CH626788A5 - - Google Patents

Description

The present invention relates to a device for sterilization and / or homogenization of a fluid product by injection of steam, comprising a T-shaped body composed of a straight tube and a tubular arm for supplying the product. fluid, and a steam injection nozzle disposed axially in a first end or inlet of the tube and opening onto a mixing chamber at the branch of the arm and the tube.

Various types of device are known for sterilizing fluid food products by steam injection. Some are based on the principle of injecting steam into the product, others on the principle of injecting product into steam, and still others on the principle of injecting steam and product. in a mixing chamber. The latter type of device has been found to be usable for most products. A known model of this kind comprises two nozzles each having an interior section that is first convergent then divergent, nozzles placed one after the other in the right tube of a T-shaped body, the outlet of the first entering the entry of the second at the junction of the tube and a tubular arm. Steam is injected under pressure into the first nozzle, the product is introduced under pressure into the tubular arm, and the vapor and product mix in the second nozzle which acts as a mixing chamber. Satisfactory results can be obtained with this model for most products, and in particular for very viscous products such as low-water flour soups or melted cheese pasta. However, this type of device must necessarily be oversized if one wishes to prevent the mass of fluid to be sterilized from forming a plug downstream of the mixing chamber. The violent turbulence that reigns in the latter prevents any possible congestion from occurring there, but the turbulence decreases beyond. To avoid a blockage beyond the mixing chamber, it is necessary to inject excess steam, so that the uncondensed steam bubbles serve as a vehicle for the heated fluid mass. This involves a waste of steam and also results in an irregular distribution of the fluid mass in a standby line comprised between the steam injection device and a device for cooling by discharge under reduced pressure, which is equivalent to a distribution inhomogeneous of the temperature in the mass. Another consequence is the pressure variations caused by an irregular flow in the standby line which can reverberate upstream of the injection nozzle and result in variations in the temperature of the injected vapor.

The present invention is the result of research into a device free from these defects.

The device according to the present invention is characterized by the fact that the internal wall of the nozzle converges downstream on a short channel of constant section opening onto the mixing chamber, and by the fact that a stirring screen is arranged in the tube at a distance from the outlet of the nozzle channel.

By the expression short channel, we mean in this presentation a channel whose length is of the same order of magnitude as the square root of its section.

With the device according to the present invention, it is possible to inject only the quantity of vapor necessary to bring the fluid product to the desired temperature by condensation on the product of all of the vapor injected. The heated fluid mass can have a high degree of homogeneity at the outlet of the device without any variations in pressure during its path in downstream waiting line being translated into variations in temperature of the injected vapor. This guarantees optimal use of the steam and remarkably stable conditions for sterilization and / or homogenization of the fluid mass.

For the sterilization of low-viscosity products such as milk or whey, the stirring screen can be produced in the form of a diaphragm disposed in the second end or outlet of the tube.

For the sterilization of more viscous products, it is preferable that the diaphragm is brought closer to the nozzle, namely that it is arranged in front of the outlet orifice of the channel of the nozzle, at the branch of the arm and the tube. In another embodiment of the device, for viscous products, the screen is produced in the form of a discharge nozzle disposed axially in the tube, the inner wall of which diverges downstream from a channel of constant cross section, channel whose inlet orifice faces the outlet orifice of the nozzle channel. Preferably, the inlet channel of the discharge nozzle has a section of at least 1.3 times the section of the outlet channel of the injection nozzle.

Yet another embodiment, derived from the above form, is intended not only for sterilization, but also for the homogenization of slightly homogeneous fluid products. In this embodiment, the downstream end of the injection nozzle has a conical surface which widens downstream from the outlet orifice of its channel, the upstream end of the discharge nozzle has a conical surface which converges upstream on the orifice

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inlet of its channel, and the upstream end of the nozzle enters the downstream end of the nozzle, the two ends delimiting between them a conical passage converging upstream on the mixing chamber between the orifice of outlet of the nozzle channel and the inlet port of the nozzle channel.

