Abstract:
A hot filling system for a liquid, with heat recovery, and a corresponding method, wherein prior to heating and filling the liquid is first preheated in a heat exchanger. A portion of the heated liquid to be filled is again cooled in a recooler and recirculated. The return line of the recooler is here connected to the supply line of the heat exchanger so as to transfer heat energy from the recooler to the heat exchanger. This reduces energy losses in comparison with known systems.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of priority of German patent application DE 102008056597, filed Nov. 10, 2008 . The entire text of the priority application is incorporated herein by reference. 
     FIELD OF THE DISCLOSURE 
     The present disclosure relates to a hot filling system for a liquid, particularly a drink, with heat recovery, the system comprising: a heat exchanger for preheating the liquid to a first temperature; a heater arranged downstream of the heat exchanger for heating the liquid to a second temperature higher than the first temperature; a first distributor arranged downstream of the heater for dividing the liquid e.g. into a portion to be filled into bottles, jars, bags, or the like, and into a portion to be returned to the inlet of the heat exchanger; a bottle filler arranged downstream of the first distributor for filling the liquid into bottles; and a recooler arranged downstream of the first distributor for cooling the portion to be returned. 
     BACKGROUND 
     Hot filling after pasteurizing, e.g. in a short-time heater, is an established method for filling drinks into bottles or bags in a preserved or durable condition. The untreated drink is preheated, degassed and then pasteurized as a rule. After the filling process, e.g. at 85° C., the filled bottles are cooled in a bottle cooling device with the help of a coolant stream, e.g. by way of spraying, to a temperature of e.g. 30° C. that is suited for further processing. 
     It is known from T. Herty: Molchbare Pasteuranlage mit kontinuierlicher Vakuumentgasung, Flüssiges Obst, 8/2002, 508-510 that during the hot filling of drinks, particularly at a standstill of the bottle filler, already pasteurized liquid is cooled in a recooler and is admixed again via a buffer to the untreated liquid. 
     It is moreover known from DE 10 2005 053 005 A1 that hot-filled beverage bags are cooled by a coolant stream and the coolant stream is circulated such that the absorbed heat is again discharged to the drink to be heated. 
     The heat withdrawn from the filled bottles or bags is e.g. passed into a heat exchanger for preheating the liquid to be treated. By contrast, the heat withdrawn during recooling of the liquid that has not been filled is disposed off in known hot filling systems in a cooling tower and represents an energy loss. This must also be taken into account during failure-free normal operation when a specific portion of the heated liquid that has not been filled yet is recooled and again admixed to the untreated liquid so as to stabilize the operation of the system. 
     SUMMARY OF THE DISCLOSURE 
     It is an aspect of the present disclosure to reduce the energy loss during hot filling as compared with known systems. 
     This aspect is achieved with a hot filling system. Hence, the return line of the recooler is connected to the supply line of the heat exchanger so as to transmit heat energy from the recooler to the heat exchanger. 
     As a result, the liquid can be preheated with heat recovered during recooling and energy losses can be reduced. 
     Preferably, the first distributor passes the liquid substantially completely through the recooler at a standstill of the bottle filler. This maximizes the energy amount available for recovery. 
     Preferably, the hot filling system comprises a second distributor that adjusts a portion of a heat transport medium to be fed from the recooler into the heat exchanger. The heating power to be transmitted can thereby be metered in a selective way. 
     In a further preferred development of the disclosure the first distributor divides the liquid during operation of the bottle filler such that the portion to be returned accounts for 10-15% of the portion to be filled. This ensures a stable control of the system. 
     Preferably, the hot filling system further comprises a bottle cooler for cooling the filled bottles, the bottle cooler having a return line connected to the supply line of the heat exchanger to transmit heat energy from the bottle cooler to the heat exchanger. As a result, the heat energy released during cooling can be recovered and used again for heating the liquid. 
     In a development of the disclosure the hot filling system further comprises a third distributor that passes heat transport medium from the return line of the bottle cooler selectively into the heat exchanger or the supply line of the bottle cooler. As a result, the recovered amount of heat can be controlled in a targeted way and the heat transport medium can be circulated in case of need. 
     It is advantageous when the third distributor passes the heat transport medium from the return line of the bottle cooler into the supply line of the bottle cooler when no bottles are cooled in the bottle cooler. This delays an unintended cooling of the bottle cooler. 
