含钒石煤脱碳焙烧过程温度变化规律及焙烧条件影响

含钒石煤是我国储量巨大的一种钒矿资源。对于含碳量高的石煤原矿,脱碳焙烧工艺能在提高钒浸出率的同时降低酸耗。对石煤脱碳焙烧过程的温度变化进行研究,避免高温烧结的同时还可利用其自身热量,这对提高焙烧过程热利用效率具有重要意义。本文在650℃、50 min、空气流量500 mL/min及20%O_(2)浓度的最佳焙烧条件下,对石煤悬浮焙烧的全过程进行系统分析和研究。在最初3.9 min内,样品迅速由室温升温至560.1℃;持续加热至10.3 min,白云石和高岭石分解,样品温度升至最高值741.5℃;燃烧结束后,样品温度回落,并稳定在622.5℃。这表明脱碳主要发生在最初的30 min内,石煤中碳质燃烧可将物料自身温度提高约120℃。基于此得到了含钒石煤脱碳焙烧过程的温度变化规律。因此,在石煤脱碳焙烧中应利用其温度变化规律,在避免高温和高氧引起的局部烧结的同时,利用自身燃烧热量,以提高焙烧效率和热利用率。

焙烧脱碳对含钒石煤相变及浮选行为的影响

湖北某高钙云母型含钒石煤中矿物被碳质深度浸染,浮选前需要焙烧脱碳。通过热重-差示扫描量热(TG-DSC)、傅里叶红外光谱(FTIR)、X射线衍射(XRD)等分析测试手段对原矿及不同温度焙烧脱碳样进行了表征分析,探讨了不同温度脱碳对浮选行为的影响。结果表明,该含钒石煤随着焙烧温度的升高,依次发生黄铁矿氧化、碳质的燃烧、方解石的分解等反应。600~700℃,碳质和黄铁矿基本消失,云母八面体结构未被破坏,方解石部分分解,固硫后剩余的CaO使浮选矿浆pH值升高,Ca^(2+)浓度增大。浮选试验结果表明,随焙烧温度的提高,碳质逐渐脱除,矿物表面性质差异扩大,脱碳样的浮选效果比原矿有明显改善。650℃脱碳样浮选,由于Ca^(2+)的活化作用,石英被油酸钠捕收,可得产率为21.10%,V_2O_5品位为0.36%的尾矿产品,钒损失率仅为10.05%,精矿的V_2O_5品位为0.95%。700℃脱碳时,矿浆过高的pH值和Ca^(2+)含量使微细颗粒发生无选择性聚沉,消耗大量的油酸钠,不利于浮选的进行。

Vanadium recovery from stone coal through roasting and flotation

A new process for vanadium recovery from stone coal by roasting-flotation was investigated based on the mineralogy. The process comprised four key steps： decarburization, preferential grinding, desliming and flotation. In the decarburization stage, roasting at 550 ℃ effectively avoided the negative effect of the carbonaceous materials in raw ore and generation of free CaO from calcite decomposition during roasting. Through preferential grinding, the high acid-consuming minerals were enriched in the middle fractions, while mica was enriched in the fine and coarse fractions. Through flotation, the final concentrate can be obtained with V2O5 grade of 1.07% and recovery of 83.30%. Moreover, the vanadium leaching rate of the final concentrate increased 13.53% compared to that of the feed. The results reveal that the decarburization by roasting at 550 ℃ is feasible and has little negative impact on mica flotation, and vanadium recovery from stone coal is conducive to reducing handling quantity, acid consumption and production cost.