Corona charged particle bed with filter material and filtering method of corona charged particle bed

Abstract

The invention discloses a filter material corona charged particle bed and a filtering method thereof. The electric particle bed comprises a particle bed shell, an air distribution device and a filtering layer filled with filter material particles, wherein the air distribution device and the filtering layer are sequentially arranged in the particle bed shell from bottom to top; the particle bed shell is provided with an air inlet located above the filter layer and an air outlet located below the air distribution device, a corona discharge electrode is horizontally buried in the filter layer, a grounding electrode is horizontally placed above the filter layer and below the air inlet, the corona discharge electrode is connected with the high-voltage output end of the high-voltage pulse switching power supply, and the grounding electrode is connected with the high-voltage output end of the high-voltage pulse switching power supply. The grounding electrode is connected with the grounding end of the high-voltage pulse switching power supply and a ground wire; a gap corona charge region is formed in a space between the corona discharge electrode and the grounding electrode; the electrostatic enhanced dust collector has the advantages that the charged filter material particles are utilized to generate strong electrostatic attraction on dust with charges opposite to the polarity of the charged filter material particles, the electrostatic enhanced filtering effect is improved, and the filtering efficiency is remarkably improved.

Description

Technical Field

[0001] The invention relates to a particle bed filtering and dust removal technology, in particular to a filter material corona charged particle bed and a filtering method thereof. Background Art

[0002] In order to improve the filtration efficiency of the particle bed and reduce the pressure drop during the filtration process, the application number is 201710754057.4 (the authorization announcement number is CN 107617295 B) Chinese invention patent discloses a particle bed electrostatic enhanced filtering dust removal device, which includes an outer shell and a filter material particle layer and an air distribution device arranged in the outer shell from top to bottom. The outer shell is provided with a dust-containing air inlet and a dust-containing back-blowing air outlet located above the filter material particle layer, and a clean air outlet and a clean back-blowing air inlet located below the air distribution device. A grounded metal dust collecting plate is vertically provided in the filter material particle layer. The metal dust collecting plate separates the filter material particle layer into a plurality of sub-filter material particle layers. A metal electrode rod connected to a high-voltage power supply is vertically inserted at the center of the sub-filter material particle layer. The sub-filter material particle layer is placed in an electric field formed by the inserted metal electrode rod and the corresponding metal dust collecting plate. A grounded metal charged electrode plate is vertically provided directly above the metal dust collecting plate. A corona discharge electrode connected to a high-voltage power supply is vertically provided directly above the metal electrode rod, so that a corona charging zone is formed in the area directly above the filter material particle layer. The working principle of this device is to charge the dust using the corona charging zone, and then enhance the filtration effect under the electrostatic force of the electric field applied to the filter particle layer, thereby improving the filtration efficiency. However, under high temperature conditions, the resistivity of the filter material will decrease, which will reduce the intensity of the electric field applied to the filter particle layer, thereby reducing the filtration effect of electrostatic enhancement. This is a technical problem that needs to be solved. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a filter material corona charged particle bed and a filtration method thereof, which utilizes the charged filter material particles to generate strong electrostatic attraction to dust with charges opposite to their polarity, thereby improving the electrostatically enhanced filtration effect and significantly improving the filtration efficiency.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is: a filter material corona charged particle bed, comprising a particle bed shell and an air distribution device and a filter layer filled with filter material particles which are sequentially arranged in the particle bed shell from bottom to top, the particle bed shell is provided with an air inlet located above the filter layer and an air outlet located below the air distribution device, the air outlet is respectively connected to a clean air pipe and a back-blowing air pipe which are connected in series with a switching valve, and is characterized in that: a corona discharge electrode is horizontally buried in the filter layer, a grounding electrode is horizontally placed at a position above the filter layer and below the air inlet, the corona discharge electrode is connected to the high voltage output end of a high voltage pulse switching power supply, the grounding electrode is connected to the grounding end and the ground wire of the high voltage pulse switching power supply, and the space between the corona discharge electrode and the grounding electrode forms an intermittent corona charging zone.

