准东煤和煤矸石共燃对灰熔融特性和钠元素释放行为影响

Ash fusion and sodium release characteristic during co-combustion of Zhundong coal and coal gangue

本文利用马弗炉试验台,在815℃和1000℃下进行了准东煤和煤矸石的共燃实验,并借助灰熔融特性分析仪、电感耦合等离子体分析仪(ICP—OES)、电子扫描显微镜-能谱仪(SEM-EDS)和X射线衍射仪(XRD)对掺混样品灰熔融特性(AFTs)、钠元素释放行为、表观形貌和矿物进行表征.结果表明:随着煤矸石掺混(CG)比例增加,准东煤(ZD)灰熔融温度呈先下降后升高的变化趋势,并在掺混比例达到15%时达到最低值,说明煤矸石掺混比例与掺混样品(ZD/CG)灰熔融温度间呈非线性关系;通过SEM-EDS与XRD表征可知,随着煤矸石掺混比例增加,高温下掺混样品中耐熔矿物(硫铝酸钙、镁黄长石方镁石、石英和赤铁矿等)和助熔矿物(钙黄长石和钠长石等)之间相互转化是影响掺混样品灰熔融温度的主要原因;无论何种掺混比例,残余灰中钠元素含量实测值(RNa/exp)均大于理论值(RNa/cal),且二者偏差率(ηdev)均为正数,表明准东煤与煤矸石在高温下发生了抑制掺混样品中的钠元素向气相释放的协同反应.

In this study, the co-combustion of Zhundong coal and coal gangue was investigated in a muffle furnace at 815 ℃ and 1000 ℃, and then subjected to ash fusion analyzer, SEM-EDS and XRD analysis for their AFTs, sodium transformation, morphological and mineralogical characteristics. The results showed that the AFTs of ZD/CG ashes decreased first, reaching the minimum AFTs at CG addition of 15%, but increased afterwards, exhibiting a non-linear correlation between CG addition ratio and ATFs. The results from SEM-EDS and XRD revealed that the fusion characteristics of the ZD/CG ashes were mainly dependent on interconversion between the refractory minerals such as yeelinmite, akermanite, periclase, quartz and hematite, and the fluxing minerals such as gehlenite and albite. RNa/exp was always greater than RNa/cal, and the deviation rates were all positive in any blending ratio, indicating that synergistic reactions were occurred between ZD and CG to inhibit the release of sodium into the gas phase at high temperature.