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WO1996031281A1 - Method and apparatus for extracting dust from gases - Google Patents

Method and apparatus for extracting dust from gases Download PDF

Info

Publication number
WO1996031281A1
WO1996031281A1 PCT/SE1996/000426 SE9600426W WO9631281A1 WO 1996031281 A1 WO1996031281 A1 WO 1996031281A1 SE 9600426 W SE9600426 W SE 9600426W WO 9631281 A1 WO9631281 A1 WO 9631281A1
Authority
WO
WIPO (PCT)
Prior art keywords
granular material
collector electrode
filter device
dust
electrode
Prior art date
Application number
PCT/SE1996/000426
Other languages
French (fr)
Inventor
Harry Johansson
Original Assignee
Senea Filter Ab
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 Senea Filter Ab filed Critical Senea Filter Ab
Priority to AU52937/96A priority Critical patent/AU5293796A/en
Publication of WO1996031281A1 publication Critical patent/WO1996031281A1/en

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
    • B03C3/34—Constructional details or accessories or operation thereof
    • B03C3/74—Cleaning the electrodes
    • B03C3/743—Cleaning the electrodes by using friction, e.g. by brushes or sliding elements
    • 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
    • B03C3/04—Plant or installations having external electricity supply dry type
    • B03C3/14—Plant or installations having external electricity supply dry type characterised by the additional use of mechanical effects, e.g. gravity
    • B03C3/145—Inertia

