EP2025392B1 - Control for a cavitator assembly - Google Patents

Description

I. Field of application

The invention relates to a hydrodynamic cavitation mixer.

II. Technical background

As is known, with such mixers, a suspension or emulsion is produced with little effort and without mechanically driven parts, by initially generating vapor-filled gas bubbles in the liquid flowing along, which subsequently collapse again in an implosion-like manner.

When this collapse of a large number of bubbles, the so-called cavitation bubbles, occurs near the interface between two phase areas, say large gas bubbles in water, the second component, in this case the gas bubbles, is torn into smaller units and thereby a very fine mixing of the two components and thus produces a very stable gas-water mixture.

The generation of cavitation bubbles is done in a flowing liquid by a drop in the static pressure below the vapor pressure of the liquid, thereby forming vapor-filled gas bubbles, eg. B. due to a current narrowing.

When the static pressure then increases again due to a widening of the flow cross-section and the static pressure again exceeds the vapor pressure, the gas bubbles collapse.

The constriction and subsequent expansion of the flow cross section can be achieved by an obstacle body is arranged in a flow chamber, wherein the remaining gap z. B. between obstacle body and surrounding housing of the flow chamber forms the bottleneck.

By multiple arrangement of such obstacle bodies behind each other, for reasons of space preferably in the form of transverse to the flow direction discs, the cavitation effect is multiplied, special in the flow direction, the annular gap area decreases from one disc to the next respectively.

In addition, cavitation fields forming in the cavities field form in the cavities between the obstacle bodies, and the spatial superposition of the individual cavitation fields creates a so-called super-cavitation field, which causes a multiplication of the cavitation effect of each individual cavitation field.

The static pressure, which falls short of the cavitation effect, becomes zero or negative in the case of water if the flow velocity exceeds a certain value dependent on environmental conditions, for example about 14 m / s at the trailing edges of the obstacle bodies.

Cavitators of this kind are used, for example, in mineral water bottling plants or lemonade production, in order either to bind the added CO ₂ as completely as possible in the water, and / or also to add the soda-based raw material (syrup).

There are two main problems in practice:

On the one hand, the quantity of the product delivered per unit time and to be processed, that is to say above all the main components of the beverage, can change greatly, depending on the operating state of the upstream plant parts or else the availability.

Furthermore, z. B. by changing the product whose properties change, for example, its temperature, viscosity, delivery pressure, etc ..

In order nevertheless to reliably effect the cavitation effect in the cavitator under such changing conditions, a certain minimum flow velocity, in particular in the flow gaps in the obstacle bodies, must be reached or exceeded, which, however, depends on the stated environmental conditions.

From the WO02 / 38512 A1 For example, a method of treating wastewater using cavitation is known. In a main section of the Cavitators several pressure relief valves are arranged, which are connected to discharges and thus prevent an overpressure builds up in the line. If an excessively high pressure occurs upstream or downstream of the cavitator, one of the overpressure valves opens and diverts a portion of the fluid located in the main line into a water reservoir.

III. Presentation of the invention a) Technical task

It is therefore an object of the present invention to provide a method and a device with the aid of which a cavitator or a cavitator system, which may also comprise a plurality of cavitators, is adapted to a change in operating conditions, in particular varying flow rates and product parameters , in particular automatically adjusted.

b) Solution of the task

This object is solved by the features of claim 1. Advantageous embodiments will be apparent from the dependent claims.

Since the detectable between the inlet and the outlet of Cavitators pressure drop with the flow velocity in Cavitator and in particular with the flow velocity at the obstacle bodies, ie in the bottlenecks of the Cavitators, correlated, the Cavitator can be controlled due to the pressure drop measured at the Cavitator distance become. The Cavitator distance can consist of one or more, in this case then usually connected in parallel, Cavitatoren.

First, a minimum pressure drop must be set which must occur at the cavitator path so that cavitation and thus the desired effect of mixing occur within the cavitator.

How high this minimum pressure drop must be depends on a variety of boundary conditions, on the one hand on the design and size of the cavitator, but also on environmental conditions such as the physical properties of the fluid to be treated with the cavitator or at least its main component in the case of mixtures z. As the temperature, viscosity and the pressure at which the fluid to be processed is delivered.

Now, if the pressure drop during operation falls below the predetermined minimum pressure drop, a partial stream is diverted from the main stream at the exit of the Cavitator route and returned in a circle to the main line before the start of the Cavitator route and fed back to it, whereby the Cavitator- Route supplied amount per unit time is artificially increased to ensure the occurrence of cavitation.

