A non-isothermal mathematical model is developed and verified for the process of thermal desorption of sulphur dioxide from the sodium sulphite/sulphate solutions. The process of the desorption of SO, is analysed which occurs in a packed column cooperating with an indirectly heated boiler. Good agreement is found between the model predictions and the experimental results. An analysis is carried out of the operation of the system boiler-desorption column for the various conditions and variants of the desorption process. The model is suitable for the design and optimization of the desorption of gases accompanied with a chemical reaction in the liquid phase.