EP0044361A1 - Précipitateur électrostatique comprenant une structure d'électrode de décharge - Google Patents

Précipitateur électrostatique comprenant une structure d'électrode de décharge Download PDF

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Publication number
EP0044361A1
EP0044361A1 EP80302450A EP80302450A EP0044361A1 EP 0044361 A1 EP0044361 A1 EP 0044361A1 EP 80302450 A EP80302450 A EP 80302450A EP 80302450 A EP80302450 A EP 80302450A EP 0044361 A1 EP0044361 A1 EP 0044361A1
Authority
EP
European Patent Office
Prior art keywords
precipitator
tube
column
wires
discharge electrode
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.)
Withdrawn
Application number
EP80302450A
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German (de)
English (en)
Inventor
Thomas J. Michel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Santek Inc
Original Assignee
Santek Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Santek Inc filed Critical Santek Inc
Priority to EP80302450A priority Critical patent/EP0044361A1/fr
Publication of EP0044361A1 publication Critical patent/EP0044361A1/fr
Withdrawn legal-status Critical Current

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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
    • B03C3/34—Constructional details or accessories or operation thereof
    • B03C3/40—Electrode constructions
    • B03C3/60—Use of special materials other than liquids
    • B03C3/64—Use of special materials other than liquids synthetic resins
    • 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
    • B03C3/41—Ionising-electrodes
    • 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
    • B03C2201/00—Details of magnetic or electrostatic separation
    • B03C2201/10—Ionising electrode with two or more serrated ends or sides

