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WO1997043044A1 - Depoussiereur electrostatique - Google Patents

Depoussiereur electrostatique Download PDF

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Publication number
WO1997043044A1
WO1997043044A1 PCT/AU1997/000298 AU9700298W WO9743044A1 WO 1997043044 A1 WO1997043044 A1 WO 1997043044A1 AU 9700298 W AU9700298 W AU 9700298W WO 9743044 A1 WO9743044 A1 WO 9743044A1
Authority
WO
WIPO (PCT)
Prior art keywords
corona
particles
accordance
corona wind
electrostatic precipitator
Prior art date
Application number
PCT/AU1997/000298
Other languages
English (en)
Inventor
John LOWKE
Richard Morrow
Original Assignee
Commonwealth Scientific And Industrial Research Organisation
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 Commonwealth Scientific And Industrial Research Organisation filed Critical Commonwealth Scientific And Industrial Research Organisation
Priority to AU26864/97A priority Critical patent/AU2686497A/en
Publication of WO1997043044A1 publication Critical patent/WO1997043044A1/fr

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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
    • B03C3/34—Constructional details or accessories or operation thereof
    • B03C3/36—Controlling flow of gases or vapour
    • 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
    • B03C2201/14—Details of magnetic or electrostatic separation the gas being moved electro-kinetically

