EP3550225B1 - Device for cooling products - Google Patents

Description

The invention relates to a device for cooling products, with a cyclone which has a housing with a circular cylinder-shaped rear section and an adjoining, conically shaped front section, with a cover on the upper end face of the rear section opposite from the front section with a cover extending concentrically through it , is arranged inside the cyclone at a distance from the cover with a circular gas outlet opening opening out gas discharge line, with a feed nozzle connected to a feed line for a cryogenic refrigerant, which opens tangentially into the rear section in the area of the upper end face, and with at least one feed line opening into the rear section for a product to be cooled.

Liquid, pasty or powdery products, in particular foods such as cake fillings, sauces and marinades, which are produced at high temperatures, often have to be cooled quickly after their production, for example in order to preserve the internal structure of the product or to counteract bacterial growth. Cooling can take place, for example, by means of electrically operated, conventional cooling units, but this is associated with a considerable use of energy. An alternative is the direct contact of the product to be cooled with a cryogenic refrigerant. The refrigerant absorbs part of the product's heat and evaporates or sublimates without leaving any residue.

In the following, “cryogenic refrigerants” are liquid, solid or gaseous media which have a temperature of -20 ° C. and below when they come into contact with the product to be cooled. In particular, the cryogenic refrigerant is a liquefied gas, such as liquid nitrogen, or carbon dioxide in solid or liquid form.

When using carbon dioxide as a cryogenic refrigerant, this is usually in liquid form under a pressure of over 5.18 bar abs. brought up and relaxed at a nozzle, the so-called relaxation nozzle, to atmospheric pressure (1 bar). The carbon dioxide cools down to one Temperature of minus 78.9 ° C (194 K), with a mixture of carbon dioxide snow and cold carbon dioxide gas. At least the carbon dioxide particles are then used to cool products and, for example, applied to the surface of a product to be cooled or - in the case of a liquid, pasty or powdery product - mixed into the product.

From the EP 1734 320 A2 a device is known in which a pumpable product to be cooled and a cryogenic refrigerant, such as liquid nitrogen, liquid carbon dioxide, liquid argon or liquid air, are brought into contact in a vortex screw cooler and are thoroughly mixed. The mixture is then fed to a separating device where the vaporized cryogenic refrigerant is drawn off. The cooled product is then ready for processing in further processes or for packaging.

From the WO 2005/053440 A1 a device for cooling liquid products is known in which a cryogenic refrigerant, for example liquid nitrogen or liquid carbon dioxide, is introduced into a container filled with the product to be cooled. The refrigerant evaporates on thermal contact with the product and is drawn off at a head space of the container. After the cooling process, the cooled product is removed via a line branching off from the bottom of the container.

The WO 2016/060869 A1 relates to a device for cooling liquid food such as sauces. With this item, the product is led through a pipe into which a cryogenic refrigerant, for example liquid nitrogen, is introduced at one or more points. The device described is, however, very complex in structure, especially since the refrigerant, which expands rapidly when it evaporates, requires the pipeline to be pressure-stable.

In the EP 3 234 485 A1 describes a process in which a product to be cooled is brought into contact with expanding carbon dioxide in a cyclone. A mixture of solid carbon dioxide particles and the product is formed, which is drawn off from an outlet opening arranged in the bottom area of the cyclone becomes. However, the brief contact between the product and carbon dioxide particles only leads to a comparatively slight cooling of the product.

The DE 10 2014 018981 A1 also relates to a method for producing supercooled carbon dioxide snow, in which liquid carbon dioxide is introduced into an expansion chamber at an expansion nozzle, where it is expanded to form a mixture of carbon dioxide gas and carbon dioxide snow, and then the mixture into a predominantly carbon dioxide snow and a predominantly carbon dioxide gas existing phase is separated.

The invention is therefore based on the object of specifying an efficient and easy-to-use possibility for cooling flowable, in particular liquid or powdery products.

This object is achieved by a device with the features of claim 1 and by a method using a device according to the invention with the features of claim 5.

Advantageous embodiments are specified in the subclaims.

