A method for removing mercury in the process of producing acid from lead-zinc smelting flue gas

Abstract

The invention relates to a method for removing mercury in the process of acid making with lead-zinc smelting flue gas, belonging to the technical field of flue gas treatment. Efficient mercury removalin the process of acid making is realized by adding a complexing agent I at the primary power wave, adding a complexing agent II to a gas-phase pipeline from an intermediate washing tower to a secondary power wave, and adding the complexing agent I at a secondary power wave; finally, mercury content in sulfuric acid in the dry absorption section is lower than 0.002%, the mercury content in finished product acid after standing is lower than 0.001%, and the requirement of superior product of industrial sulfuric acid is achieved; furthermore, the mercury removing method is steady in mercury removing efficiency, simple in mercury removal process, strong in adaptability, and favorable for transformation of existing devices, and addition of new equipment is not needed.

Description

technical field [0001] The invention belongs to the technical field of flue gas treatment, and in particular relates to a method for removing mercury in the process of producing acid from flue gas of lead-zinc smelting. Background technique [0002] Current users of sulfuric acid, especially in the fields of food industry, pharmaceutical industry, feed industry and chemical fertilizer industry, have higher and higher requirements for the mercury content of sulfuric acid used. my country's GBIT534-2014 "Industrial Sulfuric Acid" requires that the mass fraction of mercury sulfate in superior products should be less than Or equal to 0.001%, while some foreign countries require that the mass fraction of mercury in sulfuric acid should not exceed 0.000 1%. The higher and higher mercury content indicators pose new challenges to the removal of mercury in the acid production process. [0003] When the flue gas produced by lead-zinc smelting is used to make acid, because the boiling p...

AI Technical Summary

Problems solved by technology

During the acid production process, the flue gas temperature at the outlet of the purification process is controlled to be 30°C. At this time, the gaseous mercury (Hg 0 ) is mostly condensed and concentrated in the secondary power wave and near the pipeline tank of the electric demister, which not only increases the risk of equipment maintenance, but also cannot control the acid quality of the product

[0004] In order to prevent the mercury in the flue gas from being deposited in a large amount in the equipment, a mercury removal agent can be used before or during the purification process, so that the mercury and the agent can be combined to form a corresponding solid and removed from the gas phase. Mercury content in process outlet flue gas dropped to 30mg / nm 3 Left and right, mercury will not condense in a large amount in the equipment tank, which will affect the safety of personnel, but the mercury in the outlet flue gas will be brought into the product acid in the subsequent dry suction conversion, which still cannot meet the high quality requirements

[0005] The existing mercury removal methods for making acid from flue gas from lead-zinc smelting mainly include sulfidation-chlorination method. This process is mature and can make the mercury content in the finished acid meet the national standard for special sulfuric acid products, but the investment is large and the process is complicated. , The operation is cumbersome and the operation cost is high; the thiosulfate method, this method adds thiosulfate to the dry acid, and generates mercury sulfide precipitation through redox to achieve the purpose of mercury removal, but the modification requires the addition of a pre-drying tower, and the investment The sodium sulfide-potassium iodide method uses the sulfidation method to remove mercury from the flue gas, and the potassium iodide method to remove mercury from the acid, which has a good mercury removal effect, but the operating cost is high, and the finished acid produced requires Carry out decolorization treatment; iodine complexing process method, this method uses potassium iodide solution to wash flue gas to remove mercury, but the modification requires setting up an independent mercury removal tower, high operating costs, large equipment investment, and difficult transformation; Outokumpu process method , this method uses hot concentrated sulfuric acid to wash flue gas in sections to remove mercury, but this method is severely corroded and difficult to maintain equipment

[0006] The above mercury removal technologies have significant effects under certain conditions, but for the existing lead-zinc smelters where the acid production equipment has been fixed and no new equipment can be added, the above treatment methods are difficult to apply

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