PURPOSE: To reduce the power consumption and to control the generation of waste water by using the steam after driving a gas suction fan in the desorption of an absorption tower, burning the obtained mixed vapor of steam and solvent (or after separated by condensation and cooling), and regenerating the desorbing steam by the produced heat.

CONSTITUTION: The desorbing steam is utilized for a steam-driven fan 8 to drive a suction fan 1, and then used for the desorption ot absorption vessel 3. The obtained mixed vapor of steam and solvent is burned 12 as such, or the mixture is condensed, cooled 5, and separated 6 into waste water and the solvent which are burned 12. The steam used for the desorption is again generated by the combustion heat. By this method, the power consumption for the suction of gaseous solvent can be reduced, and the solvent which cannot be reused even when recovered is reutilized as the combustion improver for a combustion furnace. Meanwhile since the waste water is eliminated, the generated combustion heat is utilized in the generation of desorbing steam, and the amt. of boiler steam to be supplied from the outside of the system can be reduced.