PILOT-SCALE STUDIES USING A HYDROCYCLONE AND FROTH FLOTATION FOR THE PRODUCTION OF BENEFICIATED COAL FRACTIONS FOR IMPROVED COAL-LIQUEFACTION

Kilogram quantities of coal fractions were produced using pilot-scale density and froth flotation methods. In the density separations a dens e-liquid hydrocyclone was used with calcium nitrate solution as the de nse medium. Three coals were used in the study: Point of Ayr, Blidwort h and Bilsthorpe, and the coal fractions produced were liquefied in a 2 L autoclave using a hydrogenated anthracene oil solvent. For froth f lotation, studies were carried out on Bilsthorpe coal using a laborato ry flotation column and a Jameson cell and the final concentrates were liquefied in the 2 L autoclave. The hydrocyclone separations showed d ifferent yields of overflow and underflow for different coals and henc e optimization of the separation density is required for each coal. Di gestion in the 2 L autoclave of the overflow samples showed significan t increases in overall conversion and oil production compared with the original feed coal. Pilot-scale tests with column flotation and a Jam eson cell indicated that they were effective in producing a final conc entrate with a vitrinite-rich fraction. These fractions showed increas ed overall conversion in the 2 L autoclave and increased oil productio n. For Bilsthorpe coal, the liquefaction products from the final conce ntrate of the flotation cell were very comparable with those from the hydrocyclone separation. The results show that beneficiation processes such as these could be applied at full scale and that, within the tot al coal complex, the production of the overflow fraction could be opti mized and the much smaller underflow fraction then directed to gasific ation and combustion reactors. (C) 1997 Elsevier Science Ltd.