EP3060352B1 - Method for clarifying a flowable product with a centrifuge - Google Patents

Description

The invention relates to a method according to the preamble of claim 1.

After US 5,318,500 To control the emptying parameters of a self-draining separator, a relatively complex mass balance determination is required, which requires, among other things, determining the inflowing mass and the solids concentration in the inflowing product.

After US 3,752,389 sensors are used to monitor whether a heavy phase has reached a certain level in a separator drum and an emptying control is then carried out depending on this measurement.

As far as the technological background is concerned EP 0 431 426 A1 called.

From the DE 32 28 074 A1 a method is known which advantageously enables control of a continuously emptying clarifier with a drum. A product parameter - here the degree of turbidity of a clear phase running out of the drum - is determined and used to monitor the emptying of the solids space of the drum. The solid phase is emptied continuously. If the turbidity or the degree of turbidity becomes too high in the clear phase, the clear phase is returned to the drum.

In addition, it is also known to use a clarifier for clarifying liquids, in particular beverages, in which the solids are emptied discontinuously with the aid of a piston valve to open and close discharge openings if the degree of turbidity measured with the photocell exceeds a certain limit.

This method has also proven itself, for example in the clarification of drinks containing turbid substances. It is problematic, however, that limit values must be specified when measuring the degree of turbidity of the clear phase, reaching them often means that an undesirably high proportion of turbid substances is already present in the beverage when the solids are emptied. Because a just beginning turbidity of the clear phase can only be determined with difficulty by sensors.

The object of the invention is to reduce this problem.

The invention solves this problem by a method having the features of claim 1.

When the drum starts up, the time of step a. the start time or the start of the product feed into the drum. Otherwise the time of the last emptying of solids is preferably used.

The calibration period can also be determined indirectly from the time the solids are emptied or as a period between two solids empties. The further solids emptying of step d. In this respect, only the consequence of the deviation of the product parameter from the target value and the time of this event is dependent. Falling below a limit value can in particular be done according to the measurement method of WO 2008/058340 A1 be a suitable method in which the turbidity is measured in a separate line to the outlet of the drum and / or in a bypass line or the like.

The actual value of the product parameter can be determined, for example, by a quasi-continuous determination of measured values. However, it is also possible to determine only a few measured values at slightly larger intervals. In this way, a measurement curve can be determined from the measured values, which allows a statement about the change in the product parameter.

The triggering of the second solids discharge preferably ends the calibration interval. The clear phase carried out in the calibration interval corresponds qualitatively to the clear phase according to the prior art, since a change in the parameter has already started in a significant manner. Therefore, during the calibration interval no qualitative change compared to the prior art has been achieved. However, this improvement is made possible by the fact that steps e) and f) can now be used to set different times than is possible solely on the basis of the measurements, which is explained in more detail below using examples.

Different mathematical operations can be used to determine and set the operating time interval. In this way, a preset time interval can be subtracted from the determined calibration time interval. The analysis curve or the end user can also analyze the measurement curve, that is to say the time course of the measurement values, over the calibration time interval, and the operating time interval can be set as a function of this evaluation. Last but not least, it is also possible to factorize the calibration interval, the factor which is multiplied by the calibration time interval preferably being less than 1. After running through the set operating interval, a solids discharge is triggered. This discharge of solids is thus time-controlled and not triggered as a function of a measurement.

In this way - assuming that the properties of the incoming product are largely the same - the solids can be emptied if the change is not yet measurable or only just measurable. If the product parameter is, for example, the turbidity content of a clear phase, once the calibration time interval is determined, an increase in the turbidity or the degree of turbidity in the clear phase is tolerated to a limit value. Some other emptying operations are then carried out in a time-controlled manner in such a way that this limit value is not reached in the first place and preferably even remains significantly below. In this way, the turbidity content of the overall derived clear phase is reduced and the overall quality of the derived clear phase is improved. Only after a few time-controlled emptying of solids is calibration carried out again to check whether the product properties of the incoming product to be processed have changed, so that an adjustment of the operating time interval is necessary. Because of the shorter operating time interval compared to the calibration time interval, the solids collecting space of the separator is therefore preferably emptied and the clear phase has almost constant product parameters over the course of the operating time interval - here in particular the degree of turbidity.

