CA2004748A1 - Apparatus for precipitating solid particles and aerosols from gases - Google Patents
Apparatus for precipitating solid particles and aerosols from gasesInfo
- Publication number
- CA2004748A1 CA2004748A1 CA002004748A CA2004748A CA2004748A1 CA 2004748 A1 CA2004748 A1 CA 2004748A1 CA 002004748 A CA002004748 A CA 002004748A CA 2004748 A CA2004748 A CA 2004748A CA 2004748 A1 CA2004748 A1 CA 2004748A1
- Authority
- CA
- Canada
- Prior art keywords
- plates
- wires
- gas
- washing liquid
- charging wires
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000007789 gas Substances 0.000 title claims abstract description 45
- 239000002245 particle Substances 0.000 title claims abstract description 23
- 239000007787 solid Substances 0.000 title claims abstract description 20
- 239000000443 aerosol Substances 0.000 title claims abstract description 18
- 230000001376 precipitating effect Effects 0.000 title claims abstract description 6
- 238000007600 charging Methods 0.000 claims abstract description 40
- 239000007788 liquid Substances 0.000 claims abstract description 33
- 238000005406 washing Methods 0.000 claims abstract description 31
- 239000007921 spray Substances 0.000 claims description 7
- 238000001556 precipitation Methods 0.000 description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 13
- 239000002912 waste gas Substances 0.000 description 11
- 239000008237 rinsing water Substances 0.000 description 6
- 239000010419 fine particle Substances 0.000 description 3
- 239000012212 insulator Substances 0.000 description 3
- 230000002378 acidificating effect Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012856 packing Methods 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 1
- 239000006096 absorbing agent Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000011362 coarse particle Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 230000005686 electrostatic field Effects 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 229920000867 polyelectrolyte Polymers 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
Classifications
-
- 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
- B03C3/01—Pretreatment of the gases prior to electrostatic precipitation
- B03C3/014—Addition of water; Heat exchange, e.g. by condensation
-
- 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
- B03C3/34—Constructional details or accessories or operation thereof
- B03C3/40—Electrode constructions
- B03C3/45—Collecting-electrodes
- B03C3/53—Liquid, or liquid-film, electrodes
Landscapes
- Treating Waste Gases (AREA)
- Electrostatic Separation (AREA)
- Gas Separation By Absorption (AREA)
- Separation Of Particles Using Liquids (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A device for precipitating solid particles and aerosols from gases, comprising a plurality of parallel spaced plates with charging wires in the spaces between the plates. The plates and charging wires are electrically charged so that said solid particles and aerosols receive a charge as they pass the charging wires and as they continue movement between the plates they are attracted to the plates. A washing liquid flows over the plates to provide a moving film which carries away the particles. A fan moves the gas containing the solid particles and aerosols past the charging wires and between the plates.
A device for precipitating solid particles and aerosols from gases, comprising a plurality of parallel spaced plates with charging wires in the spaces between the plates. The plates and charging wires are electrically charged so that said solid particles and aerosols receive a charge as they pass the charging wires and as they continue movement between the plates they are attracted to the plates. A washing liquid flows over the plates to provide a moving film which carries away the particles. A fan moves the gas containing the solid particles and aerosols past the charging wires and between the plates.
Description
~0047~a APPARATUS FOR PRECIPITATING SOLID PARTICLES
AND AEROSOLS FROM GASES
The present invention relates to an apparatus for pre-cipitating solid particles and aerosols from gases.
Various types of wet and dry electrostatic filters are known for precipitating small solid particles and aerosols from gaseous or aerosol-like substances, particularly waste gases.
The present invention relates to such an apparatus for wet pre-cipitation.
German A-31 52 216 discloses an electric wet type filter in which the gas is first of all conducted through an ionizing device comprising a plurality of vertical, positively charged metal wires arranged at a distance to one another, between which negatively charged, similarly shaped wire counter-electrodes are positioned.
The gas from the ionizing device reaches the electro-static field of a filter which comprises a group of parallel plate electrodes, one plate being thereby alternately connected to the positive terminal of a voltage source while the other intermediate plate is connected to the negative terminal.
The plate electrodes are made of glass and are washed by a water film, whereby the actual electrode is formed by the conductive water film. The plates are washed by means of pipes which are disposed in the vicinity of the upper plate edge and in which nozzle openings are formed so that the jets of water from the pipes on the upper edge are directed obliquely downwards '~0(~4748 to the sides of the glass plates in the form of numerous fine streams.
The known electrostatic filter exhibits various dis-adwantages. Since the ionizing device lies in front of the actual collecting plates, the danger exists that ionized solid particles will accumulate predominantly on the leading edges of the plates in the direction of the gas supply, whereby particu-larly the edges are not washed entirely because the plates are sprayed, as described, via nozzles, and thus it cannot always be guaranteed that the solid particles will be carried away immediately and completely with the washing liquid. In addition, there is a danger that by spraying the waste gas to be treated horizontally the water film on the plate edges will separate.
At the same time there is a danger of short circuits.
A so-called tube filter is known from French A-25 75 675, the entire surface of its inner wall being washed by means of a water reservoir arranged on the peripheral side but having, how-ever, only very small precipitation surfaces, thus resulting in a low specific gas throughput capacity and simultaneously a high expense pertaining to the apparatus.
