FREMGANGSMAATE FOR ANRIKING AV KALKHOLDIG FOSFORITT SOM IKKE ER MAGMATISK VED ANRIKING AV DENS P2O5-INNHOLD OG REDUKSJON AV DENS KADMIUMINNHOLD

摘要

The present invention relates to a method for beneficiation of phosphate rock by a thermal treatment, wherein an appreciable increase in P.sub.2 O.sub.5 and decrease in cadmium contents in the calcined product are achieved. According to the invention, the phosphate rock is contacted with hot gases possessing a temperature in the range of between 700. degree. C. to 1600° C. for a period of below 60 seconds and subsequently the fines are removed by a conventional classification method thus obtaining an up-graded phosphate product with a relatively low cadmium content. The up-graded phosphate product is also characterized by a relatively low sulfide content as well as low organic matter, which are very advantageous in the phosphoric acid manufacture therefrom. One of the advantages of the method is the almost complete recovery of the P.sub.2 O.sub.5 present in the phosphate rock since no slaking for calcium oxide removal is utilized.