The aforementioned steps of the method serve to control the operation of a separator. However, the individual process steps do not necessarily have to be carried out in one unit of the separator, but can alternatively be carried out by external devices (measuring devices, sensors, evaluation unit).

Advantageous embodiments of the invention are the subject of the subclaims

It may be necessary to adjust the aforementioned operating interval from time to time to changes in the properties of the clear phase as a result of changes in the properties of the incoming product - in particular if this is a natural product such as a must to be clarified or a fruit or vegetable juice or a beer or the like . Such a change in properties can occur, for example, in the processing of turbid natural products that were previously stored in a container. A sediment is formed with larger amounts of turbid substances. If liquid is fed to the separator as a starting product from the sediment area, the solids content is higher and the solids have to be emptied more frequently. It is therefore advantageous if, after a predetermined number of runs of operating time intervals, steps a) -d) of claim 1 are run through again and the operating interval is adapted to a current measurement.

It is optionally also sensible if parameters of the starting product are included in the method according to the invention. Thus, the inlet volume flow or a product parameter of the starting product fed to the separator can be determined and steps a) - f) run through again if the volume flow changes or the product parameter changes beyond a limit value.

The product parameter of the clear phase can be not only the degree of turbidity but also another measurable parameter - the viscosity and / or the conductivity. Sensors or measuring devices with appropriately designed sensors for determining these parameters can be attached to the separator at the corresponding processes in a comparatively simple manner.

It is advantageous if the operating time interval is selected such that within the operating time interval the product parameters of the clear phase immediately before emptying deviates by less than 50%, preferably less than 20%, from the product parameters of the clear phase immediately after the solids discharge. If, for example, you select the degree of turbidity as a parameter, you have been able to do so - among other things Fig. 2 results - only a solids discharge or a solids emptying take place if the degree of turbidity of the clear phase towards the end of the time interval in which the solids collected in the separator had reached a multiple of the degree of turbidity of the clear phase immediately after emptying. This excessive increase in the degree of turbidity in the clear phase shortly before emptying is prevented by the novel setting of the operating interval.

Ideally, the operating time interval is at least 5%, preferably at least 10%, shorter than the calibration time interval.

The solids discharge takes place, as is customary in the case of a discontinuous solids discharge, preferably through discharge openings in the manner of nozzles, which can be closed and opened by a piston slide. This has the particular advantage that the opening state of the discharge nozzles can be precisely controlled.

The calibration time interval and the operating interval and the setting of the operating time interval are preferably determined by means of an evaluation unit designed as a software routine of a control computer, which is connected to the sensors and which enables the actuation mechanism of the piston slide in the drum to be activated.

Also advantageous is a method for clarifying a flowable starting product (AP) with a centrifuge, in particular a separator with a rotatable drum with an inlet and at least one liquid discharge for the continuous discharge of at least one clarified liquid phase - a clear phase - and with discontinuously opening solid discharge openings for discontinuous Discharge of the solid phase, which has at least the following steps: a) setting or determining a start time; b) repeated determination / measurement of at least one actual value of a product parameter of the clear phase (KP) derived from the drum; c) determining and evaluating the difference quotient from the determined product parameters and the respective time intervals between the measurements; and d) triggering a solids discharge as a result of the evaluation in step c). After step d), steps a) to d) preferably start again. The difference quotient is then determined and evaluated from the measured values of the product parameter and the time intervals between the measurements. Depending on this evaluation, emptying may be triggered. Only when the behavior of this difference quotient (i.e. the course of the numerical differentiation of the product parameter function, which is only approximately known in the form of discrete measured values, depending on the time) deviates from a predetermined and pre-stored behavior, in particular if the difference quotient (or the first derivative), for example The emptying is triggered once or several times, or falls below or exceeds a predetermined limit value.