An object of the present invention is to provide a wet ionization scrubber which allows a high gas throughput and a high degree of precipitation of solid particles from the gases or aerosols conducted through the scrubber while maintain-inq the cost of the apparatus as low as possible.
The present invention provides an apparatus that com-~0(14748 prises a plurality of plates arranged parallel and at a distance to one another and connected as electrodes with a specific charge. These plates are washed continuously and over their entire surfac~s with a washing liquid, charging wires which have a different charge to that of the plates extend in the spaces between the adjacent plates. The solid particles intro-duced into the spaces between the plates by the flow of gas are hereby provided in the area between the plates with a charge corresponding to that of the charged wires and are subsequently attracted directly by the plates connected as counterelectrodes.
Because the entire surface of the plates are washed with a wash-ing liquid, the particles are quickly and completely carried away to a collecting tank for discharge of the washing liquid together with the solid particles.
The arrangement of the ionization wires between the individual plates ensures that the charged solid particles purposefully move along the shortest path to the plate electrodes and cannot adhere to the edges or the unwashed surfaces.
With a higher gas throughput capacity, a higher degree of precipitation which can be adjusted by the selected spacing of the plates and the voltage applied is made possible through this.
The apparatus according to the present invention is characterized in detail by the features of claim 1.
According to a first examplary embodiment, it is pro-posed to arrange the charging wires vertically between the '~0047~8 plates, whereby this preferably occurs in such a way that the wires lie in a vertical plane. The gas is preferably fed hoxizontally and the wires are then arranged between the plates at the end section facing the gas feed so that the solid parti-cles are ionized uniformly and immediately following entry of the gas flow between the plates.
There is also a danger in this case, particularly with a high gas throughput, that the water film on the plate electrodes at the gas inlet side could separate in places. Because of the arrangement of wires between the plates, the apparatus according to the present invention does not exhibit the disadvantage that larger quantities of solid particles are precipitated on the un-washed area of the plates. However, in a preferred exemplary embodiment the present invention likewise proposes arranging the ionization wires horizontally between the vertically oriented plates and then guiding the gas in co-current or countercurrent flow with the washing liquid through the spaces between the plates.
In this connection it is proposed that the device for continuously and completely washing the plates with a washing liquid, which preferably has its own electric conductivity, be designed (from top to bottom) with distribution channels that are open at the top and are arranged directly on the upper edqe of each plate. The washing liquid then runs over the edge of the channels, over the outer surface of the channels and then over the entire length of the plates to thereby uniformly and ~004748 completely cover their surfaces. The channels can be wider than the plates.
Even when feeding the gas countercurrently, a separa-tion of the liquid film is avoided since the lower edges of the plates are always washed over their entire length/width and new water is continuously supplied from the top.
In an advantageous exemplary embodiment the wires are situated between the adjacent plates at an angle less than 90 to the horizontal. The advantage of this is that any water droplets that should be deposited on the charging wires (also called electrical discharge wires) are immediately carried off to the lower-lying end so that the danger of a short circuit between adjacent plates with the same charge is prevented. The electrical discharge wires are preferably inclined between 10 and 30 to the horizontal.
The level of high voltage which can be applied to the electrical charging wires depends on the spacing between the plates. The plate spacing and the applied voltage also depend on the quality and quantity of gas/aerosol to be cleaned. At a corresponding high voltage, a single "discharge plane" of electrical charging wires suffices, that is only one charging wire runs between adjacent plates. If a lower power supply must be selected or to even further improve the degree of precipita-tion, it is proposed in a further alternative to arrange a plural-ity of "charging planes" between the plates. A plurality of electrical charging wires then positioned at a distance to one another between adjacent plates, whereby adjacent electrical ~OOA748 charging wires between adjacent plates are again preferably each arranged in one plane. The individual ~Icharging planes can thereby be connected jointly or separately to a voltage source.
The advantage of the distribution channels on the upper edges of the plates, described above, having the washing liquid flowing over their edge onto the plates is that disper-sions can also be used for washing. The apparatus according to the present invention thus has a further advantage over the electric filter known from German A-31 52 216 in which the wash-ing liquid is sprayed onto the plates via nozzles, since these nozzles can easily become clogged when using dispersions.
The distribution channel can consist of a pipe whose upper side is cut open. The distribution channel can be designed with a weir to uniformly distribute the rinsing liquid. To achieve large precipitation surfaces it is in particular pro-posed to arrange precipitation aids between the washed plates and at an adequate distance to the electrical discharge wires, these precipitation aids being wetted by the washing liquid.
Aqueous solutions of acidic or basic electrolytes, solutions containing surfactants or polyelectrolytes can be used, for example, as the washing liquid.
Furthermore, it is proposed that an evaporative cooler through which the gas/aerosol is conducted precede the apparatus.
The evaporative cooler represents a type of high-capacity ab-sorber and can consist of a spray tower or a fixed bed which is ~`0~47~8 _ 7 - 27560-~3 sprayed with a washing liquid. The gas/aerosol is in this case cooled to the dew point. Coarser solid particles are thereby already precipitated. Aerosol-like solid particles are con-ducted through the fixed bed or the spray tower and are then preferably precipitated in countercurrent flow through the fol-lowing wet ionization scrubber of the type described above.