[0005] The high-voltage pulse switching power supply uses a unipolar pulse switching power supply with a pulse frequency of 1 to 30 Hz, a pulse width of 1 to 255 ms, and an output voltage of 0 to 150 kV or 0 to -150 kV. Here, a unipolar pulse switching power supply can provide positive or negative pulses. The pulse frequency and pulse width of the high-voltage pulse switching power supply that supplies power to the corona discharge electrode are related to the length of the power-on time and the power-off time, which have a great influence on the charge of the filter material particles and even affect whether it can be effectively charged. A shorter power-on time and a longer power-off time can fully charge the filter material particles, but if the pulse width is too large, the power-on time is too long, or the power-off time is too short, the charge of the filter material particles will be seriously reduced, because in the fluidized state, the partially charged filter material particles are thrown to the ground electrode by the action of bubbles, adsorbed on the ground electrode under the action of the electric field force, and leak charge to the ground electrode. The longer the power-on time, the more charge leaks, until its electric field force is reduced to the point where it cannot overcome gravity and falls back to the filter layer, thereby seriously reducing the charge of the filter material particles. In addition, although the electric field formed between the corona discharge electrode and the air distribution device (containing metal parts) has a small electric field strength due to the large distance between them, the charged filter material particles are squeezed downward by the electric field force, which is enough to squeeze the filter layer into a dead bed, significantly increase the air flow resistance of the filter layer, and cause local perforations, which cannot be fluidized normally, thus seriously affecting the transmission of charge from the intermittent corona charging area to the entire filter layer. The longer the power-on time and the shorter the power-off time, the more serious this situation is. Therefore, the power-on time should be shorter and the power-off time should be longer to eliminate the dead bed and perforation problems of the filter layer, and ensure the normal fluidization of the filter layer and the timely transmission of charge. However, it should be noted that if the power-on time is too short or the power-off time is too long, the required charging time will also increase. This frequency range allows flexible adjustment in different application scenarios, and can adapt to applications requiring high-frequency pulses as well as environments with low frequency requirements; the wider pulse width adjustment range means that the pulse width can be optimized for different filter material characteristics and filter layer conditions to achieve the best charging effect and dust removal efficiency; the high charge of the filter material enhances the electrostatic attraction of the filter material particles to the oppositely charged dust, significantly improves the filtration efficiency, and can adapt to different working conditions, filter material characteristics and handle dust of different properties.

[0006] The structure of the corona discharge electrode is a slotted screen composed of thin steel wires with a diameter of 2 to 5 mm, and the spacing between adjacent thin steel wires is 10 to 150 mm; the structure of the grounding electrode is a slotted screen composed of thick steel wires with a diameter of 8 to 12 mm, and the spacing between adjacent thick steel wires is 20 to 150 mm; the spacing between the corona discharge electrode and the grounding electrode is 100 to 300 mm. Here, the corona discharge electrode and the grounding electrode adopt the design of slit screen, which can provide more discharge points and make the electric field distribution more uniform. This uniform electric field helps to improve the efficiency of corona discharge and the charging effect of the entire filter layer; the diameter of the thin steel wire is 2-5mm, and the spacing between adjacent thin steel wires is 10-150mm. This design can increase the surface area of ​​corona discharge, thereby improving the discharge efficiency; the diameter of the thick steel wire is 8-12mm, and the spacing between adjacent thick steel wires is 20-150mm. This design helps to avoid abnormal discharge of the grounding electrode and enhance the stability of corona discharge of the corona discharge electrode and the charging ability of filter particles; the corona discharge electrode and the grounding electrode The spacing between them is 100 to 300 mm, which can obtain a suitable electric field strength, avoid breaking down the air medium or causing unnecessary energy loss, and increase the charge of the filter material; the structural optimization design of the corona discharge electrode and the grounding electrode enables the filter material particles to be charged more evenly, thereby increasing the charge of the filter material and the electrostatic attraction to the oppositely charged dust, improving the filtration efficiency, making the electrostatic enhanced filtration effect more significant, and helping to capture more dust particles, including very fine dust particles such as submicron particles; this structural design enables the corona discharge electrode and the grounding electrode to adapt to different working conditions, including different filter material properties, gas temperature and speed.

[0007] The buried depth of the corona discharge electrode in the filter layer is 10 to 50 mm. Here, the buried depth refers to the thickness of the filter material particle layer above the corona discharge electrode; the buried depth of the corona discharge electrode has a great influence on the charge amount of the filter material particles and the required charging time. If the buried depth is large, the additional electric field formed by the charged filter material particles will reduce the electric field strength at the corona discharge electrode, thereby reducing the charge amount of the filter material particles. However, if the buried depth is small, it will also cause the required charging time of the entire filter layer to increase. The buried depth range of 10 to 50 mm provides a certain flexibility, allowing adjustments to be made according to different working conditions and filter material characteristics to achieve the best dust removal effect; by optimizing the position of the corona discharge electrode, the filter material can be charged quickly and more, improving the electrostatic enhanced filtration effect.

[0008] The filter layer is composed of at least two layers of filter material particles, the particle size of each layer of the filter material particles decreases from top to bottom, and the density increases from top to bottom. During back-blowing cleaning, the filter material particles of each layer are fluidized and do not mix with each other. Here, the particle size of the upper filter material particles is larger, which can initially capture large dust particles, while the particle size of the lower filter material particles is smaller, which can capture finer dust, forming a step-by-step filtering effect and improving the overall filtering efficiency; the filter material particles with larger particle sizes usually have higher air permeability, so the large-size filter material particles in the upper layer can reduce the pressure loss when the airflow passes through; because the filter material particles of each layer are fluidized and do not mix during back-blowing cleaning, each layer of filter material particles can be effectively cleaned, ensuring the cleanliness of the filter material particles and the durability of the step-by-step filtering performance.

