METHOD AND APPARATUS FOR DIFFUSING OZONE GAS INTO LIQUID

Abstract

An ozone diffuser includes an outer tube having a tubular porous membrane disposed coaxially therein. An annular space is defined between the inner surface of the tubular member and the outer surface of the membrane into which ozone gas is applied. Water is caused to flow through the interior of the membrane in such a manner as to form a vortex which creates a negative pressure at the inner surface of the membrane. The pressure difference between the annular space and the interior of the membrane causes ozone gas to be sucked through the membrane and become diffused into the water. The pressure difference results in a high concentration of ozone in the water. The vortex also produces a shearing effect which breaks up the ozone bubbles and increases the diffusion efficiency.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to the art of cleaning and sterilization, and more specifically to a method and apparatus for diffusing ozone gas into a liquid which is used for these purposes.

[0003] 2. Description of the Related Art

[0004] The use of ozone for cleaning or sanitizing objects is known in the art per se. Ozone is vastly superior to chlorine and other commonly used sanitizing agents which are toxic and must be removed after use. Ozone is also a much stronger sanitizing agent than such other fluids.

[0005] U.S. Pat. No. 4,898,679, entitled “METHOD AND APPARATUS FOR OBTAINING OZONE SATURATED WATER”, issued Feb. 6, 1990 to Seymour Siegel et al, teaches how to use ozone saturated water to perform clean-in-place cleaning of pipes in a processing plant. Other uses include sanitization of fruit and other agricultural products.

[0006] Water is a desirable vehicle for carrying ozone gas to and from the object or objects that are to be cleaned or sanitized. Various methods of diffusing ozone gas into water have been proposed in the art. However, prior art methods are generally inefficient and result in a relatively low concentration of diffused ozone. The method disclosed in the above referenced patent to Siegel, for example, involves bubbling the ozone gas into the water using a ceramic diffuser.

[0007] The effectiveness of ozone saturated water is limited by the concentration of ozone gas which can be diffused into the water. As such, there exists a need in the art for a method and apparatus for diffusing ozone gas into a liquid which produces a higher concentration of ozone than has been possible heretofore.

SUMMARY OF THE INVENTION

[0008] The above described need which has existed heretofore in the art is fulfilled by an ozone diffuser according to the present invention which includes an outer tube having a tubular porous membrane disposed coaxially therein. An annular space is defined between the inner surface of the tubular member and the outer surface of the membrane into which ozone gas is applied.

[0009] Water is caused to flow through the interior of the membrane in such a manner as to form a vortex which creates a negative pressure at the inner surface of the membrane. The pressure difference between the annular space and the interior of the membrane causes ozone gas to be sucked through the membrane and become diffused into the water.

[0010] The pressure difference results in a high concentration of ozone in the water. The vortex also produces a shearing effect which breaks up the ozone bubbles and increases the diffusion efficiency.

[0011] These and other features and advantages of the present invention will be apparent to those skilled in the art from the following detailed description, taken together with the accompanying drawings, in which like reference numerals refer to like parts.

DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a simplified diagram illustrating a cleaning or sanitizing system including an ozone diffuser according to the present invention;

[0013] FIG. 2 is a side view of the present ozone diffuser;

[0014] FIG. 3 is a vertical sectional view of the diffuser taken on a line III-III of FIG. 2;

[0015] FIG. 4 is a horizontal sectional view illustrating a water inlet of the diffuser taken on a line IV-IV of FIG. 2; and

[0016] FIG. 5 is a horizontal sectional view illustrating an ozone inlet of the diffuser taken on a line V-V of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

[0017] FIG. 1 illustrates a cleaning or sanitizing system 10 including an ozone diffuser 12 according to the present invention. In the illustrated configuration, the system 10 includes a tank 14 which contains objects (not shown), e.g. fruit or other agricultural products, which are to be cleaned or sanitized.

[0018] Water having ozone gas diffused therein is circulated through the tank 14 in contact with the objects to be cleaned or sanitized. More specifically, a pump 16 draws water from the lower end of the tank 14 through a conduit 18 and applies this water to a water inlet 20 of the diffuser 12 through a conduit 22 as indicated by arrows. Ozone gas from an ozone source 24 is applied to one or more ozone gas inlets 26 (only one inlet is shown) of the diffuser 12 through a conduit 28. Water having ozone gas diffused therein is applied through a water outlet 30 and a conduit 32 into the upper end of the water tank 14 through which it circulates to clean or sanitize the objects therein.

[0019] The ozone source 24 per se is not the particular subject matter of the invention and will not be described in detail. The source 24 can be constructed to convert oxygen gas into ozone gas using corona discharge in a known manner.