Definitions

  • the present invention relates to electrostatic precipitators, and, particularly, but not exclusively, to electrostatic precipitator of the type which may be used to remove dust particles from flue gas.
  • the present invention provides an electrostatic precipitator, comprising means for creating an electric field to apply an electric charge to particles in a gas, and collection means for collecting the particles, the precipitator being physically and/or electrically adapted to utilise a corona wind, created by interaction between the electric field and particles in the gas, to assist in collection of the particles.
  • the arrangement of the precipitator is such as to take into account the vector result of the corona wind flow and a gas stream flow such that the resultant wind flow assists m directing the dust particles towards the collection means.
  • the gas stream flow may be the applied gas flow m a flue gas such as flue gas in an electrical power generating station.
  • the means for creating an electric field preferably includes a plurality of conductors, each of the conductors configured to produce a corona and arranged physically with respect to each other such that a corona wind produced by the interaction of the corona and gas particles assists in facilitating collection of the - - particles by the collection means.
  • the conductors are preferably elongate wires shaped to produce a corona (i.e., they may be circular in cross section) .
  • the arrangement is preferably such that the gas flow created by the corona wind and any applied gas flow directs particles over the collection means in order to facilitate collection.
  • the electric field is produced by groups of a plurality of parallel extending wires extending on either side of a louvred collector plate.
  • adjacent groups of wires are staggered with respect to each other so that the electric field creates a corona wind which will be directed through the collector plate towards the opposite group of electrodes.
  • the louvred collector plate comprising a plurality of angled louvres spaced with respect to each other, allows gas flow through the collector plate.
  • areas of relative lack of flow of gas, or "relatively still regions” are formed m the precipitator and precipitation of particles on the collection means in these relatively still areas is facilitated.
  • further conductors are provided and mounted within or proximate the relatively still areas, the further conductors being arranged to produce an electric field to assist m precipitation but not to produce a corona, so as to avoid or minimise the production of any corona wind within the relatively still areas, or any corona wind which interferes with the corona wind produced by the first conductors.
  • the collection means includes a plurality of groups of collection members and there are provided a plurality of groups of conductors, - - the respective groups of collection members and conductors being interleaved so that each group of collection members has a plurality of conductors on either side of it and vice versa.
  • the collection members are preferably in the form of plates having a curved or arcuate profile and the conductors are arranged such that the vector result of the applied gas flow and the corona wind directs gas over the outer, or larger, curved surface of each of the collector plates.
  • Adjacent plates preferably curve m opposite directions to each other to facilitate flow over the outside of the plates. At least some pairs of plates m adjacent groups oppose each other and are curved towards each other.
  • a "stagnant space" of relatively still gas is created.
  • this stagnant space actually facilitates precipitation, as the gas particles remain within the space and are subject to an applied charge, for a relatively long period of time.
  • Further conductors are preferably mounted within this stagnant space, the further conductors being arranged not to produce a corona or at least produce minimal corona, but are charged, so as to produce regions of no corona but high electric field facilitate precipitation without producing a corona wind
  • the present invention further provides a method of precipitating particles from a gas flow, comprising the steps of applying an electric field to the gas to create a corona wind which assists m moving particles towards a collection means for precipitation and collection.
  • the present invention yet further provides a method of constructing an electrostatic precipitator for removing dust particles from a gas, the precipitator comprising means for creating an electric field to apply an electric charge to particles m the gas, and collection means for collecting the particles, the method comprising the steps of physically and/or electrically adapting the means for creating the electric field and the collection means to utilise a corona wind, created by interaction between the electric field and particles in the gas, to assist m collection of the particles.
  • the present invention yet further provides a method of constructing an arrangement for removing dust particles from a gas by precipitation on a collection means, comprising the step of arranging electrodes on either side of the collection means to take into account the effect of a corona wind created by an electric field produced by the electrodes when charged, whereby the corona wind will assist in the precipitation of the gas particles onto the collection member.
  • the present invention yet further provides an electrostatic precipitator, comprising first and second groups of corona creating conductors arranged, respectively, on opposite sides of a collection means comprising a plurality of collection members separated by gaps to enable gas flow, the first group of corona creating conductors being staggered with respect to the second group of corona creating conductors.
  • corona wind has been harnessed to assist particle precipitation.
  • regions of no or relatively little corona wind are produced to further facilitate precipitation, by including conductors which produce little or no corona but high electric field in the - - relatively still areas.
  • the corona wind can interfere with collection of particles.
  • the present invention provides an electrostatic precipitator, comprising means for creating an electric field to apply an electric charge to particles m a gas, and collection means for collecting the particles, the means for creating an electric field being adapted to minimise the production of corona wind so that at least regions of little or no corona wind are created m the precipitator to facilitate precipitation on the collection means.
  • the electrical conductors may be substantially flat plates with curved edges, to minimise the production of corona.
  • the collection means comprises opposing collector members mounted either side of a conductor, and an electric field is applied to the conductor to enhance precipitation.
  • the electrostatic precipitator also utilises a corona wind, so that there are regions where corona wind flow is utilised to enhance precipitation, and relatively still regions of little or no corona wind where gas movement is relatively small and which also result m increased precipitation, as discussed above m relation to the preferred embodiment of the first aspect of the invention.
  • the present invention provides a method of precipitating particles from a gas flow, comprising the steps of applying an electric field to the gas and creating at least regions of relatively still gas where little or minimal corona wind is produce ⁇ , - - to assist in precipitating particles on a collection means for collection.
