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WO2008074969A1 - Cellule à plasma non thermique - Google Patents

Cellule à plasma non thermique Download PDF

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Publication number
WO2008074969A1
WO2008074969A1 PCT/GB2007/002088 GB2007002088W WO2008074969A1 WO 2008074969 A1 WO2008074969 A1 WO 2008074969A1 GB 2007002088 W GB2007002088 W GB 2007002088W WO 2008074969 A1 WO2008074969 A1 WO 2008074969A1
Authority
WO
WIPO (PCT)
Prior art keywords
air
plasma cell
thermal plasma
flow guide
guide element
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.)
Ceased
Application number
PCT/GB2007/002088
Other languages
English (en)
Inventor
Alan Mole
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.)
Tri Air Developments Ltd
Original Assignee
Tri Air Developments Ltd
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 Tri Air Developments Ltd filed Critical Tri Air Developments Ltd
Publication of WO2008074969A1 publication Critical patent/WO2008074969A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/32—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by electrical effects other than those provided for in group B01D61/00
    • B01D53/323—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by electrical effects other than those provided for in group B01D61/00 by electrostatic effects or by high-voltage electric fields
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/48—Generating plasma using an arc
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H2245/00—Applications of plasma devices
    • H05H2245/10—Treatment of gases
    • H05H2245/15—Ambient air; Ozonisers

