Mercury removal efficiency of 75% can be achieved with the addition of a dust remover and desulfurization unit. Mercury removal rates up to 90% with the addition of an SCR unit, as well as adsorption technology, the basis for the study of oxidation technology are still weak, and there is a lack of economically viable alternatives and reductions Row technology, lack of technical support capacity is one of the crux of our country's mercury pollution control difficult.
It is understood that China's existing coal-fired power plant atmospheric mercury control of scientific research is weak, the actual emission data and census data is lacking, mercury control technology is not fully mastered, so formulating ideas and limits draw on foreign research results and emission limits value. By studying the emission standards of thermal power plants in the United States and the EU, the mercury emission limit of thermal power plants in our country is 0.03 mg / m 3. This limit is the same as in Germany's GFAVO as revised in 2004.
Thermal power plant flue gas denitrification, dust removal and desulfurization at the same time, mercury synergies can be removed effect. The EU "BAT for Large Burning Installations" recommends that the removal of mercury prioritize the use of efficient dedusting, flue gas desulphurization and denitrification synergistic control of the technical route. Adopting electrostatic precipitator or bag filter to install flue gas desulphurization device, the average removal efficiency is 75% (50% for electrostatic precipitator and 50% for flue gas desulphurization). If SCR device is added up to 90% With lignite removal efficiency of 30% to 70%.
Halide removal technology in front of coal-fired power plant Halide removal technology is to add halide into the coal conveyor belts or coal feeders in the power plant, or inject the solution directly into the hearth of the boiler. Halide in flue gas oxidizes elemental mercury to form divalent mercury, and SCR flue gas denitration device enhances the oxidation of elemental mercury to form more divalent mercury. Mercury divalent dissolved in water to be captured by desulfurization devices, and thus achieve the purpose of mercury removal. This technology has good mercury removal efficiency and low cost for coal-fired power plants with SCR and desulfurization facilities installed. Halides added to the coal do not exacerbate corrosion of the boiler since the amount of halide added to the coal is much less than that of the coal itself.
Flue injection of activated carbon adsorbent technology mainly uses wet flue gas desulfurization equipment, which can effectively control mercury emissions, and the injection system is simple, low mercury cost. The only thing worth noting is that the mercury that has been removed enters the gypsum or waste water that is discharged from the wet desulphurization of the flue gas and needs to be reprocessed. However, due to the low cost of mercury removal, this technology is very attractive for power plants that are equipped with SCR and wet FGD systems today.
Flue injection of activated carbon adsorbent is the activated carbon containing halide injected in front of electrostatic precipitator or bag filter, the mercury in the flue gas and activated carbon in the reaction of the halide and activated carbon adsorption, and then captured by the electrostatic precipitator set. Mercury collected in the fly ash will not be released again, so as to achieve the purpose of mercury removal. The proportion of adsorbent in fly ash depends on the injection rate and the ash content of the coal, typically 0.1% to 3%.
Flue injection of activated carbon adsorbent technology includes the selection and production of adsorbents, adsorbent storage and injection, mercury measurement of three links. Halogenated activated carbon sorbents are shipped from the production facility to the power plant and stored in storage tanks. Compressed air presses the adsorbent into the injector feed injection conduit, respectively, and then into the flue gas through a nozzle. A continuous mercury monitor records the mercury content in the flue gas.
Adsorbents are at the core of this technology. Optimized injection system can spray particles evenly adsorbed in the flue gas, the adsorbent particles cover all the flue space, with the fastest speed and mixing flue gas, the adsorbent particles and mercury compounds to maximize contact and Reaction, greatly improve the adsorbent mercury removal efficiency and reduce costs.
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