生物质松木锯末中低温还原高铁拜耳法赤泥

对生物质松木锯末和烟煤还原焙烧高铁拜耳法赤泥进行对比试验研究,包括还原温度、还原时间、还原剂用量对还原效果的影响.生物质松木锯末还原高铁拜耳法赤泥所需还原温度低而且还原时间短最终还原效果较好.试验通过热分析和X射线衍射、动力学研究结果揭示出生物质松木锯末中低温还原高铁拜耳法赤泥机理.同时确定了生物质松木锯末中低温还原的最佳还原条件.研究表明生物质松木锯末为赤泥质量分数的20%,还原温度为650℃,还原时间为30 min可将赤泥完全磁化.生物质松木锯末热重试验分析表明250~375℃温度区间为锯末热解的主要阶段,350℃左右热解速率达到最大,450℃后热解反应趋于平缓;烟煤热重试验表明300~700℃温度区间为烟煤热解的主要阶段,450℃左右热解速率达到最大,650℃后热解反应趋于平缓.动力学研究表明锯末在300~400℃区间热解表观活化能比烟煤热解表观活化能要低很多,说明在此温度范围内锯末比烟煤更加容易发生热解反应.生物质能够中低温还原高铁拜耳法赤泥,还原温度比煤基还原的还原温度低200℃左右. 

Medium-low temperature reduction of high-iron Bayer process red mud using biomass pine sawdust

An experiment was conducted to determine the difference between using biomass pine sawdust and pulverized coal in the reduction roasting of high-iron Bayer process red mud from the perspective of reduction temperature, reduction time, and reducing agent dosage. Experimental results show that biomass pine sawdust reduction roasting is quicker, occurs at a lower temperature, and is a superior process to pulverized coal reduction roasting. The mechanism of using biomass pine sawdust in reduction roasting of high-iron Bayer process red mud at a low temperature was investigated using thermal analysis, X-ray diffraction, and dynamic analysis. In addition, the optimum conditions involved in reducing high-iron Bayer process red mud were determined using biomass pine sawdust at medium and low temperatures. It is found that when using 20% biomass pine sawdust in mass at a reduction temperature of 650℃ and a reduction time of 30 min, the high-iron red mud in the Bayer process can be completely magnetized. A thermogravimetric experiment conducted on biomass pine sawdust indicates that the main stage of sawdust pyrolysis occurs within a temperature range of 250-375℃. The pyrolysis rate reaches a maximum at about 350℃, but tends to be gentle at 450℃. The main stage of pulverized coal pyrolysis occurs at 300-700℃; the pyrolysis rate is at its maximum at 450℃ but it tends to be gentle at 650℃. The kinetic study shows that at a temperature of 300-400℃, the apparent pyrolysis activation energy of the sawdust is much lower than that of pulverized coal, indicating that sawdust is more prone to pyrolysis than pulverized coal at this temperature range. In summary, biomass reduces high-iron Bayer red mud at a lower temperature, which is about 200℃ lower than that of coal-based reduction.