DE102015119165B4 - Process for clarifying a free-flowing product using a centrifuge, in particular a separator - Google Patents

Abstract

Process for clarifying a flowable starting product (AP) with a centrifuge, in particular a separator with a rotatable drum (1) with an inlet (4) and at least one liquid outlet (13) for the continuous outlet of at least one clarified liquid phase - a clear phase - and with discontinuous solids outlet openings (5) to be opened for the discontinuous discharge of a solids phase - called solids emptying -, characterized by at least the following steps:100: Setting or determining a time interval, which is limited by a start time (t1) and an end time (t2), wherein in the time interval a next solids discharge is to take place after a previous solids discharge;200: carrying out a centrifugal clarification of the starting product (AP) in the drum (1);300: repeated determination of at least one actual value of a parameter, in particular a product or process parameter, during the step 200; 400: Carrying out a solids emptying if the parameter deviates from a limit value, in particular exceeds a limit value; and500, 900: determining the point in time (tE) of the current emptying of solids and checking whether this is within the time interval from step 100; and- return to step 200 if the time (tE) of the current solids emptying is in the time interval from step 100;- or carry out a change in a discharge volume for the next solids emptying if the time (tE) of the current solids emptying is not in the time interval the step 100 lies.

Description

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

From the U.S. 4,014,498A is a method for clarifying a free-flowing starting product with a separator with a rotatable drum with an inlet and at least one liquid outlet for the continuous outlet of at least one clarified liquid phase - a clear phase - and with solids outlet openings that can be opened discontinuously for the discontinuous outlet of a solids phase - called solids discharge - known, that has at least the following steps: 100: setting or determining a time interval, which is delimited by a start time and an end time, wherein a next solids emptying is to take place in the time interval after a previous solids emptying; 200: performing a centrifugal clarification of the starting product in the drum; 300: repeated determination of at least one actual value of a parameter, in particular a product or process parameter, during step 200; 400: Carrying out a solids emptying if the parameter deviates from a limit value, in particular exceeds a limit value; and 500, 900: determining the time of the current solids emptying and checking whether this is within the time interval from step 100; and returning to step 200 if the time of the current solids discharge is within the time interval of step 100; or performing a change in the product feed volume per unit of time if the point in time (tE) at which the solids are discharged is not in the time interval from step 100. Further state of the art form the U.S. 3,408,000 A , U.S. 2,532,792 A and DE 10 2013 111 576 A1 .

The clarification performance of a self-cleaning separator for clarification of solids from a product to be processed is determined, among other things, by parameters such as the clarification area of the disk pack, the size of the solids space in the drum, the design of the centripetal pump for discharging the clear phase, the drive power of the motor and the set inflow volume per Unit of time (inlet quantity) and the quantity of solids contained in the product are limited. With many self-cleaning separators, the solids discharge is triggered after a fixed time interval. The time between two emptyings (emptying frequency) depends on the above parameters. If more volume is emptied when emptying the solids than there is solids in the bowl, this usually leads to product loss.

In order to prevent this, modern centrifuges are not only emptied at intervals, but the solids are also emptied by a sensor device ( DE 32 28 074 A1 ) triggered, e.g. by measuring the turbidity of the clear phase flow or by comparable systems. Since the emptying volume is also set to be constant here, an increase in the solids content in the inlet (e.g. starting product from a tank bottom cone) can lead to a significant increase in the emptying frequency, which should be avoided.

Against this background, the object of the invention is to alternatively further develop the generic method in such a way that it enables very simple and very good control of the emptying and thus of the entire clarification method as a whole.

The invention solves this problem by the subject matter of claim 1.

Advantageous configurations of the method according to the invention can be found in the dependent claims.

