Potential Value Added Products from the Minnesota Ilmenite Deposits

Abstract

As part of the University of Minnesota’s ongoing support for the development of ilmenite deposits located within the Duluth complex, the University’s Permanent Trust Fund sponsored a project by the Coleraine Minerals Research Laboratory to determine if valued added products could be produced from the ilmenite deposits and to determine if ilmenite recovery could be increased. A previous study sponsored by the Minerals Coordinating Committee indicated that using high pressure rolls in place of a rod mill to grind the ilmenite increases TiO2 recovery by about 10 percent. The major loss of TiO2 (about 25 %) was associated with the removal of magnetite by magnetic separation after spiral concentration. The objective of this program was to determine if the magnetic portion of the spiral concentrate could be upgraded to make a concentrate suitable for either blast furnace pellet feed or DRI feed. During upgrading of the magnetic portion, non-magnetic materials should contain the bulk of the ilmenite, and they would also be upgraded to determine the potential for additional ilmenite recovery. Initial liberation grinds and Davis tube tests on the spiral magnetic concentrate indicated that grinding and magnetic separation alone could not upgrade the material sufficiently. Standard silica flotation on the ground and magnetically separated material did not provide significant upgrading. The best concentrate produced contained 58.84 percent iron, 6.66 percent TiO2, and 5.74 percent silica. Perhaps this material could be used in the iron nugget process. Amine flotation, fatty acid flotation and WHIMS were used to recover TiO2 from the non-magnetic portion of the reground spiral magnetic concentrate. Only fatty acid flotation of the ilmenite showed any potential for recovering additional ilmenite at grade. Additional test work on the use of silicate depressants is needed. Elutriation tests on size fractions indicated that grinding to finer than 200 mesh is needed for liberation of the ilmenite from the silicate gangue. While the previous test work showed increased TiO2 recovery in the spiral nonmagnetic fraction, no work was conducted on upgrading that material to determine if the increased recovery could be carried through to a final concentrate. Therefore, bench scale electrostatic separator tests were run on the spiral non-magnetic fraction produced in the previous project. The electrostatic tests indicated that both grade and recovery could be obtained.