Tunnel pasteuriser and method for operating a tunnel pasteuriser

Abstract

Method for operating a tunnel pasteuriser with a plurality of sequentially successive treatment zones, wherein containers with a product packed therein are transported by means of a conveying device through the treatment zones and are heated with treatment media having different actual media temperatures, are pasteurized and preferably then cooled again, wherein the actual media temperatures are detected by a control unit and compared with target media temperatures, and wherein heating and/or cooling devices are controlled based on the comparison, characterised in that during the treatment of the containers, initial values for an optimisation are formed from the actual media temperatures of the treatment zones, and the target media temperatures are determined by means of a prediction model for determining the expected degree of pasteurisation with the optimisation, such that at least a minimum degree of pasteurisation of the containers is achieved.

Claims

1. A method for operating a tunnel pasteurizer with a plurality of sequentially successive treatment zones, wherein containers with a product packed therein are transported by a conveying device through the treatment zones and are heated with treatment media having different actual media temperatures, are pasteurized, wherein the actual media temperatures are detected by a control unit and compared with target media temperatures, and wherein heating and/or cooling devices are controlled based on the comparison, wherein, during treatment of the containers, initial values for an optimization are formed from the actual media temperatures of the treatment zones, and the target media temperatures are determined by a prediction model which determines an expected degree of pasteurization with the optimization such that at least a minimum degree of pasteurization of the containers is achieved, and wherein an expected energy and/or resource consumption is determined and minimized from the target media temperatures.

2. The method according to claim 1, wherein the optimization takes place simultaneously over at least two of the treatment zones.

3. The method according to claim 1, wherein a momentary degree of pasteurization per container row is determined and then summed up to determine the expected degree of pasteurization.

4. The method according to claim 3, wherein for the treatment zones in each case the momentary degree of pasteurization per container row is determined taking into account a corresponding actual media temperature of the treatment zone and at least one heat transfer parameter of a corresponding treatment medium of the treatment zone to the containers.

5. The method of claim 3, wherein the momentary degree of pasteurization per container row is determined orthogonal to a running direction.

6. The method according to claim 1, wherein during the optimization of the target media temperatures the actual media temperatures are permuted by at least one change value to determine a gradient of the expected degree of pasteurization via the prediction model.

7. The method according to claim 1, wherein the target media temperatures are optimized in such a way that a maximum product temperature is not exceeded.

8. The method according to claim 1, wherein the target media temperatures are optimized in such a way that a maximum temperature jump between two adjacent treatment zones is not exceeded.

9. The method according to claim 1, wherein the target media temperatures are optimized in such a way that a maximum energy and/or resource consumption during the treatment of the containers is not exceeded and/or minimized.

10. The method according to claim 1, wherein the target media temperatures are optimized in such a way that a TAT (time above temperature) value and/or a KP (killing point temperature) value and/or one or more PE (pasteurization units) values are not exceeded.

11. The method of claim 1, wherein after pasteurization, the containers with the product packed therein are then cooled again.

12. A method for operating a tunnel pasteurizer with a plurality of sequentially successive treatment zones, wherein containers with a product packed therein are transported by a conveying device through the treatment zones and are heated with treatment media having different actual media temperatures, are pasteurized, wherein the actual media temperatures are detected by a control unit and compared with target media temperatures, and wherein heating and/or cooling devices are controlled based on the comparison, wherein, during treatment of the containers, initial values for an optimization are formed from the actual media temperatures of the treatment zones, and the target media temperatures are determined by a prediction model which determines an expected degree of pasteurization with the optimization such that at least a minimum degree of pasteurization of the containers is achieved, and wherein an expected energy and/or resource consumption is determined and minimized from the target media temperatures via a second prediction model and compared with the maximum energy and/or resource consumption.

13. The method according to claim 12, wherein the expected energy and/or resource consumption is determined per zone or per row of containers and then summed.

14. The method according to claim 13, wherein for each of the treatment zones a zone consumption and/or a container row consumption is determined taking into account a corresponding media temperature, at least one heat transfer parameter from a corresponding treatment medium to the containers and a heat capacity of the containers.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Further features and advantages of the invention are explained in more detail using the following embodiments:

(2) FIG. 1 shows embodiments of a tunnel pasteuriser and a method for operating the tunnel pasteuriser in a top view or as a flowchart;

(3) FIG. 2 shows an embodiment of a first prediction model for determining the degree of pasteurisation as a flowchart for the method from FIG. 1; and

(4) FIG. 3 shows an embodiment of a second prediction model for determining the energy and/or resource consumption as a flowchart for the method from FIG. 1.