This alternative represents a two-stage process which is advanta-geous particularly with heavily loaded waste gases as well as tarry, acidic, basic and saline aerosols from waste gases. The entire device preferably comprises a vertical tower with a first charging plane through which the waste gas is first of all con-ducted before it reaches the wet ionization scrubber. The wash-ing liquid from the wet ionization scrubber can thereby be used again in the preceding charging stage; however, it is also equally possible to design the spray tower with a separate feeding mechanism for a washing liquid and to drain the washing liquid from the wet ionization scrubber separately.
If the evaporative cooler is formed from a fixed bed, then it can consist, for example, of a packed bed or an ordered packing, for example a fabric packing.
The present invention will be explained in greater detail herebelow with reference to two exemplary embodiments.
In drawings illustrating the invention:
Figure 1: a partially cut away side view of a first exemplary embodiment of a wet type electro-static filter, ;~004'~8 Figure 2: a per~p~ctive view showing the position-ing of precipitation plates and electrical discharge wires of the apparatus according to Figure 1, Figure 3: a side view of a second exemplary embodi-ment of a wet ionization scrubber preceded by a high-capacity absorber, Figure 4: illustrates an alternative positioning of the electrical discharge wires relative to the precipitation plates in the apparatus according to Figure 3.
The apparatus according to Figure 1 comprises a c~lin-drical housing 10 with a rectangular cross-section which merges at both endsvia a cones 12 into a feed connector 14 or an out-let connector 16 for the waste gas to be cleaned. A fan 18 for conveying the waste gas G through the housing 10 is disposed in the inlet connector 14.
A plurality of vertically oriented plates 20 are arrang-ed parallel and spaced from one another in the centre portion of the housing 10. The plates 20 are connected to one another by means of spacers. The plates are spaced equidistantly and an electrical charging wire 22 is connected between adjacent plates 20 such that the electrical charging wires 22 are positioned one below the other in a plane. As can be seen from Figure 1, the vertically extending electrical charging wires 22 are positioned at the gas inlet end of the plates 20 at a distance behind the , .
~004~74~3 front faces 20a. The electrical charging wires 22 run equi-distantly between adjacent plates 20 and extend above and below the plates 20 where they are fastened to the frame by horizontally extending clamps 24 (Figure 2) isulated on the outside by insulators 26.
The plates 20 are smooth and free of notches. A
distribution channel 28 is arranged on the upper edge 20b of each plate 20. This channel can be configured as a weir taper-ing conically to the plate edge 20b. Figure 2 illustrates one embodiment in which the distribution channel 28 is formed from a pipe that is firmly connected to the associated plate 20. The diameter of the pipe 28 is greater than the thickness of the associated plate 20 so that the distribution channel 28 extends somewhat beyond the plate 20 on both sides. The channel 28 is open at the top and a washing liquid is supplied by means of a feeding mechanism (not illustrated). This washing liquid flows over both of the edges of the channel 28, along its outer wall and then reaches the outer surfaces of the plates 20 which are thus washed completely and uniformly. These sections can be covered with an increased film of rinsing water by changing the incline over the length as well as by forming a notch trans-versely to the channel or by mounting a displaceable ring on the end facing the ionizing device. This structural feature is particularly adapted to deal with the increased precipitation of pollutants at the front end section of the plates 20 in the direction of gas supply.
;~304t7~8 - - 10 - 27560- ~3 To obtain precipitation, the plates 20, on the one hand, and the electrical discharge wires 22, on the other hand, must be provided with different charges. In the exemplary embodiment illustrated in Figures 1, 2, the electrical charging wires 22 are positively charged and the plates 20 are negatively charged, or rather the plates 20 form the earth potential for which a voltage source (not illustrated) is used. The fine particles, which are contained in the gas blown into the housing 10 via the gas inlet connection piece 14, are charged (in this case, positively) while passing the electrical charging wires 22 and are subsequently attracted by the plates 20 acting as counter electrodes where they contact the continuous water film and are carried downwards by the water film. To this end, the base 30 of the housing has openings, not illustrated in detail, through which the washing liquid reaches a collecting tank 32. The flow of rinsing water containing the solid particles preferably then passes through a settling tank.
Figure 3 illustrates a further exemplary embodiment of the apparatus which is in this case arranged in the upper portion of a tower 34. Analogous to the exemplary embodiment according to Figures 1, 2, the apparatus comprises a plurality of water-washed plates 20 arranged parallel and at a distance to one another. These plates are suspended at the upper end from a supporting structure 36. Analogous to Figures 1, 2, a rinsing channel 28 runs above each plate. The water supply is schema-tically illustrated at 38.
, 2004'7~8 - ll - 2756n-23 In this case also an electrical charging wire 22 runs between adjacent plates 20; however, in contrast to the exemp-lary embodiment according to Figures l, 2, it is arranged hori-zontally, namely in the area of the lower end section of the plates 20. The ends of the electrical discharge wires 22 extend-ing beyond the plates 20 are stretched over clamps 40 that are insulated from the frame by means of insulators.
These electrical charging wires 22 are arranged in such a way that they lie in a horizontal plane.
As shown in Figure 3, in addition to the electrical charging wires 22, additional electrical charging wires 22a are arranged between the upper end sections of the plates 20 in a manner corresponding to that of the electrical charging wires 22, and thus results in a second charge/ionization plane.