According to claim 1, steps e) and f) are then carried out, i.e. one or a few further emptying intervals are fixed in time.

This procedure is considered in more detail using the example of the product parameter "degree of turbidity" as a function of time. The degree of turbidity is determined at intervals by a measurement. The difference quotients from the degree of turbidity and the time intervals between the respective measurements are then determined and evaluated. A (numerical) detection of a change, for example an increase, in the difference quotient enables a statement to be made, or advantageously a detection, at a relatively early point in time an onset of a clearer or faster increase in turbidity. In this situation, an additional emptying of solids makes sense. This procedure can also be used to prevent the risk of late emptying.

It may also be the case that when evaluating the difference quotient it is found that it changes only very slightly over a relatively long period of time. This can have the following cause. If the solids content in the separator drum increases very slowly, there is a risk that the plate pack in the separator drum will gradually become clogged with solids. This is the reason for proven continuous increase in the turbidity or the degree of turbidity ("sawtooth effect") and the dynamic limit value over the course of a day. In this case, it is conceivable that more solids are already being discharged, although the solids content itself is not yet as high as it should be when emptying. It therefore makes sense to carry out an emptying earlier than expected. In this situation it appears advantageous to define the limit value from the behavior of the derivation of the turbidity function as a function of time. Because evaluating the derivative function makes it possible to distinguish the very slow increase from other increases.

Other effects which can influence the course of the increase in the solids content in the separator drum are a possibly necessary throttling of the feed quantity, a possibly necessary rinsing of the hood or a pre-filling of a hydrostop system. In these situations too many solids could get into the liquid drain for the liquid phase. In this situation too, the alternative procedure provides a simple remedy. Because evaluating the derivation function makes it possible to record the situations described.

Optionally, it is also conceivable to carry out a new measurement in the event of a decrease in the turbidity or in the case of a constant turbidity and to discard the previously stored values. This way, inadmissible Drains are prevented, which could otherwise occur, for example, in the event of pressure surge changes or flow changes in the system

• Fig. 1: schematische Schnittansicht eines Separators, welcher mit dem erfindungsgemäßen Verfahren betrieben wird;
• Fig. 2: eine beispielhafte Messverlaufskurve aus einer Anwendung des erfindungsgemäßen Verfahrens;
• Fig. 3: ein Flussdiagramm zu einem erfindungsgemäßen Verfahren mit den Schritten des Anspruchs 1;
• Fig. 4: eine beispielhafte Messverlaufskurve aus einer Anwendung eines weiteren erfindungsgemäßen Verfahrens; und
• Fig. 5: ein Flussdiagramm zu einem alternativen Verfahren.

The invention is explained in more detail below on the basis of a preferred exemplary embodiment with reference to the accompanying drawings. It shows:

• Fig. 1 : schematic sectional view of a separator, which is operated with the inventive method;
• Fig. 2 : an exemplary measurement curve from an application of the method according to the invention;
• Fig. 3 : a flowchart for a method according to the invention with the steps of claim 1;
• Fig. 4 : an exemplary measurement curve from an application of a further method according to the invention; and
• Fig. 5 : a flowchart of an alternative method.

Fig. 1 shows a separator 1 for clarifying turbidity-containing, flowable starting products AP with a drum with a vertical axis of rotation. The product is processed in continuous operation. This means that the product is fed in continuously and at least one cleared liquid phase, called the clear phase, is drained off.

The separator has a discontinuous discharge of solids, the solid F separated from a starting product by clarification being removed at intervals by opening and reclosing discharge nozzles or discharge openings 5.

The drum has a lower drum part 10 and a drum cover 11. It is also preferably surrounded by a hood 12. The drum is also on a drive spindle 2 is placed, which is rotatably mounted and can be driven by a motor.

