چكيده انگليسي :
Magnetite is the main source and raw material in the iron and steel industries. With the reduction of high-grade iron ore reserves in the world and the rapid growth of demand in global markets for a product with the lowest impurities, the processing of low-grade iron ores and preventing its lose has become a significant issue. At lines 6, 5, and 7 of Gol Gohar Mining and Industrial Complex, the feed tonnage in flotation was 960 t/h, and the floatation tailings tonnage was 47 t/h with an average iron grade of 50.2%. This resulted in a loss of 20 t/h of iron metal. In this study, to identify the iron phase and reduce its loss, sampling was performed on the feed, floatation tailings, and concentrate. The samples were subjected to Davis tube test, mineralogical studies, and grade analysis. The results showed a high mass recovery of the magnetic part, i.e. 75-80%, which indicated that a lot of iron was transferred to the tailings and was wasted. According to the mineralogical studies on the flotation tailings, it was found that the wasted iron was mainly magnetite in addition to pyrite which is the gangue mineral, and the degree of liberation of magnetite was 76%, indicating a relatively low interlocking between pyrite and magnetite. Also, in these lines, the tonnage of feed of flotation was 960 t/h and the tonnage of floating tailings was 47 t/h with an average iron grade of 50.2, which confirms the lose of iron. To investigate the effect of the degree of liberation on flotation, the particle size was reduced from 100 microns (as in the plant) to 45 microns by a rod mill, and the flotation test was performed on this 45-micron sample under plant conditions. The results of this test showed that the grade of magnetite in the tailings decreased by 13 percentage points compared to the plant and by 10% compared to the experimental flotation test using plant conditions. After that, the wash water was used. By using wash water, the level of iron in the tailings decreased from 50 to 36%. As supplementary tests, 20 flotation tests on feed and 20 flotation tests on plant tailings were designed and conducted. The condition was 100 g/ton of collector, 40 g/ton of frother, 400 g/ton of dextrin, and with a particle size of below 45 microns. As a result, the recovery of the magnetic portion by the Davis tube fell from 80 to 55%. As a final step, wash water was added, which decreased the recovery of the magnetic fraction from 70% to 44%. As a result of this study, a 26% decrease in magnetite wastage, an 8% decrease in the iron grade of tailings, and an 11% decrease in the magnetite grade of the tailings were obtained. According to the results of the experimental design, the use of sodium hexametaphosphate dosage of 200 g/t, frother dosage of 60 g/t, collector dosage of 150 g/t, particle size of 75 microns and dextrin dosage of 200 g/t are the best conditions for reducing magnetite in tailings. Also, the use of 200 g/t sodium hexametaphosphate, 60 g/t frother, 150 g/t collector, particle size of 75 microns, and 200 g/t dextrin are the best conditions for reducing sulfur in the concentrate. Furthermore, the supplementary flotation tests on the tailings indicated that the use of 150 g/t sodium hexametaphosphate, 80 g/t frother, 400 g/t collector, particle size of 66 microns, and 150 g/t dextrin are the best conditions for the magnetite recovery from the plant flotation tailings.