Definitions

  • the present invention relates to a non-thermal plasma cell, preferably but not exclusively for decontaminating polluted air, to a method of increasing residence time of air within a non-thermal plasma cell without significantly increasing back-pressure, and to a method of providing a spiral air flow guide element in a non-thermal plasma cell.
  • Non-thermal plasma cells are known.
  • a non-thermal cell comprises two Mgh-voltage and high-frequency electrodes separated by a space or dielectric which is sufficient to prevent arcing, but close enough to create an intense electrical field.
  • the dielectric is electrically of very low-conductivity, but air within the dielectric is subject to an intense electron 'bombardment'. Collisions between the electrons generated by the electric field and the outer ring elections of the atoms of the component molecules of air create a plasma.
  • This, in the field is designated 'non-thermal% since, although the energy generated by the electron collisions is high, typically around 700 degrees Kelvin and higher the mass of the electrons is low. Consequently, there is almost no ionisation of the much more massive protons, and the overall temperatures in the plasma remain low, typically in the range of 10 Celsius to 80 Celsius.
  • non-thermal plasma cell for use as part of a non-thermal plasma filter
  • an important consideration is the residence time of the air within the cell. If air passes through the plasma cell too quickly, destruction of any pollutant particles is low, and thus decontamination of the air is poor.
  • increasing the residence time of the air within the plasma cell inevitably results in increasing back-pressure, thus requiring far greater energy to maintain an air-flow through the non-thermal plasma cell. As ihe.baek-pressuK increases, so the energy requirement to force air through the filter and to maintain the plasma logarithmically increases.
  • One kind of plasma cell consists of an open-ended elongate tubular cylindrical eartt electrode with an elongate high-voltage wire electrode coaxially provided within th ⁇ tubular cylindrical electrode.
  • This arrangement is not ideal, since, although the tubular earth electrode has no obstruction, thus resulting in almost no back-pressure, to achieve destruction of even simple pollutant particles within the air, the cell must be extremely long, typically over one metre to achieve sufficient residence time of the air within the plasma.
  • a further problem associated with this open-tube arrangement is the support of the central high-voltage wire electrode within the tubular earth electrode. Sagging inevitably occurs over such a long length, thus resulting in arcing and poor plasma generation.
  • Another kind of plasma cell utilises porous electrode plates, spaced by a densely packed bed of dielectric material.
  • the cell is typically only millimetres wide, in order to limit back-pressure and energy consumption. Consequently, either residence time of air within the cell is extremely short, in order to achieve treatment of any significant volume of air, or air-flow rate is extremely low to increase residence time, which impacts rate of treatment.
  • the present invention therefore seeks to provide a non-thermal plasma cell with increased residence time of air within the cell, without significantly increasing back-pressure.
  • a non-thermal plasma cell for a non-thermal plasma filter, the plasma cell comprising an elongate tubular cylindrical earth element, an elongate high-voltage electrode provided coaxially in flie tubular earth element, and an air flow guide element for imparting rotation to an air flow stream flowing in the tubular earth element, the air flow guide element having an air-flow directing surface which extends at anon-parallel angle to a longitudinal extent of the high-voltage electrode.
  • a method of increasing residence time of air within a non-thermal plasma cell without significantly increasing back-pressure comprising the steps of : a) providing a plasma cell having an elongate tubular cylindrical earth element and a coaxial elongate high-voltage electrode; and b) providing an air flow guide element in the tubular earth element of the plasma cell, the air flow guide element having an air-flow directing surface which extends at a non- parallel angle to a longitudinal extent of the high-voltage electrode and which is adapted to impart rotation to an air flow stream flowing in the tubular earth element.
  • the method further comprises a step c), subsequent to step b), of providing a dielectric coating on an interior surface of the tubular earth element and/or on the air-flow directing surface of the air flow guide element, so that pollutant particles in the air stream are centrifugally forced outwards by the rotation imparted to the air stream, and absorbed by the dielectric coating.
  • a method of providing a spiral air flow guide element in a non-thermal plasma cell having an elongate tubular cylindrical earth element and a coaxial elongate high-voltage electrode comprising the steps of : a) hanging a strip of flexible settable electrically-insulating material from the high-voltage electrode; b) rotating one end of the flexible strip relative to the other end to form a spiral around the electrode; and c) setting the spiral strip, the set spiral strip forming an air flow guide element around the electrode for imparting rotation to an air flow stream flowing in the tubular earth element, the air flow guide element having an air-flow directing surface which extends at a non-parallel angle to a longitudinal extent of the high-voltage electrode.
  • a method of providing the air flow guide element in a non-thermal plasma cell in accordance with the third aspect of the invention comprising the steps of : a) hanging a strip of flexible settable electrically-insulating material from the high-voltage electrode; b) rotating one end of the flexible strip relative to the other end to form a spiral around the electrode; and c) setting the spiral strip, the set spiral strip forming the air flow guide element around the electrode for imparting rotation to an air flow stream flowing in the tubular earth element.
  • Figure 1 is a perspective view showing a non-thermal plasma cell for a non-thermal plasma filter, in accordance with the first aspect of the invention.
  • Figure 2 is a diagrammatic view of a central high-voltage electrode of the plasma cell, with a strip of flexible settable electrically-insulating material hung therefrom along a major portion of its longitudinal extent.
  • the plasma cell 10 comprises an open-ended elongate tubular cylindrical electrical-earth electrode element 12, an elongate high-voltage wire electrode 14, and an air-flow guide element 16.
  • the tubular earth element 12 forms the earth or ground electrode, and is formed from a rigid electrically conductive material, such as metal, for example, steel or stainless steel.
  • the elongate high-voltage electrode 14 is centrally mounted coaxially within the tubular earth element 12, and typically has threaded ends 18 to enable simple connection to a high- voltage and high-frequency power supply.
