Study of the magnetic fading of magnetite powder for coal preparation use

Magnetic powder as a kind of coal separation medium is widely used in heavy medium coal separation process for it can be easily recovered and recycled for reuse. The recoverability and recycling stability of the magnetite powder have a direct bearing on its consumption and make-up amount in coal separation process, and the consumption of the medium directly affects the technical performance of coal separation operation. However, so far, the criteria for the evaluation of the above-going 2 factors are still unavailable. A study is made in the paper of the magnetic fading characteristics of the magnetite powder for coal separation use based on the concept of fading rate—a criterion for evaluation of recoverability of the powder, as well as the fading rate in relation to medium consumption in coal washing process. The study result may serve as a reference for making appropriate adjustment of make-up medium volume for achieving an optimum coal washing performance.