Definitions

  • the present invention relates to a method of cleansing dust-laden gases in accordance with preamble of Claim 1.
  • the invention also relates to apparatus for carrying out the method.
  • the object of the present invention is to provide a method and apparatus which will not be affected by high temperatures and which will enable dust-laden gases to be cleansed or purified electro- statically in a particularly advantageous manner, even when these gases have very high temperatures.
  • This object is achieved with the method and apparatus defined in the characterizing clauses of re ⁇ spective method and apparatus Claims.
  • the following advantages are among those that are afforded by the invention.
  • the inventive method and apparatus provides both techni ⁇ cal and economical advantages.
  • the method and appara- tus enable highly effective cleansing of very hot process gases whose temperatures are in the order of 700°C or even higher.
  • the apparatus is very reliable in operation and requires the minimum of maintenance. Very good cleansing results can be achieved and so- called thermic separation of different components can be performed.
  • the gas has a very low pressure drop through the gas-cleansing apparatus.
  • the collector electrodes can be cleaned continuously in spite of the high temperatures involved.
  • Fig. 1 illustrates schemati ⁇ cally and partially in section a first embodiment of an inventive electrostatic gas purifier
  • Fig. 2 illustrates schematically and partially in section a second embodiment of an inventive elec- trostatic gas purifier.
  • a device 1 which includes an electrostatic fil ⁇ ter to which the dust-laden gas to be cleansed is passed through a delivery conduit 2, said gas passing up through the electrostatic filter device 1 and exiting through an outlet conduit 3 in which a transport fan 4 is mounted, as illustrated schematically in said Figure.
  • the filter device 1 includes a rod-like emission electrode 5 which is mounted centrally in the flow of hot gas and to which a d.c. voltage of, e.g., 30-70 kV is applied from a voltage source 6.
  • the emission electrode 5 is conveniently provided with pointed protru- sions or like means for promoting the generation of corona dis ⁇ charges.
  • the filter device 1 also includes a collector electrode 7, which in the case of the illustrated embodiment has an annular configuration and surrounds the emission electrode 5.
  • the configuration of the collector electrode arrangement 7 can be likened to a wandering curtain of gravel-like material or some other granular material. Movement of the gravel or granules 8 through the filter device is steered by annular lamellae 9 which are obliquely positioned in the fashion of jalousie slats, such as to define gaps 10 between the various lamellae 9.
  • the lamellae 9 are inclined so that the gravel ⁇ like material can run externally therealong without said material 8 running through the aforesaid gaps 10 and entering the gas through- flow duct 11 of said filter device.
  • the angle of inclination of the lamellae 9 is shown in Fig. 1.
  • a circular outer casing 12 is pro ⁇ vided outside the lamellae 9, wherein the gravel-like material 8 runs between the lamellae 9 and the outer casing 12 under the force of gravity.
  • the gravel-like material 8 is delivered to the filter device in Fig. 1 through a delivery conduit 13 and exits through an outlet conduit 14.
  • the gravel-like material or granular material can be handled with the aid of a pneumatic conveyor or a hot goods elevator, for instance.
  • the lamellae 9 and the outer casing 12 are electrically conductive and electrically earthed, and may be comprised of steel, for in ⁇ stance.
  • the gravel-like material or granular material 8 may also be electrically conductive and may consist of iron ore crush or steel balls, although it is also possible to use electrically non- conductive gravel or other granular material.
  • the collector electrode 7 of the Fig. 1 embodiment can be said to include the lamellae 9, the outer casing 12 and the granular mate ⁇ rial 8.
  • the inventive filter device illustrated in Fig. 1 operates in the following manner. Hot dust-laden gas to be cleansed, or purified, is delivered to the filter device 1 through the delivery conduit 2, whereafter the gas passes through the centre portion 11 of the device, i.e. in the region between the voltage-applied emission electrode 5 and the electrically earthed collector electrode 7.
  • the granular material 8 is allowed to run slowly down in the region between the lamellae 9 and the outer casing 12 and the dust present in the gas is transferred therefrom to the collecting electrode 7, i.e. to the granular material 8, the lamellae 9 and the inner sur- face of the outer casing 12, under the effect of the electric field thus generated.
  • the downwardly running granular material 8 keeps the metal surfaces free from dust and, at the same time, transports the dust away from the gas flow.
  • the granular material 8 departing from the filter device 1 through the outlet conduit 14 is cleansed from dust and thereafter returned to the filter device 1 via the delivery conduit 13. If the dust has a tacky or elastic nature such as to form dust lumps or agglomerates, the dust can be readily removed from the mass of granular material by sieving or screening said material, for instance.
  • the cleansed, hot gas leaves the fil- ter device 1 through the outlet conduit 3 for further handling.
  • the embodiment illustrated in Fig. 2 differs from the Fig. 1 em ⁇ bodiment by virtue of comprising a plurality of emission electrodes 5' and collector electrodes 7', 20, and by virtue of dividing the gas flow through the filter device I'into a plurality of mutually parallel part-flows.
  • the Fig. 2 embodiment also includes a number of internal collector electrodes 20.
  • the inner collector electrodes 20 include double, obliquely positioned lamellae 21, 22 which are also electrically earthed, wherewith gaps 23, 24 are provided between the various lamellae 21, 22 and wherein the lamellae are inclined at an angle which enables granular material to run between the vertically disposed lamellae rows in a spill-free fashion.
  • the flow of granular material is divided such that granules 8 will run in all collector electrodes 7' and 20.
  • the filter device will conveniently include a plurality of granular material 8 inlet and outlet conduits.
  • the collector electrodes 7' of the Fig. 2 embodiment can be said to include the lamellae 9', the outer casing 12' and the granular material 8.
  • the collector electrodes 20 can be said to include the lamellae 21, 22 and the granular material 8.
  • the cross-sectional shape of the filter device may be either circular or rectangular, or some other shape.
  • the design of the emission electrode may also vary.
  • the design of the collector electrode may also be modified provided that it permits a flow of dust-collecting granular material.
  • the direction in which the gas flows through the filter device may also be varied if desired.
  • the choice of material from which the emission electrodes, collec ⁇ tor electrodes and the granular material are comprised may also be varied, of course.
  • the central feature of the invention is that the inventive collec ⁇ tor electrode is cleansed continuously and that the granular mate ⁇ rial continuously carries away from the filter device dust that precipitates therein during a gas-cleansing or purifying operation.

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  • Electrostatic Separation (AREA)

Abstract

The invention relates to a method and to an apparatus for cleansing or purifying dust-laden gases, particularly hot process gases, with the aid of an electrostatic filter device (1; 1') which includes at least one emission electrode (5; 5') and at least one collector electrode (7; 7', 20). There is used a granular material (8) which passes along the collector electrode and which cleanses the surfaces thereof. At the same time, dust collected on the collector electrode is carried away from the filter device together with the granular material. The granular material (8) moves down the collector electrode (7; 7', 20) under the influence of gravity. The granular material (8) is cleansed and recycled to the filter device (1; 1').

