AU610233B2

AU610233B2 - A plant for continuously sterilising liquids, such as milk

Info

Publication number: AU610233B2
Application number: AU21722/88A
Authority: AU
Inventors: Ole Andersen; Eskil Bone Jorgensen; Henrik Kjaerbye; Per Grostol Nielsen
Original assignee: APV Pasilac AS
Current assignee: SPX Flow Technology Danmark AS
Priority date: 1987-09-02
Filing date: 1988-09-01
Publication date: 1991-05-16
Anticipated expiration: 2008-09-01
Also published as: DK458687D0; DK458687A; JPH0195725A; AU2172288A; DK169248B1; JP2637784B2

Description

1N 11111 11111-

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Iy~r Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-69 COMPLETE SPECIFICATION (OR IGIN AL)1 03 Class Int. Class Application Number: Lodged: C.nplete Specification Lodged: Accepted: Published: Priority: Re~ated Art 1Tsdor-umil":lt tainsth [ScCloi 49) mid is cl.,f Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: APV PASILAC A/S Ostmarken 7, DK-2860 Soborg, Denmark OLE ANDERSEN, HENRIK PER GROSTOL NIELSEN KJAEitBYE, ESKIL BONE JORGENSEN and EDWD. WATERS SONS, 50 QUEEN STREET, MELBOURNE, AUSTRALIA, 3000.

Complete Specification for the invention entitled: A PLANT FOR CONTINUOUSLY STERILISING LIQUIDS, SUCH AS

MILK

The following statement is a full description of this invention, including the best method of performing it known to us 8eal or i/ Company and Signatures of its Officers as prescribed by its Articles of Association. t K m n t..e K ,1e D h ,i K. .Tn, 24 7 Registered Patent Attorney To: THE COMMISSIONER OF PATENTS.

T- 2 The invention relates to a plant for continuously sterilising liquids, such as milk, where unsterilised milk is sprayed, preferably after preheating, into a sterilising chamber fed with steam which together with the milk is led to a holding chamber in which the milk heated by the steam is kept for a predetermined period Plants for sterilising milk are known. Such plants are sometimes called UHT-plants, i.e. ultra high temperature plants. In these plants steam is sprayed into the milk fed to 10 the sterilising chamber in such a manner that the milk is o 0 heated to a temperature of about 140-148°C. Subsequently, the 0: milk is led to a so-called holding chamber, in which the milk is kept for a predetermined period (approximately 2-5 sec) in 00.. the heated state. Then the milk is led to a vacuum chamoer oo 0 15 via an overflow. In this vacuum chamber the water deriving 0o o from the steam is removed again in such a manner that the solid content of the milk is the same when the milk leaves .o o0 said vacuum chamber as before the feeding of steam. After the processing in the vacuum chamber the milk is usually led to a homogenizer and then subjected to a cooling and packing. The resulting milk has a shelf life of 2-3 months or more. The milk is, however, often encumbered with the draw-back that with respect to taste qualities it cannot compete with pasteurized milk as it tastes more or less as if it has been boiled.

The latter is inter alia due to the fact that in the sterilising chamber the milk has a tendency to burn onto the inner side of the wall of said chamber with the effect that the milk particles in question stay too long in said sterilising chamber and thereby cause the remaining milk to taste boiled. The disadvantageous taste of boiled milk is probably also due to formation of foam caused; by gases contained in the heated milk at the outlet in the bottom of the sterilising chamber.

As a result the stay in the sterilising chamber is prolonged for some of the milk.

Attempts have been made at overcoming the above problem, inter alia by providing a cooling jacket both adjacent a bottom portion of the wall of the sterilising chamber and adjacent was.. te nrst application made in a U-onvention country in respect of the invention the subject of the application.

DECLAR ED thiso .sday Au .t Signature. (6) 1 T 3 at least a portion of the wall of the holding chamber. The cooling jacket is adapted to subject the walls in question to such a temperature that the temperature on the inner side of said walls is slightly below the boiling point of the water at the steam pressure in question.

