Abstract:
The present invention provides an apparatus for dissolving a gas in a liquid, the apparatus comprising (a) a closed container containing a liquid at a predetermined level, (b) a contactor module at least partially immersed in the liquid having (1) a gas supply channel to the bore side of the fibers, (2) a liquid supply channel to the shell side of the fibers, and (3) an exit port for transport of a gas-containing liquid, and (c) the remaining space in the closed container being occupied by a pressurized gas. The liquid prepared in the apparatus of the present invention containing a dissolved gas, is used to prepare beverages, such as coffee, tea, soda, chocolate and the like, whether hot or cold.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the priority of United Kingdom Application 0312421.1 filed 30 May 2003 and United Kingdom Application 0326296.1 filed 12 Nov. 2003 under 35 U.S.C. § 119.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH  
       [0002]     Not Applicable.  
       BACKGROUND OF THE INVENTION  
       [0003]     Many beverages require certain levels of gases to be dissolved in at least one of the constituent liquids prior to dispense in order to achieve the desired taste and or presentation effects in the final beverage. Examples of such beverages include carbonated juices, sodas, and the like where carbon dioxide is either pre-dissolved at elevated pressure in water which is added to a concentrate or is pre-dissolved at elevated pressure in the mixture of water plus concentrate. When dispensed correctly a substantial portion of the carbon dioxide remains in solution in the glass or cup, producing the familiar taste effect when the beverage is consumed. Other examples of beverages include chilled or hot coffees, and chocolates where either nitrogen or air gases are pre-dissolved at elevated pressure in water or in premixed water with concentrate. When these liquids are dispensed correctly, the pre-dissolved gases are substantially removed from solutions on passage of the liquid thru the dispense tap to form a large quantity of small bubbles which float and settle at the top of the beverage to produce an appealing presentation of the drink in the glass or cup.  
         [0004]     Still further examples include beverages based on dairy products, which contain pre-dissolved nitrous oxide and water-based beverages containing pre dissolved oxygen.  
         [0005]     The use of gas/liquid contactor modules containing non-flooding gas-permeable hollow fibers and associated control schemes for controlling dissolved gases in liquids have been described in U.S. Pat. No. 5,565,149 (herein incorporated by reference). Technology disclosed in U.S. Pat. No. 5,565,149 has been commercialized in a range of Cellarstream® dispense systems which are manufactured and marketed by Headmaster, Ltd., Bramshill, United Kingdom and Permea a division of Air Products and Chemicals, Inc. Allentown, Pa., U.S.A.  
         [0006]     The amount of a gas which can be dissolved in a liquid at a selected temperature, is proportional to the applied absolute pressure of the gas.  
         [0007]     Hitherto, beverage dispense systems utilizing the gas/liquid contactors have consisted of the two shell ports of the contactor module being connected respectively to a pressurized liquid source and to a dispense tap, whereas the contactor module gas port is connected to a pressurized gas source.  
         [0008]     In order to maintain efficient operation of such systems, additional controls such as those described in U.S. Pat. No. 5,565,149 are necessary to maintain the pressure of gas applied to the contactor fibers at substantially the same pressure as that of the liquid supply in the contactor module. These conventional systems have drawbacks for certain applications.  
         [0009]     Where it is desired to dissolve a large amount of a weakly soluble gas, e.g., nitrogen, for a beverage such as a chilled draft coffee beverage, the contactor module must be built to operate safely at correspondingly high pressures on both the liquid and gas sides of the system. At a working temperature of 3° C. contactor modules rated for operation at a maximum pressure of 4 bar gauge will deliver a maximum level of dissolved nitrogen of approximately 110 ml per liter of water. This pre-dissolved gas level directly determines the size of “head” on the dispensed drink, and it is generally accepted that operation of contactor modules at high pressure to deliver high levels of dissolved gas will be desirable if that could be achieved economically.  
