Abstract:
A gas recovery system for a beverage dispensing system is provided. The system includes a mechanism for drawing gas from an at least partially used beverage container, a compressor downstream of the at least partially used beverage container, a gas separator downstream of the compressor, and a gas storage vessel downstream of the gas separator. The gas recovery system is configured to draw gas from the at least partially used beverage container, to separate the gas into component gases by passing the gas through the gas separator, and to selectively direct at least one of the separated component gases to the gas storage vessel.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application is a U.S. nationalization under 35 U.S.C. §371 of International Application No. PCT/GB2009/050031, filed Jan. 16, 2009, which claims priority to United Kingdom Patent Application Nos. GB 0800792.4, filed Jan. 16, 2008, and GB 0810714.6, filed Jun. 11, 2008, the contents of which applications are herein incorporated by reference in their entireties. 
     FIELD OF INVENTION 
     The present invention relates to a liquid dispensing system. 
     More particularly the present invention relates to a liquid dispensing system for dispensing beer from a large number of containers or kegs, and a gas recovery system for recovering gas from such a beer dispensing system. 
     BACKGROUND 
     It is known for pubs and the like to store beer in kegs. The kegs are supplied with gas, typically carbon dioxide or nitrogen or a combination of the two, to maintain a desired pressure in the keg. The pressure within the keg helps to drive the beer to the dispensing tap where the beer is served, and also serves to maintain carbonation in the beer. The composition of gas and pressure used depends upon the pressure required by the particular beer in the keg. 
     As beer is used up, more gas needs to be pumped into the keg to maintain the required pressure. Typically, once a keg has been fully used up and no longer contains any beer, the keg is removed from the beer supply line and returned to the brewery where residual gas is then vented. 
     Accordingly, large amounts of gas, particularly carbon dioxide, are required within a beer dispensing system to provide the necessary pressure to the kegs. The greater the number of kegs within the system the greater the amount of gas required. 
     Typically the gas is stored in tanks which are delivered to the pub or like establishment, and once the tanks are emptied they are returned to the gas provider to be re-filled. Since the gas used by the kegs is usually vented to atmosphere, new deliveries of gas have to be made frequently. 
     This has a negative impact on the environment, not only because of the carbon dioxide which is directly vented to the atmosphere from the used kegs, but also because of the emissions from the delivery trucks which need to make frequent deliveries. 
     Accordingly there is a need for a system that can reduce the gas wastage of beverage dispensing systems. 
     A system that attempts to achieve this is shown in WO 01/94252 (Jones), which shows two embodiments of a gas reclamation system for a beverage dispensing system. 
     In the first embodiment, gas from a used keg is passed through a separator which separates the gas before passing the separated gas into a collection tank. The separated gas is then passed through a compressor after which it may be re-used by the system. 
     There are several drawbacks with having the compressor at the last stage as shown in this embodiment of the system. First, having the gas collection tank positioned upstream of the compressor means that only a portion of the gas in the keg will be recoverable, this portion being equal to the balanced pressure between the collection tank and the keg. 
     To increase the amount of gas recoverable from the keg, the compressor will have to be stopped and started frequently to ensure a pressure differential exists between the keg and the collection tank. This causes very high wear on the compressor which will therefore need to be maintained frequently. 
     Secondly, in the first embodiment the separator is shown upstream of the compressor. Therefore the gas will pass through the separator at a pressure no greater than the maximum top pressure of the keg, which is typically about 375 kPa (all pressures quoted are absolute pressures). This pressure is not sufficient to ensure complete separation of carbon dioxide and nitrogen from a gas blend mix, since pressures of more than about 500 kPa are typically required to ensure separation when using a gas separation filter. 
     The second embodiment of the Jones system uses a gas sensor to sense the composition of the gas being reclaimed from the used keg, before passing this gas through a compressor and into a relevant collection tank for that particular composition of gas. 
