Abstract:
A method and apparatus for treating fluids by transmitting ultrasonic energy into the fluids to produce high intensity cavitations in the fluids as the fluids pass through the apparatus. The fluids are retained in the apparatus for a sufficient period of time to destroy contaminates in the fluids, neutralize acids or bases in the fluids and dissociate other chemical compounds.

Description:
This is a divisional of application Ser. No. 09/755,915, now U.S. Pat. No. 6,547,935, filed Jan. 6, 2001. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a method and apparatus for treating fluids and particularly for treating water to destroy contaminates in the water and sterilize the water. The apparatus and method are effective to treat the water using ultrasonic energy to dissociate compounds in the water. 
     BACKGROUND OF THE INVENTION 
     The use of ultrasound to treat various materials is well known to those skilled in the art. The general principles relating to the use of ultrasonic energy to treat various materials and its ability to result in dissociation of materials and to perform other difficult chemical reactions and the like is discussed in “The Chemical Effects of Ultrasound”, Kenneth S. Suslick, Scientific American, February 1989, pages 80–86. 
     Ultrasound has been used for a number of applications and ultrasonic transducers are well known to those skilled in the art and are commercially available. Some applications of ultrasonic techniques are shown in U.S. Pat. No. 4,164,978 issued Aug. 21, 1979 to Harold W. Scott; U.S. Pat. No. 4,169,503 issued Oct. 2, 1979 to Harold W. Scott; and U.S. Pat. No. 5,951,456 issued Sep. 14, 1999 to Harold W. Scott. These patents are hereby incorporated in their entirety by reference. 
     The availability of pure fluids is an ongoing problem in our society. In many instances it is desirable to be able to purify various gases which may contain bacterial or viral contaminates or various gaseous compound contaminates. The purification of gases, while it is frequently required, is less frequently required than the purification of liquids. Liquids, such as water, are widely used for a variety of purposes. Techniques for purifying water range from ionization techniques, to distillation and the wide variety of techniques used in municipal and other water treating plants to produce potable water. All of these techniques are relatively expensive and require extensive process equipment and process activity and expense to purify the water. Accordingly, improved and more efficient methods have long been sought for purifying fluids and particularly for purifying liquids such as water. 
     SUMMARY OF THE INVENTION 
     According to the present invention an apparatus for treating fluids is provided. The apparatus comprises a radial ultrasonic transducer having an inner surface, a central passageway having a central axis, a tube having an outer surface and centrally positioned at least partially through the central passageway, a fluid inlet to the passageway, and a fluid outlet from the passageway. 
     The present invention further comprises a method for treating a fluid wherein the method comprises passing the fluid through a passageway through a radial transducer, the passageway being formed between an inside surface of the radial transducer and the outside of a tube centrally and axially positioned at least partially through the passageway. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an apparatus for treating fluid according to the present invention; 
         FIG. 2  is an end view of a fluid passageway through the apparatus of  FIG. 1 . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the discussion of the Figures the same numbers will be used throughout to refer to the same or similar components. 
     In  FIG. 1  an apparatus  10  according to the present invention is shown. The apparatus comprises a radial transducer  12  which is connected to a power supply  14  and encloses a passageway  16  axially positioned through the radial transducer. The passageway and transducer are symmetrically positioned around an axis  24 . Axial transducer  12  is positioned for flow through passageway  16  by a pair of flanges  18  as shown. These flanges may be of any suitable construction and may be joined to transducer  12  by any suitable means. The transducer is joined to flanges  18  sealingly for the flow of fluids through a passage inlet  36  to a passage outlet  38  as shown by arrows  40 . 
     Transducer  12  can be of any suitable configuration for providing ultrasonic power into passageway  16 . For instance, prefabricated radial transducers are available at a variety of frequencies. These transducers are considered to be well known to those skilled in the art and any suitable configuration may be used so long as ultrasonic power is provided to passageway  16 . Passageway  16  is sized so that the ultrasonic energy transmitted into passageway  16  is of a wavelength equal to the diameter of passageway  16 . A variety of transducer frequencies may be used. Such frequencies may vary from about 10 to about 400 kilohertz with frequencies from 20 to about 200 kilohertz being preferred. 