  • the elongate high-voltage electrode 14 is formed from electrically conductive material, such as metal, for example copper or stainless steel, and preferably extends the entire longitudinal extent of the tubular earth element 12 and projects from the open ends 20.
  • the air-flow guide element 16 is a one-piece spiral element which extends spirally around the elongate high-voltage electrode 14.
  • the air-flow guide element 16 extends continuously along the entire or substantially entire longitudinal extent of the tubular earth element 12, and thus supports the elongate high-voltage electrode 14 coaxially within the tubular earth element 12.
  • the flexible settable electrically-nonconductive material can be, for example, glass fibre cloth.
  • a length of the strip 22 is equal to the length of tubular earth element 12 plus fifty percent, and a width is equal to the internal radius of the tubular earth element 12 minus the outside radius of the elongate high-voltage electrode 14.
  • the strip 22 of material is temporarily attached to the elongate high-voltage electrode 14 via a plurality of spaced hanging elements 24.
  • the hanging elements 24 are preferably formed from combustible material, such as nylon monofilament cord.
  • the strip 22 is held stationary at one end 26, relative to the elongate high-voltage electrode 14, and the other end 28 is rotated around the longitudinal axis of the elongate high-voltage electrode 14, to form a smooth spiral without kinks or folds. Rotation is continued until the spirally wound strip 22 has a longitudinal extent which matches or substantially matches the length of the tubular earth element 12.
  • the spiral strip 22 and high-voltage electrode 14 are transferred to a kiln or oven and flash- heated momentarily to fiise the fibres of the glass in the strip 22, and to destroy the hanging elements 24. On removal and cooling, a smooth rigid spiral is formed around the high- voltage electrode 14.
  • the rigid spiral and high-voltage electrode 14 are then inserted into the tubular earth element 12. Due to the width of the spiral strip 22, the high-voltage electrode 14 is folly supported along its entire longitudinal extent coaxially within the tubular earth element 12.
  • the rigid spiral forms the air-flow guide element 16. Since the spiral air-flow guide element 16 has a width which extends folly from the high-voltage electrode 14 to the interior surface 30 of the tubular earth element 12, the guide element 16 has an air-flow directing surface 32 which defines a spiral air-flow path (arrows X) through the tubular earth element 12, and around the high-voltage electrode 14. Consequently, air-flowing in the tubular earth element 12 is forced to rotate.
  • the plasma cell 10 further comprises an absorptive dielectric coating 34.
  • a settable dielectric material such as liquid alumina ceramic comprising alumina particles of one to two millimetres in diameter.
  • the plasma cell 10 is removed and the exterior surfaces 36 are wiped clean of dielectric material.
  • the internally-coated cell 10 is then transferred back to the kiln or oven for firing.
  • the interior dielectric coating 34 sets, rigidly holding the high-voltage electrode 14 to the spiral air-flow guide element 16, and the spiral air-flow guide element 16 to the interior surface 30 of the tubular earth element 12.
  • the non-thermal plasma cell 10 can then be connected to the power supply.
  • the cell 10 can also be arranged as part of an array of such cells for treatment of larger volumes of air.
  • spiral air flow guide element extends the air flow pathway within the tubular earth element by fifty percent, and thus increases residence time of air within the tubular earth element by fifty percent.
  • back-pressure although increased when compared to a simple open-tube plasma cell having a rectilinear flow path therethrough, remains low.
  • a further significant advantage achieved by the provision of the spiral air flow guide element is the impartation of centrifugal force on the air flowing within the tubular earth element. Pollutant particles within the air stream are typically heavier, and thus, due to the rapid rotation of the air stream, are forced radially outwards by centrifugal force. The pollutant particles are thus readily absorbed and destroyed by the interior coating of dielectric material. Consequently, greatly improved decontamination of polluted air flowing the plasma cell is achieved. This is particularly relevant to air which contains harmful biological agents and which must be rapidly decontaminated.
  • the rate of winding of the spiral air flow guide element can be uniform along its longitudinal extent, or non-uniform, as necessity dictates.
  • the rate of winding from cell to cell can be altered, simply by altering the length of the strip of flexible settable electrically- nonconductive material.
  • the spiral air flow guide element although continuous along the longitudinal extent of the tubular earth element, can be provided in discrete parts, joined together or spaced apart along the longitudinal extent.
  • the spiral air flow guide element is typically flush with the open ends of the tubular earth element, but may project from one or both ends, or may have a longitudinal extent which is less than that of the tubular earth element.
  • the air flow guide element is itself a spiral having two opposing spiral surfaces, it is feasible that the air flow guide element is formed with only one spiral air-flow directing surface.
  • the air-flow directing surface of the air flow guide element is spiral.
  • the air flow guide element must impart rotation to the air stream flowing in the tubular earth element.
  • the air-flow directing surface does not necessarily have to define a spiral air-flow path.
  • the air flow guide element can be or include an arcuate or planar vane or a plurality of such vanes spaced circumferentially from each other, thus defining one or more arcuate air-flow paths around the high-voltage electrode.
  • the interior dielectric coating can be dispensed with.
  • the interior dielectric coating is essential.
  • the dielectric coating should be provided on at least the upstream facing surface of the air-flow guide element. Consequently, the dielectric coating on the interior of the tubular earth element and/or on the high-voltage electrode could be dispensed with.
  • non-thermal plasma cell for anon-thermal plasma filter with a greatly improved decontamination effectiveness per cubic metre of air treated. It is also possible to provide a non-thermal plasma cell which has increased residence time of air therewithin, but which does not, in relative terms, have a significant increase in back- pressure.
  • a simple method of construction is provided, making the cell simple and cost- effective to produce. It is also possible to retrofit the non-thermal plasma cell in place of elongate tubular cells already in operation.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
  • Plasma Technology (AREA)