     Preferably, the supply temperature of the heat exchanger is 60-75° C. This enables a particularly efficient heat recovery. 
     The underlying aspect is further achieved with a method for hot filling liquids. Thus the liquid is preheated with heat energy recovered during recooling of the portion to be returned. 
     Preferably, the portion to be returned is set such that it accounts for 10-15% of the portion to be filled in the bottling process. This ensures a stable control of the system. 
     Preferably, the liquid is completely returned upon interruption of the bottling process. This maximizes the energy amount available for the recovering process. 
     Preferably, the method further comprises the following steps: cooling the filled bottles; and preheating the liquid with heat energy recovered during cooling of the bottles. The heat energy released during cooling can thereby be recovered and used again for heating the liquid. 
     Preferably, the liquid is preheated upon interruption of the bottling process with heat energy recovered during cooling of the bottles and with heat energy recovered during recooling. This ensures a preheating as constant as possible during the standstill period and minimizes the amount of energy to be fed from additional heat sources during preheating. 
     Preferably, the heat energy recovered during cooling of the bottles is used for preheating the liquid only for a period as long as bottles are being cooled. This prevents a situation where a device used for the bottle cooling process cools down rapidly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment is described in the drawing, in which: 
         FIG. 1  shows a diagram of a hot filling system according to the disclosure; 
         FIG. 2  shows a diagrammatic curve of the heating power available for heat recovery when the bottle filling process is temporarily stopped. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  schematically shows a hot filling system  1  for a liquid  2 , particularly a drink. The arrows shown in broken line represent the flow direction of the liquid  2 ; the arrows shown in continuous line represent the flow direction of a heat transport medium  3 , such as e.g. water. 
     Accordingly the hot filling system  1  comprises a collecting vessel  4  for temporarily storing the liquid  2  to be treated and filled, the vessel having arranged downstream thereof in series a heat exchanger  6 , a preheater  8 , a heater  10  and a first adjustable three-way distributor  12  with an inlet  12   a  and two outlets  12   b  and  12   c.    
     The heat exchanger  6  comprises an inlet  6   a  and an outlet  6   b  for the liquid  2  and a supply line  6   c  and a return line  6   d  for the heat transport medium  3  and preheats the liquid  2  to a preheat temperature TV, which is e.g. needed for conventional degassing of the liquid in a degassing apparatus (not shown). 
     In case of need the preheater  8  additionally preheats the liquid  2 , e.g. in the case of an insufficient heating power of the heat exchanger  6  or upon start of the system  1 . 
     In the heater  10 , the liquid  2  is heated to a treatment temperature TB that is higher than the preheating temperature TV. 
     The first distributor  12  distributes the liquid  2  flowing out of the heater  10  into a portion FA to be filled and into a portion FR to be returned into the product circuit or the collecting vessel  4 . Accordingly the outlet  12   b  of the first distributor  12  has arranged downstream thereof a bottler  14  which fills the liquid portion FA into bottles  16 . The outlet  12   c  has arranged downstream thereof a recooler  18  with an inlet  18   a  and an outlet  18   b  for the liquid  2 , as well as a supply line  18   c  and a return line  18   d  for the heat transport medium  3 . The outlet  18   b  of the recooler  18  leads back to the collecting vessel  4 . 
     The recooler  18  forms a first heat transport medium circuit  24  together with a second adjustable three-way distributor  20 , the heat exchanger  6  and a first cooling tower  22 . The inlet  20   a  of the second distributor  20  is fed from the return line  18   d  of the recooler  18  and divides the stream of the heat transport medium  3  into a portion WE for external heat disposal in the first cooling tower  22  and into a portion WR for heat recovery in the heat exchanger  6 . Accordingly an outlet  20   b  of the second distributor  20  is connected to the supply line of the first cooling tower  22 ; the other outlet  20   c  is connected to the supply line  6   c  of the heat exchanger  6 . 
