WO1989012574A1

WO1989012574A1 - Plant for treatment, e.g. heat treatment, of a liquid flowing through a tube of flexible material

Info

Publication number: WO1989012574A1
Application number: PCT/SE1989/000316
Authority: WO
Inventors: Torbjörn BERNDT; Björn WERNERSSON
Original assignee: Ab Tetra Pak
Priority date: 1988-06-14
Filing date: 1989-06-05
Publication date: 1989-12-28
Also published as: AU3833589A; SE8802217D0

Abstract

In a plant a liquid is treated while flowing through a tube (10) of flexible material, which in turn is moved in the flow direction of the liquid through first and second channels (1, 2) coupled in series. In the channels (1, 2) the flexible tube (10) is surrounded by liquid flowing in the same direction as the liquid within the flexible tube (10). The flexible tube (10) is transferred from one of the channels to the other through a passage in a transferring device (3), which passage has a cross-section which as to form and size substantially coincides with the cross-section of the flexible tube (10), when this is situated in the passage. While the flexible tube is moved between said one channel (1) and the passage, it is surrounded by perforated walls forming a transferring channel, liquid around the flexible tube being gradually discharged from the transferring channel along a substantial part of its extension.

Description

Plant for treatment, e.g. heat treatment, of a liquid flowing through a tube of flexible material

The present invention relates to a plant for treatment of a liquid flowing through a tube of flexible material, while the tube having a cross-section deviating from a circular form is moved in the flow direction of the liquid through first and second channels coupled in series, which plant comprises first and second means forming the respec¬ tive channels and giving them a cross-section of substantially the same form but larger than the cross-section of the tube present therein, means arranged for supply of liquid to the first channel, so that the liquid will flow therethrough around the flexible tube in the moving direction of the tube, means arranged for discharge of liquid from the first channel at the end thereof situated closest to the second channel, and means arranged for supply of liquid to the second channel at its end situated closest to the first channel.

In the following the present invention will be described in connection with a plant for heat treating of a liquid, which flows through a tube of flexible material in the above described manner, by means of other liquids caused to flow around the flexible tube while this is moved through the above mentioned channels. However, the invention is not limited to a plant for particularly heat treatment of the liquid in the flexible tube or limited to accomplishment of the treatment of this liquid by means of the liquids caused to flow around the flexible tube through the channels. Thus, the invention is principally applicable even in connection with a plant arranged for another kind of treatment, such as radiation treatment, of a liquid in a flexible tube, which treatment per se does not concern the liquids flowing around the flexible tube.

A known plant of the kind in question is described schematically in a report that was published by Mr Lennart Stenstrom at a conference in Princeton, USA, in 1983, "First International Conference on Aseptic Packing - ASEPTIPAC 83". The plant described in the report is based on an invention described in US-A-3.913.299. When a plant of the defined kind should be designed it has proved difficult to construct the initially mentioned means for discharge of liquid from the first channel and for supply of liquid to the second channel.

Thus, it has proved difficult to avoid that the tube of flexible material owing to the pressure of the liquid enclosed therein expands at the outlet for discharge of Liquid from the first channel and blocks this outlet. Further, it has proved difficult during the operation of the plant to prevent an undesired overflow of liquid from one channel to. the other around the tube of flexible material.

The object of the present invention is to provide in a plant of the initially described kind a solution of the problems connected with the liquid discharge from the first channel and the liquid supply to the second channel.

This object can be achieved in a way such that a transferring device forms a passage for the flexible tube between the channels, which passage has a cross-section that to its form and size substantially coincides with the cross-secton of the flexible tube when this is situated in the passage, that walls surrounding the flexible tube in an area between the first channel and said passage form a transferring channel, which at one of its ends has substantially the same cross-section as the first channel and at its other end has substantially the same cross-section as the passage, said walls further having oulet openings for liquid around the tube, which are distributed around all of the transferring channel as well as along the same between the first channel and the passage, that said means for discharge of liquid from the first channel communicates with the first channel through said outlet openings and that the outlet openings have a total outflow area per unit of length of the transferring channel dimensioned such that a gradual outflow of liquid is obtained through the outlet openings along a substantial part of the transferring channel. By construction of the plant in this way it can be prevented that the flexible tube is expanded so that it prevents outflow of liquid from the first channel. In spite of this, the flexible tube may be used such that it seals against said transferring device and prevents liquid around the tube from flowing over from one channel to the other.

