Experimental Study On Effect Of Additives On Characteristics Of Biomass Ash Slagging

Biomass energy,as the fourth largest energy resource in the world's primary energy consumption,is the only solid biomass energy that can be stored and transported.However,in the actual combustion and gasification process,a series of physical chemical reactions will take place in biomass because it contains a large number of alkali metal elements,such as K and Na and the mineral Si,Cl Sand so on,in the process of actual combustion and gasification of biomass,which will play an important role in the future energy utilization structure of human beings.The formation of low melting point compounds or eutectic leads to serious problems such as ash deposition,slagging,high temperature corrosion and so on,which affect the normal operation of the boiler.Therefore,on the basis of selecting appropriate additives to improve the ash characteristics of biomass,so the formation of slagging and other problems can be restrained.It is of great significance to the utilization of biomass on a large scale.(1)In this paper,four kinds of biomass such as rice straw,wheat straw,corn straw and sawdust were selected as raw materials.Firstly,two different ashing methods were used to study the change of ash content with ashing temperature and time.The basic elemental analysis,industrial analysis and ash composition detection were carried out.The results showed that in order to measure ash content accurately,the method of low temperature ashing was more accurate;The results showed that the content of inorganic elements in different biomass ash was obviously different,but there was a common characteristic that the specific proportion of inorganic elements oxide content was large.(2)The characteristic temperature of four kinds of biomass ash was measured,and the relationship between ash melting point and ash composition was studied.Four typical integral ashing temperatures were selected in the range of 600?to900?,and the samples were placed in a muffle furnace for burning ash.The changes of ash composition with ashing temperature and the morphology of ash samples are obtained by SEM-EDX.The results show that the ash composition changes at 600?or800?.The ash content decreased slowly at 800 after the fastest ash content decline.The SEM?-EDX detection of ash sample found that different biomass,at different temperature,ash sample microcosmic.Because of the different species,the gray particle structure of biomass has diversity,which also reflects the complexity of many inorganic elements in the form of biomass.(3)On the basis of the study of biomass ash characteristics,wheat straw was used as raw material in this paper.The experiment of burning wheat straw with different additives was carried out,and the additive with better slagging effect was selected.The mechanism of additive inhibiting slagging of ash sample was studied.Ca O,NH4H2PO4,(NH4)2SO4 and kaolin were used as additives,mixed with wheat straw,and then slowly ashes in muffle furnace.The results show that the effect of the four additives on slag deposition is as follows: kaolin>NH4H2PO4> Ca O >NH4H2SO4.The combustion with the additives mentioned above will be carried out.The microstructure and main element characteristics of the ash samples in the presence of various additives were studied,and the XRD phase of the ash samples with typical characteristics was detected to detect the ash-forming phase.The action mechanism of additives on alleviating slagging of wheat straw was studied.The results of XRD phase analysis showed that K in ash samples mainly existed in the form of KCl and K2SO4 at 600 at lower ashing temperature,and with the increase of temperature,the alkali metal K ?existed mainly in the form of KCl and K2SO4.Reaction of alkali metal K with Si O2 in ash to form KCa PO4 and K2Mg(Si O4)with lower melting point After the addition of four additives,the active substance elements such as C,P,Al,S reacted with K first to form Al2Si7O5(mullite)and Al PO4 with high melting point.In this paper,some studies on the characteristics of biomass ash and the action mechanism of additives on the inhibition of slagging can provide a theoretical reference for understanding the basic properties of biomass and play an important role in the large-scale utilization of biomass.