Method for clarifying a flowable product with a centrifuge having discontinuously openable solid-discharge openings

Abstract

A method is provided for clarifying a flowable starting product with a separator having a feed and at least one liquid discharge for continuously discharging at least one clarified liquid phasea clear phaseand with discontinuously openable solid-discharge openings for discontinuously discharging the solid phase. The method involves the steps: a. setting or determining a starting time; b. repeatedly determining at least one actual value of a product-parameter of the clear phase derived from the drum; c. determining the time interval until the product-parameter actual value reaches or exceeds a product-parameter limit value; d. preferably initiating a solid discharge as a result of reaching or exceeding the product-parameter limit value; e. determining and setting an operating time interval by using the determined calibrating time interval, the operating time interval being less than or greater than the ascertained calibrating time interval; and f. initiating at least one or more solid discharges each time the set operating time interval has elapsed.

Claims

1. A method, comprising: clarifying a flowable starting product using a separator with a rotatable drum, a feed, at least one liquid discharge for continuously discharging at least one clarified liquid phase, and discontinuously openable solid-discharge openings for continuously discharging the solid phase by a. setting or determining a starting time; b. repeatedly determining at least one actual value of a single product-parameter of the at least one clarified liquid phase drawn off from the rotatable drum, wherein the single product-parameter of the at least one clarified liquid phase is one of degree of turbidity, a viscosity, and a conductivity; c. determining a calibrating time interval from the starting time until a time at which the single product-parameter actual value of the at least one clarified liquid phase or a difference quotient of the determined single product-parameter actual values of the at least one clarified liquid phase and respective time intervals between the measurements reaches or exceeds a product-parameter limit value; d. initiating a solid discharge via the solid-discharge openings in response to the determined actual value of the at least one clarified liquid phase reaching or exceeding the product-parameter limit value; e. determining and setting an operating time interval using the determined calibrating time interval, wherein the operating time interval is less than the determined calibrating time interval; and f. initiating one of the plurality solid discharges each time the set operating time interval elapses.

2. The method of claim 1, wherein a time of a first solid discharge is determined in step a.

3. The method of claim 1, wherein steps a.-f. are only repeated after a predetermined number of passages of operating time intervals.

4. The method of claim 1, further comprising: determining a volumetric flow or a product-parameter of the flowable starting product fed to the separator, wherein steps a.-f. are repeated if the volumetric flow changes or the product-parameter of the flowable starting product changes up to or beyond a limit value.

5. The method of claim 1, wherein the setting of the operating time interval is performed in such a way that, within the operating time interval, the product-parameter directly before the solid discharge deviates by less than 20% from the product-parameter directly after the solid discharge.

6. The method of claim 5, wherein the operating time interval is at least 10% less than the calibrating time interval.

7. The method of claim 1, wherein the solid discharge is initiated if the difference quotient reaches or falls below, or exceeds, a predetermined limit value one or more times.

8. The method of claim 1, wherein the solid discharge takes place through discharge nozzles, which are closed and opened by a piston slide valve.

9. The method of claim 1, wherein determination of the at least one actual value of the product-parameter of the at least one clarified liquid phase is performed by a sensor arranged in or at an outlet of the separator.

10. The method of claim 1, further comprising: determining, using a sensor arranged in or at the feed of the separator, at least one actual value of a product-parameter of the starting product.

11. The method of claim 10, further comprising: determining, by an evaluation unit, a calibrating time interval and operating time interval; and setting, by the evaluation unit, the operating time interval, wherein the evaluation unit is connected to the sensor and the evaluation unit allows a hydraulic setting of a position of a piston slide valve in the drum.

