高铝高炉渣系的熔化特性

 为了掌握高Al₂O₃条件下(w(Al₂O₃)为15%以上)高炉渣系的熔化特性,利用差式扫描量热仪分析了不同w(MgO)/w(Al₂O₃)、碱度(R)以及w(Al₂O₃)对高铝高炉渣的熔化温度及熔化热的影响。试验结果表明,炉渣熔化开始温度为1 248～1 291 ℃、熔化结束温度为1 432～1 485 ℃、熔化热为137～211 J/g;当w(Al₂O₃)=15%、高w(MgO)/w(Al₂O₃)时,发生了共晶逆反应,导致高炉炉渣熔化开始温度逐渐降低,但由于高炉炉渣的液相线温度基本未变,所以炉渣熔化结束温度基本未发生改变;w(Al₂O₃)为20%时,随着w(MgO)/w(Al₂O₃)的增加,炉渣中易生成熔点较高的镁铝尖晶石,导致高炉炉渣熔化开始温度逐渐增大,与此同时,炉渣液相线温度逐渐降低,导致炉渣熔化结束温度逐渐降低;随着碱度R的增加,高炉炉渣中生成了具有高熔点的化合物、炉渣的液相线温度升高,使得高炉炉渣的熔化开始温度逐渐增加、炉渣熔化结束温度逐渐升高;随着w(Al₂O₃)的增加,发生了共晶逆反应,故炉渣的熔化开始温度逐渐降低,而随着w(Al₂O₃)的增加,炉渣中键能较大的Al—O键增多,需要在更高温度下才能实现炉渣的最终熔化,即熔化结束温度逐渐增加;随着w(MgO)/w(Al₂O₃)、R以及w(Al₂O₃)的增加,炉渣熔化热逐渐增多。分析认为,随着R的增加,炉渣中有高熔点化合物的生成,熔化热增加;随着炉渣中w(Al₂O₃)的增加,炉渣中Al—O键增多,解聚破坏熔渣结构消耗的热量增多;而随着w(MgO)/w(Al₂O₃)增加,高熔点化合物的生成或熔化开始温度降低,造成熔化热增加。

Melting characteristics of blast furnace slag with high Al2O3

In order to understand the melting characteristics of blast furnace slag with high Al₂O₃ (w(Al₂O₃)≥15%), the influences of different w(MgO)/w(Al₂O₃), basicity R and w(Al₂O₃) on the melting temperature and heat of high aluminum blast furnace slag were discussed by differential scanning calorimeter (DSC). The experimental results show that the initial melting temperature (t_onset) of slag is 1 248-1 291 ℃, the end melting temperature(t_end) is 1 432-1 485 ℃, and the heat of melting is 137-211 J/g. When w(Al₂O₃)=15%, the eutectic reverse reaction occurs at high w(MgO)/w(Al₂O₃), which leads the initial melting temperature of blast furnace slag decreases. However, the end melting temperature of blast furnace slag is almost unchanged because the liquidus temperature does not change. When w(Al₂O₃)=20%, with the increase of w(MgO)/w(Al₂O₃), magnesia-alumina spinel with high melting point is easily formed in the slag, which leads to the increase of initial melting temperature of slag, meanwhile, the end melting temperature of slag decreases due to the decrease of liquidus temperature. With the increase of R, compounds with high melting point are formed in the blast furnace slag, and the liquidus temperature of slag increases, making both the slag initial melting temperature and end melting temperature increase. With the increase of w(Al₂O₃), the eutectic reverse reaction occurs, so the initial melting temperature of slag decreases. However, with the increase of w(Al₂O₃), the Al—O bond with higher bond energy in slag increases, and the final melting of slag needs to be realized at a higher temperature, that is, the end melting temperature increases. With the increase of w(MgO)/w(Al₂O₃), basicity R and w(Al₂O₃), the melting heat (ΔH) of slag increases. Among them, compounds with high melting point are formed in the slag and the melting heat increases with the increase of R. While the w (Al₂O₃) in slag increases, the Al—O bond in slag increases, and the amount of heat consumed by depolymerization of slag structure also increases. And with the increase of w(MgO)/w(Al₂O₃), the formation of high melting point compounds or the decrease of initial melting temperature is resulting in the increase of melting heat.