An evaporation cooling zone 42, which extends over the entire cross-section of the tower 34 and is configured in this case as a countercurrent spray tower, is arranged in the tower at a specific distance below the apparatus described above.
A spray head 44, which is supplied with a separate flow 48 of washing liquid via a line 26, is arranged in the centre of the tower 34 above the evaporation cooling zone 42. The washing liquid is sprayed in a star shape by means of the spray head 44 over the entire cross-sectional area of the evaporative cooler 42 which consists of a gas permeable plastic network.
This installation Operates as follows; The waste gas/aerosol is conveyed via an inlet connector 14 located at :
~:0047~8 the lower end of the tower 34 through the tower 34 by means of a fan and thereafter flows through the tower 34 from bottom to top. In this way the waste gas first flows through the evapora-tive cooler 42 where a first precipitation of coarse particles occurs. The coarser particles are absorbed by the sprayed washing liquid and on account of gravity are returned with the flow of washing water against the gas direction G to the base area of the tower 34 and discharged laterally via an outlet 50 below the gas inlet connection piece 14.
The already preconditioned waste gas continues to flow upwards by the action of the fan and then reaches the actual wet ionization scrubber in which the particle-like gas constitu-ents are first of all ionized in the area of the first discharge plane (electrical charging wires 22) and are subsequently pre-cipitated in the manner described earlier by means of precipita-tion on the film of rinsing water flowing off the plates.
The thus further cleaned gas continues to flow upwards through the tower 34 until it reaches the area of the second discharge plane (electrical charging wires 22a) where any solid particles still remaining in the gas are removed in the same manner.
The cleaned waste gas subsequently leaves the apparatus at the top and is drawn off via the gas outlet connection piece 16 at the upper end of the tower 34 and the very fine particles precipitated on the plates 20 or the film of rinsing water are discharged downwardly via the flow of rinsing water which is ~QO.~74a conducted through the evaporative cooler 42 to the outlet 50 to wh:ich a clarifying stage is connected.
The effectiveness of precipitation of the installation described is particularly high since the distribution channels described guarantee that the entire surface of the plates 20 is washed and the very fine particles precipitated in the area of the discharge planes thus always reach the counter electrodes (plates 20) on the shortest path and are carried away with the flow of rinsing water. Thus, the gas is guided countercurrently to the rinsing liquid. It would also be equally possible, how-ever, to conduct the gas and the rinsing liquid co-currently.
In contrast, the apparatus according to Figures 1, 2 operates in a crosscurrent manner, i.e. the gas is guided through the ionizing devices (plates 20, electrical charging wires 22) per-pendicularly to the direction of flow of the washing liquid.
Instead of arranging the electrical charging wires 22, 22a horizontally, they can also be arranged at an angle ~ to the horizontal as illustrated in Figure 4. The advantage of this exemplary embodiment is that water droplets which may be deposited on the electrical discharge wires 22, 22a, are carried to the lower-lying end of the electrical discharge wire and thus away from the actual ionizing device. In this manner the danger of a short circuit between the electrical discharge wires 22 and the adjacent plates 20 is avoided.
Furthermore, the electrical charging wires are fastened and charged as described above.
~004748 The plate spacing depends on the voltage applied to the electrical discharge wires 22, 22a. In view of the limited dielectric strength of the unheated insulators inserted in the ionizing device, working voltages of up to + 20 kV or - 20 kV
preferably are used in handling of moist gases. Accordingly, as a function of the gas to be treated, plate spacings of 15 to 60 mm are preferred. The plates themselves can consist of almost any type of material and are as a rule grounded. In any event, the plate material should be easily wettable and resist-ant for the respective field of use. Furthermore, the plates should have as smooth a surface as possible in order to prevent the rinsing liquid from separating.
AND AEROSOLS FROM GASES
The present invention relates to an apparatus for pre-cipitating solid particles and aerosols from gases.
Various types of wet and dry electrostatic filters are known for precipitating small solid particles and aerosols from gaseous or aerosol-like substances, particularly waste gases.
The present invention relates to such an apparatus for wet pre-cipitation.
German A-31 52 216 discloses an electric wet type filter in which the gas is first of all conducted through an ionizing device comprising a plurality of vertical, positively charged metal wires arranged at a distance to one another, between which negatively charged, similarly shaped wire counter-electrodes are positioned.
The gas from the ionizing device reaches the electro-static field of a filter which comprises a group of parallel plate electrodes, one plate being thereby alternately connected to the positive terminal of a voltage source while the other intermediate plate is connected to the negative terminal.
The plate electrodes are made of glass and are washed by a water film, whereby the actual electrode is formed by the conductive water film. The plates are washed by means of pipes which are disposed in the vicinity of the upper plate edge and in which nozzle openings are formed so that the jets of water from the pipes on the upper edge are directed obliquely downwards '~0(~4748 to the sides of the glass plates in the form of numerous fine streams.
The known electrostatic filter exhibits various dis-adwantages. Since the ionizing device lies in front of the actual collecting plates, the danger exists that ionized solid particles will accumulate predominantly on the leading edges of the plates in the direction of the gas supply, whereby particu-larly the edges are not washed entirely because the plates are sprayed, as described, via nozzles, and thus it cannot always be guaranteed that the solid particles will be carried away immediately and completely with the washing liquid. In addition, there is a danger that by spraying the waste gas to be treated horizontally the water film on the plate edges will separate.