The object of the present invention is to provide a plant allowing production of a product of the same taste qualities as pasteurized milk, and more particularly to provide a plant where a few milk particles do not stay too long in oo 10 the sterilising chamber and optionally also in the holding chamber.

o0 0 0 The plant according to the invention is characterised S°o in that at the top the sterilising chamber comprises at least one row of downward-directed outlet openings for the milk, o:o 15 said openings being situated along a circle about the centre of the chamber and allowing the milk to flow into the chamber in separate jets, and that the inner wall of the chamber at o0 the top comprises uniformly distributed steam inlet openings.

o0,o. Unlike the known plants where the milk during its passage through the plant is spread into a film meeting the fed steam, 0the present invention has the effect that jets of milk are formed. Each jet of milk is converted into drops meeting the fed steam immediately after the outlet openings, whereby the milk is quickly heated to the increased temperature. In this manner it is ensured that the milk particles do not burn onto portions of the sterilising chamber as no milk particles come into contact with portions of said sterilising chamber having a higher temperature than said particles. The resulting milk -turned out to possess good taste qualities.

A further consequence of the milk being fed to the sterilising chamber in form of jets instead of a thin film or curtain-like stream is that the milk flows at a relatively high speed whereby the tendency to turbulence arising in the sterilising chamber is reduced. In this manner it is additionally ensured that the milk particles are not hurled against the walls of the sterilising chamber.

According to the invention the steam inlet openings are i 4 particularly advantageously provided in a separate bell-shaped device secured to the inside of the chamber, said device and said chamber together defining a circumferential steam distribution chamber, in which the steam fed can be spread before it leaves through the steam inlet openings. As a result the steam enters the interior of the chamber in a slow and steady manner, which reduces the tendency to turbulence additionally.

Moreover according to the invention the steam inlet openings may be situated within an area of such an axial extent that the milk is heated to the increased sterilising temperature before it has passed the lower end of said area within the sterilising chamber, whereby it is ensured that no milk particles come into contact with chamber portions of a higher temperature.

The distribution chamber may according to the invention o0 o comprise distributor means situated adjacent a steam inlet and o 0 °causing the steamn to circulate inside the distribution chamber.

0 In this manner a uniform distribution of the steam as well as a o 0o o 2 feeding of steam in form of an almost laminar and uniformly 20 distributed flow are obtained.

00000 Finally according to the invention at least one air 00 aoutlet may be provided in the top of the chamber, whereby the 00 0 0 0 0 0 gases contained in the milk can easily escape without haviig to follow the milk through the outlet of the sterilising chamber.

The invention will now be described with reference to milk as the liquid by way of example only, as it will be readily understood that by persons skilled in this art that any 0 I nutrient containing liquid can be utilised in the present 3 invention.

The invention will be described with reference to the accompanying drawing, in which Fig. 1 is a diagrammatic view of a preferred embodiment of a plant according to the invention, and Fig. 2 is on a larger scale a vertical, sectional view through a sterilising chamber of the plant of Fig. i, and where said sectional view does not include all parts for the sake of clarity.

I k~"c ""~a~u3arrr~ i i i 4A The plant of Fig. 1 for sterilising milk comprises a sterilising chamber 1 communicating with the bottom of a holding chamber 3 through a pipeline 2. An overflow pipe 4 extends upwards through the bottom of the holding chamber 3 o o e Q 0 0 o0 0 0 00 0 0 0 0 o 00 0 0 o a 0 00 0 000000

