CN119140278B - Corona charged particle bed for filter material and filtering method thereof - Google Patents
Corona charged particle bed for filter material and filtering method thereof Download PDFInfo
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- CN119140278B CN119140278B CN202411426632.4A CN202411426632A CN119140278B CN 119140278 B CN119140278 B CN 119140278B CN 202411426632 A CN202411426632 A CN 202411426632A CN 119140278 B CN119140278 B CN 119140278B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
- B03C3/017—Combinations of electrostatic separation with other processes, not otherwise provided for
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/30—Particle separators, e.g. dust precipitators, using loose filtering material
- B01D46/32—Particle separators, e.g. dust precipitators, using loose filtering material the material moving during filtering
- B01D46/38—Particle separators, e.g. dust precipitators, using loose filtering material the material moving during filtering as fluidised bed
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/66—Regeneration of the filtering material or filter elements inside the filter
- B01D46/70—Regeneration of the filtering material or filter elements inside the filter by acting counter-currently on the filtering surface, e.g. by flushing on the non-cake side of the filter
- B01D46/72—Regeneration of the filtering material or filter elements inside the filter by acting counter-currently on the filtering surface, e.g. by flushing on the non-cake side of the filter with backwash arms, shoes or nozzles
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Abstract
本发明公开了一种滤料电晕荷电颗粒床及其过滤方法，该电颗粒床包括颗粒床壳体以及自下而上依次设置于颗粒床壳体内的布风装置和充填有滤料颗粒的过滤层，颗粒床壳体上设置有位于过滤层上方的进气口和位于布风装置下方的出气口，过滤层内水平埋设有电晕放电极，位于过滤层上方且位于进气口下方的位置上水平放置有接地极，电晕放电极与高压脉冲开关电源的高压输出端连接，接地极与高压脉冲开关电源的接地端及地线连接，电晕放电极与接地极之间的空间形成间隙性电晕荷电区；优点是其利用荷电后的滤料颗粒对带有与其极性相反电荷的粉尘产生强大静电引力，提升了静电增强的过滤效果，显著提高了过滤效率。
The invention discloses a filter material corona charged particle bed and a filtering method thereof. The charged particle bed comprises a particle bed shell, 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. 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. The advantage is that the charged filter material particles are used to generate a strong electrostatic attraction to dust with an opposite charge to the charged filter material particles, thereby improving the filtering effect of electrostatic enhancement and significantly improving the filtering efficiency.
Description
Technical Field
The invention relates to a particle bed filtering and dedusting technology, in particular to a filter material corona charged particle bed and a filtering method thereof.
Background
In order to improve the filtering efficiency of a particle bed and reduce the pressure drop in the filtering process, china patent application No. 201710754057.4 (issued publication No. CN 107617295B) discloses an electrostatic intensified filtering dust collector of the particle bed, which comprises an outer shell, a filter material particle layer and a wind distribution device, wherein the filter material particle layer and the wind distribution device are sequentially arranged in the outer shell from top to bottom, a dust-containing gas inlet and a dust-containing blowback gas outlet which are positioned above the filter material particle layer, a clean gas outlet and a clean blowback gas inlet which are positioned below the wind distribution device are arranged on the outer shell, a grounded metal dust collecting plate is vertically arranged 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 with a high-voltage power supply is vertically inserted in the center of the sub-filter material particle layer, a grounded metal electrode plate is vertically arranged above the metal dust collecting plate, and a corona discharge electrode connected with a high-voltage power supply is vertically arranged above the metal electrode rod, so that a corona charge area is formed in the region right above the filter material particle layer. The working principle of the device is that the corona charging area is utilized to carry out charging treatment on dust, and then the filtering effect is enhanced under the action of electrostatic force of an external electric field of a filter material particle layer, so that the filtering efficiency is improved. However, under the high temperature condition, the specific resistance of the filter material is reduced, which reduces the strength of the external electric field of the filter material particle layer, and further reduces the electrostatic enhancement filtering effect, which is a technical problem to be solved.
Disclosure of Invention
The invention aims to solve the technical problem of providing a filter material corona charged particle bed and a filtering method thereof, which utilize charged filter material particles to generate strong electrostatic attraction to dust with opposite polarity, thereby improving the electrostatic enhanced filtering effect and remarkably improving the filtering efficiency.