DETAILED DESCRIPTION

(5) FIG. 1 shows embodiments of the tunnel pasteuriser 1 and the method 100 for operating the tunnel pasteuriser in a top view or as a flowchart.

(6) The left part of FIG. 1 shows the tunnel pasteuriser 1 with a plurality of sequentially successive treatment zones Z.sub.1-Z.sub.4, through which the containers 2 are transported by the conveyor device 3 in the direction T. The conveyor device 3 is here designed as a conveyor belt, for example, but can also be designed as any other suitable conveyor device. A product has been packed into the containers 2, which is pasteurised by the tunnel pasteuriser 1.

(7) During transport through the treatment zones Z.sub.1-Z.sub.2, the containers 2 are sprayed with heated treatment media (water), the media temperature in the treatment zone Z.sub.2 being higher than in the treatment zone Z.sub.1. As a result, the containers 2 are heated step by step and kept above a minimum temperature of 60° C. for at least 10 minutes. This kills off germs in container 2 and pasteurises the product. The heating devices H.sub.1, H.sub.2 are provided to heat the treatment media in the treatment zones Z.sub.1-Z.sub.2. These can include a heater, heat exchanger and the like.

(8) Subsequently, the containers 2 are transported through the treatment zones Z.sub.3-Z.sub.4 and cooled down again step by step. For this purpose, the containers 2 are each sprayed with a cool treatment medium (water), whereby the media temperature in the treatment zone Z.sub.4 is lower than in the treatment zone Z.sub.3. In this way the containers 2 are cooled down in a controlled and slow manner so that they can then be transported to further treatment stations after tunnel pasteuriser 1. Cooling devices K.sub.3 and K.sub.4 are provided to cool the treatment media in treatment zones Z.sub.3-Z.sub.4. These can include a controlled fresh water supply, cooling devices, heat exchangers and the like.

(9) Furthermore, the temperature sensors T.sub.1-T.sub.4 are provided in the treatment zones Z.sub.1-Z.sub.4 to detect the respective actual media temperatures.

(10) The heating and cooling devices H.sub.1, H.sub.2, K.sub.3, K.sub.4 as well as the temperature sensors T.sub.1-T.sub.4 are connected to the control unit 4 via suitable connecting lines.

(11) On the right side of FIG. 1 one can see the control unit 4 in which the method 100 for operating the tunnel pasteuriser 1 is carried out as follows:

(12) In step 101, the actual media temperatures of the individual treatment zones Z.sub.1-Z.sub.4 measured with the temperature sensors T.sub.1-T.sub.4 are detected, for example by means of an interface that detects an analogue or digital signal from the temperature sensors T.sub.1-T.sub.4. The actual media temperatures are then stored in a storage unit of the control unit 4 not shown here.

(13) In step 102, the actual media temperatures are compared with target media temperatures also stored in the storage unit, whereby a difference is formed from the target media temperatures and the actual media temperatures.

(14) In step 103, the heating and cooling devices H.sub.1, H.sub.2, K.sub.3, K.sub.4 are then controlled via the comparison so that the actual media temperatures correspond as closely as possible to the target media temperatures. Control signals are transmitted via the connecting lines to the heating and cooling devices H.sub.1, H.sub.2, K.sub.3, K.sub.4 and the heating or cooling capacity is corrected so that the target media temperatures are maintained as accurately as possible.

(15) In step 104, during the treatment of the containers 2, the target medium temperatures are adjusted with an optimisation as follows:

(16) First, in step 104a, initial values for the optimisation are formed from the actual media temperatures. In other words, the actual media temperatures are set as the start value for the optimisation.

(17) In step 104b the expected degree of pasteurisation is calculated from the initial values and the prediction model 210 described below in relation to FIG. 2. Optionally, the expected energy and/or resource consumption is calculated from the initial values using the prediction model 220 described below in relation to FIG. 3.

(18) Furthermore, the actual media temperatures (the temperatures of the treatment zones) or the initial values are permuted by a slight change value, for example by 0.5° C., and are also entered into the prediction model 210 or 220. In this way, changes in the degree of pasteurisation or in the energy and/or resource consumption are determined by the media temperatures to which the change value is applied, and the gradients of the degree of pasteurisation or of the energy and/or resource consumption are formed from this.

(19) In addition, quality criteria pre-selected by the operating personnel are stored in the control unit 4. These are the minimum degree of pasteurisation and optionally a maximum product temperature, a maximum temperature jump between two adjacent treatment zones Z.sub.1-Z.sub.4, a maximum energy and/or resource consumption. The minimum degree of pasteurisation can be specified in the form of one or more pasteurisation units (PE), a TAT value, a KP value or a combination of these calculation methods.

