WO2001019209A1

WO2001019209A1 - An apparatus in the heat treatment of a flow of a pumpable food product

Info

Publication number: WO2001019209A1
Application number: PCT/SE2000/001781
Authority: WO
Inventors: Fredrik Innings; Mattias Lennartsson; Eric Lundgren
Original assignee: Tetra Laval Holdings & Finance Sa
Priority date: 1999-09-14
Filing date: 2000-09-14
Publication date: 2001-03-22
Also published as: SE523358C2; AU7467500A; SE9903263D0; SE9903263L

Abstract

The disclosure relates to an apparatus in the heat treatment of a flow of a pumpable food product. The apparatus comprises a buffer pipe (1) through which the product passes and in which the product, which is at a given temperature, stays for a certain period of time. The buffer pipe (1) consists of a cylindrical pipe (2) of a certain length L. The pipe (2) is connected to a closed system including a conduit (9), as well as a piston and cylinder assembly (10). The closed system is filled with a liquid. Throughout its entire length L, the pipe (2) of the buffer pipe (1) has an inner passage (5) manufactured from a flexible material. The inner passage (5) is connected to the product flow. That volume of product which stays in the inner passage (5) is reduced when the product flow through the buffer pipe is reduced, in that more liquid from the closed system is fed into the pipe (2).

Description

AN APPARATUS IN THE HEAT TREATMENT OF A FLOW OF A PUMPABLE FOOD PRODUCT

TECHNICAL FIELD The present invention relates to an apparatus in the heat treatment of a flow of a pumpable food product, comprising a buffer pipe through which the product passes and in which a predetermined temperature is maintained for a predetermined period of time.

BACKGROUND ART

In the heat treatment of pumpable food products, the product is heated to a predetermined temperature. The temperature depends on what process is intended, such as, for example, pasteurisation or sterilisation. When the product has reached the desired temperature, it must be kept at this temperature for a predetermined period of time.

The heat treatment may be put into effect indirectly or directly. In indirect heat treatment, the heating of the product takes place in some form of heat exchanger which may, for example, be a plate heat exchanger or a tube heat exchanger. In direct methods, heated steam is supplied direct to the product. Examples of such methods are injection and infusion.

An apparatus for maintaining the attained temperature during a given period of time consists of a buffer pipe. The buffer pipe is normally designed as a pipe loop or alternatively a straight pipe section, or combinations of these two. The length of the pipe or the pipe loop corresponds to the treatment of a certain product at a certain calculated capacity of the heat treatment plant. It is important that the stay time is exact, since too short a stay time does not give the desired treatment of the product, and too long a stay time injuriously affects the product, by changes to its flavour or aroma.

The capacity for which the heat treatment plant, and thereby also the buffer pipe, is calculated normally corresponds to a number of filling machines for packing the product into consumer packages. When one or more of these filling machines possibly drops out of production because of operational disruption, the flow is reduced and the result will rapidly be an overly long stay time in the buffer pipe and thereby an overtreated product. It is, therefore, desirable that the buffer pipe may be rapidly regulated so that the stay time can be kept constant. Also in cases when the intention is to rapidly vary production to suit different foods which require different stay times, use may be made of a variable buffer pipe. Without such a possibility of varying the stay time, the entire plant must be retro-designed or alternatively an overtreated product must be accepted.

A variable buffer pipe is described in Swedish Patent Specification SE 510 797. This buffer pipe has one or more cooled sections which can be engaged stepwise when necessary. The drawback inherent in this buffer pipe is that those steps by which the buffer pipe capacity can be cut are fixed and, in certain practical applications, these steps may be too large.

OBJECTS OF THE INVENTION

One object of the present invention is to realise a buffer pipe which is steplessly variable and which may rapidly be varied in relation to changes in the flow.

A further object of the present invention is that the buffer pipe is to be simple and economical, both in manufacture and in maintenance.

SOLUTION

These and other objects have been attained according to the present invention in that an apparatus of the type described by way of introduction has been given the characterising features that the buffer pipe consists of a cylindrical pipe of a certain length L, which is connected to a closed system containing a liquid, and that the entire length L of the pipe is accommodated by a inner passage of a flexible material, the passage being connected to the product flow.

Preferred embodiments of the present invention have further been given the characterising features as set forth in the appended subclaims.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Two preferred embodiments of the present invention will now be described in greater detail hereinbelow, with reference to the accompanying Drawings, in which: Fig. 1 shows, partly in section, the apparatus according to the present invention; and

Fig. 2 schematically illustrates the apparatus connected in to a conduit.

