Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J65/00—Lamps without any electrode inside the vessel; Lamps with at least one main electrode outside the vessel
  • H01J65/04—Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating plasma display panels
  • H01J65/042—Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating plasma display panels by an external electromagnetic field
  • H01J65/046—Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating plasma display panels by an external electromagnetic field the field being produced by using capacitive means around the vessel
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/52—Cooling arrangements; Heating arrangements; Means for circulating gas or vapour within the discharge space

Definitions

• This invention deals generally with the use of ultraviolet radiation to sterilize liquids and more specifically with a high power excimer lamp structure used to expose liquids to intense ultraviolet radiation to kill bacteria, even when the liquids are essentially opaque to ultraviolet radiation.
• Excimer lamps are essentially gas filled enclosures which are subjected to high voltage AC power by electrodes which are outside of, but in contact with, the enclosure.
• the lamp enclosures are constructed of a material such as quartz, so that they are transparent to ultraviolet radiation.
• the lamp acts as the dielectric of a capacitor in which the electrodes are the plates of the capacitor, and, as in all capacitors, the dielectric provides all the impedance and uses all the power.
• the envelope is usually formed of concentric cylinders sealed together at the ends, with the gas fill between the cylinders. The metal electrodes are then additional cylinders in contact with the outer surface of the outer quartz cylinder and inner surface of the inner cylinder.
• the electrode in contact with the outer surface of the lamp envelope has typically been a mesh which is partially transparent to ultraviolet radiation or a metal film which is so thin that some ultraviolet radiation passes through it.
• Such electrodes must also be capable of handling high electrical currents. That requires that they have significant volume in order to prevent limiting the electrical current or causing resistance heating.
• This high current requirement eliminates thin films and increases wire thickness in a mesh so greatly that the mesh blocks significant amounts of the ultraviolet radiation output. It then becomes a diminishing tradeoff in which the thick wire screens required for higher power levels block more of the ultraviolet radiation output which should be available for treatment of the liquid.
• the same mesh with large wires interferes with the cooling of the lamp surface, and when excimer lamps increase in temperature lamp efficiency and life are adversely affected.
• the present invention overcomes the dilemma caused by using mesh electrodes when purifying liquids with high power ultraviolet radiation lamps by completely eliminating all the metal electrodes in contact with the lamp envelope.
• the excimer lamp of the invention is powered by high voltage AC, but has no metallic electrodes within or in contact with the envelope.
• the lamp is constructed in the form of two concentric quartz cylinders sealed together at their ends with the excimer gas fill between the cylinders. Cooling liquid is pumped through the central region inside the inner quartz cylinder where an electrically conductive pipe that is not in contact with the inner cylinder is used to supply this cooling liquid. Although it is not in contact with the inner quartz cylinder, this central pipe also acts as the high voltage electrode. A cable attaches the central pipe to a high voltage AC power source, but this high voltage electrode is electrically isolated from the source of cooling liquid by a suitably long length of electrically insulated tubing which also supplies the cooling liquid.
• the entire lamp is enclosed within an outer metal cylindrical sheath which is also not in contact with the quartz envelope, but is connected to the return of the high voltage AC power source and is also grounded.
• the liquid to be treated flows through the metal sheath and over the outside surface of the external envelope of the excimer lamp.
• the electrical circuit is dependent on the fact that the power applied to the lamp is alternating current, and, therefore, power can be transferred through capacitances.
• the two different liquid layers, cooling liquid inside the inner cylinder and treated liquid outside the outer cylinder, are the only electrical power feeds to the lamp and, although they theoretically have some conduction, they essentially act as capacitors to couple AC power to the excimer lamp.
• These liquid filled capacitors have little power loss because the liquids have high dielectric constants. Therefore, the capacitors formed by the liquid, and also the capacitors formed by the walls of the quartz envelope, result in impedances which are very much lower than that of the excimer gas within the lamp. Thus, virtually all the power is delivered to and used by the lamp.
• the liquid flowing within the central enclosure of the lamp and the treated liquid on the outside of the lamp are near perfect coolants for the quartz lamp envelope. Since there are no electrodes contacting the quartz envelope, the entire surface of the envelope is liquid cooled, and that liquid can be temperature controlled to establish the most desirable temperature for the quartz envelope. This temperature control is a major factor in securing long life operation for high power excimer lamps.
• the cooling liquid in the center of the lamp when selected to be a clear liquid, it also permits ultraviolet radiation emitted from the inner envelope of the lamp to pass through the cooling clear liquid and the other side of the lamp and to still reach the treated liquid on the far side of the lamp.
• the present invention thereby not only furnishes an ultraviolet radiation generating excimer lamp with high efficiency and long life, but there is no reason to believe that there is any inherent limit on its power capability.
• FIG. 1 is a cross section view across the liquid flow path of the excimer lamp of the preferred embodiment of the invention.
• FIG. 2 is a simplified schematic diagram of the electrical and fluid flow arrangement of the invention. Detailed Description of the Invention
• FIG. 1 is a cross section view along the liquid flow path of excimer lamp 10 of the preferred embodiment of the invention in which lamp 10 is constructed from multiple concentric cylinders.
• the internal cylinder is simple hollow metal pipe 12 through which liquid flows into volume 14 which is located around pipe 12.