Abstract

Une cellule (10) à plasma non thermique pour un filtre à plasma non thermique comprend un élément (12) de masse cylindrique tubulaire allongé, une électrode (14) haute tension allongée disposée coaxialement dans l'élément (12) de masse tubulaire, et un élément (16) de guidage de courant d'air pour conférer une rotation à un flux de courant d'air s'écoulant dans l'élément (12) de masse tubulaire. L'élément (16) de guidage de courant d'air a une surface (32) de direction de courant d'air qui s'étend à un angle non parallèle dans la dimension longitudinale de l'électrode (14) haute tension. L'invention concerne également des procédés.
PCT/GB2007/002088 2006-12-20 2007-06-07 Cellule à plasma non thermique Ceased WO2008074969A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0625496.5 2006-12-20
GB0625496A GB2444976A (en) 2006-12-20 2006-12-20 Non-thermal plasma filter for decontaminating gases

Publications (1)

Publication Number Publication Date
WO2008074969A1 true WO2008074969A1 (fr) 2008-06-26

Family

ID=37734587

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2007/002088 Ceased WO2008074969A1 (fr) 2006-12-20 2007-06-07 Cellule à plasma non thermique

Country Status (2)

Country Link
GB (1) GB2444976A (fr)
WO (1) WO2008074969A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013076459A1 (fr) 2011-11-25 2013-05-30 Tri-Air Developments Limited Cellule de plasma non thermique

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3976448A (en) * 1972-04-20 1976-08-24 Lin Eng Corporation Electrostatic and sonic gas processing apparatus
JPS5268095A (en) * 1975-12-03 1977-06-06 Hitachi Ltd Device for ozone generation
US4159971A (en) * 1976-02-19 1979-07-03 Arthur Gneupel Ozone generator
WO1992010429A1 (fr) * 1990-12-06 1992-06-25 Klausen Lauritz Nicolai Balsle Procede et generateur d'ozone destine a conditionner l'air et/ou un liquide
US6190622B1 (en) * 1998-05-14 2001-02-20 Fantom Technologies Inc. Ozone generator
WO2003010088A1 (fr) * 2001-07-25 2003-02-06 Precisionh2 Inc Production d'hydrogene et de carbone a partir de gaz naturel ou de methane a l'aide de plasma non thermique obtenu par decharge a barriere dielectrique

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH115013A (ja) * 1997-06-16 1999-01-12 Kenji Inoue 排ガス処理装置
NO983106D0 (no) * 1998-07-03 1998-07-03 Applied Plasma Physics As Elektrode for bruk ved generering av ikke-termisk plasma
GB9924999D0 (en) * 1999-10-22 1999-12-22 Aea Technology Plc Reactor for the plasma treatment of gases
GB2415774B (en) * 2004-06-30 2007-06-13 Alan Mole Air decontamination device and method

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3976448A (en) * 1972-04-20 1976-08-24 Lin Eng Corporation Electrostatic and sonic gas processing apparatus
JPS5268095A (en) * 1975-12-03 1977-06-06 Hitachi Ltd Device for ozone generation
US4159971A (en) * 1976-02-19 1979-07-03 Arthur Gneupel Ozone generator
WO1992010429A1 (fr) * 1990-12-06 1992-06-25 Klausen Lauritz Nicolai Balsle Procede et generateur d'ozone destine a conditionner l'air et/ou un liquide
US6190622B1 (en) * 1998-05-14 2001-02-20 Fantom Technologies Inc. Ozone generator
WO2003010088A1 (fr) * 2001-07-25 2003-02-06 Precisionh2 Inc Production d'hydrogene et de carbone a partir de gaz naturel ou de methane a l'aide de plasma non thermique obtenu par decharge a barriere dielectrique

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Week 197729, Derwent World Patents Index; AN 1977-51108Y, XP002451499 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013076459A1 (fr) 2011-11-25 2013-05-30 Tri-Air Developments Limited Cellule de plasma non thermique
CN104041193A (zh) * 2011-11-25 2014-09-10 特利埃尔发展有限公司 非热等离子单体

Also Published As

Publication number Publication date
GB2444976A (en) 2008-06-25
GB0625496D0 (en) 2007-01-31

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