METHOD FOR CURTAILING PHOSPHOROUS IMPURITY IN THE PRODUCTION OF SMELTER GRADE ALF.SUB.3

摘要

In the generation of hydrogen fluoride gas for the product of AlF3 by the reaction of fluorspar with concentrated sulphuric acid a small amount of aluminium sulphate is introduced into the reactive mix to assist in the retention of phosphorous compounds in the solid residues of the reaction and thus reduce the phosphorous content of the gaseous HF. Aluminium sulphate may be added as alum or may be generated in situ in the sulphuric acid by addition of an alumina hydrate, preferably before the acid is brought into contact with fluorspar. The addition of a small amount of calcium carbonate to the fluorspar also improves retention of phosphorous compounds in the solid residues in some instances.