Method for thermally treating a product by means of steam in an autoclave having condensate discharge

Abstract

The invention relates to a method for thermally treating at least one product by means of steam in an autoclave which comprises a receiving container, a steam supply and a condensate discharge, the receiving container delimiting a treatment chamber for receiving the products, the steam supply opening into the treatment chamber and the condensate discharge branching off from the treatment chamber, and, in order to carry out a treatment pass, the product being positioned in the treatment chamber and the steam being applied thereto, characterized in that condensate accumulating in the treatment chamber is discharged via the condensate discharge already during the application of the steam to the product.

Description

[0001] Method for thermally treating a product by means of steam in a

[0002] Autoclave with condensate drain

[0003] The invention relates to a method for thermally treating at least one product using steam in an autoclave comprising a receiving vessel, a steam inlet, and a condensate outlet. The receiving vessel defines a treatment chamber for receiving the product, the steam inlet opens into the treatment chamber, and the condensate outlet branches off from the treatment chamber. To carry out a treatment cycle, the product is positioned in the treatment chamber and exposed to steam. The invention further relates to an autoclave configured for carrying out such a method.

[0004] Such a process and such an autoclave can be used, for example, to preserve products, particularly foodstuffs. The products can be packaged in packaging such as glass jars, cans, or film packaging. For treatment in the autoclave, the products can be arranged in so-called product cages or stacked on perforated storage sheets that are moved into the autoclave and out again after treatment. Within the product cages, the products are positioned at a distance from one another using perforated intermediate layers. The product cages and intermediate layers are designed to be fluid-permeable in order to achieve the most even possible exposure of the products to steam and also to water used as a cooling liquid in the autoclave.

[0005] In such a process, a large amount of condensate can occur as a result of the cooling of the steam due to the transfer of heat energy from the steam to the products, among others. This condensate usually collects in the floor of the treatment chamber and is only discharged after the end of a treatment cycle. As a result of the temperature inside the treatment chamber rising during the treatment, condensate that has occurred relatively early in the treatment still has a relatively low temperature, for example, initially around 40°C. As the treatment progresses, this condensate that has already occurred is then also heated up by a further supply of steam, which may, for example, have a temperature of around 160°C, which is unnecessary for the product treatment. This increases the energy required to carry out the process.

[0006] Based on this prior art, the object of the invention was to improve a method according to the above-mentioned type with regard to the energy required for its implementation.

[0007] This object is achieved by the subject matter of the independent patent claims. Advantageous embodiments thereof are subject matter of the dependent patent claims and will become apparent from the following description of the invention.

[0008] According to the invention, a method is provided for the thermal treatment of at least one product by means of steam, in particular water vapor or a water vapor-air mixture, in an autoclave, wherein the autoclave comprises a receiving vessel, a steam inlet and a condensate outlet, wherein the receiving vessel delimits a treatment chamber for receiving the products, the steam inlet opens (directly or indirectly) into the treatment chamber and the condensate outlet branches off (directly or indirectly) from the treatment chamber. To carry out a treatment cycle, the at least one product is positioned in the treatment chamber and (at least also) exposed to the steam, whereby it is heated and tempered in a targeted manner, preferably in a controlled manner according to a defined temperature profile curve.According to the invention, condensate accumulating in the treatment chamber is already removed via the condensate drain during the application of steam to the at least one product. This prevents this already accumulated condensate from being heated by newly supplied steam during the further implementation of the process, so that the thermal energy required for such heating of the condensate can be saved. Thus, the amount of steam supplied to the treatment chamber for carrying out the treatment cycle can be reduced. The reduction can be between 10% and 15% compared to a corresponding process without the condensate drain according to the invention.An autoclave according to the invention for the thermal treatment of at least one product using steam accordingly comprises a receiving vessel, a steam inlet, and a condensate drain. The receiving vessel defines a treatment chamber for receiving the products, the steam inlet opens (directly or indirectly) into the treatment chamber, and the condensate drain branches (directly or indirectly) out of the treatment chamber. The autoclave is further configured to at least temporarily discharge condensate accumulating in the treatment chamber via the condensate drain while the at least one product is being exposed to steam.

