Typical Ultra-Low Emissions Technology Route for Flue Gas Pollutants

Ultra-low emissions of flue gas pollutants involve ultra-low emissions of particulate matter, SO2 and NOx in the flue gas. There are many technical options for ultra-low emissions of each pollutant, see Figure 1.

Ultra-low emissions

Figure 1 Low-emission technical route of coal-fired power plant

Compared with the ultra-low emission technology of SO2 and NOX, ultra-low emission technology of particulate matter involves not only a dust removal measure but also secondary dust removal measures with a large number of technical routes. The typical technical route is as follows:

a) Wet electrostatic precipitator as secondary dust removal technology of ultra-low emissions

(1) The effect of WESP to remove particulates is relatively stable and basically not affected by the load change of coal-fired units. Therefore, for power plants with large fluctuation of coal quality, large and frequent load changes, etc., Suitable for wet electrostatic precipitator as secondary dust removal technology of ultra-low emissions.

②WESP is used as an intensive treatment device for pollutant control in coal-fired power plants. It is generally used in combination with dry electrostatic precipitators and wet desulfurization systems. It can also be used in combination with low-temperature electric dust removal technology, electric bag compound dust removal technology and bag dust removal technology , PM2.5, SO3 acid mist, aerosol and other pollutants synergistic treatment, to achieve ultra-low emissions coal-fired power plants.

③ When the concentration of particulate matter emission is less than 10mg / m3, the concentration of WESP inlet particulate matter should be less than 30mg / m3, generally not more than 50mg / m3. When particulate emissions are required to be less than 5 mg / m3, the WESP inlet particulate concentration should be less than 20 mg / m3, typically not more than 30 mg / m3.

④When the concentration of WESP inlet particles is high, the dust removal efficiency can be improved by increasing the dust collection area and air flow velocity.

⑤ According to the site site conditions, WESP can adopt different layouts, low site layout occupy a certain site, high site layout does not occupy space.

b) Wet desulfurization synergistic dust removal as the second ultra-low emission technology line

① limestone - gypsum wet desulfurization system can remove some of the fumes in the flue gas, while the flue gas will also generate a small amount of secondary particles, such as gypsum particles formed during the desulfurization process, unreacted particles of calcium carbonate, etc., should take supporting management Measures to achieve ultra-low emissions.

(2) The net dedusting efficiency of the wet desulfurization system depends on many factors such as gas-liquid contact time, liquid-gas ratio, demister effect, uniformity of flow field, concentration of dust in the flue gas at the desulfurization system entrance, and presence or absence of additional dedusting device.

③ In order to achieve ultra-low SO2 emission, syngas removal efficiency is generally greater than 70% through the use of enhanced sprinkler system, tube-type dust remover, and other types of high efficiency dust remover, which can be used as Ultra-low emission secondary dust removal technology route.

④ When the requirement of particulate emission concentration less than 10mg / m3, the wet desulfurization inlet dust concentration should be less than 30mg / m3. When the requirements of particulate emissions concentration of less than 5mg / m3, wet desulfurization inlet soot concentration should be less than 20mg / m3.

c) Ultra-low emission technology line that does not rely on secondary dust removal based on composite dust removal with ultra-clean electric bag

① using ultra-clean electric bag composite dust collector can be directly achieved dust collector outlet smoke concentration of less than 10mg / m3 or 5mg / m3. There is no additional dust removal requirement for the downstream wet desulfurization system. As long as the concentration of the particulate matter in the desulfurization system is not increased, the particulate concentration can be less than 10mg / m3 or 5mg / m3, meeting the ultra-low emission requirements.

② ultra-clean electric bag filter dust concentration at the export of dust from the basic quality of coal and unit load changes, covering less.

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