CA1038306A - Wet electrostatic precipitation process and apparatus - Google Patents
Wet electrostatic precipitation process and apparatusInfo
- Publication number
- CA1038306A CA1038306A CA206,116A CA206116A CA1038306A CA 1038306 A CA1038306 A CA 1038306A CA 206116 A CA206116 A CA 206116A CA 1038306 A CA1038306 A CA 1038306A
- Authority
- CA
- Canada
- Prior art keywords
- wash liquid
- precipitator
- particles
- spent
- slurry
- 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.)
- Expired
Links
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
- B03C3/02—Plant or installations having external electricity supply
- B03C3/16—Plant or installations having external electricity supply wet type
Abstract
ABSTRACT
An improved wet electrostatic precipitation apparatus and process for the removal of waste particles from effluent gases in which a portion of the wash liquid is recirculated to build up a predetermined solids content, whereby a faster settling rate is achieved and less wash liquid is required.
An improved wet electrostatic precipitation apparatus and process for the removal of waste particles from effluent gases in which a portion of the wash liquid is recirculated to build up a predetermined solids content, whereby a faster settling rate is achieved and less wash liquid is required.
Description
~0383Q6 This invention relates to a wet electrostatic precipitation pro-cess for the removal of waste products from effluent gases and to a wet elec-trostatic precipitator for performing the process of this invention.
It is well known that fine particles which can be electrically charged can be collected in electrostatic precipitators. There are two types of electrostatic precipitators that are commonly used ~ a) dry electrostatic precipitator - for which the mode of operation is to electrically charge the particles which then collect on a grounded plate.
The particles collected on the grounded plate are removed by a rapping mech-anism which dislodges the particles from the plate;
(b) wet electrostatic precipitator - this type of precipitator operates on the same electrostatic principle but the dust particles collected on the grounded plate are removed from the plate by a film of wash liquid which passes over the grounded plate.
The advantage of using a wet electrostatic precipitator over a dry electrostatic precipitator is that for materials with very low electrical resistivity, the particles lose their electrical charge very quickly and if collected in a dry electrostatic precipitator, would fall from the grounded plate and would become re-entrained in the gas stream. On the other hand, in the wet electrostatic precipitator the dust particles are entrapped in the wash liquid on a continual basis.
Known wet electrostatic precipitator units operate with a very high ratio of wash liquid to collected solids (e.g. 0.05% solids). When the collected solids are separated out from the slurry of spent wash liquid and collected solids, by settling and decanting, it has been found that the set-tlement rate is slow.
The present invention enhances the settlement rate of collected solids in the effluent. This is done by recycling some of the slurry back into the precipitator, thus increasing the ratio of collected solids to wash liquid in the slurry from about 0.05% up to 5% or 10%. This higher percen-tage of solids in the wash liquid improves the settling characteristics of the solids in the slurry.
~03B306 An additional advantage obtained by the process and apparatus of this invention is that the collection efficiency of dust particles from the flue gases is increased More particularly, the present invention is a wet electrostatic precipitator having (i) an electrostatic precipitation zone having an electrode and a cor-responding electrically chargeable plate;
tii) a gas inlet means for introducing a waste particle bearing gas into the electrostatic precipitation zone and a gas outlet means for exhausting the cleaned gas from the precipitator;
(iii) means for passing wash liquid over the electrically chargeable plate to remove electrostatic precipitated particles from the plate, ~iv) inlet means for introducing fresh wash liquid into the means for passing wash liquid over the electrostatically chargeable plate, (v) a first reservoir for collecting waste particle bearing spent wash liquid from the precipitation zone, and (vi) circulation means to recycle a portion of the waste particle bear-ing spent wash liquid to the means for passing wash liquid over the electri-cally chargeable plate whereby the wash liquid contains in suspension a predetermined amount of waste particles prior to passing over the electrically chargeable plate.
The invention also includes a process for removing waste particles from effluent gases by means of a wet electrostatic precipitator in which the precipitated waste particles are washed out of the precipitator with a wash liquid. A part of the wash liquid used to wash the precipitated particles out of the precipitator is comprised by recirculating part of the waste par-ticle-bearing, spent wash liquid through the precipitator until the wash liquid contains in suspension a predetermined amount of waste particles prior to passing through the precipitator.
