CN103128001A - Dry-wet combination type electrostatic dust extractor and dust extracting method - Google Patents

Abstract

The invention relates to a dry-wet combined electrostatic dust collector and a dust removal method aimed at removing fine particles in flue gas, belonging to the technical field of industrial dust removal. The present invention adopts the existing electric precipitator and reforms the last two stages of the electric field. The penultimate electric field of the dust collector adopts angle steel long burr wire, zigzag wire or herringbone pole line to enhance the charging effect of the penultimate electric field on the particles; the final electric field of the dust collector adopts a circular pole line, Enhance the working voltage of the final electric field, form a strong migration electric field, and reduce the influence of corona wind on the flow field; the combination of the penultimate electric field and the final electric field improves the particle size of 0.1-1μm in the final electric field Mobility; several last-stage ash-cleaning sprinklers are installed above the polar plate of the final electric field, and the method of washing the plate with water replaces vibration cleaning to ensure that the particles attached to the plate can be removed and reduce The original secondary dust caused by rapping.

Description

A dry-wet combined electrostatic precipitator and dust removal method

technical field

The invention relates to a dry-wet combined electrostatic dust collector and a dust removal method aimed at removing fine particles in flue gas, belonging to the technical field of industrial dust removal. the

Background technique

Coal is the main energy source for industrial production such as power generation, metal smelting, and cement manufacturing in my country, and it will still occupy a dominant position in the next few decades. The flue gas emitted by its combustion contains a large amount of particles, which will cause serious environmental pollution, especially the particles that can enter the lungs with an aerodynamic diameter of less than 2.5 μm, which can enter the human body from the respiratory tract, and the surface is easy to accumulate a large amount of heavy metals. It is very harmful to human health. the

With the increasingly stringent environmental protection standards, only the electrostatic precipitator and bag filter can meet the emission requirements among the dust removal equipment currently in use. Among them, the electrostatic precipitator technology has the characteristics of concentrated separation force, small airflow resistance, low power consumption, large processing scale, high temperature resistance and strong corrosion resistance, and is widely used in my country's industrial production. However, it has a penetration window for particles with a particle size in the range of 0.1-1.0 μm, and the classification dust removal efficiency is lower than 80%. The main reason is that the particles in this particle size range are difficult to charge, and the particles are easy to follow the flow during the vibration cleaning process, causing secondary dust. the

Aiming at the problem of low removal efficiency of PM _2.5 , the existing methods of improving the electrostatic precipitator mainly include optimizing the geometric parameters and operating parameters of the traditional electrostatic precipitator, adopting the principle of pre-coagulation to reunite the particles through bipolar charging, and adopting Mobile plates, wet electrostatic precipitators, etc. improve the cleaning process. The University of Ohio adopts a film-coated wet electrostatic precipitator, replacing stainless steel plates with fiber materials, and forming a water film on the surface of the plates, which can greatly reduce the use of steel and reduce secondary dust. (Membrane-based wet electrostatic precipitation, Fuel Processing Technology, 2004, 85:781-798.) A patented electrostatic precipitator (201010607898.0) uses a fine wire mesh to replace part of the pole line in the last stage of the electrostatic precipitator to realize the charge Electric enhancement, inertial interception, Brownian diffusion capture, electrostatic force enhancement, migration distance shortening and other functions. This technology can enhance the dust collector's capture efficiency of fine particles, but it cannot solve the problem of secondary dust generation when traditional electrostatic precipitators clean dust. To sum up, most of the improvements have made great changes to the original electrostatic precipitator and are difficult to popularize. Therefore, the use of existing equipment to improve the technology of electrostatic precipitator to capture tiny particles has attracted more and more attention.

Contents of the invention

This patent provides a dry-wet combined electrostatic precipitator and dust removal method for the problems of low efficiency of capturing PM _2.5 by traditional electrostatic precipitators and serious impact of secondary dust.

The technical solution adopted by the dry-wet combined electrostatic precipitator of the present invention is to adopt the existing electric precipitator, which includes multi-stage electric fields inside, and transform the last two stages of the electric field. The penultimate electric field of the dust collector adopts angle steel long burr wire, zigzag wire or herringbone pole line to enhance the charging effect of the penultimate electric field on the particles; the final electric field of the dust collector adopts a circular pole line, Enhance the working voltage of the final electric field, form a strong migration electric field, and reduce the influence of corona wind on the flow field; the combination of the penultimate electric field and the final electric field improves the particle size of 0.1-1μm in the final electric field The migration speed and mobility; set several last-stage ash cleaning sprinklers above the plate of the final electric field, and replace the vibration cleaning with water to wash the plate, so as to ensure that all the particles attached to the plate can be removed , to reduce the secondary dust caused by rapping. the

The polar plate of the final electric field is made of corrosion-resistant conductive material or coated with a corrosion-resistant layer to avoid corrosion problems caused by wet cleaning. the

The dry-wet combined electrostatic precipitator method of the present invention is specifically as follows: the flue gas enters the dust collector, and most of the particles in the flue gas have been captured through the first few stages of electric fields; in the last two stages of electric fields, the flue gas Most of the particles are PM _2.5 . When they pass through the penultimate electric field, the charge of the particles will be strengthened, and they will move in the strong migration electric field of the final stage until the plate is captured, which improves the dust removal efficiency; when cleaning dust, the electric field of the final stage is cleaned with water. The way, and by adjusting the position and flow rate of the nozzle of the final dust cleaning sprinkler, the sprayed water forms a water film on the surface of the plate, which greatly reduces the secondary dust.