DESCRIPTION OF PREFERRED EMBODIMENTS

The apparatus according to the present invention consists, in principle, of a buffer pipe 1 or a part of a buffer pipe 1. The buffer pipe 1 is intended to be placed after a heat treatment plant for a flow of a pumpable food product. The heat treatment plant may, for example, have indirect heating, such as various types of heat exchangers, or direct heating, such as an injector or an infusor. In the heat treatment plant, the product is heated to a predetermined temperature. The temperature depends on whether the product is to be pasteurised or sterilised. For the pasteurisation or sterilisation of the food product to achieved the desired result, i.e. the destruction of micro-organisms. The attained temperature must be maintained for a predetermined period of time.

The product is to remain in the buffer pipe 1 during the predetermined period of time. If the stay time is too short, the desired effect of the heat treatment will not be achieved, and if the stay time is too long, the flavour and aroma of the product will be injuriously affected, as a result of excessively high thermal shock or loading.

The buffer pipe 1 is adapted to a certain maximum capacity of the heat treatment plant, which is relatively constant. On the other hand, it occurs relatively often that disruptions downstream, after the heat treatment plant, may affect the stay time of the product in the buffer pipe 1. After the heat treatment plant, the product is most generally pumped to a number of filling machines for packing into consumer packages. If an operational disruption possibly occurs so that one or more filling machines fall out of production, there will be a rapid change in the flow and thereby a prolonged stay time in the buffer pipe 1.

The construction of the buffer pipe 1 according to the present invention is apparent from Fig. 1. The buffer pipe 1 consists of a cylindrical pipe 2 of a certain length L. The pipe 2 has a diameter which is larger than connecting conduits 3, for which reason it is necessary to mount conical joint pieces 4 between the pipe 2 and the connecting conduits 3. Within the pipe 2, throughout its entire length, there is disposed an inner passage 5. The inner passage 5 is manufactured from a flexible, heat-resistant and food-approved material, for example a rubber or plastic material.

The securement of the inner passage 5 must be hygienically tight and can, as is shown in Fig. 1, be designed such that the ends 6 of the inner passage 5 are bent out and in over the ends 7 of the pipe 2 and that the conical joint pieces 4 are designed so as to seal against the ends 6 of the passage 5. This affords a hygienic seal with requisite sealing pressure and without unhygienic gaps. The inner passage 5 is secured such that it constitutes an extension of the connecting conduits 3 and the product will thus pass the buffer pipe 1 through the inner passage 5.

The cylindrical pipe 2 has a connection 8 on its circumferential surface. This connection 8 is coupled via a conduit 9 to a piston and cylinder assembly 10 as shown in Fig. 2. That section of the pipe 2 which surrounds the inner passage 5, the conduit 9 and the front section of the piston and cylinder assembly 10 contains an incompressible liquid in a closed system. As a result of the movement of the piston in the piston and cylinder assembly 10, the interior of the passage 5 which is flexible can be modified so that the volume which is enclosed in the inner passage 5 is reduced. The connection 8 may be placed at any optional position on the circumferential surface of the pipe 2. If the connection 8 is placed centrally on the pipe 2, the connection 8 should be provided inwards, towards the pipe 2, with some form of bulging grid so that the connection 8 does not run the risk of being blocked when the inner passage 5 is pressed together. This may possibly be avoided by placing the connection 8 in one end of the pipe 2.

The conduit 9 constitutes a buffer for the liquid which is displaced by means of the piston and cylinder assembly 10. Since the product which is conveyed through the buffer pipe 1 may be at a temperature of 150°C in sterilisation, the liquid which surrounds the inner passage 5 will rapidly be heated. Experiments have shown that, by placing the conduit 9 and the piston and cylinder assembly 10 beneath the buffer pipe 1, heating of the conduit 9 is reduced compared with if the conduit 9 is placed beside or above the buffer pipe 1. As a result of the correct placing of the conduit 9 and the piston and cylinder assembly 10, together with adaptation of the length of the conduit 9, it is possible to prevent the piston and cylinder assembly 10 from being exposed to excessively high temperatures.

The apparatus according to the present invention normally also includes temperature gauge 11 and pressure gauge 12. In Fig. 2, the flow direction of the product is shown by means of arrows. The heat treatment equipment is disposed upstream of the apparatus according to the present invention and a number of filling machines are disposed downstream of the apparatus according to the present invention. This arrangement is not shown on the Drawings.