An embodiment of the invention is illustrated in the accompanying drawings in which:
Figure 1 is a schematic drawing and flow sheet of the wet electro--- 2~ --` 1038306 static precipitator according to the invention.
Figure 2 is a detailed drawing in plan of the wash liquid distri-bution unit.
Figure 3 is an elevation of the embodiment illustrated in Figure 2.
Figure 4 is a view along section A-A of Figure 2.
Figure 1 illustrates three collection plates 1 in the form of hollow cylindrical tubes. The collection plates are connected to an electri-cal supply conduit 2 by which they are electrically charged. The effluent gas from which the waste particles are to be removed is introduced at the effluent gas inlet 3 and passes up through collection plates 1, which plates electrostatically attract the waste particles from the effluent gas. The effluent gas from which the waste particles have been removed are discharged by means of exhaust gas fan 5 through the clean gas exhaust 4.
The fresh wash liquid, which in this case is water, enters the precipitator through the fresh water inlet 6. This fresh wash liquid passes down through collection plates 1 picking up the waste particles to form a slurry of water and waste particles and passes into the slurry tank 8. The slurry from the slurry tank 8 can either be passed through the slurry line 9 to a thickener 10 or can be recycled by means of the slurry recycle pump 13 through the slurry recycle line 14 back through the collection plates 1. By recycling the slurry back through the collection plates the concentration of waste particles in the wash liquid is increased.
A slurry tank agitator 7 can be provided in order to agitate the slurry in slurry tank 8 and make the slurry more homogeneous. The waste par-ticles are finally removed from the system when the slurry passes to the thickener 10 which is used to decant the solids from the slurry. The slurry is removed from the system through the thickener underflow discharge 11. Any overflow from the thickener is recycled by the overflow recycle pump 12 through the thickener overflow line 15 back through the collection plates 1.
Figures 2, 3 and 4 illustrate slurry spray nozzles 20 located on the slurry distributor header 19 which is connected to the slurry recycle line 14. Fresh makeup water passing through the fresh water inlet 6 is ~03B306 introduced into the wash liquid through nozzles 21.
A reservoir 30 is provided to retain the slurry before it passes through the collection plates 1. Also provided but not shown in Figures 2, 3 and 4 are frusto-conical weirs which are positioned within the reservoir 30 and communicate with the top of the collection plates 1.
A shroud 17 is provided so that slurry passing from the slurry spray nozzles 20 is directed in a manner conducive to keeping the circulating velocity of the slurry in the reservoir 30 sufficiently high to eliminate the solids in the slurry from settling out in certain "dead" areas of the reser-voir, particularly around the weirs. The fresh makeup water nozzles 21 are also positioned so that the fresh makeup water entering the reservoir 30 also enhances the circulating velocity of the slurry in the reservoir 30.
The amount of solids in the slurry passing through collectionplates 1 can be regulated by the regulation of the fresh water entering through fresh water inlet 6 and the regulation of the slurry recycle line 14.
The following example compares removal of waste production case A, where there was no recirculation of slurry, and case B, where there was re-circulation of the slurry.
Case A Case B
Fresh Water Usage*
(U.S. gallons per dry ton of dust recovered) 960** 270**
Solids in Precipitation Discharge (%) ~ 0.5 5.0 Final Solid Density ~%) 24 59 Thi~kener Minimum Area ~ft /ton.24 hours) 4 Efficiency ~%) 97.5 99-5 * Based on thickener underflow % solids being 80% of final solid density.
** Calculated based on no thickener.
From the above it can be seen that recycling the slurry gives the advantages of the use of less fresh water, a smaller minimum thickener area and a greater final density of solids. It is this greater density of final solids which promotes faster settling of the solids in the slurry and conse-s ~038306 quently better separation capabilities.
The test results also show that efficiency of the precipitator is increased from 97.5% to 99.5% when the per cent solids in the discharge from the wet electrostatic precipitator is 5% rather than less than 0.5%.