The final stage electric field is a weak discharge electric field suitable for wet dust cleaning, which reduces the probability and frequency of electric field breakdown and ensures the stable operation of the dust collector. the

In the wet cleaning process of the final electric field, the dust cleaning effect is enhanced by adding detergent or supplemented by mechanical vibration cleaning. the

The advantages of this patent compared with the prior art are as follows:

(1) Improve dust removal efficiency, especially the graded capture efficiency of PM _2.5 . In the last two stages of electric field, according to the characteristics of the smoke and dust at the entrance, the configuration of the pole line and the plate is changed to realize the combination of enhanced charging by the front electric field and enhanced migration by the rear electric field, and introduce thermophoretic force and liquid bridge force through wet cleaning in the final electric field Facilitates migration and adhesion of particles. The particles that have been deposited on the plate can minimize the secondary dust through water flushing, thus greatly improving the removal efficiency of the dust collector for PM _2.5 under the comprehensive effect;

(2) The pole line plate configuration of the final electric field is adjusted to adapt to the weak discharge electric field of wet dust cleaning, reduce the probability and frequency of electric field breakdown, and ensure the stable operation of the dust collector. Moreover, by controlling the arrangement of the water nozzles and the cleaning cycle, it is ensured that the plates will not be covered with a thicker ash layer, reducing the impact of the back corona of the ash layer, and maintaining a uniform strong electric field between the polar plates. the

(3) Good application prospect and low cost. The modification of the original traditional electrostatic precipitator is small, the transformation of the polar line and the polar plate is easy to realize, and the wet dust removal is used in the last stage, with less ash, less water consumption, and a long cleaning cycle. the

Description of drawings

Figure 1 is a schematic diagram of the overall structure of the improved dry-wet combined electrostatic precipitator. the

Figure 2(a) and Figure 2(b) are the structure diagrams of the penultimate electric field and the final electric field of the dry-wet combined electrostatic precipitator, respectively. the

Figure 3 is a schematic diagram of the partial structure of the final stage electric field of the dry-wet combined electrostatic precipitator. the

FIG. 4 is a front view of FIG. 3 . the

Labels in the figure:

1- Dust collector flue gas inlet, 2- penultimate electric field, 3- final electric field, 4- dust collector outlet, 5- ash hopper, 6- penultimate electric field pole line, 7- final dust cleaning spray Water container, 8-final electric field pole line, 9-polar plate. the

Detailed ways

The present invention provides a dry-wet combined electrostatic precipitator and a dust removal method. The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods. the

Traditional electrostatic precipitators generally adopt four electric field layouts. After the first two electric fields, most of the large particles over 10 μm have been captured by the plates, and the remaining ash in the flue gas is less than 10% of the total ash. Most of them are fine particles with a particle size below 2.5 μm. the

The overall structure of the dry-wet combined electrostatic precipitator described in the present invention is shown in FIG. 1 . The dust collector adopts the existing electrostatic precipitator, including dust collector flue gas inlet 1, dust collector outlet 4, ash hopper 5 and multiple plates 9, and retains the design of the electric field at the front of the traditional electrostatic precipitator, so as to realize the control of flue gas The removal of medium and large particle size particles, and the transformation of the last two stages of the electric field. The penultimate electric field 2 of the dust collector adopts angle steel long burr wire, zigzag wire or herringbone pole line to enhance the charging effect of the penultimate electric field on the particles, as shown in Figure 2 (a); the dust collector The final electric field 3 adopts polar lines with poor discharge effect and uniform electric field, such as circular polar lines, to enhance the working voltage of the final electric field, form a strong migration electric field, and reduce the influence of corona wind on the flow field; the penultimate electric field 2 The combination with the final electric field 3 improves the migration speed and mobility of particles with a particle size of 0.1-1 μm in the final electric field; several final dust cleaning sprinklers 7 are set above the plate of the final electric field 3, The method of rinsing the plate with water instead of vibrating to remove dust can ensure that all the particles attached to the plate can be removed and reduce the secondary dust caused by rapping, as shown in Figure 2(b), Figure 3 and Figure 4 In addition, a layer of liquid film with a lower temperature will be attached to the surface of the plate after washing, which is conducive to making particles adhere to the plate through thermophoretic force and liquid bridge force. The plate of the final electric field 3 is made of corrosion-resistant conductive material or coated with a corrosion-resistant layer to avoid corrosion problems caused by wet cleaning and ensure the normal operation of the electrostatic precipitator. the

During the operation, since the proportion of PM _2.5 in the total ash is very small, the period of final cleaning is very long and the water consumption is small. In addition, the strong electric field formed by the final circular polar line is more uniform, which can reduce the probability of electric field breakdown of the final wet dust collector and ensure its long-term normal operation. Realize the efficient and economical operation of the dry-wet combined electrostatic precipitator. The finally captured ash is collected in the ash hopper 5, and the purified gas flows out from the outlet 4 of the dust collector.