The technical scheme includes that the filter material corona charged particle bed comprises a particle bed shell, an air distribution device and a filter layer, wherein the air distribution device and the filter layer are sequentially arranged in the particle bed shell from bottom to top, the filter layer is filled with filter material particles, an air inlet and an air outlet are arranged above the filter layer and below the air distribution device, the air outlet is respectively connected with a clean air pipe and a back-blowing air pipe which are connected with a switching valve in series, the filter material corona charged particle bed is characterized in that a corona discharge electrode is horizontally buried in the filter layer, a grounding electrode is horizontally arranged above the filter layer and below the air inlet, the corona discharge electrode is connected with a high-voltage output end of a high-voltage pulse switching power supply, the grounding electrode is connected with a grounding end and a ground wire of the high-voltage pulse switching power supply, and a gap corona charge area is formed between the corona discharge electrode and the grounding electrode.
The high-voltage pulse switching power supply is a monopole pulse switching power supply, the pulse frequency is 1-30 Hz, the pulse width is 1-255 ms, and the output voltage is 0-150 kV or 0-150 kV. Here, positive or negative pulses may be provided using a unipolar pulsed switching power supply. The pulse frequency and the pulse width of the high-voltage pulse switching power supply for supplying power to the corona discharge electrode are related to the power-on time and the power-off time, so that the size of the charge quantity of filter material particles is greatly influenced, and even whether the effective charge can be influenced. The shorter power-on time and the longer power-off time can make the filter material particles fully charged, 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 quantity of the filter material particles is seriously reduced, because the filter material particles after partial charge are thrown to the grounding electrode under the action of bubbles under the fluidization state, are adsorbed to the grounding electrode under the action of electric field force, and leak charges to the grounding electrode, the longer the power-on time is, the more the charges leak until the electric field force is reduced to the point that the charges cannot overcome the gravity and fall back to the filter layer, thereby seriously reducing the charge quantity of the filter material particles. In addition, the electric field formed between the corona discharge electrode and the wind distribution device (containing metal parts) is small in electric field strength due to the fact that the distance between the corona discharge electrode and the wind distribution device is large, the charged filter material particles are extruded downwards under the action of the electric field force, so that the filter layer can be extruded into a dead bed, the airflow resistance of the filter layer is obviously increased, local perforation is generated, and the filter layer cannot be normally fluidized, so that the transmission of charges from a gap corona charging area to the whole filter layer is seriously influenced, the longer the power-on time is, the shorter the power-off time is, the more serious the situation is, the shorter the power-on time is, the longer the power-off time is, the dead bed and perforation problem of the filter layer are eliminated, and the normal fluidization of the filter layer and the timely transmission of the charges are ensured. It should be noted that too short a power-on time, or too long a power-off time, may also result in an increase in the required charge time. The frequency range allows flexible adjustment in different application scenes, can adapt to the application requiring high-frequency pulse and also can adapt to the environment requiring low frequency, the wider pulse width adjustment range means that the pulse width can be optimized aiming at different filter material characteristics and filter layer conditions so as to achieve the optimal charge effect and dust removal efficiency, the high charge quantity of the filter material enhances the electrostatic attraction of filter material particles to the charge dust with different polarities, the filter efficiency is obviously improved, and the filter device can adapt to different working conditions, filter material characteristics and dust with different properties.
The corona discharge electrode is in a structure of a slotted screen composed of thin steel wires with diameters of 2-5 mm, the distance between adjacent thin steel wires is 10-150 mm, the structure of the grounding electrode is in a slotted screen composed of thick steel wires with diameters of 8-12 mm, the distance between adjacent thick steel wires is 20-150 mm, and the distance between the corona discharge electrode and the grounding electrode is 100-300 mm. The corona discharge electrode and the grounding electrode are designed by adopting a slotted screen, more discharge points can be provided, so that electric field distribution is more uniform, the uniform electric field is beneficial to improving the efficiency of corona discharge and the charging effect of the whole filter layer, the diameter of each fine steel wire is 2-5 mm, the distance between every two adjacent fine steel wires is 10-150 mm, the design can increase the surface area of the corona discharge, so that the discharge efficiency is improved, the diameter of each coarse steel wire is 8-12 mm, the distance between every two adjacent coarse steel wires is 20-150 mm, the design is beneficial to avoiding abnormal discharge of the grounding electrode, enhancing the stability of corona discharge of the corona discharge electrode and the charging capacity of filter material particles, the distance between the corona discharge electrode and the grounding electrode is 100-300 mm, and suitable electric field strength can be obtained, so that air medium breakdown or unnecessary energy loss is avoided, the filter material charge is increased, the structural optimization design of the corona discharge electrode and the grounding electrode enables the filter material particles to be more uniformly charged, thereby improving the electric quantity of the filter material and the electrostatic attraction of the filter material, enhancing the filter material efficiency, enhancing the filter material dust, and further improving the filter material particle filtration efficiency, and further being more suitable for the dust particle capture performance and dust with different particle characteristics, such as fine particle filter electrode particle size and particle size.