At the same time there is a danger of short circuits.
A so-called tube filter is known from French A-25 75 675, the entire surface of its inner wall being washed by means of a water reservoir arranged on the peripheral side but having, how-ever, only very small precipitation surfaces, thus resulting in a low specific gas throughput capacity and simultaneously a high expense pertaining to the apparatus.
An object of the present invention is to provide a wet ionization scrubber which allows a high gas throughput and a high degree of precipitation of solid particles from the gases or aerosols conducted through the scrubber while maintain-inq the cost of the apparatus as low as possible.
The present invention provides an apparatus that com-~0(14748 prises a plurality of plates arranged parallel and at a distance to one another and connected as electrodes with a specific charge. These plates are washed continuously and over their entire surfac~s with a washing liquid, charging wires which have a different charge to that of the plates extend in the spaces between the adjacent plates. The solid particles intro-duced into the spaces between the plates by the flow of gas are hereby provided in the area between the plates with a charge corresponding to that of the charged wires and are subsequently attracted directly by the plates connected as counterelectrodes.
Because the entire surface of the plates are washed with a wash-ing liquid, the particles are quickly and completely carried away to a collecting tank for discharge of the washing liquid together with the solid particles.
The arrangement of the ionization wires between the individual plates ensures that the charged solid particles purposefully move along the shortest path to the plate electrodes and cannot adhere to the edges or the unwashed surfaces.
With a higher gas throughput capacity, a higher degree of precipitation which can be adjusted by the selected spacing of the plates and the voltage applied is made possible through this.
The apparatus according to the present invention is characterized in detail by the features of claim 1.
According to a first examplary embodiment, it is pro-posed to arrange the charging wires vertically between the '~0047~8 plates, whereby this preferably occurs in such a way that the wires lie in a vertical plane. The gas is preferably fed hoxizontally and the wires are then arranged between the plates at the end section facing the gas feed so that the solid parti-cles are ionized uniformly and immediately following entry of the gas flow between the plates.
There is also a danger in this case, particularly with a high gas throughput, that the water film on the plate electrodes at the gas inlet side could separate in places. Because of the arrangement of wires between the plates, the apparatus according to the present invention does not exhibit the disadvantage that larger quantities of solid particles are precipitated on the un-washed area of the plates. However, in a preferred exemplary embodiment the present invention likewise proposes arranging the ionization wires horizontally between the vertically oriented plates and then guiding the gas in co-current or countercurrent flow with the washing liquid through the spaces between the plates.
In this connection it is proposed that the device for continuously and completely washing the plates with a washing liquid, which preferably has its own electric conductivity, be designed (from top to bottom) with distribution channels that are open at the top and are arranged directly on the upper edqe of each plate. The washing liquid then runs over the edge of the channels, over the outer surface of the channels and then over the entire length of the plates to thereby uniformly and ~004748 completely cover their surfaces. The channels can be wider than the plates.
Even when feeding the gas countercurrently, a separa-tion of the liquid film is avoided since the lower edges of the plates are always washed over their entire length/width and new water is continuously supplied from the top.
In an advantageous exemplary embodiment the wires are situated between the adjacent plates at an angle less than 90 to the horizontal. The advantage of this is that any water droplets that should be deposited on the charging wires (also called electrical discharge wires) are immediately carried off to the lower-lying end so that the danger of a short circuit between adjacent plates with the same charge is prevented. The electrical discharge wires are preferably inclined between 10 and 30 to the horizontal.
The level of high voltage which can be applied to the electrical charging wires depends on the spacing between the plates. The plate spacing and the applied voltage also depend on the quality and quantity of gas/aerosol to be cleaned. At a corresponding high voltage, a single "discharge plane" of electrical charging wires suffices, that is only one charging wire runs between adjacent plates. If a lower power supply must be selected or to even further improve the degree of precipita-tion, it is proposed in a further alternative to arrange a plural-ity of "charging planes" between the plates. A plurality of electrical charging wires then positioned at a distance to one another between adjacent plates, whereby adjacent electrical ~OOA748 charging wires between adjacent plates are again preferably each arranged in one plane. The individual ~Icharging planes can thereby be connected jointly or separately to a voltage source.
The advantage of the distribution channels on the upper edges of the plates, described above, having the washing liquid flowing over their edge onto the plates is that disper-sions can also be used for washing. The apparatus according to the present invention thus has a further advantage over the electric filter known from German A-31 52 216 in which the wash-ing liquid is sprayed onto the plates via nozzles, since these nozzles can easily become clogged when using dispersions.
The distribution channel can consist of a pipe whose upper side is cut open. The distribution channel can be designed with a weir to uniformly distribute the rinsing liquid. To achieve large precipitation surfaces it is in particular pro-posed to arrange precipitation aids between the washed plates and at an adequate distance to the electrical discharge wires, these precipitation aids being wetted by the washing liquid.
Aqueous solutions of acidic or basic electrolytes, solutions containing surfactants or polyelectrolytes can be used, for example, as the washing liquid.
Furthermore, it is proposed that an evaporative cooler through which the gas/aerosol is conducted precede the apparatus.