Description

METHOD AND APPARATUS FOR EXTRACTING DϋST FROM GASES
The present invention relates to a method of cleansing dust-laden gases in accordance with preamble of Claim 1. The invention also relates to apparatus for carrying out the method.
The principle according to which electrostatic dust filters func¬ tion has long been known to the art. In order to achieve a satis¬ factory gas-cleansing result, it is particularly important that the collector electrode or electrodes of the electrostatic filter is/are effectively cleaned in order to prevent layers and coatings of electrically insulating dust from collecting and impairing the function of the collector electrode (s) .
Known electrostatic filter constructions are normally limited to function in gas temperatures of up to about 450°C. One problem is that dust that cakes on the collector electrodes becomes electri¬ cally insulating and prevents the flow of electric current between emission electrodes and collector electrodes. Mechanical removal of these dust cakes with the aid of an impact or knocking mechanism or some corresponding mechanism presents a problem. This problem in¬ creases with increasing temperatures, due to deterioration of the impulse effect on the collector electrode at higher temperatures. High operating temperatures also create a problem with regard to filter house construction.
The object of the present invention is to provide a method and apparatus which will not be affected by high temperatures and which will enable dust-laden gases to be cleansed or purified electro- statically in a particularly advantageous manner, even when these gases have very high temperatures. This object is achieved with the method and apparatus defined in the characterizing clauses of re¬ spective method and apparatus Claims. The following advantages are among those that are afforded by the invention. The inventive method and apparatus provides both techni¬ cal and economical advantages. For instance, the method and appara- tus enable highly effective cleansing of very hot process gases whose temperatures are in the order of 700°C or even higher. The apparatus is very reliable in operation and requires the minimum of maintenance. Very good cleansing results can be achieved and so- called thermic separation of different components can be performed. The gas has a very low pressure drop through the gas-cleansing apparatus. The collector electrodes can be cleaned continuously in spite of the high temperatures involved.
The invention will now be described in more detail with reference to an exemplifying embodiment thereof and also with reference to the accompanying drawings, in which Fig. 1 illustrates schemati¬ cally and partially in section a first embodiment of an inventive electrostatic gas purifier; and Fig. 2 illustrates schematically and partially in section a second embodiment of an inventive elec- trostatic gas purifier.
Shown in Fig. 1 is a device 1 which includes an electrostatic fil¬ ter to which the dust-laden gas to be cleansed is passed through a delivery conduit 2, said gas passing up through the electrostatic filter device 1 and exiting through an outlet conduit 3 in which a transport fan 4 is mounted, as illustrated schematically in said Figure.
The filter device 1 includes a rod-like emission electrode 5 which is mounted centrally in the flow of hot gas and to which a d.c. voltage of, e.g., 30-70 kV is applied from a voltage source 6. The emission electrode 5 is conveniently provided with pointed protru- sions or like means for promoting the generation of corona dis¬ charges.
The filter device 1 also includes a collector electrode 7, which in the case of the illustrated embodiment has an annular configuration and surrounds the emission electrode 5. The configuration of the collector electrode arrangement 7 can be likened to a wandering curtain of gravel-like material or some other granular material. Movement of the gravel or granules 8 through the filter device is steered by annular lamellae 9 which are obliquely positioned in the fashion of jalousie slats, such as to define gaps 10 between the various lamellae 9. The lamellae 9 are inclined so that the gravel¬ like material can run externally therealong without said material 8 running through the aforesaid gaps 10 and entering the gas through- flow duct 11 of said filter device. The angle of inclination of the lamellae 9 is shown in Fig. 1. A circular outer casing 12 is pro¬ vided outside the lamellae 9, wherein the gravel-like material 8 runs between the lamellae 9 and the outer casing 12 under the force of gravity. The gravel-like material 8 is delivered to the filter device in Fig. 1 through a delivery conduit 13 and exits through an outlet conduit 14. The gravel-like material or granular material can be handled with the aid of a pneumatic conveyor or a hot goods elevator, for instance.