The embedding depth of the corona discharge electrode in the filter layer is 10-50 mm. The embedding depth of the corona discharge electrode has a larger influence on the charge quantity and the required charge time of the filter material particles, if the embedding depth is large, the electric field intensity at the corona discharge electrode is reduced by an additional electric field formed by the charged filter material particles, so that the charge quantity of the filter material particles is reduced, and if the embedding depth is small, the required charge time of the whole filter layer is increased. The embedded depth range of 10-50 mm provides certain flexibility, allows adjustment according to different working conditions and filter material characteristics so as to achieve the optimal dust removal effect, and can enable the filter material to be charged quickly and more by optimizing the position of the corona discharge electrode, so that the electrostatic enhancement filter effect is improved.
The filter layer is composed of at least an upper layer and a lower layer of filter material particle layers, the particle size of the filter material particles of each filter material particle layer is reduced layer by layer from top to bottom, the density is increased layer by layer from top to bottom, when the ash is removed by back blowing, each layer of filter material particle layer is fluidized and not mixed with each other. The filter material particles with larger particle size can reduce pressure loss during air passing, and each layer of filter material particles are fluidized and not mixed during back blowing ash removal, so that each layer of filter material particles can be effectively cleaned, and the cleanliness of the filter material particles and the durability of the step filtering performance are ensured.
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 200-300 mm, the corona discharge electrode is horizontally embedded in the upper filter material particle layer, and the thickness of the lower filter material particle layer is 40-50 mm. The thicker upper filter material particle layer can contain more dust, prolong the ash cleaning period, improve the dust containing capacity of the filter layer, protect the lower filter material particle layer, prevent large particle dust from directly impacting the lower filter material particle layer, prolong the service life of the whole filter layer, and ensure that the lower filter material particle layer has smaller particle diameter and larger density, is suitable for capturing fine dust particles, improves the filtering precision, and can form a tighter structure, improves the capturing capacity of the fine dust and reduces the total pressure drop of the filter layer.
The air distribution device comprises a pre-air distribution porous plate, a slotted screen and an air distribution particle layer which are sequentially distributed from bottom to top, wherein the aperture ratio of the pre-air distribution porous plate is 1-3% (small value is taken at high temperature), a gap exists between the pre-air distribution porous plate and the slotted screen, the air distribution particle layer is paved on the slotted screen, and the filter material particle layer at the lowest layer is paved on the air distribution particle layer. The opening ratio of the pre-air distribution porous plate is 1-3%, so that uniform air flow is formed above the pre-air distribution porous plate, instability of the air flow is reduced, and too high or too low flow velocity in a local area is avoided. The slit screen and the air distribution particle layer are arranged, the filter layer is supported, air is further uniformly distributed through slits of the slit screen, air flow can be guided through the air distribution particle layer, the air flow can be further dispersed, the air flow can be ensured to uniformly pass through the filter layer, and the fine filter material particles at the lower layer are prevented from falling down. A gap exists between the pre-air distribution perforated plate and the slotted screen, and the static pressure sensor can be conveniently arranged above the pre-air distribution perforated plate (namely between the pre-air distribution perforated plate and the slotted screen).
Static pressure sensors are respectively arranged above and below the pre-air distribution porous plate and used for testing the upper and lower static pressure difference of air flow passing through the pre-air distribution porous plate, and accordingly the air speed flowing through the filter layer is monitored.