(20) Using the initial values, the gradients of the degree of pasteurisation or the energy and/or resource consumption and the quality criteria, the target media temperatures are then optimised by means of a generally known optimisation algorithm in such a way that the aforementioned quality criteria are achieved as well as possible.

(21) Subsequently, the target media temperatures determined in this way are stored in control unit 4 and, based on this, steps 101-104 are carried out again, including the optimisation of the target media temperatures. In other words, steps 101-104 are repeated continuously during the treatment of containers 2 with tunnel pasteuriser 1. It is also conceivable that steps 101-103 and step 104 are carried out in parallel.

(22) In that, during the treatment of container 2, initial values for optimisation 104 are formed from the actual media temperatures, the treatment zones Z.sub.1-Z.sub.4 and the target media temperatures are determined with the optimisation by means of the prediction model 210 in such a way that at least a minimum degree of pasteurisation of container 2 is achieved, the target media temperatures are coupled with one another via the optimisation. Consequently, the treatment zones Z.sub.1-Z.sub.4 are controlled at once by the optimisation 104 running during the treatment, so that oscillations are avoided. Consequently, the containers 2 are treated more uniformly during transport through the treatment zones Z.sub.1-Z.sub.4, so that the product quality is improved.

(23) In addition, the optional quality criteria prevent over-pasteurisation, uneven pasteurisation due to a temperature jump, high energy and/or resource consumption, and a treatment temperature that is too low. As a result, container 2 is pasteurised in such a way that the quality of the products packed in it is particularly high and contamination with non-destroyed germs is avoided.

(24) FIG. 2 shows the prediction model 210 for determining the degree of pasteurisation in a flowchart. It can be seen that a media temperature is entered into the prediction model 210 in step 211 for each of the treatment zones Z.sub.1-Z.sub.4.

(25) For each of the treatment zones Z.sub.1-Z.sub.4, the product temperature prevailing in container 2 is now determined in step 212 by means of at least one heat transfer parameter. The at least one heat transfer parameter is preferably determined experimentally by means of a measurement, for example by spraying a container in a test chamber with a treatment medium in predetermined temperature steps and measuring the product temperature in the container for each temperature step. Calculation methods are also conceivable.

(26) Subsequently, for each treatment zone Z.sub.1-Z.sub.4, the product temperature is used to determine the momentary degree of pasteurisation for each row of containers at each treatment time, for example the input to pasteurisation units (PE), which can be determined using methods generally known in the technical literature (for example in H. W. Del Vecchio, C. A. Dayharsh, and F. C. Baselt: Thermal death time studies on beer spoilage organisms. Proceedings of the American Society of Brewing Chemists, 1951, page 45; Andrew Geoffrey Howard Lea and John R. Piggott, editors: Fermented Beverage Production. Second edition. Springer, 2003. page 379; Carsten Zufall, Karl Wackerbauer: The Biological Impact of Flash Pasteurisation Over a Wide Temperature Interval, Journal of The Institute of Brewing Volume 106, Issue 3 (pages 164-168)).

(27) Then, for each container row, the momentary degrees of pasteurisation of a container row are summed up over the treatment period in step 213 and output as degree of pasteurisation in step 214.

(28) FIG. 3 shows the prediction model 220 for determining energy and resource consumption in a flowchart. It can be seen that in step 221 a media temperature and a current product temperature are entered into the prediction model 220 for the treatment zones Z.sub.1-Z.sub.4.

(29) For each of the treatment zones Z.sub.1-Z.sub.4, the product temperature prevailing in the containers 2 due to spraying with the treatment medium is now determined in step 222 by means of the at least one heat transfer parameter described above in relation to step 212.

(30) Furthermore, the differential temperature by which the product is heated or cooled as it passes through the respective treatment zones Z.sub.1-Z.sub.4 is determined. The heat capacity of the product packed in container 2, the mass of product filled and the differential temperature can then be used to calculate the energy absorbed or released by container 2. As the number of containers in the respective treatment zone Z.sub.1-Z.sub.4 is known, for example by means of a counting device at the entrance of the tunnel pasteuriser 1, the zone consumption required for treatment in the treatment zone Z.sub.1-Z.sub.4 can be determined. For example, the previously described calculation of the energy and resource quantity for a tunnel pasteuriser is disclosed in WO 2010/094487 A1.

(31) Then the zone consumptions of all treatment zones Z.sub.1-Z.sub.4 are summed up in step 223 and output as energy and resource consumption in step 224.

(32) The output degree of pasteurisation or the energy and/or resource consumption is used in optimisation 104, as described in relation to FIG. 1 above, to optimise the target media temperatures.

(33) It goes without saying that features mentioned in the embodiments described above are not limited to these special combinations and are possible in any other combination.