WO2007139468A1

WO2007139468A1 - An apparatus for evaporative cooling of a liqueform product

Info

Publication number: WO2007139468A1
Application number: PCT/SE2007/000508
Authority: WO
Inventors: Gustav Gustavsson; Roland Ringström
Original assignee: Tetra Laval Holdings & Finance Sa
Priority date: 2006-05-26
Filing date: 2007-05-24
Publication date: 2007-12-06
Also published as: SE529950C2; SE0601172L

Abstract

The invention relates to an apparatus for evaporative cooling of a liqueform product. The apparatus comprises a vacuum chamber (1) which is divided into a first, centrally positioned space (6) and a second space (7) which concentrically surrounds the first space (6). Both of the spaces (6, 7) are open towards the upper end of the vacuum chamber (1). The vacuum chamber (1) has a conical upper portion (2). The first space (6) has an outlet (25) for condensed steam. The second space (7) has an inlet (12) for product supplied with steam as well as an outlet (13) for the product. The apparatus also includes a circulation circuit for cooling liquid. The first space (6) is lengthened downwards so that it extends at least as far below the bottom wall (4) of the vacuum chamber (1) as the extent of the space (6) inside the vacuum chamber (1).

Description

AN APPARATUS FOR EVAPORATIVE COOLING OF A LIQUEFORM PRODUCT

TECHNICAL FIELD The present invention relates to an apparatus for evaporative cooling of a liqueform product, comprising a vacuum chamber divided into a first, centrally placed space and a second space which concentrically surrounds the first space, and where both spaces are open towards the upper end of the vacuum chamber, said first space being lengthened downwards and extending at least as far below the bottom end wall of the vacuum chamber with a lower part as the extent of the space inside the vacuum chamber, which constitutes an upper part, and that the first space is provided with an outlet for condensed steam and the second space has an inlet for vaporized product as well as an outlet for the product, the apparatus also including a circulation circuit for coolant liquid. Today, the heat treatment of liquid food products, such as milk, is a quite common industrial process. By heating the product, there will be obtained increased shelf-life as a result of extermination of the microorganisms which are to be found in the product. On sterilization of the food product, this is heated to a temperature exceeding 100⁰C. In order rapidly to heat up to such temperatures, steam is employed. The heating can be put into effect either directly or indirectly. In indirect heating, different types of heat exchangers are employed. In the direct heating, steam is added direct to the product.

There are two types of direct heating of a liquid product, injection and infusion. In injection, steam is injected into the product in a closed system. Infusion implies that the product is finely divided and caused to pass a space filled with steam. In both cases, the supplied steam rapidly and efficiently heats up the product to the desired temperature and the product is then held at this temperature for a given, predetermined time interval. The supplied steam must thereafter be removed from the product, since the intention is to avoid diluting product. This is normally put into effect by evaporative cooling, so-called flash cooling, in a vacuum chamber. During the process, the steam is released and condensed, at the same time as the product is cooled down to the temperature it had before the heat treatment. The evaporative cooling normally takes place in that the product supplied with steam is fed under pressure into a vacuum chamber. When the product enters into the vacuum chamber, the liquid boils, the steam is released and rises upwards in the vessel, while the product accumulates in the lower region of the vessel. Thus cooled, the product may be drained off from the lower region of the vessel. The steam which, together with incondensable gases, departs from the product is to be condensed in order for it to be drained off to an outlet. The condensation can either be put into effect in that the steam and gases are fed into an additional vacuum chamber, where the steam is cooled by being showered with cold water, or that the steam is condensed in some form of water-cooled plate condensor or tube condensor. The plate- or tube condensor may be integrated into the first vacuum chamber, or alternatively be placed outside it.

Most of the apparatuses existing today for condensing steam are relatively expensive to manufacture, since, in the first case, an extra vacuum chamber is required or alternatively some form of condensor is needed. For the conventional method of condensing the steam, a large quantity of cooling water is moreover consumed, and this water should be of good quality in order to avoid furring and corrosion on plates or tubes in the condensor.