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C 1I E j 1 1 1 to a predetermined level inside said holding chamber 3, and communicates with the inlet 5 of a vacuum chamber 6. At the bottom the outlet of the vacuum chamber communicates with a homogenizer 8 through a pipeline 7. The outlet of the homogenizer 8 communicates with a heat exchanger 9 through a pipeline The cold side of the heat exchanger is connected to a pipeline 11 for the feeding of raw milk. Having passsed the heat exchanger 9 the raw milk continues through a pipeline 12 10 connected to the top of the sterilising chamber i. The top of 0 oo0 0 00 o 0 the sterilising chamber 1 comprises an outlet head 13 described 0= more detailed below and including rows of outlet openings 14 o and 15, cf. Fig. 2, situated along circles about the centre of the chamber. The raw milk is preheated in the heat exchanger o0 15 9 and flows therefrom through the above outlet openings and oo o into the sterilising chamber in thin jets 16 and 17. Gradually these jets divide into drops during their passage towards the 0 bottom of the sterilising chamber 1.

0 A steam distribution chamber 18 is mounted along the inner side of the upper end of the sterilising chamber 1. The distribution chamber communicates with the interior of the sterilising chamber 1 through uniformly distributed apertures.

The distribution chamber 18 is fed with steam under pressure o through a pipeline 19.

A cooling jacket 20 extends round and along the lower end of the sterilising chamber 1 and allows passage of liquids at an increased temperature of about 110-130 0 C. The temperature is adapted to the walls of the sterilising chamber 1 being about 3 mm thick, and the pressure inside the sterilising chamber 1 is about 4.0 bar abs.

The liquid is fed to the cooling jacket from a heat exchanger 21 through a pipeline 22 connected to the cooling jacket 20 adjacent the lower end thereof. The outlet of the cooling jacket 20 communicates with the inlet of the heat exchanger 21 through a pipeline 23.

A cooling jacket 24 extends also round the holding chamber 3, where the inlet of said cooling jacket communicates 6 with the outlet of the heat exchanger 21 through a pipeline and where the outlet of said cooling jacket communicates with the inlet of the heat exchanger 21 through a pipeline 26.

The cooling jackets 20 and 24 on the sterilising chamber 1 and the holding chamber 3, respectively, are adapted to provide the adjacent wall portions with a lower temperature than the sterilising temperature of about 140-148°C, and more particularly with a temperature slightly below the boiling point of the water at the steam pressure in question.

S10 When the plant is running, raw milk flows through the o 0 0 0 pipelines 11 and 12 and the heat exchanger 9 to the sterilising 00 chamber 1. The raw milk enters as previously mentioned the o sterilising chamber in thin jets 16 and 17. Immediately after leaving the sterilising chamber the jets 16 and 17 of milk 0 15 meet a flow of steam fed through the pipeline 19. The steam 0 heats the milk to the sterilising temperature. The heated milk cont'inues through the pipeline 2 and into the holding oooo chamber 3 in which the milk is kept for a predeterrined period o oo 0 0 0 (2-3 sec). Subsequently the milk continues through the over- O o o o 20 flow pipe 4 to the vacuum chamber 6, in which liquid is removed until the solid content of the milk corresponds to the solid 0 0 0 o oo content thereof before the milk entered the sterilising chamber i. From the vacuum chamber 6 the milk continues to the homogen- 0oo o00 izer 8 and then through the heat exchanger 9 to further pro- 0 cessing. In the heat exchanger 9 the milk releases heat to the fed raw milk in such a manner that said raw milk is subjected to a preheating. The water removed in the vacuum chamber 6 is sucked out at the top and led to a heat exchanger 28 through a pipeline 27. In the heat exchanger 28 heat is released to the cooling water which is led to the heat exchanger 21. through a pipeline 29. In the heat exchanger 21 the temperature of the liquid for the cooling jackets 20 and 24 is lowered after having passed said cooling jackets 20 and 24.

The sterilising chamber is illustrated more detailed in Fig. 2. At the top the sterilising chamber comprises the outlet head 13 for the milk, said outlet head comprising outlet openings 14 and 15, respectively, situated in circles. The milk 7 is fed to the outlet head 13 through a distributor head comprising two circumferential or annular chambers 31 and 32.

