Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
  • C01B13/10—Preparation of ozone
  • C01B13/11—Preparation of ozone by electric discharge
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L2/00—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor
  • A61L2/16—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor using chemical substances
  • A61L2/20—Gaseous substances, e.g. vapours
  • A61L2/202—Ozone
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
  • B01J19/087—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electric or magnetic energy
  • B01J19/088—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electric or magnetic energy giving rise to electric discharges
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
  • B01J2219/0803—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electric or magnetic energy
  • B01J2219/0805—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electric or magnetic energy giving rise to electric discharges
  • B01J2219/0845—Details relating to the type of discharge
  • B01J2219/0849—Corona pulse discharge

Definitions

• the present invention relates to the field of ozone generation and sterilization using ozone. More particularly, it relates to a method and apparatus for generating ozone and a method and apparatus for sterilizing articles with an ozone sterilant.
• ethylene oxide is an effective sterilant, it has three primary deficiencies.
• CFCs chlorofluorocarbons
• ethylene oxide gas is neurotoxic and has been classified by OSHA as a carcinogenic substance.
• OSHA a carcinogenic substance
• Ozone is an unstable substance which easily degrades to oxygen in the presence of heat or in water. Ozone may be generated several ways, the most common of which is by passing an oxygen-containing gas through a zone between two electrodes and generating a corona discharge between the electrodes.
• One of the electrodes is a high voltage metal electrode and the other is generally a conductor coated on a dielectric such as glass or ceramic.
• the first electrode is typically grounded at a high voltage transformer ground and the second electrode is generally electrically attached to the high voltage terminal of a high voltage transformer.
• the corona discharge splits the natural oxygen molecules into individual, highly active oxygen atoms, which immediately combine with the nearest oxygen molecule to form a trioxygen molecule, i.e., ozone.
• the reaction is extremely fast and exothermic.
• the heat of the reaction, the heat generated by the corona discharge and the heat generated within the dielectric by the passage of current contribute directly to the destruction of the newly generated ozone.
• Sterilization is enhanced by the use of humidified ozone.
• the ozone penetrates the membrane of the bacteria readily when the bacteria is coated with a water film which results from the required humidity level.
• the penetration of ozone requires less energy when it first passes through hydroxide and when it passes through the bacterial membrane when using a water film as a transfer medium.
• the water ' film transfer medium acts in the manner of an impedance transformer, whereby only a small amount of the ozone's molecular energy is required to pass through the bacterial membrane.
• Prior art ozone sterilizers which used humidified ozone as a sterilant do not consistently achieve levels of greater than 6% ozone by weight in the humidified sterilant due to heat build-up in the generator.
• a further method of increasing conversion rates is by making the generators significantly larger in size.
• larger generators require large quantities of power which not only increases costs, but more importantly, results in significantly higher quantities of ozone- destroying heat.
• a larger size generator would not be practical in many institutions requiring sterilizers. Accordingly, it would be beneficial to develop an ozone sterilizer and generator that achieve a high conversion rate without significant loss of ozone in either the generator or the humidification procedure.
• ozone sterilizers may be made more efficient and practical.
• the present invention includes an apparatus for generating ozone and a method for generating a gas containing ozone.
• the apparatus includes an ozone generator, a means for generating a corona discharge, a heat exchanger, a conduit for partially circulating a portion of the gas leaving the generation zone of the generator, and a circulation pump.
• a portion of ozone- containing gas leaving the generation zone is circulated through the heat exchanger and combined with an oxygen- containing gas forming a feed gas.
• the cool feed gas is fed to the generation zone of the generator and used in the zone to form further ozone.
• the feed gas cools the interior of the generator and increases the concentration of ozone in the gas leaving the generator.
• the ozone generator has a first electrode and a second electrode.
• the electrodes are spaced from each other and define between them the ozone generation zone.
• the inlet of the zone receives the feed gas comprising oxygen, and the outlet of the zone releases a gas mixture of the feed gas and ozone which is generated in the zone.
• a first coolant is in heat exchange relation with one surface of the first electrode.
• the heat exchanger has a gas side and a first coolant side.
• the gas side is in fluid communication with the zone.
• a second coolant in the first coolant side acts to cool the gas circulated through the gas side of the heat exchanger.
• the conduit is in fluid communication between the zone and the gas side of the heat exchanger and is configured for receiving a portion of the gas mixture which leaves the outlet of the zone.
• the pump circulates the portion of the gas mixture through the conduit, the heat exchanger and the zone.
• a feed gas comprising oxygen as described above, is introduced into the ozone generation zone in an ozone generator.
• a corona discharge is created between a first and second electrode in the generator to form ozone within the zone from the oxygen in the feed gas.