According to the invention, a device of the type and purpose mentioned at the beginning is characterized in that the outlet opening of the front section is flow-connected to a product outlet for cooled product, in which means are arranged for building up a counter-pressure that counteracts the flow pressure of the product flowing out through the product outlet.

The device according to the invention thus comprises a cyclone, the housing of which has, in a manner known per se, a cylindrical rear section and an adjoining, conically shaped front section which opens into an outlet opening. On the opposite end of the rear section from the front section there is a cover with a gas discharge line (also called an immersion tube) which passes through it and opens inside the cyclone at a distance from the cover with a gas outlet opening. The cyclone is usually vertical, with the outlet opening of the front section pointing downwards and the gas outlet opening pointing upwards. A feed line for a refrigerant opens tangentially into the rear section of the cyclone and is equipped with a nozzle opening at the end. Furthermore, a feed line for feeding in a product to be cooled opens into the rear section. For example, the feed line for the product opens into the rear section essentially perpendicularly or at an acute angle to the direction of flow of the refrigerant and at a distance from the nozzle opening of the Supply line for the refrigerant. In order to prevent the product from freezing onto the walls of the cyclone, they can be equipped with a heating device, for example an electrical one.

When the device is in use, a considerable flow pressure is exerted in the cyclone in the direction of the outlet opening of the front section due to the supply of the refrigerant and its expansion and / or evaporation. Surprisingly, it has now been found that particularly efficient cooling of the product can be achieved if a certain counterpressure is built up against this flow pressure. The cause of the increase in cooling performance has not been fully clarified; the counter pressure may lead to the product staying longer in the cyclone and thus to a longer contact time with the cryogenic refrigerant. The invention therefore provides that means for generating such a counterpressure are arranged in a product discharge line adjoining the outlet opening.

The means for building up a counterpressure include flow resistances within the product discharge, such as an aperture or other narrowing of the free flow cross-section. In one embodiment, they comprise a throttle valve, by means of which a specific counterpressure to be achieved can be set. This embodiment is particularly recommended when different products are to be cooled in the device and a certain cooling capacity is required, depending on the type and properties of the product, such as temperature or viscosity and / or the temperature to be set. The throttle valve can also be designed so that it can be regulated and, during the cooling process, a counter pressure can be regulated as a function of a measured parameter, such as the temperature of the product on the outlet side.

In another embodiment, the means for building up the counterpressure comprise a section of the product discharge, which is designed in the manner of a siphon and comprises at least one line section that extends geodetically upwards. When the device is in operation, a line section consisting of cooled product is formed in the line section running vertically upwards Column whose weight (for liquid products: hydrostatic pressure) acts as a counter pressure against the flow pressure at the outlet opening of the cyclone. Of course, the means for building up a counterpressure can also be combined with one another, for example an orifice or a throttle valve in the product feed line with a line section running vertically upwards.

A particularly advantageous embodiment of the invention provides that the feed line for the product to be cooled opens into the rear section in such a way that a product flow flowing out of it is directed into the flow of the refrigerant introduced at the feed nozzle. As a result, an intimate mixing of product and refrigerant is achieved immediately after the product has been supplied.

The product is preferably introduced via a feed line which opens perpendicularly to the refrigerant flow and which is guided, for example, through the cover of the rear section and at least with its end section runs essentially parallel to a longitudinal axis of the cyclone. In this case, the product is thus introduced into the cyclone essentially perpendicular to the direction of flow of the refrigerant. The feed line for the product can, however, also open into the rear section at an acute angle, with one directional component each parallel and perpendicular to the refrigerant flow. In addition, the feed line for the product can also be equipped with a spray nozzle on the mouth side.

In a particularly advantageous embodiment of the invention, the feed line for the product does not open into the rear section immediately in front of the feed nozzle for the refrigerant, but rather at an axial distance from it. The feed line for the product preferably opens into the rear section 1 cm to 10 cm in front of the feed nozzle, particularly preferably 2 cm to 5 cm. In this embodiment, the product flow encounters an already widened refrigerant flow and is entrained by it.

