SBM Mining Company adopts the stage-wet grinding ultrafine mill process, it uses two to one grinding process with two one-stage ball mill against one one-stage ball mill. Grinding and wet magnetic separating the crude concentrate of 25% grade, finally we can get 66.00% grade iron ore concentrate. The cost is lower than 200 yuan per tonne. Beijing Science and Technology University is performing a process test of a certain ultra-poor magnetite. It is found that the crude ores can discard 75.66% qualified gangue after the wet pre-selection. In this way, only one fourth of the ores are going to enter the subsequent operation, which has greatly alleviated the follow-up operation load. Coarse grinding adopts the drum sieve and mill to construct the closed-circuit.
When the dissemination size of the gangue minerals is smaller, this can crush minerals to the smallest, adopting the discarding the tailing during wet ultrafine mill. Many experimental results prove that, the effect of the pre-selection discarding tailing of coarse grains (above 10mm) is very bad. The grade is less than 2% when using the dry ultrafine mill to discard 10% of the tailings, and the loss of the magnetic iron is over 3%. Thus the single adoption of this method is not able to resolve the problem. In 2004, SBM Mining Machinery Company carried out a research into the high-pressure roller semi-industrial test as well as the sorting test of the rolling mill products. Conducting the discarding tailings of the magnetic pre-selection for the 3to 0mm products with 26.27% grade, thus the qualified tailings of 47.80% productivity and 8310/e grade can be pre-discarded. We can say that this research has opened up a fresh new situation for the utilization of the ultra-poor iron ore in our country. In order to realize the pre-selection discarding of tailings of the ores, promote the grinding grade largely, improve the ore processing capacity at the same time and reduce the grinding and selection operation cost, SBM has made a breakthrough through trial and error as well as in-depth exploration, viz. adopting the closed circuit system constructed high-pressure rolling mill and the linear vibrating screen. It crushes the three-stage crushed ores of 20 to 0mm into 3 to 0mm, then adopting the wet midfielder strong ultrafine mill machine to discard the tailings. And the fine iron ore of 65.00% can be obtained after re-grinding and re-selection.

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