Decomposition of Li2CO3 by interaction with SiO2 in mold flux of steel continuous casting

Abstract

The effect of SiO2 addition on the decomposition of Li2CO3 was investigated using the thermo-gravimetric and differential scanning calorimetric method (TG-DSC) at temperatures up to 1000degreesC. Addition of SiO2 greatly enhanced the decomposition of Li2CO3. The main decomposition reaction began to take place around 600degreesC, and completed just above the melting point of Li2CO3. The decomposition product was Li2O.SiO2 irrespective of the Li2CO3 to SiO2 Mixing ratio as long as both reactants were available. It was ascertained that a liquid layer between Li2CO3 and SiO2 particles formed and facilitated the decomposition reaction. The governing reaction of the decomposition was the reaction between the dissolved Li2CO3 and SiO2 in the liquid layer to form Li2O.SiO2. The decomposition rate was independent of the Li2CO3/Sio(2) Mixing ratio until either one had been completely exhausted. When excess Li2CO3 existed, it further reacted with the initial product of Li2O.SiO2 to form 2Li(2)O.SiO2. When SiO2 was found in excess, on the other hand, no further reaction took place. This is attributed to the fact that upon Li2CO3 exhaustion there is no liquid phase available to facilitate further reaction. The apparent activation energy of the decomposition of Li2CO1 in existence with SiO2 is 198 kJ mol(-1).