The decomposition rate of Na
2CO
3 melts in the temperature range from 1 200 to 1 700°C under argon atmosphere was measured by using a thermobalance. Significant weight loss of the melt was observed adove 1 300°C. The rate at a steady state was given as ω=9.66 × 10
2 exp (- 58 600/RT) (g/cm
2·). The reaction scheme was concluded from this equation to be Na
2CO
3(l)→ Na
2O(l) + CO
2(g), Na
2O(l) → 2Na (g) + 1/2O
2(g). The rate-determining step was the diffusion of reaction products in argon.
The reduction of premelted Na
2CO
3-SiO
2 mixtures with graphite at about 1 200°C was examined. Residual Na
2CO
3 in the premelted mixture was completely decomposed by the reaction: Na
2CO
3(l) + 2C(s) → 2Na(g) + 3CO(g). No substantial reduction was observed for sodium metasilicate, Na
2O· SiO
2, dissolved in the premelted mixture. Excess Na
2O over 1 mol per 1 mol SiO
2 was decomposed by carbon: Na
2O(l) + C(S) → 2Na(g) + CO(g). Dense fume rising in the reaction furnace was observed during the reaction with graphite. This fume would be originated from the sodium vapour produced as the reaction product in the above reaction.
Some experimental results were presented on the removal of carbon dissolved in liquid iron by Na
2CO
3-SiO
2 mixtures.
View full abstract