DESULFURIZATION OF BATH SMELTER METAL

The purpose of the present work was to determine the mechanism and opt imal conditions for desulfurizing bath smelter metal with a CaO-CaF2 f lux. The minimum silicon (0.1 pct), or aluminum (0.3 pct), contents in the metal for optimal rates were determined. It was found that 8 to 1 0 pct CaF2 at 1450-degrees-C is required and that the rate below the C aO-CaF2 eutectic temperature (1360-degrees-C) is very slow. It is prop osed that a liquid phase at the surface of the CaO particles is requir ed, which is provided by the addition of CaF2. The Si or Al is require d to reduce the number of phases for the reaction from three, when car bon is controlling the oxygen potential, to two when Si or Al is; two- phase reactions are inherently faster than those involving three phase s. For the optimal conditions, the rate is controlled by mass transfer of sulfur in the metal to the CaO-CaF2 surface. A simple model for co ntinuous desulfurization indicates 95 pct desulfurization can be achie ved at high production rates for metal containing 0.10 to 0.15 pct Si using a CaO-10 pct CaF, flux at 1450-degrees-C.