The object of the invention is also achieved with a method for cooling products, using a device according to the invention, with the Features of claim 5 solved. One of them is in the rear section
a feed nozzle opening into a cyclone tangentially introduces a cryogenic refrigerant into the cyclone. At the same time, a product to be cooled is supplied in a product flow directed towards the flow of the refrigerant introduced. The mixture of refrigerant and product is separated in the cyclone, with the product being discharged via a product discharge line which opens out from a conically shaped front section adjoining the rear section. Evaporated refrigerant is discharged via a gas discharge line in the rear section of the cyclone.

According to the invention, a counterpressure that counteracts the flow pressure of the outflowing product is generated in the product discharge on the downstream side. The back pressure is set to a predetermined value by means of suitable means or is regulated as a function of a measured value. For example, a throttle valve or a constriction in the product discharge or the maintenance of a liquid column, against the hydrostatic pressure of which the cooled product has to flow out, can be used as means. By applying the counter pressure, the flow conditions inside the cyclone are changed in such a way that there is a longer contact time between product and refrigerant and thus more efficient cooling of the product.

The counter pressure is set to a value of 0.03 to 0.2 bar, particularly preferably to a value between 0.05 and 0.1 bar. The cryogenic refrigerant used is preferably liquid nitrogen or liquid carbon dioxide, which when entering the cyclone decomposes to form a mixture of gaseous and solid carbon dioxide.

The method according to the invention and the device according to the invention are suitable for cooling liquid, fluidized or powdery products. In particular, the device according to the invention is used for cooling food products based on fat or water, in particular liquid food products such as sauces, soups or juices, with or without solid constituents. After cooling in the device according to the invention, the product can then undergo further processing steps or one Packaging unit are supplied. The gaseous refrigerant produced during the cooling process, for example carbon dioxide gas, is drawn off at the gas discharge line and can, for example, also be used to precool the refrigerant fed to the cyclone.

Example:

• The rear section of the cyclone of a device according to the invention has a tube diameter of, for example, 250 mm to 300 mm. An aqueous product with a flow rate of between 2.5 m ³ / h is introduced into the rear section.
• At the same time, liquid carbon dioxide is introduced as a refrigerant with a flow rate of 1.2 t / h. In the product discharge, a back pressure between 0.05 bar and 0.1 bar is generated, for example, by means of a throttle valve. The product withdrawn at the product discharge outlet has a temperature that is up to 40 ° C. lower than the temperature of the product fed in.

• Fig. 1: Eine erfindungsgemäße Vorrichtung in einer Schnittansicht längs der Linie I-I in Fig. 2,
• Fig. 2: Die Vorrichtung aus Fig. 1 in einer Schnittansicht längs der Linie II-II in Fig. 1,

An exemplary embodiment of the invention will be explained in more detail with the aid of the drawing. In schematic views show:

• Fig. 1 : A device according to the invention in a sectional view along the line II in FIG Fig. 2 ,
• Fig. 2 : The device off Fig. 1 in a sectional view along the line II-II in Fig. 1 ,

The device 1 shown in the drawings for cooling products comprises a cyclone 2, the housing of which has, in a manner known per se, a rear section 3 with a circular cylindrical cross-section with a radius Rz and an adjoining, conically shaped front section 4, which in an outlet opening 5 with Radius Rp empties. The cyclone 2 is made of a poorly thermally conductive material, such as stainless steel or titanium, and can moreover be equipped with a thermally insulating cover, not shown here.

On its end face opposite the front section 4, the rear section 3 is closed with a cover 6. A cylindrical gas discharge pipe 7 with an inner radius R _G , which is connected to a gas discharge line in a manner not shown here, is passed through the center of the cover 6, _{whereby there is an annular space 8 of width B R} between the outer wall of the gas discharge pipe 7 and the inner wall of the rear section 3. The gas discharge pipe 7 is led deep into the interior of the cyclone 2 and ends with a gas outlet opening 11 approximately at the level 12 of the transition between the rear section 3 and the front section 4 of the cyclone 2. The rear section 3, the front section 4 and the gas discharge pipe 7 are along a A common vertical axis 9 is arranged, the outlet opening 5 being arranged at the bottom and the gas discharge pipe 7 being arranged at the top of the cyclone 2. For example, the radius Rz is between 10 cm and 15 cm, the radius R _G between 5 cm and 10 cm and the radius R _P between 5 cm and 10 cm.