The probable mechanism for this efficiency improvement is that with higher contained solids the water film flowing over the collection plates is more turbulent thus creating better collection characteristics.
The recirculation slurry is not limited to 5% solids. The higher limit is the % solids in the slurry that is pumpable with each material; or the density that increases the settling characterisitics of the material to a point where the weir in the top of the collection plate cyclindrical tube becomes filled with settled material.
The following Table I sets out wet electrostatic precipitator (WESP) efficiency data for six tests in which the sluTTy was recycled in tests 3, 4 and 5 but not l, 2 and 6 generally, when the carbon content of the dust is high the efficiency is lower. Test No. 3 in Table I shows, however, that even when the carbon content of the dust is as high as 26.6%, by recycle to 5.0%, the efficiency has been increased to 99.91%. Table II
sets out test data setting out thickener area requirements and settling rates for varying concentrations of solids in the recycle solution. From Table II it can be seen, generally, that a better settling rate and a lesser thickener area requirement is obtained withaa high per cent solids in the wash liquid. The additional settling rate of the recycled solution seems to be the result of flocculation of the particles in the distribution shroud and in the collector pipes.
TABLE I
Test 1 2 3 4 5 6 Kiln R.K. R.K. R.K. D.K. R.K. R.K.
Volume of gases acfm 799 644 629 1428 630 515 Temp: Inlet WESP F 730 628 660 298 712 720 Outlet wesP F 256 232 204 174 170 240 Dust Load Concentration Inlet wesP gr/scf 2.29 2.28 3.12 8.51 7.50 7.53 Outlet wesP gr/scf .031 .060 .003 .010 .028 .217 Clean water flow USgpm 14 11 11 Water slurry recycle " 11 9.4 11 Clean water addition " .25 1.0 1.0 Water to swamp " 14 11.0 0.25 1.0 1.0 11 % Solids Slurry 0.02 0.11 5.0 5.5 2.6 0.27 wesP Efficiency 98.56 96.95 99.91 99.88 99.3 96.5 Inlet wesP % C Dust 10.7 26.6 1.31 4.25 4.07 Slurry wesP % C Solids 9.6 10.7 16.2 1.91 6.12 5.03 Inlet Gases Flow %
CO/CO21.3/2 6/1 6/1 0/9.7 6.2/0 Outlet Gases Flow %
CO/CO21/5.52.5/3.72/3.7 Time of Tests hrs 8 13 25 20 25 11 D.K. - Drying Kiln 103~306 TABLE II
% Solids Ultimate Settling Thickene~ Overflow TemperOature in Wash % SolidsRatej Area, t / Clarity, Flow, F
Test Liquid hr/ft ton/24 hrs. ppm A3.87 37 4.6* 6.70 20 138 B0.82 20 43.3 3.6 5 160 C1.09 23 51.2 2.28 10 166 D0.46 24 59.1 4.81 10 172 E0.40 16 43.3 7.50 10 114 F0.40 16 39.4 8.24 10 115 G0.40 14 43.3 5.28 5 106 H0.75 21 49.2 3.48 5 156 I5.64 59 19.7 1.08 25 138 J 0.4 25.0 44.0 2.95 46 144 K 1.0 37.0 32.5 3.99 46 144 L 2.0 40.8 21.2 3.00 25 144 M 3.0 41.9 20.0 2.05 15 144 N 4.0 43.1 15.3 1.97 10 144 0 5.0 43.5 11.8 2.01 10 144 P15.0 50.0 5.2 1.20 46 144 * The settling rates were difficult to determine due to high turbidity of the effluent.
It is well known that fine particles which can be electrically charged can be collected in electrostatic precipitators. There are two types of electrostatic precipitators that are commonly used ~ a) dry electrostatic precipitator - for which the mode of operation is to electrically charge the particles which then collect on a grounded plate.
The particles collected on the grounded plate are removed by a rapping mech-anism which dislodges the particles from the plate;
(b) wet electrostatic precipitator - this type of precipitator operates on the same electrostatic principle but the dust particles collected on the grounded plate are removed from the plate by a film of wash liquid which passes over the grounded plate.