Definitions

  • This invention relates generally to discharge electrodes for electrostatic precipitators, and more particularly to a discharge electrode structure disposed within a tubular collector electrode and adapted to maintain a uniform high-intensity electrostatic field within the tubular electrode.
  • Electrostatic precipitators function to separate contaminating particles of droplets of a semi-solid or solid nature for a gaseous stream. Such precipitators are especially helpful in removing finer particles (less than 40 pm).
  • the gases to be purified such as those issuing from an incinerator, are conveyed through a collector tube where they are subjected to an electrostatic field which causes the particles to migrate toward the inner wall of the collector tube, thereby separating the particles from the gas flowing through the tube.
  • the particles accumulate on the wall of the collector tube and it becomes necessary, therefore, at fairly frequent intervals, to shut down the precipitator in order to permit removal of the agglomerated particles.
  • a uniform film of downwardly flowing water. is formed on the inner wall of the collector tube, the film serving to continuously wash away the contaminants, thereby obviating the need to interrupt the precipitator operation.
  • the present invention is applicable to a dry or wet type of electrostatic precipitator in which the discharge electrode structure is coaxially supported within a tubular electrode.
  • unipolar ions are produced by a discharge electrode, the ions migrating across the gap between this electrode and the tubular collector under the influence of an electric field established therebetween. In so migrating. the ions attach themselves to the aerosol particles moving with the gas passing between the electrodes, the charged particles being attracted to the collector.
  • the discharge electrode is a wire coaxially supported within a tubular collector electrode.
  • This wire has a much smaller radius of curvature than the tubular collector, the air gap or inter-electrode space between these electrodes being very large compared to the radius of the wire.
  • the electric field varies inversely with the radius of the wire.
  • the level of voltage needed to produce a corona discharge is below that necessary to completely break down the dielectric of air to produce a spark discharge across the gap. Since an understanding of this distinction is vital to the invention, the behavior of corona and spark discharges will be further analyzed.
  • a corona discharge is a highly active glow region surrounding a discharge electrode.
  • this electrode is constituted by a wire, the glow region extending a short distance beyond the wire.
  • the free electrons in the gas in the region of the intense electric field surrounding the wire gain energy from this field to produce positive ions and other electrons by collision. In turn, these new electrons are accelerated and produce further ionization.
  • the electrons emitted from the negatively-charged wire or discharge electrode are drawn toward the positively- charged collector electrode. As these electrons advance into the weaker field away from the wire, they tend to form negative ions by attaching themselves to neutral xoygen molecules. These negative ions create a dense unipolar cloud that occupies most of the gap between the electrodes and constitutes the only current in the entire space outside the corona glow region. This space charge functions to regard the further emission of negative charge from the corona region and in this way restricts the ionizing field adjacent the wire, thereby stabilizing the discharge.
  • the air dielectric When, however, the voltage applied to the ionizing electrode is furthe: elevated to a level exceeding the point at which a co::ona discharge is maintained in a stable condition, the air dielectric then'completely breaks down as a result of which the air in the gap is rendered relativelv conductive to sustain a spark discharge which is accompanies by a heavy current flow.
  • An electrostatic precipitator attains its highest operating efficiency under optimum ionization conditions when the voltage applied to the discharge electrodes approaches the point of transition between an incomplete breakdown or corona discharge producing a copious supply . of ions and complete air dielectric breakdown or spark discharge which effectively short circuits the precipitator and renders it inoperative.
  • the voltage gradient about this wire to the surface of the tube is uniform over a 360 polar angle from the center of the wire normal to its axis.
  • a collector tube having an 8-inch diameter
  • a discharge wire having an 8-mil diameter and an excitation voltage of 30 kilovolts applied between the wire and the collector tube.
  • the resultant voltage gradient between the wire and the collector tube is then approximately 7500 volts per inch. Because the discharge wire is of small diameter and is at a high voltage, it will readily ionize small particles suspended in a contaminated gas passing through the tube. As a result, the ionized particles will migrate toward the wall of the collector tube, the migration being induced by the intense voltage gradient.
  • the obvious step is to increase the voltage from 30 KV to 60 KV and thereby establish the same voltage gradient.
  • the drawback to this obvious approach is not only that it entails a far more costly power supply, but now that one has doubled the voltage to maintain the same voltage gradient, the likelihood of an air breakdown that would short circuit the precipitator is greatly augmented.
  • the main object of this invention is to provide a discharge electrode structure for use in conjunction with a tubular electrode of large diameter to produce an intense voltage gradient that is substantially uniform over a 360° polar angle, thereby ionizing virtually all contaminants in the gaseous stream passing through the tube.
  • an object of this invention is to provide an improved discharge electrode structure of the above type which includes a circular array of wires which are electrostatically isolated from each other.
  • a significant advantage of a discharge electrode structure in accordance with the invention is that it makes possible a large capacity electrostatic precipitator of the wet or dry type wherein the voltage gradient is substantially uniform to effect ionization of the particles passing through the annular region between the array of discharge wires and the inner wall of the collector tube.
  • a discharge electrode structure which includes a column of dielectric material whose central axis is coincident with the axis of the collector tube within which the structure is disposed.
  • the column has a cross-sectional geometry, preferably star-shaped, that defines a circular series of longitudinally extending niches. Supported between the ends of the column is a circular array of fine gauge wires, each of which is suspended within a respective niche so that the wires are electrostatically isolated from each other.
