Application and Utilization of the Enviro-Clear Thickener in a U.S. Steel Coal Preparation Plant

During 1972-1973, U.S. Steel acquired an existing southern West Virginia high volatile coal mine property including a 150 tph heavy media feldspar jig preparation plant. Expansion of production from the property required an increase in plant capacity to 300 tph, replacement of the feldspar jig with a hydrocyclone circuit, and inclusion of a water clarification thickener system. The rugged and restrictive nature of the terrain adjacent to the plant facility indicated prohibitive construction costs and severe site congestion would be encountered if a conventional water clarification thickener were installed. A high-loading, small-volume thickener, developed initially for the sugar beet industry by the Enviro-Clear Co. of New York, was investigated by U.S. Steel Research for possible coal preparation application, utilizing bench scale and small scale pilot plant evaluation methods. Results of testing at existing U.S. Steel preparation plants indicated predictable successful application of the Enviro-Clear thickener, so a 35-ft-diam unit was installed. The two-phase thickener system, utilizing presettled bottom sludge as a filter-clarification media, has successfully performed since commissioning in April 1973, producing clarified water competitive with conventional thickener systems with freedom from usual thickener operational problems.