The function of the apparatus according to the present invention will now be described in two different preferred embodiments. In the first preferred embodiment, the inner passage 5 has a cross sectional area which corresponds to the cross sectional areas of the connecting conduits 3 when the flow through the buffer pipe 1 is at its largest, i.e. when all filling machines connected to the heat treatment plant are in operation. Temperature gauges 11 after the buffer pipe 1 ensure that the product keeps the correct temperature during its passage through the buffer pipe 1.

When the control system of the heat treatment plant registers a reduction in flow, for example because one of the filling machines has stopped, the control system emits a signal to the piston and cylinder assembly 10. The piston in the piston and cylinder assembly 10 is displaced so that more liquid is forced into the pipe 2. The liquid will then compress the flexible inner passage 5 so that that volume of product which stays in the inner passage 5 is reduced. The quantity of liquid which is displaced into the pipe 2 must have a volume which, at the current stay temperature, gives the volume in the buffer pipe 1 which corresponds to the requisite stay time in the buffer pipe 1. The more liquid which is forced into the pipe 2 through the movement of the piston, the smaller will be the retained volume. The liquid may consist of de-aerated, de-ionised water which should preferably also be sterile.

In the second preferred embodiment of the present invention, the liquid consists of a food-approved oil. When the largest flow for which the buffer pipe 1 is adapted passes through the buffer pipe 1, the flexible walls of the inner passage

5 are inflated by the pressure of the product and a large quantity of liquid is evacuated from the pipe 2. When a reduced flow is indicated, more liquid is fed to the pipe 2 and the volume maintained in the inner passage 5 is reduced.

By adapting the volume in the inner passage 5 to the flow which at present prevails, it is possible rapidly and exactly to obtain the correct stay time for the product through the buffer pipe 1. By measuring the pressure difference across the passage 5, i.e. the difference between the pressure which is indicated by the pressure gauge 12 and the pressure gauge 13 placed on the conduit 9, and by comparing this with a reference pressure at the current position of the piston in the piston and cylinder assembly 10, it is possible to indicate leakage from the inner passage 5. If the pressure difference exceeds a given preselected value, this indicates that the inner passage is worn out or damaged.

The variable buffer pipe 1 according to the two above-described preferred embodiments can also be employed in those cases when it is desired to be rapidly able to vary production. Since different food products require different stay times in a buffer pipe 1, a conventional plant must normally be retro-fitted to a considerable degree if the intention is to vary the stay time.

As will have been apparent from the foregoing description, the present invention realises an apparatus for being able to steplessly vary the buffer pipe 1 in a heat treatment plant so that, in the event of possible operational disruption, it is possible to rapidly adapt the volume in the buffer pipe 1. Given that the volume in the buffer pipe 1 can be altered in varying flows, a constant stay time can be obtained.

The present invention should not be considered as restricted to that described above and shown on the Drawings, many modifications being conceivable without departing from the scope of the appended Claims.

Claims

WHAT IS CLAIMED IS:

1 . An apparatus in the heat treatment of a flow of a pumpable food product, comprising a buffer pipe (1) through which the product passes and in which a predetermined temperature is maintained for a predetermined period of time, characterised in that the buffer pipe (1) consists of a cylindrical pipe (2) of a certain length L, which is connected to a closed system containing a liquid; and that the entire length L of the pipe (2) is accommodated by a inner passage (5) of a flexible material, the passage (5) being connected to the product flow.

2. The apparatus as claimed in Claim 1, characterised in that the volume of the product quantity which is kept in the inner passage (5) is disposed to be reduced in reduced product flow through the buffer pipe (1).

3. The apparatus as claimed in Claim 1, characterised in that the closed system to which the pipe (2) is connected comprises a connection (8) on the circumferential surface of the pipe (2), a conduit (9) and a piston and cylinder assembly (10).

4. The apparatus as claimed in Claim 1, characterised in that the liquid consists of de-ionised, de-aerated, water.

5. The apparatus as claimed in Claim 1, characterised in that the liquid consists of a food-approved oil.

6. The apparatus as claimed in Claim 1, characterised in that the inner passage (5) is secured in that its ends (6) are bent out and in over the ends (7) of the pipe (2); and that they are tightly retained in this position by means of conical joint pieces (4).