Separation of Particulate Solids of Varying Densities in a Fluidized Bed.
U S Pat 3 774 759 1973 Nov; :
A particulate feedstock is separated into a light fraction and a heavy fraction by feeding it into a fluidized bed of particulate material whose particle size and specific gravity, relative to the particle sizes and specific gravities of said light and heavy fractions, are such that one of these fractions readily stratifies into an easily removable layer in the bed while the other fraction tends to remain intermixed with the bed material rather than stratifying. Said other fraction is removed as product from the bed while it is in said intermixed condition. Thus, an impure ground coal (30 pct impurities; coal, 1.35 Sp gr; impurities, 2.6 Sp gr) having a particle size of 50 pct in the range 3/8 in to 1/4 in, 25 pct in the range 6 to 8 U.S.S. Mesh and 25 pct in the range 14 to 30 U.S.S. Mesh was fed into a fluidized bed of magnetite (200-300 U.S.S. Mesh) being fluidized with air at 2.1 Ft/min. The coal was maintained in the bed for 5 min. Prior to product withdrawal, the bed consisted of 1.8 Wt pct coal feedstock and 98.2 pct magnetite. Purified coal then drawn off at a bed height of 60 pct contained 2.9 pct impurity, and was equal to 83.7 pct of the potentially clean coal in the feedstock. When the experiment was repeated and the coal product was drawn off at a bed height of 66 pct, 90.7 pct of the potentially clean coal in the feedstock was recovered containing 3.8 pct impurity.
U.S. Pat. 3,774,759, Nov. 27, 1973, Chem. Abstr. Not Found