According to the embodiment of the device, the various elements which constitute it will preferably be made either of stainless steel, or, if the stresses to which the element is subjected allow it, of polytetrafluoroethylene. Thus the T-shaped body, as well as the diaphragms or the homogenization nozzle, will generally be made of stainless steel, while the steam injection nozzle may be made of polytetrafluoroethylene. This latter embodiment has enormous advantages, both in terms of construction and use of the device. In fact, this heat-resistant synthetic material is easy to work, which allows a set of nozzles of different diameters to be formed inexpensively, and it has a very low coefficient of friction, which prevents the formation of deposits and burnt scabs in the nozzle or on its edges. As for the discharge nozzle of one of the embodiments mentioned above, it will, depending on the case, be made more of stainless steel or rather of polytetrafluoroethylene, the latter variant being preferred if the conditions are suitable.

Preferably, the T-shaped body has, at each end of the straight tube and at the end of the tubular arm, means for fixing to pipes of respective respective diameters, these means possibly being a thread or closing elements of the bayonet type. . The fixing of the various elements in the T-shaped body is provided in different ways, depending on their shape or the respective nature. The steam injection nozzle can be retained by a shoulder provided on the periphery of its upstream end and resting on a groove arranged in the interior wall of the inlet of the tube. A similar system can be provided to hold the stirring screen in place at the other end of the tube. The exact position of the screen, namely its distance separating it axially from the nozzle, can be adjusted using a set of seals of different thicknesses to be placed between the groove made in the inner wall of the outlet of the tube. and the shoulder provided on the periphery of the downstream end of the screen. The whole can be held in place by the end of the waiting pipe coming to be fixed on the tube. Another fixing method can be provided, in particular for the homogenization nozzle, namely a thread hollowed out on the downstream end of the nozzle and corresponding to a thread hollowed out in the inner wall of the outlet of the tube. The distance between nozzle and nozzle can be adjusted more easily and finely with this latter method of attachment, but it is then necessary to seal the device by an elastic ring placed between the nozzle and the tube, upstream of the threads.

To use the device according to the present invention, it is possible to connect the inlet of the tube to a supply line for pressurized steam, connect the outlet to a standby pipe and connect the tubular arm to a supply line for the product. fluid to sterilize and / or homogenize. The waiting line can itself be connected by a back pressure valve to a cooling or expansion chamber. Preferably a sufficiently high vapor pressure will be used before the nozzle to fully benefit from the advantages of the present device. Indeed, it is a question of profiting from the law of the critical flow which wants that, for a nozzle of the present type, the speed of the vapor at the exit of the nozzle reaches and does not exceed a limit speed, which is that of the speed of sound in steam, from the moment the pressure at the inlet of the nozzle exceeds approximately twice the pressure at the outlet of the nozzle. The pressure prevailing in the waiting line will preferably be maintained at a value slightly higher than the saturated vapor pressure of water at the chosen sterilization and / or homogenization temperature. The vapor pressure at the inlet of the nozzle must therefore be significantly greater than twice the pressure prevailing in the waiting line, so that the difference between the pressure at

626788

the outlet of the nozzle and the pressure in the waiting line can practically not be filled by accidental fluctuations in the pressure in the waiting line. In this way, these fluctuations cannot be passed upstream of the nozzle and the flow rate and the temperature of the injected vapor remain constant. As for the pressure at which the fluid is injected into the supply arm, it can be chosen from the range defined by the pressure in the waiting line and the pressure at the outlet of the nozzle.

Since we are working in critical regime, the steam flow rate per mm2 of section of the nozzle outlet channel is known as soon as we set the value of the steam pressure at the inlet of the nozzle . Knowing at what temperature and at what flow rate the fluid is introduced into the device and at what temperature it is desired to sterilize it, one can calculate exactly the quantity of steam required and therefore the diameter of the nozzle that must be used. The present device therefore makes it possible to work without waste under constant and well-defined conditions.