[0009] In order to enable such automated condensate removal, an autoclave according to the invention can preferably comprise a control device for automatically removing the accumulating condensate. For this purpose, the control device can comprise a control unit that can or does actuate a condensate removal valve. The control unit can also have a sensor for detecting the presence of condensate in the treatment chamber or in a line fluidically connected to the treatment chamber, which line can in particular be part of the condensate removal. The control unit can actuate the valve in particular as a function of a signal from the sensor, so that the valve is opened by the control unit when the presence of condensate or a defined fill level of the condensate is detected.

[0010] According to the invention, "steam" is understood not only to mean a chemically pure, gaseous substance which is in the liquid state at room temperature and which can be converted back into the liquid state by condensation, but also any mixture of such a pure, gaseous substance with another gas.

[0011] According to a preferred embodiment of a method according to the invention, it can be provided that the condensate is discharged intermittently or continuously via the condensate discharge while the at least one product is exposed to the steam. With intermittent discharge, condensate is first collected and then the corresponding accumulation of condensate is discharged while the products are still exposed to the steam. This preferably occurs several times during a treatment run, in particular after a defined period of time or after the accumulation of a defined amount of condensate. In particular, it can also be provided that both measures are combined, so that discharge takes place as soon as one of the defined specifications (period of time and amount of accumulated condensate) is met.With continuous condensate removal, however, accumulating condensate is removed immediately, potentially maximizing the energy savings according to the invention. On the other hand, such continuous condensate removal may require a continuously open condensate drain, which may be associated with process-related disadvantages, for example, with regard to the formation of a defined atmosphere within the receiving space. This may apply in particular if the defined atmosphere within the receiving space comprises an overpressure compared to the pressure in the environment of the autoclave, as may preferably be provided.

[0012] According to a preferred embodiment of a method according to the invention, the condensate can be discharged into a collection device. In an autoclave according to the invention, the condensate discharge can lead into the collection device. This allows for storage and thus further use of the accumulated condensate.

[0013] Such further use of the condensate can preferably be or include preheating at least one product to be thermally treated in a subsequent treatment pass. A preferred embodiment of a method according to the invention can therefore provide that the condensate produced during a first treatment pass for the thermal treatment of at least one first product is used to preheat at least a second product during a second treatment pass. This takes advantage of the fact that the condensate discharged during the first treatment pass can have a higher temperature than the (second) product at the beginning of the (second) treatment pass. In this way, the energy required for the thermal treatment of the (second) product can be kept as low as possible.In order to enable the discharged condensate to be used for preheating at least one product during a subsequent treatment run, an autoclave according to the invention can be designed such that the collecting device is fluidically connected to the treatment chamber via a condensate supply.

[0014] Another further use of the condensate can also be provided within the scope of a method according to the invention, for example, preheating a liquid, in particular water, which is subsequently evaporated to generate the steam to be used for the thermal treatment of at least one product. Further use of the discharged condensate can also be provided independently of a method according to the invention, for example, for any heating or cleaning measure.

[0015] In order to keep the cooling of the condensate discharged during the first treatment run as low as possible and thus to keep the usable thermal energy of the condensate as high as possible in a method according to the invention in which the condensate is discharged into the collecting device, it can preferably be provided that the collecting device thermally insulates the condensate or the collecting device of an autoclave according to the invention is set up for thermal insulation of the condensate and accordingly comprises at least one design feature by means of which heat transfer from the condensate in the collecting device to the environment is deliberately kept low.This feature can, for example, be a multi-layered design of a wall of the collecting device, with a gap formed between two layers of this wall being evacuated as far as possible (creating a vacuum) or filled with at least one material with the lowest possible thermal conductivity. This material can be solid, liquid, or gaseous.

[0016] In order to pump the condensate into the collection device and / or out of the collection device, a condensate pump can be integrated into the condensate discharge and / or the condensate supply (respectively).

