Thermophysical properties of limestone as a function of origin (Part 2): Calcination enthalpy and equilibrium temperature
Summary: The influence of the origin of different limestones on the reaction enthalpy at calcination temperature and on the equilibrium temperature was experimentally determined. The reaction enthalpy at standard temperature seems to be independent of the origin and it is specified as 178 kJ/mol in the literature. The reaction enthalpy at calcination temperature varies between 160 and 172 kJ/mol for four different limestones. The equilibrium temperature at 1 bar CO2 varies between 907 and 923 °C for 18 different limestones. These values are independent of the particle size. Therefore, both researched properties depend significantly on the nature of the limestone.
For the energy evaluation of the calcination process in kilns two enthalpy values are required: the enthalpy at normal temperature and the enthalpy at decomposition temperature. The reaction enthalpy at normal temperature is decisive for the energy balance of a lime kiln. The enthalpy of the inlet and outlet gas flows and the enthalpy of the solid flows are always related to this normal temperature T0:
∆H· = M· · cp · (T – T0).(1)
The reaction enthalpy at decomposition temperature determines the energy consumption and the efficiency. This sets the minimum fuel energy input which...