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Technical route analysis of flue gas desulfurization, dust removal, mercury removal and ultra-low emission
2016-12-19507
Considering the environmental situation of our country, the national environmental supervision of coal-fired power enterprises is increasingly strict. When coal-fired power plants choose the ultra-low emission technology route, they should choose the technology with certain energy-saving effect. The technical route selection of ultra-low emission of flue gas pollutants shall follow the basic principle of "adjusting measures to coal, furnace, local conditions, overall coordination and development"
Due to the coal conditions, not only the design coal and check coal, but also the fluctuation of coal types and coal quality that the power plant may burn with the change of market should be considered, so as to ensure the ultra-low emission of pollutants under the condition of burning unfavorable coal quality. For example, for the flue gas conditions with stable coal quality, low ash content, easy charging and large ash sulfur ratio, it is an economic and reasonable choice to choose the low-temperature electrostatic precipitator + dry slag filter as the technical route of ultra-low emission of particles.
For the flue gas conditions with large fluctuation of coal quality, high ash content, poor charge performance and small ash sulfur ratio, the back washing filter system or bag filter equipment shall be preferred for dust removal. Whether to install a wet electrostatic precipitator at the back depends on the outlet concentration of the precipitator and the synergistic dust removal effect of the desulfurization process adopted at the back. The wet electrostatic precipitator is the best way to deal with the adverse factors Option
Technical route of sulfur dioxide ultra-low emission
1.1 desulfurization efficiency required by ultra-low emission
When the inlet concentration of different desulfurization meets the requirements of ultra-low emission, different desulfurization efficiency is required. In order to achieve stable ultra-low emission, the SO2 concentration at the outlet of desulfurization tower is controlled as 30mg / m3, so it can be calculated that the desulfurization efficiency shall not be lower than 97% when the inlet concentration is 1000mg / m3; the desulfurization efficiency shall not be lower than 98.5% when the inlet concentration is 2000mg / m3; the desulfurization efficiency shall not be lower than 99% when the inlet concentration is 3000mg / m3; and the desulfurization efficiency shall not be lower than 99% when the inlet concentration is 6000mg / m3 When the inlet concentration is 10000mg / m3, the desulfurization efficiency shall not be lower than 99.7%
The concentration range at the inlet of desulfurization tower is the condition that ultra-low emission should be strictly controlled. The technical selection of new units is relatively simple, while the application technology, equipment conditions and site of existing units have a great impact on the technical selection
1.2 selection of ultra-low emission desulfurization technology route
For coastal power plants with good sea water diffusion conditions and in line with the requirements of coastal sea area environmental function zoning, advanced sea water treatment and filtration system technology can be selected for power plants with inlet SO2 concentration lower than 2000mg / m3
Technical route of NOx ultra-low emission
Boiler low nitrogen combustion technology is the preferred technology to control nitrogen oxides. On the premise of ensuring boiler efficiency and safety, the concentration of nitrogen oxides at boiler outlet shall be reduced as much as possible
For pulverized coal boiler, the NOx concentration at boiler outlet shall be less than 550mg / m3 through burner transformation and furnace combustion condition optimization. SCR Flue Gas Denitration shall be adopted after the boiler, and measures such as selecting catalyst filtration equipment, precise ammonia injection, flow field distribution shall be taken to ensure stable and efficient operation of denitration facilities and realize ultra-low NOx emission
For circulating fluidized bed boiler, combustion adjustment shall be carried out to ensure that the concentration of nitrogen oxide generated is less than 200mg / m3. SNCR denitration device shall be installed to realize ultra-low emission of nitrogen oxide; if the ultra-low emission requirements cannot be met, SCR can be added at the back of the boiler and a layer of catalyst shall be used
For the W-type flame boiler burning anthracite, the concentration of nitrogen oxide at the outlet of the boiler should be reduced as much as possible on the premise of ensuring the efficiency and safety of the boiler. However, at present, it is difficult to achieve a lower level, and it is difficult to stably meet the ultra-low emission requirements of nitrogen oxide only by the SCR behind the boiler. There are no successful cases at home and abroad, which need further study
Typical technical route of ultra-low emission of flue gas pollutants
Ultra low emission of flue gas pollutants involves ultra-low emission of particles in flue gas, ultra-low emission of sulfur dioxide and ultra-low emission of nitrogen oxides. There are many technical options for ultra-low emission of each pollutant. At the same time, the synergy between different pollutant treatment facilities needs to be considered. Therefore, many technical routes will be combined to meet the specific conditions of different coal-fired power plants The ultra-low emission technology of particles involves not only primary dedusting, but also secondary dedusting (deep dedusting). Comparatively speaking, there are many technical routes. Here, only taking the ultra-low emission of particles as an example, the typical technical routes developed in recent years and widely used are introduced
1.1 ultra low emission technical route with wet esp as secondary dust removal
As the technical equipment for the fine treatment of pollutant control in coal-fired power plants, wet ESP is generally used in combination with dry ESP and wet desulfurization system, and can also be used in combination with low-temperature ESP, multi-functional self-cleaning filter, bag filter, etc., which can be used in new projects and reconstruction projects. The collaborative treatment of PM2.5 dust, SO3 acid mist, aerosol and other multi pollutants can be realized to achieve combustion Ultra low emission of coal power plant
1.2 ultra low emission technical route with wet desulfurization and collaborative dedusting as secondary dedusting
During the operation of limestone gypsum wet desulfurization system, part of smoke and dust in the flue gas will be removed, and some secondary organisms will also appear in the flue gas, such as gypsum particles and unreacted calcium carbonate particles formed in the desulfurization process. The net dust removal effect of wet desulfurization system depends on gas-liquid contact time, liquid-gas ratio, demister effect, flow field uniformity, dust concentration in the flue gas at the inlet of desulfurization system Whether there are additional dedusting and filtering devices and many other factors
For the composite desulfurization tower with ultra-low emission of sulfur dioxide, the rotary coupling, double tray, enhanced spray system, tube bundle dedusting and demister and other types of high-efficiency dedusting are adopted
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