     As shown in  FIG. 1  a tube  20  is positioned coaxially in axial transducer  12  and extending at least partially through passageway  16 . The ends  22  of tube  20  are desirably closed by any suitable configuration and preferably with a curved elliptical or otherwise rounded configuration to minimize the restriction of flow created by tube  20 . Tube  20 , while it may be open-ended with a gas flow through the tube or otherwise positioned in the tube, is desirably closed. The closed tube is filled with any suitable gas which will not transmit ultrasonic energy inside tube  20 , tube  20  is desirably supported coaxially with transducer  12  in passageway  16 . A plurality of supports  26  are shown supporting tube  20  in position. Adjustable fasteners  28  are positioned to sealingly engage flanges  18  to permit adjustment of tube  20  and retention of tube  20  in passageway  16 . While four support tubes have been shown in  FIG. 2  it will be understood that few more or fewer supports could be used. It is however, desirable that the supports be sufficient to maintain tube  20  centrally positioned in passageway  16 . Preferably at least three supports are used. 
     As shown in  FIG. 1  fluid flows into passageway  16  via inlet  36  and out via outlet  38  as shown by arrows  40 . 
     In operation ultrasonic energy is introduced into the fluid in passageway  16  from an inner surface  30  of passageway  16 . The ultrasonic energy, as well known to those skilled in the art, is transmitted in waveform and passes inwardly to the inner surface of tube  20 . Since tube  20  is filled with a non-transmitting fluid the wave energy is reflected back resulting in intense energy with cavitation and the like in the space defined by inside  30  of passageway  16  and an outside  32  of tube  20 . Desirably, axis  24  is positioned at ½ of 1 wavelength at the frequency of transducer  12  from inside  30  of passageway  16 . The distance between the inside  30  of passageway  16  and the outside of tube  20  is a distance which is not a multiple, i.e. multiple or fraction, of the ultrasonic wavelength at the chosen frequency which will permit a standing wave in passageway  16 . The diameter of tube  20  is sufficient to result in a space less than ½ wavelength between inside  30  of passageway  16  and outside  32  of tube  20 . This results in intense cavitation normal to the fluid flow in passageway  16 . It is important that the distance between the inside of passageway  16  and the outside of tube  20  be less than a multiple of the wavelength produced by transducer  12  which will result in a standing wave. Energy transmitted into passageway  16  is sufficient to result in severe intense cavitation in the fluid flow with the intensity increasing toward the center of the radial transducer. The sealed tube reflects the waves to the originating surface thus increasing the intensity between the outside  32  of tube  20  and inside  30 . The intensity between inside  30  of passageway  16  and outside  32  of tube  20  is many times the intensity radiating from the source. 
     This high intensity creates destructive forces that destroy bacteria or viruses by instant high temperatures of thousands of degrees Celsius and pressures of hundreds to thousands of atmospheres at heating times less than a microsecond. While Applicant does not wish to be bound by any theory it appears that in addition OH and H 2 O 2  radicals are formed which destroy bacteria and shock waves are also generated which destroy cellular structures and bacteria. Bacteria and viruses are organic compounds and are destroyed in such an environment. Further, non-elemental materials such as nitrates and other undesirable contaminates are also destroyed. For instance, nitrates may be converted into water, nitrogen and oxygen by treatment in the apparatus. Residence times in the apparatus are desirably at least about 50 milliseconds. 
     Desirably, the energy transmitted into passageway  16  at surface  30  is from about 1.6 to about 1.8 watts per square centimeter. Typically, under such conditions the energy level at outer surface  32  of inner tube  20  is about 9.5 to about 10.0 watts per square centimeter. Desirably, the average energy level in passageway  16  is greater than about 1.5 watts per square centimeter. Under these conditions substantially all non-elemental compounds in the flowing stream are dissociated. 
     The fluids treatable in the method of the present invention comprise any gas or liquid from which it is desired to remove contaminates. Water is a frequently treated liquid and is readily treated by the method of the present invention. 
     The fluids are treated by the method of the present invention by passing the fluids through the passageway and passing the ultrasonic energy into the fluid at the levels discussed above. Desirably, the fluids are retained in the passageway for a time equal to at least about 50 milliseconds. 
     EXAMPLE 
     A radial transducer having an inner diameter of 3.0625 inches and a length of 6 inches is used with a tube having an outer diameter of 0.500 inches and a length of 6 inches. The radial transducer radiates approximately 600 watts from its inner surface. At this power level 1.611 watts per square centimeter of power is delivered to the passageway  16 . A liquid flow rate of 72 hundred gallons per hour through the apparatus was used. At this flow rate the residence time of the fluid in the apparatus is about 93 milliseconds. This treatment system is effective to destroy all bacteria or viruses contained in the flowing fluid. 
     Having thus described the invention by reference to certain of its&#39; preferred embodiments it is pointed out that the embodiments described are illustrative rather than limiting in nature and that many variations and modification are possible within the scope of the present invention.