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

Abstract

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 calcium sulfate precipitate from sodium hydroxide solution, treating the hydrated calcium sulfate precipitate to prepare gypsum, treating the sodium hydroxide solution to prepare desulfurizing liquid which can be added into the desulfurizing absorption tower again.

Description

technical field [0001] The invention relates to a flue gas desulfurization method, in particular to a sodium-calcium double-alkali flue gas desulfurization method. Background technique [0002] The basic process of the existing sodium-alkali double-alkali flue gas desulfurization is to use sodium hydroxide or sodium carbonate as the desulfurization absorption solution for sulfur-containing flue gas. The liquid after sulfur is called desulfurization rich liquid, and the desulfurization rich liquid mainly contains sodium sulfite, and then all the desulfurization rich liquid is reacted with lime water in the displacement reactor to form calcium sulfite precipitation, and sodium hydroxide is replaced at the same time, and then passed into The air oxidizes calcium sulfite to calcium sulfate. After solid-liquid separation, the sodium hydroxide solution is returned to the desulfurization absorption tower for recycling. [0003] The main deficiencies in the technology of the above-...

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Problems solved by technology

[0004] One is that the flue gas is directly cooled with desulfurization liquid in the desulfurization absorption tower, and the waste heat in the flue gas cannot be recycled, resulting in waste of energy. In addition, the desulfurization absorption tower purifies the flue gas with a lot of water;

[0005] Second, all the desulfurization-rich liquid in the desulfurization absorption tower will enter the displacement reactor for reaction. In this way, the amount of desulfurization-rich liquid will be relatively large, so the corresponding regeneration system equipment specifications will be relatively large, resulting in huge project investment and desulfurization cost. too high;

[0006] The third is that the circulating sodium hydroxide solution entering the desulfurization absorption tower contains high calcium ions, and reacts with sulfur dioxide in the desulfurization absorption tower to form calcium sulfite, causing serious blockage of related equipment and pipelines, frequent shutdowns for maintenance, and affecting the production of upstream main devices; The calcium sulfite solid precipitate is formed after absorbing the rich liquid and lime water. It is difficult to completely contact the gas and liquid when the air is oxidized. If the oxidation is not complete, the generated gypsum is unstable and has no use value.

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