The chambers 31 and 32 extend coaxially round the centre axis of the sterilising chamber i. The outer annular chamber 31 communicates with the interior of the sterilising chamber 1I through the circle of outlet openings 14, whereas the inner annular chamber 32 communicates with the interior of the sterilising chamber 1 through the circle of outlet openings The two annular chambers 31 and 32 are separated from one another and connected to their respective inlet connections 33 and 34, which can be connected to the pipeline 12 as desired for the feeding of raw milk. The running capacity of the plant determines whether the connection 33 or the connection 34 is to be used. In a preferred embodiment of the invention the @0 15 connection 33 and the associated outlet openings 14 are used 0 0 in case the flow amount is required to be 8000 1 of milk/h, whereas the connection 34 and the associated outlet openings o0o00 15 are used in case the flow amount is required to be 4000 1 o 00 00: of milk/h.

o 20 A through opening 35 is situated in the centre of the outlet head 13. The through opening communicates through a central chamber 36 with a connection 37 situated at the top.

A bail-shaped nozzle 38 is screwed in the inner side of the 0000. opening 35, said nozzle comprising, as indicated, a plurality of passage openings uniformly distributed on the surface of said nozzle 38. This nozzle serves two purposes. When the plant is running, the released gases can escape through the nozzle 38 and out through the connection 37. When the sterilising chamber is to be cleaned, cleaning fluid can be sprayed therein through the nozzle 38.

The outlet head 13 is fastened by means of bolts or screws in a manner not shown in details between circumferential flanges 39 and 40 on the distributor head 30 and the wall, respectively, of the sterilising chamber 1. A bell-shaped device 41 is simultaneously fastened by means of bolts or screws on the inner side of the flange 40 on the wall of the sterilising chamber i. The device 41 comprises a frusto-conical 8 portion 42 and a cylindrical portion 43, said portions being interconnected. The lower end of the cylindrical portion 43 comprises an outwardly inclined, circumferential flange 44.

As indicated in the drawing the bell-shaped device is divided into thre axially succeeding sections 45, 46, and 47. 'he two latter sections 46 and 47 extend from the centre of the frustoconical portion 42 to the lower end of the cylindrical portion 43 and are provided with uniformly distributed perforations as shown. Although the drawing only indicates a few perforations, such perforations 60 are uniformly distributed everywhere on said sections. These perforations 60 allow passage of steam, which as mentioned above is fed to the steam distribution chamber 18 defined between the bell-shaped device 41 and the wall of the sterilising chamber 1.

The steam is fed through a pipe stub 48. A through opening 61 is situated inside the pipe stub 48 in a wall of a circumferential channel 49. Inside the opening 61 a plate is provided which the fed steam hits. From the plate the steam flows to the sides and circulates in the circumferential channel 49. Inwardly the circumferential channel 49 is defined by the upper section 45 of the bell-shaped device 41 and outwardly, i.e. to the side facing the steam distribition chamber 18, by a wall 62 with perforations (not shown in detail) allowing passage of steam into the distribution chamber 18. The circumferential channel 49 and the perforations thereof towards the distribution chamber 18 ensure a uniform distribution of steam to the distribution chamber 18. Simultaneously a calming of the movement of the steam is achieved in such a manner that the steam follows an almost laminar flow at a low speed into the interior of the sterilising chamber 1 through the perforations 60 in the bell-shaped device 41.

The cooling jacket 20 is visible at the lower portion of the sterilising chamber 1. The interior of the cooling jacket may be provided with flow-preventing means 51, 53, 54, and in form of thin, bent bars suitably secured. The flow-preventing means ensure a distributed flow path of the cooling liquid through the cooling jacket 20 in such a manner that the wall

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M~o i- 9 of the sterilising chamber i has a uniform temperature along the entire circumference ;thereof. The inlet of the cooling jacket 20 is indicated by the reference numeral 56 and the outlet by the reference numeral 57.