     The hot filling system  1  further comprises a bottle cooler  28  for cooling the filled bottles  16 . Said cooler comprises a supply line  28   c  and a return line  28   d  for the heat transport medium  3  and forms a second heat transport medium circuit  34  with a third adjustable three-way distributor  30 , the heat exchanger  6  and a second cooling tower  32 . The inlet  30   a  of the third distributor  30  is here fed from the return line  28   d  of the bottle cooler  28  and passes the heat transport medium  3  heated in the bottle cooler  28  in a first position via the outlet  30   b  to the supply line  6   c  of the heat exchanger so as to transmit heat energy from the bottle cooler  28  to the heat exchanger  6 . In a second position the third distributor  30  shorts the supply line  28   c  and the return line  28   d  of the bottle cooler  28  via the outlet  30   c.    
     The liquid  2  is e.g. a drink, such as water, milk, juice, beer, lemonade, or another liquid, which is treated by the action of heat and is filled in the heated state. The liquid may contain an emulsion, suspension and/or foam. 
     The heat exchanger  6  may e.g. be a conventional plate or tube heat exchanger and is preferably operated at a supply temperature of 50-80° C. In  FIG. 1  both heat transport medium circuits  24  and  34  are respectively connected in parallel with the supply line  6   c  and the return line  6   d  for the sake of clarity. The circuits, however, could just as well be separated from each other, e.g. by check valves, by a separate supply and return line  6   c ,  6   d  for each circuit or by a two-stage configuration of the heat exchanger  6 . It is decisive that both circuits  24 ,  34  can be used for preheating the liquid  2  and combined and optimized in case of need. Likewise, the cooling towers  22  and  32  and their cooling capacity, respectively, and the respective volume flows could be connected and controlled in a way differing from that shown in  FIG. 1  as long as they fulfill the described function. 
     The preheater  8  can e.g. be heated with steam. 
     The heater  10  is e.g. a conventional, steam-operated short-time heater with a heat holding path on which the liquid  2  to be treated is held at the treatment temperature TB for a specific period of time, e.g. for pasteurizing. The heater  10  may comprise a correction cooler (not shown) to set the treated liquid  2  to a temperature suited for bottling, e.g. 85° C. The heat quantity withdrawn from the liquid  2  in this process is returned, as much as possible, to the inlet of the heater  10  to heat subsequent inflowing liquid  2 . 
     The distributor  12  is e.g. an electrically controlled mixing valve with which the liquid portions FR and FA can be varied in relation with each other in a way as finely graduated as possible or continuously and can also be set such that the liquid  2  is passed exclusively to the bottle filler  14  or to the recooler  18 . 
     The bottle filler  14  fills the heated liquid  2  as supplied to it in a conventional way continuously into bottles  16 . The bottles  16  may e.g. be made from glass or plastic. Other containers, such as bags, may be filled just as well. 
     The filled bottles  16  are cooled in the bottle cooler  28  e.g. by being sprayed with water to a temperature suited for further processing, e.g. 30° C. The bottle cooler  28  may e.g. be designed as a multistage cooling tunnel. The bottle cooler  28  may e.g. be designed such that a return temperature that is as high as possible is achieved, e.g. in the range of 50° C. to 80° C. so as to optimize the heat recovery efficiency on the heat exchanger  6 . This can e.g. be achieved by designing individual cooling stages of the cooling tunnel in an appropriate way and/or by increasing the residence time of the bottles  16  in the bottle cooler  28  or by reducing the volume flow of the heat transport medium  3  through the bottle cooler  28 . 
     The third distributor  30  is preferably an electrically controlled switching valve that passes the heated heat transport medium  3  flowing out of the return line  28   d  of the bottle cooler  28 , either completely to the supply line  6   c  of the heat exchanger  6 , or, however by way of shorting, returns it to the supply line  28   c  of the bottle cooler  28 . The shorting operation prevents or delays a cooling of the bottle cooler  28  in cases where temporarily no filled bottles  16  enter the bottle cooler  28 . The third distributor  30 , however, could also be configured as a mixing valve. 
     The recooler  18  is preferably configured such that a return temperature that is as high as possible is achieved, e.g. 50-80° C., to achieve a heat recovery efficiency on the heat exchanger  6  that is as high as possible. The liquid  2  should here be cooled down approximately to the temperature of the untreated liquid  2 , e.g. to a temperature of about 20-40° C. before it mixes in the collecting vessel  4  with untreated liquid  2 . 