The accompanying drawing shows, by way of example, some embodiments of the device according to the present invention.

Figs. 1 to 3 are sections on a 1: 1 scale of three embodiments of the device intended for sterilization and / or homogenization of fluid products of different viscosities.

Fig. 4 is a diagram of an installation which can incorporate a device according to the present invention or other devices and intended for comparative tests.

The device shown in fig. 1 comprises a T-shaped body composed of a straight tube 1 and a tubular arm 2. A nozzle 5 for injecting steam is disposed axially in the inlet 3 of the tube. A stirring screen 6 is disposed axially in the outlet 4 of the tube. The screen consists of a diaphragm 7 mounted at the end of a positioning cylinder 13. With the long cylinder shown in fig. 1, the diaphragm is located in front of the outlet orifice 8 of the channel 9 of the nozzle. This arrangement is favorable for the treatment of very viscous fluids such as flour soups with a high dry matter content, for example. The arrangement of the diaphragm indicated in 10 in dashed lines is suitable on the other hand for the sterilization of liquids which are not very viscous such as milk or whey. The inner wall 11 of the nozzle 5 is conical and converges downstream on the channel 9 which opens through its outlet orifice 8 on the mixing chamber 12, at the junction of the arm 2 and the tube 1. The nozzle 5 is in polytetrafluoroethylene. The T is made of stainless steel, as is the screen 6. The tube 1 has, at its downstream end, an external thread 14 for joining with a standby pipe, and an internal groove 15 on which the shoulder 16 abuts. provided on the periphery of the downstream end of the stirring screen 6. The tube 1 has, at its upstream end, external closing elements 17 of the bayonet type for junction with a steam supply pipe, and an internal groove 18 on which abuts the shoulder 19 provided on the periphery of the upstream end of the nozzle 5. The tubular arm 2 has at its outer end a thread 20 for the junction with a supply line of fluid to be sterilized.

In fig. 2, the same figures represent the same elements as in FIG. 1. However, the stirring screen 6 is produced here in the form of a discharge nozzle made of polytetrafluoroethylene. This device is particularly suitable for sterilizing very viscous fluid products, such as processed cheese for example. The inner wall 21 of the nozzle is conical and diverges downstream from a short channel 22 of constant section, the inlet port 23 of which faces the outlet port 8 of the channel 9 of the nozzle 5 The channel 22 has a section 1.3 times larger than the section of the channel 9.

In fig. 3, the same figures represent the same elements as in FIGS. 1 and 2. However, the stirring screen 6 is produced here in the form of a stainless steel discharge nozzle, the upstream end of which has a conical surface 31 which converges, upstream, on the orifice inlet of its channel 22. The downstream end of the injection nozzle has a conical surface 32 which widens towards

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4

downstream from the outlet orifice of its channel 9 and advances on the upstream end of the nozzle 6, so that these two ends delimit between them a conical passage 33 converging upstream on the chamber of mixture 12 comprised between the outlet port of the nozzle channel and the inlet port of the nozzle channel. This embodiment of the device according to the present invention therefore makes it possible to inject the fluid product to be sterilized into the vapor stream against the direction of this stream, and not perpendicular to, or even in the direction of the stream. This causes a shearing effect of the fluid product stream such that the latter can thus be homogenized. The nozzle 6 is fixed in the tube 1 by an external thread 34 corresponding to an internal thread 38 of the end 4 of the tube, which makes it possible to very finely adjust the distance separating it from the nozzle. However, in the embodiment shown here, the nozzle also has an internal thread 35 in which is fixed a threaded ring 36 supporting a rupture tube 37 intended to reinforce the homogenization effect. The ring 36 is pierced with holes all around the base of the rupture tube to allow the sterilized and homogenized fluid product to pass. This rupture tube 37 is however not necessary to obtain homogenization. It only plays a minor supporting role. To seal the device, an elastic ring 39 is placed between the nozzle and the tube, upstream of the threads 34 and 38. It is held in place by a groove formed in the outer wall of the nozzle. In the embodiment shown here, it is the nozzle itself which carries means for fixing to the waiting pipe.

