PRODUCTION OF CITRATE SOLUBLE PHOSPHATES BY CALCINATION OF SECONDARY PHOSPHATE SOURCES WITH A SODIUM-SULFURIC COMPOUND

摘要

A method of calcination is suggested, comprising: providing a raw material comprising whitlockite Ca9(Mg,Fe2+)[PO3(OH)l(PO4)6], and/or iron phosphate FePO4, and/or aluminium phosphate A1PO4 and/or fluorapatite Ca5(PO4)3F; providing an alkaline- sulfuric compound as an additive; and calcining a mixture of the raw material with the additive to obtain a product, comprising a citrate soluble phosphate compound. Further, a citrate soluble phosphate compound obtained from a P-containing raw material, methods of use of the product and of the citrate soluble phosphate compound, e.g. as a fertilizer, and a method for obtaining a fertilizer are described.