Flue gas desulfurization process adopting secondary mixed magnesium method and device thereof

Abstract

The invention relates to a flue gas desulfurization process adopting a secondary mixing magnesium method, a neutralization reaction process of a desulfurizer and absorption liquid comprises the following steps of: leading out a part of absorption liquid from a desulfurization tower, primarily mixing the absorption liquid with a magnesium oxide desulfurization agent, and secondarily mixing the primary mixed liquid with the absorption liquid in the tower after the primary mixed liquid is not subjected to solid-liquid separation into the desulfurization tower; performing a neutralization reaction on the magnesium oxide in the primary mixed solution and the absorption solution in the tower, or / and dissolving the magnesium sulfite crystal substance in the primary mixed solution in the absorption solution in the tower, and using the secondary mixed solution for absorbing sulfur dioxide in the flue gas. The problem that in the prior art, the PH of desulfurization absorption liquid is low or / and the concentration of effective absorption media is low is solved, the desulfurization efficiency is improved, the spraying liquid-gas ratio is reduced, and the spraying energy consumption is reduced; the utilization rate of the desulfurizer is improved, and the medicament cost is reduced; the solid content of the absorption liquid is reduced, and the problem of operation reliability of a desulfurization system is solved; and meanwhile, the problem of desulfurization product oxidation and the problem of regeneration system scale which restrict wide application of a magnesium sulfite clear liquid method desulfurization technology are solved.

Description

technical field [0001] The invention relates to flue gas desulfurization, in particular to the improvement of the existing magnesium method flue gas desulfurization process. Background technique [0002] The desulfurization tower of the traditional magnesium flue gas desulfurization includes three units: absorption, neutralization and spraying. The absorption liquid performs gas-liquid mass transfer with the flue gas in the absorption unit located in the middle of the desulfurization tower to absorb sulfur dioxide in the flue gas and complete the absorption of desulfurization absorption. The liquid enters the neutralization unit (the liquid storage section at the bottom of the tower) for neutralization reaction with the (hydrogen) magnesium oxide desulfurizer, and is introduced into the spray layer located at the upper part of the desulfurization tower by the spray pump of the circulation unit to circulate for the desulfurization of the flue gas absorb. Based on the purpose...

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Problems solved by technology

[0006] However, the "magnesium sulfite clear liquid method" technology also has technical defects in three aspects: 1) based on the slightly soluble characteristics of magnesium sulfite, the method of external regeneration The amount of absorbed liquid needs to reach 25%-100% of the spraying amount in the tower. The technical defect of large-scale equipment and high site requirements caused by the large amount of external regeneration restricts the popularization and application of this technology.

Although the desulfurization efficiency can be improved by further increasing the regeneration capacity, the scale of the regeneration system is further expanded

3) Limited by the amount of magnesium sulfite entering the tower, it is impossible to oxidize magnesium sulfite to magnesium sulfate in the tower, and the desulfurization product can only be separated from the desulfurization system from the solid-liquid separation link in the form of magnesium sulfite crystals. However, magnesium sulfite crystals are extremely difficult to oxidize after leaving the desulfurization circulation system, making it difficult to realize the comprehensive utilization of desulfurization products.

4) In order to minimize the amount of external regeneration, it is usually used to increase the rate of neutralization reaction and the completion of neutralization reaction by adding an excessive amount of desulfurizer, although the pH of the regeneration solution can reach a weakly alkaline level of 7.2-7.8 , but the magnesium-sulfur ratio of the desulfurization system is above 1.05, and the loss of desulfurizer is large

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