In a preferred embodiment such transferring device comprises an unper- forated pipe having stiff walls, which pipe forms said passage and extends a distance along the flexible tube. By means of such an unper- forated pipe a better sealing may be provided between said first and second channels.

The flexible tube may be allowed to adopt any desired cross-sectional form in said passage, which can thus be given different cross-sectional forms. It is an advantage if the cross-section of the passage is substan¬ tially of the same size as the cross-section adopted by the flexible tube in the passage. However, the cross-section of the passage may be allowed to be somewhat larger than that of the tube, if there are means for main¬ taining the liquid pressures substantially alike on the two sides of the passage, seen in the moving direction of the tube.

The transferring channel may be made in different lengths depending on the magnitude of the liquid flow that should leave the first channel through said outlet openings. The larger this flow is the longer the transferring channel has to be made, i.e. the longer the distance has to be over which the outlet openings are distributed. By dimensioning of the outlet openings in a way such that outlet openings situated after each other allow outflow only of part of the liquid flowing through the trans¬ ferring channel around the flexible tube, a required overpressure may be maintained of the liquid in the transferring channel, i.e. in the area of the outlet openings. Thereby, it is prevented that the flexible tube - as a consequence of the pressure of the liquid therein - is expanded such that it closes the outlet openings. As mentioned above the flexible tube in principle may be allowed to adopt any desired cross-section during its transport though the transferring channel and the passage. If the flexible tube has a flattened form, the transferring channel preferably, however, is formed such that the opposing walls situated opposite to the respective flat sides of the flattened flexible tube converge towards said passage. Thereby, the flexible tube may maintain its flattened form in the transferring channel and in the passage. The unperforated pipe forming part of said trans¬ ferring device preferably constitutes a direct continuation of the per- forated walls of the transferring channel.

The invention is described in the following with reference to the accompanying drawing, in which fig 1 shows a plant according to the invention and fig 2 shows a certain part of the plant in fig 1. Figs 3 and 4 show cross-sections along the lines III-III and IV-IV, res¬ pectively, in fig 2.

The plant in fig 1 comprises two flattened pipes 1 and 2, which are interconnected by means of a transferring device 3. The pipe 1 has a vertical part and a horizontal part. The vertical part is connected with a supply member in the form of a funnel 4, and the horizontal part through the transferring device 3 is connected with one end of the pipe 2, which in its entirety extends horizontally. The other end of the pipe 2 through a transferring device 5 is connected with a discharge device comprising a tube-formed discharge member 6.

The pipes 1 and 2 and the transferring devices 3 and 5 form a tunnel, the inlet of which is situated in the funnel 4 and the outlet of which is situated in the discharge member 6-

Through said tunnel a tube of flexible material containing a liquid to be heat treated in the plant is to be moved. The liquid is to flow through the flexible tube while the latter moves through the plant. In the drawing there are shown two rolls 7, 8 with a belt-formed flexible material and means 9 for continuous welding together of the belts leaving the rolls, so that a tube 10 is formed. Into the tube 10 thus formed there is extending from above a supply pipe 11 for liquid to fill the tube and flow therethrough.

At the outlet end of the discharge member 6 outside thereof there is a means (not shown) for cross-sealing of the liquid filled tube 10 at even intervals as this leaves the discharge member 6. By such a cross- sealing separate portions of liquid are obtained within the tube 10, as shown at 12.

During operation of the plant the whole of the tunnel formed by the pipes 1 and 2 and the transferring devices 3 and 5 should be filled up with liquid around the flexible tube 10. This liquid during the movement through the tunnel of the tube 10 should move in the same direction as the tube 10. For this purpose the plant comprises a first pump 13, which with its suction side through a conduit 14 is connected to said trans¬ ferring device 3 and which with its pressure side through a conduit 15 is connected to the funnel 4. Further, a second pump 16 is connected with its suction side through a conduit 17 to the transferring device 5 and with its pressure side through a conduit 18 connected to the transferring device 3.

