PURPOSE: To enable to obtain a high desulfurization efficiency without accompanying offensive smell generation, by absorbing SO2 with absorbent generated at the time of regulating pH of absorbing liquid after carrying out absorption treatment, on occasion of desulfurizing exhaust liquid and gas using excess absorbent.

CONSTITUTION: Absorbent slurry, such as limestone etc., prepared in excess slurry concentration, is supplied from the slurry tank 9 to the absorption circulating tank 5 and a part of the above slurry is sent to the reaction vessel 11 through the cooling circulation tank 4, after circulating the absorption tower 3. Excess limestone is reacted with sulfuric acid and pH regulation is carried out in the vessel 11. On this occasion, generated SO2 is sent to the deodorization tower packed adsorbent, such as active carbon etc. and is changed into odorless gas and then, is discharged in the atmosphere through the discharge duct 21. On the one hand, fresh washing water is always supplied to the adsorbent through the piping 22 and the adsorbent is continuously activated and is washed. Used washing water is entered the slurry tank 9 through the piping 23 and is used as supply water.