxidizer concentration gradient is the driving force for diffusion and can be approximated by the oxidizer molar concentration, evaporation constant scales linearly with oxidizer concentration. Mixtures of CO₂ and H₂O indicate that H₂O plays the dominant role in driving combustion compared with CO₂. Water vapor exhibits roughly twice the oxidizing capacity of CO₂, resulting in significantly faster burning. All measured burning-time data were processed to develop a new empirical correlation applicable to CO₂–H₂O–N₂ mixtures. This correlation fills the long-standing gap in burning-time data for magnesium particles in mixed-gas environments.