US2690329A - Device for homogenizing liquids - Google Patents

Description

Sepfi. 2, 11954 K. E. RESSLY 2,690,329

DEVICE FOR HOMOGENIZING LIQUIDS Filed Oct. 24, 1951 INVENTOR. Ku/vo ET/E/v/VE GFESSLY.

flTTU/WVEK Patented Sept. 28, 1954 DEVICE FOR HOMOGENIZIN G LIQUIDS Kuno Etienne Gressly, Konolfingen, Switzerland, assignor, by mesne assignments, to Alpura A. G., Bern, Switzerland Switzerland, a corporation of Application October 24, 1951, Serial No. 252,967

Claims priority, application Switzerland October 25, 1950 5 Claims. 1

This invention relates to devices for homogenizing liquids, for the purpose of preventing the tendency to separation or sedimentation of substances suspended in the liquids.

Devices which are customarily employed for homogenizing liquids, more especially milk, are bulky and heavy because of the high pressures used in the treatment, for example 100 to 300 kg. per square centimeter, and consequently they are very expensive. Their capacity in relation to their size and the power consumed is relatively small; it amounts on an average to not more than 5,000 to 6,600 liters per hour. These devices are equipped with conveying devices for the liquid to be treated, valve controlled piston pumps being used in most cases. Such devices are not readily adaptable to continuous processes because the amount of milk or other liquid treated per time unit in a preceding operating stage, for example in a heating device, does not, in the great majority of cases, conform with the operating capacity of the homogenizing devices. This disadvantage usually necessitates the provision of a storage container between the homogenizing device and the preceding operating stage, which interrupts the continuous flow of liquid through the plant.

It is also known that the high pressures hitherto used in homogenizing processes may have an adverse effect on the liquids being treated and on the substances suspended in them, especially when the liquids are subjected to a subsequent heat treatment for the purpose of sterilization. The eiiect of the high pressures can vary considerably, especially in the case of milk, according to the composition of the milk which may vary at different seasons of the year and according to its acidity. This makes it difiicult to treat the milk continuously and to obtain a uniform final product, for example condensed milk, and, if a continuous treatment is to be performed, some reduction in quality must usually be accepted.

Conventional homogenizing devices cannot easily be sterilized because of their complicated construction. There is thus a considerable risk of infection of the liquids flowing through the devices, and they cannot be used in a continuous production process under sterile conditions. There must therefore be a sterilizing operation after the homogenizing process. The necessity for sterilizing the liquid after homogenization makes it impossible to restore a stable suspension or emulsion in a liquid which has begun to separate or to form a sediment because of the effect of the heat treatment during the sterilization subsequent to the original homogenizing process.

It is an object of the resent invention to provide a device for homogenizing liquids in Which the aforementioned disadvantages of conventional devices are reduced or eliminated.

The device for homogenizing liquids according to the present invention comprises an impact system in the form of a plurality of stationary, spaced plates, each plate having an aperture and the apertures being disposed along a continuous line, the liquid to be treated passing through the apertures in a stream of such form that the edge of each aperture intercepts a peripheral part of the stream, whereby partial amounts of the liquid are separated from the stream at each plate and are deflected laterally into the spaces between the plates.

There is preferably an end plate having no aperture farthest from the point at which the jet enters the impact system.

It is desirable that the apertures in the plates decrease progressively as the distance of the plates from the point of entry of the stream or jet increases.

In one embodiment of the invention, a displacement body extends through the apertures in the plates partially obstructing the apertures. The displacement body may be in the form of a cone whose point is directed toward the jet. The displacement body is preferably movable in the direction of the axis of the jet.

The distance between adjacent plates preferably should increase as the distance from the point of entry of the jet increases.

The impact system may be surrounded by a cylindrical impact wall disposed coaxially with the axis of the jet. The streams of liquid diverted from the jet by the plates impinge upon this impact wall.

In one embodiment of the invention, the liquid is forced at high presure through a pressure reducing nozzle, from which the liquid emerges in the form of a high velocity jet directed toward the apertures in the plates. The nozzle may form part of an ejector to which a compressible operating medium is supplied whose pressure is reduced in the ejector for accelerating the jet of liquid. A gaseous or vaporous heat carrier may be used as the operating medium.

