Flue gas desulfurization process through calc-alkaline regeneration magnesium sulfite cycle absorption method

Abstract

The invention relates to a flue gas desulfurization process through a calc-alkaline regeneration magnesium sulfite cycle absorption method, which comprises the following steps: introducing flue gas containing sulfur dioxide into an absorption tower continuously, absorbing the sulfur dioxide in the flue gas circularly by using magnesium sulfite absorption liquid to convert magnesium sulfite into magnesium bisulfite, and then splitting part of the tower bottom absorption liquid to perform double decomposition reaction with calcium hydroxide to generate mixed slurry of magnesium hydroxide and calcium sulfate; splitting another part of the tower bottom absorption liquid which is put into a regeneration system outside the tower to perform regeneration with the generated mixed slurry of the magnesium hydroxide so that the magnesium bisulfite is regenerated into the magnesium sulfite; performing solid-liquid separation, reclaiming the mixed slurry of the magnesium sulfite and the calcium sulfate, and returning the filtrate to the absorption tower to perform cycle absorption; and introducing air to oxidize the reclaimed mixture of the magnesium sulfite and the calcium sulfate mixture so that the magnesium sulfite is oxidized into the magnesium sulfate, reclaiming the magnesium sulfate filtrate and returning the same to the cycle absorption, and comprehensively using sludge generated by filter pressing. The process adopts calc-alkali to regenerate the absorption liquid so that the absorption reaction rate is high.

Description

technical field [0001] The invention relates to a flue gas desulfurization process, in particular to a wet flue gas desulfurization process in which a magnesium sulfite absorption liquid is used for flue gas desulfurization cycle absorption, and a calcium-based alkaline compound is used to regenerate the absorption liquid. Background technique [0002] my country's magnesite reserves are the first in the world, and its purity is high. Magnesium desulfurization has a huge resource advantage in my country; because the solubility of the intermediate product magnesium sulfite formed during the absorption reaction process of magnesium desulfurization is much greater than that of calcium desulfurization. Calcium sulfate prevents the deposition of sulfite on the surface of the desulfurizer and affects the reaction rate. At the same time, the existence of high solubility sulfite in the circulating absorption liquid improves the absorption activity of the absorption liquid. Therefore, ...

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Problems solved by technology

[0015] Limited by the absorption reactivity and absorption capacity of the low-pH absorption liquid, in order to achieve a high desulfurization efficiency, a large liquid-gas ratio is still required, the pressure loss of the flue gas in the absorption system is large, and the power consumption and operating costs are high; The absorption system is still a low pH slurry circulation system, with high requirements for equipment anti-corrosion, wear resistance and anti-blocking, high requirements for key equipment such as circulating pumps, stirring in the tower, nozzles, etc., and large investment in engineering equipment; the regeneration reaction in the tower has high requirements for equipment, High power consumption and low efficiency

[0016] Metathesis product Mg(OH) 2 and CaSO 4 The mixture is difficult to separate completely, Mg(OH) 2 Bringing in desulfurization gypsum, resulting in difficulty in gypsum filtration and quality degradation; at the same time, the effective desulfurization agent Mg(OH) 2 The loss of SO needs to be absorbed by supplementary 2 The equivalent of 5-7% magnesium oxide is used to maintain the magnesium balance of the system, which increases the operating cost,

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