The lamellae 9 and the outer casing 12 are electrically conductive and electrically earthed, and may be comprised of steel, for in¬ stance. The gravel-like material or granular material 8 may also be electrically conductive and may consist of iron ore crush or steel balls, although it is also possible to use electrically non- conductive gravel or other granular material. The collector electrode 7 of the Fig. 1 embodiment can be said to include the lamellae 9, the outer casing 12 and the granular mate¬ rial 8.
The inventive filter device illustrated in Fig. 1 operates in the following manner. Hot dust-laden gas to be cleansed, or purified, is delivered to the filter device 1 through the delivery conduit 2, whereafter the gas passes through the centre portion 11 of the device, i.e. in the region between the voltage-applied emission electrode 5 and the electrically earthed collector electrode 7. The granular material 8 is allowed to run slowly down in the region between the lamellae 9 and the outer casing 12 and the dust present in the gas is transferred therefrom to the collecting electrode 7, i.e. to the granular material 8, the lamellae 9 and the inner sur- face of the outer casing 12, under the effect of the electric field thus generated. The downwardly running granular material 8 keeps the metal surfaces free from dust and, at the same time, transports the dust away from the gas flow. The granular material 8 departing from the filter device 1 through the outlet conduit 14 is cleansed from dust and thereafter returned to the filter device 1 via the delivery conduit 13. If the dust has a tacky or elastic nature such as to form dust lumps or agglomerates, the dust can be readily removed from the mass of granular material by sieving or screening said material, for instance. The cleansed, hot gas leaves the fil- ter device 1 through the outlet conduit 3 for further handling.
The embodiment illustrated in Fig. 2 differs from the Fig. 1 em¬ bodiment by virtue of comprising a plurality of emission electrodes 5' and collector electrodes 7', 20, and by virtue of dividing the gas flow through the filter device I'into a plurality of mutually parallel part-flows. In addition to comprising the peripherally mounted collector electrode 7' in accordance with the earlier de¬ scribed embodiment, the Fig. 2 embodiment also includes a number of internal collector electrodes 20. The inner collector electrodes 20 include double, obliquely positioned lamellae 21, 22 which are also electrically earthed, wherewith gaps 23, 24 are provided between the various lamellae 21, 22 and wherein the lamellae are inclined at an angle which enables granular material to run between the vertically disposed lamellae rows in a spill-free fashion. In the case of the Fig. 2 embodiment, the flow of granular material is divided such that granules 8 will run in all collector electrodes 7' and 20. The filter device will conveniently include a plurality of granular material 8 inlet and outlet conduits.
The collector electrodes 7' of the Fig. 2 embodiment can be said to include the lamellae 9', the outer casing 12' and the granular material 8. The collector electrodes 20 can be said to include the lamellae 21, 22 and the granular material 8.
The illustrated and described embodiments have, in principle, func¬ tional similarities and a closer description of the manner in which the Fig. 2 embodiment operates is considered unnecessary. Those components of the Fig. 2 embodiment that find correspondence in the Fig. 1 embodiment have been referenced with the same reference numeral to which a prime has been added.
It will be understood that many variations are possible with regard to the structural design of the inventive device. Naturally, the cross-sectional shape of the filter device may be either circular or rectangular, or some other shape. The design of the emission electrode may also vary. The design of the collector electrode may also be modified provided that it permits a flow of dust-collecting granular material.
The direction in which the gas flows through the filter device may also be varied if desired. The choice of material from which the emission electrodes, collec¬ tor electrodes and the granular material are comprised may also be varied, of course.
The central feature of the invention is that the inventive collec¬ tor electrode is cleansed continuously and that the granular mate¬ rial continuously carries away from the filter device dust that precipitates therein during a gas-cleansing or purifying operation.
It will therefore be understood that the invention is not re¬ stricted to the illustrated and described exemplifying embodiments thereof and that modifications and changes are conceivable within the scope of the following Claims.