In the transferring device 3 there is a passage connecting the interior of the pipe 1 with the interior of the pipe 2 and, preferably, having a smaller cross-sectional area than that of the interior of both pipes 1 and 2. The described conduits 14 and 18 are connected to the transferring device 3 at the respective sides of the passage therein.

Also the transferring device 5 may have a passage for the flexible tube 10, which passage has a smaller cross-sectional area than that of the interior of the pipe 2. The conduit 17 in that case is connected upstream of this passage.

The discharge member 6, the interior of which constitutes a continuation of the tunnel through the pipes 1 and 2, has a discharge opening 19, the size of which substantially coincides with that of the cross-section of the liquid filled tube 10. Below the opening 19 there is a container 20 for receiving liquid leaking out through the discharge opening 19.

A third pump 21 with its suction side, through a conduit 22, communicates with the interior of the container 20 and with its pressure side, through a conduit 23, communicates with the interior of the discharge member 6. Through a conduit 24 a container 25 containing liquid is also connected to the discharge member 6. A free liquid surface in the container 25 is substantially larger than the cross-sectional area in said tunnel (around the pipe 10) and is situated at a higher level than the outlet opening 19 in the outlet member 6.

As indicated in the drawing, a free liquid surface is maintained at a certain level in the funnel 4 around the flexible tube 10. A free liquid surface is maintained at about the same level within the flexible tube 10 in the area of the opening of the supply pipe 11. The liquid surface in the container 25 is situated at a lower level than the liquid surface in the funnel 4 during operation of the plant.

Thus, one liquid body is maintained in the funnel 4 at the tunnel inlet and one liquid body is maintained in the discharge member 6 at the tunnel outlet, the liquid pressure being larger at the tunnel inlet than at the tunnel outlet.

A sensing and control unit 26 is arranged to sense the position of the liquid surface in the funnel 4 and to control through a connection 27 the capacity of the pump 21 in a way such that the liquid surface in the funnel 4 is maintained at a predetermined level.

The conduit 15 extends through a first heat exchanger 28 having a supply pipe 29 and a discharge pipe 30 for a heating medium. The conduit 18 extends through a second heat exchanger 31 having a supply pipe 32 and a discharge pipe 33 for a cooling medium. Liquid being pumped through the conduit 15 by means of the pump 13 will thus be heated in the heat exchanger 28 and will then, while it flows further on through the pipe 1, heat liquid situated within the flexible tube 10. The pipe 1 forms a heating zone Zl.

Correspondingly, the pipe 2 forms a cooling zone Z2, in which the liquid in the flexible tube 10 is again cooled. Liquid circulated by means of the pump 16 through the pipe 2 and the conduits 17 and 18 will thus be cooled in the heat exchanger 31 and will then cool liquid within the flexible tube 10.

The plant operates in the following manner.

Liquid to be heat treated in the plant is supplid continuously through the inlet pipe 11. Within the flexible tube 10, that is continuously formed in a manner described before and is moved downwards within the funnel 4, there is formed a free liquid surface in the area of the opening of the inlet pipe 11.

Simultaneously, liquid is circulated by means of the pump 13 through the conduit 15, the heat exchanger 28, the pipe 1 and the conduit 14, so that the liquid filled flexible tube 10 is surrounded by heating liquid all the time while it is moved through the pipe 1, i.e. the heating zone Zl. In the same manner liquid is circulated by means of the pump 16 through the conduit 18, the heat exchanger 31, the pipe 2 and the conduit 17, so that the liquid filled flexible tube 10 is surrounded by cooling liquid all the time while it is moved through the pipe 2, i.e. the cooling zone Z2.

