EP0515914B1 - Homogenising machine and its method of operation - Google Patents

Description

The invention relates to a homogenizing machine for homogenizing liquids such as emulsions or suspensions, with at least one working space and displacer arranged therein for increasing the pressure with at least one supply and at least one discharge line per working space, which are each provided with an inlet or outlet valve, and a gap for the homogenization and a method for operating such a homogenizing machine, in which a liquid to be homogenized is conveyed through a gap.

Homogenizing machines are used in a variety of ways in process engineering. For example, milk or ice cream is homogenized in food technology.

The liquid to be homogenized is increased in its pressure in a working space with at least one supply and at least one discharge line per working space, which are each provided with an inlet or outlet valve, by means of a displacer. A plunger is used as a displacer, which is guided through a hole in the housing into the work area. The seal between the plunger and the housing is subject to constant rubbing stress due to the oscillating movement of the plunger. Wear particles and possibly additional lubricants can be introduced into the liquid to be homogenized.

The liquid which is increased in pressure is fed through the outlet valve to a gap in which the actual homogenization process takes place. The gap is usually circular as a distance between a stamp and the end of a bore through which the liquid to be homogenized is passed to the end face of the coaxially arranged stamp, in order to then flow outwards through the annular gap formed.

Wear occurs in such arrangements. For example, it is known from German patent DE 37 28 946 to reduce mechanical wear caused by polycrystalline shaped diamond parts. This wear is particularly undesirable in the case of liquids that are sensitive to contamination and that have a particularly high level of purity.

The object of the invention is therefore to provide a homogenizing machine and a method for operating one with which the process liquid is exposed to a reduced risk of contamination or a wear-related leakage of process medium is avoided. This object is solved by the features of claims 1 and 14.

Because a membrane is provided between the displacer and the liquid to be homogenized, the liquid to be homogenized is hermetically separated from the displacer. The membrane itself acts as a displacer. However, since it is not subject to abrasive wear, the risk of contamination of the liquid to be homogenized is reduced. The wear particles of the plunger remain in a liquid-filled space between the membrane and the plunger.

In addition, the wear-related, inevitable leakage of process medium through the gap between the oscillating plunger and plunger seal is excluded. This is particularly advantageous when homogenizing toxic, environmentally hazardous media.

If a plate membrane is provided as the membrane, proven designs can be used which can also be used for particularly high pressures. A roller membrane can be advantageous, particularly at low pressures, since relatively large volumes can be displaced with small diameters.

Steel membranes have advantages in particularly aggressive media or high temperatures.

If several membranes are switched to work on a common homogenizing gap, the flow rate can advantageously be evened out by clever switching of the different membranes.

It is particularly favorable if the membrane is designed as a displacer with a hydraulic template as a displacer, since the membrane protects the process fluid from wear particles of the plunger. The uniform hydraulic flow to the membranes enables the process medium to be conveyed uniformly.

It is particularly indicated when an odd number of displacers with associated membranes is interconnected, since an odd number Work cycles with a phase shift known in the art have a more uniform delivery characteristic than an even number of displacers. Due to the compressibility of the hydraulic supply, the membranes produce a non-uniformity in the delivery curves of the liquid to be homogenized. Before the outlet valve of the work area opens, the process fluid and the hydraulic oil of the hydraulic supply in the work area must first be compressed by the plunger via a so-called loss path. The longer the compression piston travel, the greater the piston speed when opening the exhaust valve, so that the valve no longer opens gently, but opens spontaneously. This sudden increase in the volume flow has an adverse effect on the homogenizing effect. The same thing happens in the suction phase. The inlet valve opens only after the hydraulic reservoir contained in the cylinder chamber is relaxed by the drive piston.

The measure that the membrane is equipped with a leakage indicator also helps to secure the process fluid from contamination.

As a further measure to equalize the volume flow, it is provided that a pressure accumulator is connected between the gap and the working space. A hydraulic pressure compensator has proven particularly advantageous here, by means of which the actual pressures and volume flows present in high-pressure homogenization systems can also be advantageously compensated.

To homogenize the homogenization result, it is further provided that several gaps are formed one behind the other, that is, from an alternating one Arrangement of edges and subsequent compression spaces. This arrangement surprisingly reduces the energy requirement when homogenizing milk and the like. Liquids.

The loss paths occurring in the case of compressible liquids or at particularly high pressures are advantageously reduced if the hydraulic receiver has fillers. Spherical additives that have a lower compressibility than the hydraulic medium of the template can serve as filler. If at the same time the density of these packing elements is lower, the dynamics are also improved.

The investment costs for such a system are reduced if the hydraulic supply is designed to be driven by plungers with a common crankshaft and preferably has a common housing.