• a ⁇ urface of the first electrode is cooled with a first coolant .
• a mixture of ozone and feed gas is released from the zone, and a portion of that mixture is drawn through a heat exchanger to be cooled.
• the first portion of the mixture drawn through the heat exchanger is combined with a gas comprising oxygen to form the feed gas.
• the present invention also includes an ozone sterilizer and a method for sterilizing an article.
• the ozone sterilizer includes an ozone generator, a holding tank, a humidification chamber, a sterilization chamber, a first and a second vent for the humidification and sterilization chambers, respectively, means for controlling gas flow from the humidification chamber to the sterilization chamber, a heater and pump means.
• the ozone generator is capable of generating a gas comprising at least about 10% by weight ozone.
• the holding tank is in fluid communication with the generator and receives the gas comprising ozone from the generator.
• the holding tank also prevents backflow of moisture into the generator.
• the holding tank is also in fluid communication with the humidification chamber.
• the humidification chamber receives the gas comprising ozone from the holding tank and humidifies the gas to form a sterilant.
• the sterilant contains at least about 8% by weight ozone at a humidity of at least about 60%.
• the first vent bleeds sterilant from the humidification chamber and the second vent bleeds sterilant from the sterilization chamber.
• the vents bleed the sterilant over a first catalyst which converts ozone to oxygen.
• the sterilization chamber is in fluid communication with and receives sterilant from the humidification chamber.
• the gas flow into the sterilization chamber from the humidification chamber is controlled by the control means.
• the heat provides warm air to the sterilization chamber.
• the pump means flows air into the sterilization chamber and evacuates the chamber over a second catalyst which, like the first catalyst, converts ozone to oxygen.
• the method for sterilizing articles includes placing the article in the sterilization chamber and sealing the chamber.
• the chamber is at least partially evacuated and the sterilization cycle begins.
• a controlled flow of the sterilant gas, as described above, is introduced into the chamber until the chamber is at about ambient pressure.
• the sterilant circulates in the chamber, and continuously flows into the chamber after ambient pressure is reached, while the sterilant is simultaneously bled from the chamber over the first catalyst for a first predetermined time period.
• the first catalyst converts ozone to oxygen.
• the chamber is once again at least partially evacuated and the sterilant reintroduced as described above for a predetermined number of cycles .
• the chamber is then evacuated over a second catalyst to convert ozone to oxygen and an aeration cycle begins.
• filtered, heated air is drawn into the chamber until the chamber is at about ambient pressure. Once ambient is reached, the air continuously flows through the chamber, while being simultaneously bled over the second catalyst for a second predetermined period of time. The chamber is then unsealed and the articles removed from the chamber.
• Fig. 1 is a cross-sectional simplified representation of an ozone generator according to the invention
• FIG. 2 is an enlarged view of a bottom portion of the generator shown in Figure 1;
• Fig. 3 is a bottom sectional view of the portion of the generator as shown in Figure 2 taken along line 3-3;
• Fig. 4 is a flow diagram of an ozone sterilizer according to one embodiment of the invention.
• Fig. 4a is a schematic representation of one embodiment of a humidification chamber, within the broken line of Fig. 4;
• Fig. 4b is a schematic representation of an alternative embodiment of a humidification chamber, within the broken line of Fig. 4;
• Fig. 5 is a flow diagram of an alternative embodiment of an ozone sterilizer according to the invention.
• Fig. 6 is a schematic representation of an embodiment of the apparatus for generating ozone of the invention including the ozone generator of Fig. 1 in the broken line;
• Fig. 7 is a cross-sectional view of one generator in a multiple-generator apparatus according to an embodiment of the invention.
• Fig. 8 is a top view of a multiple-generator apparatus according to the invention.
• Fig. 9 is a partially broken away perspective view of a feed gas inlet portion of one generator in a multiple- generator apparatus according to the invention.
• Fig. 10 is a partially broken away bottom view of the feed gas inlets of a multiple-generator apparatus according to the invention
• Fig. 11 is a top sectional view of a seal used in a generator in the multiple-generator apparatus of Figure 7 taken along line 11-11;
• Fig. 12 is a cross sectional view of the seal of Fig. 11 taken along line 12-12;
• Fig. 13 is a partially broken away enlarged cross sectional view of the top portion of an outlet of a multiple-generator apparatus in accordance with the invention
• Fig. 14 is a flow diagram of the electrical and control system including the central processing unit of the invention
• Fig. 15 is a flow diagram of a method for generating ozone in accordance with an embodiment of the invention.
• Fig. 16 is a flow diagram of a method for sterilizing articles in accordance with an embodiment of the invention.
• the invention provides a highly efficient, economical ozone generator which provides a continuous flow of ozonated gas having a high percentage concentration of ozone.