A filtering method using corona charged particle bed of filter material is characterized by that several corona charged particle beds of filter material are parallelly connected together to form a particle bed filter dust collector, and each corona charged particle bed of filter material can be repeatedly passed through the filtering-back blowing fluidization dust-removing circulation to make dust-containing air flow remove dust effectively,
The back blowing fluidization ash removal process comprises the following steps:
When the static pressure difference obtained by the two static pressure sensors monitors that the filtering air speed of the filter material corona charged particle bed is reduced to a preset air speed threshold value, the filter material corona charged particle bed is switched from a filtering state to a back blowing fluidization ash removing state through a switching valve, clean back blowing air flow from a back blowing air pipe enters from an air outlet and sequentially flows through an air distribution device and a filter layer, so that filter material particles in each filter material particle layer of the filter layer are fluidized, and dust deposited in gaps among the filter material particles is taken out of the filter material corona charged particle bed from an air inlet by clean back blowing air flow;
The corona charging process of the filter material comprises the following steps:
When any filter material corona charged particle bed finishes back blowing fluidization ash removal, then a high-voltage pulse switching power supply is connected, corona discharge electrodes carry out intermittent corona discharge on filter material particles entering an intermittent corona charging zone, meanwhile, the filter material particles are mixed up and down and collide under a fluidization state, and continuously enter and exit the intermittent corona charging zone, so that charges are promoted to be transmitted from the intermittent corona charging zone to the whole filter layer, the charge of all the filter material particles in the whole filter layer is rapidly completed, and then the high-voltage pulse switching power supply is turned off;
The filtering stage process is as follows:
When any filter material corona charged particle bed finishes filter material corona charged, the filter material corona charged particle bed is switched from a filter material corona charged state to a filtering state through a switching valve, dust-containing air flow enters the filter material corona charged particle bed from an air inlet, charged filter material particles in a filter layer generate strong electrostatic attraction to dust with charges opposite to the polarity of the dust, the filter efficiency is obviously improved, and purified air after high-efficiency dust removal flows through an air distribution device, flows out from an air outlet and is finally led out from a clean air pipe.
The static pressure sensor is used for monitoring dust deposition amount and filtering air speed of the corona charged particle bed of the filter material, automatic back blowing fluidization ash removal process triggering is achieved, timeliness and accuracy of ash removal are improved, excessive accumulation of dust in a filter layer is prevented through the regular back blowing fluidization ash removal process, air permeability and filtering performance of the filter material particles are maintained, blocking and abrasion of the filter material particles are reduced through the effective back blowing fluidization ash removal process, and service life of the filter material particles is prolonged. Through electrostatic enhancement filtration, the same dust removal effect can be achieved at higher filtration airflow rates, thereby reducing the equipment size. The mode of charge transmission from the intermittent corona charging zone to the whole filter layer comprises 1) the charge of the intermittent corona charging zone, that is, filter material particles continuously enter and exit the intermittent corona charging zone in a fluidization state to directly obtain corona charge, and 2) the contact transfer charge, that is, the filter material particles turn up and down, and in mutual collision, the charged filter material particles transfer charge to uncharged filter material particles under the drive of potential difference.
Compared with the prior art, the invention has the advantages that:
1) The corona charging quantity of the filter material particles is large, firstly, the intermittent corona discharge of the corona discharge electrode is realized by using a high-voltage pulse switching power supply, the power-on time is short, the power-off time is long, the contact and leakage time of the charged filter material particles and the grounding electrode is reduced, and the leakage of charges is reduced, so that the charging quantity of the filter material particles is increased. In addition, the intermittent corona discharge is helpful to eliminate the problems of dead beds (motionless filter material particle areas) and perforation (holes formed by blowing away filter material particles) in the filter layer caused by direct-current corona electric fields, ensure that the charged filter layer can be normally fluidized, ensure that charges can be effectively transmitted among the filter material particles, ensure that the charge of the filter material particles of the whole filter layer is more uniform, the charge speed is faster, and the charge quantity is larger. Secondly, the corona discharge electrode is horizontally buried in the filter layer, the corona discharge electrode divides the filter layer into two parts, the part above the corona discharge electrode is positioned in a gap corona charging area, and because the part of the filter material layer is thin, the influence of an additional electric field formed by charged filter material particles on the electric field intensity at the corona discharge electrode can be effectively reduced, and corona blocking is effectively prevented, so that the charge quantity of the filter material is improved. Thirdly, the horizontal arrangement mode of the corona discharge electrode and the grounding electrode is beneficial to optimizing the uniformity and stability of an electric field, and rapid, uniform and full charge of filter material particles in the filter layer in a fluidization state can be realized.