  • a high voltage is impressed between the array of wires and the inner surface of the collector tube, which is preferably grounded, to create an electrostatic field in the annular region between the discharge electrode structure and the tube to ionize the contaminants in the gaseous stream passing therethrough and to cause the ionized contaminants to migrate toward the collector tube.
  • the surface of the niches acquire bound electrostatic charges whereby the voltage gradient between the discharge electrode structure of the tube is rendered substantially uniform.
  • a conventional electrostatic precipitator having a collector tube 10, within which is coaxially disposed a fine discharge electrode wire 11. A high voltage is impressed between the wire and the tube.
  • collector tube 10 has an inner diameter of 8 inches; hence the radial distance between the wire and the surface of the tube is about 4 inches.
  • the voltage gradient is represented in Fig. 1 by concentric circles and the electric lines of force by dashed radial lines.
  • the voltage gradient in this arrangement is uniform, about a 360 polar angle from the center of the wire.
  • One prior art approach to enlarging the capacity of the electrostatic precipitator is to provide, as shown in Fig. 2, in conjunction with a collector tube 12 of, say, 16 inches in diameter, a circular array 13 of fine discharge electrode wires.
  • the distance between the circle of discharge electrode wires and the inner wall of the collector tube is 4 inches; hence it is the same as the distance between the single discharge wire 11 and the wall of the 8-inch collector tube 10 in Fig. 1. Consequently, no greater operating voltage is required in the scaled-up Fig. 2 arrangement than in the smaller Fig. 1 arrangement.
  • the central region encircled by the array of wires has a zero voltage gradient, and particulate contaminants in the gaseous stream passing through this region will not be ionized.
  • the wires in the array are in close proximity to each other, they interact electrostatically and the voltage gradient resembles a clover leaf pattern with a lobe about each wire. This gives rise to a voltage gradient between the wire array and the collector tube which is distinctly non-uniform. Hence the contaminated gas passing in the annular region between the tube and the array of wires will not be properly ionized and the precipitator will operate inefficiently.
  • a preferred embodiment of an electrostatic precipitator in accordance with the invention the precipitator being constituted by a collector tube 14 within which is disposed a discharge electrode structure, generally disignated by numeral 15.
  • Discharge electrode structure 15 includes a central column 16 whose center axis is coincident with the axis X of the collector tube, the length of the column being about equal to that of the tube.
  • Column 16 is extruded or otherwise fabricated of a synthetic plastic material having good structural and dielectric properties which is capable of taking on an extremely high bound surface charge. Suitable for this purpose is acrylic, polycarbonate, polystyrene or plastics having similar properties.
  • the cross sectional geometry of the column is such as to define a circular series of longitudinally-extending niches.
  • the geometry is that of a five-pointed star which defines five triangular alcoves or niches N 1 , N 2 , N 3 , N4 and N 5 .
  • the invention is not limited to this configuration and the niches may be in either geometric forms such as arcuate alcoves.
  • the discharge electrode structure further includes a circular array of wires 17 whose diameter is preferably less than ten mils which extend between insulating discs 18 and 19 secured to opposite ends of the column, each wire being suspended within a respective niche.
  • the end discs may be spring-biased, as shown in block form in Figure 3 to hold the wires under tension.
  • the wires in the array are interconnected, a high voltage from a power supply 20 being applied to the wires.
  • the other end of the power supply as well as collector tube 14 is grounded so that an intense electric field is established between the wires and the collector tube.
  • collector tube 14 must be conductive to form a collector electrode; but where the precipitator is wet, the tube need not be electrically conductive--for the water film which flows down the inner surface of the tube is grounded to operate as the collector electrode.
  • a contaminated gas is admitted to the lower end of collector tube 14, preferably through a Venturi inlet 21, this serving to cause the gas entering the collector to expand against the wet wall thereof to prevent the water film from being peeled off by the upward rush of incoming gas.
  • a Venturi inlet is not necessary, however, with a dry precipitator.
  • the gas may be admitted to the upper end of the wet precipitator and flow downwardly therein, no Venturi being used at the inlet.
  • Each niche-disposed wire 17 in the array disposed is the same radial distance from the center axis of the column and is parallel thereto.
  • the resultant electrostatic field establishes a bound surface charge on the niches. This results in a uniform voltage gradient between the ionizing wire and the circular ground plane, this being due to the uniform distribution of the electrostatic field on the wall of the niches.
  • the bound surface charge on the plastic column is satisfied, the field tends to reflect precisely the same electrostatic voltage field applied to it by the ionizing wire.
  • the voltage gradient from any center point of any ionizing wire or from any edge of any arm of the star-configurated column to the concentric ground plane of the collector tube can be made very close-to an equal value.
  • the dielectric column which takes a hiqh bound surface charge is that the potential difference across its entire surface is essentially zero. Therefore, the column is not susceptible to picking up contaminants that would cause grounding or arcing of the ionizing wires because of their close proximity to the column.
  • the plastic column may be supported by a grounded element or fixture, its high surface and volume resistivity will prevent it from leaking a significant amount of charge from the ionizing wires.
  • the diameter of the collector tube was given as 16 inches, as compared to the prior art single wire arrangement involving a collector tube of 8-inch diameter.
  • the enclosed area in an 8-inch diameter tube is equal to 50.27 square inches, and the internal surface area is 25.13 square inches per linear inch to ground potential surface.
  • the area enclosed is 201.06 square inches, with an internal surface area of 50.27 square inches per linear inch. It is evident, therefore, that when using an unobstructed 16-inch diameter collector tube, the air flow is quadrupled at the same static pressure drop.
  • the column in the present arrangement is an obstruction in the 16-inch diameter collector tube. If we assume that the column occupies the central 8-inch diameter region within the tube in order to maintain a uniform voltage gradient and to provide good ionization, the resultant loss in total air flow is 25%. However, this represents three times more air flow with the same electrostatic characteristics obtained with a single wire in an 8-inch collector tube.