The advantage of using a wet electrostatic precipitator over a dry electrostatic precipitator is that for materials with very low electrical resistivity, the particles lose their electrical charge very quickly and if collected in a dry electrostatic precipitator, would fall from the grounded plate and would become re-entrained in the gas stream. On the other hand, in the wet electrostatic precipitator the dust particles are entrapped in the wash liquid on a continual basis.
Known wet electrostatic precipitator units operate with a very high ratio of wash liquid to collected solids (e.g. 0.05% solids). When the collected solids are separated out from the slurry of spent wash liquid and collected solids, by settling and decanting, it has been found that the set-tlement rate is slow.
The present invention enhances the settlement rate of collected solids in the effluent. This is done by recycling some of the slurry back into the precipitator, thus increasing the ratio of collected solids to wash liquid in the slurry from about 0.05% up to 5% or 10%. This higher percen-tage of solids in the wash liquid improves the settling characteristics of the solids in the slurry.
~03B306 An additional advantage obtained by the process and apparatus of this invention is that the collection efficiency of dust particles from the flue gases is increased More particularly, the present invention is a wet electrostatic precipitator having (i) an electrostatic precipitation zone having an electrode and a cor-responding electrically chargeable plate;
tii) a gas inlet means for introducing a waste particle bearing gas into the electrostatic precipitation zone and a gas outlet means for exhausting the cleaned gas from the precipitator;
(iii) means for passing wash liquid over the electrically chargeable plate to remove electrostatic precipitated particles from the plate, ~iv) inlet means for introducing fresh wash liquid into the means for passing wash liquid over the electrostatically chargeable plate, (v) a first reservoir for collecting waste particle bearing spent wash liquid from the precipitation zone, and (vi) circulation means to recycle a portion of the waste particle bear-ing spent wash liquid to the means for passing wash liquid over the electri-cally chargeable plate whereby the wash liquid contains in suspension a predetermined amount of waste particles prior to passing over the electrically chargeable plate.
The invention also includes a process for removing waste particles from effluent gases by means of a wet electrostatic precipitator in which the precipitated waste particles are washed out of the precipitator with a wash liquid. A part of the wash liquid used to wash the precipitated particles out of the precipitator is comprised by recirculating part of the waste par-ticle-bearing, spent wash liquid through the precipitator until the wash liquid contains in suspension a predetermined amount of waste particles prior to passing through the precipitator.
An embodiment of the invention is illustrated in the accompanying drawings in which:
Figure 1 is a schematic drawing and flow sheet of the wet electro--- 2~ --` 1038306 static precipitator according to the invention.
Figure 2 is a detailed drawing in plan of the wash liquid distri-bution unit.
Figure 3 is an elevation of the embodiment illustrated in Figure 2.
Figure 4 is a view along section A-A of Figure 2.
Figure 1 illustrates three collection plates 1 in the form of hollow cylindrical tubes. The collection plates are connected to an electri-cal supply conduit 2 by which they are electrically charged. The effluent gas from which the waste particles are to be removed is introduced at the effluent gas inlet 3 and passes up through collection plates 1, which plates electrostatically attract the waste particles from the effluent gas. The effluent gas from which the waste particles have been removed are discharged by means of exhaust gas fan 5 through the clean gas exhaust 4.
The fresh wash liquid, which in this case is water, enters the precipitator through the fresh water inlet 6. This fresh wash liquid passes down through collection plates 1 picking up the waste particles to form a slurry of water and waste particles and passes into the slurry tank 8. The slurry from the slurry tank 8 can either be passed through the slurry line 9 to a thickener 10 or can be recycled by means of the slurry recycle pump 13 through the slurry recycle line 14 back through the collection plates 1. By recycling the slurry back through the collection plates the concentration of waste particles in the wash liquid is increased.
A slurry tank agitator 7 can be provided in order to agitate the slurry in slurry tank 8 and make the slurry more homogeneous. The waste par-ticles are finally removed from the system when the slurry passes to the thickener 10 which is used to decant the solids from the slurry. The slurry is removed from the system through the thickener underflow discharge 11. Any overflow from the thickener is recycled by the overflow recycle pump 12 through the thickener overflow line 15 back through the collection plates 1.