2) The electrostatic enhancement filtering effect is large, and the electrostatic attraction of the charged filter material particles to the heteropolarity charged dust is obviously enhanced due to the large corona charge quantity of the filter material particles. The enhanced electrostatic attraction is far greater than that of pure mechanical filtration or inertial collision filtration, and the dust capturing capability of the electric particle bed can be effectively improved, so that the filtration efficiency is remarkably improved. Under the action of static electricity, even very fine dust particles such as submicron particles and the like can be effectively captured, and the dust removal efficiency can be remarkably improved.
3) The size of the equipment is reduced, namely, the same dust removing effect can be achieved under the condition of higher filtering air speed due to the electrostatic enhancement effect, so that the size of the equipment can be reduced under the condition of treating the same air flow.
Drawings
FIG. 1 is a simplified schematic diagram of a corona charged particle bed of the filter material of the present invention;
Fig. 2 is a graph showing the change of the charge amount per unit surface area of filter material particles with different depths in a filter layer of a corona charged particle bed of the filter material according to the present invention with the charge time.
Detailed Description
The invention is described in further detail below with reference to the embodiments of the drawings.
The embodiment provides a filter material corona charged particle bed, as shown in fig. 1, which comprises a particle bed shell 1, an air distribution device 2 and a filter layer 3 filled with filter material particles, wherein the air distribution device 2 and the filter layer 3 are sequentially arranged in the particle bed shell 1 from bottom to top, the particle bed shell 1 is of a main structure of the particle bed, the air distribution device 2 is used for uniformly distributing air flow, the filter layer 3 is used for capturing dust, an air inlet 4 positioned above the filter layer 3 and an air outlet 5 positioned below the air distribution device 2 are arranged on the particle bed shell 1, the air inlet 4 is used for guiding dust-containing air flow to enter or back-blowing air flow to flow out, the air outlet 5 is used for guiding purified air flow to exit or clean back-blowing air flow to enter, the air outlet 5 is respectively connected with a clean air pipe (not shown in the figure) and a back-blowing air pipe (not shown in the figure) which are connected in series with a switching valve (not shown in the figure), a corona discharge electrode 7 is buried horizontally in the filter layer 3, the corona discharge electrode 7 is used for generating corona discharge, the grounding electrode 8 is horizontally arranged 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 for forming an electric field, the corona discharge electrode 7 is connected with a high-voltage output end of the high-voltage pulse switching power supply 9, the grounding electrode 8 is connected with the grounding end of the high-voltage pulse switching power supply 9 and a ground wire, the high-voltage pulse switching power supply 9 provides intermittent high voltage to enable air around the corona discharge electrode 7 to be ionized in a intermittent manner to form charged ions and electrons, the charged particles are then collided with filter material particles to charge the filter material particles, a gap corona charging area 10 is formed between the corona discharge electrode 7 and the grounding electrode 8 and can charge the filter material particles to increase electrostatic attraction between dust particles and the filter material particles, thereby improving the filtering efficiency.
Further limited, the high-voltage pulse switching power supply 9 is a unipolar pulse switching power supply, the pulse frequency is 1-30 Hz, preferably 5-10 Hz, the pulse width is 1-255 ms, preferably 20-60 ms, the output voltage is 0-150 kV or 0-150 kV, preferably 0-60-100 kV. Here, the unipolar pulse switching power supply may provide positive or negative pulses, and a positive unipolar pulse switching power supply may be selected for implementation. The pulse frequency and the pulse width of the high-voltage pulse switching power supply 9 for supplying power to the corona discharge electrode 7 are related to the power-on time and the power-off time, so that the size of the charge quantity of filter material particles is greatly influenced, and even whether the effective charge can be influenced. The shorter power-on time and longer power-off time can make the filter material particles fully charged, 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 quantity of the filter material particles is seriously reduced, because the filter material particles after partial charge are thrown to the grounding electrode 8 under the action of bubbles under the fluidization state, are adsorbed to the grounding electrode 8 under the action of electric field force, and leak charges to the grounding electrode 8, the longer the power-on time is, the more the charges leak, until the electric field force is reduced to the point that the charges cannot overcome the gravity and fall back to the filter layer 3, thereby seriously reducing the charge quantity of the filter material particles. In addition, the electric field formed between the corona discharge electrode 7 and the wind distribution device 2 (including metal parts) has small electric field intensity due to large distance between them, but the charged filter material particles are downwards extruded by the action of the electric field force, so that the filter layer 3 can be extruded into a dead bed, the airflow resistance of the filter layer 3 is obviously increased, local perforation occurs, and the electric charge can not be normally fluidized, so that the transmission of the electric charge from the intermittent corona charging area 10 to the whole filter layer 3 is seriously affected, the longer the power-on time is, the shorter the power-off time is, the more serious the power-on time is, the shorter the power-off time is, and the longer the power-off time is, so that the dead bed and perforation problems of the filter layer 3 are eliminated, and the normal fluidization of the filter layer 3 and the timely transmission of the electric charge are ensured. It should be noted that too short a power-on time, or too long a power-off time, may also result in an increase in the required charge time. The frequency range allows flexible adjustment in different application scenes, can adapt to the application requiring high-frequency pulse and also can adapt to the environment requiring low frequency, the wider pulse width adjustment range means that the pulse width can be optimized aiming at different filter material characteristics and filter layer 3 conditions so as to achieve the optimal charge effect and dust removal efficiency, the high charge quantity of the filter material enhances the electrostatic attraction of filter material particles to the charge dust with different polarities, the filter efficiency is obviously improved, and the filter material can adapt to different working conditions, filter material characteristics and dust with different properties.
