The rate of formation of SiO by the reaction of CO or H2 with silica and silicate slags

Abstract: The rate of formation of SiO(g) by the reaction of CO and H₂ with silica or silicate slags containing SiO₂, CaO, and A1₂O₃ has been measured. The rate with hydrogen for both pure silica and silica in slags is controlled by gas phase mass transport. The rate changed with flow conditions, sample size, and gas properties as predicted by the appropriate mass transfer equations. In particular, the rate is faster in H₂-He than in H₂-Ar gas mixtures with the same hydrogen pressure, which proves conclusively the rate is controlled by gas phase mass transport. The rate of formation of SiO by the reaction of silica with CO did not change with flow conditions or particle size and the rate was the same in CO-He and CO-Ar with the same pressure of CO. In addition, the calculated rate with CO for mass transfer is considerably faster than was observed. These observations strongly indicate the rate is controlled by chemical kinetics on the surface. Similar results were obtained for the rate of reaction of CO with silica in slags and the rate was found to be proportional to the activity of SiO₂ and CO pressure. The present results are discussed in relationship to silicon transfer in slag-metal reactions.