BENEFICIATION, DEPHOSPHORIZATION AND DESULPHURIZATION OF AGBAJA IRON ORE
Iron ores are used in blast furnace for the production of pig iron; Agbaja Iron ore has an estimated reserve of over I billion metric tonnes. Unfortunately, this large reserve cannot be utilized for the production of pig iron due to its high sulphur and phosphorus contents. In addition, the ore cannot be beneficiated easily like Itakpe and Oshokoshoko iron ores because of its texture. This work studied the beneficiation, dephosphorization and desulphurization of Agbaja iron ore. The raw ore was beneficiated using several techniques namely; oil agglomeration technique, rapid magnetic separation technique, Humphrey spiral technique, froth flotation technique and jigging table technique. Chemical leaching, bacteria leaching and pyrometallurgical methods were used to reduce the phosphorus and sulphur contents of the ore. Hydrochloric acid, sulphuric acid and nitric acids of different concentrations were used at various leaching times, acid concentrations and particle sizes. The parameters varied in bacterial leaching include bacterial loads and leaching time. Atomic Absorption Spectrophotometer, X-ray fluorescence spectrophotometer, Digital muffle furnace and Absorbance-concentration technique were used for experimentation and chemical analysis. Central composite design technique was applied to obtain optimum conditions of the processes. Surface response plots were also obtained. Oil agglomeration technique was adjudged the best beneficiation technique with an iron assay of 67.05%. The percentage degrees of dephosphorization and desulphurization were found to increase with increase in acid concentration and leaching time and a decrease in particle size for the three acids. The experimental results for percentage removal of phosphorus for HCl, H2SO4 and HNO3 were 98.12%, 99.56% and 98.55% respectively, while that of sulphur were 85.56%, 87.77% and 84.44%. The optimum % removal of phosphorus from the model for HCl, H2SO4 and HNO3 were 97.97%, 99.87% and 99.74% respectively and that of sulphur were 89.66%, 87.73% and 84.94%. Results obtained using bio leaching showed that percentage degrees of biodephosphorization and biodesulphurization depended on the bacterial load and leaching time and passed through a maximum with increase in leaching time. The experimental results for % removal for phosphorus for mixed Colony, Colony I, Colony II, Colony III, Colony IV, and Colony V were 86.00%, 81.01%, 82.28%, 81.01%, 82.28% and 81.01% respectively and that of sulphur were 99.88%, 99.78%, 99.78%, 99.78%, 99.89% and 99.78% respectively. Also the optimum percentage removal of phosphorus using mixed Colony, Colony I, Colony II, Colony III, Colony IV, and Colony V were 94.86%, 90.91%, 92.21%, 90.91%, 92.02% and 90.91% while that of sulphur include, 99.94%, 99.99%, 99.43%, 99.43%, 99.93% and 99.43%, respectively. Critical observation of the results showed that there was no remarkable difference between the experimental values and CCD model values confirming the authenticity of the CCD models. The result of this work has shown that Agbaja Iron Ore if properly processed can be used in our metallurgical plants and also can be exported since phosphorus and sulphur contents of the ore have been reduced drastically.