[0009] The filter layer is composed of an upper filter material particle layer and a lower filter material particle layer, the thickness of the upper filter material particle layer is 200-300mm, the corona discharge electrode is horizontally buried in the upper filter material particle layer, and the thickness of the lower filter material particle layer is 40-50mm. Here, the thicker upper filter material particle layer can accommodate more dust, extend the dust cleaning cycle, improve the dust holding capacity of the filter layer, and protect the lower filter material particle layer, avoid large particles of dust directly impacting the lower filter material particle layer, and extend the service life of the entire filter layer; the filter material particles of the lower filter material particle layer have a smaller particle size and a larger density, which is suitable for capturing fine dust particles and improving the filtering accuracy, and the finer and thinner lower filter material particle layer can form a tighter structure, improve the ability to capture fine dust, and reduce the total pressure drop of the filter layer.

[0010] The air distribution device is composed of a pre-air distribution porous plate, a slit screen and an air distribution particle layer which are sequentially distributed from bottom to top. The opening rate of the pre-air distribution porous plate is 1-3% (the smaller value is taken at high temperature). There is a gap between the pre-air distribution porous plate and the slit screen. The air distribution particle layer is spread on the slit screen, and the bottom layer of the filter material particle layer is spread on the air distribution particle layer. Here, the opening rate of the pre-air distribution porous plate is 1-3%. Such a design helps to form a uniform airflow above the pre-air distribution porous plate, reduce the instability of the airflow, and avoid excessively high or low flow rates in local areas. The setting of the slit screen and the air distribution particle layer, first, supports the filter layer; second, further distributes the air evenly. The slits of the slit screen can guide the airflow, and the air distribution particle layer can further disperse the airflow to ensure that the airflow passes through the filter layer evenly; third, prevents the leakage of fine filter material particles in the lower layer. There is a gap between the pre-air distribution porous plate and the slit screen. This design can conveniently place a static pressure sensor above the pre-air distribution porous plate (that is, between the pre-air distribution porous plate and the slit screen).

[0011] Static pressure sensors are respectively arranged above and below the pre-air distribution porous plate to test the upper and lower static pressure difference of the airflow passing through the pre-air distribution porous plate, thereby monitoring the air velocity flowing through the filter layer.

[0012] A filtering method using the filter material corona charged particle bed is characterized in that: the filtering method combines a plurality of the filter material corona charged particle beds in parallel into a particle bed filter dust collector, and ensures that each of the filter material corona charged particle beds can perform filtering-backblowing fluidized dust cleaning cycle repeatedly, so that the dust-laden airflow can be efficiently dusted; the filtering method includes a backblowing fluidized dust cleaning process, a filter material corona charging process and a filtering process,

[0013] The back-flushing fluidized dust cleaning process is as follows:

[0014] As the amount of dust deposition in any filter material corona charged particle bed increases, when the static pressure difference obtained by the two static pressure sensors monitors that the filtration air velocity of this filter material corona charged particle bed is reduced to a preset air velocity threshold, the filter material corona charged particle bed is switched from the filtration state to the back-blowing fluidized cleaning state through the switching valve, and the clean back-blowing airflow from the back-blowing air pipe enters from the air outlet, flows through the air distribution device and the filter layer in turn, so that the filter material particles in each layer of the filter material particle layer of the filter layer are fluidized, and the dust deposited in the gaps between the filter material particles is carried out of the filter material corona charged particle bed from the air inlet by the clean back-blowing airflow;

[0015] The filter material corona charging process is:

[0016] When any filter material corona charged particle bed completes back-flushing fluidized cleaning, then the high-voltage pulse switch power supply is turned on, the corona discharge is intermittent corona discharge, and the filter material particles entering the intermittent corona charging area are intermittently corona charged. At the same time, the filter material particles are mixed and collided up and down in the fluidized state, and continuously enter and exit the intermittent corona charging area, which promotes the transfer of charge from the intermittent corona charging area to the entire filter layer, so that all the filter material particles in the entire filter layer are quickly charged, and then the high-voltage pulse switch power supply is turned off;

[0017] The filtering phase process is as follows:

[0018] When any filter material corona charged particle bed completes the filter material corona charging, the switching valve is then used to switch the filter material corona charged particle bed from the filter material corona charged state to the filtering state, and the dust-laden airflow enters the filter material corona charged particle bed from the air inlet. The charged filter material particles in the filter layer generate strong electrostatic attraction to the dust with opposite charge, which significantly improves the filtration efficiency. The purified airflow after efficient dust removal passes through the air distribution device, flows out from the air outlet, and is finally led out by the clean air pipe.

[0019] Here, the dust deposition amount and filtration air velocity of the filter corona charged particle bed are monitored by a static pressure sensor to trigger the automatic back-blowing fluidized cleaning process, thereby improving the timeliness and accuracy of the cleaning process; through the regular back-blowing fluidized cleaning process, the excessive accumulation of dust in the filter layer is prevented, and the air permeability and filtration performance of the filter particles are maintained; the effective back-blowing fluidized cleaning process reduces the blockage and wear of the filter particles and prolongs the service life of the filter particles. Through electrostatically enhanced filtration, the same dust removal effect can be achieved at a higher filtration air velocity, thereby reducing the size of the equipment. The way in which the charge is transmitted from the intermittent corona charging area to the entire filter layer includes: 1) intermittent corona charging area charging: the filter particles continuously enter and exit the intermittent corona charging area in the fluidized state, and directly obtain corona charging; 2) contact transfer charging: the filter particles tumble up and down, and in the mutual collision, the charged filter particles transfer charge to the uncharged filter particles under the drive of the potential difference.