Swedish Patent Specification SE 514 560 describes an apparatus for evaporative cooling which only utilises one vacuum chamber. The vacuum chamber is divided into two concentrically placed spaces which are open upwards towards the upper end wall of the vessel. The product supplied with steam enters into the one space, and in the other space the released steam is showered with cooling water from a closed circulation circuit. Nor does this apparatus need any expensive and complicated condensors. However, one drawback inherent in this apparatus is that there is a risk that the cooling water which is employed for condensing the steam can splash over to the other space and thereby dilute the product, or even worse risk infecting the sterile food product. By showering coolant liquid from above in the one space, there is also created a cold surface against the product space which may result in the steam in the product being condensed too soon, and that a part of the steam thereby accompanies the product out. Swedish Patent Specification SE 526 792 also relates to an apparatus for evaporative cooling with a similar construction with two concentric spaces, where the one space is lengthened beneath the bottom surface of the other. This arrangement prevents cooling water from finding its way into the product, or that the steam runs the risk of condensing too soon. The vacuum chamber which is described in this specification has a conventionally rounded upper end wall. However, it has proved that the product supplied with steam, when entering into the vacuum chamber, forms a permanent vortex. When the steam departs from the vortex, product may accompany the steam, which implies product losses, and also that the product may infect the sterile cooling water. This takes place above all when the intention is to raise capacity of the apparatus and this constitutes a factor which restricts capacity.

OBJECTS OF THE INVENTION One object of the present invention is that the apparatus be designed such that the separation of steam and product will be much more efficient, which reduces the risk of product losses.

A further object of the present invention is that the effective separation results in it being possible to considerably increase the capacity of the apparatus. Yet a further object of the present invention is that smaller vacuum chambers than normal for the same capacity can be employed.

SOLUTION

These and other objects have been attained according to the present invention in that the apparatus of the type described by way of introduction has been given the characterising feature that the vacuum chamber has a conical upper portion.

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

One preferred embodiment of the present invention will now be described in greater detail hereinbelow, with reference to the accompanying Drawings. In the accompanying Drawings: Fig. 1 is a side elevation of the vacuum chamber in the apparatus;

Fig. 2 is a side elevation, partly in cross section, of the vacuum chamber in the apparatus; and

Fig. 3 shows a flow diagram valid for the apparatus.

DESCRIPTION OF PREFERRED EMBODIMENT

An apparatus for evaporative cooling of a liqueform product comprises a vacuum chamber 1 which is shown in detail in Figs. 1 and 2. The vacuum chamber 1 has a conical upper portion 2, a side wall 3 and a bottom wall 4. Inside the vacuum chamber 1 there is disposed an additional circular wall 5 which divides the vacuum chamber 1 into two concentrically disposed spaces, a first 6 and a second 7. Both of the spaces 6, 7 are open towards the upper end of the vacuum chamber 1. The lower definition of the second space 7 consists of the bottom wall 4 of the vacuum chamber 1.

The first space 6 which is positioned centrally in the vacuum chamber 1 is lengthened downwards, so that the space 6 continues below the bottom wall 4 of the vacuum chamber 1 so that the space 6 consists of two parts 8, 9. That part 8 of the space 6 which is located below the bottom wall 4 has a longer or alternatively equally long extent as that part 9 which is located above the bottom wall 4 and inside the vacuum chamber 1. The lower part 8 has a bottom portion 10 which is rounded or which is otherwise suitably formed for a vacuum chamber.

The conical upper portion 2 of the vacuum chamber 1 has a top angle α which is 35-60°, preferably the top angle is 45-50°. The first space 6 has an extent upwards in the vacuum chamber 1 so that, at the level 11 for the upper definition of the first space 6, the first space 6 has a cross sectional area a which is less than or equal to the cross sectional area A of the second space 7 at the same level 11. As a result of the described design of the vacuum chamber with both of its spaces 6, 7, no manhole is required on the vacuum chamber 1. By disconnecting the lower part 8 of the first space 6 from the upper part 9, it is then possible to draw out the upper part 9 from the vacuum chamber 1 and by such means gain access to the vacuum chamber 1. Given that the manhole will become superfluous, the vacuum chamber 1 can be manufactured much more cheaply.

Adjacent the second space 7 in the vacuum chamber 1, there is an inlet 12 for the heated product supplied with steam. The inlet 12 is disposed tangentially in the side wall 3 of the vacuum chamber 1 and is disposed as a vertical gap. In the second space 7, there is also an outlet 13 for the cooled product. The bottom wall 4 of the vacuum chamber 1 is designed such that liquid, i.e. product or cleaning liquid, cannot remain stagnant in the lower part of the second space 7. The outlet 13 is connected to a conduit 14 which, via a centrifugal pump 15, pumps the product further to continued treatment or processing. The first space 6 has, in its bottom portion 10, an outlet 16 for the cooling liquid, preferably water, which is to condense the steam from the product The outlet 16 is connected to a conduit 17 which, via a centrifugal pump 18, pumps the cooling water to a cooler 19. The cooler 19 may, for example, be in the form of a plate heat exchanger. The cooler 19 is also connected to a cold water conduit 20. From the cooler 19, the cooling water passes further into an as good as closed circuit, via a conduit 21, back to a cooling water inlet 22 in the bottom portion 10 of the first space 6. The cooling water conduit continues through the greater part of the lower portion 8 of the first space 6. That part 23 which passes through the lower part 8 of the first space 6 has, in its upper end, a number of holes 24. Through these holes 24, cooling water is showered on the steam which is located in the lower part 8 of the first space 6. The number of holes 24 depends on the capacity for which the apparatus is calculated.