     A major drawback of this embodiment is the number of collection tanks that are required i.e. one collection tank per type of gas mix recovered. So if an establishment has a number of different types of beer within the dispensing system each requiring a different gas blend mix, then this same number of storage tanks will be required. 
     Another major drawback of both embodiments of the Jones system is that it requires a user to disconnect the keg from the beer supply before connecting it to the gas reclamation system. This increases the amount of labour and therefore costs associated with using the system. 
     It is therefore an object of the present invention to overcome or at least mitigate these and other problems in the prior art. 
     SUMMARY 
     Accordingly the present invention provides a liquid dispensing system, a gas recovery system and a keg handling system as set forth in the appended claims. 
     The liquid dispensing system of the present invention enables beverage containers in the system to be processed with no user intervention during the processing cycle. 
     The layout of the components of the gas recovery system as claimed results in a very high level of gas recovery and separation since the gas is compressed before being passed through a separator. 
     In a preferred embodiment the system is fully automatic, meaning that the system can switch between beer dispensing mode and gas recovery mode automatically. In a still more preferred embodiment, once gas has been fully recovered from a used keg the keg is automatically re-pressurised to a pressure of about 170 kPa ready for return of the keg to the brewery or other supplier. 
     In other words, the present invention discloses a fully automatic system that enables a keg to be connected to a beverage dispensing system, for the keg to be used and the gas recovered, then for the keg to be prepared for return to the brewery with no, or at most minimal, user intervention. 
     In one embodiment of the gas recovery system the gas separator is preferably in the form of a hollow fibre membrane positioned downstream of the compressor. The hollow fibre membrane element contains pores of a size that are designed to only let gas of a certain composition through. By forcing gas through the hollow fibre membrane under pressure the gas in question is separated into one or a number of component gases as required, after which the component gas or gases are passed to storage tanks prior to return to the system. 
     In a second embodiment the gas separator is a hollow fibre membrane positioned downstream of the beer keg. Gas is passed through the hollow fibre membrane and the gas contained in the keg is thereby separated. 
     In a most preferred embodiment, the gas reclamation system comprises a gas blending unit downstream of the at least one storage tank. The gas blending unit can then provide any composition of gas as required e.g. 70% carbon dioxide, 30% nitrogen; 60% carbon dioxide, 40% nitrogen etc. 
     Accordingly, for most applications only three storage tanks are required: an oxygen tank, a nitrogen tank and a carbon dioxide tank, the gas blending unit being capable of blending the nitrogen and carbon dioxide to any composition. When a gas of a single composition is required then this gas bypasses the gas blending unit. 
     The present system therefore significantly reduces the number of gas storage tanks required. 
     A preferred embodiment of the present invention also provides a nitrogen generating mode, thereby eliminating the need to have nitrogen gas tanks delivered. When in nitrogen generating mode the system draws air from the atmosphere and passes it through the gas separator, with the separated nitrogen gas then being delivered to the nitrogen storage tank. Other gases separated during this process, for example oxygen, can be delivered to respective storage tanks as required. 
     The compressor preferably comprises a sealed download system that allows any gas remaining in the compressor following a recovery cycle to be recycled within the system, which therefore eliminates gas wastage and also prevents stalling of the compressor when a new recovery cycle is begun. To achieve this function the compressor comprises a download vessel into which any gas remaining in the compressor following a gas recovery cycle is fed. When a new gas recovery cycle begins, the gas contained in the download vessel is fed back to the inlet of the compressor and is thus retained within the system. 
     The present invention also discloses a liquid dispensing system comprising a gas recovery system as claimed, described in more detail below with reference to the drawings. 
     The present invention also discloses a new design of beverage exhaust detector, which is preferably in the form of a foam on beer (FOB) valve. 
