On the Rate of CO Evolution with the Silica Reduction Reaction

Abstract

The evolution rate of CO gas produced by the reduction of silica in CaO-SiO₂-Al₂O₃ slag by molten carbon-saturated iron in graphite crucible has been measured in the temperature range between 1 510°C and 1 620°C, and the effects of tempenature, slag composition, silicon content of iron and ratio of interface area of slag/metal and slag/graphite on the rate have been examined.
The rate of CO evolution is proportional to activity of silica in slag and increases with an increase of the interface area. Apparent activation energies of the rate are 87 kcal/mol for acid slag and 62 kcal/mol for basic slag.
On the basis of the changes of over-all reaction rate with the ratio of the interface areas, the CO evolution rates of unit interface area are evaluated. The proportion of contribution of the reaction at each interface to over-all evolution rate is varied with temperature and slag composition. The rates of silica reduction estimated by present results are in good agreement with that already reported by many investigators.
The results obtained in this work show a good correspondence to the results of our previous study in which CO bubbles formation were observed by X-ray fluoroscopy method.
It is suggested that in this experimental condition, the reaction is controlled by chemical reaction step.