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Introduction of wet electrostatic precipitator technology
The working principle of wet electrostatic precipitator
The dust collection principle and dry wet electrostatic precipitator and electrostatic precipitator are the same, by making the high-voltage corona dust charging, resulting in a large number of electrons and ions, the process of moving toward the poles in the electric field under the action of force, collision of the dust particles in the flue gas which is charged and the charged dust in electric field under the action of force and flow separation to the plate or polar motion, charged dust reaches the plate or pole line by electrostatic adsorption plate or in the polar line, so that the flue gas purification. But the dust collecting plate on the captured clear WESP and DESP have great differences, dry ESP using mechanical vibration or acoustic cleaning method to clean dust on the electrode, and the wet electric dust collector by scouring rinse water from the dust collecting plate electrode, the top flow down. To form a continuous liquid film in the dust collecting plate, the plate to capture dust washing bucket with water discharge.
Fig. 1 principle of wet electrostatic precipitator
Main design form of 2.2 wet electrostatic precipitator
At present, foreign power plants have several design forms of WESP practical engineering applications, the vast majority of the vertical flue gas flow, WESP applications in industry and power plants are more than the following three design forms:
1) independent design of vertical flue gas flow
2) horizontal smoke flow independent design, specific form
3) vertical smoke flow and WFGD integrated design
Fig. 4 horizontal smoke flow wet electrostatic precipitator Fig. 5 vertical smoke flow and WFGD integral type
Characteristics of 2.4 wet electrostatic precipitator
1) dust collection efficiency is not affected by dust properties. A nozzle with good atomizing effect is adopted, and the discharge electrode and dust collector are energized at the same time to ensure that no harmful discharge occurs. The uniform water mist inside the electric field is equivalent to the large amount of water quenching and tempering of the flue gas, and the dust collecting efficiency is not influenced by the dust property.
2) under adverse conditions, the wet electrostatic precipitator for dust collecting dry electrostatic precipitator can apply to gas purification process and performance requirements of high industry; the discharge electrode adopts a unique shape and installation methods, not damaged due to vibration or corrosion.
3) eliminate the phenomenon of back corona. The discharge electrode and dust collector can be made by using the water jet to clean the dust collector
Always keep clean, no dust accumulation on the electrode, effectively eliminate the phenomenon of back corona, improve the efficiency of dust collection per unit area, under the same conditions can achieve a lower emission concentration.
4) curb dust phenomenon occurred two times. Because of canceling the rapping, avoid the dust in the vibration two times in the process of dust, especially suitable for export requirements and low dust concentration places (the concentration of wet electric dust collector outlet can reach 10mg/Nm3 level);
5) without moving parts, greatly reduce the operation and maintenance workload. The discharge electrode with special shape and installation method, is not damaged by vibration or corrosion of the sprinkler system nozzle arrangement and the dust collecting plate type is optimized, can guarantee the epipolar line and plate the best cleaning effect, the electric dust collector without moving parts, greatly reduces the operation and maintenance work.
6) low water consumption. Wet electrostatic precipitator ash water treatment facilities from the circulatory system, circulating water flow through the nozzle does not vary with the unit load change, water consumption remained unchanged, there was a linear relationship between the amount of dust and water amount of circulating water in flue gas. Wet electrostatic precipitator has need to pay a certain amount, but due to the discharge of sewage from circulation can be used as process water pre wet desulfurization, the water supply and drainage quantity balance, the water consumption of the whole system and configuration of wet electric dust collector at the same.
Table 4 comparison table of ESP dry electrostatic precipitator and WESP wet electrostatic precipitator technology
Parameter dry electric precipitator (ESP) wet electrostatic precipitator (WESP)
The collection rate of submicron particles is low, and the collection rate of submicron particles is higher
Dust flying, about 85% of the emissions will appear flying phenomenon, no flying phenomenon; in gravity, the water film will flow to collect the surface, so that dust fall off from the bottom
The boot device needs to be preheated before it can function, and can be started directly
Thermal insulation requires special attention; thermal insulation is not required
Dust resistivity is suitable for resistivity at 108~1010
The particles of ohm-cm below 108 will cause dust to fly two times. When the resistivity is higher than 010, it will form corona. The accumulated dust will not form an insulating layer, and the water film on the collecting electrode can be used as a grounding device
Fire from the furnace of non burning, part of the burning of particles, equipment to the interior of a serious threat, there are fire hazards, there is no fire hazard
Trapping of gaseous pollutants by trapping of gaseous pollutants
(HCl, Hg2+, SO2)
Aerosols can not capture and can capture aerosols (H2SO4 aerosols and hydrocarbons)
Variations in gas parameters are very sensitive to changes in particle size, flue gas flow, temperature, and inlet dust load, which can be subjected to substantial parameter variations with a pre washing step
The actual gas flow increases with the increase of temperature, and the gas flow at dew point is lower
Sticky dust does not handle sticky dirt; it handles sticky dust
Moving parts used to remove dust collected by the vibrator require more maintenance, remove dust by flushing, and have no moving parts
The area of gas flow is large, and the air intake volume per cubic meter is larger, so the area is larger, the air flow rate is smaller, the air inlet volume per cubic meter is smaller, and the occupation area is smaller, and the utility model is suitable for installation above the scrubber
Pressure drop, low pressure drop (20~40mmwc), high pressure drop (60~80mmwc)
4 project case
Jiangsu long Thai environmental protection in Jiangsu, Xuzhou Zhen Thai company completed 200 thousand Nm3 wet dust removal system, the system is in the construction phase, covers an area of 30 square meters, is expected to process efficiency of 99%. The inlet dust content is 100mg/h, the outlet dust content is about 10mg/h, and the aerosol produced in the process can be effectively treated, and the particles produced in the production can be greatly improved.