Mahmoud Motasim

This study was performed on disseminated low-grade chromite ore, Gedarif State, Umm Saqata-Qala Elnahal, to treatment the ore by Heavy media separation (HMS) with low intensity magnetic separation (LIMS) for course fraction size (-212+75) μm and selective flocculation for chromite slimes (-75) μm. The ore of the study area is low grade contains 21.5% Cr2O3 with the liberation size of chromite mineral in the range (0.30-0.05) mm. The main gangue of the ore is mineral silicates as the Antigorite mineral. The ore was crushed, ground, and then classified to tow fraction size (-212+75) μm and slimes (-75) μm. Fractions size (-212+75) μm contained 25.58% Cr2O3 was treated by HMS via Bromofrom mixed with carbon tetrachloride flowed by low intensity magnetic separator. HMS with LIMS obtained the highest recovery 82.52% and grade 46.62% Cr2O3 for chromite concentrate with 2.54 Cr/Fe. The slimes (-75) μm contained 22.17% Cr2O3 was treated by selective flocculation method. Optimum grade 42.71% Cr2O3 and recovery 37.10% for chromite concentrate, were achieved at sodium silicate concentration 100 mg/l, starch concentration 45 mg/l, pH=9, and solid percentage 5%

High grade chromite ore has been decreased constantly due to the importance of chromium element in industrial uses such as metallurgical, chemical, and refractory industries. Therefore, beneficiation of low grade has been more significant .Response Surface Methodology (RSM) is combination of statistical and mathematical methods used for modeling and analyzing problems. In this study, the Central Composite Design (CCD) was applied by using Design-Expert (version 6.0.5) for modeling and optimizing the effect of operating variables on the performance of gravity separation via pilot plant shaking table for chromite ore. Three operating variables were studied, namely feed rate, tilt angle, and flow rate during the tests. The sample under study is low grade chromite ore, containing (30.21%, Cr2O3). The mathematical model equations of ANOVA model revealed that the grade of concentrate is more sensetive for feed rate (g/min) compered to water flow rate (l/min).whereas , recovery of concentrate is more sensetive for tilt angle compered to water flow rate (l/min) and feed rate (g/min). Optimized responses for the beneficiation process were found at concentrate with 48.52% Cr2O3 in with 83.09% recovery and it was achieved at water flow rate 15.33 l/min, tilt angle 2.16 ≈ 2.00 degree, and feed rate of 195.38 g/min

This study was carried out on the low-grade chromite, Gedarif state, Sudan, at Umm Saqata- Qala Elnahal to achieve full characterization for the ore via Microscopic studies for the polish section samples, X-ray diffraction analysis (XRD), X-ray Fluorescence Analysis (XRF), Scanning electron microscopic with Energy Dispersive X-ray Spectroscopy (SEM-EDX), and physical properties tests. Microscopic study revealed that the liberation size of chromite mineral is in the range (0.30-0.05) mm. also the X-ray diffraction, X-ray fluorescence and scanning electron microscope with the Energy Dispersive X-ray analysis showed that main gangue of the ore is mineral silicates as Antigorite and contains 21.58-19.60% Cr2O3. The physical tests (saturated density and dry density) demonstrated that ore has low density in range 2.54-2.38 g/cm3 because it is low grade chromite ore, this can be attributed to the dominating mineral silicate (waste) which associated with chromite mineral.