BENEFICIATION STUDIES OF OKABA COAL, NIGERIA

Abstract

Several researches have highlighted the benefits of using cleaned coal in improving its utilization in coal fired plants and other industrial processes in order to satisfy stringent environmental requirements. In this study, the aim was to investigate the amenability of Okaba coal to mineral beneficiation methods using heavy liquids and froth flotation. The coal samples obtained from Okaba mine was subjected to chemical and proximate analysis. Washability studies using float and sink tests were conducted on 1-3mm, 3-6mm and 6-9mm size fractions using heavy liquids of different specific gravity. Depending on the association between coal macerals and mineral matter, the process of separating low ash particles from high ash particles could be easy or difficult and was investigated using the Near gravity material (NGM) assessment. Froth flotation was performed in a laboratory Denver flotation cell under several operational factors: particle size, concentration dosage, pulp density and frother dosage to ensure optimum flotation conditions. The flotation products were quantified in terms of its combustible recovery, ash rejection and efficiency index. Chemical analyses of the coal samples indicated that on average Okaba coal contains 11.54% ash, 11.52% moisture, 43.45% volatile matter, 33.49% fixed carbon, 5.54% hydrogen, 1.45% nitrogen, 8.9% oxygen, 0.72% sulphur. The ultimate and proximate results places Okaba coal as non-coking and well suited for combustion and in power generation plants. Results from washability analysis indicated a sharp cut in the increment curve suggesting that Okaba coal can be cleaned easily with a cut density of 1.8 for ease of separation. Flotation results suggest that optimum condition for clean coal can be obtained at a particle size of -150+125microns, using a collector dosage of 78g/kg of feed, at neutral pH and a pulp density of 7.7%.