EP3060351B1 - Method for continuously clarifying a flowable suspension with a centrifuge - Google Patents

Description

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

After US 5,318,500 a relatively complex mass balance determination is required to control the emptying parameters of a self-emptying separator.

After EP 2 644 278 A1 a change in inlet pressure or flow into the drum is required to control the drain parameters of a self-draining separator.
After WO 2011/093784 A To control a centrifuge with a Coriolis flow meter, a pump in the recirculation line is controlled on the basis of a density measurement in a recirculation line.
From the DE 28 14 523 A1 A method for controlling a separator is known, in which a determination of the flow rates of a product at the inlet and outlet of the separator is required, as well as a determination of the concentration of the heavy phase in the outlet flow.
From the DE 32 28 074 A1 a method is known which advantageously enables control of a continuously emptying clarifier with a drum. Here, a suspension 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 in the clear phase becomes too high, 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 discontinuously opened and closed with the aid of a piston valve Discharge openings are emptied when the degree of turbidity measured with the photocell exceeds a certain limit.

This method has also proven itself in certain applications. Unfortunately, there are solids that can blind the photocell over time, so that in these cases the separator cannot be controlled satisfactorily. There is therefore a need for simple and yet as precise as possible methods by means of which a moment which is particularly suitable for emptying solids is determined when clarifying suspensions of solids with discontinuously self-emptying separators.

The object of the invention is to solve this problem.

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

The limit value is one that can be determined directly from the (preferably) temporal behavior of the one or more suspension parameters. However, it can also be such a limit value that can be determined from the first (or second or nth) derivation of the temporal behavior of the one or more suspension parameters, for example in the form of a difference quotient from the measured values of the suspension parameter and the time intervals between the measurements of the Suspension parameters.

The direct or indirect determination of one or two or more of the parameters mentioned makes it possible to determine in each case the solids mass (or a value proportional thereto) that has been separated from the suspension since the last emptying, in order to draw a conclusion about the degree of filling of the solids space pull with solid separated from the suspension, which has collected in the solid collecting space. In particular, the solid must not reach the edge of the stack of plates. If the determined solids mass value therefore exceeds a predetermined limit value, for example determined in test operation, an emptying is triggered by the To completely or at least largely empty the solids collecting chamber of solids.
The Coriolis flow meter is suitable for determining the suspension and / or solids mass, with which a sufficiently precise determination of this value or these values is possible in a simple manner. The Coriolis flow meter is preferably designed to measure the mass flow, the density and the density in parallel as a totalizer. It also preferably measures the temperature. Density as a totalizer means that the density is measured again and again at intervals, that (directly or suitably processed, e.g. multiplied by the time interval between measurements) the sum of these values is formed and thus a value is determined that corresponds directly to the solids mass.

If the suspension to be processed has a relatively constant, constant solids content, it is sufficient to determine the mass flow per time of incoming suspension and to integrate it over time, in particular by adding it up, in order to calculate the solids content that arises in the calculation Solid collection space has collected.
If this fluctuates, on the other hand, it may be necessary to determine how high the solids content in the incoming suspension is at the time using a pre-stored table, e.g. determined in the experiment, or with the aid of a predetermined functional relationship and the measurement of a further suspension parameter such as the density is just what is possible with modern Coriolis flowmeters. With an additional temperature determination, which the Coriolis flow meter can preferably also carry out in an integrated manner, and with a supplementary summation of the measured values - which is also preferably carried out directly by the Coriolis flow meter / sensor, the degree of filling of the solids collecting space of the drum can be determined.

At the same time, the Coriolis flow meter (Coriolis meter) can be used to protect the self-draining separator or its drum against excessive densities in the inlet by preventing the inlet (e.g. by switching a valve) when the maximum permitted density for the respective self-draining separator is exceeded. This value is already known and is shown for each separator.

The individual process steps do not necessarily have to be carried out in one structural unit of the separator, but can also be carried out by external devices (in particular measuring devices, sensors, control unit individually or in combination of these and possibly other devices).

Advantageous embodiments of the invention are the subject of the subclaims.

• Fig. 1 : eine schematische Schnittansicht eines Separators, welcher mit dem erfindungsgemäßen Verfahren betrieben wird; und
• Fig. 2: ein Flussdiagramm zur Veranschaulichung eines erfindungsgemäßen Verfahrens.

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 : a schematic sectional view of a separator, which is operated with the inventive method; and
• Fig. 2 : A flowchart to illustrate a method according to the invention.

Fig. 1 shows a separator 1 for clarifying fluid-containing starting suspensions SU with a rotatable drum with a vertical axis of rotation. The suspension is processed in continuous operation. Ie, the suspension feed takes place continuously and also the removal of at least one clarified liquid phase, called the clear phase.

The self-draining separator has a discontinuous solids discharge, the one separated from a suspension by clarification Solid S is emptied 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 placed on a drive spindle 2 which is rotatably mounted and can be driven by a motor.

The drum has a suspension inlet 4 through which a suspension SU to be clarified is passed into the drum. It also has at least one outlet 13 with a gripper, which is used to derive a clear phase L 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 suspension into two liquid phases of different densities. This would require a further liquid drain.

