Preparation and characterization of inorganic foam modified with nano-magnesium hydroxide for inhibiting coal spontaneous combustion

To overcome the poor stability of currently employed foam material in preventing coal spontaneous combustion, the nano-stabilized foam was proposed in this study. Considering foamability and stability, the optimized concentration ranges and the interaction effect of each component were determined through single-factor experiments and response surface analysis. In the appropriate concentration range, the addition of nano-magnesium hydroxide further enhanced the foam stability. The optimal composition of nano-stabilized foam was obtained using the parametric optimization function. The stability coefficient of nano-stabilized foam was up to 99.91%. It can maintain the foam form for the longest time (>48 h), providing long-term wetting and oxygen insulation. Compared with other comparative foam materials, the nano-stabilized foam treated coal sample exhibited the minimal oxygen consumption rate and index gas release amount. Nano-stabilized foam can play the largest role in inhibition, and the inhibition rate was 70.61% at 100 °C. The inhibition rate of coal samples treated with nano-stabilized foam was also observed to be the biggest at each temperature. The coal sample treated with nano-stabilized foam had the highest cross-point temperature (242.3 °C), which was 31.47% than the raw coal. These experimental findings exhibit that the nano-stabilized foam has superior foam stability and inhibitory effect.