Further, the corona discharge electrode 7 is a slotted screen composed of thin steel wires with diameters of 2-5 mm, the distance between adjacent thin steel wires is 10-150 mm, preferably 100mm, the grounding electrode 8 is a slotted screen composed of thick steel wires with diameters of 8-12 mm, the distance between adjacent thick steel wires is 20-150 mm, preferably 100mm, and the distance between the corona discharge electrode 7 and the grounding electrode 8 is 100-300 mm. The corona discharge electrode 7 and the grounding electrode 8 are designed by adopting a slotted screen, more discharge points can be provided, electric field distribution is more uniform, the uniform electric field is favorable for improving corona discharge efficiency and charging effect of the whole filter layer 3, the diameter of each fine steel wire is 2-5 mm, the distance between every two adjacent fine steel wires is 10-150 mm, the design can increase the surface area of corona discharge, so that discharge efficiency is improved, the diameter of each coarse steel wire is 8-12 mm, the distance between every two adjacent coarse steel wires is 20-150 mm, abnormal discharge of the grounding electrode 8 can be avoided, corona discharge stability of the corona discharge electrode 7 and charging capacity of filter material particles are improved, the distance between the corona discharge electrode 7 and the grounding electrode 8 is 100-300 mm, proper electric field strength can be obtained, air medium breakdown or unnecessary energy loss is avoided, the structure optimization design of the corona discharge electrode 7 and the grounding electrode 8 enables filter material particles to be more uniformly charged, attractive force and electrostatic dust to be charged, the electrostatic dust to be more remarkably improved, the electrostatic dust-collecting effect of the corona discharge electrode 7 is improved, the electrostatic dust-collecting device is more suitable for dust particles with different particle-collecting characteristics, and the dust-collecting performance is more suitable for dust-collecting conditions.
Further, the depth of embedding of the corona discharge electrode 7 in the filter layer 3 is 10 to 50mm, preferably 20 to 30mm. The embedding depth refers to the thickness of the filter material particle layer above the corona discharge electrode 7, the embedding depth of the corona discharge electrode 7 has a larger influence on the charge amount and the required charge time of the filter material particles, if the embedding depth is large, the additional electric field formed by the charged filter material particles can reduce the electric field intensity at the corona discharge electrode 7, thereby reducing the charge amount of the filter material particles, but if the embedding depth is small, the required charge time of the whole filter layer 3 can also be increased. The embedding depth range of 10-50 mm provides certain flexibility, allows adjustment according to different working conditions and filter material characteristics so as to achieve the optimal dust removal effect, and can enable the filter material to be charged quickly and more by optimizing the position of the corona discharge electrode 7, so that the electrostatic enhancement filter effect is improved.
Further defined, the filter layer 3 is composed of at least an upper and a lower filter material particle layers, the particle sizes of the filter material particles of the filter material particle layers are reduced layer by layer from top to bottom, the density of the filter material particles is increased layer by layer from top to bottom, and the filter material particle layers are fluidized and are not mixed with each other when back blowing ash removal is carried out. The filter material particles with larger particle size can reduce pressure loss during air passing, and each layer of filter material particles are fluidized and not mixed during back blowing ash removal, so that each layer of filter material particles can be effectively cleaned, and the cleanliness of the filter material particles and the durability of the step filtering performance are ensured.