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] 1) Large corona charge of filter particles: First, by using a high-voltage pulse switching power supply, intermittent corona discharge of the corona discharge electrode is achieved, with a short power-on time and a long power-off time. This method helps to reduce the contact leakage time between the charged filter particles and the grounding electrode, reduces the loss of charge, and thus increases the charge of the filter particles. In addition, intermittent corona discharge helps to eliminate the dead bed (immobile filter particle area) and perforation (holes formed by the filter particles being blown away) problems in the filter layer caused by the DC corona electric field, ensures that the charged filter layer can be fluidized normally, and enables the charge to be effectively transmitted between the filter particles, so that the filter particles in the entire filter layer are charged more evenly, the charging speed is faster, and the charge amount is larger. Second, the corona discharge electrode is buried horizontally in the filter layer. The corona discharge electrode divides the filter layer into two parts. The part above the corona discharge electrode is in the intermittent corona charging zone. Since the filter material layer in this part is thin, it can effectively reduce the influence of the additional electric field formed by the charged filter material particles on the electric field strength at the corona discharge electrode, effectively prevent corona occlusion, and thus increase the filter material charge. Third, the horizontal placement of the corona discharge electrode and the grounding electrode helps to optimize the uniformity and stability of the electric field, and can achieve rapid, uniform and sufficient charging of the filter material particles in the filter layer under the fluidized state.

[0022] 2) Electrostatically enhanced filtration has a large effect: Due to the large corona charge of the filter particles, the electrostatic attraction of the charged filter particles to the oppositely charged dust is significantly enhanced. This enhanced electrostatic attraction is much greater than simple mechanical filtration or inertial collision filtration, which can effectively improve the dust capture ability of the charged particle bed, thereby significantly improving the filtration efficiency. Under the action of electrostatics, even very fine dust particles such as submicron particles can be effectively captured, which can significantly improve the dust removal efficiency.

[0023] 3) Reduce equipment size: Due to the electrostatic enhancement effect, the same dust removal effect can be achieved at a higher filtration air velocity, so the equipment size can be reduced while processing the same air flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a simplified structural schematic diagram of the filter material corona charged particle bed of the present invention;

[0025] Figure 2 The graph is a curve showing the change of the charge per unit surface area of ​​filter material particles at different depths in the filter layer in the filter material corona charged particle bed of the present invention as a function of the charging time. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the accompanying drawings.

[0027] This embodiment proposes a filter material corona charged particle bed, such as Figure 1 As shown, it includes a granular bed shell 1 and an air distribution device 2 and a filter layer 3 filled with filter particles which are sequentially arranged in the granular bed shell 1 from bottom to top. The granular bed shell 1 is the main structure of the granular bed. The air distribution device 2 is used to evenly distribute the airflow, and the filter layer 3 is used to capture dust. The granular bed shell 1 is provided with an air inlet 4 located above the filter layer 3 and an air outlet 5 located below the air distribution device 2. The air inlet 4 is used to guide the dust-laden airflow to enter or the back-blowing airflow to flow out, and the air outlet 5 is used to guide the purified airflow to be discharged or the clean back-blowing airflow to enter. The air outlet 5 is respectively connected to a clean air pipe (not shown in the figure) and a back-blowing air pipe (not shown in the figure) which are serially connected with a switching valve (not shown in the figure). A corona discharge electrode 7 is horizontally buried in the filter layer 3, and the corona discharge electrode 7 is used to Corona discharge is generated. A grounding electrode 8 is horizontally placed above the filter layer 3 and below the air inlet 4. The grounding electrode 8 is opposite to the corona discharge electrode 7 and is used to form an electric field. The corona discharge electrode 7 is connected to the high-voltage output end of the high-voltage pulse switching power supply 9, and the grounding electrode 8 is connected to the grounding end and the ground wire of the high-voltage pulse switching power supply 9. The high-voltage pulse switching power supply 9 provides an intermittent high voltage to intermittently ionize the air around the corona discharge electrode 7 to form charged ions and electrons. These charged particles then collide with the filter material particles to charge the filter material particles. The space between the corona discharge electrode 7 and the grounding electrode 8 forms an intermittent corona charging area 10, which can charge the filter material particles and increase the electrostatic attraction between the dust particles and the filter material particles, thereby improving the filtration efficiency.

