Influence Of Biomass Ash On Sintering Characteristics Of Oxygen Carrier During Chemical Chain Gasification Of Coal

Coal chemical chain gasification can be regarded as an organic coupling of chemical chain technology with solid heat carrier pyrolysis,coal catalytic gasification and fluidized bed process,which is one of the feasible ways to achieve clean and efficient coal gasification,but the relatively low gasification rate of coal semi-coke is the key to limit the efficiency of the whole chemical chain gasification process.By doping alkali metals and transition metals as catalysts in the oxygen carriers,the reaction rate and conversion rate of the oxygen carriers can be improved,but the alkali metal elements generally have a low melting point,which will cause sintering on the surface of the oxygen carrier particles,which in turn may lead to a reduction in the reactivity of the oxygen carriers and a reduction in the reaction conversion efficiency.Therefore,in this paper,two kinds of biomass ashes,straw and sawdust,were used as additives,and anthracite coal coke,two natural iron ore oxygen carriers and two natural manganese ore oxygen carriers were used as research objects to investigate the effect of biomass ashes on the reaction characteristics of coal coke gasification and the sintering characteristics of oxygen carriers in the chemical chain gasification process.（1）The effects of the proportion and type of biomass ash on the carbon microcrystalline structure of coal coke and the gasification reactivity of coal coke were investigated by XRD and TG;the results showed that the addition of both straw ash and sawdust ash slowed down the graphitization process of anthracite during pyrolysis,and the degree of slowing down became more obvious as the addition proportion increased;both types of biomass ash improved the gasification reactivity of coal coke,and as the addition proportion increased,the Both types of biomass ash will improve the graphitization activity of coal coke,and the increase in the percentage of addition is more significant.The slowing down of coal coke graphitization by biomass ash and its richness in catalytic active alkali and alkaline earth metals are the main reasons for its increased activity in coal coke gasification reactions.Compared to sawdust,straw ash was more significant in slowing down the carbon microcrystalline structure of coal coke and increasing the activity of coal coke gasification reactions,mainly due to the high K and Na content of straw ash.（2）The effect of biomass ash types and proportions on the sintering characteristics of oxygen carriers was investigated using thermomechanical analysis（TMA）and high temperature hot bench characterisation;the mechanism of the effect of biomass ash on the sintering of oxygen carriers was investigated with the aid of Factsage software and XRD.The results showed that the sintering process curves of both iron ore and manganese ore carriers could be divided into two stages:solid phase sintering with slow volume shrinkage and liquid phase sintering with rapid shrinkage.The addition of the two types of biomass ashes decreased the solid phase sintering start temperature,prolonged the solid phase sintering process and shortened the liquid phase sintering process of the hematite oxygen carriers,and the solid phase sintering of the two oxygen carriers increased with the increase of the proportion of biomass ashes added,and the liquid phase sintering rate increased,and the effect of straw ash on the sintering process of hematite was more significant with the same addition proportion;the effect of straw ash on the sintering process of ilmenite The effect of straw ash on the sintering process of ilmenite showed the same trend as that of hematite,while the effect of sawdust ash on the sintering process of ilmenite was not obvious.The results of the high temperature thermal bench indicate that the addition of both biomass ashes promotes the sintering of both hematite and ilmenite oxygen carriers.Both straw ash and sawdust ash caused an increase in the solid phase sintering start temperature and a shortening of the solid phase sintering process of the manganese ore 1 oxygenate carrier,and the corresponding temperature of the liquid phase sintering start was also increased,and the rate of the liquid phase sintering stage was reduced,which played a role in inhibiting the sintering of the manganese ore 1 oxygenate carrier.The effect of sawdust ash and straw ash on the sintering process of the Manganese Ore 2 oxygenate was not significant at 5%and 10%,but when the addition ratio was increased to 15%and 20%,the straw ash reduced the temperature corresponding to the start of solid phase sintering and liquid phase sintering of the Manganese Ore 2 oxygenate,and sawdust ash did not change the temperature corresponding to the start of solid phase sintering and liquid phase sintering of the Manganese Ore 2 oxygenate,but the shrinkage rate of both solid phase sintering and liquid phase sintering increased.Factsage calculations show that the reaction of iron ore with sawdust ash produced higher melting point calcium feldspar and plagioclase in the solid phase sintering stage while the reaction of iron ore with straw ash produced lower melting point potassium feldspar and potassium containing compounds resulting in iron ore sintering.With the addition of biomass ash,the solid-liquid phase sintering temperature of the Mn ore 1 oxygenate increased and the addition of sawdust ash resulted in an earlier solid phase sintering than the addition of straw ash.The reaction of the manganese ore with the biomass ash produces the higher melting points of roseworthite Mn Si O₃and spinel Fe₂Si O₄,thus causing a later sintering stage.