Preferably, the liquid outlets from the impact system are connected with a container in which a sub-atmospheric pressure can be maintained.

The invention may be performed in various ways, one particular embodiment being described by way of example with reference to the accompanying drawings in which;

Figure 1 is a sectional elevation of the device;

Figure 2 is a diagram of a plant for the treatment of milk, which plant is provided with a homogenizing device such as that shown in Figure 1.

In the device shown in Fig. l, the liquid to be treated is continuously introduced through a pipe I under high pressure into a pressure reducing nozzle 2, from which it emerges in the form of a high velocity jet. The nozzle 2 is mounted in a body 3 to which is screwed the end connection of the pipe I. Bearing against a shoulder of the body 3 is a retaining disc 4, which is pulled down by screws 5 toward a flange 5, which is welded into an opening in the top of a container 1 receiving the treated liquid. Pitted inside the flange e is an annular body 3, a packing ring 9 being pressed between this body and the body 3.

The outlet of the nozzle 2 opens into a cylindrical passage formed in members 3 and 8. This passage leads to an impact system consisting of a plurality of concentrically disposed circular plates it. These plates are provided with holes through which extend bolts H spaced at 120 around the axis of the plates. The bolts are screwed into the member 8. The plates 18, with the exception of the end or terminal plate ma, are of uniform thickness and are spaced from each other by means of three sets of spacers 12, which are also spaced at 120 about the axis of the plates and are each attached to one side or" one of the plates. The bolts ll are threaded at their free ends to receive nuts IS, the nuts bearing against the end plate Illa and firmly securing the plates together.

Each plate is has a central aperture M, the apertures forming a flow channel for the liquid to be treated, which channel is aligned with the nozzle 2. The flow area of the apertures decreases with increasing distance from the jet nozzle 2. The edge of each subsequent aperture thus projects a little farther into the flow path of the jet than the edge of the preceding aperture and deflects some of the liquid through 90, the deflected liquid being discharged radially outwards through the space between the plates. The spacers i2 situated nearest to the body 8 are thinner than the spacers which are farther away, so that the distance between adjacent plates progressively increases as the distance from the body 8 increases. In this way, despite the fact that the jet velocity decreases with increasing distance from the nozzle 2, approximately the same amounts of liquid are discharged through all the spaces between the plates. The momentum of the portions of liquid deflected from the jet is sufficient to hurl the liquid against an impact wall it which is open at its lower end and forms a conduit means surrounding the plate system. The liquid running oii from the impact wall i5 is collected at the bottom of the container I and can be passed to a discharging device, not shown, for example a cooler.

The device can be produced comparatively simply, and its cost is only a fraction of that of conventional homogenizing apparatus.

Arranging the plates so that the size of the apertures i i decreases in the flow direction of the liquid makes it possible to deflect the liquid to be treated in small partial amounts and thus to subject all liquid particles, with the substances contained in them which may tend to separate or form a sediment, to an effective impact against a plate and to a sudden change of direction.

The distances between the individual plates are preferably so chosen that the partial amounts of liquid conducted radially outwards fiow with high turbulence through the spaces between the plates, the kinetic energy which they still contain being destroyed by the impact on the impact wall 95.

Atmospheric pressure may prevail in collecting container 7. It is desirable, however, to connect the interior of the container with a device, not shown, for maintaining a partial vacuum therein. The resulting sudden pressure drop of the liquid introduced under high pressure through the pres sure reducing nozzle promotes to a great degree the homogenizing effect of the device.

The homogenizing effect can also be increased considerably by providing a displacement body 55 which partially fills the apertures 12 in the plates. This displacement body can be rigidly connected to the end plate tea or, as the figure shows, be mounted in a supporting member ll welded to the end plate so as to be adjustable in the direction of the axis of the jet. A set screw 48 is provided for holding the displacement body in the desired position. With the exception of the part held in the supporting member ii, the displacement body !6 is of conical form with its point facing the nozzle 2. The jet of liquid emerging from the nozzle 2 at high velocity news along the surface of the displacement body which forms a core around which a jet of liquid of annular cross-section is formed. One advantage of this arrangement is that the homogenizing effect is considerably increased by the greatly increased liquid friction produced by the formation of a boundary layer on the surface of the displacement body. The displacement body also prevents N the phenomenon which might occur in a full jet without displacement body, whereb individual liquid particles in the core of the full jet are subjected to a less abrupt deflection at the edges of the plate apertures i l.