• 100: Setzen oder Bestimmen eines Zeitintervalls, das durch einen Startzeitpunkt und einen Endzeitpunkt begrenzt ist und in dem eine nächste Feststoffentleerung nach einer vorhergehenden Feststoffentleerung erfolgen soll;
• 200: Durchführen eines zentrifugalen Klärens des Ausgangsproduktes in der Trommel;
• 300: wiederholtes Bestimmen wenigstens eines Istwertes eines Parameters, insbesondere eines Produkt- oder Verfahrensparameters, insbesondere eines Produktparameters der aus der Trommel abgeleiteten Klarphase, während des Schrittes 200;
• 400: Durchführen einer Feststoffentleerung, wenn der Parameter von einem Grenzwert abweicht, insbesondere einen Grenzwert überschreitet; und
• 500, 900: Bestimmen des Zeitpunkts (t_E) der aktuellen Feststoffentleerung und prüfen, ob dieser in dem Zeitintervall aus dem Schritt 100 liegt; und
  • - Rückkehr zu Schritt 200, wenn der Zeitpunkt t_E der aktuellen Feststoffentleerung in dem Zeitintervall aus Schritt 100 liegt;
  • - oder Durchführung einer Veränderung eines Entleerungsvolumens für die nächste Feststoffentleerung , wenn der Zeitpunkt t_E der aktuellen Feststoffentleerung nicht in dem Zeitintervall aus dem Schritt 100 liegt.

Claim 1 creates a method for clarifying a flowable starting product with a centrifuge, in particular a separator with a rotatable drum with an inlet and at least one liquid outlet for the continuous outlet of at least one clarified liquid phase - a clear phase - and with solids outlet openings that can be opened discontinuously for the discontinuous outlet of the solids phase - called solids discharge -, with at least the following steps:

• 100: Setting or determining a time interval, which is limited by a start time and an end time and in which a next solids discharge is to take place after a previous solids discharge;
• 200: performing a centrifugal clarification of the starting product in the drum;
• 300: repeated determination of at least one actual value of a parameter, in particular a product or process parameter, in particular a product parameter of the clear phase derived from the drum, during step 200;
• 400: Carrying out a solids emptying if the parameter deviates from a limit value, in particular exceeds a limit value; and
• 500, 900: determining the point in time (t _E ) of the current emptying of solids and checking whether this is within the time interval from step 100; and
  • - Return to step 200 if the time t _E of the current solids emptying is in the time interval from step 100;
  • - or carrying out a change in an emptying volume for the next emptying of solids if the point in time t _E of the current emptying of solids is not in the time interval from step 100.

The following is preferably also defined and/or set in step 100: a maximum limit value for the parameter that is not to be exceeded; and the volume of solid to be dumped in the next solid dump to a value less than a maximum value and greater than a minimum value.

In practice, it has proven to be useful and advantageous for a safe and stable process if the time interval is within the following range: 0 sec ≤ t ₂ - t ₁ ≤ 300 sec. This means that the starting point and the end time can be the same on the one hand so that the time interval is zero or, on the other hand, the time interval within which the emptying is to follow can be up to 5 minutes long before parameters are adjusted in order to arrive as closely as possible within the time interval at the next emptying. In the first case, the parameters are almost always adjusted after each emptying. The longer the interval, on the other hand, the less frequently adjustments to the parameters are necessary.

If it is determined in step 500 that the last solids emptying E of step 400 was triggered before the start time t ₁ of the time interval was reached, the emptying volume V _E for the next solids emptying is increased in a step 700. If it is determined after a long period of operation that the specified time interval has not been optimally selected, this can also be changed—for example manually by an input or automatically by a calculation—and the method can be restarted, as it were.

Furthermore, if it is determined in step 900 that the last solids emptying E of step 400 was triggered after reaching the end time t ₂ of the time interval, the emptying volume V _E for the next solids emptying is reduced in a step 1100

With the subject matter of claim 1 and the subject matter of the subclaims it is ensured in a simple manner in each case that the solids discharge is carried out in a well-controlled manner even if the solids content in the inlet of the centrifuge fluctuates greatly.

The deviation from a parameter limit value can also be a deviation from a derivative limit value (limit value for a gradient) when determining a temporal behavior of the parameter. In addition, one or more parameters can be determined. If necessary, emptying is triggered when one of the parameters first exceeds a set limit value (e.g. degree of turbidity and viscosity).