The drum preferably has a plate pack 14 made of axially spaced separating plates. A solids collecting space 8 is formed between the outer circumference of the plate pack 14 and the inner circumference of the drum in the area 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 openings 5. The discharge openings 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 openings are open, the solid S is thrown out of the drum into a solid catcher 7.

The drum has an actuating mechanism for moving the piston slide 6. 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 which is arranged outside the drum and which is in a supply line arranged outside the drum 19 is arranged for the control fluid, 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 interrupted in order to move the piston slide accordingly in order to open the discharge openings. The actuating mechanism - here the control valve 17 - is connected via a data line 18 to a control unit 9 for controlling and / or regulating the solids discharge.

A Coriolis sensor 20 is arranged in the inlet 4. The Coriolis sensor 20 is designed as a Coriolis mass flow meter. The function of a Coriolis sensor designed as a Coriolis mass flow meter is known per se. If a homogeneous mixture of the solid phase S and the liquid phase is present in the incoming suspension SU, the two phases S and L can be determined proportionately by means of a density measurement which can also be carried out with the sensor 20 and the fluid properties of the suspension which are known per se. Possibly. these fluid properties are determined in tests or in test mode.

The Coriolis sensor 20 is connected via a wired or wireless data line 21 to the evaluation and control unit 9 (preferably a control computer of the separator), which evaluates the measured values determined and controls the emptying and thus the opening of the discharge openings 5 as a function of this evaluation.

During the clarification of the suspension SU to form the clear phase L, turbid substances and other solids contained in the suspension to be clarified are collected in the solids 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.

Below is with reference to Fig. 2 an embodiment of a method according to the invention, which is carried out by means of the separator described above, explained in more detail.

The suspension SU is preferably passed continuously into the separator, in which it is clarified. There is a continuous clear phase discharge of the clear phase L.

Coriotis sensor 20 is arranged in inlet 4 and is used in step 100 to measure one or more of the suspension parameters mass, solid mass in suspension, mass flow, temperature, density and / or totalizer density. The signal of the Coriolis sensor 20 is summed up by the control unit 9 of the separator or by electronics integrated in the Coriolis sensor in a step 200. This totalized value is temporarily stored in a totalizer in the sensor itself or preferably in the control unit.

The summed value - preferably a mass value or a value proportional to the mass value - is then compared in a step 300 with a predetermined and previously stored limit value. This predetermined limit value can, for example, have been determined beforehand during measurements in trial operation in such a way that it corresponds to an 80% filling of the solid collecting space with solid.

As long as the limit value has not been reached, steps 100 and 200 are repeated (indicated by the arrow at "300" down).

On the other hand, when the limit value is reached or exceeded, the solids collecting space is emptied in a step 400 by actuating the piston valve. In a step 500, the total counter is reset to zero and a measurement according to step 100 and a summation of the measured values in the total counter according to step 200 are repeated until they are emptied again.

Reference symbol list:

1

separator

2nd

spindle

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

20

sensor

21

Data line

100, 200, 300, 400, 500

steps

SU

suspension

L

Liquid phase / clear phase

S

Solids

Claims (5)

1. A method for continuously clarifying a free-flowing suspension (SU) with a centrifuge, which is an automatically emptying separator that discontinuously empties solid matter and comprises a rotatable drum having a vertical axis of rotation, having an inlet for the incoming suspension (SU) to be clarified which has one or several suspension parameters, and having at least one liquid discharge for the continuous discharge of at least one clarified liquid phase (L), and solid-matter discharge openings that are to be opened and closed again discontinuously for the discontinuous discharge of the solid phase (S), wherein the drum further comprises a separator disc stack (14) consisting of spaced separator discs,
   characterized by the following steps:

   a) measuring of at least the suspension parameter of mass flow and preferably one or several of the further suspension parameters of mass, mass of solid matter in suspension, temperature, density and cumulative density; wherein for determining the one or the plurality of the suspension parameters at least one Coriolis flowmeter is used,

   b) initiating a time-limited solid-matter discharge as a result of a repeated determination according to step a) upon reaching or after exceeding a limiting value dependent on one or more of the measured suspension parameters, wherein the initiation of the solid-matter discharge is carried out as a result of integration of the output signal from the Coriolis flowmeter over time.
2. The method according to claim 1, characterized in that the solid-matter mass value or a value proportional thereto which has been separated from the suspension since the last emptying is determined in order to draw conclusions about the level of filling of the solid matter chamber with solid matter separated from the suspension.
3. The method according to claim 1 or 2, characterized in that the integration over time is carried out by means of accumulating measured values, and in that the limiting value is a cumulative limiting value.
4. The method according to one of the preceding claims, characterized in that a suspension (SU) having a fluctuating solid-matter content is processed.
5. The method according to one of the preceding claims, characterized in that the measured results from the Coriolis flowmeter (Coriolis meter) are further used to protect the automatically emptying separator or the drum thereof against excessively high densities in the inlet, by the inlet being prevented when a maximum permissible density of the separator is exceeded.

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