[0028] It is further defined that the high-voltage pulse switching power supply 9 uses a unipolar pulse switching power supply, the pulse frequency is 1 to 30 Hz, preferably 5 to 10 Hz, the pulse width is 1 to 255 ms, preferably 20 to 60 ms, and the output voltage is 0 to 150 kV or 0 to -150 kV, preferably 0 to 60-100 kV. Here, a unipolar pulse switching power supply can provide positive or negative pulses, and a positive unipolar pulse switching power supply is used in the specific implementation. The pulse frequency and pulse width of the high-voltage pulse switching power supply 9 that supplies power to the corona discharge electrode 7 are related to the length of the power-on time and the power-off time, which has a great influence on the charge amount of the filter material particles, and even affects whether it can be effectively charged. A shorter power-on time and a longer power-off time can fully charge the filter particles, but if the pulse width is too large, the power-on time is too long, or the power-off time is too short, the charge of the filter particles will be seriously reduced. This is because in the fluidized state, the partially charged filter particles are thrown toward the grounding electrode 8 by the action of bubbles, and are adsorbed on the grounding electrode 8 under the action of the electric field force, and leak charge to the grounding electrode 8. The longer the power-on time, the more charge leaks, until the electric field force is reduced to the point where it cannot overcome gravity and falls back into the filter layer 3, thereby seriously reducing the charge of the filter particles. In addition, although the electric field formed between the corona discharge electrode 7 and the air distribution device 2 (containing metal parts) has a large spacing between them and a small electric field strength, the charged filter material particles are squeezed downward by the electric field force, which is enough to squeeze the filter layer 3 into a dead bed, and the air flow resistance of the filter layer 3 is significantly increased, and local perforations occur, which cannot be normally fluidized, thereby seriously affecting the transmission of charges from the intermittent corona charging area 10 to the entire filter layer 3. The longer the power-on time and the shorter the power-off time, the more serious this situation is. Therefore, the power-on time should be shorter and the power-off time should be longer to eliminate the dead bed and perforation problems of the filter layer 3, and ensure the normal fluidization of the filter layer 3 and the timely transmission of charges. However, it should be noted that if the power-on time is too short or the power-off time is too long, the required charging time will also increase. This frequency range allows flexible adjustment in different application scenarios, and can adapt to applications requiring high-frequency pulses as well as environments with low frequency requirements; the wider pulse width adjustment range means that the pulse width can be optimized for different filter material characteristics and filter layer 3 conditions to achieve the best charging effect and dust removal efficiency; the high charge of the filter material enhances the electrostatic attraction of the filter material particles to the oppositely charged dust, significantly improves the filtration efficiency, and can adapt to different working conditions, filter material characteristics and handle dust of different properties.

[0029] It is further defined that the structure of the corona discharge electrode 7 is a slit screen composed of thin steel wires with a diameter of 2 to 5 mm, and the spacing between adjacent thin steel wires is 10 to 150 mm, preferably 100 mm; the structure of the grounding electrode 8 is a slit screen composed of thick steel wires with a diameter of 8 to 12 mm, and the spacing between adjacent thick steel wires is 20 to 150 mm, preferably 100 mm; the spacing between the corona discharge electrode 7 and the grounding electrode 8 is 100 to 300 mm. Here, the corona discharge electrode 7 and the grounding electrode 8 adopt a slit screen design, which can provide more discharge points and make the electric field distribution more uniform. This uniform electric field helps to improve the efficiency of corona discharge and the charging effect of the entire filter layer 3; the diameter of the thin steel wire is 2 to 5 mm, and the spacing between adjacent thin steel wires is 10 to 150 mm. This design can increase the surface area of ​​corona discharge, thereby improving the discharge efficiency; the diameter of the thick steel wire is 8 to 12 mm, and the spacing between adjacent thick steel wires is 20 to 150 mm. This design can avoid abnormal discharge of the grounding electrode 8, enhance the stability of corona discharge of the corona discharge electrode 7 and the charging ability of filter particles; the corona discharge electrode 7 and the grounding electrode The spacing between 8 is 100 to 300 mm, which can obtain a suitable electric field strength, avoid breaking through the air medium or causing unnecessary energy loss, and increase the charge of the filter material; the structural optimization design of the corona discharge electrode 7 and the grounding electrode 8 enables the filter material particles to be charged more evenly, thereby increasing the charge of the filter material and the electrostatic attraction to the oppositely charged dust, improving the filtration efficiency, making the electrostatic enhanced filtration effect more significant, and helping to capture more dust particles, including very fine dust particles such as submicron particles; this structural design enables the corona discharge electrode 7 and the grounding electrode 8 to adapt to different working conditions, including different filter material properties, gas temperature and speed.

[0030] It is further defined that the buried depth of the corona discharge electrode 7 in the filter layer 3 is 10 to 50 mm, preferably 20 to 30 mm. Here, the buried depth refers to the thickness of the filter material particle layer above the corona discharge electrode 7; the buried depth of the corona discharge electrode 7 has a great influence on the charge amount of the filter material particles and the required charging time. If the buried depth is large, the additional electric field formed by the charged filter material particles will reduce the electric field intensity at the corona discharge electrode 7, thereby reducing the charge amount of the filter material particles, but if the buried depth is small, it will also cause the required charging time of the entire filter layer 3 to increase. The buried depth range of 10 to 50 mm provides a certain flexibility, allowing adjustments to be made according to different working conditions and filter material characteristics to achieve the best dust removal effect; by optimizing the position of the corona discharge electrode 7, the filter material can be charged quickly and more, improving the electrostatic enhanced filtering effect.

