Abstract: A concentrator treats a lean magnetite ore and it has changed its original single magnetic separation process into a magnetic-gravity combined separation flowsheet due to the property change of the mill feed. The transformation has improved the production's metallurgical performances but the production is not stable and the concentrate has failed to attain the predetermined index. Through the investigation of the existing production and flowsheet and the analysis of the main factors influencing the production indexes and flowsheet stability, the key problems existing in the production flowsheet and each operation have been found and an optimization flowsheet consisting of staged grinding, coarse-fine separate treatment and magnetic-gravity combined separation is proposed.

Key words: Lean magnetite, Coarse-fine separate treatment, Magnetic-gravity separation process, Optimization