• the generator is highly efficient as a result of the continuous partial recirculation of ozonated gas formed in the generator, the highly efficient cooling system and the swirling flow of feed gas within the ozone generator. As a result of the high efficiency of the generator, it is capable of being used in a small sterilizing apparatus 'of
• the sterilizer includes a humidifier which provides a humidified-ozone gas sterilant having a high percentage concentration of ozone such that fewer sterilization cycles are necessary, sterilization cycle time is shorter and bacteria kill rates are higher than prior art ozone sterilizers.
• Fig. 1 a simplified cross-sectional representation of an embodiment of an ozone generator for use in an apparatus for generating ozone in accordance with the invention.
• the generator, corona discharge generating means and conduit for gas circulation will be described followed by the remaining features of the apparatus including the heat exchanger and pump means.
• the ozone generator generally referred to as 10, includes a first, annular electrode 12 and a second, central electrode 14 spaced from the first electrode 12 defining an ozone generation zone 16 in the annular space between the electrodes 12, 14.
• the first electrode 12 is a high voltage electrode and is in the form of an outer metal tube.
• the second electrode 14 as shown in Fig.
• the first electrode and the inner tube 12, 20 are arranged concentrically with respect to each other. While the electrodes 12, 14 as shown are in the form of concentric tubes, the electrodes may also be in the form of parallel plates seated in a pressure vessel and having a cooling fluid in connection with a first electrode and a space between the electrodes. The concentric arrangement is preferred for maximizing the cooling efficiency of the apparatus and for providing a larger annular ozone generation zone 16.
• the inner tube 20 is formed of a dielectric insulating material.
• the dielectric material may be any suitable dielectric material such as, for example, any suitable glass or ceramic dielectric material having a dielectric constant of at least about 10.
• the dielectric insulating material is glass, and more preferably a lead glass.
• the dielectric constant is increased approximately 15% over most standard glass compositions. Increasing the dielectric constant decreases the amount of energy absorbed by the glass such that the glass is not so highly heated. Further, the ozone conversion is enhanced by using a material having a higher dielectric constant such as lead glass, as that material will also decrease the voltage resistance over the inner tube 20 such that more electrical energy is retained in the gas passing through the zone 16 which is subject to cooling as described below.
• the second electrode 14 as shown in Fig. 1 is in the form of a conductive coating including a conductive material, for example, a thin layer of anodized silver.
• the second electrode may be grounded by any suitable means.
• the electrodes are both connected to the terminals of a means for generating a corona discharge. Any suitable power source may be used for powering the generator which includes means for providing pulses of voltage to the electrodes.
• a transformer 26 is provided for powering the generator. While it is preferred that the electrodes be arranged as shown, it will be understood, based on this disclosure, that either electrode may be the ground electrode by reversing the polarity with respect to the transformer 26.
• the transformer 26 is preferably a step-up transformer having a DC power supply connected to a chopper for pulsing the voltage charges from about 2,000 to 40,000 volts.
• the chopper may have either a constant frequency of from about 300 to about 8,000 Hz, preferably about 350 Hz, or a variable frequency range of from about 300 to about 1,000 Hz, preferably between about 300 and 500 Hz. If a constant chopping frequency is provided, the voltage input may be controllable by an AC current from a central processing unit which is input to a DC rectifier for providing the DC supply to the chopper.
• a central processing unit can be programmed to control the ozone concentration in the gas leaving the generator between predetermined minimum and maximum values by turning the DC supply to the chopper on and off in response to the exit ozone concentration as measured by an ozone monitor having an output in connection with an input of the central processing unit.
• the chopping frequency may be proportionally varied between minimum and maximum values by an oscillator controlled by a voltage of from about 1-10 volts from the central processing unit with respect to the minimum and maximum ozone concentration levels. The frequency level proportionally increases, if the measured ozone concentration decreases. The higher the frequency, the higher the ozone produced in the generator 10.
• the generator 10 includes an outer pressure vessel housing 28.
• the housing 28 as shown in Fig. 1 is cylindrical, however, other housing configurations such as rectangular, spherical and the like may be used. The cylindrical shape is preferred for better gas flow characteristics.
• the housing 28 preferably surrounds an annular cooling jacket 30 formed between the first electrode 12 and the housing 28 as shown in Fig. 1.
• the cooling jacket 30 has an inlet 32 for receiving a first coolant in heat exchange relation with the first electrode 12 for cooling the outside surface 34 of the first electrode 12 and an outlet 36 for releasing the coolant.
• the first coolant is water, however, other coolants including ethylene or propylene glycol, brine, silicon oil, chilled gas, including chilled feed gas as described below, or other suitable coolants may be used.
