Experimental Study On Arsenic Release In Co-combustion Of Biomass And Coal

The co-combustion of biomass and coal can not only replace some fossil energy,but also discharge low CO2.,which is a very promising technical route..The heavy metal elements will be released into the atmosphere with the flue gas during the combustion process.However,there are few studies on the release law of mixed combustion arsenic.This paper will study this.After the co-combustion of tobacco stem/black bean straw/wheat straw/millet straw/corn stalk/rice straw/wood chips and Kaiyuan/Jingyu coal,it was found that some kinds of biomass could inhibit the release of arsenic,but some could promote the release of arsenic.When the biomass after the acid wash with coal and burned,the release of the seven pickled biomass arsenic all increased,which indicated that the alkaline metal elements in the biomass could inhibit the release of arsenic during combustion.When the mineral elements(Na,K,Mg,Ca,Al,Fe and Si elements)are added to the coal and burned,it is found that the alkaline metal elements inhibit the release of arsenic in coal and the Si element promotes the release of arsenic in coal.This indicates that the release law of arsenic of co-combustion has a great relationship with the mineral element content in biomass.The alkaline metal element in the biomass during the co-combustion can react with arsenic to form stable solid phase arsenates to inhibit the release of arsenic.The reason why Si can promote the release of arsenic is that it not only promotes the conversion of solid phase arsenic to arsenic in the gas phase,but also combines with some alkaline metal elements to form silicate.In addition,when the biomass after pyrolysis and coal were mixed and burned,the release of arsenic decreased.Therefore,the release of arsenic in the co-combustion is not only related to the mineral element content,but also related to the volatile matter in biomass.The high volatility in the biomass during co-combustion will increase the surface temperature of the coke,which will accelerate the burning rate.At the same time release a large amount of heat to promote the arsenic-containing minerals to decompose.By measuring the content of mineral elements in biomass,the reason why the ability of seven biomass to inhibit arsenic is different during co-combustion is explained.Finally,the changes of various forms of arsenic in the ash after combustion of Kaiyuan coal(KY),the ash after co-combustion of tobacco stem and coal(TS)and the ash of co-combustion of rice stem and coal(RS)were also discussed.The acid-soluble arsenic of the RC is reduced and the exchange arsenic is increased compared with the KY.The reason is that the large amount of heat released during the co-combustion promotes the decomposition of the acid-soluble arsenic in the coal.The reason for the increase in the exchangeable arsenic is that the arsenic oxide reacts with the K element to form K3ASO4 during co-combustion.Compared with the KY,the residual arsenic of the RS is decreased(the exchangeable arsenic),and the acid-soluble arsenic is increased.The reason for the decrease of the acid-soluble arsenic is that the residue arsenic is decomposed into acid-soluble arsenic,and the alkaline metal elements combine with arsenic to form the acid-soluble arsenic.The reason for the decrease of the residual arsenic may be that the Ca element in the tobacco stem reacts with the S element on the surface of the residual arsenic to promote the decomposition of the residual arsenic during the combustion.