     A FOB valve is a valve that is positioned in the beer line between the beer keg and the beer tap at which the beer is served. A known FOB valve comprises a chamber having an inlet from a beer keg and outlet to a beer tap. Within the chamber is situated a float, which when the FOB valve chamber contains beer floats above the outlet and therefore allows beer to flow through the FOB valve. When the keg is empty or nearly empty, beer no longer flows through the FOB valve, and is instead replaced by foam. The foam is not dense enough to support the float, which therefore drops into the outlet valve thereby closing the FOB valve. This prevents gas or excessive gas from entering the beer line. Any gas in the FOB valve can then be vented via a vent valve. 
     For use with a gas recovery system as claimed, a FOB valve is disclosed further having a safety valve in the beer line. This can effectively isolate the FOB valve from the rest of the system. 
     Preferably, whenever a gas recovery cycle is begun, the FOB valve is isolated from the system. This prevents any pressure differential within the supply line caused by a recovery cycle from lifting the FOB valve float out of the FOB chamber outlet, which could potentially allow unwanted foam into the beer line. The safety valve also prevents any damage occurring to valves within the keg itself or the keg tapping head connector. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Other aspects and preferred features of the invention are described below with reference to the accompanying drawings in which: 
         FIG. 1  is a schematic view of a liquid dispensing system incorporating a gas recovery system as claimed. 
         FIGS. 2 and 3  show a known type of foam on beer valve. 
         FIG. 4  shows a novel foam on beer valve incorporating a safety valve. 
         FIG. 5  is a schematic diagram showing the normal pressure levels in a gas circuit according to the present invention. 
         FIG. 6  is a schematic diagram showing a gas circuit according to the present invention during supply of gas to a keg. 
         FIG. 7  is a schematic diagram showing a gas circuit according to the present invention during recovery of gas from a keg. 
         FIG. 8  is a schematic diagram showing the automatic change over valve system according to the present invention. 
         FIG. 9  is a detailed view of a filter as used in the gas recovery system according to the present invention. 
         FIG. 10  is a schematic view of a liquid dispensing system in a further embodiment with a CO 2  bypass. 
         FIG. 11  is a schematic view of a liquid dispensing system in a further embodiment with a Pressure Swing Absorption separator. 
         FIG. 12  is a schematic view of a liquid dispensing system in a further embodiment with direct processing of the gas and N 2  generation. 
         FIG. 13  is a schematic view of a liquid dispensing system in according to further embodiments disclosed herein. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , a liquid dispense system incorporating a gas recovery system according to the present invention is shown generally at  10 . Beer is drawn from a keg  16  along beer line  15 , and gas may be supplied to the keg and removed from the keg along gas line  17 . For clarity only a single keg is shown, but it should be understood that multiple kegs may be connected to such a gas recovery system. 
     A gas recovery operation will now be described with reference to  FIG. 1 . The beverage dispense system has a central control unit  12 . Once the central control unit  12  has received a signal from a foam on beer (FOB) valve  14  to indicate that a keg  16  is used i.e, no longer contains any beer, pressure sensor  18  checks to see if there is sufficient pressure in the keg for a gas recovery cycle. If pressure sensor  18  detects that there is enough pressure, then valve  64  is closed turning off the gas supply to the keg, and valves  20  and  22  (means for drawing) are opened to allow gas from the keg  16  to enter the gas recovery system. The gas then passes through a filter shown generally at  24  (and described in more detail with respect to  FIG. 9 ) before entering a compressor  26 . 
     The gas is compressed in compressor  26  and subsequently forced through hollow fibre membrane  28  under pressure. A pressure sensor  30  is positioned between the compressor and hollow fibre membrane to detect when the hollow fibre membrane becomes blocked and requires maintenance. 
     Once the gas has entered the membrane it is forced through pores contained within membrane elements which separates the incoming gas into one or a number of component gases. 
     The component gases are then directed to their respective storage tanks. In this exemplary embodiment the gas recovery system contains an oxygen storage tank  32 , a nitrogen storage tank  34  and a carbon dioxide storage tank  36 . 