• the coolant is preferably recirculated through a heat exchanger and cooled in the heat exchanger 38 for reuse, as shown in Fig. 6.
• housing 28 would function as the first electrode which, in conjunction with electrode 14, would be used for generating the corona discharge.
• metal tube 12 would be an optional feature and the cooling jacket 30 would include the generation zone 16.
• Chilled feed gas fed through inlet 32 would serve as the gas to be ozonated as well as the first coolant for cooling the first electrode.
• the gas would leave outlet 36 and could be recycled through a heat exchanger as described below.
• Such feed gas acting as the first coolant, with metal tube 12 present could also be ozonated in the cooling jacket 30 such that the cooling jacket 30 and zone 16 would both be ozone generating zones.
• the feed gas would be split and fed to both inlet 32 and inlet 44 through opening 66 as discussed below.
• the cooling jacket as shown in Fig. 1 preferably includes a plurality of heat absorbing bodies 40 which may be formed of metals such as, for example, copper, aluminum, zirconium, stainless steel or other similar metals having high heat ' conductivity and non-corrosive properties, or may be a plated metallic body, such as electroplated copper.
• the bodies may be chips or smaller fibers of metal but preferably include a mixture of both chips and fibers.
• the chips preferably have at least one flat surface, and may range in size from about 1/16 inch to about 1/4 inch in diameter as measured in the longest dimension.
• the fibers or strands are generally about 1/8 inch long and about 1/32 inch in diameter.
• the metallic bodies 40 create better flow distribution of the coolant inside the cooling jacket 30 such that contact between the coolant and the first electrode 12 is increased.
• the metallic bodies also collectively function as a heat sink, evenly distributing and absorbing heat transferred from the first electrode 12 to the coolant.
• the metallic bodies are preferably held within the cooling jacket 30 by mesh 42 such as a screen or other porous surface which covers the inlet 32 and outlet 36.
• the quantity of heat absorbing bodies within the jacket may be varied. However, it is preferred that the jacket 30 be sufficiently packed with bodies to absorb heat and evenly distribute the first coolant, but not to create a pressure drop over the cooling jacket greater than about 2 psi.
• the ozone generation zone 16 has an inlet 44 for receiving a feed gas comprising oxygen and an outlet 46 for releasing from the generator a gas mixture of the feed gas and ozone formed in the zone 16.
• the outlet 46 is in fluid communication with the first end 48 of a conduit 50 situated concentrically within the inner tube 20.
• the conduit 50 is held concentrically within the inner tube 20 by a seal 52.
• the seal 52 is configured for holding the first ends 54, 48 of the inner tube and the conduit such that they are seated in sealing relation within concentric recesses 56 within the seal.
• the seal may be formed of any ozone resistant substance such as neoprene, silicone, fluoroelastomeric rubber and the like.
• Ozone resistant O-rings are located between the seal and the ends 48, 54 to prevent leaks and to yield in response to thermal expansion of the inner tube 20 and conduit 50.
• the seal 52 includes an opening 58 aligned with the first end 48 and in fluid communication with the outlet 46.
• the first end 48 and conduit 50 are configured to receive a portion of the gas mixture from about 0% to about 30% by volume, and preferably about 5% to about 15% by volume, of the mixture leaving the outlet 46 for recirculation through a heat exchanger 38 (Fig. 6) .
• the remainder of the mixture leaves by way of an outlet 59 of the generator for use in an ozone application such as the sterilizer described in detail below.
• the first end 48 may have a diameter sized to receive a portion of the gas mixture or preferably has a variable orifice (not shown) inserted within the end for adjustably receiving a portion of the mixture.
• the second end 60 of the conduit 50 extends longitudinally and outwardly through a cylindrical bottom portion 62 of the generator.
• the inlet 44 is in fluid communication with an annular space ' 65 in the bottom portion 62 of the generator.
• the annular space 65 surrounds the conduit 50 in the bottom portion 62 of the generator as best shown in Figs. 2 and 3.
• the annular space 65 has an opening 66 extending through a side wall 68 of the bottom portion 62 of the generator.
• a pipe 70 as shown in Fig. 3 is attached over the opening 66 and forms an acute angle or with a tangent T to the side wall drawn across the opening 66.
• the angle ⁇ is from about 20° to about 45°, preferably, about 30°.
• the angle provides a generally circular swirling flow through the annular space 65.
• the swirling flow through the annular space 65 provides a helical flow upward through the zone 16 at a velocity higher than the velocity which can be achieved with a direct flow of gas through the zone 16.
• the swirling flow of gas also enters the inner tube 20. This flow pattern provides increased contact of the feed gas with the dielectric tube 20 and first electrode in comparison with straight, direct flow through the zone 16 during one pass through the zone 16.
• the swirling flow also increases contact of the feed gas with the second electrode 14 when flowing through the tube 20.