[0017] The invention is explained in more detail below using an exemplary embodiment illustrated in the drawings. In the drawings:

[0018] Fig. 1 : an autoclave according to the invention in a perspective view,

[0019] Fig. 2: the autoclave in a view from above,

[0020] Fig. 3: the autoclave in a side view,

[0021] Fig. 4: the autoclave in a front view,

[0022] Fig. 5: a cross-section through the autoclave according to the section plane A - A in Fig. 3,

[0023] Fig. 6: a longitudinal section through the autoclave according to the section plane B - B in Fig. 3 and

[0024] Fig. 7 shows the autoclave in a perspective view, whereby a wall of a receiving container of the autoclave is partially not shown.

[0025] The autoclave shown in the drawings comprises a receiving container 1 with a cylindrical container shell 2, each of whose ends is closed by means of an openable container lid 3. However, an embodiment can also be provided in which only one of the ends is closed by means of an openable container lid and the other end is closed firmly (i.e. cannot be opened), for example by means of a so-called dished end. The receiving container 1, the central longitudinal axis of which is horizontal, delimits a treatment chamber 4 for receiving products (not shown) that can be thermally treated therein using steam. The products can be, for example, fluid-tight packaged foodstuffs that are to be sterilized by the thermal treatment. For this purpose, the steam can have a temperature of, for example, 158°C, at least temporarily.

[0026] To load the autoclave with the products, at least one of the container lids 3 can be opened and the products introduced into the treatment chamber 4. For this purpose, the products can be arranged, for example, in so-called product cages and distributed over several levels thereon. These product cages can preferably be designed to be rollable and, for example, have grid-shaped shelves for the products in order to ensure the best possible flow through them and thus enable the best possible and even exposure of the products to steam. The at least one previously opened container lid 3 is closed after the products have been introduced into the treatment chamber 4 in order to seal the treatment chamber 4. The treatment chamber 4 can preferably be pressure-tightly sealed against the environment.

[0027] Thermal treatment of the products takes place in batches, i.e., in one treatment run for a limited number of products accommodated in the treatment chamber 4. Such a treatment process comprises preheating the products, then targeted heating and tempering of the products, and then targeted cooling of the products. At least temporarily, during the thermal treatment of the products, a defined pressure profile can be set in the treatment chamber 4 with an overpressure relative to the ambient pressure.

[0028] The products are preheated exclusively, or at least partly, using condensate generated in a previous treatment run. This accumulated condensate is temporarily stored in a collecting device in the form of a cylindrical, horizontally oriented condensate tank 5, which is arranged outside the receiving container 1. For preheating, the temporarily stored condensate is pumped into the treatment chamber 4 by an electric motor-driven condensate pump 6, which can be designed, for example, as a centrifugal pump. The condensate pump 6 is integrated into a condensate supply line 7. The condensate supply line 7 (with the condensate pump 6) is part of a condensate supply line 8, which connects the condensate tank 5 to the treatment chamber 4.The condensate is discharged into the treatment chamber 4 by means of two spray lines 9, one of which is arranged approximately halfway up one of the two sides of the treatment chamber 4 and which extend horizontally over essentially the entire length of the treatment chamber 4 (cf. Fig. 5). The spray lines 9 are each arranged within a side chamber 4b of the treatment chamber 4. These side chambers 4b are separated by lateral partition walls 20 from a central chamber 4a, within which the products are arranged. An arrangement of the (then, for example, four) spray lines 9 within the central chamber 4a is also possible as an alternative. The condensate could then be applied directly to the products arranged therein.The spray lines 9 have, along their respective longitudinal sections, a plurality of outlet openings (evenly or unevenly) spaced from one another, through which the condensate is discharged.

