Method for continuously clarifying a flowable suspension with a centrifuge, which involves a time-limited solid-matter discharge by opening and closing solid-matter discharge openings of the centrifuge to discharge the solid matter

Abstract

A method is provided for continuously clarifying a flowable suspension with a discontinuously solid-dischargingself-dischargingseparator, which has a rotatable drum with a vertical axis of rotation, a feed for the suspension to be clarified and at least one liquid discharge for continuously discharging at least one clarified liquid phase, and discontinuously openable solid-discharge openings for discontinuously discharging the solid phase. The method involves a) measuring one or more of the suspension parameters mass, mass of solid substance in the suspension, mass flow, temperature, density, cumulative density; and b) initiating a time-limited discharge of solid substance as a result of a repeated determination on the basis of step a) in the event of or after the exceeding of a limit value.

Claims

1. A method, comprising: a) continuously clarifying a free-flowing suspension with a centrifuge, wherein the centrifuge discontinuously empties solid matter via openable and closeable solid-matter discharge openings, and comprises a rotatable drum with a vertical axis of rotation, an inlet for receiving the suspension to be clarified, and at least one liquid discharge for continuous discharge of at least one clarified liquid phase; b) measuring one or more of suspension parameters comprising mass, mass of solid matter in suspension, mass flow, temperature, density, cumulative density; and c) initiating a time-limited solid-matter discharge as a result of a repeated determination according to step b) upon reaching or after exceeding a limiting value dependent on one or more of the measured suspension parameters, wherein the time-limited solid-matter discharge comprises opening and then closing the solid-matter discharge openings of the centrifuge to discharge the solid matter, wherein a Coriolis flowmeter, with which a mass flow is determined, determines the one or more of the suspension parameters of the step b), and wherein the measured results from the Coriolis flowmeter protect the centrifuge or a drum of the centrifuge from excessively high densities in the inlet, by preventing feeding of the suspension to be clarified to the inlet when a maximum permissible density of the separator is exceeded.

2. The method of claim 1, wherein the solid-matter mass value or a value proportional to the solid-matter mass value of the solid matter that has been separated from the suspension since the last emptying is determined to determine level of filling of a solid matter chamber of the centrifuge with the solid matter separated from the suspension.

3. The method of claim 1, further comprising: integrating an output signal from the Coriolis flowmeter over time, wherein the initiation of the discharge is performed based on the integrated output signal.

4. The method of claim 3, wherein the integration over time is carried out by accumulating measured values, and the limiting value is a cumulative limiting value.

5. The method claim 1, wherein the free-flowing suspension has a fluctuating solid-matter content.

6. The method of claim 1, wherein the centrifuge is a separator.

7. The method of claim 1 wherein the centrifuge is an automatically emptying separator.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

(1) The invention will be explained in more detail below by using a preferred exemplary embodiment with reference to the appended drawings, in which:

(2) FIG. 1: shows a schematic sectional view of a separator which is operated with the method according to the invention; and

(3) FIG. 2: shows a flowchart to illustrate a method according to the invention.

DETAILED DESCRIPTION

(4) FIG. 1 shows a separator 1 for clarifying free-flowing starting suspensions SU containing turbid matter, having a rotatable drum with a vertical axis of rotation. The processing of the suspension is carried out in continuous operation. This means that the input of suspension is carried out continuously, as is the discharge of at least one clarified liquid phase, called the clear phase.

(5) The automatically emptying separator has a discontinuous solid-matter discharge for this purpose, wherein the solid matter S separated from a suspension by clarification is emptied at intervals by opening and re-closing discharge nozzles or discharge openings 5.

(6) 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 additionally placed on a drive spindle 2, which is rotatably mounted and can be motor-driven.

(7) The drum has a suspension inlet 4, through which a suspension SU to be clarified is led into the drum. It also has at least one outlet 13 with a gripper, which is used to lead a clear phase L out of the drum. The gripper is a type of centripetal pump. However, the liquid discharge could also be managed with other means. In addition, it would also be conceivable, in addition to the clarification, to perform separation of the suspension into two liquid phases of different density. A further liquid outlet would be required for this purpose.

