Study On The Characteristics Of Ash During Co-combustion Of Biomass And Coal/Char

Biomass is one of the renewable energy. Biomass reburning and co-combustion ofbiomass and coal are the most effective ways among biomass utilization technologies.However, the melting point of the ash during co-combustion of biomass and coal is oftenlower than that during coal combustion, making the risk of safe operation for boilers.Therefore, it has great scientific and practical significances to study on the characteristics ofash during the co-combustion of coal/char and biomass. This study provided an overview ofthe present research on the characteristics of ash during co-combustion of coal/char andbiomass. Typical biomass and coal/char were selected to prepare the ash samples. The keyfindings of this study are as following:Firstly, the blending ratio of biomass, ashing time, the atmosphere and other factorswhich affect the ash production ratio were taken into account. The ash production ratioincreased with the increasing of the blending ratio. The ash production ratio decreased withthe increasing of ashing time and increased with the increasing of oxygen concentrations.Secondly, the mechanism study on ash production was conducted. The thermalgravimetric analysis was used to reveal the influence of interaction between biomass andcoal/char combustion on ash production ratio during co-combustion process. The ashcomposition was also analyzed in order to further understand the effects of the precipitationand retention of Na, Mg, K, Cl, S on the variation of ash production ratio. The influence ofanhydrite decomposition on ash production ratio variation was further studied.Finally, the influence of different factors on ash fusion point was studied. The resultsshowed that the ratio of biomass obviously affected the ash fusion point but the ashing timeand atmosphere has little effect on the ash fusion point. The existed prediction model of ashfusion point has little precision. Thus, it is need to establish a new prediction model of ash fusion point during co-combustion of coal/char and biomass. The new full regressionprediction model of ash fusion point during co-combustion of coal/char and biomass wasfinally set up with the sub-model of SiO2component based on the gray correlation analysisbetween ash fusion point and ash component.