Preliminary study of correlations between fine coal characteristics and properties and their dewatering behaviour

The dewatering performance of 25 fine coal samples taken from 21 Australian coal preparation plants has been studied. Coal equilibrium moistures, surface properties, quantity of superfine particles, mineral matter and water properties influence the behaviour of filters or screen bowl centrifuges more directly than do any other coal properties. The equilibrium moisture, ranging from 1.3 percent to 5.8 percent, has a strong influence on filter cake moisture, but a weak effect on product moisture from screen bowl centrifuges and other fine coal centrifuges. The surface properties of coal samples were analysed by gas (N) adsorption. Specific surface area is usually less than 2.0 m/g for coal samples. The total pore volume is in the range of 0.0013 to 0.0121 cclg. These surface properties appear to have a significant correlation with the centrifuge product moisture rather than filter cake moisture. The quantity of superfine material (-0.063 mm), is strongly correlated with the product moisture of screen bowl centrifuges, while the measured zeta potential is significantly correlated with the filter cake moisture. Kaolin appears to have a much stronger effect on filter cake moisture than do any other ash minerals. Water conductivity and total dissolved solids in fine coal samples varied over wide ranges: from 1050 to 9960 μS/cm and from 852 to 7380 mg/l respectively. Surprisingly, both parameters are found to have quite a strong influence on filter cake and centrifuge product moisture. The product moisture increases as the water conductivity and total dissolved solids in the water increase