[0020] The present ozone diffuser 12 is illustrated in FIGS. 2 to 5, and includes an outer tubular member 40 which has an upper section 42 and a lower section 44 which is fixed to the upper section 42 by a flange and bolt arrangement 46. The upper member 40 has a stepped inner surface including a large diameter surface 46 which terminates at its upper end in a small diameter surface 48. The lower member 44 has an inner surface 50 with the same diameter as the surface 48.

[0021] A porous membrane 52 is coaxially mounted inside the member 40 and has an outer diameter which is substantially the same as the inner diameters of the surfaces 48 and 50. The membrane 52 is held at its upper end within the surface 48, and at its lower end within the surface 50. A first passageway 54 or annular space is defined between the inner surface 46 of the tubular member 40 and a first or outer surface 55 of the membrane 52. The upper end portion of the tubular member 40 and the interior of the membrane 52 as defined by a second surface 57 thereof constitutes a second passageway 56.

[0022] The diffuser 12 is oriented substantially vertically, with the longitudinal axis of the second passageway 56 also being oriented vertically. The water inlet 20 opens into the upper end portion of the passageway 56, whereas the water outlet 30 leads out of the lower end portion of the passageway 56. The ozone inlet 28 opens into, preferably, the central portion of the first passageway 54 and fills the passageway 54 with ozone gas at a positive pressure. The passageway 54 does not have an outlet.

[0023] In operation, water is applied through the inlet 20 into the second passageway 56. The tubular member 40 and membrane 52 are configured such that the water flows downwardly through the passageway 56 in the form of a helical vortex as indicated by arrows 58. The vortex creates a negative pressure on the inner surface of the membrane 52 due to the Bernoulli effect as is known in the art per se. The pressure difference between the opposite surfaces of the membrane 52 causes ozone gas to be sucked through the porous membrane 52 and become diffused into the vortex of water flowing downwardly through the passageway 56.

[0024] The membrane 52 preferably has a porosity of 50 to 60 microns. A membrane suitable for practicing the present invention is commercially available from Pore Technologies of Framinghan, Mass. The configuration which creates the vortex is preferably designed such that the pressure difference between the opposite surfaces of the membrane 52 which causes the ozone gas to be sucked therethrough is on the order of approximately 5 to 20 psig, most preferably approximately 15 psig.

[0025] A preferred arrangement for creating the vortex is illustrated in FIG. 4. The longitudinal axis of the second passageway 56 is designated as 60, and extends perpendicular to the plane of the drawing. The water inlet 20 is oriented substantially perpendicular to the axis 60, and is radially offset therefrom. Thus, water flowing through the inlet 20 impinges on the inner surface of the passageway 56 and is forced to spin counterclockwise as indicated by arrows in FIG. 4. The water is caused to flow downwardly through the passageway 56 by gravity. As such, the combination of the circular flow caused by the offset of the inlet 20 and the downward flow caused by gravity creates the desired helical vortex.

[0026] The vortex also has a shearing effect on the ozone bubbles emerging from the inner surface of the membrane 52 which have a diameter of 50 to 60 microns. This shearing effect breaks up and scatters the bubbles into smaller bubbles having a diameter of 30 to 40 microns, and yet further increases the diffusion efficiency.

[0027] It has been determined that the present ozone diffuser 12 is substantially more efficient than prior art diffusers, in that it is capable of diffusing ozone into water with as much as 90% of the theoretically maximum concentration of 6.75 milligrams per liter at ambient pressure and temperature.

[0028] Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof.

[0029] For example, although the invention has been described as being applied to diffusing ozone gas into water, the scope of the invention is not so limited and encompasses any application in which one fluid is to be diffused into another fluid. One fluid can be a gas and the other fluid can be a liquid as described above. Alternatively, both fluids can be gasses or both fluids can be liquids. The porosity of the membrane and the pressure difference thereacross created by the vortex can be determined mathematically and/or empirically in accordance with a particular application and the fluids which are to be mixed.

[0030] Various alternatives to the particular configuration which is explicitly described and illustrated are also encompassed within the scope of the invention. For example, although a preferred embodiment of the invention is illustrated in which ozone is applied to the outer (annular) passageway 54 and water is applied to the inner passageway 56, it is within the scope of the invention to reverse this relationship.

[0031] Although not explicitly illustrated, in this particular embodiment ozone would be applied to the inner passageway and water would be applied to the outer (annular) passageway. A vortex created by water flowing downwardly in the passageway would suck ozone from the inner passageway through the membrane into the water flow in the outer passageway due to the pressure drop created by the vortex in a manner essentially similar to that described above. In this modification the lower end of the inner passageway would preferably be sealed such that the inner passageway would not have an outlet, and that an outlet be provided at the lower end of the outer passageway.

