碳热还原粉煤灰物相变化规律
Phase transformation of carbothermal reduction coal fly ash
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摘要: 在感应炉中,空气气氛下,以粉煤灰为原料,木炭为还原剂,不同温度条件下对粉煤灰还原反应过程及合金进行研究。利用XRD,SEM-EDS技术对还原产物进行分析检测。结果表明,碳还原粉煤灰分为4个阶段:(1 373~1 673 K)Fe2O3和碳反应生成铁;(1 773~1 873 K)石英和碳反应生成Si C,莫来石发生分解并与碳反应生成Si C和Al2O3;(1 973~2 173 K)石英除生成较多Si C,还有少量Si生成,部分Al2O3和空气中的氮气生成Al5O6N,并最终分解成Al2O3和Al N;2 273 K氧化铝和Si C,C反应生成Al,Si,Al N和碳反应生成Al。高温下有气态的Si O,Al2O产生,造成部分铝硅损失。合金由3个相组成,3者相互混合存在,除含有较多Al,Si,Fe,Ca外,还含有部分Si C。在合适的配碳量下,Al2O3对Si C的生成有抑制作用。Abstract: 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.