[0031] It is further defined that the filter layer 3 is composed of at least two layers of filter material particles, the particle size of each layer of filter material particles decreases layer by layer from top to bottom, and the density increases layer by layer from top to bottom. During back-blowing cleaning, each layer of filter material particles is fluidized and does not mix with each other. Here, the particle size of the upper layer of filter material particles is larger, which can initially capture large particles of dust, while the particle size of the lower layer of filter material particles is smaller, which can capture finer dust, forming a step-by-step filtering effect and improving the overall filtering efficiency; filter material particles with larger particle sizes usually have higher air permeability, so the large-size filter material particles in the upper layer can reduce the pressure loss when the airflow passes through; because the filter material particles in each layer are fluidized and do not mix during back-blowing cleaning, each layer of filter material particles can be effectively cleaned, ensuring the cleanliness of the filter material particles and the durability of the step-by-step filtering performance.

[0032] The preferred solution is, Figure 1 As shown, the filter layer 3 is composed of an upper filter material granular layer 31 and a lower filter material granular layer 32. The thickness of the upper filter material granular layer 31 is 200-300 mm, preferably 250 mm. The corona discharge electrode 7 is horizontally buried in the upper filter material granular layer 31. The thickness of the lower filter material granular layer 32 is 40-50 mm, preferably 45 mm. The filter material particles in the upper filter material granular layer 31 are floating beads with a diameter of 2-3 mm, and the filter material particles in the lower filter material granular layer 32 are gem sand with a diameter of 0.4-0.6 mm. Here, the thicker upper filter material particle layer 31 can accommodate more dust, extend the cleaning cycle, and improve the dust holding capacity of the filter layer 3, and can protect the lower filter material particle layer 32, avoid large particles of dust directly impacting the lower filter material particle layer 32, and extend the service life of the entire filter layer 3; the filter material particles of the lower filter material particle layer 32 have a smaller particle size and a larger density, which is suitable for capturing fine dust particles and improving the filtering accuracy, and the finer and thinner lower filter material particle layer 32 can form a tighter structure, improve the capture ability of fine dust, and reduce the total pressure drop of the filter layer 3 at the same time.

[0033] It is further defined that the air distribution device 2 is composed of a pre-air distribution porous plate 23, a slit screen 22 and an air distribution particle layer 21 which are sequentially distributed from bottom to top. The opening rate of the pre-air distribution porous plate 23 is 1-3% (a smaller value is taken at high temperature), there is a gap between the pre-air distribution porous plate 23 and the slit screen 22, the air distribution particle layer 21 is laid on the slit screen 22, and the bottom layer of the filter material particle layer is laid on the air distribution particle layer 21. Here, the opening rate of the pre-air distribution porous plate 23 is 1-3%. Such a design helps to form a uniform airflow above the pre-air distribution porous plate 23, reduce the instability of the airflow, and avoid excessively high or low flow rates in local areas. The arrangement of the slit screen 22 and the air distribution particle layer 21, first, supports the filter layer 3; second, further uniformly distributes the air, the slits of the slit screen 22 can guide the airflow, and the air distribution particle layer 21 can further disperse the airflow to ensure that the airflow passes through the filter layer 3 evenly; third, prevents the leakage of the lower layer of fine filter material particles. There is a gap between the pre-air distribution porous plate 23 and the slit screen 22 . This design can conveniently place a static pressure sensor 61 above the pre-air distribution porous plate 23 .

[0034] It is further defined that static pressure sensors 61 and 62 are respectively provided above and below the pre-air distribution porous plate 23 to test the upper and lower static pressure difference of the airflow passing through the pre-air distribution porous plate 23, thereby monitoring the air velocity flowing through the filter layer 3.

[0035] This embodiment also proposes a filtering method using a filter material corona charged particle bed, which combines multiple filter material corona charged particle beds in parallel into a particle bed filter dust collector, and ensures that each filter material corona charged particle bed can repeatedly perform a filtering-backblowing fluidized cleaning cycle, so that the dust-laden airflow can be efficiently dusted; the filtering method includes a backblowing fluidized cleaning process, a filter material corona charging process and a filtering process.

