Chemical and mineralogical characterization of Kahnuj ilmenite concentrate and investigation of its reduction behavior in pure hydrogen gas

Ilmenite is considered the most important source of titanium and its oxide and is usually processed by sulfate, chloride, and smelting processes. In all these processes, incomplete removal of iron combined with titanium is the main problem. In order to improve iron removal, pre-processing of ilmenite by carbothermic reduction processes is a solution used in the industry. Considering the technical and environmental problems of carbothermic, replacing coke by hydrogen, is a new method that brings significant advantages in the subsequent separation processes.

In this research, Kahnuj ilmenite concentrate is first characterized through physical, chemical, and structural analysis techniques. Gas reduction of the ilmenite pellets using pure hydrogen gas was performed, and then reduction products subjected to further characterization. The reduction degree was calculated based on the weight loss after the reduction process. Samples were characterized using optical microscopy, electron microscopy, X-ray diffraction analysis, and energy-dispersive X-ray spectroscopy.

The Kahnuj ilmenite concentrate is composed of the FeTiO3 as the main phase, hematite, and a partial sphene phase within the ilmenite grains. Mn and Mg found in the chemical analysis of the concentrate led to incomplete separation of iron oxides in ilmenite.In this research, a maximum reduction degree of 76% is achievable at a reduction temperature of 1100 °C. With an increase in the reduction temperature, metallic iron diffused out the ilmenite structure and accumulated around the particles. With an increase in the reduction time, the aggregation of the pseudobrookite phase, occurred in the center of the ilmenite particles.