CHARACTERIZATION OF SOKOTO PHOSPHATE ROCK AND DESIGN OF PROCESS FLOWSHEET FOR ITS BENEFICIATION

By

Author

Presented To

Department of Engineering

ABSTRACT
The characterization of Sokoto phosphate rock and design of process flow-sheet for its beneficiation has been investigated and established. The samples of the Sokoto phosphate mineral ore used for the research work were sourced from mining locations in Dange-Shuni, Bodinga, Yabo, Wurno, and Rabbah Local Government Areas of Sokoto State. Chemical analysis of the Run-of-Mine sample gave 44.3%SiO2, 12.1%P2O5, 19.1%CaO, 3.9%Fe2O3, and 10.5% Al2O3 while the sorted nodules without scalping assayed 14.2%SiO2, 21.7% P2O5, 44.31%CaO, 6.19%Fe2O3, and 3.60% Al2O3. Mineralogical analysis of Sokoto Phosphate Rock using XRD showed that the material contained calcite, quartz, hydroxylapatite, flourapatite and carbonate-flouapatiteas the main associating minerals with calcite dominating. Photomicrographs of a thin section of the phosphate nodules showed that associating mineral assemblage exist in very fine association with no visible mineral grains even under the microscope. This resulted in poor separation of associating mineral through flotation due to poor liberation. Grindability test carried out on the Sokoto phosphate rock using Denver ball milling machine gave a work index of 56.7kwh/ton which is higher than the work indexes of 10.13-13.03kwh/ton for other phosphate mineral ores sighted in the literature. Size-Assay analysis conducted on scrubbed Sokoto Phosphates nodules revealed that nodules had a size distribution with 80% passing 29300μm. A density test revealed that Sokoto Phosphate nodules have a specific gravity of 2.9. Flotation Tests using AERO 704 (fatty Acid), Alkyl Hydroxamates, Melamine as collectors (alone or mixed with diesel), MIBC as frother, Calcium Hydroxide and Sulphuric Acid as pH regulators and Dextrin, Sodium Silicate and Aluminium Chloride as depressants produced poor P2O5 separation in the flotation products due to very poor liberation associated with very fine mineral grains. AERO 704 Collector gave the best result with a P2O5 recovery of 87.3% at 950g/t of reagent, 65% solid conditioning pulp density and pH of 10. Based on the results obtained from all the tests and analysis carried out on the ore, a process flowsheet was developed comprising a Scrubber fitted with a Screen Mesh of 12.7mm apertures to upgrade the ROM from 12.1% P2O5 to 24.5% P2O5 with a P2O5 recovery of 72% that will be milled to 80% passing 75μm thus producing a product with high enough P2O5 content that can be used for fertilizer production.