When the sterilising chamber is used, the milk flows, as mentioned, either out through the circle of openings 14 or through the circle of openings 15 depending on the required flow amount to be processed. The milk leaves in thin jets and is immediately exposed to the steam .ed through the perforations 60 in the bell-shaped device 41. The axial extent of the bell-shaped device 41 has been chosen such that all the milk particles are heated to the desired sterilising temperature of about 140-148°C before they leave the lower section of the bell-shaped device. The milk particles fall in a uniform flow towards the bottom of the sterilising chamber while they absorb almost all the steam fed.

When the sterilising chamber 1 is used, water is condensed opposite the cooling jacket 20 whereby a thin film of liquid is formed. The film flows towards the bottom of the sterilising chamber i. As a result the milk particles are prevented from burning onto the wall of the chamber. The cavitations in the milk resulting from the heating of the gases present in said milk turns out to collapse due to their content of condensable substances, i.e. steam and other ingredients.

Subsequently the removed gases escape through the nozzle 38, and consequently nothing prevents the milk from flowing out immediately through the outlet of the sterilising chamber 1 and directly into the holding chamber 3, cf. Fig. i. Therefore no milk particles stay too long in the sterilising chamber I.

The bell-shaped device 41 and the associated outlet head 13 are very easy to clean, the cleaning being easily performed by spraying cleaning liquid therein through the nozzle 38.

The invention has been described with reference to a preferred embodiment. Many modifications can, however, be carried out without thereby deviating from the scope of the invention. Thus the cooling jackets 20 and 24 may, for inst- I:i ance, be divided into several sections and fed with liquid from their respective heat exchanger. In addition, the invention is, of course, adapted to the product to be processed, as many other products apart from ordinary milk can be processed, viz. for instance soya milk, coconut milk, starch-based products, and other nutrient-containing liquids.

a a 0 0 C tS o oae o a e 0o 6 -r

Claims

1. A plant for continuously sterilising liquids, where unsterilised liquid is sprayed, preferably after preheating, into a sterilising chamber fed with steam which the liquid heated by the steam is kept for a pedetermined period, characterised in that at the top the sterilising chamber comprises at least one row of downward-directed outlet openings for the liquid, dsaid openings being situated along a circle about the centre of the chamber and allowing the liquid to flow into the chamber in separate jets, and that the inner wall of the chamber at the top comprises uniformly distributed steam inlet openings.

2. A plant as claimed in claim 1 wherein said liquid can be milk, cream, skimmed milk, flavoured milk, ice cream oo o mix, chocolate milk, vitamin enriched milk, soymilk, coconut o 00 0 0 milk, starch based liquids or any other nutrient-containing oo liquids. 0 0 00o

3. A plant as claimed in claim 1 or 2, characterised o oo 0 in that the steam inlet openings are provided in a separate o000 bell-shaped device secured to the inside of the chamber, said 0oo o device and said chamber together defining a circumferential o o steam distribution chamberm in which the steam fed can be spread before it leaves through the steam inlet openings.

4. A plant as claimed in claim 1, 2 or 3 characterised in that the steam inlet openings are situated o 0 oo0o within an area of such an axial extent that the liquid is heated to the increased sterilising temperature before it has o'o 0 passed the lower end of said area within the sterilising chamber.

5. A plant as claimed in claim 2, characterised in 0 that the steam distribution chamber comprises distributor means .0 0situated adjacent a steam inlet and causing the steam to or circulate inside the distribution chamber.

6. A plant as claimed in any one of claims 1 to 4, L Ilkqnll I~ BIC~rSPWr~l 19 characterised in that at least one air outlet is provided in the top of the chamber.

7. A plant being substantially as herein described with reference to the accompanying drawings. DATED this 11 February 1991 APV PASILAC A/S WATERMARK PATENT TRADEMARK ATTORNEYS SUITE 6, FLOOR 16, TOWN HALL HOUSE, 456 KENT STREET, SYDNEY N.S.W. 2000. V7- 0 2 i