Preferably, the emptying frequency, the emptying volume and the inflow quantity of inflowing product per unit of time are adjusted in a simple manner such that the required quality properties (e.g. selectivity and dry substance) of the centrifugal separation are maintained in a reproducible manner.

• 1: schematische Schnittansicht eines Separators, welcher mit dem erfindungsgemäßen Verfahren betrieben wird;
• 2: ein beispielhaftes Diagramm zur Veranschaulichung des erfindungsgemäßen Verfahrens;
• 3: ein Flussdiagramm eines Ausführungsbeispiels eines erfindungsgemäßen Verfahrens.

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

• 1 : schematic sectional view of a separator which is operated with the method according to the invention;
• 2 : an exemplary diagram to illustrate the method according to the invention;
• 3 : a flowchart of an embodiment of a method according to the invention.

1 shows a separator for clarifying turbidity-containing, free-flowing starting products AP with a rotatable drum 1 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 clarified liquid phase, known as the clear phase, is also discharged continuously. The drum 1 of the separator, configured as a self-emptying centrifuge, has a discontinuous solids outlet, the solids F separated from the starting product AP by clarification being removed at intervals by opening and closing again outlet nozzles or outlet openings 5 .

The drum 1 has a lower drum part 10 and a drum cover 11 . It is also preferably surrounded by a hood 12 . The drum 1 is also placed on a drive spindle 2, which is rotatably mounted and can be driven by a motor.

The drum 1 has a product inlet 4 through which a starting product AP is fed into the drum 1 . It also has at least one outlet 13 with a gripper, which is used to drain a clear phase KP from drum 1 serves. The gripper is a type of centripetal pump. However, the liquid outlet could also take place by other means. In addition, it would also be conceivable to carry out a separation of the product into two liquid phases of different densities in addition to the clarification. This would require a further liquid drain.

The drum 1 preferably has a plate pack 14 of axially spaced separating plates. A solids collection space 8 is formed between the outer circumference of the disk pack 14 and the inner circumference of the drum 1 in the region of its largest inner diameter. Solids, which are separated from the clear phase in the area of the plate stack 14, collect in the solids collection chamber 8, from which the solids can be discharged from the drum 1 via the outlet nozzles 5. The outlet nozzles 5 can be opened and closed by means of a piston valve 6 which is arranged in the lower part 10 of the drum. When the outlet nozzles are open, the solids F are conveyed out of the drum 1 into a solids catcher 7 .

The drum 1 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 1 and other elements outside the drum. The inflow of the control fluid such as water is made possible via a dosing arrangement 17 arranged outside of the drum 1, which is assigned to an inflow line 19 for the control fluid arranged outside of the drum 1, so that the control fluid can be sprayed into the drum 1 for emptying the solids by releasing the control valve or vice versa, the flow of control fluid can be interrupted in order to move the piston valve accordingly in order to release the outlet openings.

At least one sensor device 22 is arranged on or in the outlet 13 of the clear phase KP, which is designed to determine one or more parameters of the at least one clear phase KP. Parameters in the context of the present invention are in particular physical properties of the measuring medium "clear phase" KP such as the degree of turbidity, the viscosity or the conductivity (eg in the case of salt solutions). The at least one sensor device 22 can be embodied, for example, as a photocell for determining the light transmittance for determining the degree of turbidity TR. In a configuration in which the clarified clear liquid phase is additionally separated into two liquid phases of different densities, the degree of turbidity can be measured in one or both of the two liquid phases. The degree of turbidity is defined, for example, on the basis of a maximum permissible value: TR _M := 100%.

A sensor device 3 for determining the flow rate or one or more parameters of the starting product to be fed into the drum 1 can - but does not have to - also be arranged at or in the feed 4 for the starting product AP into the drum 1 . These parameters can also be physical parameters such as the degree of turbidity or the viscosity of the starting product.