Fig. 4 schematically represents an installation intended for comparative tests of different devices. The fluid to be sterilized is prepared in the tank 41 and then introduced, under the desired pressure, into the supply line 43 by the pump 42. The pressure and the temperature in the supply line of the fluid are measured by the instruments P2 and Tj. The saturated steam is supplied at the pressure desired by the valve 44 in the supply line 45. The pressure in the supply line is measured by the instrument P i. The temperature at the outlet of the steam injection device 47 is measured by the instrument T2. The product is maintained at the sterilization temperature in the standby line 48, the dimensions of which determine the duration of the treatment. The pressure and temperature at the downstream end of the standby line are measured by the P3 and T3 instruments. In the same terminal area of the holding pipe, 4 instruments TL, TR, TB and TH measure the temperature prevailing on the left, right, bottom and top of the pipe respectively, so as to determine the homogeneity or the inhomogeneity of the current flowing in the pipe. The sterilized product then escapes from the waiting line through the back pressure valve 49 and cools instantly by expansion in an expansion chamber not shown. In this chamber, the condensate of the vapor which has heated the fluid product by condensing there returns to the state of vapor and cools the product by vaporizing.

The following examples illustrate some modes of use of the device according to the present invention and also give the results of some comparative tests. The percentages are given by weight, unless otherwise indicated.

Example 1:

With a device of the type shown in FIG. 1, comprising a T-shaped body whose tube and arm have an internal diameter of 60 mm, a Teflon nozzle (registered trademark) having a channel of 0 14 mm, a diaphragm of 0 20 mm positioned as indicated in 10 , 18000 kg / h of whey serum containing 12% dry matter are heated to a temperature between 40 and 72 ° C. with a vapor pressure, before the nozzle, of 12 bars.

Example 2:

With a device similar to that of Example 1, but with a nozzle channel of 0 18 mm, it is heated to a temperature between 40 and

85 ° C, with a steam of 12 bars before the nozzle, 20,000 kg / h of whey serum with 12% dry matter.

Example 3:

5 With a device similar to that of Example 1, but with a T whose tube and arm have a 0 of 50 mm, 10,000 kg / h of whey serum is heated, the dry matter content of which is 20%, at a temperature between 60 and 75 ° C, with a vapor pressure of 7 bars upstream of the nozzle, the latter having a channel of 0 9 mm.

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Example 4:

With a device similar to that of example 1, but with a diaphragm of 0 8 mm positioned as indicated in 13 in fig. 1 and a Teflon nozzle having a channel of 0 7 mm, it is heated to a

15 temperature between 70 and 150 ° C, with a vapor pressure before the nozzle of 12 bars, 1800 kg / h of condensed milk having a dry matter content of 32%.

Example 5:

In the context of the preparation of a whole milk reconstituted from skimmed milk powder and butter oil, first a skim milk reconstituted with 19.8% dry matter is prepared, a mixture is mixed with it. equal amount of butter oil and this premix is emulsified to obtain a concentrated pre-emulsion. We blend

25 then intimately 16% of the pre-emulsion and 84% of skimmed milk reconstituted to obtain the finished product of the desired composition.

The premix is emulsified at a temperature of at least 40 ° C with various devices or devices as follows:

3o A) Using a Fryma cone mill type LSR / 80/61 rotating at 2900 rpm for a power of 9 kW: the mill is fed at the rate of 30 kg of premix per minute (Aj) or 60 kg / min (A2) by opening the stator 14 turns and 2 turns respectively.

B) With a Reactron gear mill type TDLK

35 3-55: the premix is carried out using a diaphragm placed at

the entrance to the mill. The mill is fed at a rate of 101 / min (BJ or 201 / min (B2).

