WETLIMS - Measurements and Models

LKAB Contact    LTU Contact
Posted in Smart pellets

The wet low-intensity magnetic separator (LIMS) is the workhorse for winning of fine, ferromagnetic particles from ore pulps. It has worked flawlessly over several decades, but is now, when pushed for higher capacities and better concentrate grades, showing its limitations. The most severe appears to be the tendency to have large (+75 µm) liberated gangue minerals entering the concentrate stream. This was shown by Moen (2007). A few trapped (entrained) gangue particles did have small inclusions of what appeared to be magnetite. It is at present unclear to what extent such inclusions will influence the entrapment of large gangue particles with the magnetite concentrate.

Previous work

A pre-project regarding wet low-intensity magnetic separators were run as a Research Trainee project at Mineral Processing with additional support from Fluid Mechanics at LTU. It resulted in a Master Thesis (Lejon Isaksson, 2008) and a short report over initial pilot tests (Lejon Isaksson, 2010).

 

 

Metso’s wet LIMS with Counter current (CTC) tank

 

By going through the literature it became clear that not very much had been published about magnetic separators in scientific journals. Most of the references were to conferences where small improvements on the general design: stronger magnets, larger drum diameters etc. were presented It was also clear from manufacturer’s documentation, and from interviews with LKAB personnel, that the design of the trough had evolved over the years without good documentation of cause and effect. Also, the best way of running a wet LIMS was up to debate. So, it was clear that the separator is a proven work-horse taken for granted, but there is a general lack of understanding of its design and operation parameters.

 

Project Scope

The suggested project will try to infer the internal workings of a wet low-intensity magnetic separator by a combination of direct-indirect measurements, and computational flow calculations. The measurements should be the validation tool for computations and planned research.

By sampling magnetic concentrates, produced for known combinations of magnetic strengths and flow velocities, getting a first estimate to what extent magnetic inclusions or mixed particles contribute to the contamination of the concentrates.

Furthermore, create the basis for establishing guidelines for running of WLIMS given particle size distributions and mineralogical composition of LKAB ores.