  • the method may also include the step of applying an electric field to other regions such that a corona wind is produced m those other regions and that this corona wind also assists in the precipitation of the particles on the collections means.
  • Figure 1 is a schematic diagram illustrating the application of an electrostatic precipitator in cleaning flue gasses m a electrical power generating station
  • Figure 2 is a schematic cross-sectional diagram illustrating corona wind in a conventional electrostatic precipitator
  • Figure 2A is a schematic perspective view of a conventional electrostatic precipitator
  • Figure 3 is a schematic cross-sectional diagram of an electrostatic precipitator m accordance with a first embodiment of the present invention, illustrating corona wind flow m the precipitator;
  • Figure 4 is a schematic cross-sectional diagram of an electrostatic precipitator in accordance with a further embodiment of the present invention.
  • Figure 5 is a schematic cross-sectionaJ diagram of an electrostatic precipitator in accordance with yet a further embodiment of the present invention, illustrating an actual flow of flue gas through a collection member;
  • Figure 6 is a schematic cross sectional diagram of yet a further embodiment of an electrostatic precipitator m accordance with the present invention.
  • Figure 7 is a plot of a measure of residual particle density against a measure of applied voltage for a precipitator arrangement in accordance with the figure 6 - - embodiment of the present invention, compared with a conventional precipitator arrangement.
  • a major application of electrostatic precipitators is to remove particulate matter from flue gases produced from the burning of fuel for powering electrical power generating stations. Such particulate matter is a major pollutant.
  • the majority of world governments have legislated to force generating companies to make provision for the removal of particulate matter from the exhaust gasses.
  • the provision of arrangements to remove particulate matter is therefore one of the major considerations of an electrical power generator and the conventional electrostatic precipitators which are generally used to remove particulate matter are extremely bulky and not radically efficient.
  • the cost of installing and maintaining conventional, very bulky precipitators is very high.
  • Figure 1 is a schematic, illustrating the position and operation of a precipitator m a coal fired electrical power generating station. It will be appreciated that a precipitator may be employed in other types of power station, such as combined cycle power stations, for example.
  • the power stations fuel in this case coal 50, is burned to heat a boiler 51 to produce steam 52 to power an electrical generator 53 to produce electrical power 54.
  • the gases which are produced by burning of the coal 50 contain large amounts of particulate matter which must be removed before the gases are exhausted to the environment, m order to minimise pollution.
  • the flue gases 55 are lead into an electrostatic precipitator 56 which operates to precipitate out particulate matter from the gases. Clean gas 57 is then exhausted via the cooling tower or stack 58.
  • the particulate matter is precipitated onto collection means 59, which may include a plurality of electrically conductive plates. These plates 59 are periodically rapped so that the particulate matter falls into a dust collector 60 positioned below the plates 59.
  • collection means 59 which may include a plurality of electrically conductive plates. These plates 59 are periodically rapped so that the particulate matter falls into a dust collector 60 positioned below the plates 59.
  • An electrostatic precipitator m m accordance with embodiments of the present invention, to be described in the following, may be employed as the precipitator 56.
  • the precipitator of the present invention preferably results in increased efficiency, which enables the bulk of the precipitator to be reduced over the conventional precipitators, and increases the efficiency of particle collection. It is expected that the precipitators of the present invention will be cheaper and easier to maintain.
  • FIG. 2 illustrates the arrangement m perspective view from above and one side.
  • a precipitator will usually be made up of a plurality of groups 1, 2 of conductors, and collector plates 4 placed in an exhaust flue to clean exhaust gases from a power plant or the like.
  • Figure 2A illustrates two plates 4 and three groups 1, 2 of conductors. In a conventional installation, there will be many more plates and groups of conductors in a stack, but only a small number are shown m the figures, for clarity.
  • the collector plates 4 are usually arranged so that they extend vertically in a flue (as illustrated m Figure 1), although they are shown extending horizontally in the drawings.
  • the electrical connections to the conductors 3 are not shown, for clarity.
  • the precipitator is usually arranged so that the direction of flow of the flue gas is such as to be parallel to the collector plates 4 and also perpendicular to the wires 3, as indicated by arrow A m Figures 2 and 2A.
  • a typical flow velocity is in the order of 1-2 metres per second.
  • a large negative voltage is applied to each of the wires, m the order of 50 kV, and the collector plates - -
  • the electrical corona surrounding the highly charged wires 3 causes particles in the flue gas to become charged and attracted to the grounded collector plate 4. When the particles reach the collector plate 4 they are discharged and stick to it. Plates 4 are periodically rapped to dislodge the particles which are collected m a hopper below the precipitator.
  • a corona wind is produced by movement of charged particles forcing movement of uncharged particles m a convection effect.
  • the arrows B in figure 1 show the flow direction which would be imposed on particles as a corona wind if no force were applied by the flow of flue gas.
  • the applied flow of the flue gas together with the force of the corona wind will result m a vector resultant of actual flow of the flue gas. It can be seen from the experimentally observed flow pattern B which would be applied by the corona wind if there was no applied flue gas flow A, however, that the flows B of opposing groups 1 and 2 of wires are directly opposite to each other.
  • the collector plate 4 is integrally formed, there is no corona wind flow between groups of conductors 3 through the collector plate. In conventional arrangements, therefore, no account is taken of the effect of the corona wind, as can be seen.
  • the opposing flows provided by the corona wind of respective groups 1, 2 of conductors could result m cancelling out any assistance that the corona wind might have given to precipitation of particulate matter.
  • corona wind velocities are in the order of 2 metres per second, which is the same order of magnitude as the - - imposed flow velocity of the flue gas flow. This is significant.
  • FIG. 3 illustrates, in cross-section, an arrangement for a precipitator in accordance with an embodiment of the invention.
  • the arrangement includes a means for producing an electrical field, m this case electrical conductors 6 and a collection means, m this case a louvered collection plate 7.
  • the arrangement is adapted to take into account the effect of a corona wind which is produced by the wires 8,9, the impetus direction of which is indicated by arrows C, such that the corona wind will assist m depositing particles on the collector plate 7.