     The recovered gases are then ready to be re-used by the system. 
     Usually beers are supplied with a gas mixture to provide the necessary pressure. To provide the necessary mixture, the required gases are passed through the gas blending unit  38 , after which the gas mixture can be returned to the system for use. If a single gas is required, for example 100% carbon dioxide, then gas will only be drawn from the carbon dioxide storage tank and no blending of gases will occur. 
     An additional gas supply tank  40  is positioned downstream of the gas blending unit. This additional tank is used to top up the system with additional gas if insufficient gas has been recovered due to losses of any kind in the gas recovery system. Since the present invention provides very high recovery rates of gases, then gas will only rarely be drawn from the additional tank  40 . 
     The gas recovery system of the present invention also has a nitrogen generating mode. When in nitrogen generating mode, air from the atmosphere is drawn through filter  42  and subsequently follows the gas recovery path as described above. Once the air has passed through the hollow fibre membrane  28 , it is primarily split up into nitrogen and oxygen which are then passed on to their respective storage tanks. These recovered gases can then be used by the system. Any oxygen stored in the oxygen storage tank is used to run any gas driven devices within the system. This prevents wastage of oxygen. 
     The sealed download function of the compressor, which further increases the efficiency of the system and reduces gas wastage, operates as follows. Once all gas has been recovered from keg  16 , valves  20  and  22  are closed thus isolating the compressor  26  from the keg. Once these valves are closed, valve  44  is opened by the control unit  12  which allows any remaining gas in the compressor  26  to be downloaded into download vessel  46 . Once a new recovery cycle is started, any gas in the download vessel  46  is returned to the gas recovery circuit to be processed. 
     Once a keg  16  has been fully emptied of beer and all gas recovered, the keg is automatically re-pressurised to approximately 170 kPa for return to the brewery or keg supplier. In this example, once the control unit  12  receives a signal that the gas recovery process has been completed, valve  48  is opened and nitrogen from storage tank  34  is fed back into the keg  16  until the required pressure has been reached. The control unit will then order a signal that tells a user that the keg is ready to be removed. 
     Another feature of the present invention is FOB valve  14 . A known FOB valve is shown in  FIGS. 2 and 3 . 
     In  FIG. 2 , beer is shown entering the FOB valve in the direction of arrow A, and beer is shown exiting the FOB valve in the direction of arrow B. In  FIG. 2 , the keg still has beer remaining in it which causes float  50  to float within chamber  52 . The float is therefore held above an outlet  54  and beer can flow through the beer line. 
     When the keg runs out of beer, foam enters the FOB valve thus causing float  50  to drop within the chamber  52  and close off outlet  54 , thereby preventing foam from entering the beer line. 
       FIG. 3  shows a potential consequence of a keg tapping head connector  56  failing during a gas recovery cycle. As gas is drawn out of the keg  16  a vacuum or partial vacuum is created in the beer line thus causing float  50  to be lifted out of outlet  54 , thus allowing foam and gas to enter the beer line, and potentially damage to be caused to the keg tapping head connector  56 . 
     This problem is overcome by the addition of a safety valve  58  to the beer line, which may be closed during a gas recovery cycle so as to isolate the FOB valve  14  from the gas line  17 . This prevents the FOB valve from being opened during gas recovery. 
       FIGS. 5 ,  6  and  7  are detailed views of parts of the beer dispense and gas recovery circuit of  FIG. 1 , and show pressure levels within the gas supply and recovery circuit during various stages of gas supply and gas recovery. 
       FIG. 5  shows the normal pressure levels found in the gas circuit. The line pressure of the supply gas is set to 445 kPa and then reduced to 375 kPa via pressure reducing valve  60 . The supply then enters the gas ring main  62  and the pressure is reduced again to somewhere between about 238 kPa and 362 kPa depending on the type of beer present in the keg  16 . 