• the results of the swirling effect are cooling of the surfaces of the first electrode and tube 20 as the feed gas flows through the zone 16 and a further cooling of the second electrode 14 as the feed gas flows through the tube 20.
• a higher yield of ozone per pass through the zone 16 is achieved.
• ozone is typically best generated where the ionization energy is the most intense, i.e., very near to the facing surfaces of the first electrode 12 and dielectric tube 20, as opposed to the very center of the zone 16, increased flow of available dioxygen molecules very close to or in contact with the facing surfaces of the first electrode 12 and tube 20 increases the ozone production by increasing residence time of the feed gas in this higher ionization region.
• the annular space 65 should be configured, and the flow rate of the feed gas adjusted such that the volume of gas continuously swirling within the annular space 65 is approximately three times the amount of gas which actually passes upward through the ozone generation zone 16.
• the second end 72 of the inner tube 20 extends partially downward into the annular space 65 such that the feed gas flow in the annular space 65 splits and a portion of the feed gas passes through the inlet 74 of an annular chamber 76 defined by the conduit 50, the inner tube 20 and the seal 52.
• the feed gas which is cooled prior to entry, flows into the annular chamber 76 and the ozone generation zone 16.
• the portion of feed gas entering the annular chamber 76 is preferably about 50% to about 99% by volume of the feed gas, more preferably about 70% to about 90% by volume.
• the portion of the feed gas entering the annular chamber is chilled from the heat exchanger and swirls upward through the chamber 76, cooling the inside surface of the second electrode 14, and exits the annular chamber 76 through at least one aperture 80 in a zone of the conduit proximate the first end 48.
• the portion of the feed gas is combined with the mixture passing through the conduit and exits the generator through the second end 60 of the conduit for recirculation.
• the feed gas flowing through the zone 16 cools the facing surfaces 82, 84 of the dielectric 20 and the first electrode 12 respectively.
• a porous surface 86 such as a mesh or screen material is positioned to extend transversely across the inlet 74.
• the porous surface acts to hold heat absorbing bodies such as the chips and fibers described above within the annular chamber 76.
• the annular chamber 76 is preferably further packed with a metallic wool, such as copper or aluminum wool, which acts as a further heat sink and which breaks up the flow of the portion of the feed gas through the annular chamber 76 to increase contact of the cooling feed gas with the electrode 14.
• the cooling efficiency of the cold feed gas passing through the annular chamber 76 is greatly increased by the presence of the metallic wool and/or metallic bodies.
• a conductive strip 88 in full contact with the second electrode 14, is coiled around but spaced from the conduit 50 and helps carry the high pulse of current to the second electrode and to act as a further heat sink for the dielectric .
• the bottom 72 of glass tube 20 could alternatively extend to the bottom 62 of the generator with holes 80 being closed.
• a coolant such as a refrigerant, chilled water and the like could be circulated through annular chamber 76, with or without metallic bodies 40.
• the coolant in such a case could be the same as the first coolant used in cooling jacket 30.
• the apparatus includes a heat exchanger 38 and a pump 90. The pump is positioned for drawing the portion of the gas mixture through the end 60.
• An inlet 92 for a gas comprising oxygen to be fed into the apparatus is situated between the second end 60 and the pump 90.
• feed gas for the inlet 44 is formed.
• the gas comprising oxygen may be pure oxygen or oxygen extracted or concentrated from air by any suitable means.
• pure oxygen is used from a pressurized source such as an oxygen cylinder.
• the pump may be any suitable pump, preferably including an ozone-resistant material, which is capable of forcing the gas through the inlet 94 of a gas side 96 of the heat exchanger 38.
• the feed gas at a temperature of from about 75°F to about 100°F passes through an interior space in the heat exchanger and out through an outlet 98 of the gas side 96 at a temperature of from about 30°F to about 50°F.
• the gas side 96 is in fluid communication with the inlet 44.
• the gas side 96 is in heat exchange relation with a first coolant side 100.
• a second coolant preferably a refrigerant at a temperature of from about 25°F to about 45°F, flows through an interior space of the first coolant side 100.
• the first coolant side 100 is also in heat exchange relation with a second coolant side 102.
• the second coolant side 102 cools the first coolant circulating through the cooling jacket 30 which enters the second coolant side 102 at a temperature of about 65°F to about 90°F and exits at a temperature of from about 35°F to about 45°F.
• the second coolant side 102 is in fluid communication with the inlet 32 and outlet 36 of the cooling jacket 30.
• the second coolant flows countercurrently to the direction of flow of the feed gas and the first coolant which both flow in parallel through the heat exchanger 38 as best shown in Fig. 6 and in Fig. 15 which schematically shows the flow of gas and coolants through the generator apparatus .