12. A method, comprising: clarifying a flowable starting product using a separator with a rotatable drum, a feed, at least one liquid discharge for continuously discharging at least one clarified liquid phase, and discontinuously openable solid-discharge openings for continuously discharging the solid phase by a. setting or determining a starting time; b. repeatedly determining at least one actual value of a product-parameter of the at least one clarified liquid phase drawn off from the rotatable drum; c. determining a calibrating time interval from the starting time until a time at which the product-parameter actual value of the at least one clarified liquid phase or a difference quotient of the determined product-parameter actual values of the at least one clarified liquid phase and respective time intervals between the measurements reaches or exceeds a product-parameter limit value; d. initiating a solid discharge via the solid-discharge openings in response to the determined actual value of the at least one clarified liquid phase reaching or exceeding the product-parameter limit value; e. determining and setting an operating time interval for a plurality of solid discharges using the determined calibrating time interval and independent of further determinations of the product-parameter actual value of the at least one clarified liquid phase, wherein the operating time interval is less than the determined calibrating time interval; and f. initiating one of the plurality solid discharges each time the set operating time interval elapses.

13. The method of claim 12, wherein a time of a first solid discharge is determined in step a.

14. The method of claim 12, wherein steps a.-f. are only repeated after a predetermined number of passages of operating time intervals.

15. The method of claim 12, further comprising: determining a volumetric flow or a product-parameter of the flowable starting product fed to the separator, wherein steps a.-f. are repeated if the volumetric flow changes or the product-parameter of the flowable starting product changes up to or beyond a limit value.

16. The method of claim 12, wherein the operating time interval is at least 10% less than the calibrating time interval.

17. The method of claim 12, wherein the solid discharge is initiated if the difference quotient reaches or falls below, or exceeds, a predetermined limit value one or more times.

18. The method of claim 12, wherein the product-parameter of the at least one clarified liquid phase and/or of the starting product is at least one of a degree of turbidity, a viscosity, and a conductivity.

19. The method of claim 12, wherein determination of the at least one actual value of the product-parameter of the at least one clarified liquid phase is performed by a sensor arranged in or at an outlet of the separator.

20. The method of claim 12, further comprising: determining, using a sensor arranged in or at the feed of the separator, at least one actual value of a product-parameter of the starting product; determining, by an evaluation unit, a calibrating time interval and operating time interval; and setting, by the evaluation unit, the operating time interval, wherein the evaluation unit is connected to the sensor and the evaluation unit allows a hydraulic setting of a position of a piston slide valve in the drum.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

(1) The invention is explained more specifically below on the basis of a preferred exemplary embodiment with reference to the appended drawings, in which:

(2) FIG. 1 illustrates a schematic sectional view of a separator that is operated by the method according to the invention;

(3) FIG. 2 illustrates, by way of example, a curve plotted over the course of a measurement from an application of the method according to the invention;

(4) FIG. 3 illustrates a flow diagram relating to a method according to an embodiment of the invention;

(5) FIG. 4 illustrates, by way of example, a curve plotted over the course of a measurement from an application of a further method according to the invention; and

(6) FIG. 5 illustrates a flow diagram relating to an alternative method of FIG. 4.

DETAILED DESCRIPTION

(7) FIG. 1 shows a separator 1 for clarifying flowable starting products AP containing turbid substances, with a drum with a vertical axis of rotation. The processing of the product takes place in continuous operation. In other words, the product feed takes place continuously and so does the drawing off of at least one clarified liquid phase, known as the clear phase.

(8) The separator has a discontinuous solid discharge, the solid matter F that is separated from the starting product by clarification being removed at intervals by the opening and re-closing of discharge nozzles or discharge openings 5.

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

(10) The drum has a product feed 4, through which a starting product AP is directed into the drum. It also has at least one outlet 13 with a gripper, which serves for drawing off a clear phase KP from the drum. The gripper is a kind of centripetal pump. The liquid discharge could, however, also take place by other means. Moreover, it would also be conceivable to perform in addition to the clarification also a separation of the product into two liquid phases of different densities. For this purpose, a further liquid outlet would be required.

(11) The rotatable drum with a vertical axis of rotation preferably has a disk stack 14 comprising axially spaced apart separating disks. Formed between the outer circumference of the disk stack 14 and the inner circumference of the drum, in the region of its greatest inside diameter, is a solids collecting chamber 8. Solids that are separated from the clear phase in the region of the disk stack 14 collect in the solids collecting chamber 8, from which the solids can be discharged from the drum by way of the discharge nozzles 5. The discharge nozzles 5 can be opened and closed by means of a piston slide valve 6, which is arranged in the lower drum part 11. With the discharge nozzles open, the solid matter F is directed out of the drum into a solids catcher 7.

