Calcination Reactions
Calcination reactions usually take place at or above the thermal decomposition temperature (for decomposition and volatilization reactions) or the transition temperature (for phase transitions). This temperature is usually defined as the temperature at which the standard Gibbs free energy for a particular calcination reaction is equal to zero. For example, in limestone calcination, a decomposition process, the chemical reaction is
- CaCO3 → CaO + CO2(g)
The standard Gibbs free energy of reaction is approximated as ΔG°r = 177,100 − 158 T (J/mol). The standard free energy of reaction is zero in this case when the temperature, T, is equal to 1121 K, or 848 °C.
Examples of chemical decomposition reactions common in calcination processes, and their respective thermal decomposition temperatures include:
- CaCO3 → CaO + CO2; 848 °C
See also calcination equilibrium of calcium carbonate
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