Such determinations can be carried out, for example, using suitable sensors as transmission measurements or scattered light measurements. Another way of determining the degree of turbidity are ultrasonic measurements. In contrast, process parameters such as volume flow, mass flow or flow rate are known and can be measured.

In a preferred embodiment variant, the sensor device can be integrated into a measuring device, which determines a clear phase or starting product parameter - e.g. the degree of turbidity TR or the conductivity - and at the same time a process parameter - e.g. the volume per unit time of the clear phase - determines.

As already mentioned, analogous to the determination of one or more product parameters of the clear phase KP, in a particularly preferred variant, one or more product parameter(s) can be determined - for example by means of a turbidity measurement and/or a viscosity measurement of the starting product AP at the product feed 4 - .

The sensors 3 and 22 are connected via data connections 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 valve 6 and thus also the time interval until the outlet nozzles 5 open .

The actuating mechanism for the piston valve 6—here in particular the dosing arrangement 17—is connected via a data link 18 to a control unit 9 for controlling and/or regulating the solids outlet. The dosing arrangement 17 can have, for example, a piston and one or more valves. You can also type of DE 10 2005 049 941 A1 be designed in order to be able to carry out a changeable dosing of the amount of fluid to control and change the duration of the solids emptying and thus the current emptying volume V _E . With the Metering arrangement 17 can vary the emptying volume, so that, for example, with increasing solids content in the inlet, the emptying volume can be increased.

In addition, another controllable device 23 - for example a controllable valve - is connected to the inlet 4, with which the inlet flow in the inlet can be changed in order to change the inlet quantity or the current inlet volume P _Z of the starting product AP to be processed per unit of time. This controllable device 23 is connected to the control unit 9 via a data connection 24 .

The aforementioned data connections 18, 20, 21, 24 enable data to be transmitted from or to the control and evaluation unit 9. They can each be designed as lines or else as wireless connections.

Below is an embodiment of a product clarification method, which can be carried out with the separator described above, based on the 2 and 3 explained in more detail, the degree of turbidity TR, in particular of the clear phase KP, being selected as the parameter to be determined in the present exemplary embodiment.

The starting product AP is preferably fed continuously into the drum 1 of 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 to form the clear phase KP, turbid substances and other solids contained in the starting product are collected in the solids collection chamber 8 of the drum 1 outside of the plate pack 14, which fills up. If too many of the solids have accumulated in the solids collection space 8, their discharge begins with the clear phase, which is to be avoided if possible.

In order to monitor the product clarification process, a determination—measurement and/or other determination—of the degree of turbidity TR is carried out. A measuring cell is used for this purpose, for example, which is X-rayed in order to determine the turbidity with the sensor device 22 .

Insofar as the term turbidity is used below in the description of the exemplary embodiment, this configuration is preferred. In the case of an embodiment of the method with a determination of another parameter, the term “turbidity” is to be replaced accordingly by the designation of this parameter.

The procedure - see 3 - starts in step 100 at a start time t ₀ . A time window is or is already defined at this start time t ₀ . In this time window, after previous attempts and tests—which have led to good clarification—the next solids discharge should take place by means of a piston valve 6, if possible after a last solids discharge. The time window is limited by a start time t ₁ :=c ₁ (constant 1) and an end time t ₂ :=c ₂ (constant 2). Furthermore, a maximum emptying volume V _M is defined, which should not be exceeded. However, this can also already be predetermined by the manufacturer or by the user.

In addition, a maximum limit value TR _M for the degree of turbidity TR that is not to be exceeded during the clarification of the starting product AP is or will be preset. The product feed or the feed volume of starting product flowing into the drum 1 and to be clarified there per unit of time is referred to as P _Z . This quantity is defined and set at the start time t ₀ as 100% of the feed capacity of the separator that is possible in the clarification process, which is exemplary but not mandatory.

The start time t ₀ corresponds to the time of a last solids emptying during the centrifugal clarification Z--step 200--which is already running or at the operating speed of the drum 1 in steady state operation--step 200--whereupon turbidity measurements are carried out repeatedly--for example continuously--in/downstream of the outlet 13 are - step 300 - to determine the current turbidity TR.

