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Desulfurization and denitration wet electric dust removal system
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Desulfurization and denitration wet electric dust removal system
Wet electrostatic precipitator (fog) WESP dust removal is the same as conventional dry electrostatic precipitator (ESP), and the flue gas environment is different (dry and wet). DC high voltage electricity ionizes the space gas near the cathode line, and the dust particles move and deposit on the surface of the dust collecting anode under the action of electric field force after being charged. WESP uses water film or flushing to remove dust on the surface of the dust collecting anode.
WESP is mainly composed of shell, anode device, cathode device, insulation device, flushing system and high voltage unit.
1. Shell: generally steel lined glass flake and other corrosion resistant materials. Divided into vertical structure and horizontal structure. Shell shape is divided into circular and square. According to the actual situation, it can be set in the upper part of the desulfurization tower or separately.
2, air intake mode: according to the actual situation can have different settings.
Vertical structure: lower air intake, upper air outlet; can also be upper air intake, lower air outlet.
Horizontal structure: flat in and flat out, etc.
3. Dust collecting anode plate: corrosion-resistant materials are selected. Various materials have their own advantages and disadvantages, and are selected according to the actual conditions such as medium composition and temperature. Due to the large amount of gas treated, the anode is generally plate type and honeycomb type. Other uses are mostly round tube type and honeycomb type.
4, discharge cathode: there are a variety of materials and models to choose from. According to the gas conditions, corrosion-resistant materials are selected, mainly the following: stainless steel, lead-antimony alloy, titanium alloy.
5. Insulation device: the main heating methods are electric heating and hot air heating. Prevent condensation and creepage of insulated quartz tube in insulated box.
6. Flushing system: intermittent flushing or continuous flushing.
7, in the corrosive gas environment, the shell and internal parts must use anti-corrosion materials manufacturing and anti-corrosion treatment.
Equipment features
1. Widely used. Mainly used in electric power, metallurgy, boiler, chemical, waste incineration, building materials and other industries wet flue gas deep purification, ultra-low ultra-clean emissions.
2, simple process: WESP and flue gas desulfurization system integrated design, new and transformation process is simple, compact structure, small footprint. The secondary transformation can be installed after the desulfurization tower without changing the existing desulfurization and dust removal facilities, and can be operated stably for a long time.
Large range of flue gas treatment capacity: several thousand to 4 million m3/h (using multiple electric fields or multiple parallel).
4. High efficiency: removal rate of particulate matter such as PM2.5 is 85-95%; Chimney outlet dust can achieve 20mg/Nm3 and higher emission standards of 5mg/Nm3; The removal rate of SO3 acid mist is 85-99%, and the corrosiveness of wet flue gas emitted through chimneys is greatly reduced. The removal rate of liquid droplets is 70-90%; Comprehensive emission reduction of heavy metals and other pollutants. It can improve the cleanliness of flue gas emission and solve the problems of gypsum rain and white smoke.
5, other: small resistance (<300Pa); low operation and maintenance costs; service life of more than 30 years.
In view of the increasingly stringent environmental protection standards for flue gas dust removal in coal-fired power plants in China, Xi 'an Institute of Thermal Engineering initiated a project in February 2011 to develop wet electric dust removal (fog) technology, aiming to control the wet flue gas behind the desulfurization tower to carry fog droplets and dust, so that the dust discharged into the atmosphere can reach the standard and PM2.5 can be effectively controlled. At present, the technology has been demonstrated in the Huangtai Power Plant Unit 8 project, a complete success.
Technical principle
The working principle of wet electrostatic precipitator is the same as that of dry electrostatic precipitator. Both of them deliver DC negative high voltage to the electric field space. Through space gas ionization, dust particles and mist particles in flue gas move to the dust collecting plate (collector) under the action of electric field force, thus being collected on the surface of the dust collecting electrode. The dry type electrostatic precipitator uses the vibration cleaning method to shock the collected dust into the ash hopper, while the wet type electrostatic precipitator uses the mist droplet particles in the flue gas to form an overflow on the surface of the dust collector and flush the dust into the ash hopper (water ash hopper).
The biggest difference between wet electrostatic precipitator and dry electrostatic precipitator lies in the difference of flue gas working medium. The flue gas of dry electrostatic precipitator is dry flue gas, the flue gas temperature is higher, and the flue gas basically contains no fog droplets. The wet electrostatic precipitator is wet saturated flue gas, the flue gas temperature is low, the flue gas contains a large number of droplets.
The wet electrostatic precipitator is usually arranged after the wet desulfurization device, and a large number of water droplets are carried in the saturated flue gas after desulfurization, and are captured when passing through the high-voltage electric field, which can reduce the probability of gypsum rain formation. At the same time, it has a good effect on the collection of fine particulate matter PM2.5, acid mist, etc., and the smoke emission concentration can reach ≤ 10 mg/m3.
The wet electrostatic precipitator developed by Xi'an Thermal Engineering Institute adopts a new anti-corrosion material for the anode plate, does not require continuous spraying of alkaline water, the system structure is simple, and five technological innovations have been realized:
1. The new corrosion-resistant composite material is used as the dust collector plate, with modular structure and honeycomb arrangement, which can effectively use the space and distribute the flow field evenly. Corrosion resistance, discharge strength and stability, so that the equipment voltage, current in a higher parameters, so as to ensure a better dust removal effect.
2. The use of new corrosion-resistant composite materials makes the structure of the electrostatic precipitator (fog) flexible and can adapt to the current complex renovation site. It can be arranged separately at the clean gas flue at the outlet of the desulfurization tower (such as Huangtai Power Plant), at the top of the desulfurization tower, or at the open space allowed by the site conditions of the power plant.
3. It is not necessary to continuously spray alkaline water during operation, and the mist droplets in the flue gas are collected by the electric field area, and overflow is formed in the dust collection tube bundle to achieve the purpose of self-flow ash cleaning.
The high-voltage power supply adopts cross-current source and high-efficiency spark control device, which can effectively avoid the flashover and drop arc phenomenon and ensure the stable operation of the electric field.
Wet electrostatic precipitator is one of the most advanced PM2.5 control technology, can achieve the following performance indicators:
* Low power consumption (300000 kW unit power consumption less than 300 kW), low resistance (less than 350 Pa)
* High efficiency of fine particle removal. PM2.5 emission concentration is less than 1.5 mg/m3.
* Aerosol and sulfur trioxide removal efficiency greater than 60%.
* Heavy metal mercury removal efficiency of about 40%.
* Droplet removal efficiency greater than 85%.
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