Also the discharge member 6, through which the liquid filled flexible tube 10 is moved, is filled with liquid. A continuous liquid body is formed by the liquid in the discharge member 6 and the liquid in the container 25. Liquid in the discharge member 6 has no thermal function in the plant, however. Depending upon which heat treatment is desired of the liquid supplied through the inlet pipe 11 the capacities of the pumps 13 and 16 are set at desired values, among other things with respect to the chosen flows and temperatures in the conduits 29 and 32. Depending upon the set capacities of the pumps 13 and 16 there is formed a free liquid surface at a certain level in the funnel 4. This level is sensed by means of the sensing and control unit 26, which controls the capacity of the pump 21, so that a predetermined liquid pressure is maintained in the dis¬ charge member 6. At an unchanged capacity of the pumps 13 and 16 an un- changed liquid pressure in the discharge member 6 means that the liquid surface in the funnel 4 is maintained at a desired level.

This means that the pump 21 will continuously supply to the discharge member 6 the same amount of liquid that leaves the same through the outlet opening 19. In other words, despite the fact that liquid is continuously accompanying the flexible tube 10 out through the outlet opening 19, an unchanged liquid pressure can be maintained within the discharge member 6.

By the above described arrangement it is automatically achieved that the liquid pressure in the pipe 1 immediately upstream of the passage in the transferring device 3 becomes substantially the same as the liquid pressure in the pipe 2 immediately downstream of the passage in the transferring device 3. This means that substantially no liquid at all flows through the passage in the transferring device 3 outside the flexible tube 10.

Even at both sides of the transferring device 5 the liquid pressures are maintained substantially alike, so that substantially no liquid at all passes out or in through the opening of the pipe 2 in the discharge member 6.

In this manner stable pressure relations are obtained in both zones Zl and Z2. Further, it is avoided that heating liquid from the zone Zl is mixed with cooling liquid from the zone Z2. The purpose of the container 25 is that undesired pressure variations in the discharge member 6 should be as small as possible and rapidly be evened out during operation of the plant.

Already in the discharge member 6 but above all outside thereof the flexible tube 10 is allowed to expand, before separate liquid portions are formed therein by the above mentioned cross-sealing thereof. This means that liquid within the flexible tube moves faster than the tube itself through the two heat treatment zones Zl and Z2.

The movement of the flexible tube 10 through the plant is accomplished substantially by the flow of liquid taking place within as well as out¬ side the tube 10 in the zones Zl and Z2. In other words, the flowing liquids entrain the flexible tube 10 forwards and through the plant. If needed, auxiliary transport means may be arranged after the discharge member 6. For instance, said means for cross-sealing of the flexible tube 10 may be arranged also to exert traction thereon.

In the plant shown in fig 1 the liquid flow through the flexible tube 10 is accomplished by means of only gravity. For avoiding that the plant should have to be made unnecessarily high only for accomplishing of a desired liquid flow through the tube 10, the funnel 4 and part of the supply pipe 11 and possibly the rolls 7, 8 and the sealing means 9 may be arranged in a closed space, in which there is maintained a super- atmospheric pressure allowed to act on the free liquid surfaces in the funnel 4 and the flexible tube 10.

Upon need the liquid flow through the flexible tube 10 may be accomp¬ lished by means of a hose pump of the kind shown in US-A-3.913.299.

Fig 2 shows a transferring device 3 according to fig 1, partly in sec¬ tion. The transferring device comprises a housing 34 having a vertical partition 35 with a horizontal slot for the passage of the flattened flexible tube 10. The partition 35 separates within the housing 34 two chambers 36 and 37. The chamber 36 communicates with the interior of the pipe 1 and through outlets 38a, 38b with the suction conduit 14 of the pump 13 (fig 1) and constitutes consequently an outlet chamber for liquid having flowed through the pipe 1. The chamber 37 communicates through inlets 39a, 39b with the pressure conduit 18 of the pump 16 (fig 1) and with the interior of the pipe 2 and constitutes consequently an inlet chamber for liquid to flow through the pipe 2.

