Abstract
Among the deleterious impurities in phosphate rock, dolomite is the most troublesome. Dolomite causes higher consumption of sulfuric acid, reduces filtration capacity, and lowers P2O5 recovery in the fertilizer manufacture process. Almost 50% of the future phosphate reserve in Florida are contaminated by dolomite. In 1994, FIPR conducted a comparative evaluation on five seemingly promising flotation processes for separating dolomite from phosphate. None of the processes evaluated proved to be a viable solution to the dolomite problem, with two failing to produce a concentrate of less than 1% MgO and all giving pool phosphate recoveries ranging from 30-60%. Building on their 30-year experience in dealing with dolomitic phosphate deposits in China, CLDRI (The Chinese Lianyungang Design and Research Institute) developed a complete processing flowsheet for the dolomitic pebbles in Florida. In this process, the sample is ground to liberate dolomite phosphate. The ground slurry is subject to dolomite flotation using a mixture of H3PO4 and H2SO4 as pH modifier and a fatty acid soup-based dolomite collector. The sink product of dolomite flotation can be beneficiated by either silica or phosphate flotation. Extensive laboratory testing demonstrated the technical and economic feasibility of the new process, achieving concentrates analyzing >31% P2O5 and <1% MgO with an overall phosphate recovery of more than 80%.
Gu Zhengxing - Lianyungang Design and Research Institute; Gao Zhizhong and Chaucer L. Hwang - IMC-Agrico Company