C) With a Supraton mill with toothed crown type 305

4Q rotating at 5400 rpm: the premix prepared as in B is introduced into the mill at the rate of 10 kg / min (CJ or 20 kg / min (C2).

D) With a Brogli mill with a toothed crown type Steril M-II rotating at 2900 rpm: the premix is prepared as in B.

45 feeds the mill at 10 kg / min (Dj) or 20 kg / min (D2).

E) With a device according to the present invention of the type illustrated in FIG. 3, where the T comprises a tube and an arm of 0 35 mm each, the nozzle channel has a 0 of 5 mm and a length of 10 mm, leading to a conical outlet of 60 ° opening, the nozzle in steel has an inlet channel of 0 5 mm and 7 mm in length, fitting into the flared end of the nozzle so that a conical passage of 60 ° opening and about 0.5 mm of thickness remains free for the flow of the premix (it is therefore projected at high speed against the jet of steam leaving the nozzle channel, then violently entrained in the inlet channel of the nozzle): a flow rate of 5 kg of premix per minute (EJ or 10 kg / min (E2), with a vapor pressure before the nozzle of 1.1 or respectively 3.2 bar, which causes a rise in temperature from 40 to 90 ° C.

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Each pre-emulsion is then intimately mixed with the desired percentage of skimmed milk reconstituted using a traditional brewer rotating for a few minutes at around 300 rpm. We observe under the microscope the fineness of the droplets of butter oil in

65 suspension then the separation of the cream is determined over time. The results are grouped in Table I. The separation of the cream is indicated in% by volume of separated cream:

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Table I

626,788

Case

Separation of the cream in% by volume after

Average dimensions of oil globules, 0 in (i

Apparatus

• At h lh

2h

3h

24h

Al

0

0

<1

1

10

4-12

Fryma

A2

1

2

2.5

3

10

8-15

Fryma

B1

0

0

0

0

7

4-8

Reactron

B2

0

0

0

0

7

4-8

Reactron

Cl

0

0

0

0

2

3-5

Supraton

C2

0

0

0

0

2

3-5

Supraton

D1

1

1

3

4

14

10-20

Brogli

D2

0

0.4

1

2

12

10-20

Brogli

El

0

0

0

0

2

3-6

Invention

E2

0

0

0

0

0

5-8

Invention

Table II

Trial No

<d Ck h

Note

Pi

P2

P3

Ti

T2

T3

Th

Tb

Tl

Tr

1

Reference

Injection speed into the mixing chamber

0.2 m / s

8, '5-9

6.5

4-6.

31

130

135

149

121

149

"l49

2

8.3-8.5

6.3

3.8-5.5

27

117

132

147

119

138

141

3

6.5

4.8

2.4-3.2

26

112

123

134

120

127

133

4

8.5-9

6.8

4-6

26

114

134

149

118

141

143

5

0.3 m / s

8

6.5

3.5-5

24

120

138

139

108

129

127

6

6.5

5

2.5-3.2

24

116

129

131

108

123

123

7

8.5

7

4.5-5.5

22

120

142

143

108

136

130

8

Invention

Nozzle channel diameter

5 mm

11

6-7

5-6.5

23

134

136

152

120

147

145

9

7

4-5

3-5

26

120

125

134

122

122

128

10

7

4-5

2.5

26

120

124

131

122

122

126

11

16

4-6

4-6

23

128

135

146

• 126

145

135

12

6

4

3-4

24

130

128

137

126

137

130

13

16

3-4

2.5

25

132

127

135

126

135

135

Thus, the results obtained with a device according to the present invention are among the best, even the best, while its construction is the simplest, its cost is the most modest and its use is the easiest.

