Abstract:
An ozonation system may include a mixing chamber having an inlet to a recirculation conduit within the chamber and proximate to its top, a recirculation conduit for withdrawing fluid from the mixing chamber through the inlet and conducting it to a pump, a venturi connected to the outfeed of the pump for induction of ozone into the water, an infeed for reintroducing a water-ozone mixture back into the chamber, the infeed terminating in a restricting nozzle.

Description:
BACKGROUND 
       [0001]    Treatment of a liquid with a gas, such as, for example, treating of water with ozone, is complicated by the fact that gasses do not always readily dissolve in the liquid. Mass transfer of the gas to the liquid may be enhanced by reducing the size of the bubbles of the gas in the liquid. This may result, in part, from the fact that the surface area of a bubble containing a single unit of gas is lower than is the case if the same volume of gas is contained within multiple bubbles. Of course, one difficulty presented by the presence of bubbles of a gas in a liquid is the tendency of bubbles to coalesce into fewer, larger bubbles. Larger bubbles tend to rise in the fluid and may accumulate at the top of a tank through which the fluid flows. 
         [0002]    Addition of ozone to water has been accomplished by using a venturi to entrain ozone-containing oxygen in a stream of water. To avoid accumulation of ozone in the workplace, so that workers are not exposed to the deleterious health effects of high ambient ozone levels, ozone that separates out of the water may be vented to an ozone-destruction unit. Such accumulations of ozone-bearing gas may occur, for example, in ozonation systems that allow the gas to accumulate, for example, at the top of a tank through which the gas-liquid mixture flows. 
         [0003]    Ozone may be generated by application of a high voltage electrical field to oxygen or air, such as by corona discharge in oxygen, by exposure to oxygen to ultraviolet light, and by other means known in the art. Although much of the oxygen will remain in its diatomic form, the resulting gas that is enriched in ozone by this or other processes will be generally referred to herein as ozone. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a cross-sectional view of a liquid-gas mixing system. 
           [0005]      FIG. 2  is a rear elevation of a liquid-gas mixing chamber with internal parts shown in phantom. 
           [0006]      FIG. 3  is an isometric view of a liquid-gas mixing system showing the gas line, check valve, venturi and pump, with parts broken away. 
           [0007]      FIG. 4  is an internal plan view of the rear wall of the liquid-gas mixing chamber. 
       
    
    
     DETAILED DESCRIPTION 
       [0008]    For simplicity, and although the liquid-gas mixer of the embodiments discussed below may be suitable for mixing gasses and liquids other than ozone and water, the embodiments may be discussed in connection with the mixing of ozone and water. References to ozone will be understood by those skilled in the art to include gasses such as oxygen that are enriched with ozone. Likewise, mixtures of liquids and gasses will be understood to mean both liquids, such as water, in which a gas, such as ozone, has been dissolved, as well as liquids in which gas bubbles are present. As is known in the art, gas bubbles of a sufficiently small size may be easily entrained in the flow of water and other liquids. 
         [0009]    As shown in  FIG. 1 , a water-ozone mixer system  10  according to embodiments of the present invention may include a number of different components. These may include a pump  11  and motor  12 , a recirculation conduit  13  for recirculating water from the mixing chamber  14  through the pump  11 , a venturi  15  that receives water from the pump  11  and passes it into the mixing chamber  14 . The venturi  15  has a gas inlet tube  16  through which ozone may be introduced into the water flowing through the venture  15 . The recirculation conduit  13 , pump  11  and venturi comprise a recirculation for recirculating liquid withdrawn from the mixing chamber  14  back into the mixing chamber. 
