Energy Requirement for Calcination Process

The theoretical energy requirement to achieve the above process can be calculated as follows. First, the magnesite rock has to be raised from ambient temperature to the temperature of decomposition. Second, once at the temperature of decomposition, there is another energy component, the enthalpy of decomposition, required to decompose the magnesite to magnesium oxide and carbon dioxide. 

The energy required for the first step can be calculated from the specific heat capacity (Cp) of magnesite using the formula Cp x increase in temperature (K) we have, in going from 298 K (25°C) to 1023 K (750°C) 

The enthalpy of decomposition of magnesite at 1000 K is 1284 kJ/kg, which is the energy required for the second step. This gives a total energy requirement of 2415 kJ (2289 Btu) to decompose 1.0 kg of magnesite, or 2.42 x 106 kJ per metric tonne (2.3 MBtu), or 2.1 MBtu/short ton. 

The kinetics of the calcination process can be described by a shrinking shell model, where the process of decomposition proceeds gradually from the outside surface inward to the center. 

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