ABSTRACT

Since coal washeries generate huge quantities of high-ash rejects as waste, effective utilization of coal rejects help in sustainable coal preparation. Out of different coal rejects, tailings from froth-flotation process can be a potential material for the extraction of clean coal due to its fine size, availability in the slurry form, presence of good carbon values, and better liberation properties. In the present study, three different methodologies i.e., chemical method, chemico-physical method, and physical method are explored to separate clean coal with >49.8% yield for their utilization in coke making process. The chemical method of demineralization by alkali-acid leaching shows a high clean coal yield of 65.4%; however, the alteration of vitrinite-group macerals makes it unsuitable for coke making process. Chemico-physical method of clean coal separation by hydrothermal extraction followed by density separation results in clean coal at 49.8% yield with an increase in vitrinite group macerals, which shows a positive impact on rheological and coking properties. The physical separation method by ultrafine grinding followed by density-gradient-centrifugation resulted in 58.2% of clean coal yield with coking properties similar to the clean coal obtained in conventional coal beneficiation plants. By adopting chemico-physical method and physical method of coal cleaning, the overall clean coal yield of the washery can be improved by >5.1%. Also, there is no deterioration in coke properties such as coke strength after reaction and coke reactivity index by using the prepared clean coal in coal blend.

摘要

由于洗煤厂会产生大量高灰渣作为废物，因此有效利用煤渣有助于可持续的煤炭制备。在不同的煤矸石​​中，来自泡沫浮选工艺的尾矿由于其细粒度、浆料形式的可用性、良好的碳值和更好的释放特性，可以成为提取清洁煤的潜在材料。在本研究中，探索了三种不同的方法，即化学法、化学物理法和物理法，以分离收率大于 49.8% 的精煤，并将其用于炼焦过程。碱酸浸出化学法脱盐，精煤收率高达65.4%；然而，镜质组显微物质的变化使其不适用于焦炭制造过程。通过水热萃取和密度分离进行精煤分离的化学物理方法导致精煤的产率为 49.8%，同时镜质体组微量增加，这对流变和焦化性能有积极影响。超细粉碎后密度梯度离心物理分离方法的精煤产率为 58.2%，其结焦性能与常规选煤厂中获得的精煤相似。采用化学物理法和物理法洗煤，可提高洗煤厂整体精煤产率>5.1%。此外，通过在混煤中使用制备的精煤，焦炭性能例如反应后的焦炭强度和焦炭反应性指数没有劣化。