Efficiency increase due to applied magnetic separation know-how
At LKAB in Sweden, the idea to increase the efficiency of the magnetite handling process matured some years ago. The goal was to concentrate magnetite ore (up to 130 t/h) after the primary autogenous (AG) mill by means of magnetic drums, in order to reach a higher quality of iron ore pebbles in the Concentrating Plant “KA3” with a capacity of 5,5 - 6 Mtpy.
The process itself is designed as fully autogenous grinding circuit consisting of the already mentioned primary AG-mill and secondary pebble mill. In the past, the material was screened immediately after it exited the AG-mill. The undersize went to LIMS (low intensity magnetic separation) and the oversize material was transported with a belt conveyor to an IFE screen.
The undersize of the screen was fed into the pebble mill as grinding media and the oversize was taken out as by-product. The oversize usually has a higher gangue content because the gangue is harder than the ore.
Figure A. Simplified flow sheet with screen (@LKAB) with double screening between primary and secondary mill
The new installation replaces the screen with the Heavy Duty Belt Drum Separator
. This allows LKAB to separate pebbles based on their magnetic properties rather than size, allowing for grinding media with less gangue. With a drive speed control on the separator, it is possible to further influence the separation.
Figure B. Simplified flowsheet with the Heavy Duty Belt Drum Separator. The change is still under evaluation. Throughput, wear and mill load are beeing monitored (@LKAB).
Before the implementation, a close and intensive communication between LKAB and IFE about the requirements of the separator took place in Kiruna. This was followed by a comprehensive material test with approx. 1000 kg material at the IFE test center in Austria. After successful investigations in the presence of LKAB at IFE’s testing area, various examinations of the test device were carried out at LKAB. With the help of these steps, the final operating parameters and the special requirements for the magnet system could be fixed in an optimal way. Designed and calculated by the IFE magnetic technology department, the separator was finally implemented as a production machine at LKAB.
Figure C. 3D drawing of the IFE Heavy Duty Belt Drum Separator (@IFE)
“In intensive communication between LKAB and IFE about our specific demand, we found a reliable partner for material tests and transferring the gained results into a production machine.”
Mikael Olofsson, LKAB Process Engineer
Luossavaara-Kiirunavaara AB (publ), which is abbreviated to LKAB, is an international high-tech mining and mineral group that mines and processes Norrbotten's unique iron ore for the global steel market. LKAB is one of Sweden's oldest industrial companies.