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  • Electrostatic Separation (AREA)
EP80302450A 1980-07-18 1980-07-18 Précipitateur électrostatique comprenant une structure d'électrode de décharge Withdrawn EP0044361A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP80302450A EP0044361A1 (fr) 1980-07-18 1980-07-18 Précipitateur électrostatique comprenant une structure d'électrode de décharge

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP80302450A EP0044361A1 (fr) 1980-07-18 1980-07-18 Précipitateur électrostatique comprenant une structure d'électrode de décharge

Publications (1)

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EP0044361A1 true EP0044361A1 (fr) 1982-01-27

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000030755A2 (fr) * 1998-11-25 2000-06-02 Msp Corporation Dispositif de precipitation electrostatique compact a efficacite elevee pour collecte de gouttelettes d'aerosol
US6902604B2 (en) 2003-05-15 2005-06-07 Fleetguard, Inc. Electrostatic precipitator with internal power supply
US7082897B2 (en) 2004-04-08 2006-08-01 Fleetguard, Inc. Electrostatic precipitator with pulsed high voltage power supply
US7112236B2 (en) 2004-04-08 2006-09-26 Fleetguard, Inc. Multistage space-efficient electrostatic collector
US7267711B2 (en) 2003-09-23 2007-09-11 Msp Corporation Electrostatic precipitator for diesel blow-by
US7455055B2 (en) 2004-04-08 2008-11-25 Fleetguard, Inc. Method of operation of, and protector for, high voltage power supply for electrostatic precipitator
EP2036615A3 (fr) * 2007-09-13 2010-02-17 Peter Buchta Electrofiltre pour une installation d'allumage
EP3492174A1 (fr) * 2017-12-04 2019-06-05 PHX Innovation ApS Système précipitateur électrostatique comportant une électrode de décharge à fil en suspension
DE102019128292A1 (de) * 2019-09-11 2021-03-11 GEFERTEC GmbH Reinigungsvorrichtung zum elektrostatischen Reinigen von Gas und Verwendungen derselben
USD1028199S1 (en) 2018-06-13 2024-05-21 Exodraft a/s Smoke extractor

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR537980A (fr) * 1922-06-01

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR537980A (fr) * 1922-06-01

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000030755A2 (fr) * 1998-11-25 2000-06-02 Msp Corporation Dispositif de precipitation electrostatique compact a efficacite elevee pour collecte de gouttelettes d'aerosol
WO2000030755A3 (fr) * 1998-11-25 2000-11-16 Msp Corp Dispositif de precipitation electrostatique compact a efficacite elevee pour collecte de gouttelettes d'aerosol
US6221136B1 (en) 1998-11-25 2001-04-24 Msp Corporation Compact electrostatic precipitator for droplet aerosol collection
US6364941B2 (en) 1998-11-25 2002-04-02 Msp Corporation Compact high efficiency electrostatic precipitator for droplet aerosol collection
US6527821B2 (en) 1998-11-25 2003-03-04 Msp Corporation Automatic condensed oil remover
US6902604B2 (en) 2003-05-15 2005-06-07 Fleetguard, Inc. Electrostatic precipitator with internal power supply
DE102004022288B4 (de) * 2003-05-15 2009-09-10 Fleetguard, Inc., Nashville Elektrostatischer Abscheider mit internem Netzgerät
US7267711B2 (en) 2003-09-23 2007-09-11 Msp Corporation Electrostatic precipitator for diesel blow-by
US7264658B1 (en) 2004-04-08 2007-09-04 Fleetguard, Inc. Electrostatic precipitator eliminating contamination of ground electrode
US7112236B2 (en) 2004-04-08 2006-09-26 Fleetguard, Inc. Multistage space-efficient electrostatic collector
US7455055B2 (en) 2004-04-08 2008-11-25 Fleetguard, Inc. Method of operation of, and protector for, high voltage power supply for electrostatic precipitator
US7082897B2 (en) 2004-04-08 2006-08-01 Fleetguard, Inc. Electrostatic precipitator with pulsed high voltage power supply
EP2036615A3 (fr) * 2007-09-13 2010-02-17 Peter Buchta Electrofiltre pour une installation d'allumage
EP3492174A1 (fr) * 2017-12-04 2019-06-05 PHX Innovation ApS Système précipitateur électrostatique comportant une électrode de décharge à fil en suspension
USD1028199S1 (en) 2018-06-13 2024-05-21 Exodraft a/s Smoke extractor
DE102019128292A1 (de) * 2019-09-11 2021-03-11 GEFERTEC GmbH Reinigungsvorrichtung zum elektrostatischen Reinigen von Gas und Verwendungen derselben
DE102019128292B4 (de) * 2019-09-11 2021-07-01 GEFERTEC GmbH Reinigungsvorrichtung zum elektrostatischen Reinigen von Gas und Verwendungen derselben

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Inventor name: MICHEL, THOMAS J.