Method for flue gas desulfurization by sodium-calcium double alkali method

The invention discloses a method for flue gas desulfurization, in particular to a method for flue gas desulfurization by a sodium-calcium double alkali method. The invention provides a method for flue gas desulfurization by the sodium-calcium double alkali method, which can more thoroughly oxidize sulfite so as to obtain higher-quality gypsum. The method comprises the following steps of: A. filling sulfur-containing flue gas into a desulfurizing absorption tower, and absorbing sulfur dioxide in the sulfur-containing flue gas using desulfurizing liquid; B. sending rich liquid into an oxidation reactor, and filling air into the oxidation reactor for oxidation so as to oxidize sodium sulfite in the rich liquid into sodium sulfate; C. sending the oxidized sodium sulfate solution into a precipitation reactor, adding lime water into the precipitation reactor, and reacting sodium sulfate with calcium hydroxide to generate hydrated calcium sulfate precipitate and sodium hydroxide; and D. separating the hydrated calci