Otisca Process: A Pilot Plant Study of Dense Liquid Separation

摘要

The Otisca Process for cleaning coal is based on gravity separation of the feed in a dense medium separator. The parting liquid is a fluorocarbon of low boiling point, low latent heat of vaporization and high density (1.5 g/cm exp 3 ). The parting liquid is recovered from the product coal and reject and recycled to the process. Due to the low latent heat of vaporization of the fluorocarbon, (77.5 Btu/lb at 77 exp 0 F) in comparison to water (971 Btu/lb at 212 exp 0 F) the energy required for the operation of the evaporators is much reduced. No pre-screening of the feed is necessary and the very low viscosity of the fluorocarbon parting liquid results in much shorter separation times than are observed with magnetite suspensions. The distribution curves for the Otisca Process based on an eight-hour test run at Otisca's pilot plant located in Florence, Pennsylvania is reported. The feed was 3/8'' x 1.4'', 1/4'' x 28m, 28m x 100m and 100m x 325m size fractions from a full washability study of the feed, product and reject collected during steady state operation. Probable errors, Epm, error areas and organic efficiencies were calculated from the data. For a 3/8'' x 325m feed, the probable error was 0.023 at a 1.49 sp gr of separation. The corresponding organic efficiency was 98%. Based on sharpness-of-separation criteria, the Otisca Process is superior to others utilizing heavy media cyclones, hydrocyclones and concentrating tables. Further testing is recommended to determine the effect of operating conditions such as feed rate, size consist and moisture content on separation efficiency so that a more extensive data base is available for design purposes. No attempt was made to evaluate freon losses or process economics. (ERA citation 06:015268)