For larger throughputs, it is advantageous if several groups of 3 work rooms each are connected to work on a common homogenizing gap or a plurality of homogenizing gaps connected in parallel, the groups preferably having working cycles that are out of phase by approximately 60 °.

The process task is solved in that the process liquid to be homogenized is supplied to the gap with approximately constant volume flow under pressure, the stamp in the homogenizing valve remains largely at rest, so that it has a has less wear. At the same time, the homogenization result is advantageously influenced.

The equalization of the volume flow by means of a pressure accumulator, which is connected to a line between the membrane and the gap, has proven to be a particularly cost-effective measure.

The uniformity is further improved if several work rooms convey together on one gap.

Figur 1

ein Schema der erfindungsgemäßen Homogenisiermaschine mit drei Arbeitsräumen in paralleler Anordnung,

Figur 2

eine typische Druckkurve der Prozeßflüssigkeit nach Figur 1 und

Figur 3

eine Druckkurve bei veränderten Verhältnissen.

The invention is illustrated in 3 figures. The figures show in detail:

Figure 1

1 shows a diagram of the homogenizing machine according to the invention with three working spaces in a parallel arrangement,

Figure 2

a typical pressure curve of the process liquid according to Figure 1 and

Figure 3

a pressure curve with changed conditions.

In FIG. 1, the line with which the process liquid to be homogenized is supplied is designated by number 1. Depending on the viscosity, the process liquid is supplied under a pre-pressure of approx. 1 to 5 bar. The line 1 branches to three inlet valves 2, 2 ', 2''of three diaphragm housings 3, 3', 3 ''. Within the membrane housings 3, 3 ', 3''there is a membrane 4, 4', 4 '', which separates the working spaces into the process liquid space 5, 5 ', 5''and the template space 6, 6', 6 '' Splits. The template spaces 6, 6 ', 6''of the membrane housing 3, 3', 3 '' are connected to the connecting lines 7, 7 ', 7'' Cylinder rooms 8, 8 ', 8''in connection. The plungers 9, 9 ′, 9 ″, which are driven by the common crankshaft 10 to which a suitable motor 11 is coupled, move in the cylinders.

The hydraulic medium contained in the cylinder spaces 8, 8 ', 8' 'of the connecting lines 7, 7', 7 '' and the template spaces 6, 6 ', 6' 'of the membrane housing 3, 3', 3 '' is from the plungers 9, 9 ', 9' 'alternately pushed out of the cylinder rooms 8, 8', 8 '' and sucked in again. This creates a hydraulic coupling with the membranes 4, 4 ', 4' 'which in turn suck in the process liquid flowing through line 1 through the inlet valves 2, 2', 2 '' and then expel them through the outlet valves 12, 12 ', 12' ' .

The product leaving the outlet valves 12, 12 ′, 12 ″ under high pressure is brought together again into a common volume flow in the pressure line 13 and fed to the homogenizing valve 14. Using pressures, usually between 150 and 1000 bar, the process liquid is pressed through a narrow gap 15. When entering the gap, the liquid pressure is suddenly converted into speed, in addition to turbulence and shear, cavitation occurs when the vapor pressure falls below. After flowing through a cavitation and turbulence zone, the process liquid strikes an annular surface 16, being subjected to a further shear stress and then being passed through the product outlet 17 without pressure.

The homogenizer gap 15 in the homogenizing valve 14 is known to be formed by a plunger 18 which is movably supported within a bore and is hydraulically supported by a pressurized liquid in bore 19. The hydraulic support is connected to a pressure source 21 via line 20.

With the pressure line 13, a surge tank 22 is also communicatively connected via line 23.

The volume of the hydraulic templates for the diaphragm housing 3, 3 ', 3' ', which is further increased by the connecting lines 7' 7 ', 7' ', has a fundamentally negative effect on the efficiency of the overall system. This is explained in FIG. 2.

The graphs 30, 30 'and 30' 'represent the ideal pressure curves in front of the gap. The working cycles of the membranes are offset from one another by 120 ° phase angle. The individual pressure curves overlap to the sum curve 31.

The resulting mean pressure is indicated by a dash-dotted line 32.