During normal work, its main capture and removal mechanism for PM _2.5 is:

(1) In the penultimate electric field, by changing the configuration of polar lines and plates, the discharge effect is enhanced, the concentration of free ions in the space is increased, and PM _2.5 is more easily charged, which is beneficial to capture in the electric field;

(2) In the final electric field, the configuration of the polar plate is changed to facilitate the formation of a uniform and stable strong migration electric field, weaken the discharge effect, reduce the dust caused by the turbulence caused by the corona wind, and make the particles easy to be captured and not easy to escape;

(3) During the cleaning process, the plate of the final electric field is washed with water to avoid rapping the plate, so that the ash bucket deposited on the plate can be collected, thereby greatly reducing the secondary dust. And according to the different properties of the dust particles, detergent can be added to the cleaning solution to ensure that the particles can be removed;

(4) The uniform low discharge and strong migration electric field selected by the final electric field can reduce the probability of breakdown in wet flue gas and ensure the stable operation of the dust collector;

(5) The use of wet dust cleaning in the final electric field can remove most of the dust and reduce the occurrence of back corona, thereby ensuring the stability of the strong electric field between the polar lines and the plates;

(6) In the final electric field, carbon fiber and other corrosion-resistant conductive materials are used instead of stainless steel for the plates, or a corrosion-resistant layer is plated on the surface of the plates to improve the corrosion resistance of the plates and ensure normal operation;

(7) In the final electric field, the electrode plate washed by water will form a layer of water film with a lower temperature on the surface, and the particles in the flue gas will be driven into the plate wall under the action of thermophoretic force, and will be driven into the plate wall by the fluid bridge force. Attached to the surface of the plate to enhance the capture effect;

Among them, the above mechanisms (1) and (2) enhance the ability of the dust collector to capture PM _2.5 under the action of multi-field coupling according to the characteristics of the dust at the entrance of the final electric field, and the mechanism (3) ensures that the captured particles There will be no secondary dusting phenomenon. Mechanisms (4), (5) and (6) make the polar plate form cooperate with the wet dust cleaning method to ensure stable and efficient operation of the equipment. Mechanism (7) introduces thermophoretic force to promote particles to The polar plate is driven into motion, and adheres to the plate wall through the fluid liquid bridge force on the surface of the polar plate to enhance the capture effect.

Claims (5)

1. do wet convolution electrostatic precipitator for one kind, inside comprises multistage electric field, it is characterized in that, the penultimate stage electric field of described deduster adopts the long prickle wire of angle steel, jaggies or fish bone well polar curve, strengthens the penultimate stage electric field to the charged effect of particle; The final stage electric field of deduster adopts the entelechy line, strengthens the operating voltage of final stage electric field, forms strong migration electric field, and reduces the impact of corona wind stream field; The combination of penultimate stage electric field and final stage electric field has promoted particle diameter in the particle of 0.1-1 μ m migration velocity and the mobility at the final stage electric field; Several final stage deashing water jets are set above the pole plate of final stage electric field, and the mode that water rinses pole plate replaces vibration dust-cleaning, and the particle of guaranteeing to be attached on pole plate all can be eliminated, and reduces the reentrainment of dust that originally caused because of rapping.

2. a kind of wet convolution electrostatic precipitator of doing according to claim 1, is characterized in that, the pole plate of described final stage electric field adopts anti-corrosion electric conducting material or plating anti-corrosion layer, with the etching problem of avoiding the wet type deashing to bring.

3. the convolution electrostatic dust removing method that wets of doing based on deduster claimed in claim 1, is characterized in that, flue gas enters deduster, and through front what electric field, in flue gas, most particles are captured; In the end in the two-stage electric field, in flue gas, particle is with PM _2.5In the majority, during through the penultimate stage electric field, charging particle can be strengthened, and moves to pole plate be hunted down in the strong migration electric field of final stage, improves efficiency of dust collection; During deashing, the mode that the final stage electric field adopts water to clean, and by regulating and controlling position and the flow velocity of final stage deashing water jet spout, make the water of ejection form moisture film at polar board surface, significantly reduce reentrainment of dust.

4. a kind of wet convolution electrostatic dust removing method of doing according to claim 3, it is characterized in that: described final stage electric field reduces probability and the number of times of electric field breakdown for adapting to the weak discharge electric field of wet type deashing, guarantees deduster stable operation.

5. a kind of wet convolution electrostatic dust removing method of doing according to claim 3, is characterized in that: in the wet type deashing process of described final stage electric field, by adding washing agent or being aided with the mechanical rapping cleaning dust mode to strengthen ash-removal effect.

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