In detail, the necessary control can be executed differently:

Thus, for example, falls below the minimum pressure drop always a fixed, certain proportion of the main stream are recycled in a circle, for example, always 50% of the main stream.

It is better, however, to be able to vary the recirculated partial flow in terms of its size, for example stepwise or continuously, which is easy to implement by a built-in the return line control valve. As a result, it can be achieved that the occurring pressure drop is always just above the predetermined minimum pressure drop and thus cavitation occurs.

A significant increase in the pressure drop over this minimum value brings little effective benefit, since the cavitation occurring then quantitatively hardly larger, so the mixing is hardly improved. In contrast, other problems occur with the return of a considerable or even large part of the main flow:

The multiple treatment in the Cavitator increases the temperature of the medium to be treated, which is disadvantageous for many applications. Likewise, the fluid to be treated is thereby not only subjected to simple but multiple loads occurring in the cavitator, for example, high shear forces, which may be disadvantageous depending on the fluid to be treated.

A particularly simple way to gradually increase the proportion of the recirculated partial flow, is to split the line into several parallel arms and install in each of these arms a simple shut-off valve, which are much cheaper and easier to control than a control valve.

By blocking several or fewer of these check valves and thus the partial branches of the return line of the recycled portion of the main flow can be varied.

The return of the partial flow takes place to a point before the working pressure for the Cavitator making available pump, so that the returned partial flow by means of this pump in turn brought to the desired working pressure becomes.

If the cavitator is used as a mixer, the return is also to a point before the mixing point of the components supplied in the main component.

Usually, the pressure drop is measured continuously and the results of the pressure measurement fed to a controller that regulates the flow through the return line. A particularly simple control that offers this is a simple differential pressure controller. In general, however, a more complex control is used, which can also take over other control functions.

Thus, for example, in addition to the pressure drop occurring directly the physical properties of the product, such as temperature, viscosity, etc. are measured and also the pressure, preferably the pressure after the pump, so the working pressure at the entrance to the Cavitator. Since the pressure drop is determined anyway by determining the pressures in front of and behind the cavitator, one of these individual pressures is already the pressure at the entrance to the cavitator.

If the cavitator path comprises not just one but several cavitators connected in parallel, the adjustment to too low a flow can also be achieved by - at least once a minimum pressure drop across the cavitator path has previously been established Cavitator or sequentially disabled several cavitators, so be closed until the minimum pressure drop is reached over the Cavitator distance with the remaining in-use cavitators, so at least one in-service cavitator.

If the Cavitator route includes two or more equally sized cavitators, falls below the minimum pressure drop one by one of these Cavitatoren sequentially shut down until only one Cavitator operated becomes.

On the other hand, if the cavitators of a cavitator path are dimensioned differently, the procedure is different:

If the initial state was that all Cavitatoren the route were activated and then the pressure drop below the minimum pressure drop decreases, so first the smallest Cavitator is stopped.

If this is not enough, the smallest cavitator will be activated and instead the next larger cavitator will be deactivated and so on until the minimum pressure drop is reached.

Should this not be achievable with the shutdown of a single Cavitators, the largest single Cavitator is left disabled and continued with the remaining activated Cavitatoren the same run and so on until the end of two or more Cavitatoren are stopped. In this way, the minimum pressure drop is just exceeded without too much increase, which means only high energy losses.

In this way, for example, with three different size cavitators already a very good control of the Cavitator system can be performed.

Preferably, the individual, each next larger Cavitatoren always behave to each other in the same size ratio, for example, 1: 2 or 1: 4.

If an operation with one or more disused Cavitatoren takes place, after a predetermined period - if this is possible due to the same dimensioning of Cavitatoren - the disused Cavitator changed to avoid too long standing of the medium to be processed in disused Cavitator, which there Possibility for undesirable germination would increase.

Conversely, in a cavitator path where not all cavitators are currently in operation, additional cavitators are activated when the instantaneous pressure drop is greater than 30%, and more than 50%, above the predetermined minimum pressure drop. This avoids excessive energy loss and excessive shear stress on the medium.

To shut down a Cavitators both the supply line and in particular the discharge line, ie in front of and behind the Cavitator, locked separately.

This prevents the migration of microbial contamination into and out of the cavitator, as well as pressure surges from the activated area of the cavitator route into the decommissioned cavitator.