It is important that the holes 24 be placed under the bottom portion 4 of the second space 7. If cooling water is sprayed out at a higher level, there is a risk of cooling down the lower part of the circular wall 5 and thereby causing the steam to be condensed before it reaches the first space 6. In the lower part 8 of the first space 6, there is also an outlet 25 for the condensed steam and the incondensable gases which depart from the product. The outlet 25 is provided in the form of a spillway overflow. The conduit from this overflow 25 normally passes via a vacuum pump (not shown) to outlet. It is this vacuum pump which otherwise creates vacuum in the chamber 1.

The vacuum chamber 1 is also provided with one or more connections 26 for cleaning, with spray nozzles 27 disposed inside the upper portion of the vacuum chamber 1. By interconnecting, with valve arrangements, the closed cooling water circuit with the remainder of the process equipment, the cooling water circuit can be washed together with remaining equipment and connected to the normal CIP equipment (Cleaning In Place) with which conventional process installations are equipped. As a result of these valve arrangements, the closed cooling water circuit may also be sterilized together with the remaining process equipment, which affords an additional security factor if cooling water were to leak into the product. The product, which is normally at a temperature of 70-120⁰C, is heat treated before entering into the apparatus. The product is heated up in that it is directly supplied with steam, in an injector or an infuser (not shown). The product is heated in the injector or infuser normally to a temperature of 100-150⁰C and is then held at this temperature in a holder cell (not shown), during a certain predetermined interval of time. The time interval depends upon the treatment temperature.

After the holder cell, the product which is mixed with steam enters under pressure into the vacuum chamber 1 of the apparatus through the tangential inlet 12. As a result of the tangential design of the inlet 12, the product will follow along the side wall 3 in the chamber 1, by so-called cyclone effect. When the product under pressure enters into the vacuum chamber 1, the liquid will boil at the sudden pressure drop, whereupon steam and incondensable gases are released from the product. The heavier product falls downwards into the second space 7 while the lighter steam and the incondensable gases rise.

In order to avoid the situation that the product supplied with steam forms a permanent vortex inside the vacuum chamber 1, the vacuum chamber 1 has been provided with a conical upper portion 2 in accordance with the foregoing disclosure. As a result of the conical upper portion 2, the centrifugal force increases upwards in the conical upper portion 2 and there will by such means be obtained a highly efficient separation of steam from the product. Trials carried out with an apparatus according to the present invention demonstrate that the conical upper portion 2 affords a reduced speed of rotation of the steam and the product in the centre of the vacuum chamber 1. The speed of rotation will be considerably higher at the outer edge of the vacuum chamber 1, which contributes to the separation of steam and liquid, and also that the product is pressed downwards.

As a result of the efficient separation, the risk is avoided that product accompanies the steam, which results in product losses and contaminated cooling water. The trials have also demonstrated that the product losses are reduced to a tenth of the product losses in a conventional apparatus for evaporative cooling.

As a result of the design of the vacuum chamber 1 with a conical upper portion 2, it is possible to reduce the size of the vacuum chamber 1 in relation to conventional vacuum chambers 1 with corresponding capacities. A vacuum chamber 1 displaying a design according to the present invention may also be employed for considerably greater capacities than corresponding chambers With a conventional rounded top portion. The trials which have been carried out show that a vacuum chamber 1 of a predetermined size may be employed for twice as high a capacity when the vacuum chamber 1 is provided with a conical upper portion 2 according to the present invention than if a vacuum chamber 1, of the same size, has a conventional cupola-shaped upper portion. This increased capacity does not influence the favourable effect of the separation. As a result, the vacuum chamber will be more economical to manufacture, at the same time as reduced product losses will be obtained.