• the first coolant side 100, the second coolant side 102 and the gas side 96 each preferably include a plurality of heat absorbing bodies 40 as described above in heat exchange relation with the second coolant, the first coolant and the feed gas respectively which may function collectively as a heat sink.
• the metallic bodies may be held within the sides of the heat exchanger by covering the gas inlet and outlet 94, 98 and the inlets and outlets of the first and second coolant sides with a porous covering or mesh 42 such as that described above with respect to the cooling jacket 30 and annular chamber 76.
• the heat exchanger Due to the use of the metallic bodies, the heat exchanger has a higher efficiency and requires less heat exchange surface area and/or a lower quantity of coolant flowing through the first and second cooling sides of the heat exchanger. As a result, it can be made smaller. While the metallic bodies are optional in the invention, they are preferred due to the high heat exchange efficiency provided. If the metallic bodies are used in either or both of the cooling jacket 30 or the heat exchanger 38, the water pressure may have to be increased somewhat to compensate for a slight pressure drop of about 1.5 psi over the heat exchanger and from about 0.5 psi to about 2 psi over the cooling jacket. Such a pressure increase can be easily effected by any conventional method such as, for example, adjusting the incoming water pressure, or providing a decreased entry orifice or high pressure nozzle for the water entering the heat exchanger.
• the invention further includes a multiple generator apparatus 104.
• the apparatus 104 includes an exterior vessel 106 having a first outlet 108 for releasing the gas mixture from the vessel 106.
• the outlets 59' of the individual generators 10' within the apparatus 104 are in fluid communication with the outlet 108 through passageways 110 as shown in Figs. 8 and 13.
• there are six generators 10' however, one skilled in the art will recognize from this disclosure that there may be more or less than six generators depending upon space constraints and the quantity of ozone required for a particular use.
• each annular space 65' includes an opening 64' in fluid communication with a pipe 70' for introducing feed gas.
• the pipes 70' are connected to a common inlet 112 in fluid communication with the outlet of the heat exchanger 38 for introducing feed gas as shown in
• Figs. 7 and 10 The pipes 70' are connected to each opening 64' at an angle a as described above such that the swirling flow of feed gas in each generator can be achieved.
• the diverted portion of the feed gas for cooling the inside of the dielectric tube enters the annular chamber 76' of each generator 10' through inlets 74' in the form of gaps created in a bottom seat 114 configured to fit in a sealing manner with the second end 72' of the inner tube 20' .
• Seals 52' each extend transversely across the full width of each generator 10'.
• the seals 52' are shaped to fit within a welded section of an extended outer wall 28' of the generator which is seated within the top portion of the multiple-generator apparatus as shown in Fig. 7.
• the inlet 32' and outlet 36' of the cooling jackets 30' are fed into two main conduits 118 running along the inside and through the bottom of the vessel 106, and running along the outside of the vessel 106, respectively.
• the conduits are in fluid communication with the heat exchanger 38.
• Each of the second ends 60' of the conduits 50' for gas recirculation extends through the bottom of the generator 10' and enters a lower chamber 120 of the vessel 106. Gas leaving the conduits 50' combines in the chamber 120 and exits the vessel 106 through a second central outlet 122 in fluid communication with the inlet of the gas side of the heat exchanger.
• the invention also includes a method for generating ozone as best shown in Figs. 1, 6 and 15.
• a feed gas comprising oxygen is introduced into an ozone generation zone 16 between the facing surfaces 82, 84 of the first and second electrodes 12, 14.
• a corona discharge is created between the electrodes 12, 14 forming ozone within the ozone generation zone.
• the surface 34 of the first electrode 12 opposite the zone 16 is cooled with a first coolant.
• a mixture of the ozone generated in the ozone generation zone and the feed gas is released from the zone 16.
• a portion of the feed gas is preferably directed away from zone 16 and used for cooling an inside surface 18 opposite the zone 16 of the second electrode 14. The portion directed away is described above.
• the second coolant side being as described above.
• a second coolant is passed countercurrently to the flow of feed gas through the gas side of the heat exchanger.
• the first coolant, the feed gas and the second coolant are preferably flowed through a plurality of metallic bodies, as described above, situated in each side of the heat exchanger.
• the recirculation through the heat exchanger and generation of ozone as described above are repeated continuously until ozonated gas is no longer needed.
• the quantity of ozone required in the exit gas mixture will be a function of the particular application for which the ozone gas is used. In the case of an ozone sterilization application, it will depend upon the quantity of articles to be sterilized in a particular sterilization load and the degree of contamination of the articles.