  • the electric wires 6 are arranged in groups 8, 9 on opposite sides of a collector plate 7. Unlike conventional precipitators, however, opposite wires 6 in the group 8, 9, are staggered with respect to each other, so that, for example, wire 6A is not directly opposite wire 6B, but is staggered relative thereto. Further, because the collector plate 7 is louvered, it will allow gas flow therethrough. The combined effect of this arrangement is to give rise to a corona wind flow impetus direction as indicated by C. The flow pattern will cause gas to flow towards and through the louvered collector plate, as indicated by the arrows.
  • the actual flow of gas will not be as indicated by arrow C but will in fact be a vector result of the applied flue gas flow D and the corona wind impetus C.
  • the vector flow direction is m fact indicated by arrows E and r in the drawing and causes flue gas to pass over the louver plates 7. This has two major advantages.
  • the random motion of the charged particles as they pass through the louvers is such that they are likely to have a much greater chance of striking the surface, discharging and sticking to the surface, than in the conventional configuration.
  • the precipitator of this embodiment will in practice comprise a plurality of stacked louvered collector plates and groups of conductors.
  • the precipitator arrangement described above leads to much greater collection efficiency. This means that smaller, cheaper precipitators can be used.
  • FIG 4 shows a further embodiment of the invention wherein the collector plate has an alternative louvered configuration to the configuration of figure 3.
  • the same reference numerals are used in figure 4 for components corresponding to the components in figure 3.
  • the difference between the embodiment of figure 4 and the embodiment of figure 3 is the arrangement of the louvers 7.
  • the louvers are divided into alternating groups 20 and 21, which lean m opposite directions to each other. Each group of louvers 20 and 21 is separated by a horizontally extending louver 22.
  • the louver arrangement takes into account the combined vector effect of the flue gas flow D and corona wind flow, which results m a flue gas flow through the louvered collector member 7 as indicated by arrows E and F. It can be seen that the louvered plates 20, 21 are essentially parallel to the resultant direction of flue gas flow, thereby presenting the largest possible surface area to gather charged dust particles.
  • Collector plate 7 again comprises a louvered plate made up of a plurality of groups of oppositely extending louvers, 20A and 21A. In this arrangement the louvers are not separated by horizontally extending louvers.
  • the actual direction of flue gas flow due to the effective contributions of the corona wind and originally imposed flue gas flow D is illustrated by arrows G. Again, maximum surface area is presented to gather charged particles.
  • High voltages are used m electrostatic precipitators, as discussed above.
  • One possible problem with the arrangements of figures 3, 4 and 5, is that the sharp edges of the louvers could possibly provide a point for an electric discharge between a conductor and a louver. This is undesirable and would result in a decrease in efficiency.
  • Figure 6 shows a schematic cross-sectional diagram of an electrostatic precipitator which is designed to take into account this possible discharge problem and also, the applicants believe, results m a further improvement to the efficiency of electrostatic precipitators.
  • the arrangement comprises a plurality of conductors 100 which are arranged to produce a corona. These conductors 100 are m the form of elongate wires, as with the conductors of the previously described embodiments. Also as with the previously described embodiments, the conductors are arranged m groups 101, 102, 103, 104, with respective conductors m adjacent groups being staggered with respect to one another. - -
  • the collection means is formed by a plurality of collection members 105 which are also formed into groups 106, 107, 108, 109, interleaved between the respective groups of conductors 100.
  • Each collection member 105 is in the form of an elongate conducting plate having an arcuate or curved profile, as is best seen in the cross section of figure 6.
  • each group 106, 107, 108, 109 of collector plates 105 extends the length of the conductors 100. Adjacent collector members 105 in a group are separated by gaps 110.
  • the staggered conductors 100 produce on a flue gas a corona wind impetus which effects the flow of flue gas D producing the vector result indicated by arrows E. It can be seen that the resultant flow of gas is over the outer curved surfaces of each of the collector members 105. This results in an increase in efficiency and a greater likelihood the precipitation will occur on the plates 105. Note that the arrows E are only illustrated on the lower two groups of collector plates but it will be appreciated that the flow is the same for all of the groups of collector plates.
  • the edges 111 of the plates are curved.
  • This curved surface minimises the chance of breakdown between the wires 100 and the plates 105 and increases the efficiency. This maximises the operating voltage by minimising the possibility of electrical breakdown.
  • the curve also acts to stiffen the plates so that lengths of six to eight meters, for example, can be supported m existing precipitator structures. The rolling of the ends further stiffens the structure. Yet another feature of the arrangement of figure
  • These plates 113 are relatively thick, with rounded edges and shaped to reduce corona. If a significant corona wind were produced by these plates it would not assist precipitation. These plates supply an electric field which enhances precipitation, without causing corona and corona wind.
  • the conductors 113 are charged to a high voltage, in fact to the same voltage, preferably, as the conductors 100, and this charge assists in precipitation on plates 105. In fact, this high voltage plate 113 also collects particles which have become positively charged - - due to back corona and dust layers. These positively charged particles are more efficiently collected by this system which has plates as well as wires at high negative potential (m all previous designs any positively charged particles had only wires to collect them) .
  • the curved earthed electrodes 105, the corona wires 100 and the high voltage plate electrodes 113 should all be periodically rapped in the conventional manner to dislodge accumulated particles.
  • the power supply is a conventional negative polarity variable pulse power supply.
  • Figure 7 shows experimental results of a measure of residual particles against a measure of applied voltage, for an arrangement m which groups of electrodes comprising corona producing electrodes alternate with non- corona producing electrodes, and the collector elements comprise groups of flat plates having gaps between them, i.e. similar to the Figure 6 arrangement, but the collector plates being flat instead of curved. It can be seen that this arrangement is appreciably more efficient than the conventional arrangement.
  • An alternative configuration of electrostatic precipitator may not utilise a corona wind, but instead be designed to provide regions where there is relatively little or no corona wind, such that gas flow is minimised, and collection efficiency is improved m this way.

