AN IMPROVEMENT ON SINTER QUALITY OF BAOTOU IRON ORE CONCENTRATE

A study was made of the macro- and microscopic structure and mineralogicalconstitution of sinter prepared by Baotou iron ore concentrate which differs fromothers by the presence of remarkable quantities of fluorine and rare earth com-pounds. The viscosity and surface tension of sinter slag phase have been measuredwith various additions of SiO_2 and CaF_2 in the sinter. It was observed that thefluorine, mainly as CaF_2, forms itself into cuspindine which is a major constituentinjurious to the properties of bonding phase and consequently the strength of thesinter. The fluorine-bearing mineral decreases obviously the viscosity and surfacetension of the slag in the sinter and makes in turn the sinter porous, with opentubular thin framework structure. Certain amount of SiO_2 may also lower thestrength of sinter slag bonding, yet it seems to be acted secondarily. In order toimprove the strength of Baotou sinter, decreasing its fluorine content to such anextent of less than 1.5% in the concentrate by benefciation may be preferable.Furthermore, both raising the slag basicity up to 2.0 and adding dolomite to sub-stitute partially the limestone in sinter burden materials may also be effective.An industrial process raising the sinter basicity up to 2.0 was found on trial inBaotou Iron and Steel Company to be successful.