The product which has now been freed of steam now has a temperature which corresponds to that temperature it had before the heat treatment, i.e. 70-120⁰C. The product is accumulated in the lower portion of the second space 7 in the vacuum chamber 1 and departs therefrom through the outlet 13. Via the conduit 14 and the centrifugal pump 15, the product is conveyed further to additional cooling, or alternatively to other processing or treatment. The steam and the incondensable gases which have risen upwards in the vacuum chamber 1 are drawn down into the upper part 9 of the first space 6, this part 9 serving as an evacuation pipe. In the lower part 8 of the first space 6, the steam and gases will be showered with cooling water from the cooling water conduit 23 and the holes 24. The cooling water may be at a temperature of 10-40⁰C. The higher the temperature of the cooling water, the greater will be the quantity of cooling water that is consumed to condense the steam. In that the cooling water is showered out over the steam at a level which lies far below the upper part 8 of the first space 6, there is no risk that cooling water which may be unsterile leaks into the product The condensed steam, the cooling water and incondensable gases are accumulated in the lower region of the lower part 8 of the first space 6. Here, the spillway overflow 25 is disposed such that the addition of condensed steam and gases departs from the apparatus via this spillway 25, whereafter the condensed steam and the gases are normally led direct to a discharge. The cooling water which is accumulated under the spillway overflow 25 in the lower region of the lower part 8 of the first space 6 is included in the almost closed circulation circuit for cooling water which is encompassed in the apparatus. Via the outlet 16 and the conduit 17, cooling water is pumped from the vacuum chamber 1 by means of the circulation pump 18 to the cooler 19. For instance, the cooler 19 may consist of a plate heat exchanger. In the cooler 19, the water is cooled to a temperature of 10-40⁰C with the aid of cold water which enters into the cooler 19 through the conduit 20.

After the cooler 19, the cooling water returns to the vacuum chamber 1 via the conduit 21, through the inlet 22 and the conduit 23, where the cooling water is once again utilised for showering the released steam from the product. By employing an almost closed cooling water circuit, the consumption of cooling liquid is reduced. By means of a suitable valve arrangement, the cooling water circuit is washable and capable of being sterilized together with the remaining process equipment.

As will have been apparent from the foregoing description, the present invention realises an apparatus for evaporative cooling of a liqueform food product which is more economical than most apparatuses occurring on the market, since a smaller vacuum chamber can be employed for condensing greater capacities of product supplied with steam. As a result of the design of the vacuum chamber, a highly efficient separation will be obtained of steam from the product and there is no risk of product losses or that product contaminates the cooling water.

Claims

WHAT IS CLAIMED IS:

1. An apparatus for evaporative cooling of a liqueform product, comprising a vacuum chamber (1) divided into a first centrally placed space (6) and a second space (7) which concentrically surrounds the first space (6) and where both spaces (6, T) are open to the upper end of the vacuum chamber (1), said first space (6) being lengthened downwards and extending at least as far below the bottom wall (4) of the vacuum chamber (1) with a lower part (8), as the extent of the space (6) inside the vacuum chamber (1), which constitutes an upper part (9), and the first space (6) having an outlet for condensed steam (25) and the second space (7) having an inlet (12) for product supplied with steam, as well as an outlet (13) for the product, the apparatus also including a circulation circuit for cooling liquid, characterised in that the vacuum chamber (1) has a conical upper portion (2).

2. The apparatus as claimed in Claim 1, characterised in that the conical upper portion (2) of the vacuum chamber (1) has a top angle α which is 35-60°.

3. The apparatus as claimed in Claim 1, characterised in that the conical upper portion (2) of the vacuum chamber (1) has a top angle α which is 45-50°.

4. The apparatus as claimed in any of the preceding Claims, characterised in that the cross section a of the first space (6) is equal to or slightly less than the cross section A of the second space (7), at that level (11) where the first space (6) has its upper definition.

5. The apparatus as claimed in any of the preceding Claims, characterised in that the inlet (12) for product is tangentially disposed in the wall (3) of the vacuum chamber (1) and designed as a vertical gap.

6. The apparatus as claimed in any of the preceding Claims, characterised in that the circulation circuit for cooling water discharges with the conduit (23) in the upper region of the lower part (8) of the first space (6).

7. The apparatus as claimed in any of the preceding Claims, characterised in that the outlet (25) for condensed steam is a spillway overflow.

8. The apparatus as claimed in Claim 6, characterised in that the conduit (23) is provided, in its upper part, with a number of holes (24).

9. The apparatus as claimed in Claim 8, characterised in that the upper part of the conduit (23) is to be located under the bottom wall (4) of the second space (7).

10. The apparatus as claimed in Claim 6, characterised in that the circulation circuit for cooling water includes an outlet (16), conduits (17, 21, 23), a centrifugal pump (18) as well as a cooler (19).