GB596788A - Improved process for the manufacture of granulated superphosphate - Google Patents

Abstract

<PICT:0596788/III/1> Superphosphate is manufactured by introducing a thick slurry of finely divided phosphate rock and sulphuric or phosphoric acid or a mixture thereof, together with superphosphate fines, into a conditioning or nodulizing zone, drying the nodulized material, and subjecting the dried material to forced cooling. A superphosphate containing from 20 per cent. to 48 per cent. available P2O5 may be produced, or only 80 to 90 per cent. of the acid used in the manufacture of a 20 per cent. availible P2O5 superphosphate may be employed. As shown, the acid and rock dust are mixed in mixer 1 provided with an exhaust fan 4, the slurry being discharged on to conveyer belt 7 on a thin layer of superphosphate fines from conveyer &c. 8. The slurry and fines pass to conditioner and nodulizer 10 and on passing through, the mixture is sprayed with water from sprays 11. The interior is illuminated by a flood light 14. The discharged nodules pass to a drier 16, being therein subjected to combustion gases from burner 18, which gases are discharged by fan 20. The material is then cooled in cooler 22 by a counter current of air drawn in by fan 24, and passes to classifying screens 27, 28. Oversize particles pass to a grinding mill 29 and return to the screens via conveyer 30, and the fines via conveyer 8 to belt 7, or even directly to the conditioner 10. Alternatively, the fines may be separated pneumatically into a fine fraction and a coarse fraction, the former being passed to the conditioner and the latter to the mixer. The superphosphate may be employed for the manufacture of phosphoric acid by the process of Specification 549,487. Specifications 530,244 and 559,482 also are referred to.