Combustion inhibition of biomass charcoal using slaked lime and dolime slurries

Abstract

Calcium hydroxide (Ca(OH)2) and magnesium hydroxide (Mg(OH)2) are promising fire suppressors because of their characteristics of nontoxic, cost-effective, and high fire suppression ability. In this work, a comprehensive study of fire inhibition of slaked lime and dolime slurries, containing different ratios of Ca(OH)2 and Mg(OH)2, was implemented for the first time. A synchronised imaging system was developed for the visualisation of the droplet evolution temporally. The chemical components were analysed by X-ray diffraction and thermogravimetric analysis. A single droplet test and a variable volume test were performed to measure the charcoal surface temperature under different conditions. The results demonstrated that the Ca(OH)2 slurry better inhibits combustion in comparison to water, which could significantly decrease the risk of fuel re-ignition. The main mechanism was found as the effective inhibition of the exchange of the oxygen and fuel by the thermally stable residues. Additionally, either adding the mixture of Mg(OH)2 or increasing the solid content of the Ca(OH)2 could further improve their effectiveness. Three stages of the fire suppression were identified in this work and a conceptual model was built accordingly to demonstrate the fire inhibition mechanisms. The results from this work could provide important guidance for the research into alternative methods of fire extinguishment.