The drum has a product inlet 4, through which a starting product AP is passed into the drum. It also has at least one outlet 13 with a gripper, which is used to derive a clear phase KP from the drum. The gripper is a kind of centripetal pump. The liquid discharge could also be done by other means. In addition to clarification, it would also be conceivable to separate the product into two liquid phases of different densities. This would require a further liquid drain.

The rotatable drum with a vertical axis of rotation preferably has a plate pack 14 made of axially spaced separating plates. A solid collecting space 8 is formed between the outer periphery of the plate pack 14 and the inner periphery of the drum in the region of its largest inner diameter. Solids, which are separated from the clear phase in the area of the plate pack 14, collect in the solids collecting space 8, from which the solids can be discharged from the drum via the discharge nozzles 5. The discharge nozzles 5 can be opened and closed by means of a piston slide 6, which is arranged in the lower drum part 11. When the discharge nozzles are open, the solid F is passed out of the drum into a solid trap 7.

The drum has an actuating mechanism for moving the piston valve. Here it comprises at least one supply line 15 for a control fluid such as water and a valve arrangement 16 in the drum and further elements outside the drum. Thus, the supply of the control fluid such as water is made possible via a control valve 17 arranged outside the drum, which is arranged in a supply line 19 for the control fluid arranged outside the drum, so that the control fluid can be sprayed into the drum for emptying by releasing the control valve or conversely, the inflow of control fluid can be stopped to move the spool accordingly to expose the discharge openings. The actuation mechanism - here that Control valve 17 is connected via a data line 18 to a control unit 9 for controlling and / or regulating the solids discharge.

At least one sensor 22, which is designed to determine one or more product parameters of the at least one clear phase, is arranged on or in the process 13 of the clear phase. Product parameters in the context of the present invention are, in particular, physical properties of the measurement medium “clear phase” such as the degree of turbidity, the viscosity or also the conductivity (for example in the case of salt solutions). The at least one sensor 22 can be designed as a photocell for determining the light transmittance.

A sensor 3 for determining the flow rate or one or more product parameters of the starting product to be conducted into the drum is preferably also arranged on or in the inlet 4 for the starting product AP into the drum. These product parameters can also be physical parameters such as the turbidity or the viscosity of the starting product.

Such measurement methods can also be carried out using sensors as transmission measurements or scattered light measurements. Another option for determining the degree of turbidity is ultrasound measurements.

In contrast, process parameters such as volume flow or flow rate are also known. In a preferred embodiment variant, the sensor can in each case be integrated into a measuring device which has a product parameter e.g. determines the degree of turbidity or conductivity and at the same time a process parameter - such as determines the flow rate of the clear phase.

As already mentioned, in a particularly preferred variant, a turbidity measurement and / or a viscosity measurement of the starting product AP can be carried out on the product inlet 4 analogously to the determination of the product parameters of the clear phase KP.

The sensors 3 and 22 are connected via data lines 20, 21 to the evaluation and control unit 9 (preferably a control computer of the separator), which evaluates the measured values determined and controls the movement of the piston slide 6 and thus also the time interval until the discharge nozzles 5 open .

It goes without saying that the aforementioned data lines 18, 20, 21 enable data transmission from or to the evaluation unit 9, and can also be replaced by wireless connections.

The method according to the invention, which is carried out by means of the separator described above, is explained in more detail below, the degree of turbidity being selected as the product parameter in the present exemplary embodiment.

The starting product AP is preferably fed continuously into the separator, where it is clarified. There is a continuous clear phase discharge of the clear phase KP.

During the clarification of the starting product AP with the formation of the clear phase KP, turbid substances and other solids contained in the starting product are collected in the solid collecting space 6 of the separator which fills up. If too many of the solids have accumulated in the collecting space 6, their discharge begins with the clear phase ( Fig. 2 ) what should be avoided if possible.

In order to monitor the clarification, the measurement and determination of the degree of turbidity was previously carried out by a measuring cell. In this case, a limit value for the turbidity value which should not be exceeded was preset and the solids F were emptied out of the solids collecting space 6 when the determined turbidity value exceeded the limit value.