Within the outlet chamber 36 there are extending two perforated plane plates 40 and 41 on both sides of the flexible tube 10 from the area, where the housing 34 is connected with the pipe 1, to the partition 35. The plates 40 and 41 converge in the intended movement direction of the flexible tube 10 and form an inlet opening for the flexible tube 10, which has the same size as the cross-sectional area of the interior of the pipe 1, and an outlet opening of the same size as the slot in the partition 35. The plates 40 and 41, further, are somewhat narrower than the housing 34, whereby the space above the plate 40 and the space below the plate 41 communicate with each other and with the space between the plates 40 and 41 at the side walls of the housing.

As illustrated by means of arrows in fig 2, liquid is intended to flow from the interior of the pipe 1 through the holes in the perforated plates 40 and 41 and through the side slots between the plates 40 and 41 out into the upper and lower parts of the outlet chamber 36 and from there out through the outlets 38a and 38b.

In the inlet chamber 37 two parallel plates 42 and 43 extend from the partition 35 towards the pipe 2 as a direct continuation of the respec- tive plates 40 and 41. Between the plates 42 and 43 a passage for the flexible tube 10 is formed, which passage has the same cross-section as the slot in the partition 35.

The plates 42 and 43 end up at same distance from the area, where the housing 34 is connected with the pipe 2. As a continuation of the pipe 2 two flanges 44 and 45 extend into the inlet chamber 37. somewhat past the free ends of the plates 42 and 43. Between the end portions of the plates 42 and 43 and the flanges 44 and 45 there are formed an upper slot 46 and a lower slot 47, through which slots the inlet chamber 37 communicates with the interior of the pipe 2. The flanges 44 and 45 and the plates 42 and 43 are formed such that liquid flowing out from the inlet chamber 37 through the slots 46 and 47 will get a flow direction substantially coinciding with the movement direcion of the flexible tube 10.

As illustrated by means of arrows in fig 2, liquid supplied through the inlets 39a and 39b is intended to flow through the inlet chamber 37 and through the slots 46 and 47 to the interior of the pipe 2.

The transferring device 3 according to fig 2 is intended to operate in the following manner.

While liquid is flowing around the flexible tube 10 from the left within the tube 1 and in between the perforated plates 40 and 41, the flexible tube is moving in the same directon and further through the slot in the partition 35 and the passage between the plates 42 and 43. Within the flexible tube 10 a liquid is flowing with a speed larger than that by which the flexible tube is moving.

Liquid around the flexible tube gradually flows out through the perfora- tions of the plates 40 and 41 and through the side slots between these plates. The total outflow area per unit of length of the plates 40 and 41 is chosen with respect to the gradually decreasing distance between the plates such that the liquid between the flexible tube 10 and the plates will undergo a gradual pressure drop during its flow along the plates, which pressure drop does not deviate too much from the pressure drop in the liquid flowing within the flexible tube 10. In this way it is avoided that the walls of the flexible tube are pressed by the liquid therein to abutment against the plates 40 and 41 such that their perforations are blocked. As can be seen from fig 2, it may prove suitable for the achievement of the best result that the perforations have a size gradually increasing in the movement direction of the flexible tube 10, whereas the side slot between the plates 40 and 41 is narrowing.

In the shown example the size of the slot in the partition 35, as well as the size of the passage between the plates 42 and 43, is chosen such that the flexible tube 10 expands somewhat from its shape in the pipe 1. However, after it has left the plates 42 and 43 and enters the pipe 2 the flexible tube 10 will regain its form that it had in the pipe 1.

As mentioned above in connection with fig 1, the same liquid pressures are maintained on both sides of the passage in the transferring device 3 for the flexible tube 10. This means that no liquid is transferred between the chambers 36 and 37. Such transferring of liquid is counter¬ acted also by the condition that the walls of the flexible tube 10 are pressed by the enclosed liquid to sealing abutment against the plates 42 and 43, respectively, during their passage therebetween.

Fig 3 is a cross-section along the line III-III in fig 2 and shows the flexible tube 10 when it is situated in the pipe 1. Fig 4 is a cross- section along the line IV-IV in fig 2 and shows the flexible tube 10 when it is situated in the passage between the plates 42 and 43.