[0029] By means of an electric motor-driven fan 19, which is arranged at a first end of the treatment chamber 4, the aerosol (air with the condensate) located within the treatment chamber 4 can be circulated within the treatment chamber 4. The aerosol is circulated in such a way that it flows through the central chamber 4a in the direction of the fan 19 and is returned via the side chambers 4b to the second end of the treatment chamber 4 (see Fig. 6). The condensate introduced into the side chambers 4b is thereby applied to the products arranged within the central chamber 4a of the treatment chamber 4 in order to preheat the products by transferring thermal energy from the condensate to the products.

[0030] Preferably, the outlet openings are each formed by a nozzle of the spray lines 9. These nozzles can, in particular, be designed to atomize the condensate in order to achieve the largest possible surface area and the most uniform wetting of the products with the condensate. This maximizes the transfer of thermal energy from the condensate to the products.

[0031] The condensate supply line 7 originates from an outlet flange 10 of the condensate tank 5 (see Fig. 5), which forms a condensate outlet of the condensate tank 5. Starting from the outlet flange 10, the condensate supply line 7 first leads to the condensate pump 6 and from there to an upper side of the receiving container 1. There, the condensate supply line 7 merges into two distribution lines 11, each leading to one of the spray lines 9. In the region of a branching of the two distribution lines 11, a coolant inlet flange 12 is also provided, to which a coolant line (not shown) can be connected. A coolant, preferably water, can be introduced into the treatment chamber 4 via the coolant line, the coolant inlet flange 12, the distribution lines 11 and the spray lines 9.

[0032] Since the outlet flange 10 is located near one end of the condensate tank 5, it is provided to align the condensate tank 5 with a slight inclination such that a liquid located in the condensate tank 5 flows towards the outlet flange 10 due to gravity.

[0033] The condensate used to preheat the products is discharged from the treatment chamber 4 and not temporarily stored again in the condensate tank 5 because the temperature of the latter is usually too low to be usefully used to preheat products in a subsequent treatment process. However, if the condensate still has a sufficiently high temperature, it can be fed back into the treatment chamber 4 via the condensate tank 5 to preheat the products. The condensate used to preheat the products can then be discharged from the treatment process, i.e. after being used to preheat the products, so that it is no longer used in the context of a method according to the invention. Alternatively, further use can also be made in the context of a method according to the invention, for example to produce steam.This steam can be used in the current or a subsequent treatment run to heat and temper the products then received in the treatment chamber 4. However, the condensate used to preheat the products is discharged via the condensate tank 5, so that the condensate pump 6 can also be used for this purpose. The condensate is discharged via a discharge flange 13, to which a disposal line (not shown) can be connected. The condensate is discharged via the discharge flange 13 by opening an actively controllable valve 14 integrated into the discharge flange 13 and closing an actively controllable valve 15 integrated into the condensate supply line 7 downstream of the discharge flange 13 (with respect to the flow direction of the condensate when supplied to the treatment chamber 4).

[0034] The process step of preheating the products using the condensate can continue until all of the condensate previously stored in the condensate tank 5 has been used. However, more condensate may be stored in the condensate tank 5 than can be reasonably used for preheating the products. In this case, it may be advantageous to drain condensate not used for preheating via a condensate drain 16 integrated into the outlet flange 10 (see Fig. 5), which also incorporates an actively controllable valve 17 for opening or closing it as needed.

[0035] The process step of preheating the products using condensate is followed by the process step of heating and tempering the products using steam. For this purpose, the steam generated in a steam generator (not shown) is introduced into the treatment chamber 4 via a steam supply 18. The steam generator can be part of the autoclave. However, an external steam generator can also be provided.

[0036] Within the treatment chamber 4, the steam is circulated by means of the fan 19, as already described for the aerosol used in the preheating of the products. Circulating the steam within the treatment chamber 4 ensures the most even exposure to the products and thus the most even heating of the products.

[0037] The process step of heating and tempering the products involves heating and tempering them using steam according to a defined temperature curve. This involves a transfer of thermal energy from the steam to the products, causing the steam to cool and at least partially condense. The resulting condensate is replaced by steam that is newly supplied to the treatment chamber 4 in a continuous or quasi-continuous process. During the heating and tempering of the products, a relatively large amount of condensate is therefore produced, which collects due to gravity on the floor of the receiving container 1 or in the floor of the treatment chamber 2.

