Production of Ultra-low Sulfur Hot Metal by Desulfurizing with CaCO3 Base Flux and the Reaction Mechanism

Hot metal desulfurization by injecting CaCO3 base flux into a torpedo car has been studied. The desulfurization efficiency for CaCO3 base flux has been found to be higher than that for CaO base flux. This is attributed to the increase of the reaction interface area due to the thermal decomposition of the injected CaCO3 particles. The rate determining step of the desulfurization reaction in this process is liquid-phase mass transfer when the sulfur content is less than 0.013%, and mass transfer in solid particles when the sulfur content is more than 0.013%. It has also been revealed that the endothermic effect of the thermal decomposition of CaCO3 is compensated by the exothermic effect of the desiliconization reaction by CO2 gas, a product of CaCO3 decomposition, and therefore does not result in larger temperature decrease of the hot metal compared with CaO base flux.