Upgrading of phosphate ore

A method for upgrading unground low grade phosphate ore to remove slimes therefrom and provide a phosphate ore suitable for acidulation which comprises the steps of:

• (a) contacting unground phosphate ore with phosphoric acid having a concentration of about 1 to 20 weight percent in an amount of about 2 to 10 parts of phosphoric acid per part of phosphate ore in a desliming unit to form a suspension containing the slimes and the phosphate ore;
• (b) removing the suspension to a solids separator and separating phosphate ore slurry solids from the suspension containing the slimes;
• (c) passing the phosphate ore to a grinding unit and grinding the phosphate ore solids in the presence of a weak phosphoric acid solution to provide a phosphate rock slurry suitable for acidulation;
• (d) removing the suspension containing the slimes and flocculating the slime solids to cause precipitation of the slime solids and provide separation between the slime solids and the phosphoric acid process liquids;
• (e) removing the resulting mixture to separation means and separating the slime solids from the process liquids;
• (f) recycling at least a portion of the process liquids to the desliming unit and at least a portion to the grinding unit;
• (g) removing the slime solids and reacting with weak phosphoric acid to acidulate finely divided phosphate rock contained therein and form a reaction mixture;
• (h) removing the reaction mixture to a separation device and separating the slime solids from the process liquids;
• (i) washing the slime solids with water, combining the wash water with the process liquids and recycling to be combined with the process liquids recovered from the separator in step (e);
• and
• (j) recovering the slime solids which contain P.sub.2 O.sub.5 values.