The evaporative cooler represents a type of high-capacity ab-sorber and can consist of a spray tower or a fixed bed which is ~`0~47~8 _ 7 - 27560-~3 sprayed with a washing liquid. The gas/aerosol is in this case cooled to the dew point. Coarser solid particles are thereby already precipitated. Aerosol-like solid particles are con-ducted through the fixed bed or the spray tower and are then preferably precipitated in countercurrent flow through the fol-lowing wet ionization scrubber of the type described above.
This alternative represents a two-stage process which is advanta-geous particularly with heavily loaded waste gases as well as tarry, acidic, basic and saline aerosols from waste gases. The entire device preferably comprises a vertical tower with a first charging plane through which the waste gas is first of all con-ducted before it reaches the wet ionization scrubber. The wash-ing liquid from the wet ionization scrubber can thereby be used again in the preceding charging stage; however, it is also equally possible to design the spray tower with a separate feeding mechanism for a washing liquid and to drain the washing liquid from the wet ionization scrubber separately.
If the evaporative cooler is formed from a fixed bed, then it can consist, for example, of a packed bed or an ordered packing, for example a fabric packing.
The present invention will be explained in greater detail herebelow with reference to two exemplary embodiments.
In drawings illustrating the invention:
Figure 1: a partially cut away side view of a first exemplary embodiment of a wet type electro-static filter, ;~004'~8 Figure 2: a per~p~ctive view showing the position-ing of precipitation plates and electrical discharge wires of the apparatus according to Figure 1, Figure 3: a side view of a second exemplary embodi-ment of a wet ionization scrubber preceded by a high-capacity absorber, Figure 4: illustrates an alternative positioning of the electrical discharge wires relative to the precipitation plates in the apparatus according to Figure 3.
The apparatus according to Figure 1 comprises a c~lin-drical housing 10 with a rectangular cross-section which merges at both endsvia a cones 12 into a feed connector 14 or an out-let connector 16 for the waste gas to be cleaned. A fan 18 for conveying the waste gas G through the housing 10 is disposed in the inlet connector 14.
A plurality of vertically oriented plates 20 are arrang-ed parallel and spaced from one another in the centre portion of the housing 10. The plates 20 are connected to one another by means of spacers. The plates are spaced equidistantly and an electrical charging wire 22 is connected between adjacent plates 20 such that the electrical charging wires 22 are positioned one below the other in a plane. As can be seen from Figure 1, the vertically extending electrical charging wires 22 are positioned at the gas inlet end of the plates 20 at a distance behind the , .
~004~74~3 front faces 20a. The electrical charging wires 22 run equi-distantly between adjacent plates 20 and extend above and below the plates 20 where they are fastened to the frame by horizontally extending clamps 24 (Figure 2) isulated on the outside by insulators 26.
The plates 20 are smooth and free of notches. A
distribution channel 28 is arranged on the upper edge 20b of each plate 20. This channel can be configured as a weir taper-ing conically to the plate edge 20b. Figure 2 illustrates one embodiment in which the distribution channel 28 is formed from a pipe that is firmly connected to the associated plate 20. The diameter of the pipe 28 is greater than the thickness of the associated plate 20 so that the distribution channel 28 extends somewhat beyond the plate 20 on both sides. The channel 28 is open at the top and a washing liquid is supplied by means of a feeding mechanism (not illustrated). This washing liquid flows over both of the edges of the channel 28, along its outer wall and then reaches the outer surfaces of the plates 20 which are thus washed completely and uniformly. These sections can be covered with an increased film of rinsing water by changing the incline over the length as well as by forming a notch trans-versely to the channel or by mounting a displaceable ring on the end facing the ionizing device. This structural feature is particularly adapted to deal with the increased precipitation of pollutants at the front end section of the plates 20 in the direction of gas supply.
;~304t7~8 - - 10 - 27560- ~3 To obtain precipitation, the plates 20, on the one hand, and the electrical discharge wires 22, on the other hand, must be provided with different charges. In the exemplary embodiment illustrated in Figures 1, 2, the electrical charging wires 22 are positively charged and the plates 20 are negatively charged, or rather the plates 20 form the earth potential for which a voltage source (not illustrated) is used. The fine particles, which are contained in the gas blown into the housing 10 via the gas inlet connection piece 14, are charged (in this case, positively) while passing the electrical charging wires 22 and are subsequently attracted by the plates 20 acting as counter electrodes where they contact the continuous water film and are carried downwards by the water film. To this end, the base 30 of the housing has openings, not illustrated in detail, through which the washing liquid reaches a collecting tank 32. The flow of rinsing water containing the solid particles preferably then passes through a settling tank.
Figure 3 illustrates a further exemplary embodiment of the apparatus which is in this case arranged in the upper portion of a tower 34. Analogous to the exemplary embodiment according to Figures 1, 2, the apparatus comprises a plurality of water-washed plates 20 arranged parallel and at a distance to one another. These plates are suspended at the upper end from a supporting structure 36. Analogous to Figures 1, 2, a rinsing channel 28 runs above each plate. The water supply is schema-tically illustrated at 38.
, 2004'7~8 - ll - 2756n-23 In this case also an electrical charging wire 22 runs between adjacent plates 20; however, in contrast to the exemp-lary embodiment according to Figures l, 2, it is arranged hori-zontally, namely in the area of the lower end section of the plates 20. The ends of the electrical discharge wires 22 extend-ing beyond the plates 20 are stretched over clamps 40 that are insulated from the frame by means of insulators.
