Evaluation of Self-heating Propensities of Coal/Biomass Deposits in the Roller Mill of Pulverized Coal Thermal Power Plants

Abstract

Self-heating propensities of coal/biomass deposits in the roller mill were evaluated by the wire-mesh basket tests with four types of coals and three types of biomasses. The results showed that initial heat release rate obtained by the product of initial rate of temperature rise and heat capacity was considered suitable for evaluating the self-heating propensities of deposited coals and biomasses of 10 cm cubic. The initial heat release rate of biomass at 80℃ tended to be lower than that of coal deposits. The effects of ambient temperature on the self-heating propensities of coal/biomass deposits were evaluated. The obtained data showed that the initial heat release rate of biomass was less affected by ambient temperature than that of coal. Therefore, the risk of self-heating and ignition of biomasses was considered lower than that of coals. Furthermore, the effect of coal/biomass ratio on the self-heating propensities of coal/biomass deposits was evaluated at 80℃. The initial heat release rate of the mixture was decreased with the increase of the ratio of biomass to coal. Additionally, it was suggested that if the bulk density of coal/biomass mixture agrees well with the volume-weighted average bulk density of each mono-sample, the initial heat release rate of the mixture can also be estimated by the volumeweighted average of that of the mono-sample.