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  • Electrostatic Separation (AREA)

Abstract

L'invention porte sur des dépoussiéreurs électrostatiques servant à éliminer les matières particulaires de flux de gaz et notamment des fumées produites par les centrales thermiques. Les dépoussiéreurs actuels sont massifs et relativement inefficaces. L'invention prévoit un dépoussiéreur utilisant les effets d'une effluve produite par ses conducteurs pour diriger le gaz vers des plaques de recueil où se produit le dépôt. Elle prévoit également des zones du dépoussiéreur exemptes ou quasi exemptes d'effluves où les matières particulaires séjournent pendant un temps relativement long et sont davantage susceptibles de se déposer.
PCT/AU1997/000298 1996-05-15 1997-05-15 Depoussiereur electrostatique WO1997043044A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU26864/97A AU2686497A (en) 1996-05-15 1997-05-15 Electrostatic precipitator

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPN9865 1996-05-15
AUPN9865A AUPN986596A0 (en) 1996-05-15 1996-05-15 Electrostatic precipitator

Publications (1)

Publication Number Publication Date
WO1997043044A1 true WO1997043044A1 (fr) 1997-11-20

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ID=3794177

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/AU1997/000298 WO1997043044A1 (fr) 1996-05-15 1997-05-15 Depoussiereur electrostatique

Country Status (2)

Country Link
AU (1) AUPN986596A0 (fr)
WO (1) WO1997043044A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105597932A (zh) * 2016-02-18 2016-05-25 北京中和锦程科技有限公司 电晕风空气净化装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4689056A (en) * 1983-11-23 1987-08-25 Nippon Soken, Inc. Air cleaner using ionic wind
WO1988004851A1 (fr) * 1986-12-19 1988-06-30 Astra-Vent Ab Systeme de traitement d'air
WO1992005875A1 (fr) * 1990-10-03 1992-04-16 Astra-Vent Ab Appareil servant a generer et a nettoyer un flux d'air
WO1996011060A1 (fr) * 1994-10-05 1996-04-18 Strainer Lpb Aktiebolag Filtre a air a deux etages assurant une ionisation efficace

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4689056A (en) * 1983-11-23 1987-08-25 Nippon Soken, Inc. Air cleaner using ionic wind
WO1988004851A1 (fr) * 1986-12-19 1988-06-30 Astra-Vent Ab Systeme de traitement d'air
WO1992005875A1 (fr) * 1990-10-03 1992-04-16 Astra-Vent Ab Appareil servant a generer et a nettoyer un flux d'air
WO1996011060A1 (fr) * 1994-10-05 1996-04-18 Strainer Lpb Aktiebolag Filtre a air a deux etages assurant une ionisation efficace

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105597932A (zh) * 2016-02-18 2016-05-25 北京中和锦程科技有限公司 电晕风空气净化装置

Also Published As

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