Figures 2, 3 and 4 illustrate slurry spray nozzles 20 located on the slurry distributor header 19 which is connected to the slurry recycle line 14. Fresh makeup water passing through the fresh water inlet 6 is ~03B306 introduced into the wash liquid through nozzles 21.
A reservoir 30 is provided to retain the slurry before it passes through the collection plates 1. Also provided but not shown in Figures 2, 3 and 4 are frusto-conical weirs which are positioned within the reservoir 30 and communicate with the top of the collection plates 1.
A shroud 17 is provided so that slurry passing from the slurry spray nozzles 20 is directed in a manner conducive to keeping the circulating velocity of the slurry in the reservoir 30 sufficiently high to eliminate the solids in the slurry from settling out in certain "dead" areas of the reser-voir, particularly around the weirs. The fresh makeup water nozzles 21 are also positioned so that the fresh makeup water entering the reservoir 30 also enhances the circulating velocity of the slurry in the reservoir 30.
The amount of solids in the slurry passing through collectionplates 1 can be regulated by the regulation of the fresh water entering through fresh water inlet 6 and the regulation of the slurry recycle line 14.
The following example compares removal of waste production case A, where there was no recirculation of slurry, and case B, where there was re-circulation of the slurry.
Case A Case B
Fresh Water Usage*
(U.S. gallons per dry ton of dust recovered) 960** 270**
Solids in Precipitation Discharge (%) ~ 0.5 5.0 Final Solid Density ~%) 24 59 Thi~kener Minimum Area ~ft /ton.24 hours) 4 Efficiency ~%) 97.5 99-5 * Based on thickener underflow % solids being 80% of final solid density.
** Calculated based on no thickener.
From the above it can be seen that recycling the slurry gives the advantages of the use of less fresh water, a smaller minimum thickener area and a greater final density of solids. It is this greater density of final solids which promotes faster settling of the solids in the slurry and conse-s ~038306 quently better separation capabilities.
The test results also show that efficiency of the precipitator is increased from 97.5% to 99.5% when the per cent solids in the discharge from the wet electrostatic precipitator is 5% rather than less than 0.5%.
The probable mechanism for this efficiency improvement is that with higher contained solids the water film flowing over the collection plates is more turbulent thus creating better collection characteristics.
The recirculation slurry is not limited to 5% solids. The higher limit is the % solids in the slurry that is pumpable with each material; or the density that increases the settling characterisitics of the material to a point where the weir in the top of the collection plate cyclindrical tube becomes filled with settled material.
The following Table I sets out wet electrostatic precipitator (WESP) efficiency data for six tests in which the sluTTy was recycled in tests 3, 4 and 5 but not l, 2 and 6 generally, when the carbon content of the dust is high the efficiency is lower. Test No. 3 in Table I shows, however, that even when the carbon content of the dust is as high as 26.6%, by recycle to 5.0%, the efficiency has been increased to 99.91%. Table II
sets out test data setting out thickener area requirements and settling rates for varying concentrations of solids in the recycle solution. From Table II it can be seen, generally, that a better settling rate and a lesser thickener area requirement is obtained withaa high per cent solids in the wash liquid. The additional settling rate of the recycled solution seems to be the result of flocculation of the particles in the distribution shroud and in the collector pipes.
TABLE I
Test 1 2 3 4 5 6 Kiln R.K. R.K. R.K. D.K. R.K. R.K.