The device embodying the invention is especially suitable for incorporation in a continuous liquid treatment process. in particular, the conical construction of the adjustably disposed displacement body makes it possible to adjust the device to suit the properties of the liquid and the amount of liquid to be treated per time unit, without adversely affecting the homogenizing effect. Advancing the displace sent body towards the jet of liquid decreases the how area of the individual plate apertures. By this adjustment, velocity conditions which are essential for obtain ing a satisfactory homogenizing effect, can be produced for different amounts of liquid flowing per time unit.

In certain cases it is desirable to increase additionally the velocity of the jet of liquid introduced into the plate apertures. For this purpcse, the channel in the body 3 surrounding the outlet of the nozzle 2 is constructed like an ejector, and a compressible medium is introduced under pressure into the how path of the jet by means of a connecting pipe screwed into a threaded apc l9. The compressible operating medium ca es an acceleration of the jet of liquid while its pressure is reduced. An inert gas, for example nitrogen, can be used as operating medium. In many cases, it is desirable to use a gaseous or vapor-nus heat carrier, for example steam, as operating medium, the heat transferred from the operating medium to the liquid serving for heating th; liquid to the sterilization temperature.

All parts of the device which come into contact with the liquid to be treated are made of stainless steel and can be easily cleaned. By passing steam through the device before putting it into operation, it can be heated to the sterilization temperature whereby all harmful bacteria are killed, which is of great importance in the treatment of liquid foods, such as milk. The device has no parts which are inaccessible for cleaning and which could become sources of infection, so that continuous operation under sterile conditions is possible after the device has been sterilized. Therefore, if liquids which have been sterilized in a previous operating stage are treated in the present device, re-sterilization by renewed heating of the already homogenized liquid is unnecessary. The liquid discharged from the collecting container can be filled directly into sterile Vessels under aseptic conditions, there being no incubation danger and no heat treatment after the homogenization which may impair the homogenizing efiect.

These advantages render the device especially suitable for the treatment of milk and liquids containing milk, which, in a preceding treatment stage, have been subjected to a heat treatment for the purpose of killin the bacteria and disease germs contained in the liquid, for example, pasteurized fresh milk and condensed milk. It is known that milk-containing liquids can easily be changed into an unstable condition by a heat treatment, in which condition salts and albuminous substances tend to sedimentation, which adversely affects the taste and keeping qualities of the liquids. This tendency to sedimentation is especially pronounced in milk produced in certain periods of lactation, in milk which has been stored for long periods, and in already condensed milk, when such liquids are sterilized by heating either previous to or after filling into tins. With the device according to the invention, such liquids can be treated, under sterile conditions, for stabilizing the substances tending to sedimentation.

An example of a simple plant for the treatment of fresh milk and condensed milk is shown diagrammatically in Figure 2.

The fresh milk or unsweetened condensed milk to be treated is conducted continuously and under high pressure, for example kg./cm. by means of a gear pump 2! through a pipe 22 into a heating device 23. This heating device is connected through a pipe M with a steam generator, not shown, and effects the almost instantaneous heating of the milk to a temperature of 200 centigrade, for example, by introduction of steam into the flow path of the milk to be treated. This heat treatment completely destroys bacteria and disease germs. In order to prevent a disagreeable boiled taste and the destruction of vitamins, the temperature of the thus heated milk must be decreased immediately thereafter. For this purpose, the milk is discharged from the heating device 23 through a pipe 25 and is conducted into a collecting container 26, a homogenizing device 27 as shown in Figure 1 being disposed at the point where the pipe 25 enters the container. While flowing through the homogenizin device 21', the pressure of the milk is reduced and its temperature is adjusted instantly to the temperature of saturated steam corresponding to the reduced pressure in the container. The vapors released from the milk at the reduction of pressure are drawn off through a pipe 28 and. pass into a droplet separator 29, from which any liquid particles which were entrained in the vapor can flow back through a pipe 30 into the interior of the container '26. The droplet separator 29 is and composition during storage.