         [0010]     Additional drawbacks of relatively high costs and complexity of installations present barriers to wide exploitation of such contactor module systems where compared to some retail outlets, a lower frequency of usage would be the norm, for example, in the domestic market sector.  
         [0011]     The present invention provides a novel apparatus for utilizing hollow fiber gas/liquid contactor modules at much higher liquid and gas pressures than has hitherto been practical or economical. The apparatus of the present invention is thus able to deliver liquids containing significantly higher concentrations of dissolved gas than is possible with a conventional apparatus. A further advantage of the apparatus of the present invention arises from the elimination of the need for controls to balance liquid and gas pressures within the contactor module thus reducing both the costs and the complexity of most installations. A still further advantage arising from the present invention is that when the apparatus is used to dissolve a highly-soluble gas, such as carbon dioxide, the practical performance of the contactor module in typical dispense operation is significantly greater than that of the contactor module of comparable geometry operated in the conventional manner.  
         [0012]     The present invention relates to an apparatus and a method for utilizing the apparatus for applying gas/liquid contactor modules containing hollow fibers for dissolving gases in liquids prior to dispense of a liquid as a beverage.  
       SUMMARY OF THE INVENTION  
       [0013]     The present invention provides an apparatus for preparation and dispense of a liquid beverage which comprises a closed container. The closed container contains liquid at a predetermined level within the container. In addition the container contains a gas/liquid contactor module at least partially immersed in the liquid, the module having (a) a gas supply channel to the bore side of the fibers, (b) a liquid supply channel to the shell side of the fibers, and (c) an exit port for transport of a gas-containing liquid. Within the closed container, the remaining space is occupied by a pressurized gas. Generally, the closed container additionally has an exit port for dispense of a gas-containing liquid from inside the container to a dispense mechanism for preparation of a beverage. Further, the closed container has a pressurized gas inlet wherein gas is supplied to the remaining space in the closed container and is maintained at an elevated pressure even during dispense of liquid from the container.  
         [0014]     The liquid within the container may be a beverage such as coffee, tea, soda, and the like or a concentrate suitable for making a beverage by the addition of another liquid, or water.  
         [0015]     The pressurized gas within the container is typically a gas dissolved in a beverage such as carbon-dioxide, nitrogen, nitrous oxide, oxygen, air and the like.  
         [0016]     Typically the contactor module contains a bundle of hollow fiber membranes, which fibers are gas permeable and liquid impermeable. The contactor module has a liquid entry port which allows liquid to access the exterior of the hollow fiber membranes within the module. The module also contains a gas entry port which allows gas to fill the interior of the hollow fiber membranes in the module. Because the gas is at an elevated pressure while in the presence of the liquid, the liquid dissolves a relatively high portion of the gas, thus providing a liquid containing dissolved gas therein. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0017]     In the accompanying drawings which form part of the specification:  
         [0018]      FIG. 1  depicts a cross-sectional view of one embodiment of the present invention;  
         [0019]      FIG. 2  depicts a cross-sectional view of another embodiment of the present invention; and  
         [0020]      FIG. 3  depicts a cross-sectional view of a further embodiment of the present invention. 
     
    
       [0021]     Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     The following detailed description illustrates the invention by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the invention, describes several embodiments, adaptations, variations, alternatives, and uses of the invention, including what is presently believed to be the best mode of carrying out the invention.  
         [0023]      FIG. 1  depicts a cross-sectional view of one embodiment of the present invention. An apparatus  10  having a closed container  14  is provided which contains a liquid  16  and a contactor module  24 . The module  24  has a shell  22  surrounding a bundle of hollow fibers  12 . The module  24  has a space  20  surrounding the bundle of hollow fibers  12  wherein a liquid resides. The contactor module  24  has an end cap  30  in the lower area which seals the ends of the fibers in the fiber bundle  12  thereby preventing entry of liquid to the interior of the fibers. There is an upper seal  26  which seals the regions around the fibers, however, the upper surface of the seal  26  provides a fiber face  28  which is open to the atmosphere allowing the interior of the fibers  12  to receive gas.  