Volume of gases acfm 799 644 629 1428 630 515 Temp: Inlet WESP F 730 628 660 298 712 720 Outlet wesP F 256 232 204 174 170 240 Dust Load Concentration Inlet wesP gr/scf 2.29 2.28 3.12 8.51 7.50 7.53 Outlet wesP gr/scf .031 .060 .003 .010 .028 .217 Clean water flow USgpm 14 11 11 Water slurry recycle " 11 9.4 11 Clean water addition " .25 1.0 1.0 Water to swamp " 14 11.0 0.25 1.0 1.0 11 % Solids Slurry 0.02 0.11 5.0 5.5 2.6 0.27 wesP Efficiency 98.56 96.95 99.91 99.88 99.3 96.5 Inlet wesP % C Dust 10.7 26.6 1.31 4.25 4.07 Slurry wesP % C Solids 9.6 10.7 16.2 1.91 6.12 5.03 Inlet Gases Flow %
CO/CO21.3/2 6/1 6/1 0/9.7 6.2/0 Outlet Gases Flow %
CO/CO21/5.52.5/3.72/3.7 Time of Tests hrs 8 13 25 20 25 11 D.K. - Drying Kiln 103~306 TABLE II
% Solids Ultimate Settling Thickene~ Overflow TemperOature in Wash % SolidsRatej Area, t / Clarity, Flow, F
Test Liquid hr/ft ton/24 hrs. ppm A3.87 37 4.6* 6.70 20 138 B0.82 20 43.3 3.6 5 160 C1.09 23 51.2 2.28 10 166 D0.46 24 59.1 4.81 10 172 E0.40 16 43.3 7.50 10 114 F0.40 16 39.4 8.24 10 115 G0.40 14 43.3 5.28 5 106 H0.75 21 49.2 3.48 5 156 I5.64 59 19.7 1.08 25 138 J 0.4 25.0 44.0 2.95 46 144 K 1.0 37.0 32.5 3.99 46 144 L 2.0 40.8 21.2 3.00 25 144 M 3.0 41.9 20.0 2.05 15 144 N 4.0 43.1 15.3 1.97 10 144 0 5.0 43.5 11.8 2.01 10 144 P15.0 50.0 5.2 1.20 46 144 * The settling rates were difficult to determine due to high turbidity of the effluent.
Claims (10)
1. In the operation of a wet electrostatic precipitation process for the removal of solid waste particles containing up to about 26.6%
carbon from effluent gases wherein the precipitated particles are washed out of the precipitator with a wash liquid to prevent their recapture by the effluent gases, said wash liquid forming a spent wash liquid slurry with the precipitated waste particles, and the particles are subsequently separated from the spent wash liquid by conventional settling techniques comprising a thickener, the improvement which comprises recirculating part of the spent wash liquid slurry through the precipitator until the wash liquid in the precipitator contains in suspension a predetermined amount of waste particles prior to passing out from the precipitator for separation of the waste particles from the spent wash liquid slurry in said thickener.
carbon from effluent gases wherein the precipitated particles are washed out of the precipitator with a wash liquid to prevent their recapture by the effluent gases, said wash liquid forming a spent wash liquid slurry with the precipitated waste particles, and the particles are subsequently separated from the spent wash liquid by conventional settling techniques comprising a thickener, the improvement which comprises recirculating part of the spent wash liquid slurry through the precipitator until the wash liquid in the precipitator contains in suspension a predetermined amount of waste particles prior to passing out from the precipitator for separation of the waste particles from the spent wash liquid slurry in said thickener.
2. The invention defined in claim 1, wherein the recirculation is conducted until the concentration of solids in the wash liquid prior to passing through the precipitator is at least about 5% by weight of solids.
3. The invention defined in claim 2 wherein the recirculation is stopped at a maximum concentration of waste particles in the wash liquid of about 10% by weight of solids.
4. The invention defined in claim 1 or 2, wherein the recirculation is continued until the solids concentration of the spent wash liquid is such that it is about to adversely affect its precipitability.
5. In a wet electrostatic precipitator system for removing waste particles from an effluent gas, said system comprising a wet electrostatic precipitator and a thickener, wherein said wet electrostatic separator removes solid waste particles containing up to about 26.6% carbon from effluent gases, said waste particles being washed out of the precipitator with a wash liquid, thereby forming a spent wash liquid slurry, and said waste particles being subsequently removed from the spent wash liquid slurry in the thickener, and wherein the electrostatic precipitator comprises:
An electrostatic precipitation zone comprising at least one electrode and a corresponding electrically chargeable collection plate, gas inlet means for introducing a waste particle bearing gas into said zone and gas outlet means for exhausting the cleaned gas therefrom, means for passing wash liquid over said plate to remove electro-statically precipitated particles therefrom, fresh wash liquid inlet means for introducing fresh wash liquid into said means for passing wash liquid over said plate, means for exhausting at least a portion of the spent wash liquid containing precipitated particles from the precipitator to the thickener, and the improvement which comprises a first reservoir for collect-ing waste particle bearing spent wash liquid from said precipitation zone and circulation means for recycling a portion of said spent waste particle bearing spent wash liquid directly to said means for passing wash liquid over said plate, whereby at least a portion of said wash liquid can be maintained in the precipitator to collect in suspension a predetermined amount of waste particles prior to passage out from the precipitator to the thickener.