These electrical charging wires 22 are arranged in such a way that they lie in a horizontal plane.
As shown in Figure 3, in addition to the electrical charging wires 22, additional electrical charging wires 22a are arranged between the upper end sections of the plates 20 in a manner corresponding to that of the electrical charging wires 22, and thus results in a second charge/ionization plane.
An evaporation cooling zone 42, which extends over the entire cross-section of the tower 34 and is configured in this case as a countercurrent spray tower, is arranged in the tower at a specific distance below the apparatus described above.
A spray head 44, which is supplied with a separate flow 48 of washing liquid via a line 26, is arranged in the centre of the tower 34 above the evaporation cooling zone 42. The washing liquid is sprayed in a star shape by means of the spray head 44 over the entire cross-sectional area of the evaporative cooler 42 which consists of a gas permeable plastic network.
This installation Operates as follows; The waste gas/aerosol is conveyed via an inlet connector 14 located at :
~:0047~8 the lower end of the tower 34 through the tower 34 by means of a fan and thereafter flows through the tower 34 from bottom to top. In this way the waste gas first flows through the evapora-tive cooler 42 where a first precipitation of coarse particles occurs. The coarser particles are absorbed by the sprayed washing liquid and on account of gravity are returned with the flow of washing water against the gas direction G to the base area of the tower 34 and discharged laterally via an outlet 50 below the gas inlet connection piece 14.
The already preconditioned waste gas continues to flow upwards by the action of the fan and then reaches the actual wet ionization scrubber in which the particle-like gas constitu-ents are first of all ionized in the area of the first discharge plane (electrical charging wires 22) and are subsequently pre-cipitated in the manner described earlier by means of precipita-tion on the film of rinsing water flowing off the plates.
The thus further cleaned gas continues to flow upwards through the tower 34 until it reaches the area of the second discharge plane (electrical charging wires 22a) where any solid particles still remaining in the gas are removed in the same manner.
The cleaned waste gas subsequently leaves the apparatus at the top and is drawn off via the gas outlet connection piece 16 at the upper end of the tower 34 and the very fine particles precipitated on the plates 20 or the film of rinsing water are discharged downwardly via the flow of rinsing water which is ~QO.~74a conducted through the evaporative cooler 42 to the outlet 50 to wh:ich a clarifying stage is connected.
The effectiveness of precipitation of the installation described is particularly high since the distribution channels described guarantee that the entire surface of the plates 20 is washed and the very fine particles precipitated in the area of the discharge planes thus always reach the counter electrodes (plates 20) on the shortest path and are carried away with the flow of rinsing water. Thus, the gas is guided countercurrently to the rinsing liquid. It would also be equally possible, how-ever, to conduct the gas and the rinsing liquid co-currently.
In contrast, the apparatus according to Figures 1, 2 operates in a crosscurrent manner, i.e. the gas is guided through the ionizing devices (plates 20, electrical charging wires 22) per-pendicularly to the direction of flow of the washing liquid.
Instead of arranging the electrical charging wires 22, 22a horizontally, they can also be arranged at an angle ~ to the horizontal as illustrated in Figure 4. The advantage of this exemplary embodiment is that water droplets which may be deposited on the electrical discharge wires 22, 22a, are carried to the lower-lying end of the electrical discharge wire and thus away from the actual ionizing device. In this manner the danger of a short circuit between the electrical discharge wires 22 and the adjacent plates 20 is avoided.
Furthermore, the electrical charging wires are fastened and charged as described above.
~004748 The plate spacing depends on the voltage applied to the electrical discharge wires 22, 22a. In view of the limited dielectric strength of the unheated insulators inserted in the ionizing device, working voltages of up to + 20 kV or - 20 kV
preferably are used in handling of moist gases. Accordingly, as a function of the gas to be treated, plate spacings of 15 to 60 mm are preferred. The plates themselves can consist of almost any type of material and are as a rule grounded. In any event, the plate material should be easily wettable and resist-ant for the respective field of use. Furthermore, the plates should have as smooth a surface as possible in order to prevent the rinsing liquid from separating.
Claims (14)
1. An apparatus for precipitating solid particles and aerosols from gases characterized by:
1.1. a plurality of plates arranged parallel and spaced from one another, 1.2. at least one charging wire extending between adjacent plates, 1.3. whereby the plates and the charging wires have different electrical charges thereon, 1.4. a fan for guiding through the gas/aerosol past the ionization wires and through the spaces between the plates, 1.5. a device for continuously and completely washing the plates with a washing liquid from top to bottom, and 1.6. a collecting tank for discharge of the washing liquid from the apparatus.
1.1. a plurality of plates arranged parallel and spaced from one another, 1.2. at least one charging wire extending between adjacent plates, 1.3. whereby the plates and the charging wires have different electrical charges thereon, 1.4. a fan for guiding through the gas/aerosol past the ionization wires and through the spaces between the plates, 1.5. a device for continuously and completely washing the plates with a washing liquid from top to bottom, and 1.6. a collecting tank for discharge of the washing liquid from the apparatus.