         [0010]    Referring to  FIGS. 1 ,  2  and  4 , internally of the mixing chamber  14 , in the present embodiment, the recirculation conduit  13  may turn upward within the mixing chamber  14  and may extend to a position proximate the top of the mixing chamber  14 , where it terminates in an inlet  20 . The venturi  13  is connected to an inlet pipe  21  that extends into the mixing chamber  14  and terminates in a “T” fitting  22 . The lower arm of the “T” fitting may be connected to a pipe  23  that may be connected to a water source, such as a municipal water supply. Thus the “T” fitting serves to combine the water flow from the inlet water supply flowing through the conduit  23  with the water flowing through the recirculation conduit  13 . This pipe  22  may extend through the bottom wall of the mixing chamber  14 . The upwardly-extending arm of the “T” fitting may be connected to a conduit  24  that terminates in a nozzle  25  having an outlet diameter that is less than the internal diameter of the conduit  24 . For example, in one embodiment, the recirculation conduit  13 , inlet pipe  21 , pipe  23  and conduit  24  may all be of one inch (2.45 cm) diameter, and the nozzle may be of ½ inch (1.23 cm) diameter. An outlet  26  may be provided in the bottom wall of the mixing chamber  14  to permit the outflow of ozonated water from the mixing chamber  14 . A purge valve  27  may be provided at the top of the mixing chamber  14  to allow for removal of gasses form the mixing chamber  14 . Such accumulation of gas in the mixing chamber may result when the pump  11  is turned off and water ceases to be withdrawn from the mixing chamber  14 . In such case, the bubbles of the gas will tend to rise in the mixing chamber  14  and coalesce at the top of the chamber  14 . Air or other gasses may also be purged from the system when the system is filled, for example, after initial installation or after maintenance involving disconnection of the water supply. 
         [0011]    According to an embodiment of the invention, and with reference to  FIG. 2 , the rear wall  30  of the mixing chamber  14  may include an aperture  31  for a pressure sensor  32  (see  FIG. 3 ) for monitoring, for example, the pressure or temperature within the mixing chamber  14 . A sensor  32  mounted in the aperture  31  may be used by a control system to determine when the pump  11  should be turned on and off in response to commencement and cessation of the flow of fluids from the mixing chamber through an outlet  26 . An aperture  33  may be provided in the rear wall of the mixing chamber  14  so that the recirculation conduit  13  can extend from the mouth  20  to the pump  11 . An inlet aperture  34  may be provided remote from the outlet aperture  33  so that water flowing from the venturi  15  may pass through the rear wall  30  and into the inlet pipe  21  that conducts it to the “T” fitting  22 . The outlet aperture  33  may be threaded for engagement with the pipes that form the recirculation conduit  13 . Likewise, the inlet aperture  34  in the rear wall  30  may be threaded to facilitate attachment of the inlet pipe  21  and venturi  15  on opposite sides of the rear wall  30  of the mixing chamber. 
         [0012]    Referring to  FIG. 3 , according to one embodiment, the gas inlet  16  of the venturi  15  may be connected through an elbow  40  and check and shutoff valve  41  to an ozone supply tube  42  from an ozone generator (not shown). 
         [0013]    A liquid-gas mixing system according to one embodiment may function as follows. Referring to  FIGS. 1-4 , according to an embodiment, water may be flowed into the mixing chamber  14  through the pipe  23  to fill the mixing chamber  14 , recirculation conduit  13 , pump  11 , venturi  15 , etc. The check and shutoff valve  41  restricts the water from flowing into the ozone supply tube  42 . 
         [0014]    Once the system has been filled with water, and the motor  12  has been turned on, the pump  11  begins circulating water from the mixing chamber  14  through the recirculation conduit  13 , the pump  11  and the venturi  15 , and back into the mixing chamber  14 . In one embodiment, where the piping used in the system is of one inch (2.54 cm) diameter, a two horsepower motor  12  is used to drive a pump  11  that has seven impellers. This arrangement may produce pressures on the order of 160 psi (1.1 megapascals) behind the venturi  15 . 
         [0015]    When the ozone supply is engaged, ozone travels through the ozone supply tube  42  and through the elbow  40  into the venturi  15 . The ozone is entrained in the stream of water exiting the venturi  15  and is conducted through the rear wall  30  of the mixing chamber  14  to the “T” fitting  22 , where it may mix with water at, for example, 80 psi (550 kilopascals) water supplied through the pipe  23  that may be connected to a water supply, such as a municipal water supply. Water may flow from the water supply through the pipe  23  as water is withdrawn through the outlet  26 . 
         [0016]    The mixture of water from the water supply and the water/ozone mixture from the venturi then passes through the conduit  24  and nozzle  25 . In the present embodiment, the nozzle as a ½ inch (1.27 cm) orifice. The turbulence and compression of the ozone bubbles in the water as it passes through the nozzle  25  may aid in reducing the size of the bubbles and in the dissolving of ozone in the water. In the present embodiment, the nozzle  25 , conduit  24 , “T” fitting  22  and pipe  23  extend upward at an angle within the mixing chamber  14 . Other orientations are possible. 
