GB1023119A - Improvements in or relating to the beneficiation of phosphate ores - Google Patents

Abstract

1,023,119. Separating solids; crushing ores. W. R. GRACE & CO. Sept. 22, 1964 [Oct. 10, 1963; Oct. 11, 1963], No. 38657/64. Headings B2A, B2H and B2J. Phosphate ore is beneficiated by thermally drying a phosphate matrix while simultaneously attriting it in a substantially vertical attrition column, pneumatically classifying the dried matrix to produce pebble phosphate and fine particles of phosphate rock, silica and agglomerated clay, and separating the pebble phosphate from the fine particles. The fine particles of phosphate rock are then separated from the fine particles of silica and agglomerated clay and are subsequently recovered as a phosphate concentrate product. The matrix is fed, via a line 2 and a hopper 1 to an attrition column 3 below which is a fluidized bed chamber 16. A hot gaseous fluid, inert to the matrix and preferably at a temperature of 175 ‹C. and at a velocity of approximately 3500 cm. per sec., is caused to flow through the column 3 to dry the matrix and to effect preliminary classification thereof into a -1À9 cm. fraction which is forced into a disintegration chamber 4 and a +1À9 cm. fraction which falls into the chamber 16. The chamber 4 may be in the form of an impingement chamber, a Jordan mill or a ball mill. The -1À9 matrix is then forced into a scrubber collector 5 (e.g. of the centrifugal type) where it is pneumatically separated into fine and coarse fractions (e.g. -200 and +200 mesh). The fine fraction is conveyed to a second scrubber collector 13 wherein fine claylike material is recovered and removed through a line 15, the gases from the collector being wet scrubbed and exhausted to atmosphere through a line 14. The coarse fraction passes to a dry screen separator 6 and is separated into a +14 mesh final product pebble phosphate which is removed through a line 7 and into -14 mesh material which is taken to a second screen separator 9 wherein it is divided into a -14 to +35 mesh fraction which is transferred to a table flotation device 10 and a -35 to +200 mesh fraction which is taken to a double cell froth flotation device 22, 25. In the device 10 the fraction is treated with anionic flotation reagents, e.g. a mixture of fatty acids, kerosenes, fuel oil and caustic soda, a phosphate concentrate product being removed through a line 11 and a waste product, essentially siliceous material, being discharged through a line 12. In the cell 22 the fraction is treated with a similar reagent, which may however not contain kerosene, and a siliceous waste product is removed at 24, a fraction of substantially concentrated phosphate is removed at 23, cleaned with sulphuric acid to remove oil and traces of fatty acids, washed and conveyed to the cell 25 wherein amines are added as reagents. The particles are divided into a siliceous waste product removed at 27 and a phosphate rock concentrate at 26. The phosphate concentrate may be recycled and reprocessed by the flotation treatment to increase the P 2 O 5 content. The table of flotation operation may be eliminated from the process. Any phosphate matrix not sufficiently disintegrated in the attrition column 3 and the fluidized bed chamber 16 passes to a dry screen 18 where it is separated into a +1À9 cm. fraction removed as a final product through line 21 and a -1À9 cm. fraction which is recirculated via a line 19 to the feed hopper 1. In another embodiment, instead of using a flotation process to treat the -14 mesh fraction passing from the screen separator 9, this fraction is led to an electrostatic separator where it is divided into a phosphate rock product and into a waste product comprising the silica and agglomerated clay. The separator may also produce a middling product which is recirculated to the separator itself or to the feed hopper 1.