An electrostatic precipitation zone comprising at least one electrode and a corresponding electrically chargeable collection plate, gas inlet means for introducing a waste particle bearing gas into said zone and gas outlet means for exhausting the cleaned gas therefrom, means for passing wash liquid over said plate to remove electro-statically precipitated particles therefrom, fresh wash liquid inlet means for introducing fresh wash liquid into said means for passing wash liquid over said plate, means for exhausting at least a portion of the spent wash liquid containing precipitated particles from the precipitator to the thickener, and the improvement which comprises a first reservoir for collect-ing waste particle bearing spent wash liquid from said precipitation zone and circulation means for recycling a portion of said spent waste particle bearing spent wash liquid directly to said means for passing wash liquid over said plate, whereby at least a portion of said wash liquid can be maintained in the precipitator to collect in suspension a predetermined amount of waste particles prior to passage out from the precipitator to the thickener.
6. An electrostatic precipitator as claimed in claim 5 wherein said collection plate is comprised of at least one vertically aligned hol-low cylindrical tube open at both ends and said means for passing wash liquid over said plate to remove electrostatically precipitated particles comprises a second reservoir, a weir distributing means positioned in said second reservoir having at least one weir communicating with the top end of each cylindrical tube to distribute the wash liquid over the inner walls of said cylindrical tube and an agitating means for agitating said wash liquid in said second reservoir to retain said waste particles in suspension.
7. An electrostatic precipitator as claimed in claim 6 wherein said agitating means comprises shrouding means positioned to direct the flow of the spent wash liquid flowing from said circulation means into the second reservoir to agitate the wash liquid in the second reservoir so as to prevent waste particles from sanding out in areas of said weir distributing means.
8. An electrostatic precipitator as claimed in claim 7 wherein said fresh wash liquid inlet means comprising a plurality of inlets arranged to direct fresh wash liquid into said second reservoir to further agitate the wash liquid in said second reservoir.
9. The invention as defined in claim 5 wherein the wash liquid is an aqueous medium.
10. The invention as defined in claim 1 wherein the wash liquid is an aqueous medium.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA206,116A CA1038306A (en) | 1974-08-01 | 1974-08-01 | Wet electrostatic precipitation process and apparatus |
| BR7504292A BR7503358A (en) | 1974-08-01 | 1975-05-28 | PROCESS FOR WET ELECTROSTATIC PRECIPITATION AND WET ELECTROSTATIC PRECIPITATOR |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA206,116A CA1038306A (en) | 1974-08-01 | 1974-08-01 | Wet electrostatic precipitation process and apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1038306A true CA1038306A (en) | 1978-09-12 |
Family
ID=4100815
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA206,116A Expired CA1038306A (en) | 1974-08-01 | 1974-08-01 | Wet electrostatic precipitation process and apparatus |
Country Status (2)
| Country | Link |
|---|---|
| BR (1) | BR7503358A (en) |
| CA (1) | CA1038306A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4441897A (en) * | 1981-09-30 | 1984-04-10 | Inco Limited | Wet electrostatic precipitator having removable nested hexagonal collector plates and magnetic aligning and rapping means |
-
1974
- 1974-08-01 CA CA206,116A patent/CA1038306A/en not_active Expired
-
1975
- 1975-05-28 BR BR7504292A patent/BR7503358A/en unknown
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4441897A (en) * | 1981-09-30 | 1984-04-10 | Inco Limited | Wet electrostatic precipitator having removable nested hexagonal collector plates and magnetic aligning and rapping means |
Also Published As
| Publication number | Publication date |
|---|---|
| BR7503358A (en) | 1976-08-03 |
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