Further, if the cavitator or cavitators of a cavitator track is variable with respect to the gap size, ie, the size of the effective gap between obstruction bodies and cavitator outer housing, cavitational cavitation may be controlled and adjusted by changing the gap size as well ,

In general, the obstacle bodies are arranged axially one behind the other at a distance, disk-shaped bodies which are arranged on an axially extending rod. To adjust the gap size not every single obstacle body is usually moved in its axial position within the usually tapered outer housing, but the axial rod and with him all obstacle body, so the entire obstacle tree.

A particularly simple control is possible because the Obstisbäumchen can only be adjusted back and forth between two end positions, which can be done in a simple manner by means of a compressed-air cylinder.

A finer control option is given if the axial adjustment can be done in several stages or even continuously, for which the tree must be moved, for example by means of a servo motor.

In particular, the continuous adjustment of the gap size is then carried out in direct dependence on the currently measured pressure drop over the Cavitator distance, so that the required minimum pressure drop is just reached.

In a cavitator, the gap width can only be varied between two positions, is switched with set large gap width to the smaller gap width as soon as the minimum pressure drop is exceeded. Conversely, switching from smaller to larger gap width is made as soon as the minimum pressure drop is exceeded by more than 20%.

The minimum pressure drop is set so that, for example, in water as the product to be processed, or a product whose main component is water, at a processing temperature of 20 ° C with deviations of +/- 2 ° C, a flow rate of at least 15 m per Second in Cavitator, especially at all bottlenecks in Cavitator, reached or exceeded. This corresponds to z. B. a minimum pressure drop of 4.0 bar above the Cavitator route.

A Cavitator system can now have several influencing options at the same time:

If the system on the one hand has a return line and on the other hand, the cavitators are variable with respect to the gap width, with a decrease in pressure drop below the minimum pressure drop, first several sequentially reduced to all Cavitatoren the Cavitator distance from a large gap to a small gap if only two positions of the gap width possible are.

If a stepped multiple variation is possible, the gap width is increasingly lowered, preferably parallel in all cavities of the distance until the minimum pressure drop is reached.

If the change in the gap width is insufficient for this purpose, in a second step, in addition, the return is increasingly open, until in this way by both influencing methods together the minimum pressure drop is reached.

If the available Cavitator system except return line and the adjustment of the gap width on a Cavitator distance with several parallel cavitators has that can be activated and deactivated individually, the switching off one or more successive Cavitatoren is the primary choice for influencing the Pressure drop, and only if this is not sufficient, in addition, the gap width reduction and the increase of the return portion - in this order - additionally used.

An alternative to this control priority is, as a first measure, to reduce the gap width for all cavitators of the cavitator path that are still continuous, and only if this is not sufficient to deactivate one or more cavitators. Again, the last level of influence is the increase in the proportion of recirculation through the return line.

The return flow through the line is never completely closed in practice to prevent deposits and microbial contamination in the line. A return of at least 2%, better 5% of the main stream is sufficient for this.

• Eine Cavitator-Strecke mit mehreren, parallel zueinander geschalteten Cavitatoren, die einzeln und unabhängig voneinander angesteuert werden können. Dabei können die Cavitatoren sowohl vollständig abgeschaltet werden, als auch im geöffneten Zustand ihre Spaltenbreite wenigstens zwischen einer großen und einer kleinen Spaltenbreite, vorzugsweise stufenlos, verstellt werden,
• eine Pumpe in der Zufuhrleitung zur Cavitator-Strecke, um den für die Funktion der Cavitatoren notwendigen Druck aufzubringen,
• eine Messvorrichtung, die den Differenzdruck zwischen zwei Messpunkten vor und nach der Cavitator-Strecke und damit den Druckabfall über der Cavitator-Strecke misst,
• und - falls der Cavitator als Mischer betrieben wird - eine Einspeiseleitung für die zuzuführende zweite Komponente der Mischung, wobei die Leitung in der Haupt-Strecke der Cavitator-Anlage vor der Pumpe mündet,
• eine Steuerung, die die Signale der Differenzdruckmessvorrichtung als Input verwendet und in Abhängigkeit davon sowohl die einzelnen Cavitatoren ansteuert, also schließt oder öffnet, und im geöffneten Zustand die Spaltenbreite variiert.

