Phase transformation of carbothermal reduction coal fly ash

Investigation on thereduction reaction process of power station fly ash as well as alloy product with the re- ductant of charcoal in induction furnace was conducted at different temperatures in air. Composition of products ob- tained under different temperatures was analyzed by X-Ray Diffraction (XRD),and SEM & EDS technology. Experi- mental results show that the reaction process of carbon and fly ash was divided into four stages:at 1 373-1 673 K,iron is formed by Fe2 O3 and carbon;at 1 773-1 873 K,SiC is generated by quartz and carbon,mullite decomposed and re- acts with carbon to generate SiC and Al2 O3 ;at 1 973-2 173 K,in addition to SiC,a small amount of Si is also genera- ted by quartz and carbon,part of Al2 O3 reacts with N2 to generate Al5 O6 N,and it is finally decomposed into Al2 O3 and AlN;at 2 273 K,Al2 O3 reacts with SiC and C to form Al and Si,Al is generated by the reaction between AlN and car- bon. The gaseous SiO and Al2 O are generated at high temperature,causing the loss of part of aluminum and silicon;the alloy obtained at 2 273 K consists of three phases which exist and are mixed with each other,in addition to a large amount of Al,Si,Fe,Ca,a small amount of SiC is also contained in the alloy. Al2 O3 had an inhibiting effect on the formation of SiC when an appropriate quantity of carbon is added.