• Volume 14 is essentially the volume enclosed by inner quartz cylinder 16 which is also one wall of excimer gas enclosure 18.
• Cylindrical sleeve 15 is an extension of inner quartz cylinder 16, closes off the end of volume 14, and helps maintain the position of inner quartz cylinder 16.
• Outer quartz cylinder 20 forms the outer wall of excimer gas enclosure 18.
• End walls 22 and 24 join inner quartz cylinder 16 and outer quartz cylinder 20 to complete excimer gas enclosure 18 and to form an annular space which is filled with excimer gas.
• End wall 24 is also extended to close off the end of inner quartz cylinder 16, thus also closing off remote end 26 of inner volume 14.
• excimer gas filled enclosure 18 is the same as any conventional excimer lamp in that, when electrical energy is applied to the gas, micro-discharges within the gas generate ultraviolet radiation, with the wavelength of the radiation determined by the particular gas within gas enclosure 18.
• the outermost cylinder is housing 28 and is held spaced away from outer quartz cylinder by supports 30 and 32.
• Supports 30 and 32 are among the several supports spaced around outer quartz cylinder 20 to center quartz cylinders 16 and 20 within housing 28 while maintaining volume 34 between housing 28 and outer quartz cylinder 20 open for the free flow of liquid through volume 34.
• Volume 34 is closed off at one end by end plate 36 which can either be an integral part of the cylinder of housing 28 as shown, or can be a removable cap bolted on in a manner similar to end plate 38 at the electrode connection end of lamp 10.
• End plate 38 is, however, constructed of an electrically insulating material such as plastic to electrically insulate central pipe 12 from housing 28.
• End plate 38 is held tight against plate 40 of housing 28 by bolts 42 and sealed by conventional "O" ring 44.
• the high voltage connection is cable 46 attached to central pipe 12 and the return voltage and ground connection is a simple wire attached to housing 28.
• These connections can be made by any conventional means such as nuts on studs welded to the part to which the connection is made.
• Central pipe 12 serves to supply cooling water to volume 14. This cooling water flows out of pipe 12 near remote end 26 of volume 14, flows back along inner quartz cylinder 16 and sleeve 15, and leaves lamp 10 through outlet pipe 50.
• the liquid being treated enters the lamp through housing input pipe 52, flows along and around the outside of outer quartz cylinder 20 as it is irradiated by the ultraviolet radiation generated by the excimer discharge within excimer gas enclosure 18, and exits the lamp through housing outlet pipe 54.
• the lamp appears electrically as a series of five dielectrics between the electrical inputs formed by pipe 12 and housing 28.
• the first dielectric is the cooling water within volume 14
• the second dielectric is inner quartz cylinder 16
• the third dielectric is the excimer gas within volume 18
• the fourth dielectric is outer quartz cylinder 20
• the fifth is the treated liquid within volume 34.
• Housing 28 which is grounded for safety and is the return for the electrical power, acts as the other "plate" of the capacitor.
• the liquids also serve another vital purpose.
• the liquids flowing across inner quartz cylinder 16 and outer quartz cylinder 20 cool the quartz walls of excimer gas enclosure 18 so that the excimer gas transfers its heat to the quartz walls and is also prevented from becoming overheated. Cooling the excimer lamp in this manner is vital to securing high reliability and long life for lamp 10.
• FIG. 2 is a simplified schematic diagram of the electrical and fluid flow arrangement of the invention which depicts the means by which two liquid flow paths can be used in lamp 10 along with high voltage alternating current power supply 60.
• lamp 10 is fed cooling liquid through central pipe 12, but central pipe 12 is also connected to high voltage power supply 60 by cable 46.
• high voltage power supply 60 by cable 46.
• Conventional wisdom suggests that the source of the cooling liquid would have to be at the same high voltage as central pipe 12 or the power supply would be shorted out, but that is not actually the case.
• cooling liquid feed path and return path to central pipe 12 are long enough and the impedance of the cooling liquid high enough, such liquid flow paths will merely act as high impedances in parallel with the lamp, and the load they cause on the power supply will be inconsequential.
• typical tap water has a resistivity in the range of 20 to 200 micromho, and therefore has a resistance of 150 kilohm to 1.5 megohm per foot when flowing in a .45 inch diameter plastic hose. It is then only necessary to determine what leakage current would be tolerable for power supply 60 and to make feed hose 62 for pipe 12 and return hose 64 long enough to limit the leakage current to that value.
• housing 28 of lamp 10 is actually electrically grounded, so there is no concern at all about any voltage being applied to it.
• treated liquid input pipe 66 and treated liquid outlet pipe 68 can be connected to any required equipment and handle liquid of any resistivity.
• the liquid being treated has such a low conductivity that it would cause no difficulty even if it were used as the cooling liquid within the central portion of the lamp.
• the preferred embodiment of the invention has been operated with the following structure, conditions, and results.
• Housing (28) material - stainless steel length - 110 cm
• Treated liquid flow rate 150 GPM Power supply (60) - 5 Kw Excimer gas fill - Xenon/Bromine (dependent upon output wavelength desired, as well established in the literature) Ultraviolet radiation output - 300 mw per square cm.
• Bacteria kill rate - 3 log removal in 40 hours treating 600 gallons per lamp The preferred embodiment of the described ultraviolet radiation generating lamp has operated in an industrial environment purifying opaque machine cutting fluids, and has operated for more than 1000 hours at full power output without failure.
• lamp 10 need not be cylindrical, although that is simpler to construct.
• the lamp could be constructed of parallel planar sheets, in which case FIG. 1 would be a cross section view across a portion of such a configuration.
• materials other than metal may be used for central pipe 12 and housing 28, as long as the materials are electrically conductive, and walls 16 and 20 of gas volume 14 may be constructed of materials other than quartz as long as the materials are transparent to ultraviolet radiation of the wavelength generated by the lamp.
• most liquids have a dielectric constant greater than 10 and the invention is relatively independent of liquid conductivity, virtually all liquids are usable in this invention.