According to an embodiment variant of the method according to the invention, the time interval from the last emptying of the solid space 6 of the separator 1 to the reaching of a predetermined first turbidity limit value is first determined, as has been the case up to now. This process step is as follows referred to as determining a calibration time interval. The calibration time interval is defined as the time between the last time the solid space of the separator was emptied until the first turbidity limit value was reached. As soon as the measured turbidity content has reached the first limit value, the solid space 6 is emptied. The emptying of the solid space during this process step is controlled by the measurement and the reaching of the desired value.

After the calibration time interval has been determined, an operating time interval is set. The operating time interval can be determined by subtracting a predetermined time interval from the calibration time interval. After passing through the specific operating time interval, the solids are emptied in a time-controlled manner. This virtually precedes an increase in the degree of turbidity and ensures that the quality of the clear phase is almost consistently good. A measurement of the turbidity content during this process step is not absolutely necessary, but is conceivable in order to intervene if the limit value is reached prematurely contrary to expectations.

After repeated e.g. n times successive runs of the operating time interval, each with subsequent emptying of the solid space 6, the degree of turbidity of the clear phase may increase again. Here, n can preferably vary between 5-50, particularly preferably between 8-30, runs. It is therefore recommended that the calibration time interval be determined again and the operating time interval set again after running the operating time intervals n times.

The corresponding evaluation operations of the measurement signals and the control and / or regulation of the emptying process is ensured by the evaluation unit 9.

Since the degree of turbidity of the clear phase also depends, among other things, on the degree of turbidity of the starting product, it is advisable to monitor the conditions at the inlet of the starting product. The flow current can be detected in this way. However, it is also conceivable to have a measuring cell at inlet 4 for measurement of the feed flow. If this changes, a new determination of the calibration time interval can be triggered.

Fig. 2 represents the time course of the degree of turbidity T of the clear phase, provided the previous method is used.

The turbidity or the degree of turbidity T is constant at one percent over the course of the 1st minute to the 9th minute. From the 9th minute, the degree of turbidity increases relatively quickly. In the 11th minute the setpoint of 5% turbidity is reached and the solids are emptied. As a result, the degree of turbidity drops again to 1%. The time window t (K) represents the calibration time interval.

The time interval can be set manually or determined mathematically or depending on measured values in a database. For example, the operating time interval t (b) can be determined by multiplying the calibration time interval by a factor less than 1.

The time window t (B) represents the operating time interval. It can be seen that the turbidity in this time window is approximately constant at 1%.

The sequence of steps a) to f) of claim 1 additionally illustrates Fig. 3 . After step f), the method can start again at step a) and run through it again.

aus den Messwerten des Trübungsgrads $$\mathrm{\Delta }\mathrm{T}:=\mathrm{T}1-\mathrm{T}2$$

und den Zeitintervallen $$\mathrm{\Delta }\mathrm{t}:=\mathrm{t}2-\mathrm{t}1$$

zwischen den jeweiligen Messungen T2(t2) und T1(t1) bestimmt und ausgewertet.An exemplary procedure shows Fig. 4 using the example of the product parameter "degree of turbidity" as a function of time. The degree of turbidity T is determined by measurements in time intervals. Then the difference quotients $$\mathrm{\Delta }\mathrm{T}/\mathrm{\Delta t}$$

from the measured values of the degree of turbidity $$\mathrm{\Delta }\mathrm{T}:=\mathrm{T}1-\mathrm{T}\mathrm{2nd}$$

and the time intervals $$\mathrm{\Delta }\mathrm{t}:=\mathrm{t}\mathrm{2nd}-\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="imgf0001.png"\; state="\{\{state\}\}">t</figure-callout>}1$$

determined and evaluated between the respective measurements T2 (t2) and T1 (t1).