2. An apparatus according to claim 1, whereby the charg-ing wires are arranged vertically between the plates.
3. An apparatus according to claim 1, whereby the charg-ing wires are arranged horizontally between the plates.
4. An apparatus according to claim 1, whereby the charg-ing wires are arranged between the plates at an angle less than 90° to the horizontal.
5. An apparatus according to one of the claims 2 to 4, whereby the charging wires are arranged between the plates on the end section facing the gas supply.
6. An apparatus according to one of the claims 2 or 3, whereby the charging wires are arranged such that they are situated in a plane.
7. An apparatus according to one of the claims 2 or 3, whereby a plurality of charging wires are arranged between adjacent plates at a distance to one another and adjacent charging wires are respectively arranged between adjacent plates in a plane.
8. An apparatus according to claim 2 or 3, whereby the fan is arranged in such a way that the gas/aerosol is fed horizontally into the spaces between the plates.
9. An apparatus according to one of the claims 2 or 3, whereby the fan is arranged in such a way that the gas/aerosol is fed vertically into the spaces between the plates in co-current or countercurrent flow to the flowing direction of the washing liquid on the plates.
10. An apparatus according to claim 1, whereby the device consists of a plurality of distribution channels for the rinsing liquid, these channels being open at the top and whereby one distribution channel is respectively arranged over one plate.
11. An apparatus according to claim 10 in which the distribution channels are flush mounted to the upper edges of the associated plates.
12. An apparatus according to claim 1, whereby the apparatus is preceded by an evaporative cooler through which the gas/aerosol is conducted.
13. An apparatus according to claim 12, whereby the evaporative cooler consists of a spray tower or a fixed bed.
14. An apparatus according to claim 12 or 13, whereby the evaporative cooler is designed with a separate feeding mechanism for a washing liquid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT300388A AT390205B (en) | 1988-12-07 | 1988-12-07 | DEVICE FOR SEPARATING FINE DUST AND AEROSOLS FROM EXHAUST GAS |
| ATA3003/88 | 1988-12-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2004748A1 true CA2004748A1 (en) | 1990-06-07 |
Family
ID=3543805
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002004748A Abandoned CA2004748A1 (en) | 1988-12-07 | 1989-12-06 | Apparatus for precipitating solid particles and aerosols from gases |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0447436A1 (en) |
| AT (1) | AT390205B (en) |
| AU (1) | AU4759490A (en) |
| CA (1) | CA2004748A1 (en) |
| DK (1) | DK503189A (en) |
| FI (1) | FI894862A0 (en) |
| WO (1) | WO1990006181A1 (en) |
| YU (1) | YU47211B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2864453B1 (en) * | 2003-12-26 | 2006-02-24 | Eurovia | PROCESS FOR THE TREATMENT OF SMOKE GENERATED DURING THE MANUFACTURE, TRANSFORMATION AND / OR HANDLING OF PRODUCTS OF PETROLEUM ORIGIN |
| DE102008046409C5 (en) | 2008-09-04 | 2013-08-22 | Eisenmann Ag | Method of removing solids from overspray resulting from painting articles |
| DE102013225607A1 (en) * | 2013-12-11 | 2015-06-11 | Aws Group Ag | System, apparatus and method for purifying a gas stream |
| CN111228977A (en) * | 2020-03-19 | 2020-06-05 | 浙江嘉福新材料科技有限公司 | Sulfuric acid tail gas treatment device and treatment process |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH362682A (en) * | 1958-10-04 | 1962-06-30 | Gema Ag Apparatebau Und Stanze | Electrostatic precipitators, in particular for cleaning flue gases |
| JPS5327285U (en) * | 1976-08-13 | 1978-03-08 | ||
| FI61815C (en) * | 1980-07-15 | 1982-10-11 | Arvi Artama | ELECTRIC FILTER |
| US4360366A (en) * | 1981-10-07 | 1982-11-23 | Dresser Industries, Inc. | Liquid distributor for a wet electrostatic precipitator |
-
1988
- 1988-12-07 AT AT300388A patent/AT390205B/en not_active IP Right Cessation
-
1989
- 1989-09-29 YU YU189589A patent/YU47211B/en unknown
- 1989-10-10 DK DK503189A patent/DK503189A/en not_active Application Discontinuation
- 1989-10-13 FI FI894862A patent/FI894862A0/en not_active IP Right Cessation
- 1989-12-06 AU AU47594/90A patent/AU4759490A/en not_active Abandoned
- 1989-12-06 WO PCT/EP1989/001498 patent/WO1990006181A1/en not_active Application Discontinuation
- 1989-12-06 CA CA002004748A patent/CA2004748A1/en not_active Abandoned
- 1989-12-06 EP EP19900900185 patent/EP0447436A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| DK503189D0 (en) | 1989-10-10 |
| ATA300388A (en) | 1989-09-15 |
| AU4759490A (en) | 1990-06-26 |
| YU189589A (en) | 1991-02-28 |
| WO1990006181A1 (en) | 1990-06-14 |
| FI894862A0 (en) | 1989-10-13 |
| YU47211B (en) | 1995-01-31 |
| DK503189A (en) | 1990-06-08 |
| EP0447436A1 (en) | 1991-09-25 |
| AT390205B (en) | 1990-04-10 |
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| Date | Code | Title | Description |
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| EEER | Examination request | ||
| FZDE | Dead |