         [0024]     The upper portion of the closed container  14  is provided with a cap  42  which covers the open face of the hollow fibers  28  and provides a gas channel  32 , which supplies pressurized gas to the open face  28  of the bundle of fibers  12 . The cap  42  is sealed between the contactor shell  22  and the inside of the cap  42  with ring seals  38  and  40 . An outlet port  34  is provided to allow liquid, surrounding the fiber bundle  12  in the space  20 , to exit from the contactor module  24 . The interior of the closed container  14  has a predetermined level of a liquid  16  and in the remaining portion of the interior of the closed container  14  there is a pressurized gas  18  which remains under pressure.  
         [0025]     In the apparatus  10 , the contactor module  24  is provided with a lower port  36  to receive liquid from the liquid  16  in the closed container  14 . The liquid  16  enters the contactor at the port  36  and fills the space  20  between the fiber bundle  12  and the contactor exterior shell  22 . In the use of the apparatus  10 , when a gas-containing liquid is desired, the gas-containing liquid is removed through an upper port  34 . The cap  42  is provided with an additional ring seal  44  and a pressure seal  46 , to prevent the pressurized gas from escaping from the closed container  14 . A port  48  is connected to a pressurized gas and hence allows gas to enter the closed container  14  at the port  48  to provide the necessary pressurized gas in the space  18  in the apparatus.  
         [0026]      FIG. 2  depicts a cross-sectional view of a further embodiment of the present invention. An apparatus  50  has a gas inlet port  63  which is machined within the cap  42  and provides pressurized gas to the gas channel  32 . A 3-port, 2-position valve  62  is optionally included in the gas feed line upstream of the gas port  63 . A gas pressure regulator  64  is placed between the valve  62  and the gas source  66 . The gas source  66  provides pressurized gas at a predetermined pressure to fill the space  18 . In the present embodiment, the level of the liquid  16  can be maintained automatically between two selected levels, an upper level and a lower level. When sufficient dispense of the gas-containing liquid through the port  34  causes the liquid level to fall below the lower selected level, a controller  60  operates a valve  62 , to vent pressurized gas from the closed container  14 . The controller  60  also operates a valve  56  which allows liquid from the liquid source  58  to be added through a port  54  until the higher selected liquid level is reached in the closed container  14 . The controller  60  then operates the valve  62  and closes the liquid entry valve  56  to allow gas pressure to be reapplied to the space  18  in the closed container  14 .  
         [0027]     The closed container  14  is further provided with a controller  60  containing a sensor means  52 , which sensor means  52  detects when the liquid level falls below the lower preselected level and when the liquid level reaches the upper preselected liquid level. Thus the controller  60  signals the liquid controlling valve  56  to open and close respectively when the liquid  16  reaches the lower level and again upon refilling when the liquid reaches the upper preselected level.  
         [0028]     An additional advantage of this embodiment of the invention is that the water level can be maintained automatically between the preselected upper and lower levels without needing to depressurize the closed container  14 , before commencing each refilling operation. If the pressure of the water source  58  is above the operating pressure of the closed container  14 , the valve  62  may be omitted in this mode of operation.  
         [0029]     This embodiment of the invention has the further advantage that there is no waste of pressurized gas involved in the operation. This is because all of the water added to the closed container  14  during each refilling operation must first past through the contactor module  24 . This provides a high efficiency in the dissolving of the pressurized gas into the liquid because all of the liquid leaving the system has passed twice through the contactor module  24 . As will be shown in subsequent examples, it has been found that the efficiency for the dissolving of gas into a liquid is significantly higher than the efficiency of a single comparable contactor module operated in a conventional manner at the same pressure, temperature, and dispense flow rate.  