A cavitator system for implementing the influencing possibilities described above thus has the following elements:

• A Cavitator track with several cavitators connected in parallel, which can be individually and independently controlled. In this case, the cavitators can both be switched off completely, and in the opened state their column width can be adjusted, at least between one large and one small column width, preferably continuously,
• a pump in the supply line to the Cavitator distance, in order to apply the pressure necessary for the function of the Cavitatoren,
• a measuring device, which measures the differential pressure between two measuring points before and after the Cavitator distance and thus the pressure drop over the Cavitator distance,
• and - if the cavity is operated as a mixer - a feed line for the supplied second component of the mixture, wherein the line opens in the main path of the Cavitator system in front of the pump,
• a controller that uses the signals of the differential pressure measuring device as input and depending on both the individual cavitators controls, so closes or opens, and in the open state, the column width varies.

The gap widths within a cavitator on the individual obstacle bodies can usually only be adjusted together, for example, by axial displacement of the entire, conical from the outer circumference, obstacle trees into the conical housing of the Cavitators.

In addition, if the main line has a return line from one point behind the Cavitator track back to a point in front of the Cavitator track, in particular in front of the Cavitator track pump, whose throughput is using a control valve can be controlled, the proportion of the returned via the return partial flow from the controller can also be controlled depending on the pressure drop across the Cavitator distance.

For shutting off, ie deactivating, the individual cavitators in the cavitator path, each cavitator preferably has check valves both in front of and behind the cavitator to prevent kickbacks and contamination in and out of the disused cavity.

The measuring points, which measure the pressure difference over the Cavitator distance, are on the one hand between the end of the Cavitator distance and the branch for the return, thus still on the unbranched main distance behind the Cavitator and on the other hand between the pump and the Entry into the Cavitator track to capture the full initial working pressure towards the Cavitator track.

The control valve in the return line is preferably arranged near the end of the return line, ie the mouth point in the main line.

If a feed line for a second component is present, this is in terms of their mouth in the main strand between the mouth of the return line and the pump, but preferably has a cross-connection to the return line, which opens upstream of the control valve in the feed line.

c) embodiments

Fig. 1:

Eine erfindungsgemäße Cavitator-Anlage, und

Fig. 2:

einen dabei verwendeten Cavitator.

Embodiments according to the invention are described in more detail below by way of example. Show it:

Fig. 1:

A Cavitator plant according to the invention, and

Fig. 2:

a Cavitator used.

FIG. 1 shows a Cavitator plant, in which in the main flow direction 10, a fluid to be processed, usually water or a product whose main component is water, fed and passed through a Cavitator distance 1, consisting of one or more, in this case two equal cavitators 1a, b connected in parallel.

So that the desired cavitation effect occurs in the cavitators, the fluid to be processed is brought by a pump 4, which is arranged in front of the Cavitator distance 1 in the main strand to the required pressure, which depends on the physical properties of the fluid to be processed and others Parameter is.

In the present case, the Cavitator system is used as a mixer, which is why the flowing in the main flow direction 10 fluid via a feed line 17, a second component, in this case CO ₂ , is supplied.

The feed line opens in the main line in a mixing point 5, which opens upstream of the pump 4, so that the complete mixture of the pressure increase is supplied by the pump 4.

From the main flow direction 10, so the main strand, branches off after the Cavitator-line 1, a return line 3 at point 3a and performs a partial flow 2a of the main stream 2 in the circle back to the main line to a point 3b, the upstream of the pump 4 and also upstream of the mixing point 5 for the second component.

This recirculation, ie a circuit guide, serves only to supply the required minimum flow rate through the cavitator section 1 in the case of small amounts of fluid to be processed per unit time in the main flow direction necessary to achieve the minimum pressure drop across the cavitator path necessary for the function of the cavitators.

For this purpose, the pressure drop across the cavitator path is measured by a differential pressure measuring device 15, which passes on its results to a controller 6, which can also be functionally combined with the differential pressure measuring device.

This control 6 controls the arranged in the return line 3 control valve 7, which is a control valve and can control the flow through the return line 3 steplessly.

The pressure measuring points 16a, b are on the one hand between the pump 4 and the entrance to the Cavitator distance 1 and on the other hand between the Cavitator distance 1 and the junction point 3a of the return path 2a.

In addition, by means of flow meters 21a, b, the flow on the one hand in the main line 10 upstream of the point 3b, in which the return line 3 opens, and on the other hand measured in the feed line 17 and the controller 6 to improve the control behavior available.

The control valve 7 is preferably located near the mouth point 3b of the return line in the main line 10th

Furthermore, each of the parallel-connected cavitators 1a, b of the cavitator section 1 can be shut down separately, ie closed, by blocking valves 18a, b arranged in front of and behind the respective cavitator 1a.

These check valves 18a, b in each cavitator 1a, b ... are controlled by the controller 6, so that each individual cavitator can be activated and deactivated.