(8) The drum preferably has a disk pack 14 made of axially spaced separating disks. Between the outer circumference of the disk pack 14 and the inner circumference of the drum, in the area of the greatest internal diameter of the latter, there is formed a solid-matter collecting chamber 8. Solid matter separated from the clear phase in the area of the disk pack 14 collects in the solid-matter collecting chamber 8, from which the solid matter 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 valve 6, which is arranged in the lower drum part 11. When the discharge openings are opened, the solid matter S is thrown out of the drum into a solid-matter collector 7.

(9) To move the piston valve 6, the drum has an actuating mechanism. Here, this 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. Thus, the input of the control fluid such as water is made possible by a control valve 17 arranged outside the drum, which is arranged in a feed line 19 for the control fluid that is arranged outside the drum, so that for an emptying action by opening the control valve, the control fluid can be sprayed into the drum or, vice versa, the inflow of control fluid can be interrupted in order to move the piston valve appropriately in order to open the discharge openings. The actuating mechanismhere the control valve 17is connected via a data line 18 to a control unit 9 for controlling and/or regulating the solid-matter discharge.

(10) A Coriolis sensor 20 is arranged in the inlet 4. The Coriolis sensor 20 is designed as a Coriolis mass flowmeter. The function of a Coriolis sensor designed as a Coriolis mass flowmeter is known per se. If a homogenous mixture of the solid-matter phase S and the liquid phase is present in the incoming suspension SU, via a density measurement, which can likewise be carried out by using the sensor 20, and intrinsically known fluid properties of the suspension, the two phases S and L can be determined proportionally. If necessary, these fluid properties can be determined in trials or in test operation.

(11) The Coriolis sensor 20 is connected via a wired or wire-free data line 21 to the evaluation and control unit 9 (preferably a control computer of the separator), which evaluates the determined measured values and, on the basis of this evaluation, controls the emptying and therefore the opening of the discharge openings 5.

(12) During the clarification of the suspension SU, forming the clear phase L, turbid matter contained in the suspension to be clarified and other solid matter is collected in the solid-matter collecting chamber 8 of the separator, which is filled. If too much of the solid matter is collected in the collecting chamber 8, the discharge thereof with the clear phase begins (FIG. 2), which should be avoided if possible.

(13) In the following text, with reference to FIG. 2, an exemplary embodiment of a method according to the invention, which is carried out by means of the above-described separator, will be explained in more detail.

(14) The suspension SU is preferably led continuously into the separator, in which said suspension is clarified. A continuing clear phase discharge of the clear phase L is carried out.

(15) Arranged in the inlet 4 is the Coriolis sensor 20, with which, in a step 100, measures one or more of the suspension parameters comprising mass, mass of solid matter in suspension, mass flow, temperature, density and/or cumulative density. The signal from the Coriolis sensor 20 is added up in a step 200 by the control unit 9 of the separator or by electronics integrated into the Coriolis sensor. This cumulative value is stored temporarily in an accumulator in the sensor itself or preferably in the control unit.

(16) Then, the cumulative valuepreferably a mass value or a value proportional to the mass valueis compared in a step 300 with a predefined and previously stored limiting value. This predefined limiting value can, for example, have been determined previously during measurements in trial operation in such a way that it corresponds to an 80% filling of the solid matter collecting chamber with solid matter.

(17) As long as a limiting value has not been reached, steps 100 and 200 are repeatedly run through again (indicated by the downward arrow by the 300).

(18) On the other hand, when the limiting value is reached or exceeded, in a step 400 the piston valve is actuated to empty the solid matter from the collecting chamber. In a step 500, the accumulator is set back to zero and a measurement according to step 100 and an accumulation of the measured values in the accumulator according to step 200 are repeatedly started again until a renewed emptying action.

LIST OF DESIGNATIONS

(19) 1 Separator 2 Spindle 4 Inlet 5 Discharge openings 6 Piston valve 7 Solid-matter collector 8 Solid-matter collecting chamber 9 Evaluation unit 10 Lower drum part 11 Drum cover 12 Hood 13 Outlet 14 Disk pack 15 Line for hydraulic fluid 16 Valve 17 Control valve 18 Data line 19 Hydraulic line 20 Sensor 21 Data line SU Suspension L Liquid phase/clear phase Solid matter