Impact of using fly and bottom ash on fire risk assessment in hard coal mines

Using fly ash in hard coal mines may lead to an increase in hydrogen concentrations in the mine atmosphere. This may result in incorrect fire risk assessment based on changes in hydrogen concentrations and fire indicators determined on their basis. The paper presents the results of changes in the concentrations of hydrogen and other gaseous components obtained from water-ash mixtures generated from the ash obtained from a coal-fired boiler and a coal- and biomass-fired boiler. As a result of the experiment, it was found that the only gas evolving from mixtures in large quantities was hydrogen. Other gaseous components, important from the point of view of fire hazard assessment (ethylene, propylene, acetylene, carbon monoxide), were released in very small amounts. Several dozen times higher amounts of hydrogen were released from fly ash obtained from a boiler in which biomass is co-fired together with coal, than from the ash from a coal-fired boiler. The highest intensity of hydrogen evolution was observed within the first 24 h from the moment of producing water-ash mixtures. At a subsequent time, hydrogen evolution was clearly smaller. Hydrogen was also released from water-ash mixtures made from bottom ash. However, the determined values of hydrogen concentration were several hundred times lower than the concentrations of hydrogen released from fly ash.

Automated summary

Using fly ash in hard coal mines may increase hydrogen concentrations in the mine atmosphere, leading to incorrect fire risk assessment. The experiment showed that fly ash from a coal and biomass-fired boiler released much higher amounts of hydrogen compared to ash from a coal-fired boiler.