According to the preferable scheme, as shown in fig. 1, the filter layer 3 consists of an upper filter material particle layer 31 and a lower filter material particle layer 32, the thickness of the upper filter material particle layer 31 is 200-300 mm, preferably 250mm, the corona discharge electrode 7 is horizontally embedded in the upper filter material particle layer 31, the thickness of the lower filter material particle layer 32 is 40-50 mm, preferably 45mm, filter material particles in the upper filter material particle layer 31 adopt floating beads with the diameter of 2-3 mm, and filter material particles in the lower filter material particle layer 32 adopt baozzle sand with the diameter of 0.4-0.6 mm. The thicker upper filter material particle layer 31 can contain more dust, prolong the ash cleaning period, improve the dust holding capacity of the filter layer 3, protect the lower filter material particle layer 32, prevent large particle dust from directly impacting the lower filter material particle layer 32, prolong the service life of the whole filter layer 3, and the lower filter material particle layer 32 has smaller particle diameter and larger density, is suitable for capturing fine dust particles, improves the filtering precision, and the thinner lower filter material particle layer 32 can form a tighter structure, improves the capturing capacity of the fine dust and reduces the total pressure drop of the filter layer 3.
Further limited, the air distribution device 2 is composed of a pre-air distribution porous plate 23, a slotted screen 22 and an air distribution particle layer 21 which are distributed from bottom to top in sequence, wherein the aperture ratio of the pre-air distribution porous plate 23 is 1-3% (small value is taken at high temperature), a gap exists between the pre-air distribution porous plate 23 and the slotted screen 22, the air distribution particle layer 21 is paved on the slotted screen 22, and the filter material particle layer at the lowest layer is paved on the air distribution particle layer 21. Here, the aperture ratio of the pre-air-distributing porous plate 23 is 1-3%, and the design is helpful to form uniform air flow above the pre-air-distributing porous plate 23, reduce instability of the air flow, and avoid too high or too low flow velocity in local areas. The slit screen 22 and the air distribution particle layer 21 are arranged, firstly, the filter layer 3 is supported, secondly, air is further uniformly distributed, the slits of the slit screen 22 can guide air flow, the air distribution particle layer 21 can further disperse the air flow, the air flow can be ensured to uniformly pass through the filter layer 3, and thirdly, the leakage of fine filter material particles at the lower layer is prevented. A gap exists between the pre-air distribution perforated plate 23 and the slotted screen 22, and the static pressure sensor 61 can be conveniently arranged above the pre-air distribution perforated plate 23.
Further defined, static pressure sensors 61, 62 are provided above and below the pre-air distribution perforated plate 23, respectively, for testing the difference in static pressure between the air flow passing through the pre-air distribution perforated plate 23, and thereby monitoring the air velocity flowing through the filter layer 3.
The embodiment also provides a filtering method using the filter material corona charged particle beds, which combines a plurality of filter material corona charged particle beds into a particle bed filtering dust remover in parallel, ensures that each filter material corona charged particle bed can be subjected to filtering-back blowing fluidization dust removal circulation repeatedly, and ensures that dust-containing air flow is efficiently removed, the filtering method comprises a back blowing fluidization dust removal process, a filter material corona charged process and a filtering process,
The back blowing fluidization ash removal process comprises the following steps:
When the static pressure difference obtained by the two static pressure sensors 61 and 62 monitors that the filtering air speed of any filter material corona charged particle bed is reduced to a preset air speed threshold value (which can be set according to the situation), the filter material corona charged particle bed is switched from a filtering state to a back-blowing fluidization ash removing state through a switching valve, clean back-blowing air flow from a back-blowing air pipe enters from an air outlet 5 and sequentially flows through an air distribution device 2 and a filter layer 3, so that filter material particles in each layer of filter material particle layers of the filter layer 3 are fluidized, and dust deposited in gaps among the filter material particles is taken out of the filter material corona charged particle bed by the clean back-blowing air flow from an air inlet 4;
The corona charging process of the filter material is as follows:
When any filter material corona charged particle bed finishes back blowing fluidization ash removal, then a high-voltage pulse switching power supply 9 is connected, a corona discharge electrode 7 carries out intermittent corona discharge on filter material particles entering an intermittent corona charging zone 10, meanwhile, the filter material particles are mixed up and down and collide under a fluidization state, and continuously enter and exit the intermittent corona charging zone 10, so that charges are promoted to be transmitted from the intermittent corona charging zone 10 to the whole filter layer 3, all the filter material particles in the whole filter layer 3 are rapidly charged, and then the high-voltage pulse switching power supply 9 is turned off;
The filtering process is as follows:
when any filter material corona charged particle bed finishes filter material corona charged, the filter material corona charged particle bed is switched from a filter material corona charged state to a filtering state through a switching valve, dust-containing air flow enters the filter material corona charged particle bed from an air inlet 4, charged filter material particles in a filter layer 3 generate strong electrostatic attraction to dust with charges opposite to the polarity of the dust, the filtering efficiency is obviously enhanced, and purified air after high-efficiency dust removal flows through an air distribution device 2, flows out from an air outlet 5 and is finally led out from a gas purifying pipe.
