The Effect of Demagnetizing Cyclone Feed on a Plant Cyclone Performance

Abstract

The effect of demagnetizing the cyclone feed was tested at the Minorca plant under the Iron Ore Cooperative Program. The plant tests were conducted by Minorca personnel. Tests were run at cyclone feed pressures of 12, 14, and 16 psi with and without the demagnetizing coil being energized. Two test series were run at each pressure on different days. Samples were taken of the rougher concentrate (cyclone feed could not be accurately sampled), cyclone underflow and cyclone overflow. The samples were filtered and dried at Minorca and the dried samples were sent to Coleraine. They were screened through 500 mesh and the individual screen fractions were analyzed for magnetic iron (Satmagan) and silica. Results from the chemistry by size fractions were balanced using the USIMPAC program. There was good agreement between the measured and balanced data. These results indicated that the main effect of the demagnetizing coil was in the minus 500 mesh fractions. The amount of minus 500 mesh material reporting to the underflow was significantly lower when the coil was energized. Also, the silica content of the minus 500 mesh fraction in the underflow has higher, and the amount of minus 500 mesh material in the cyclone overflow was higher when the coil was on. The USIMPAC program was used with the balance data to calculate the cyclone split size, d50, and apparent by-pass for the magnetic iron and silica portion of the cyclone feed. Having the coil on or off had little effect on the d50 values for either the magnetic iron or the silica, but having the coil off increased the magnetic iron apparent by-pass by about 100 percent. Computer simulations using USIMPAC were run using previous plant data and the cyclone parameters determined above. However, this produced unrealistic results, since the previous data had a significantly coarser cyclone split. Since the cyclone splits were essentially unaffected by the coil, simulations were run with the previous data splits and the current apparent by-passes. This simulation showed an increased circulating load, but little overall effect on the line performance. Test work conclusively showed that the use of a demagnetizing coil on the cyclone feed at Minorca will significantly reduce the amount of fine iron reporting to the cyclone underflow, which should improve line performance.