A feed nozzle 14 for a cryogenic refrigerant opens into the rear section 3 of the cyclone 2, which is flow-connected via a feed line 15 to a source for a cryogenic refrigerant, not shown here. The source is, for example, a tank for cryogenic liquefied nitrogen or for pressure liquefied carbon dioxide. An end section of the feed line 15, on the end face of which the feed nozzle 14 is located, is arranged within a tangential feed section 16 of the cyclone 2 and axially to this. A flange connection 17 ensures a gas-tight connection between feed line 15 and feed section 16.

Furthermore, a product feed line 18 is provided which opens into the rear section 3 at an outlet opening 19 in the cover 6 vertically or at an angle, with an additional tangential directional component. The outlet opening 19 is arranged in such a way that it is aligned with the end section of the feed line 15 and opens out in front of the feed nozzle 14 at a distance D of, for example, 2 cm to 5 cm.

The outlet opening 5 of the front section 4 is followed by a product discharge line 20 for discharging cooled product, which in the exemplary embodiment shown here has a continuous cross-sectional _{radius R P} which corresponds to the radius of the outlet opening 5 of the cyclone. The product discharge 20 has in the manner of a siphon a U-shaped line section which, when the device 1 is in use, geodetically downwards with a bend 21 and with its Legs 22, 23 are directed upwards, with the leg 22 directly adjoining the outlet opening 5. Elbow 21 and legs 22, 23 of the U-shaped line section are dimensioned in such a way that a liquid column of height H of, for example, 500 mm to 800 mm can be maintained in it.

During operation of the device 1, a cryogenic refrigerant, for example pressure-liquefied carbon dioxide, flows through the feed line 15 at a pressure of more than 5.18 bar (abs.), For example a pressure between 18 to 20 bar (abs.), To the feed nozzle 14 is introduced into the cyclone 2. At the feed nozzle 14, the carbon dioxide expands to form a stream of carbon dioxide gas and carbon dioxide snow, which flows tangentially into the annular space 8 between the inner wall of the rear section 3 and the outer wall of the gas discharge pipe 7 and is there forced onto a spiral-shaped path 25 that descends in the direction of the front section, as in Fig. 2 indicated. Instead of carbon dioxide, another cryogenic refrigerant, such as liquid nitrogen, can also be used.

At the same time as the refrigerant, a liquid product to be cooled is supplied via the product feed line 18. Before the outlet 19, the product mixes intimately with the refrigerant introduced from the feed nozzle 14 and is entrained by its flow. The refrigerant absorbs heat from the product and at least partially evaporates or sublimates, with the product cooling down.

In a manner known per se, the spiral path 25 of the evaporated refrigerant transforms at the level of the gas outlet opening 11 into a spiral path ascending within the gas discharge pipe 7. The gaseous refrigerant escaping at the gas discharge pipe 7 is then preferably collected and used, for example, to precool the supplied refrigerant in the supply line 15. Due to the circular flows within the cyclone 2, the liquid droplets or particles of the product are thrown against the inner wall of the conical front section 4 at the latest after a few revolutions due to the centrifugal force and decelerated to the extent that they detach from the flow and down towards the outlet opening 5 to run. The Liquid product is then discharged via the U-shaped line section of the product discharge line 20.

The supply and expansion of the refrigerant in the cyclone 2 leads to a strong flow pressure of the product in the direction of the product outlet 20. When flowing out via the product outlet 20, however, the product must pass the leg 23 of the U-shaped line section and thus a hydrostatic pressure corresponding to the height H. which acts as a back pressure to the flow pressure of the product. The counter pressure of, for example, 0.05 bar to 0.08 bar leads to a longer average contact time of the liquid droplets of the product with the refrigerant and thus to a significantly greater cooling of the product compared to a discharge led directly downwards. In addition, the device 1 according to the invention is also suitable in the same way for cooling a powdery product.

