Multistage Mineral Acid Leaching De-Mineralization of a Medium Caking Coal
contents that are less than 12% and 0.8% respectively. Preliminary test on Chikila coal gave high ash and sulfur contents of about 14.90% and 1.68%, the objective is to de-mineralize it using mineral acid. Sample of Nigerian Chikila coal obtained at a depth of about 4.5 m was air dried, crushed and pulverised. Fractions of - 425+300 μm and -75 μm were leached with dilute hydrochloric acid using 24 factorial variables combination. Three multistage leaching were conducted. The filtrates and coal concentrate obtained were analysed using UV spectrophotometer and particle induced X-ray emission (PIXE) analyser, respectively. Sieve analysis showed a cumulative oversize of 63.3% at 600 μm mesh size, while the remaining 36.7 % were distributed on the lower sieves. The proximate analysis of the sample as-received gave moisture, volatile matter, ash, sulphur and fixed carbon percents 4.70, 42.12, 12.6, 1.68 and 40.58, respectively. The multistage leaching of -75 μm fraction using H2O-HCl-H2O sequence produced a coal concentrate with moisture, volatile matter, ash, sulphur and fixed carbon percents of 3.85, 34.52, 8.13, 1.02 and 53.50, respectively. This translates to a decrease in ash, sulphur and volatile contents of 35.48, 39.29 and 18.04 % and an increase in carbon content of 24.15 %. A successful upgrade of the leaching to pilot scale will make the coal available as a blend component for economical industrial cokemaking.
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