Authors: M-C. Patoine, A. De Mori, K. Borowiec
Abstract
The leaching of titanium slag to enrich feedstock for the pigment industry leads to the production of an iron chloride rich spent liquor, similar to that produced by the ilmenite leaching or steel pickling plants, but that contains higher concentration of impurities such as MgCl2 or CaCl2. Since 1998, QIT uses a pyrohydrolysis regeneration process similar to that used by the steel industry to regenerate the waste solution.
Typical spent acid composition obtained by QIT is compared to that produced by the steel pickling industry. Fundamental thermodynamics explain the impact of MgCl2 or CaCl2 on the FeCl2 liquor regeneration, as experienced by QIT in their full scale regeneration plant. MgCl2 and CaCl2 are found to be more stable in their chlorinated form than FeCl2, and require higher reaction temperature to be converted into oxides. Analysis of solid build-up collected in QIT plant reactors was performed and showed that when reaction temperature in insufficient, unconverted molten MgCl2 or CaCl2 can collect on equipment walls and in piping, and form a hard sinter with reactor dust.