         [0017]    Larger bubbles tend to rise more quickly in the water in the mixing chamber  14 . The inlet  20  of the recirculating conduit  13  is accordingly placed near the top of the tank so that these bubbles in particular are drawn into the recirculation conduit and passed through the pump  11 , venturi  15  and other components of the system. The presence of bubbles in general and larger bubbles in particular in the recirculating fluid may diminish the efficiency of the pump  11 , in this embodiment, the pump  11  may be provide with a great number of impellers, such as the seven impellers mentioned above, and may be driven by a larger motor  12 , such as the aforementioned two horsepower (1.5 kilowatt) motor, than would be used for a similar system recirculating only water. Of course, bubbles passing through the impellers of a pump  11  may be broken up into smaller bubbles, and the passage through the venturi may further reduce the size of bubbles. 
         [0018]    Production of micron and submicron bubbles is desirable because the smaller the bubbles are, the greater the ratio of surface area to volume becomes. This permits more rapid and efficient mass transfer of the ozone into the water and aids in achieving a high ozone level in the water. 
         [0019]    Placement of the inlet  20  of the recirculating conduit  13  near the top of the mixing chamber  14  may reduce or eliminate any accumulation of ozone at the top of the mixing chamber  14 . In instances where such accumulation occurs, of course, it can be removed through the purge valve  27 . 
         [0020]    The nozzle  25  and venturi  15  may be of the type provided by the Mazzei Injector Corporation of Bakersfield, Calif., model number 1078 and 14, respectively. Other suitable venturis  15  and nozzles  25  may be used, and nozzles may even be fashioned from piping or nipple fittings for piping in which the end is crosscut in the shape of an “X” to a sufficient depth and width that, when the free ends are bent in toward one another and welded or otherwise joined together, an orifice of suitable size is produced. 
         [0021]    The ozone/water mixture in the mixing chamber  14  is, of course, under pressure as a result of the pressure from the water supply applied through the pipe  23 . When water is allowed to flow through the outlet  26 , it thus flows under pressure and may entrain bubbles of ozone therein. The smaller bubbles, in particular, submicron bubbles, may be more likely to be entrained in this flow out of the outlet  26  in the bottom of the mixing chamber  14  as they tend to rise more slowly. 
         [0022]    As shown and discussed above, an embodiment may use a relatively small mixing chamber in conjunction with a high level of recirculation of the ozone and water through the pump  11  and nozzle  25 , and may achieve a high level of ozonation. It is believed that various embodiments may produce micron and submicron bubbles in significant quantities. 
         [0023]    Referring to  FIGS. 5-7 , the pressure of the water supply may not always be as high as may be desired for purposes of practicing of the invention. For example, if the pump  11  and motor  12  of a system  10  are sized and designed to produce a pressure of 80 psi at the outlet of the venturi  15 , an inlet pressure of 80 psi from the water supply may be desired. Accordingly, a booster pump  45  of sufficient size and efficiency, and driven by a suitable motor  46  may be used to supply water to the mixing chamber  14  at a desired pressure. In  FIGS. 5-7 , the pumps  11 ,  45  and motors  12 ,  45  are arranged vertically and positioned proximate to the mixing chamber  14 . This may allow the system to be more compact. 
         [0024]    As with the embodiments of  FIGS. 1-4 , the water mixing system comprising the the “T” fitting  22  and the nozzle  25  may be inclined from the vertical, and the incline and positioning of these elements may be helpful in controlling the circulation of water or other liquid within the mixing chamber  14 . For example, the water mixing system may be inclined at 52 degrees from vertical. 
         [0025]    While the positioning of the outlet  26  for the gas/liquid mix may be varied, it may be positioned at the bottom or lower side, front or back wall to reduce the likelihood that the larger bubbles will be withdrawn from the chamber  14  therethrough. 
         [0026]    The ratio of fluid withdrawn from the mixing chamber to fluid recirculated through the recirculation system (comprising the conduit  13 , pump  11 , venturi  15 , inlet pipe  21  and the like members as shown in the embodiments depicted in  FIGS. 1-8 ) may be varied to affect the degree of mixing achieved. 
         [0027]    Although the present invention has been described in considerable detail with reference to certain embodiments, other embodiments are possible. Therefore, the spirit or scope of the appended claims should not be limited to the description of the embodiments contained herein.