(12) For moving the piston slide valve, the drum has an actuating mechanism. Here, this mechanism comprises at least one feed line 15 for a control fluid such as water and a valve arrangement 16 in the drum and further elements outside the drum. This makes it possible for the control fluid such as water to be fed by way of a control valve 17 arranged outside the drum, which is arranged in the feed line 19 for the control fluid arranged outside the drum, so that, for an evacuation, the control fluid can be injected into the drum by releasing the control valve or, conversely, the flow of control fluid can be interrupted in order to move the piston slide valve correspondingly to expose the discharge openings. The actuating mechanismhere the control valve 17is connected by way of a data line 18 to a control unit 9 for the open-loop or closed-loop control of the solid discharge.

(13) Arranged at or in the outlet 13 of the clear phase there is at least one sensor 22, which is designed to determine one or more product parameters of the at least one clear phase. Product parameters in connection with the present invention are, in particular, physical properties of the clear phase measuring medium, such as the degree of turbidity, the viscosity or else the conductivity (for example in the case of salt solutions). The at least one sensor 22 may be a photocell for determining the light transmissivity.

(14) Arranged at or in the feed 4 for the starting product AP into the drum there is preferably likewise a sensor 3 for determining the through-flow of one or more product parameters of the starting product to be directed into the drum. These product parameters may also be physical parameters, such as the turbidity or the viscosity of the starting product.

(15) Such measuring methods may also be carried out using sensors as transmission measurements or scattered-light measurements. A further possibility for determining the degree of turbidity is the use of ultrasound measurements.

(16) By contrast, method parameters such as the volumetric through-flow or through-flow rate are also known. In a preferred configurational variant, the sensor may be respectively integrated in a measuring device, which determines a product parameter, for example the degree of turbidity or the conductivity, and at the same time determines a method parametersuch as for example the through-flow rate of the clear phase.

(17) As already mentioned, by analogy with the determination of the product parameters of the clear phase KP, in a particularly preferred variant a turbidity measurement and/or a viscosity measurement of the starting product AB may be performed at the product feed 4.

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

(19) It goes without saying that the aforementioned data lines 18, 20, 21 make a data transmission from or to the evaluation unit 9 possible, and can even be replaced by wireless connections.

(20) The method according to the invention, which is carried out by the separator described above, is described more specifically below, the degree of turbidity having been chosen in the present exemplary embodiment as the product parameter.

(21) The starting product AP is directed, preferably continuously, into the separator, where it is clarified. A continuous clear-phase discharge of the clear phase KP takes place.

(22) During the clarification of the starting product AP, with the formation of the clear phase KP, turbid substances contained in the starting product and other solids are collected in the solids collecting chamber 6 of the separator, which fills up. When too much solid matter has collected in the collecting chamber 6, it begins to be discharged with the clear phase (FIG. 2), which should be avoided as far as possible.

(23) In order to monitor the clarification, until now the measurement and determination of the degree of turbidity has been carried out by a measuring cell. This involved presetting a limit value for the turbidity value that was not to be exceeded and then performing an evacuation of the solid matter F from the solids collecting chamber 6 whenever the determined turbidity value exceeded the limit value.

(24) According to a configurational variant of the method as provided by the invention, as before, first an determination is performed of the time interval from the last evacuation of the solids chamber 7 of the separator 1 up to the reaching of a prescribed first turbidity limit value. This method step is subsequently referred to as the determination of a calibrating time interval. The calibrating time interval is defined as the time between the last evacuation of the solids chamber of the separator up until the reaching of the first degree of turbidity limit value. As soon as the measured turbidity content has reached the first limit value, an evacuation of the solids chamber 7 takes place. The evacuation of the solids chamber 7 during this method step is controlled by the measurement and reaching of the setpoint value.