       FIG. 6  shows supply of gas to the keg  16  during a normal beer dispense function. When the keg requires additional pressure, gas flows through valve  64  thereby allowing gas from the gas ring main  62  to flow into the keg  16  via keg tapping head connector  56 . 
       FIG. 7  shows a view of certain parts of the gas circuit during a gas recovery operation. Once the control unit  12  has received a signal from the FOB valve  14  that the keg  16  no longer contains any beer, the control system opens vent valve  66  for about five seconds to vent the FOB valve of any gas. FOB valve  14  is then isolated from the gas circuit by closing safety valve  58 . 
     Valves  64  and  68  are then closed and valve  20  is opened allowing the gas to be passed to the main system for the gas recovery cycle to continue as described above with reference to  FIG. 1 . 
       FIG. 8  shows kegs  16 ,  116 ,  216 ,  316  and  416  connected to a liquid dispensing unit and gas recovery system according to the present invention, with certain features removed from the drawing for clarity.  FIG. 8  shows how the automatic change over valve system works to allow the system to check when kegs are used and therefore either need removing from the system or require a gas recovery cycle, and which kegs still contain beer and therefore may remain connected to the beer line. The automatic change over valve system allows the beverage dispensing system to switch between kegs as they are used up. 
     Each keg  16 ,  116 ,  216 ,  316  and  416  is respectively connected to a FOB valve  14 ,  114 ,  214 ,  314  and  414 , although for ease of understanding only one of these connections is shown in  FIG. 8 . When the control unit  12  receives a signal from the FOB valve  14  indicating that keg  16  is empty, the FOB valve will undergo a venting and isolation procedure as described above with reference to  FIG. 4 . Control valve  70  will then be closed, thus disconnecting the keg  16  from the beer line  15 . 
     Control valve  72  is subsequently opened to connect keg  116  to the beer line. If FOB valve  114  senses that keg  116  is also fully used, then the control unit  12  will close valve  72  to disconnect keg  116  from the beer line, and open valve  74  to connect keg  216  to the beer line. This process is continued through use of FOB valves  314  and  414  and control valves  76  and  78  until the system finds a keg still containing beer. It should be appreciated that this system is suitable for any number of kegs. 
     The control unit  12  will indicate to a user when a beer keg is used, all gas has been recovered, and the keg re-pressurised so that it can be removed from the system and replaced by a fresh keg. 
       FIG. 9  shows in detail filter unit  24  which is positioned upstream of compressor  26 . The filter unit comprises a main housing  80 , within which are contained filter elements  82 ,  84 ,  86  and  88 . The end of the filter unit is closed off with a lid  90 . Gas enters the filter unit in the direction of arrow C and leaves the filter in the direction of arrow D. 
     Recovered gas first passes through moisture removal element  82  to remove moisture from the gas stream. The filter unit also has a moisture sensor  92  that will indicate to an operator via an alarm if the gas stream contains excessive moisture, which may occur in the event of the keg  16  being stored incorrectly, for example in a non-upright position. 
     The recovered gas then passes through a molecular sieve element  84  which removes any further moisture or alcohols remaining in the gas, and then through an absorbent filter element  86  which removes any hydrocarbons in the gas. The recovered gas then passes through polishing filter element  88  which removes any other contaminants remaining in the system. The filtered gas is then passed on to the compressor for the continuation of the gas recovery cycle. 
     It should be appreciated that it is also possible for the filter to comprise the above features separately and not within a single housing. 
       FIG. 10  is a schematic view of a liquid dispensing system with many of the features described previously with reference to  FIG. 1  with the addition of a CO 2  bypass. There is shown the central control unit  12 , FOB valve  14 , beer line  15 , keg  16 , gas line  17 , pressure sensor  18 , valves  20  and  22 , filter  24 , compressor  26 , hollow fibre membrane  28 , pressure sensor  30 , nitrogen storage tank  34 , carbon dioxide storage tank  36 , gas blending unit  38 , additional tank  40 , valves  44  and  48 , download vessel  46 , a float  50 , float chamber  52 , keg tapping head connector  56 , gas ring main  62  and valves  64  and  68 . Furthermore, there is shown the features of the CO 2  bypass pressure sensor  94 , valves  96  and  98  and junctions  92 ,  100  and  102 . Valve  98  is situated in the connection between junctions  92  and  100  and defines the bypass of the hollow fibre membrane  28 . 