[0036] The back-flushing fluidized bed cleaning process is:

[0037] When the static pressure difference obtained by the two static pressure sensors 61 and 62 monitors that the filtration air velocity of any filter material corona charged granular bed is reduced to a preset air velocity threshold value (which can be set according to the situation) due to the increase of dust deposition amount in any filter material corona charged granular bed, the filter material corona charged granular bed is switched from the filtration state to the back-blowing fluidized cleaning state through the switching valve, and the clean back-blowing airflow from the back-blowing air pipe enters from the air outlet 5, flows through the air distribution device 2 and the filter layer 3 in turn, so that the filter material particles in each layer of the filter material particle layer of the filter layer 3 are fluidized, and the dust deposited in the gaps between the filter material particles is carried out of the filter material corona charged granular bed from the air inlet 4 by the clean back-blowing airflow;

[0038] The process of filter material corona charging is as follows:

[0039] When any filter material corona charged particle bed completes back-flushing fluidized cleaning, then the high-voltage pulse switch power supply 9 is turned on, the corona discharge electrode 7 intermittently performs corona discharge, and intermittent corona charging is performed on the filter material particles entering the intermittent corona charging area 10. At the same time, the filter material particles are mixed and collided up and down in the fluidized state, and continuously enter and exit the intermittent corona charging area 10, so that the charge is transferred from the intermittent corona charging area 10 to the entire filter layer 3, so that all the filter material particles in the entire filter layer 3 are quickly charged, and then the high-voltage pulse switch power supply 9 is turned off;

[0040] The filtering process is:

[0041] When any filter material corona charged particle bed completes the filter material corona charging, the filter material corona charged particle bed is then switched from the filter material corona charging state to the filtering state through the switching valve, and the dust-laden airflow enters the filter material corona charged particle bed from the air inlet 4. The charged filter material particles in the filter layer 3 generate a strong electrostatic attraction to the dust with an opposite charge to its polarity, which significantly enhances the filtration efficiency. The purified airflow after efficient dust removal passes through the air distribution device 2, flows out from the air outlet 5, and is finally led out by the clean air pipe.

[0042] Here, the dust deposition amount and filtration air velocity of the filter material corona charged particle bed are monitored by a static pressure sensor, so as to trigger the automatic back-blowing fluidized cleaning process, thereby improving the timeliness and accuracy of the cleaning process; through the regular back-blowing fluidized cleaning process, the excessive accumulation of dust in the filter layer 3 is prevented, and the air permeability and filtration performance of the filter material particles are maintained; the effective back-blowing fluidized cleaning process reduces the blockage and wear of the filter material particles, and prolongs the service life of the filter material particles. Through electrostatically enhanced filtration, the same dust removal effect can be achieved at a higher filtration air velocity, thereby reducing the size of the equipment. The way in which the charge is transmitted from the intermittent corona charging area 10 to the entire filter layer 3 includes: 1) intermittent corona charging area 10 charging: the filter material particles continuously enter and exit the intermittent corona charging area 10 in the fluidized state, and directly obtain corona charging; 2) contact transfer charging: the filter material particles tumble up and down, and in the mutual collision, the charged filter material particles transfer charge to the uncharged filter material particles under the drive of the potential difference.

[0043] For a filter material corona charged particle bed of the present embodiment, the pulse frequency of the positive unipolar pulse switching power supply is set to 5Hz, the pulse width is set to 40ms, that is, the power-on time is 40ms, the power-off time is 160ms, the output voltage is set to 0-90kV, the distance between the corona discharge electrode 7 and the grounding electrode 8 is set to 200mm, the thickness of the filter material particles above the corona discharge electrode 7 is set to 20mm, that is, the burial depth of the corona discharge electrode 7 in the filter layer 3 is 20mm, the temperature is 450℃, and the fluidizing gas velocity is 2.1u mf (u mfis the critical fluidization velocity of the upper filter material), the unit surface area charge (μC / m) of the filter material particles at different depths (surface, 37.5 mm, 75 mm, 112.5 mm, 175 mm) in the filter layer 3 2 )like Figure 2 As shown. Figure 2 It can be seen that the charge of the filter particles at different depths in the filter layer 3 is basically the same, indicating that the filter particles are strongly mixed in the fluidized state and the filter particles in the filter layer 3 are uniformly charged. Figure 2 It can also be seen that the filter particles have a large charge, reaching 30μC / m 2 , which is more than 10 times the fluidization friction charge of the filter particles.

[0044] The initial filtration air velocity is 0.45m / s, the final filtration air velocity is 0.25m / s, and the dust concentration in the dust-laden airflow entering from the air inlet 4 is 10g / m 3 , the temperature was 450℃, and two conditions of filtration were compared: condition 1: the filter particles were positively charged and the dust was negatively charged; condition 2: the filter particles were not charged and the dust was not charged. The results showed that the initial outlet dust concentration of the particle bed filtration in condition 1 was 12.5mg / Nm 3 The average outlet dust concentration during the filtration cycle is 4.82 mg / Nm 3 The initial outlet dust concentration of the particle bed filtration in condition 2 is 44.38 mg / Nm 3 The average outlet dust concentration during the filtration period is 13.47 mg / Nm 3 It can be seen that the electrostatic enhanced filtration effect of working condition 1 is very obvious.