Claims

1. A method of cleansing or purifying dust-laden gases, particu¬ larly hot process gases, with the aid of an electrostatic filter device (1; 1') which includes at least one emission electrode (5; 5') and at least one collector electrode (7; 7', 20), characterized by using in conjunction with the collector electrode (7; 7', 20) a granular material (8) which moves along the collector electrode and cleans the surfaces thereof while, at the same time, carrying away from the filter device dust that has collected on the collector electrode, together with the granular material.
2. A method according to Claim 1, characterized by allowing granu¬ lar material (8) to move along the collector electrode (7; 7', 20) under the force of gravity.
3. A method according to Claim 1 or Claim 2, characterized by cleaning the granular material (8) and recycling said material back to the filter device (1; 1').
4. Apparatus for cleansing or purifying dust-laden gases, particu¬ larly hot process gases, said apparatus including an electrostatic filter device (1; 1') which includes at least one emission elec¬ trode (5; 5') and at least one collector electrode (7; 7', 20), characterized in that the collector electrode (7; 7', 20) includes a granular material (8) intended to pass along the collector elec¬ trode such as to cleanse the surfaces thereof and to collect the dust content of the gas, said dust content being carried away from the filter device together with the granular material.
5. Apparatus according to Claim 4, characterized in that the col¬ lector electrode (7; 7', 20) includes means (9, 12; 9', 12', 21, 22) for guiding the granular material (8) in its movement along the collector electrode.
6. Apparatus according to Claim 5, characterized in that said guide means includes jalousie-like obliquely positioned lamellae
(9; 9', 21, 22) .
7. Apparatus according to any one of Claims 4-6, characterized in that the granular material (8) is electrically conductive.
8. Apparatus according to any one of Claims 4-6, characterized in that the granular material (8) is electrically non-conductive.
PCT/SE1996/000426 1995-04-05 1996-04-02 Method and apparatus for extracting dust from gases WO1996031281A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU52937/96A AU5293796A (en) 1995-04-05 1996-04-02 Method and apparatus for extracting dust from gases

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9501245-6 1995-04-05
SE9501245A SE504411C2 (en) 1995-04-05 1995-04-05 Method and apparatus for purifying dust-laden gases

Publications (1)

Publication Number Publication Date
WO1996031281A1 true WO1996031281A1 (en) 1996-10-10

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Application Number Title Priority Date Filing Date
PCT/SE1996/000426 WO1996031281A1 (en) 1995-04-05 1996-04-02 Method and apparatus for extracting dust from gases

Country Status (3)

Country Link
AU (1) AU5293796A (en)
SE (1) SE504411C2 (en)
WO (1) WO1996031281A1 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2133116A1 (en) * 1997-10-10 1999-08-16 Unisystems S A Electrostatic filter
WO2011163052A3 (en) * 2010-06-21 2012-03-08 Tessera, Inc. Granular abrasive cleaning of an emitter wire
EP1958696A3 (en) * 2007-02-16 2013-04-24 Otto Spanner GmbH Electrofilter
US8482898B2 (en) 2010-04-30 2013-07-09 Tessera, Inc. Electrode conditioning in an electrohydrodynamic fluid accelerator device
AT516061A4 (en) * 2015-03-04 2016-02-15 Gerlinger Ernst boiler

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994006563A1 (en) * 1992-09-21 1994-03-31 Edmeston Ab Method for pollution emission reduction from glass melting furnace

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994006563A1 (en) * 1992-09-21 1994-03-31 Edmeston Ab Method for pollution emission reduction from glass melting furnace

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2133116A1 (en) * 1997-10-10 1999-08-16 Unisystems S A Electrostatic filter
EP1958696A3 (en) * 2007-02-16 2013-04-24 Otto Spanner GmbH Electrofilter
US8482898B2 (en) 2010-04-30 2013-07-09 Tessera, Inc. Electrode conditioning in an electrohydrodynamic fluid accelerator device
WO2011163052A3 (en) * 2010-06-21 2012-03-08 Tessera, Inc. Granular abrasive cleaning of an emitter wire
AT516061A4 (en) * 2015-03-04 2016-02-15 Gerlinger Ernst boiler
AT516061B1 (en) * 2015-03-04 2016-02-15 Gerlinger Ernst boiler

Also Published As

Publication number Publication date
AU5293796A (en) 1996-10-23
SE504411C2 (en) 1997-02-03
SE9501245L (en) 1996-10-06
SE9501245D0 (en) 1995-04-05

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