As can be seen from fig 3, the interior of the pipe 1 has a cross-section that is substantially larger than the cross-section of the flexible tube 10, but which has substantially the same form as that. As can be seen from fig 4, the flexible tube 10 has expanded somewhat from its shape according to fig 3 and substantially fills out the passage between the - plates 42 and 43. Filler pieces 48 and 49 may be arranged along the side walls of the housing 34 preventing undesired liquid flow along the flexible tube 10 outside thereof in the passage between the plates 42 and 43.

It is also evident from fig 3 and 4 that the passage between the plates 42 and 43 has a smaller cross-sectional area than the interior of the pipe 1.

Claims

1. Plant for treatment of a liquid flowing through a tube (10) of flexible material, while the tube having a cross-section deviating from a circular form is moved in the flow direction of the liquid through first and second channels coupled in series, which plant comprises

- first and second means (1, 2) forming the respective channels and giving these a cross-section having substantially the same shape as but being larger than the cross-section of the tube (10) situated therein,

- means (13, 15) arranged for supply of liquid to the first channel, so that liquid flows therethrough around the flexible tube (10) in the movement direction of the tube,

- means (14) arranged for discharge of liquid from the first channel at the end thereof situated closest to the second channel, and

- means (16, 18) arranged for supply of liquid to the second channel at the end thereof situated closest to the first channel,

c h a r a c t e r i z e d i n

- that a transferring device (3) forms a passage for the flexible tube (10) between the channels, which passage has a cross-section, which as to form and size substantially coincides with the cross-section of the flexible tube (10), when the latter is situated in the passage,^"

- that walls (40, 41) surrounding the flexible tube (10) in an area between the first channel and said passage form a transferring channel, which at one of its ends has substantially the same cross-section as the first channel and at its other end has substantially the same cross- section as the passage, said walls (40, 41) further having outlet openings for liquid around the tube, which are distributed all around the transferring channel as well as along the same between the first channel and the passage, - that said means (14) for discharge of liquid from the first channel communicates with the first channel through said outlet openings and

- that the outlet openings have a total outflow area per unit of length of the transferring channel dimensioned such that a gradual outflow of liquid is obtained through the outlet openings along a substantial part of the transferring channel.

2. Plant according to claim 1, c h a r a c t e r i z e d i n that said transferring device (3) comprises an unperforated pipe (42, 43) with stiff walls, which forms said passage and extends a distance along the flexible tube (10).

3. Plant according to claim 1 or 2, c h a r a c t e r i z e d b y a housing (34) surrounding the walls (40, 41) of the transferring channel and defining around these walls an outlet chamber (36) communicating with the outlet openings.

4. Plant according to any of the preceding claims, c h a r a c t e - r i z e d i n that the outlet openings in the walls (40, 41} of the transferring channel have a total through-flow area per unit of length of the transferring channel, which increases seen in the movement direction of the flexible tube (10).

5. Plant according to any of the claims 2-4, c h a r a c t e r i z e d i n that the unperforated pipe (42, 43) constitutes a direct continua¬ tion of the perforated walls (40, 41) of the transferring channel.

6. Plant according to any of the preceding claims, c h a r a c t e - r i z e d b y a housing (34) that is connected with said first and second means (1, 2) and that surrounds the perforated walls (40, 41) of the transferring channel, a partition (35) in the housing separating an outlet chamber (36), that communicates with the outlet openings in the walls (40, 41) of the transferring channel, from an inlet chamber (37) that communicates with said second channel.

7. Plant according to any of the preceding claims, c h a r a c ¬ t e r i z e d i n that two opposing walls (40, 41) of the transferring channel form an interspace between themselves for passage of a flattened flexible tube (10), the opposing walls (40, 41) converging towards said passage.

8. Plant according to any of the preceding claims, c h a r a c ¬ t e r i z e d i n that the walls (40, 41) of the transferring channel comprise two substantially plane, perforated plates, which form an interspace between themselves for passage of a flattened flexible tube (10) and which leave open slots between their respective side edges for outflow of part of liquid accompanying the flexible tube (10) into the transferring channel.