Abstract
The conversion of insoluble phosphorous minerals such as apatite, Ca5(PO4)3(F, OH, Cl), to phases containing phosphorous in soluble form is an essential step in the production of fertilizer grade phosphates. Developing countries lack the capital-intensive industrial base necessary to create a phosphate industry. We examine a process suitable for use in Sri Lanka which uses mainly indigenous raw materials. In this process, a chlorine-rich apatite is fused with Na2CO3 and SiO2 at 900° C and 1300° C for 1 to 2 h to yield a product having >90% available phosphorous. Data necessary for the technological evaluation of the process are presented. Phase equilibria in the lime-rich portions of the system CaO-Na2O-P2O5-SiO2 have been studied. The section Ca3(PO4)2-Ca2SiO4-CaNaPO4 is shown to be a ternary system, and phase relations on the 1100° and 1300° C isothermal sections are presented. A reconnaisance of the system CaO-Ca3(PO4)2-Ca2SiO4-CaNaPO4 has been made. These data, combined with studies of the kinetics of the reaction, point to regions of composition and reaction conditions favouring high yields of available phosphorous.
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Gunawardane, R.P., Glasser, F.P. Reaction of chlorapatite, Ca5(PO4)3(Cl, F) with sodium carbonate and silica. J Mater Sci 14, 2797–2810 (1979). https://doi.org/10.1007/BF00611458
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DOI: https://doi.org/10.1007/BF00611458