[0038] According to the invention, this accumulating or already accumulated condensate is continuously or intermittently removed from the treatment chamber 4. This is intended to prevent, as far as possible, the transfer of thermal energy from the steam still present in the treatment chamber 4 to the condensate, which would reduce the proportion of thermal energy supplied via the steam that is transferred to the products. The condensate is removed from the treatment chamber 4 via a condensate drain 21, which is connected to an inlet flange 36 of the condensate tank 5 and into which an actively controllable valve 35 is also integrated.

[0039] The discharged condensate, which has a higher temperature than the products at the beginning of the thermal treatment (i.e. immediately after introduction into the treatment chamber 4), is therefore introduced into the condensate tank and temporarily stored there for the already described preheating of products in a subsequent treatment run.

[0040] In order to ensure that the condensate in the condensate tank 5 cools down as little as possible, the condensate tank 5 is designed to be thermally insulated, for which purpose its wall 22 is surrounded by an insulation layer 23, which can consist, for example, of a rigid plastic foam (e.g. EPS) (see Fig. 3 and 5).

[0041] The process step of heating and tempering the products is followed by the process step of targeted cooling of the products. This process step is divided into two sub-steps: pre-cooling and main cooling. For pre-cooling, a coolant, preferably water, is introduced into the treatment chamber 4 via the coolant inlet flange 12, the distribution lines 11, and the spray lines 9. A (passive) check valve 26 in the condensate supply line prevents the coolant from overflowing into the condensate tank 5.

[0042] The coolant introduced into the treatment chamber 4 during pre-cooling primarily serves to condense the steam still present in the treatment chamber 4. A relatively small amount of coolant is sufficient for this purpose. This is particularly true in conjunction with atomization of this coolant using the nozzles of the spray lines 9, which allows for the most uniform mixing possible of the steam with the atomized coolant. Pre-cooling can prevent an excessively rapid drop in process pressure within the treatment chamber 4. Furthermore, pre-cooling can cause a (gentle) initial cooling of the products with a relatively low gradient, thus avoiding thermal shock in products that are sensitive to this.

[0043] For the main cooling, relatively large quantities of coolant, preferably water, are applied as evenly as possible to the products located within the treatment chamber 4. This coolant is supplied via a coolant supply 27, which comprises three coolant supply units 28, which are arranged distributed along the length of the receiving container 1 and each comprise a coolant supply line 29 and an electric motor-driven circulation pump 30, integrated into the associated coolant supply line 29, for conveying the coolant. A design of the autoclave with only one, two, or more than three coolant supply units 28 is also possible. An end section of each of the coolant supply lines 29 is designed as a distributor 31, which opens into the treatment chamber 4 at four positions spaced apart in the longitudinal direction of the receiving container 1.Via the three coolant supply units 28, each with four openings of the associated coolant supply lines 29 into the treatment chamber 4, the coolant can be introduced into the treatment chamber 4 in a manner that is as evenly distributed as possible over the longitudinal extent of the receiving container 1.

[0044] Coolant that accumulates in the base of the treatment chamber 4 during the product cooling process step can be removed from the treatment chamber 4 via a coolant return line 32 of the coolant supply units 28. These coolant return lines 32 each open into the associated coolant supply line 29 on the suction side of the circulation pump 30, which allows the removed coolant to be returned to the treatment chamber 4 if further cooling of the still relatively warm products is possible. For this purpose, the coolant supply units 28 each comprise a plate heat exchanger 37, by means of which recooling of the returned coolant is possible using an external coolant.Furthermore, the coolant can be discharged via a drain flange 24 (with actively controllable valve 25) of the two outer coolant return lines 32 as well as via the condensate drain 21, the condensate tank 5, the condensate pump 6 and the discharge flange 13 when the process step of cooling the products is completed or at least the discharged coolant is no longer to be used for further cooling of the products.