A solids emptying E of the solids F from the solids collection chamber 8 with the piston valve 6 - step 400 - is carried out when it is determined in step 300 that the determined turbidity value exceeds the maximum turbidity limit TR _M .

In this case, in a step 500 it is checked whether the end of the period t _E from a last solids discharge to the currently performed solids discharge is within the time window t ₁ to t ₂ within which the solids discharge should preferably be triggered by the turbidity measurement.

If it is determined in step 500 that - e.g. due to an increasing proportion of solids in the product feed - a solids discharge before reaching the start time t ₁ of the time interval, the solids discharge E was triggered in step 400 - which means that the solids space in drum 1 is completely full , it is checked whether the volume of the next or then current solids discharge tion V _E is still below a limit value V _Max - step 600. This is certainly the case during the first program run, since it was defined at the start that V _E <V _M . In this case, therefore, the discharge volume is increased for or during the subsequent solids discharge—step 700: for example, V _E is increased here by 10%, so that V _{E NEW} =1.1*V _E applies. Thus, after the next solids emptying—step 400—less solids remain in the solids space 8 and in a next cycle centrifugation can be a little longer so that the lower time limit t ₁ is exceeded if possible before another solids emptying is triggered.

If the solids content in the product feed increases after several cycles or many cycles to such an extent that the maximum emptying volume of the centrifuge is not sufficient to reach or exceed the start time t1 of the time interval, after step 600 has been carried out, the feed quantity is calculated in step 800 as an alternative to step 700 reduced. For this purpose, for example, the following is established: P _Z NEW =0.9*P _Z .

Steps 100 to 800 are repeated iteratively until further emptying is triggered within the emptying time window t ₁ to t ₂ and constant operation with reproducible separation quality is achieved.

In the event that it has been determined - step 500, that the current emptying time t _E is greater than the time to reach the start time t ₁ , it is further checked whether the emptying time t _E is less than or greater than the time to reach the End time t ₂ - step 900.

If this is the case, the parameters remain unchanged and the centrifugal clarification Z is continued unchanged in step 200 .

However, if it is determined in step 900 that, e.g. as a result of the falling solids content in feed 4, the time span t _E has been exceeded before reaching the end time t2 of the time interval from the last to the current solids discharge E in step 400 (this means that the dwell time of the solids in the drum 1 is too long, compaction is imminent), ie if it is determined in step 900 that t _E >t ₂ , the volume of the emptying volume is checked again, for example based on the duration of the solids emptying: step 1000. If - in step 1000 - determined that the current evacuation volume V _E is still greater than the minimum evacuation volume V _Min in step 1000, the evacuation volume V _E of the subsequent solids evacuation is reduced; eg as follows: V _{E NEW :=} 0.9 * V _E; Step 1100.

If, on the other hand, the current discharge volume V _E is already smaller than the minimum discharge volume V _Min , the product feed P _Z is increased; eg as follows: P _{Z NEW :=} 0.9 * P _Z; Step 1120.

Steps 100 to 800 or possibly up to 1200 are repeated iteratively until further emptying is triggered within the emptying time window t1 to t2 and constant operation with reproducible separation quality is achieved.

2 illustrates essential steps of 3 in a different representation.

Overall, product losses due to non-optimal emptying are reduced in a simple manner with the methods shown and claimed.

