Magnesite Dissociation pressure

The relationship between the dissociation pressure of a natural magnesite and temperature is shown in Figure 5.1. The pressure of carbon dioxide in the atmosphere above the magnesite reaches one atmosphere in pressure (760 mmHg) at a temperature of about 750°C. This dissociation temperature is considerably higher than other determinations, so one must bear in mind that this measurement was made on a natural magnesite and the figure reflects the more practical considerations of its production. 

Figure 5.1 Relationship between dissociation pressure of natural magnesite and temperature. [Data adapted from J. Chem. Soc. 123, 1055 (1923).]...

Stage 2, Calcination Zone When the magnesite reaches a temperature of about 750°C, the pressure of carbon dioxide produced by dissociation of magnesite equals the partial pressure of CO2 in the combustion atmosphere. As the magnesite progresses through the calcination zone, the temperature further rises and the surface layer of the ore begins to decompose. 

Stage 3, Once the temperature of the magnesite has exceeded the decomposition temperature, the partial pressure exceeds one atmosphere and the process of dissociation can proceed beyond the surface of the particles. 

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