Wet flue gas desulfurizing and hydrargyrum-removing technology based on two-stage oxidation reaction and system thereof

Abstract

A wet flue gas desulfurization and demercuration process and a system thereof based on two-stage oxidizing reaction. The process does two-stage oxidizing treatment to the simple substance HgO in flue gas utilizing to ultraviolet radiation and oxidant of halogen series, transmutes the gas phase divalent ion Hg2+ therein to liquid phase divalent ion Hg2+ using the modified limestone-gesso wet desulfurization process, and then transmutes the liquid phase divalent ion Hg2+ to the stable mercuric sulfide-HgS deposition via stabilizer of liquid phase divalent ion Hg2+. The system comprises desulfurization and demercuration equipments such as an ultraviolet irradiator, an electrical precipitator, an oxidant spraying unit and a reaction absorber etc, gesso treatment equipments of desulfurization byproduct, and a treating equipment for mercuric sulfide-HgS deposition. The process and the system thereof can raise the oxidation rate of simple substance Hg in the flue gas effectively, and at the same time effectively overcome the reduction release of divalent ion Hg2+ to avoid secondary pollution and be capable of raise desulfurization and demercuration efficiency of limestone-gesso wet desulfurization system.

Description

technical field [0001] The invention relates to a flue gas purification technology of a coal-fired power station, in particular to a wet flue gas desulfurization and mercury removal process based on a two-stage oxidation reaction and a system thereof. Background technique [0002] Coal is the main fuel for power stations in China at present and for a long time to come. While pulverized coal combustion provides the necessary heat and power resources, it will also bring serious mercury Hg and sulfur dioxide SO 2 pollute. According to statistics, in 2003, my country's coal-fired power plants emitted 86.8 tons of mercury into the atmosphere, and 28.94 tons of mercury in waste residues. Mercury has the characteristics of high toxicity, high volatility, easy deposition in organisms, and long hysteresis The pollution of mercury emitted into the atmosphere is global. In 2005, the total amount of sulfur dioxide discharged by coal-fired power stations in my countr...

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Problems solved by technology

[0006] Studies have shown that the limestone-gypsum wet desulfurization system has a significant effect on the divalent ion mercury Hg in the flue gas 2+ With high absorption efficiency, desulfurization and mercury removal can be realized at the same time, but there are still the following problems in the demercury removal of the existing limestone-gypsum wet desulfurization system: First, because the elemental mercury in the flue gas is difficult to dissolve in water, when the flue gas When the mercury in the gas mostly exists in the form of elemental mercury, the mercury removal efficiency of this method is not high; second, the divalent ion mercury absorbed into the desulfurizer slurry is easily absorbed by iron, manganese, nickel and other metal ions and sulfite ion reduction, and re-enter the flue gas in the form of elemental mercury, thereby reducing the actual efficiency of mercury removal; third, the mercury entering the desulfurization wastewater or desulfurization residue still has the possibility of secondary pollution

However, this method also does not solve the problem of divalent ion mercury Hg in the absorption tower. 2+ The restore release problem

In addition, this method is not sensitive to elemental mercury Hg 0 For primary oxidation treatment, if a higher mercury oxidation rate is to be achieved, an excessive amount of oxidant must be injected, and excessive oxidant will inevitably cause secondary pollution

The Chinese invention patent application publication number CN1933894A discloses a method of adding bromine-containing compounds from coal or boiler burners to enhance the oxidation of mercury. This method increases the divalent ions in flue gas through the oxidation of bromine. In order to improve the mercury removal capacity of the wet desulfurization system, but the addition of bromine-containing compounds in the combustion process has a very limited ability to oxidize elemental mercury, thus limiting the mercury removal capacity of the wet desulfurization system

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