     The system and features are as described previously with reference to  FIG. 1 . In addition the system has a CO 2  bypass feature that allows CO 2  to be passed directly to the CO 2  storage tank  36  instead of passing through the hollow fibre membrane  28 . In a preferred embodiment the system has two inputs one for mixed gases and one for CO 2 . The presence of CO 2  is detected, preferably at CO 2  inlet port via pressure sensor  94  and the valves not used in the CO 2  recovery are shut down. Therefore, only valves  96 , and  98  remain open. The gas in filtered at the filter  24  as described in the detail above with reference to  FIG. 1  and flows from the compressor  26  to junction  92  through valve  98  to junction  100 , thereby allowing the gas to bypass the hollow fibre membrane  28 . The gas flows from junction  100  to junction  102  and is passed to the CO 2  storage tank  36 . In further embodiments gasses other than CO 2  bypass the hollow fibre membrane  28 , and are passed directly to their own storage tank in the method as described above. The direct recovery of CO 2  is however preferential over other gasses in beverage dispensing systems. 
       FIG. 11  is a schematic view of a liquid dispensing system in a further embodiment with a Pressure Swing Absorption or PSA separator  104 . There is shown the central control unit  12 , FOB valve  14 , beer line  15 , keg  16 , gas line  17 , pressure sensor  18 , valve  20 , filter  24 , compressor  26 , nitrogen storage tank  34 , CO 2  storage tank  36 , gas blending unit  38 , additional tank  40 , valves  44  and  48 , download vessel  46 , a float  50 , float chamber  52 , keg tapping head connector  56 , gas ring main  62  and valves  64  and  68  and junction  92 . Furthermore there is shown valves  106 ,  108 ,  110 ,  114 ,  116  and  118 , PSA cylinders  105  and  120 , compressor  112 , vent valve  122  and the inlet  124 . In use the gas flows to junction  92  and passes through inlet  124 , from where it is directed towards the PSA separator  104 . 
       FIG. 11  shows a further embodiment of the invention which incorporates a PSA type separator in place of the hollow fibre membrane  28 . The PSA separator  104  may be used when taking into account cost and purity considerations. 
     In the example shown in  FIG. 11  the PSA separator  104  incorporates the CO 2  bypass as described with reference to  FIG. 10 . The PSA separator  104  is one that is known in the art. Those skilled in the art will appreciate that the PSA separator  104  may be used in conjunction with other liquid dispensing systems such as the system as described with reference to  FIG. 1 . 
     In an embodiment, the system functions CO 2  retrieval mode. CO 2  is detected and directed to junction  92  as described with reference to  FIG. 10  and valves  108 ,  114 ,  116  and  118  are closed and valves  106  and  110  are open. In CO 2  retrieval mode, the compressor  26  pressurises the system for a pre-determined length of time, preferably until the system is sufficiently pressurised to dispense beverages at the required pressure. After such length of time valves  106  and  110  are closed and the compressor  26  stops. After another pre-determined length of time, in a preferred embodiment approximately 10 seconds, valve  108  opens and the compressor  112  starts. The contents of PSA separator  104  are emptied into the CO 2  storage tank  36 , and after a predetermined time period the system stops the compressor  112  and closes valve  108 . Preferably during operation if gas pressure is still detected at the inlet of the system  124  the two PSA cylinders  105  and  120  operate on a “one on one off” bases, i.e. when one cylinder is being pressurised the other one will be depressurised in order to provide a continuous stream of gas. This arrangements has the advantage of ensuring that there is little or no wait period in the system during normal running mode. 