The static pressure sensor is used for monitoring dust deposition amount and filtering air speed of the corona charged particle bed of the filter material, automatic back blowing fluidization ash removal process triggering is achieved, timeliness and accuracy of ash removal are improved, excessive accumulation of dust in the filter layer 3 is prevented through the regular back blowing fluidization ash removal process, air permeability and filtering performance of the filter material particles are maintained, blocking and abrasion of the filter material particles are reduced through the effective back blowing fluidization ash removal process, and service life of the filter material particles is prolonged. Through electrostatic enhancement filtration, the same dust removal effect can be achieved at higher filtration airflow rates, thereby reducing the equipment size. The mode of the charge transmission from the intermittent corona charging zone 10 to the whole filter layer 3 comprises 1) the charge of the intermittent corona charging zone 10, that is, the filter material particles continuously enter and exit the intermittent corona charging zone 10 in a fluidization state to directly obtain corona charge, and 2) the contact transfer charge, that is, the filter material particles turn 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 potential difference.
For the corona charged particle bed of the filter material in this 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 set to 40ms, the power-off time is set to 160ms, the output voltage is set to 0-90 kv, 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 embedding depth of the corona discharge electrode 7 in the filter layer 3 is 20mm, the temperature is 450 ℃, the fluidization air speed is 2.1u mf(umf and is the critical fluidization speed of the upper filter material), and the specific surface area charge quantity (μc/m 2) of the filter material particles with different depths (surface layer, 37.5mm, 75mm, 112.5mm and 175 mm) in the filter layer 3 is shown in fig. 2. As can be seen from fig. 2, the charge of the filter material particles at different depths in the filter layer 3 is substantially the same, indicating that the filter material particles are strongly mixed in the fluidized state, and the charge of the filter material particles in the filter layer 3 is uniform. It can also be seen from FIG. 2 that the filter material particles have a charge of up to 30 μC/m 2, which is 10 times greater than the fluidization friction charge of the filter material particles.
The initial filtering air speed is 0.45m/s, the final filtering air speed is 0.25m/s, the dust concentration in the dust-containing air flow entering from the air inlet 4 is 10g/m 3, the temperature is 450 ℃, and the filtering comparison of two working conditions is carried out, namely, the first working condition is that the filter material particles are positively charged and the dust is negatively charged, and the second working condition is that the filter material particles are not charged and the dust is not charged. The results show that the initial outlet dust concentration of the particle bed filtration under the first working condition is 12.5mg/Nm 3, the average outlet dust concentration of the filtration period is 4.82mg/Nm 3, the initial outlet dust concentration of the particle bed filtration under the second working condition is 44.38mg/Nm 3, the average outlet dust concentration of the filtration period is 13.47mg/Nm 3, and the electrostatic enhancement filtration effect of the first working condition is quite obvious.
Claims (9)
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| RU2039608C1 (en) * | 1993-12-24 | 1995-07-20 | Товарищество с ограниченной ответственностью "Элстат" | Two-zoned electric filter for cleaning air from aerosol and toxic gases |
| CN107617295A (en) * | 2017-08-29 | 2018-01-23 | 宁波大学 | A kind of static reinforced dust removal by filtration device of grain bed |
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| NL8701660A (en) * | 1987-07-14 | 1989-02-01 | Tno | COMBUSTION DEVICE WITH A FLUIDIZED BED. |
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| RU2039608C1 (en) * | 1993-12-24 | 1995-07-20 | Товарищество с ограниченной ответственностью "Элстат" | Two-zoned electric filter for cleaning air from aerosol and toxic gases |
| CN107617295A (en) * | 2017-08-29 | 2018-01-23 | 宁波大学 | A kind of static reinforced dust removal by filtration device of grain bed |
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