(25) After the determination of the calibrating time interval, an operating time interval is set. The operating time interval can be determined by subtracting a prescribed time interval from the calibrating time interval. After passing the certain operating time interval, a solid evacuation then takes place in a time-controlled manner. As a result, an increase in the degree of turbidity is as it were pre-empted and it is ensured that the quality of the clear phase is almost constantly good. A measurement of the turbidity content during this method step is not absolutely necessary but is conceivable, in order to intervene if, contrary to expectations, the limit value is possibly reached prematurely.

(26) After repeated, for example n successive, passages of the operating time interval, each time with a subsequent evacuation of the solids chamber 6, it can happen that the degree of turbidity of the clear phase increases again. In this case, n may vary preferably between 5 and 50, particularly preferably between 8 and 30, passages. It is therefore recommendable after the nth passage of operating time intervals, to carry out a renewed determination of the calibrating time interval and renewed setting of the operating time interval.

(27) The corresponding operations for evaluation of the measurement signals and also the open-loop and/or closed-loop control of the evacuation process are ensured by the evaluation unit 9.

(28) Since, among the factors on which the degree of turbidity of the clear phase is based is the degree of turbidity of the starting product, it is advisable to also monitor the conditions at the feed of the starting product. For instance, the through-flow may be detected. It is also conceivable, however, to provide a measuring cell for measuring the feed flow at the feed 4. If this changes, a renewed determination of the calibrating time interval can be initiated.

(29) FIG. 2 represents the variation over time of the degree of turbidity T of the clear phase if the previous method is applied.

(30) 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 rapidly. In the 11th minute, the setpoint value of 5% turbidity is reached and a solid evacuation takes place. As a result, the degree of turbidity consequently falls again to 1%. In this case, the time window t(K) represents the calibrating time interval.

(31) The time interval may be set manually or be determined computationally or in dependence on measured values in a database. For example, the operating time interval t(b) may be determined by multiplication of the calibrating time interval by a factor of less than 1.

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

(33) FIG. 3 illustrates a sequence of steps of a method according to an embodiment of the invention. Specifically, in step a. a starting time is set or determined. In step b. repeatedly determining at least one actual value of a product parameter of the clear phase (KP) drawn off from the drum is repeatedly determined. Step c. involves 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. In step d. a solid discharge as a consequence of reaching or exceeding the limit value, in particular the product-parameter limit value is preferably initiated. Step e. involves determining 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 less than or equal to or greater than the ascertained calibrating time interval t(K). In step f. at least one or more solid discharges is initiated each time the set operating time interval t(B) has elapsed. After step f), the method can start again at step a) and run through these once again.

(34) FIG. 5 illustrates a sequence of steps of a method according to an embodiment, which as illustrated by FIG. 4, is based on the example of the product parameter degree of turbidity in dependence on time. The degree of turbidity T is determined by measurements respectively carried out in time intervals. Specifically, in step a. a starting time is set or determined. In step b. at least one actual value of a product parameter of the clear phase (KP) drawn off from the drum is repeatedly determined or measured. Step c. involves determining difference quotients from the determined product-parameter actual values and the respective time intervals between the measurements and evaluating the difference quotients. In step d. a solid discharge is initiated as a consequence of the evaluation in step c).

(35) Then, the difference quotients
?T/?t
are determined from the measured values of the degree of turbidity
?T:=T1?T2

(36) and the time intervals
?t:=t2?t1

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

(38) The detection of a change, for example an increase, in the difference quotient makes it possible at a relatively early time to detect a commencing more rapid increase in the turbidity. In this situation, an additional solid evacuation is advisable. Also with this procedure, the risk of belated evacuations can also be prevented.

LIST OF DESIGNATIONS

(39) 1 Separator 2 Spindle 3 Sensor 4 Feed 5 Discharge openings 6 Piston slide valve 7 Solids catcher 8 Solids collecting chamber 9 Evaluation unit 10 Lower drum part 11 Drum cover 12 Shroud 13 Outlet 14 Disk stack 15 Line for hydraulic fluid 16 Valve 17 Control valve 18 Data line 19 Hydraulic line 20 Data line 21 Data line 22 Sensor KP Clear phase AP Starting product F Solids t(K) Calibrating time interval t(B) Operating time interval t(Z) Preset time interval n Number of successive passages of the operating time interval with subsequent solid discharge