     With the hot filling system  1  according to the disclosure it is possible to work in the following way during normal operation after the respective desired temperatures have been reached and with a continuous filling of the bottles  16  and their introduction into the bottle cooler  28 : 
     Liquid  2  is continuously passed from the collecting vessel  4  through the heat exchanger  6 , whereby it is heated to a preheating temperature TV. If the heating capacity of the heat exchanger  6  is insufficient, the liquid  2  is additionally heated up in the preheater  8  to the temperature TV. The liquid  2  is subsequently treated e.g. in a vacuum degassing process (not shown) and/or other processes and passed to the heater  10 . In this heater the liquid  2  is heated, for instance for pasteurizing, to a treatment temperature TB for a certain period of time, where: TB&gt;TV. A portion FA of the treated liquid  2  is passed into the bottle filler  14  and filled in this bottle filler into bottles  16  at a temperature of preferably 80-90° C. The remaining portion FR of the treated liquid  2  is passed into the recooler  18 ; it is cooled therein to 20-40° C. and returned again into the collecting vessel  4 . The proportionate return of the liquid  2  during normal operation ensures a stable operation of the filling system. As a consequence, a situation can for example be prevented where liquid  2  must be discarded due to lack of sterility caused by delayed filling. The ratio FR/FA is 0.05-0.2 during normal operation. Preferably, the ratio FR/FA is 0.1-0.15. 
     The predominant portion of the heating power that is available in the heat exchanger  6  during normal operation derives from the bottle cooler  28 . The ratio of the heating powers available from the heat transport medium circuits  24  and  34  on the return lines  18   d  and  28   d , respectively, corresponds approximately to the ratio FR/FA during normal operation. 
     The heat recovery in the bottle cooler  28  and in the recooler  18  and in the heat medium circuits  34  and  24 , respectively, may be combined to minimize the energy losses in the filling system  1  during normal operation and/or to optimize the control thereof. 
     With the hot filling system  1  according to the disclosure it is possible to operate in case of failure, particularly at a standstill of the bottle filler  14 , as follows: 
     Upon stop of the bottle filler  14  the whole heated liquid  2  should be circulated under normal operation conditions so as to be able to swiftly re-continue the filling operation. 
       FIG. 2  shows the heating power potentially available for energy recovery in the circuits  24  and  34  during operation B and during a temporary standstill S of the bottle filler  14 . During normal operation there are substantially time-constant heat quantities available from circuits  24  and  34 , respectively. 
     Upon stop of the bottle filler  14  the whole liquid  2  is passed from the first distributor  12  into the recooler  18  and is cooled in said recooler approximately to the start temperature of the untreated liquid  2 . This will increase the heating power available on the return line  18   d  of the recooler  18  until said power corresponds to the output power of the bottle cooler  14  during normal operation. 
     Even after the bottle filler  14  has been stopped, already filled bottles  16  are still transported to the bottle cooler  28 , so that the same heating power as during normal operation is at first still available on the return line  28   d  of the bottle cooler  28 , e.g. for a period of two minutes. Starting from time S′, after all of the conveyed bottles  16  have been cooled, the heating power available on the bottle cooler  28  is decreasing continuously. As can be seen from  FIG. 2 , the available heat output power of the bottle cooler  28  is normally increasing or decreasing at a slower pace than that of the recooler  18 . 
     To delay the cooling of the bottle cooler  28 , the third distributor  30  shorts the supply line  28   c  and the return line  28   d  of the bottle cooler  28  at time S′ and simultaneously prevents that the supply line  28   c  is fed from the second cooling tower  32 . 
     When the operation of the bottle filler  14  is resumed, the first distributor  12  is again reset to normal operation so that only the original liquid portion FR is passed to the recooler  18 . As a result, the heating power available on the return line  18   d  of the recooler  18  is again decreasing to the value prevailing during normal operation. 
     Since the available heat output power of the bottle cooler  28  is rising at a slower pace than the power of the recooler  18  is decreasing, as shown in  FIG. 2 , the heating power available on the heat exchanger  6  on the whole may temporarily fall below a minimum value needed for preheating the liquid  2 , so that additional heating power must be applied by the preheater  8  for this purpose. 
     Due to the combined heat recovery in the bottle cooler  28  and in the recooler  18  and in the heat medium circuits  34  and  24 , respectively, the liquid  2  can predominantly be preheated by recovered energy and an additional external energy input can considerably be reduced in comparison with conventional systems.