PURPOSE: To easily and economically treat flue gas with high desulfurization rate by installing reaction tanks other than a reactor of final stage and properly setting operation conditions, such as pH for each reaction tank. ;CONSTITUTION: In the 1st process, waste gas is introduced into a cooling region 18 having a cooling means 34 in which liquid absorbent is dispersed to cool flue gas and to remove dust. In the 2nd process, a part of the waste gas having passed through the 1st process is fed into a tank 54 contg. a liquid absorbent of pH3.0-4.5 having desulfurizing power and the rest of the waste gas is fed into tanks 20, 22, 24 contg. a liquid absorbent of pH4.5-7.0 having desulfurizing power other than the tank 54 and simultaneously while oxygen contg. gas is introduced from an oxygen contg. gas introducing means 50, the waste gas is brought into contact with the liquid absorbent to desulfurize it. The liquid absorbent used in the 1st process is recovered to be stored in the reaction tank 54 and also is sprayed to use it by circulation and also the liquid absorbents in the reaction tanks 20, 22, 24 are successively discharged to use them.;COPYRIGHT: (C)1994,JPO&Japio
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