Claims

1. A filter material corona charged granular bed, comprising a granular bed shell and an air distribution device and a filter layer filled with filter material particles arranged in the granular bed shell from bottom to top, the granular bed shell is provided with an air inlet located above the filter layer and an air outlet located below the air distribution device, the air outlet is respectively connected to a clean air pipe and a back-blowing air pipe connected in series with a switching valve, characterized in that: A corona discharge electrode is horizontally buried in the filter layer, and a grounding electrode is horizontally placed at a position above the filter layer and below the air inlet. The corona discharge electrode is connected to the high-voltage output end of the high-voltage pulse switching power supply, and the grounding electrode is connected to the grounding end and the ground wire of the high-voltage pulse switching power supply. The space between the corona discharge electrode and the grounding electrode forms an intermittent corona charging zone.

2. A filter material corona charged particle bed according to claim 1, characterized in that: The high-voltage pulse switching power supply is a unipolar pulse switching power supply with a pulse frequency of 1 to 30 Hz, a pulse width of 1 to 255 ms, and an output voltage of 0 to 150 kV or 0 to -150 kV.

3. A filter material corona charged particle bed according to claim 1, characterized in that: The structure of the corona discharge electrode is a slotted screen composed of thin steel wires with a diameter of 2 to 5 mm, and the spacing between adjacent thin steel wires is 10 to 150 mm; the structure of the grounding electrode is a slotted screen composed of thick steel wires with a diameter of 8 to 12 mm, and the spacing between adjacent thick steel wires is 20 to 150 mm; the spacing between the corona discharge electrode and the grounding electrode is 100 to 300 mm.

4. A filter material corona charged particle bed according to any one of claims 1 to 3, characterized in that: The corona discharge electrode is embedded in the filter layer to a depth of 10 to 50 mm.

5. A filter material corona charged particle bed according to claim 4, characterized in that: The filter layer is composed of at least two layers of filter material particles, the particle size of the filter material particles in each layer decreases layer by layer from top to bottom, and the density increases layer by layer from top to bottom. During backblowing cleaning, the filter material particles in each layer are fluidized and do not mix with each other.

6. A filter material corona charged particle bed according to claim 5, characterized in that: The filter layer consists of an upper filter material particle layer and a lower filter material particle layer, the thickness of the upper filter material particle layer is 200-300 mm, the corona discharge electrode is horizontally buried in the upper filter material particle layer, and the thickness of the lower filter material particle layer is 40-50 mm.

7. A filter material corona charged particle bed according to claim 5, characterized in that: The air distribution device consists of a pre-air distribution porous plate, a slit screen and an air distribution particle layer which are distributed in sequence from bottom to top. The opening rate of the pre-air distribution porous plate is 1-3%. There is a gap between the pre-air distribution porous plate and the slit screen. The air distribution particle layer is spread on the slit screen, and the bottom layer of the filter material particle layer is spread on the air distribution particle layer.

8. A filter material corona charged particle bed according to claim 7, characterized in that: Static pressure sensors are respectively arranged above and below the pre-air distribution porous plate.

9. A filtering method using the filter material corona charged particle bed according to claim 8, characterized in that: The filtering method combines a plurality of filter material corona charged particle beds in parallel into a particle bed filter dust collector, and ensures that each of the filter material corona charged particle beds can perform filtering-backblowing fluidized dust cleaning cycle repeatedly, so that the dust-laden airflow can be dusted efficiently; the filtering method includes backblowing fluidized dust cleaning process, filter material corona charging process and filtering process, The back-flushing fluidized dust cleaning process is as follows: As the amount of dust deposition in any filter material corona charged particle bed increases, when the static pressure difference obtained by the two static pressure sensors monitors that the filtration air velocity of this filter material corona charged particle bed is reduced to a preset air velocity threshold, the filter material corona charged particle bed is switched from the filtration state to the back-blowing fluidized cleaning state through the switching valve, and the clean back-blowing airflow from the back-blowing air pipe enters from the air outlet, flows through the air distribution device and the filter layer in turn, so that the filter material particles in each layer of the filter material particle layer of the filter layer are fluidized, and the dust deposited in the gaps between the filter material particles is carried out of the filter material corona charged particle bed from the air inlet by the clean back-blowing airflow; The filter material corona charging process is: When any filter material corona charged particle bed completes back-flushing fluidized cleaning, then the high-voltage pulse switch power supply is turned on, the corona discharge is intermittent corona discharge, and the filter material particles entering the intermittent corona charging area are intermittently corona charged. At the same time, the filter material particles are mixed and collided up and down in the fluidized state, and continuously enter and exit the intermittent corona charging area, which promotes the transfer of charge from the intermittent corona charging area to the entire filter layer, so that all the filter material particles in the entire filter layer are quickly charged, and then the high-voltage pulse switch power supply is turned off; The filtering process is: When any filter material corona charged particle bed completes the filter material corona charging, the switching valve is then used to switch the filter material corona charged particle bed from the filter material corona charged state to the filtering state, and the dust-laden airflow enters the filter material corona charged particle bed from the air inlet. The charged filter material particles in the filter layer generate a strong electrostatic attraction to the dust with the opposite charge to its polarity. The purified airflow after efficient dust removal passes through the air distribution device, flows out from the air outlet, and is finally led out by the clean air pipe.

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