The relatively large volume of the hydraulic template, which is composed of template spaces 6, 6 ', 6''connecting line 7, 7', 7 '' and cylinder space 8, 8 ', 8'', leads to the fact that due to the compressibility of the contained process fluid piston 9 during a work cycle must first compress this until finally that pressure is reached at which the outlet valve 12, 12 ', 12''opens. The pressure curve 33, 33 ', 33''in FIG. 3 shows such behavior. The mean pressure 34, shown in dash-dot lines, is dropped significantly compared to the mean pressure 32 in FIG. It can be seen from FIG. 3 that the quantities expelled from the individual work spaces no longer overlap in time. The volume flow to the valve is therefore inconsistent. The example shown in FIG. 3 has a complete decoupling for a period of about 30 °, ie there is no homogenization. Over an initial angular range of 85 °, which corresponds to the compression path of the liquid contained in the membrane housing 3, 3 ', 3'', the line 7, 7', 7 '' and the cylinder 8, 8 ', 8'' single membrane not. The longer this compression path, the greater the piston speed when the pressure valve is opened, so that the valve no longer performs the desired smooth movement sequence, as shown in FIG. 2, but spontaneously opens. This is reflected in the sudden increase in pressure according to pressure curve 33, 33 ', 33''before the gap. This also has a negative impact on the homogenization effect. The hydraulically supported stamp, which forms the homogenizing gap, has to cope with this uniformity, the stamp completely closing the gap at a high frequency. According to the invention, this disadvantageous behavior, which can lead to increased wear and to contamination of the process liquid, is prevented by the measure according to the invention. The pressure of the machine according to the invention is designated by number 35 in FIG. It fluctuates only slightly around the mean pressure, which is marked with number 34. This behavior is achieved by pressure accumulator 22 (FIG. 1), which advantageously smoothes the product stream to be homogenized.

REFERENCE SIGN LIST

1

Head (product)

2.2 ', 2' '

Inlet valve

3rd

Membrane spaces

4th

membrane

5.5 ', 5' '

Process fluid space

6

Template room

7

Connecting line

8th

Cylinder space

9

Plunger

10th

crankshaft

11

engine

12th

Exhaust valve

13

Pressure line

14

Homogenizing valve

15

gap

16

Ring surface

17th

Product outlet line

18th

stamp

19th

drilling

20th

management

21

Pressure source

22

surge tank

23

management

26

27

28

29

30th

Pressure curve

31

Pressure curve

32

medium pressure

33

Pressure curve

34

medium pressure

35

print

Claims (16)

1. Homogenising machine for homogenising liquids such as emulsions or suspensions, with at least one working chamber (5, 6, 7, 8) and displacing element arranged therein for increasing the pressure, with at least one supply line (1) and at least one discharge line (13) per working chamber, which are each provided with an inlet valve (2) or an outlet valve (12), as well as a gap (15) for the homogenisation which is located downstream of the outlet valve, characterised in that a membrane ((4) is provided between displacing element and liquid to be homogenised.
2. Homogenising machine according to Claim 1, characterised in that by way of membrane (4) a disk-type membrane is provided.
3. Homogenising machine according to Claim 1, characterised in that by way of membrane (4) a roller-type membrane is provided.
4. Homogenising machine according to Claim 1, characterised in that by way of membrane (4) a steel membrane is provided.
5. Homogenising machine according to Claim 1, 2, 3 or 4, characterised in that several membranes (4) in associated working chambers (5) are fitted so as to act upon a common homogenising gap (15).
6. Homogenising machine according to Claim 1, 2, 3, 4 or 5, characterised in that the membrane (4) is designed to be impinged by a plunger (9) with hydraulic receiver by way of displacing element.
7. Homogenising machine according to Claim 6, characterised in that an odd number of displacing elements are connected together.
8. Homogenising machine according to Claim 1, 2, 3, 4, 5, 6 or 7, characterised in that the membrane (4), inasmuch as it is a double membrane, is equipped with a leakage indicator.
9. Homogenising machine according to Claim 1, 2, 3, 4, 5, 6, 7 or 8, characterised in that a pressure reservoir (22) is connected between homogenising gap (15) and working chamber (5).
10. Homogenising machine according to one or more of the preceding claims, characterised in that several homogenising gaps (15) are arranged in series.
11. Homogenising machine according to one or more of the preceding claims, characterised in that the hydraulic receiver comprises fillers.
12. Homogenising machine according to one or more of the preceding claims, characterised in that the hydraulic receiver is designed to be driven by plungers (9) with a common crankshaft (10) and preferably has a common housing.
13. Homogenising machine according to one or more of the preceding claims, characterised in that several groups of, in each case, three working chambers (5, 5', 5'') are fitted so as to act upon a common homogenising gap (15) or several gaps arranged in parallel, whereby the groups preferably have work cycles in relation to one another which are phase-offset by about 60°.
14. Method for operating a homogenising machine according to Claim 1, in which a liquid to be homogenised is conveyed through a gap (15), characterised in that the liquid to be homogenised is supplied to the gap (15) under pressure with an approximately constant volumetric flow rate by several membranes (4) operating in phase-offset manner.
15. Method according to Claim 14, characterised in that the pressure is maintained largely constant by means of a pressure reservoir (2) which is connected to a delivery line (23) between working chamber (5) and gap (15), whereby the pressure is applied by a hydraulic receiver via several membranes (4) operating in pulsating manner.
16. Method according to Claim 14 or 15, characterised in that several operating chambers deliver liquid jointly towards one gap (15).

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