Ignition sensitivity of coal/waste/biomass mixtures

Abstract

Due to environmental concerns and depleting reserves of fossil fuels, alternative, environmentally friendly fuels such as biomass and waste products are being considered for partial or full fossil fuel replacement. A particular problem of waste materials such as sewage sludge is the low energy density and to deal with this several heat and power generation facilities are firing fuel mixtures, such as coal-biomass, coal-sewage sludge or even biomass-sewage sludge. These processes effectively involve mixtures of flammable powders whose ignitability and explosibility characteristics are not known and therefore present un-quantified safety risks to the new technology. This study reports on these risks and on the reactivity characteristics of the two and three component powder mixtures of coal / sewage-sludge / torrified-wood-pellet. In particular the chemical composition, the ignition sensitivity parameters (including minimum ignition energy, minimum ignition temperature on a layer, minimum explosive concentration) and flame speed have been determined. In all cases the measured parameters mixtures were within the range defined by the lower and upper value components and no synergistic or antagonistic effects were noted.