Laboratory and pilot plant flotation studies on settling pond coking coal fines and its utilization for metallurgical purposes

Most of the Indian coking coal washeries were installed during the period 1960-1980 where the design of the washery was based on relatively easy or moderately difficult washing coking coals, mined in the eastern and western part of Jharia coalfields. The coal fines below 0.5 mm were not processed and though enriched in vitrinite content, nowadays the fines cannot be mixed directly with clean coal due to their high ash content (more than 25%) and of high percentage of silica content. Due to an increase in opencast mechanized mining of coals, quality of the coal fines deteriorated and they need to be beneficiated before blending with the coarse coals. Some of the washeries installed fine coal treatment plants, but due to varied reasons these circuits were not operated as a result, huge quantity of unwashed coal fines is left as such and discharged to nearby ponds or lagoons, and in the process they had been accumulated in adjoining settling ponds causing environmental pollution and are being sold to domestic market for use in non-metallurgical purposes. The coking coal fines constitute vitrinite content, which is a vital ingredient for metallurgical purpose. Hence, if these coal fines are beneficiated, they may add to the overall quality of the clean coal. In this paper attempt has been made to beneficiate the accumulated coal fines through laboratory flotation tests vis-à-vis pilot plant studies to generate maximum amount of cleans from settling pond coal fines suitable as blend for metallurgical coke making