[0032] It is further within the scope of the invention to provide other vortex creating water or other fluid flow paths and porous membrane arrangements which cause ozone or another fluid to be sucked into the water or other fluid through a membrane. Such paths can be, for example, circular, spiral, and/or include multiple sections which are similar or different. Any configuration which produces the effect of diffusing one fluid into another fluid due to a pressure difference created on the opposite sides of a porous membrane by a vortex is considered to be an equivalent of the particular configuration which is described and illustrated.

Claims

1. An apparatus for diffusing a first fluid into a second fluid, comprising:

a membrane having a porosity which is sufficient to allow the first fluid to pass therethrough;

a first passageway configured to apply the first fluid to a first surface of the membrane; and

a second passageway configured to apply the second fluid to a second surface of the membrane which is opposite to the first surface thereof such that the second fluid forms a vortex with sufficiently low pressure to cause the first fluid to move from the first passageway through the membrane into the second passageway and become diffused into the second fluid.

2. An apparatus as in

claim 1, in which the first fluid is a gas and the second fluid is a liquid.

3. An apparatus as in

claim 2, in which the first fluid comprises ozone gas.

4. An apparatus as in

claim 3, in which the second fluid comprises water.

5. An apparatus as in

claim 1, comprising an outer tubular member, in which:

the membrane is tubular and is disposed coaxially inside the outer tubular member;

the first passageway comprises an annular space between an inner surface of the tubular member and an outer surface of the membrane, the outer surface of the membrane constituting said first surface thereof;

the first passageway has an inlet;

the membrane has an inner surface which constitutes said second surface thereof and defines the second passageway; and

the second passageway has an inlet and an outlet.

6. An apparatus as in

claim 5, in which:

the inlet of the second passageway is oriented at substantially a right angle to a longitudinal axis of the second passageway and is radially offset from the longitudinal axis, thereby causing the second fluid to form said vortex in the second passageway.

7. An apparatus as in

claim 6, in which the inlet and outlet of the second passageway are provided at substantially opposite ends thereof.

8. An apparatus as in

claim 7, in which the apparatus is disposed such that the axis of the second passageway is oriented substantially vertically; and

the inlet of the second passageway is disposed above the outlet thereof.

9. An apparatus as in

claim 1, in which:

the first fluid comprises ozone gas; and

the membrane has a porosity of approximately 50 to 60 microns.

10. An apparatus as in

claim 1, in which the first and second passageways are configured such that a pressure difference between the first and second surfaces of the membrane is approximately 5 to 20 psig.

11. An apparatus as in

claim 1, in which the second passageway is configured such that said vortex at least partially shears the first fluid at the second surface of the membrane.

12. A method for diffusing a first fluid into a second fluid, comprising the steps of:

(a) providing a membrane having a porosity which is sufficient to allow the first fluid to pass therethrough;

(b) applying the first fluid to a first surface of the membrane; and

(c) applying the second fluid to a second surface of the membrane which is opposite to the first surface thereof in such a manner that the second fluid forms a vortex with sufficiently low pressure to cause the first fluid to move through the membrane and become diffused into the second fluid.

13. A method as in

claim 12, in which the first fluid is a gas and the second fluid is a liquid.

14. A method as in

claim 13, in which the first fluid comprises ozone gas.

15. A method as in

claim 14, in which the second fluid comprises water.

16. A method as in

claim 12, in which:

step (a) comprises providing the membrane in the shape of a tube;

step (b) comprises applying the first fluid to an outer surface of the membrane which constitutes said first surface thereof; and

step (c) comprises applying the second fluid to an interior of the membrane which constitutes said second surface thereof.

17. A method as in

claim 16, in which:

the membrane is oriented such that a longitudinal axis thereof is oriented substantially vertically; and

the second fluid is applied into the interior of the membrane at substantially a right angle to the longitudinal axis and is radially offset from the longitudinal axis to create said vortex.

18. A method as in

claim 12, in which:

the first fluid comprises ozone gas; and

step (a) comprises providing the membrane with a porosity of approximately 50 to 60 microns.

19. A method as in

claim 12, in which steps (b) and (c) in combination comprise creating a pressure difference between the first and second surfaces of the membrane of approximately 5 to 20 psig.

20. A method as in

claim 12, in which steps (a), (b) and (c) in combination comprise creating said vortex such that it at least partially shears the first fluid at the second surface of the membrane.