• the ozone generator of the invention is capable of generating ozone at concentrations of from about 9% to about 15% by weight, and at least about 10% by weight, at pressures of from ambient to about 250 psia, preferably from ambient to about 100 psia. More preferably, the ozone generating apparatus generates ozone at a concentration of at least about 14% at a relative humidity of at least about 60%.
• the sterilizer includes an ozone generator.
• the generator may be any generator capable of generating an ozonated gas including at least about 10% ozone.
• the generator is the same as the generator 10 or the multiple-generator apparatus 104 as described above.
• the generator 10 the generator for the sterilizer apparatus will be referred to as the generator 10; however, it will be understood from this disclosure that the generator 104, or other generators capable of generating an ozonated gas including at least about 10% by weight ozone, may be substituted for the generator 10, and are within the scope of this invention.
• the generator 10 receives feed gas from the gas side outlet of a heat exchanger.
• the heat exchanger is preferably the same as the heat exchanger 38 as described above; however, other heat exchanger configurations may be substituted without departing from the spirit of this invention.
• the oxygen-containing gas may be any oxygen- containing gas as described above, preferably pure oxygen as fed from an oxygen tank or an in-house oxygen source which is introduced into the system at a pressure of from about 2 to about 10 psig.
• the oxygen-containing gas and warm gas from the generator 10 are combined to form feed gas.
• the feed gas is forced by pump 90 into the inlet of the gas side of the heat exchanger 38, as described above, and cooled.
• Water, or other suitable coolant, which is preferably filtered, is fed into the sterilizer apparatus 11 through a main water supply line 19 at a pressure of from about 25 to about 50 psig, preferably about 35 psig and at about 65°F.
• the line 19 is split into two feed lines 21, 23.
• the water is fed into the inlet of the second coolant side of the heat exchanger 38, and cooled by a second coolant, such as a refrigerant or refrigerated water, in the first coolant side of the heat exchanger 38 to a temperature of from about 30°F to about 45°F, preferably from about 30 to about 35°F.
• a second coolant such as a refrigerant or refrigerated water
• the outlet 36 of the cooling jacket is connected to the first end of line 27a.
• the second end of line 27a is in fluid communication with the inlet of the second coolant side of the heat exchanger 38.
• a controlled amount of water substantially equal to the amount of water fed into the heat exchanger through line 21 preferably exits the heat exchanger through a main drain line 29.
• the outlet of the ozone generator 10 for releasing a gas containing ozone formed in the generator 10 is in fluid communication with a holding tank 31 for receiving the gas containing ozone.
• the gas is a mixture of feed gas and ozone leaving the ozone generator 10. The gas mixture passes into the holding tank 31 and accumulates prior to introducing the gas into the humidification chamber 33.
• valve assembly 39 is placed in line 35 and includes a pressure regulator and solenoid valve for regulating a pressure of the ozone-containing gas in line 35.
• the ozone concentration in the holding tank 31 is detected and measured by the ozone monitor.
• An outlet of the ozone monitor 37 is connected to line 41 which connects to line 43.
• Line 43 leads to a first system catalyst 47 such that excess ozone passing outward from the monitor is fed through the catalyst 47 and then to drain line 29.
• the catalyst 47 destroys the ozone in the sterilant by converting the ozone back to oxygen.
• the catalyst preferably also includes a heating element. Any catalyst capable of destroying ozone in the sterilant prior to releasing the sterilant gas into a drain may be used.
• the function of the check valve 51 is to prevent humidified sterilant from passing backwards into the generator.
• the humidified sterilant passes backward into the holding tank 31 which preferably accumulates the sterilant before it can enter the generator 10.
• the holding tank 31 is preferably equipped with an emergency drain line (not shown) connected to pass through the first system catalyst 47 and into the drain line 29.
• a valve may be included in the emergency drain line and the CPU programmed to open the valve when the generator 10 is shut off if a slight vacuum is created in the generator and holding tank 31 due to cooling of the generator. In this manner, water which collects in the holding tank 31 will not be drawn back into the generator 10 and potential leaks can be prevented.
• the humidification chamber 33 preferably includes an adjoining side-chamber, such as a sight glass (not shown) for viewing and measuring the level of water in the chamber 33 and a level controller for controlling the water level received within the chamber 33.
• the level controller may be any suitable level controller.
• the humidification chamber 33 includes a humidifier 33a in the form of a pipe having a plurality of small holes for bubbling the ozone gas mixture through water to humidify the ozonated gas forming the sterilant above the water.
• a humidifier 33a is described in U.S. Patent No. 5,069,880.
• the chamber 33 is preferably equipped with a drain line including a solenoid valve 57 in electrical communication with the CPU.
• This bubbling-type humidifier 33a is simple to make and inexpensive. It functions well in smaller sterilizers. However, if larger sterilizers of at least about 4 ft are made according to this invention, or if higher amounts of humidified ozone are required, the bubbling-type chamber is not preferred as there may be too great a loss of ozone in the water bath.