         [0030]      FIG. 3  depicts a cross-sectional view of an apparatus  70  in a still further embodiment of the present invention. In this embodiment, the contact module  24  rests on the bottom of the closed container  14 . In addition, the contactor module may be completely immersed in the liquid  16 . A tube  68  is connected to the cap  42  of the contactor module  24 . The open end of the tube  68  is secured above the liquid level, and generally it will have its open end located just below the gas connection port  49  so as to receive and transport pressurized gas to the open fiber face  28  of the contactor module  24 . The liquid exit port  34 , in the form of a tube, is connected to a liquid outlet connection  67  which leads to the dispense mechanism for the gas-containing liquid to form a beverage. A separate resealable connection  65  is provided to allow refilling of the closed container  14  with liquid. Alternatively, the scheme described above in the second embodiment in  FIG. 2 , may be used for controlling the liquid levels in the closed container  14 .  
       EXAMPLE 1  
       [0031]     A contactor module was assembled within a 10 liter keg according to the embodiment shown in  FIG. 3 . The keg was filled with water at 12° C., sealed, and pressurized with nitrogen at 4 bar gauge pressure.  
         [0032]     The keg outlet was connected to a dispense tap fitted with a “creamer disc” with 5 holes each of 0.5 mm diameter.  
         [0033]     185 ml of liquid was dispensed via the tap into a parallel-sided glass containing 15 ml of liquid coffee concentrate.  
         [0034]     The liquid level in the glass was 100 mm for 200 ml liquid content.  
         [0035]     After settling, a thick foam (of about 10 mm in thickness) made of tight and stable small bubbles had formed on the beverage. Allowing for the normal liquid content in the foam, this head corresponds to a dissolved nitrogen level of approximately 90 ml of nitrogen per liter of liquid.  
       EXAMPLE 2  
       [0036]     Using the same arrangement as in Example 1, the keg was pressurized with nitrogen at 7 bar gauge at the same temperature.  
         [0037]     185 ml was dispensed from the same tap into the same parallel-sided glass containing 15 ml of liquid coffee concentrate.  
         [0038]     After settling, 17 mm of thick foam made of tight and stable small bubbles had formed on the beverage. Allowing for the normal liquid content in the foam, this head corresponds to a dissolved nitrogen level of approximately 145 ml of nitrogen per liter of liquid.  
       EXAMPLE 3  
       [0039]     A contactor module, 51 mm internal diameter and containing an active fiber area of 1.2 square meters, was fitted to a 10.5 liter keg according to the embodiment shown in  FIG. 2 . The keg was insulated and fitted with a liquid level sensor, a liquid level controller and a solenoid valve in line from a source of vacuum-degassed water according to the arrangement shown in  FIG. 2 .  
         [0040]     The level sensor was a type which only detected a single level, set at 9.5 liters. The controller was provided with a switch which simulated the action of a low-level detection and thus allowed the user to determine when to start re-filling the keg. The space in the keg was initially filled with carbon dioxide gas supplied from a cylinder via a non-relieving pressure regulator set at a delivery pressure of 3 bar. A pressure gauge was fitted in the feed gas line downstream of this regulator.  
         [0041]     The water source was at a pressure of 4.2 bar and at a temperature of 13.3° C. The keg started filling with water when electrical power was applied to the controller, and continued filling until the upper level set by the level sensor was reached. During this time the reading on the pressure gauge in the feed gas line remained at 3 bar.  
         [0042]     The carbonation levels of a sequence of five dispensed volumes of 200 ml each dispensed at a flow rate of 2.0 liters per minute, were measured with a carbonation analyzer of a type used for testing sodas. The measured carbonation levels remained constant at 4.22 volumes of carbon dioxide per volume of liquid for all samples.  
         [0043]     The controller switch was operated and the keg re-filled again. The feed gas pressure gauge remained at 3 bar, and a further sequence of five 200 ml volumes were dispensed at a flow rate of 1 liter per minute. The measured carbonation levels remained constant at 4.22 volumes of carbon dioxide per volume of liquid.  
         [0044]     In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results are obtained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.