Reference List

1

drum

2

spindle

3

sensor

4

Intake

5

exhaust ports

6

piston slider

7

solids catcher

8th

solids collection space

9

control unit

10

drum base

11

drum cover

12

Hood

13

process

14

plate pack

15

Hydraulic fluid line

16

Valve

17

dosing arrangement

18

Data Connection

19

hydraulic line

20

Data Connection

21

Data Connection

22

sensor device

23

Controllable device

24

Data Connection

CP

clear phase

AP

starting product

E

solids emptying

f

solids

Z

centrifugal clarification

TR

degree of turbidity

TRM

Maximum turbidity limit

t0

Start time procedure

t1

Start Time Interval

t2

end time interval

t0, t1, t2,

times

te

Time of current emptying

PU

current void volume

VMax

maximum emptying volume

vmin

minimum emptying volume

PZ

Current inflow volume / time unit

p.m

maximum inflow volume / time unit

Claims (13)

Process for clarifying a flowable starting product (AP) with a centrifuge, in particular a separator with a rotatable drum (1) with an inlet (4) and at least one liquid outlet (13) for the continuous outlet of at least one clarified liquid phase - a clear phase - and with discontinuous solids outlet openings (5) to be opened for the discontinuous discharge of a solids phase - referred to as solids emptying -, characterized by at least the following steps: 100: setting or determining a time interval which is limited by a start time (t ₁ ) and an end time (t ₂ ), wherein in the time interval a next solids emptying is to take place after a previous solids emptying; 200: performing a centrifugal clarification of the starting product (AP) in the drum (1); 300: repeated determination of at least one actual value of a parameter, in particular a product or process parameter, during step 200; 400: Carrying out a solids emptying if the parameter deviates from a limit value, in particular exceeds a limit value; and 500, 900: determining the point in time (t _E ) of the current emptying of solids and checking whether this is within the time interval from step 100; and - return to step 200 if the time (t _E ) of the current solids emptying is in the time interval from step 100; - or carrying out a change in an emptying volume for the next emptying of solids if the point in time (t _E ) of the current emptying of solids is not in the time interval from step 100 . procedure after claim 1 , characterized in that in step 100 the following is also defined and/or set: - a maximum limit value (TR _M ) not to be exceeded for the parameter, which is in particular a degree of turbidity (TR) of the clear phase; - the volume of solids to be emptied during the next solids ejection (V _E ) to a value which is less than a maximum value (V _Max ) and greater than a minimum value (V _Min ). procedure after claim 1 or 2 , characterized in that the time interval is within the following range: 0 sec ≤ t ₂ - t ₁ ≤ .300 sec.. Method according to one of the preceding claims, characterized in that if it is determined in step 500 that the last solids emptying E of step 400 was triggered before the start time t ₁ of the time interval was reached, in step 700 the emptying volume (V _E ) for the next solids discharge is increased. procedure after claim 4 , characterized in that the emptying volume (V _E ) for the next solids emptying is increased in step 700 if no maximum emptying volume (V _Max ) has been reached and that the product feed volume (P _Z ) per unit of time is reduced in step 800 if the maximum emptying volume (V _Max ) is reached or exceeded. Method according to one of the preceding claims, characterized in that if it is determined in step 900 that the last solids emptying E of step 400 was triggered after reaching the end time (t2) of the time interval, the emptying volume (V _E ) for the next solids emptying is decreased in a step 1100. procedure after claim 6 , characterized in that the discharge volume (V _E ) for the next solids discharge is reduced in step 1100 if the minimum discharge volume (V _Min ) has not yet been reached and that the product feed volume (P _Z ) per unit time is increased in step 1200, when the minimum evacuation volume (V _Min ) is reached or fallen below. Process according to one of the preceding claims, characterized in that the product parameter of the clear phase (KP) and/or the starting product (AP) is the degree of turbidity (TR). Method according to one of the preceding claims, characterized in that the product parameter of the clear phase (KP) and/or the starting product (AP) is the viscosity and/or the conductivity. Method according to one of the preceding claims, characterized in that the solids are discharged through the discharge openings (5), which are closed and opened by a piston valve (6). Method according to one of the preceding claims, characterized in that the parameter of the clear phase (KP) is determined by at least one sensor device (22) which is arranged in or on an outlet (13) of the separator (1). Method according to one of the preceding claims, characterized in that the parameter of the starting product (AP) is determined by a sensor device (3) which is arranged in or on an inlet (4) of the separator (1). Method according to one of the preceding claims, characterized in that the method is controlled by means of a control unit (9).

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