In the sulfur recovery unit, the temperature control of the Claus reactor is of vital importance, as it directly affects the operational efficiency and stability of the unit.
The temperature setting of the first reactor is based on ensuring the complete hydrolysis of COS and CS₂.
COS + H₂O = H₂S + CO₂
CS₂ + H₂O = H₂S + CO₂
The reaction rates of these two reactions are controlled by kinetics, and the hydrolysis rate increases with the increasing temperature . Only when the appropriate temperature range of 316 to 350°C is reached can complete hydrolysis be achieved.
The temperature setting for the second and third reactors should follow the following principles:
2H₂S + SO₂ = 3S + 2H₂O
This reaction is a thermodynamic equilibrium reaction and an exothermic reaction. From the perspective of kinetics, the reaction rate can be determined. The lower the temperature, the higher the equilibrium conversion rate. In theory, the operating temperatures of the second and third reactors should be maintained above the dew point temperature of sulfur to be suitable. At the same time, considering capillary condensation of sulfur, a safe operating temperature range above the sulfur dew point should be established. The recommended temperature range is 210 to 250 degrees Celsius.