气氛对煤矸石中矿物质高温碳热还原反应的影响

利用煤矸石制备复合耐火材料是实现煤矸石高值利用的有效途径之一.以山西平朔煤矸石为研究对象,利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)分别研究了1200~1500 ℃氩气(Ar)和氮气(N2)气氛下煤矸石中矿物质的碳热还原反应情况,并通过变换两种气体通入次序,研究了气氛通入次序对矿物质碳热还原反应的影响.结果显示,只通入Ar时,高温样品中的莫来石在1300 ℃时开始发生碳热反应生成碳硅石(SiC);只通入N2时,莫来石在1300 ℃时发生碳热还原氮化反应生成β-Sialon相(Si5AlON7)和刚玉相(Al2O3);当先通入Ar并停留1 h后通入N2停留2 h时,样品中生成的碳硅石在通入N2后转化为β-Sialon相,而且中间体碳硅石的生成能够明显促进莫来石向β-Sialon相的转化.当煤矸石中碳含量较低时,热处理过程中难以同时生成SiC相和Sialon相.高温下煤矸石样品中β-Sialon相的生成使样品表面的棒状颗粒增多.

Effect of Atmosphere on the Carbothermal Reduction Reaction of Mineral Matters in Coal Gangue at High Temperature

Producing refractory material by coal gangue is one of the effective ways to realize the high-value utilization of coal gangue.The carbothermal reduction reaction of mineral matters in Pingshuo coal gangue at high temperature(1200-1500 ℃)under different atmospheres and effect of atmosphere on the mineral transformation were investigated by X-ray diffraction and scanning electron microscopy.Results show that the mullite in high-temperature coal gangue samples reacts with carbon to form moissanite (SiC)above 1300℃under argon atmosphere;while,the mullite transforms to β-Sialon(Si5AlON7)and corundum(Al2O3)above 1300 ℃ under nitrogen atmosphere.The formation of moissanite in samples could accelerate the transformation of mullite to β-Sialon when the coal gangue was firstly heated under argon atmosphere and then was heated continuously under nitrogen atmosphere.The moissanite and β-Sialon were difficult to be formed simultaneously in the coal gangue with low carbon content at high temperature.The β-Sialon in the high-temperature samples presents rod shape.