[0045] After the targeted cooling of the products, their thermal treatment is complete, and they can be removed from the treatment chamber 4 after opening at least one of the container lids 3. A new batch of products to be thermally treated can then be introduced into the treatment chamber 4 and thermally treated in the same manner.

[0046] To achieve the greatest possible automation of the thermal treatment of products using the autoclave, the autoclave comprises a control system with a control unit 33 that controls components of the autoclave, in particular its actively controllable valves and electric motor drives. The control unit 33 can also receive signals from one or more sensors, in particular a temperature sensor 34 for determining a temperature within the condensate tank and a fill level sensor (not visible) for determining the presence and, if applicable, also a fill level of a liquid in the floor of the treatment chamber 4, and evaluate them for automation purposes.

[0047] List of reference symbols:

[0048] Receptacle

[0049] Container shell

[0050] Container lid

[0051] Treatment room a Central room of the treatment room b Side room of the treatment room

[0052] Condensate tank

[0053] Condensate pump

[0054] Condensate supply line

[0055] Condensate supply

[0056] Spray line 0 Outlet flange of the condensate tank 1 Distribution line 2 Coolant inlet flange 3 Discharge flange 4 Valve of the discharge flange 5 Valve of the condensate supply line 6 Condensate drain 7 Condensate drain valve 8 Steam supply 9 Fan 0 Partition wall 1 Condensate discharge 2 Wall of the condensate tank 3 Insulation layer of the condensate tank 4 Drain flange 5 Valve of the drain flange 6 Check valve of the condensate supply line 7 Coolant supply 8 Coolant supply unit Coolant supply line Circulation pump Distributor of the coolant supply line Coolant return line Control unit Temperature sensor Condensate discharge valve Inlet flange of the condensate tank Plate heat exchanger

Claims

Patent claims:

1. A method for the thermal treatment of at least one product by means of steam in an autoclave which comprises a receiving container (1), a steam inlet (18) and a condensate outlet (21), wherein the receiving container (1) delimits a treatment chamber (4) for receiving the product, the steam inlet (18) opens into the treatment chamber (4) and the condensate outlet (21) branches off from the treatment chamber (4), wherein in order to carry out a treatment cycle the product is positioned in the treatment chamber (1) and is subjected to steam, characterized in that condensate accumulating in the treatment chamber (1) is already discharged via the condensate outlet (21) while the product is being subjected to steam.

2. Process according to claim 1, characterized in that the condensate is discharged intermittently.

3. Process according to claim 1, characterized in that the condensate is continuously discharged.

4. Method according to one of the preceding claims, characterized in that the condensate is discharged into a collecting device.

5. Method according to claim 4, characterized in that the collecting device thermally insulates the condensate.

6. A method according to claim 4 or 5, characterized in that the condensate produced during a first treatment pass for thermally treating a first product is used to preheat a second product during a second treatment pass.

7. Autoclave for the thermal treatment of at least one product by means of steam, comprising a receiving container (1), a steam supply (18) and a condensate discharge (21), wherein the receiving container (1) has a treatment chamber (4) for receiving the product, the steam supply (18) opens into the treatment chamber (4) and the condensate discharge (21) branches off from the treatment chamber (4), characterized in that the autoclave is designed to discharge condensate accumulating in the treatment chamber (4) via the condensate discharge (21) while the product is being subjected to steam.

8. Autoclave according to claim 7, characterized by a control device which is designed for the automatic removal of the condensate which occurs.

9. Autoclave according to claim 8, characterized in that the control device comprises a control unit (33) which can actuate a valve (35) of the condensate discharge (21).

10. Autoclave according to one of claims 7 to 9, characterized in that the condensate discharge (21) opens into a collecting device.

11. Autoclave according to claim 10, characterized in that the collecting device is designed for thermal insulation of the condensate.

12. Autoclave according to claim 10 or 11, characterized in that the collecting device is fluidly connected to the treatment chamber (4) via a condensate supply (8).

Images