The detection of a change, for example an increase, in the difference quotient makes it possible to detect an onset of a faster increase in the turbidity at a relatively early point in time. In this situation, an additional emptying of solids makes sense. This procedure can also be used to prevent the risk of late emptying.

Reference symbol list:

1

separator

2nd

spindle

3rd

sensor

4th

Intake

5

Discharge openings

6

Spool

7

Solids trap

8th

Solids collection room

9

Evaluation unit

10th

Lower part of the drum

11

Drum cover

12th

Hood

13

procedure

14

Plate pack

15

Line for hydraulic fluid

16

Valve

17th

Control valve

18th

Data line

19th

Hydraulic line

20th

Data line

21

Data line

22

sensor

KP

Clear phase

AP

Starting product

F

Solids

t (K)

Calibration time interval

t (B)

Operating time interval

t (Z)

preset time interval

n

Number of successive runs of the operating time interval with subsequent solids discharge

Claims (10)

1. A method for clarifying a flowable starting product (AP) with a centrifuge, in particular a separator with a rotatable drum with a feed and at least one liquid discharge for continuously discharging at least one clarified liquid phase - a clear phase - and with discontinuously openable solid-discharge openings for continuously discharging the solid phase, characterized by the following steps:

   a. setting or determining a starting time;

   b. repeatedly determining at least one actual value of a product parameter of the clear phase (KP) drawn off from the drum; wherein the product parameter of the clear phase (KP) is the degree of turbidity, the viscosity and/or the conductivity;

   c. determining the calibrating time interval t(K) from the starting point until the time at which the product-parameter actual value or a difference quotient of the determined product-parameter actual values and the respective time intervals between the measurements reaches or exceeds a limit value, in particular a product-parameter limit value;

   d. initiating a solid discharge as a consequence of reaching or exceeding the limit value, in particular the product-parameter limit value;

   e. ascertaining and setting an operating time interval t(B) by means of the ascertained calibrating time interval t(K), the operating time interval t(B) being at least 5% less than the ascertained calibrating time interval t(K); and

   f. initiating at least one or more solid discharges each time the set operating time interval t(B) has elapsed.
2. The method as claimed in claim 1, characterized in that in step a. the time of a first solid discharge is ascertained.
3. The method as claimed in claim 1 or 2, characterized in that, after a predetermined number (n) of passages of operating time intervals t(B), a renewed run-through of steps a.- f. takes place.
4. The method as claimed in claim 1, 2 or 3, characterized in that an ascertainment of the volumetric flow or a product parameter of the starting product (AP) fed to the separator (1) is performed and a renewed run-through of steps a.-f. takes place if the volumetric flow changes or the product parameter changes up to a limit value or beyond a limit value.
5. The method as claimed in one of the preceding claims, characterized in that the setting of the operating time interval t(B) is performed in such a way that, within the operating time interval t(B), the product parameter directly before the evacuation deviates by less than 50%, preferably less than 20%, from the product parameter directly after the solid discharge.
6. The method as claimed in one of the preceding claims, characterized in that the operating time interval t(B) is at least 10% less than the calibrating time interval.
7. The method as claimed in one of the preceding claims, characterized in that the solid discharge takes place through discharge nozzles (5), the discharge nozzles (5) being closed and opened by a piston slide valve (6).
8. The method as claimed in one of the preceding claims, characterized in that the ascertainment of the product parameter of the clear phase (KP) is performed by a sensor (22), which is arranged in or at an outlet (13) of the separator (1).
9. The method as claimed in one of the preceding claims, characterized in that the ascertainment of the product parameter of the starting product (AP) is performed by a sensor (3), which is arranged in or at the feed (4) of the separator (1).
10. The method as claimed in one of the preceding claims, characterized in that the ascertainment of the calibrating time interval t(K) and the operating interval t(B) and the setting of the operating time interval t(B) are performed by means of an evaluation unit (9), which is connected to the sensors (3, 22) and which allows a hydraulic setting of the position of the piston slide valve (6) in the drum.

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