Example 6:

An installation is used as illustrated in FIG. 4 to compare the performance of the device described in fig. 2 and those of a known device with two convergent-divergent nozzles, as described in the introduction to this presentation and used in the traditional way. The Tl5 T2, TH, TB, TL and TR instruments are thermocouples connected to a multi-track recorder. The T3 instrument is a mercury thermometer. The product to be sterilized is an aqueous slurry with 60% dry matter, prepared from 50% cereal flour, 25% sugar and 25% whole milk. It is delivered by pump 42 at a rate of 400 kg / h. The standby line is 2 m long and has an internal diameter of 35 mm. The T-shaped body has a tube and an arm of 0 35 mm, both for the device according to the present invention and for the reference device. The latter comprises two convergent-divergent stainless steel nozzles of adjustable relative position which have at their narrowest part a diameter of 20 mm each. The

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device according to the invention comprises a tetrafluoroethylene nozzle having a channel of 0 4 or 5 mm and a tetrafluoroethylene nozzle having an inlet channel of 0 7 mm, the distance between the outlet orifice of the channel of the nozzle and l the inlet opening of the nozzle channel being 5 mm. Tests are carried out for different pressures Pt of the vapor upstream of the nozzle or of the injection nozzle.

The results of these tests are collated in Table II. The pressures are indicated in bars and the temperatures in degrees Celsius.

(See previous page)

Under the heading Note, it was indicated for the reference device that one worked at two speeds of injection of the product into the mixing chamber by moving one of the nozzles axially. By mixing chamber is meant, in this case, the converging part of the inlet of the second nozzle into which the diverging outlet of the first nozzle opens.

It is noted that a much better homogeneity of the temperatures Th, Tb, Tr and Tl has been obtained during the tests with the device s according to the present invention. During the tests with the reference device, it was not possible to avoid a separation of the flow in the standby line into a creeping current of thick product and a rapid and hotter current of excess vapor which flows over the product. This separation could be largely avoided during tests with the device according to the present invention, without having to deplore the formation of plugs. This allows all the material to be treated under the same conditions, to keep these conditions constant over time and to avoid wasting the steam.

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2 sheets of drawings

Claims (11)

626788 1. Device for sterilization and / or homogenization of a fluid product by steam injection, comprising a T-shaped body composed of a straight tube and a tubular arm for supplying the fluid product, and a nozzle steam injection device arranged axially in a first end or inlet of the tube and leading to a mixing chamber at the branch of the arm and the tube, characterized in that the inner wall of the nozzle converges downstream on a short channel of constant section leading to the mixing chamber, and by the fact that a stirring screen is arranged in the tube at a distance from the outlet of the nozzle channel. 2. Device according to claim 1, characterized in that the screen is a diaphragm. 2 3. Device according to claim 2, characterized in that the diaphragm is arranged in front of the outlet orifice of the nozzle channel, at the branch of the arm and the tube. 4. Device according to claim 2, characterized in that the diaphragm is arranged in the outlet end of the tube, downstream of the branch of the arm and the tube. 5. Device according to claim 1, characterized in that the screen is a discharge nozzle disposed axially in the tube, the inner wall of which diverges downstream from a short channel of constant section, channel whose l the inlet port faces the outlet port of the nozzle channel. 6. Device according to claim 5, characterized in that the inlet channel of the discharge nozzle has a section at least 1.3 times larger than the section of the outlet channel of the injection nozzle. 7. Device according to claim 5, characterized in that the downstream end of the injection nozzle has a conical surface which widens downstream from the outlet of its channel, and by the causes the upstream end of the discharge nozzle to have a conical surface which converges upstream on the inlet opening of its channel, the upstream end of the nozzle penetrating into the downstream end of the nozzle and the two ends delimiting between them a conical passage converging upstream on the mixing chamber between the outlet port of the nozzle channel and the inlet port of the nozzle channel. 8. Device according to claim 1, characterized in that the steam injection nozzle is made of polytetrafluoroethylene. 9. Device according to claim 2, characterized in that the diaphragm is made of stainless steel. 10. Device according to claim 5, characterized in that the discharge nozzle is made of polytetrafluoroethylene. 11. Device according to claim 7, characterized in that the discharge nozzle is made of stainless steel.