For this purpose, only a single check valve would be sufficient for each individual cavitator, but should be prevented by the two check valves that unilaterally mixed liquid and thus germs or pressure shocks from the main strand from acting on the immobilized Cavitator.

Further, in each cavitator 1a, b is the - in FIG. 2 shown obstacle trees 12 with the attached obstacle bodies 14a, b in the axial direction 10 of the Cavitators between two end positions by means of an air cylinder 13a displaceable, which due to the conical design of both the Obstisbäumchens and the surrounding Cavitatorgehäuses the gap width 11 from large to small gap width and vice versa can be adjusted.

Also, this adjustment causing air cylinder 13a, b are controlled by the controller 6 from.

The measuring points for the differential pressure measurement by the measuring device 15 are located downstream of the Cavitator-line 1 between the end of the Cavitator-1 route and the branch 3a for the return 3 and upstream of the Cavitator-track 1 between the pump 4 and the Cavitator-stretch 1.

Between the feed line 17 for the second component and the return line 3 there is also a connecting line 19, which branches off in the feed line 17 between the metering valve 20 and the mixing point 5 with the main strand.

This connecting line and the other valves contained in the feed line and connecting line 19 are used both in the feed line and in the return line for cleaning purposes.

Also, the metering valve 20 in the feed line 17, which controls the supply to the second component can advantageously be controlled directly by the existing controller 6.

• Einerseits das Zu- und Abschalten einzelner Cavitatoren 1a, b der Cavitator-Strecke 1,
• andererseits das zunehmende Öffnen oder Schließen der Rückführstrecke 3 und damit des vom Hauptstrom zurückgeführten Teilstromes 2a, und
• Vergrößern oder Verkleinern der Spaltbreite in den einzelnen Cavitatoren, in diesem Fall durch Umschalten von großer auf kleiner Spaltbreite und zurück separat und unabhängig für jeden einzelnen Cavitator 1a, b....

Thus, a controller 6 controls the three significant influencing possibilities for the pressure drop across the cavitator path, which for proper function and application of the cavitation effect should not fall below one for each individual case of the system-specific minimum pressure drop:

• On the one hand the switching on and off of individual cavitators 1a, b of the cavitator segment 1,
• on the other hand, the increasing opening or closing of the return path 3 and thus of the recirculated from the main flow part stream 2a, and
• Increase or decrease the gap width in the individual cavitators, in this case by switching from large to small gap width and back separately and independently for each cavitator 1a, b ....

LIST OF REFERENCE NUMBERS

1

Cavitator route

1a, b

Cavitator

2

main power

2a

partial flow

3

Return path

3a, b

Point

4

pump

5

mixing point

6

control

7

Control valve

8th

supply line

9

discharge

10

Flow direction

11

gap width

12

obstacle trees

13a, b

Air Cylinder

14a, b

obstacle body

15

Differential pressure measuring device

16a, b

measuring points

17

feeder

18a, b

check valves

19

connecting line

20

metering valve

21a, b

Flowmeter

Claims (7)

1. A method for flow control for a cavitator assembly including a cavitator path (1), including a cavitator (1 a) or plural cavitators (1 a, b... ) connected in parallel, wherein

   - a minimum pressure drop over the cavitator path (1) is determined as a function of properties of the fluid to be processed,

   - when undercutting the minimum pressure drop, a partial flow (2a) from an end of the cavitator path (1) is returned in the cycle through a return path (3) upstream of a beginning of the cavitator path (1), so that the volume supplied to the cavitator path (1) per unit time is increased in order to provide cavitation.
2. The method according to claim 1, wherein the portion of the returned partial flow (2a) is a fixated portion, in particular 50 % of a main flow (2).
3. The method according to claim 1, wherein the portion of the returned partial flow (2a) is continuously changed so that the minimum pressure drop is provided.
4. The method according to one of the preceding claims, wherein the return is provided at a point upstream of a pump (4) providing an operating pressure for the cavitator path.
5. The method according to one of the preceding claims, wherein the return is provided at a point upstream of a mixing point (5) of two components in a cavitator arrangement that is used as a mixer.
6. The method according to one of the preceding claims, wherein the minimum pressure drop is determined as a function of properties of the product to be processed, in particular at least as a function of properties of the main components of the product.
7. The method according to one of the preceding claims, wherein a minimum pressure drop over the cavitator path (1) is predetermined, in particular as a function of properties, e.g. a temperature, of the product to be processed.

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