     In a further embodiment the system operates in N 2  retrieval mode. In this embodiment PSA cylinder  105  is being filled, the compressor  26  starts up along and the air inlet valve  124  is opened. Valves  108  and  110  are closed and valve  106  is opened thereby filling PSA cylinder  105 , though in further embodiments other PSA cylinders may be filled. The compressor  26  runs for a pre-determined period of time dependent on the pressure required in system and then stops, whereupon valve  106  is closed. After another pre-determined length of time, in a preferred embodiment 10 seconds, the vent valve  122  is opened until the pressure in the PSA cylinder  105  has reached atmospheric pressure, whereupon the vent valve  122  is closed. As with the recovery mode described previously, if a predetermined level has not been reached in the N 2  storage tank  34  the system can operate the two PSA storage cylinders  105  and  120  in the “one on one off” mode as described previously with reference to the CO 2  bypass mode. 
     In further embodiments the PSA separator  104  may comprise any number of PSA cylinders  105 , 120  and the gases recovered from such a system need not be limited to CO 2  and N 2 . 
       FIG. 12  is yet another embodiment of a liquid dispensing system with direct gas processing and N 2  generation. In this embodiment, the gas is processed directly from the keg, thereby avoiding the need of a hollow fibre membrane  28  or PSA separator  104 . There is shown the central control unit  12 , FOB valve  14 , beer line  15 , keg  16 , gas line  17 , pressure sensor  18 , filter  24 , compressor  26 , nitrogen storage tank  34 , carbon dioxide storage tank  36 , gas blending unit  38 , additional tank  40 , valves  44  and  48 , download vessel  46 , a float  50 , float chamber  52 , keg tapping head connector  56 , gas ring main  62  and valves  64  and  68 . Furthermore there is shown, inlets  126  that are connected to filters  128 , valves  129 ,  130 ,  131  which are connected to gas sensors  132  which are connected to a 70/30 mixture tank  134 , a 60/40 mixture tank  136 . and junction  138 . In use the gas flows from the compressor  26  to junction  138 . The gas is directed from junction  138  to the valves  130 , thereby bypassing the hollow fibre membrane  28 . 
     In this embodiment the gas is directly processed from the keg  16  and does not require the need of a hollow fibre membrane  28  or a PSA separator  104  (not shown in  FIG. 12 ). In a preferred embodiment there are three inlets  126  each connected to a specific gas mixture e.g. 70.30, 60/40 or CO 2 , though in other embodiments there may be more than or less than  3  inlets dependent on how many gas mixtures there are to be filtered. In a preferred embodiment the present invention will only filter one type of gas that is passed through the inlets  126  at a time. The inlets  126  in the preferred embodiment are fitted with sensors so that the type of gas being filtered may be determined. Once the gas type has been determined the system only processes said gas type and filters the gas to the corresponding storage tank. For example, if the inlet  126  was to detect a 70/30 mixture, the filters  128  would only pass the 70/30 mixture through and the values  129  and pressure sensors  132  would open and valves  130 ,  131  would shut, thereby directing the gas to the 70/30 storage tank  134 . For the recovery of other gases valves  129 ,  130  and  131  would open and shut as required to direct the gas to the desired storage tank. Those skilled in the art will appreciate that the gas sensors  132  act as an additional fail-safe in only allowing the correct gas type to the tanks  134 ,  136  and  36 . In other embodiments other gas types may be recovered and a varying number of inlets  126  may be used. 
     In a preferred embodiment the gas sensors  132  are CO 2  gas sensors and are used to detect the level of CO 2  in the storage tanks  134 ,  136  and  36 . The detection of the levels of CO 2  in the system is important, as beverage dispense gases, namely CO 2 , are consumed in small quantities by the beer in which the gases come into contact with. Therefore, over a period of time if the gas blends are not checked, the system will eventually loss the blend ratio of the gases as the levels of CO 2  will vary. When the gas sensors  132  have detected an anomaly in the blend ratio of the gases remedial action to return the blends to the desired ratios is undertaken. The present invention provides a method for ensuring that the levels of gases in a blend are at the correct ratio and maintains them at these ratios. 