Landscapes

• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Physical Water Treatments (AREA)
• Discharge Lamps And Accessories Thereof (AREA)
• Paints Or Removers (AREA)

Priority Applications (10)

Applications Claiming Priority (1)

Publications (2)

Family

ID=22267132

Family Applications (1)

Country Status (9)

Cited By (6)

Families Citing this family (3)

Citations (6)

Family Cites Families (4)

• 1998
  • 1998-05-26 AU AU28061/01A patent/AU767717B2/en not_active Ceased
  • 1998-05-26 CA CA002333106A patent/CA2333106C/en not_active Expired - Fee Related
  • 1998-05-26 AT AT98924877T patent/ATE289117T1/de not_active IP Right Cessation
  • 1998-05-26 EP EP98924877A patent/EP1082753B1/en not_active Expired - Lifetime
  • 1998-05-26 DE DE69829004T patent/DE69829004T2/de not_active Expired - Lifetime
  • 1998-05-26 JP JP2000551423A patent/JP4159745B2/ja not_active Expired - Fee Related
  • 1998-05-26 DK DK98924877T patent/DK1082753T3/da active
  • 1998-05-26 WO PCT/US1998/010611 patent/WO1999062104A1/en active IP Right Grant
  • 1998-05-26 ES ES98924877T patent/ES2238761T3/es not_active Expired - Lifetime

Patent Citations (6)

Non-Patent Citations (1)

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