• the sterilant leaves the humidification chamber 33 having a temperature of from about 45°F to about 90°F and a concentration of ozone of from about 8% to about 15% by weight, preferably about 10% to about 15% by weight and more preferably about 12% to about 15% by weight at a relative humidity of from about 60% to about 99%, and preferably from about 80% to about 95%.
• the temperature of the ozone sterilant is preferably from about 45°F to about 80°F when it enters the sterilization chamber 75, although it may be slightly more or less depending upon the temperature of the sterilant leaving the humidification chamber and the rate at which the sterilant is introduced to the sterilization chamber through the bypass valve.
• Sterilant at temperatures of up to about 100°F provides an effective bacteria kill rate and faster kill time than colder sterilant.
• a sterilant concentration of from about 8% to about 15% ozone by weight as delivered by the invention bacterial kill times of only 25 minutes for Bacillus Suhtelis (globigii) at a D star of 4.5 minutes have been achieved.
• the sterilant is released from the humidification chamber 33 through outlet 68 as shown in Figures 4A and 4B.
• Line 68' splits to lines 43, 69 and 71.
• Line 43 is the vent line for the chamber 33.
• Line 69 is a bypass line and line 71 is a direct line, both of which are for introducing sterilant to the sterilization chamber.
• the outlet 68 of the humidification chamber 33 is in fluid communication with the inlet 73 of the sterilization chamber 75 which receives the sterilant from the humidification chamber.
• the chamber 75 preferably includes an outer wall portion enclosing an interior space 75' for receiving items to be sterilized therein.
• bypass valve 77 is closed and sterilant is continuously bled from the sterilization chamber 75 through a second vent over the first catalyst 47 which is in fluid communication with the outlet 83 of the sterilization chamber 75.
• the second vent for the sterilant may include passing the sterilant outward through line 85 and solenoid valve 87.
• line 85 is connected to line 43.
• the sterilant is circulated throughout the chamber by an internal fan, blower or similar means for gas circulation.
• the sterilization chamber is configured such that the circulation means is an internal fan provided within a back wall portion of the chamber.
• the temperature and pressure in the sterilization chamber 75 are continuously monitored during the operation of the sterilizer by temperature and pressure sensors located within the chamber. The sensors are in electrical communication with pressure and temperature detectors powered by the main electrical supply and which supply an electrical signal to the CPU.
• water from the evacuated sterilant gas collects in a collector at the bottom of the pump.
• the water and oil collected in the base of the pump leave the pump 91 and pass through an oil separator 95.
• the oil separator includes a hollow chamber and drip line. Water collects and separates from the oil and may be emptied into the main drain line 29 through line 93' .
• the oil phase can be recirculated as pump oil after separation. Alternatively, the oil and water collected at the base of the pump may be heated to remove water from the oil phase.
• the pump 91 operates to draw warm, filtered air through the chamber 75 to dry the sterilized articles and to ensure that all sterilant is removed from the chamber 75 prior to opening the chamber to remove the articles.
• Outside air which is passed through an air filter 97, such as, for example, a HEPA ® biomedical air filter, is drawn through a heater 99 and warmed to a temperature of about 110°F.
• the warm air flows through solenoid valve 101, line 71 and valve 79 into the chamber 75 where it is circulated by a fan, blower, or the like, as described above.
• the vacuum pump 91' i ⁇ situated such that it functions to force outside air through the sterilizer at the end of the sterilization cycle instead of drawing the air through the sterilizer as in the apparatus of Figure 4.
• the pump 91' further functions to evacuate the sterilization chamber 75 over the second system catalyst 89, through line 93' and an oil filter 103, which removes any particles of pump oil or water which may have been introduced into the filtered air by the pump.
• the oil filter may be any suitable oil filter, or an oil separator as described above. After filtration, the evacuated sterilant, or other gas, may pass directly into the drain line 29 through line 105.
• the kill time (even when doubled for safety and regulatory reasons) is extremely short in comparison with prior art ethylene oxide sterilizers.
• the sterilizer provided a quick aeration time on the average of about 10 min. A full sterilization cycle was complete in an average time of under 2 hours. The kill rate for all samples was 100%.

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• 1997
  • 1997-03-17 AU AU23185/97A patent/AU2318597A/en not_active Abandoned
  • 1997-03-17 EP EP97915869A patent/EP0888135A4/en not_active Withdrawn
  • 1997-03-17 JP JP9533504A patent/JP2000507853A/ja not_active Withdrawn
  • 1997-03-17 WO PCT/US1997/003471 patent/WO1997034643A1/en not_active Application Discontinuation

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