Flue gas treatment method and system

Abstract

The invention discloses a flue gas treatment method and a flue gas treatment system. Flue gas contains sulfur dioxide, hydrogen chloride and hydrogen bromide. The method comprises the following steps: (1) enabling the flue gas to be reversely in contact with absorption liquid containing zinc oxide to obtain purified flue gas and after-absorption liquid containing zinc sulfite, zinc chloride and zinc bromide; (2) performing filtration treatment on the after-absorption liquid to obtain filtrate and filter residues, wherein the filtrate contains zinc chloride and zinc bromide, and the filter residues contain zinc sulfite; (3) performing slurrying treatment on the filter residues; (4) performing oxidization treatment on slurry containing zinc sulfite to convert the zinc sulfite in the slurry into zinc sulfate to obtain a solution containing zinc sulfate; (5) performing evaporation and concentration treatment on the solution containing zinc sulfate to obtain a zinc sulfate heptahydrate product. By the method, the flue gas can be simultaneously desulfurized and dehalogenated to reach an emission standard; meanwhile, sulfur dioxide in the flue gas can be recycled, so that resources can be maximally recycled.

Description

technical field [0001] The invention belongs to the technical field of chemical industry, in particular, the invention relates to a method and a system for processing flue gas. Background technique [0002] At present, more than 200 flue gas desulfurization technologies have been researched and developed in the world, but only dozens of methods have been maturely applied in industrialization. Generally, according to the principle of whether desulfurization by-products are recycled or not, they can be divided into two types: discarding method and recycling method. The discarding method is a desulfurization method that discards desulfurization products. The lime (stone)-gypsum method is the most commonly used at home and abroad. The technology of this method is very mature and the operating cost is relatively low, accounting for 90% of the total desulfurization market share. Other major disposal methods include sodium-alkali method and magnesium method. The relatively mature...

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Problems solved by technology

[0003] The flue gas treated by electronic waste pyrolysis contains a certain concentration of HCl and HBr, and the content of heavy metals in the flue dust is high and the composition is complex. The lime (stone)-gypsum process is adopted. From a technical point of view, the removal effect can be guaranteed, but the gypsum The filter cake has high impurity content and cannot be used as industrial raw materials, so it can only be stockpiled as solid hazardous waste; the filtrate contains Cl - and Br - Ions are continuously enriched in the system, which will cause serious corrosion of the system equipment and reduce the service life. The solution is to send the filtrate to the wastewater treatment station for comprehensive purification treatment. The cost of the treatment is very high, which makes the process economical. poor

If the regenerative amine absorption and desorption method and the acid method are considered, the flue gas contains a certain concentration of HCl and HBr, and the heavy metal content in the flue dust is high and the composition is complex, which may affect the absorbent of the regenerative amine absorption and desorption method and the acid method. Serious impact will cause the absorbent to lose its activity, and the absorption reaction cannot be carried out normally. In addition, the investment in the regenerative amine absorption and desorption method and the acid method is relatively high

The sodium-alkali method desulfurizes and purifies flue gas. After the wastewater is treated, the salt content is high, and NaOH needs to be purchased, and the operating cost is high.

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