List of reference symbols

1.

contraption

2.

cyclone

3.

Rear section

4th

Front section

5.

Outlet opening

6th

cover

7th

Gas exhaust pipe

8th.

Annulus

9.

axis

10.

-

11.

Gas outlet opening

12th

level

13th

-

14th

Feed nozzle

15th

Supply line

16.

Feed section

17th

Flange connection

18th

Product supply line

19th

Outlet opening

20th

Product rejection

21.

Elbow

22nd

leg

23

leg

24

-

25th

train

Bz

Width of the annular gap

RG

Inner radius of gas discharge

Rp

Inner radius product rejection

Margin no

Inner radius of the rear section of the cyclone

H

Height of a column of liquid in the product discharge

D.

Distance between feed nozzle and product feed line

Claims (7)

1. Apparatus for cooling products, having a cyclone (2) which has a housing with a circular-cylindrical rear section (3) and with a conically shaped front section (4), adjoining said rear section, with an outlet opening (5), wherein, at the upper face side, opposite the front section (4), of the rear section (3), there is arranged a cover (6) which has a gas extraction line (7) passed through it in a concentric manner and which opens out in the interior of the cyclone (2) by way of a circular gas outlet opening (11) in a manner spaced apart from the cover (6), having a supply nozzle (14) which is connected to a feed line (15) for a cryogenic refrigerant and which opens into the rear section (3) in the region of the upper face side in a tangential manner, and having at least one feed line (18) for a product to be cooled, which at least one feed line opens into the rear section (3),
   characterized
   in that the outlet opening (5) of the front section (4) is connected in terms of flow to a product discharge line (20) for cooled product, in which product discharge line means (21, 22, 23) for building up a counterpressure acting counter to the flow pressure of the product flowing away through the product discharge line (20) are arranged, wherein
   the means (21, 22, 23) for building up a counterpressure comprise a throttle valve or an orifice plate and/or a geodetically upwardly extending line section (23) of the product discharge line (20), in which line section a liquid column whose hydrostatic pressure acts as counterpressure can be built up during operation of the apparatus.
2. Apparatus according to Claim 1, characterized in that the feed line (18) for the product opens into the rear section (3) in such a way that a product stream flowing from said feed line is directed into the stream of the refrigerant introduced at the supply nozzle (14).
3. Apparatus according to either of the preceding claims, characterized in that the feed line (18) for the product opens into the rear section (3) of the cyclone (2) in a manner axially spaced apart from the supply nozzle (14) for the refrigerant.
4. Apparatus according to one of the preceding claims, characterized in that the feed line (18) for the product is arranged, at least with its end section opening into the cyclone (2), in a manner substantially parallel to a longitudinal axis (9) of the cyclone (2).
5. Method for cooling products using an apparatus according to one of the preceding claims, in which method a cryogenic refrigerant is introduced in a tangential manner into the rear section (3) of the housing of a cyclone (2) at a supply nozzle (14), a product to be cooled is introduced, via a feed line (18) opening into the cyclone (2), into the stream of the refrigerant introduced and is mixed therewith, and subsequently the mixture of refrigerant and product is separated in the cyclone (2), wherein the product is discharged via a product discharge line (20) which opens out from a conically shaped front section (4) connected to the rear section (3), and evaporated refrigerant is discharged via a gas extraction line (7) opening into the rear section (3),
   characterized
   in that a counterpressure acting counter to the flow pressure of the product flowing away is generated in the product discharge line (20) on the outflow side, wherein the counterpressure is set to a value of 0.03 to 0.2 bar, preferably of between 0.05 and 0.1 bar.
6. Method according to Claim 5, characterized in that liquid carbon dioxide or liquid nitrogen is used as cryogenic refrigerant.
7. Method according to either of Claims 5 and 6, characterized in that the product is a liquid or pulverulent product.

Images