     In further embodiments the system will also have a hollow fibre membrane  28  or PSA separator  104  to generate N 2  and will also have a gas blender unit  38  to make all possible gas blends required for dispense. 
       FIG. 13  shows a gas recovery system which is not coupled to a drinks dispensing system. In this embodiment the gases are recovered directly from the keg and may act as a stand-alone system from which gas may be recovered from empty kegs. There is shown the central control unit  12 , filter  24 , compressor  26 , hollow fibre membrane  28 , nitrogen storage tank  34 , carbon dioxide storage tank  36 , gas blending unit  38 , valves  44 , download vessel  46 , junctions  92 ,  100 , a 70/30 mixture tank  134 . 
     Furthermore, there is shown the kegs a CO 2  keg  140  and a mixed keg  142 , a keg status indicator  144 , valves  146  that are connected to the CO 2  keg  140  and a mixed keg  142 , and an air input  148 . There is also shown the vents  150 , attached to the hollow fibre membrane  28 , filter  24  and compressor  26 . A valve  152  coupled to the hollow fibre membrane  28  further valves  154  and  156  connected to the 70/30 mixture tank  134  and CO 2  storage tank  36  respectively and a further valve  158  that separates the connection between the 70/30 mixture tank  134  and CO 2  storage tank  36 . 
     In use, the kegs are attached to the gas recovery system. Preferably, there is a status indicator  144  so that a user is able to see how much gas is left in the kegs. In the following example of the embodiment there are two kegs that are connected to the system a CO 2  keg  140  and a mixed keg  142 . The gas flows directly to a valve  146  which is preferentially a one-way check valve. There is also an air input  148  which draws air from the atmosphere to provide nitrogen. The gas is passed through the filter  24 , as described above with reference to  FIG. 1 . Some gas may be vented at this stage through vents  150 . The gas which passes through the filter  24  is compressed at the compressor  26  and flows through the pipe to junction  92 . As in the embodiment described above with reference to  FIG. 10 , the pipe between junctions  92  and  100  define the hollow fibre membrane  28  bypass. In the embodiment shown in  FIG. 13 , the gas may be passed through the hollow fibre membrane  28  and through valve  152  to junction  153  where dependent on which gas is being filtered is either recycled back into the system through valves  146  or stored in the nitrogen storage tank  34 . Those skilled in the art will appreciate that the gas stored need not be nitrogen but is dependent on the structure of the membrane. 
     In a further embodiment the gas recovery system works in the same way as the CO 2  bypass as described with reference to  FIG. 10 . In such an embodiment, dependent on which gas has been detected either valve  154  or  156  is opened. If 70/30 gas has been detected valve  154  is opened and valve  156  is closed and the gas passes directly to the 70/30 storage tank  134 . Likewise if CO 2  has been detected valve  156  is opened and valve  154  is closed and the gas flows directly to CO 2  storage tank. 
     Those skilled in the art that whilst the gas recovery system has been described with reference to a CO 2  bypass such an embodiment may include all other embodiments described within the specification, with the hollow fibre membrane  28 , a PSA separator  104  or direct processing. 
     Also disclosed is an automatic keg handling system comprising a controller or control unit that is configured to communicate with a beverage exhaust detector and beverage container to order a gas recovery system to begin to recover gas from the beverage container once the beverage has been used up. 
     Preferably the gas recovery system is of the type described herein in relation to the present invention, but the automatic keg handling system could potentially be fitted to an existing type of gas recovery system. 
     Preferably the beverage exhaust detector is a foam on beer valve as described with reference to  FIG. 4 .