connected with a steam jet ejector 3|, which is supplied through conduit 32 with live steam from the pipe 24. This steam, together with the vapors drawn off from the container 26, may be conducted in expanded state through a pipe 33 to other apparatus and may serve, for example, as the heating medium of a heat exchanger for preheating the milk to be treated. With the aid of ejector 3|, an adjustable partial vacuum can be produced in the interior of the container 26, so that the homogenized and sterile milk discharged from the container through a pipe 34 has a temperature which is below its boiling point at atmospheric pressure. The discharge pipe 34 is connected with a gear pump 35, which conveys the milk into other apparatus, for example, into a cooler. The homogenizing device 21 has an ejector nozzle, to which steam tapped from pipe 24 can be supplied through a pipe 36 as operating medium for accelerating the liquid flow through the nozzle. The amount of steam flowing through conduit 36 can be adjusted by manipulation of a valve 31 to suit the prevailing operating conditions.

In milk treated according to the invention, the salts and albuminous substances are converted into a stable emulsion which, because of the preceding sterilization, can be kept for a long time under aseptic conditions. If the milk is filled into sterile containers, it can be kept almost indefinitely without its quality being reduced by disagreeable alterations in taste, color,

The homogenizing efiect obtained by the device according to the invention produces such an extensive break-up of the fat particles that fresh milk, for example, no longer creams up during prolonged standing. Sweetened condensed milk which was treated by the device proved to be stable even in the case of selected samples of compositions having a high content of fat-free solids during the whole lactation period. Treatment according to the invention to a great extent prevents undesirable thickening of the milk product.

The device is also suitable for the treatment of a number of other liquids, particularly for the treatment of liquid foods and beverages which originally contain substances or to which substances are added during the treatment which must be converted into stable emulsions or suspensions. Especially good results were obtained by the treatment of fatty emulsions, as well as extracts from animal and vegetable substances. The device according to the invention can also be successfully used in various processes for manufacturing chemical products.

The invention is, of course, not restricted to the exact details of design and construction shown and described, for obvious modifications will occur to a person skilled in the art; for example, more than one row of apertures may be provided in the plate system, through which passes a liquid divided into a plurality of jets, without departing from the scope of the present invention.

I claim:

1. A device for homogenizing liquids, comprising an impact system including a plurality of spaced substantially parallel stationary plates, an aperture in each plate, said apertures being arranged coaxially along a straight line, an expansion nozzle for discharging the liquid to be homogenized in the form of a jet through said apertures, said apertures having edges individually intercepting liquid at the periphery of the jet and deflecting the intercepted liquid into the spaces between said plates radially away from said apertures, and conduit means having a portion surrounding said plates and receiving the deflected liquid from the spaces between the plates.

2. A device for homogenizing liquids, com. prising an impact system including a plurality of spaced substantially parallel stationary plates, an aperture in each plate, said apertures being arranged coaxially along a straight line, an ejector means comprising an expansion nozzle discharging the liquid to be homogenized in the form of a jet through said apertures, said ejector means comprising supply means for an expansible medium for accelerating the flow velocity of the jet, said apertures having edges individually intercepting liquid at the periphery of the jet and deflecting the intercepted liquid into the 4. A device for homogenizing liquids, comprising an impact system including a plurality of spaced substantially parallel stationary plates, an aperture in each plate, said apertures being arranged along a continuous line, means for flowing the liquid to be homogenized in the form of a jet through said apertures, said apertures having edges individually intercepting liquid at the periphery of the jet and deflecting the intercepted liquid into the spaces between said plates, and a vacuum chamber connected with said impact system for receiving the liquid therefrom after it has been homogenized there- 1n.

5. A device for homogenizing liquids, comprising an impact system including a plurality of spaced substantially parallel stationary plates, an aperture in each plate, said apertures being arranged coaxially on a straight line, means for flowing the liquid to be homogenized in the form of a jet through said apertures, said apertures having edges individually intercepting liquid at the periphery of the jet and deflecting the intercepted liquid into the spaces between said plates radially away from said apertures, and conduit means having a portion surrounding said plates and receiving the deflected liquid from the spaces between the plates, the spacing between said plates increasing in the flow direction of the jet.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,641,485 Heftler Sept. 6, 1927 2,042,462 Hahn June 2, 1936 2,132,854 Knott Oct. 11, 1938 2,203,130 Costello June 4, 1940 2,426,238 Platon Aug. 26, 1947 2,471,667 Arnold May 31, 19i9

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