Self-dumping Drum Centrifuge For The Clarification Of Liquids, Equipped With A Paring Disk For Removing The Clarified Liquid Under Pressure

Abstract

Self dumping centrifugal separator having a paring chamber and disk for removal of clarified liquid, and, for dumping, a main valve at the periphery of the drum for periodic ejection of solids and a secondary valve for removal of liquid from the separating zone to reduce the discharge of liquid through the main valve during dumping. Means, such as springs, urge the secondary valve into a normally closed position. A control chamber is provided for receiving liquid to urge the secondary valve to the open position and a passageway communicates the control chamber with an annular groove separated by a weir from the paring chamber, the weir being of greater inside diameter than the inside diameter of the paring chamber cover. Upon interruption of flow of clarified liquid from the paring disk, during initiation of dumping, liquid in the paring chamber overflows the weir and flows into the annular groove, through said passageway to the control chamber and forces the secondary valve to the open position for discharge of liquid from the separating zone.

Description

BACKGROUND

The invention relates to a self-dumping drum centrifuge for the clarification of liquids, which is equipped with a paring disk for removing the clarified liquid under pressure. A drum of this kind is described, for example, in German Patent No. 1,182,602.

In drums of this kind, a valve in the line through which the material is delivered for separation and a valve in the line through which the clear phase is removed must be closed in order to prevent any inflow or back-flow of liquid into the drum when the dumping apertures are opened.

In self-dumping drums of the usual design, dumping involves spinning the entire content of the drum into the same catching means where the solids and the liquid recombine. Depending on the nature of the material being separated, however, it may be desirable prior to the opening of the peripheral apertures for the discharge of the solids to let off the liquid filling the central portion of the drum through special apertures situated further inward radially and to capture this liquid in a separate catching means. In this manner liquid losses may be minimized or the solids may be obtained in the highest possible concentration.

A self-dumping drum centrifuge for the clarification of liquids, having a controlled main valve for the periodical discharge of the solids and a separately controlled secondary valve for the prior discharge of the liquid portion of the drum contents, is known, for example, through German Patent No. 1,212,889. In this prior-art design the cylindrical portion of the secondary valve surrounds a concentric chamber which communicates with the separating chamber through one or more bores. These bores are located at approximately the same distance from the axis of rotation as the outer edge of the plate stack. Thus, when the solids chamber is filled, they run from the outermost circumference of the ring of liquid filling the central part of the separating chamber. With the infeed shut off and the main valve closed, and with the secondary valve open, at first only the liquid part of the drum content is let off and is caught by an upper catching means. Then the main valve is opened and substantially naught but the solids are ejected into the lower catching means. On account of the independent operation of the two valves, two separate lines having built-in valves are required for control fluid. The clarified liquid in the prior-art design emerges freely from the drum through an annular plate.

THE INVENTION

The invention is addressed to the problem of constructing a self-dumping clarifying separator with a paring disk such that, when the valve in the line through which the clarified liquid is removed is closed, the liquid part of the drum contents will be automatically let out.

The invention is characterized by a secondary valve, which is known in itself, for the opening and closing of the apertures for letting out the liquid portion of the drum contents, on whose one side a plurality of compression springs are distributed around its periphery and on whose other side a control chamber is provided which communicates through one or more passages with a central annular groove which is separated from the paring chamber by a diaphragm whose inside diameter is larger than the inside diameter of the cover of the paring chamber.

A spring-biased ring which is axially displaceable by means of a control fluid is also known from the previously mentioned German Patent No. 1,182,602. The purpose of this ring, however, is to let the closing fluid out of the closing chamber of the valve controlling the apertures for the discharge of the solids; also, the ring is not actuated by the valve in the clear phase discharge line.

Thus, the invention is concerned with a self-dumping drum centrifuge for the separation of a liquid into a solid fraction and a clarified liquid fraction. The centrifuge comprises a drum having a separating chamber for the separation and a solid collecting chamber disposed radially outwardly of the separating chamber, a paring chamber communicating with the separating chamber for receiving clarified liquid from the separating chamber, a paring disk for removal of clarifying liquid from the paring chamber, a discharge line for receiving clarified liquid from the paring disk for discharge of clarified liquid, a main valve at the periphery of the drum for periodic ejection of solids from the drum for said dumping, and a secondary valve for corresponding periodic discharge of liquid from the separating chamber to reduce the discharge of liquid through the main valve during dumping. The invention provides the improvement which comprises, in the drum, means resiliently urging the secondary valve to the closed position, and means defining a control chamber for the secondary valve for receiving liquid to urge the secondary valve to the open position. An annular groove is separated from the paring chamber by a weir having an inside diameter greater than the inside diameter of the paring chamber cover, and a passageway communicates the annular groove with the control chamber. In operation, upon interrupting flow in the discharge line for discharge of clarified liquid, in the dumping operation, liquid overflows the weir and flows through said passageway to the control chamber for urging the secondary valve to the open position.

AN EMBODIMENT

An embodiment of the invention is represented in the drawing.

The main valve 1 for the periodical ejection of the solids is provided in this embodiment in the lower part 2 of the drum and the secondary valve 3 for letting out the liquid part of the drum contents is provided in the upper part 4 of the drum between the drum cover 5 and the paring chamber cover 6. The two covers 5 and 6 are screwed together by means of a threaded ring 7. The separating zone 3 or chamber 8 is equipped with a plate stack 9. Solids collect in solids collecting zone or chamber 8a. Passages 10 lead from the inner margin of the separating chamber 8 to the paring chamber 11 in which a paring disk 12 is provided for the purpose of pumping the clarified liquid out under pressure. Adjacent the outer margin of the plate stack 9 the drum cover 5 is provided with bores 13 leading to the underside of the secondary valve 3. From the outer sliding surface of the secondary valve 3 bores 14 lead outwardly through the drum cover 5.

On the upper side of the secondary valve 3 there are assembled a plurality of compression springs 15 distributed around its periphery, which urge the secondary valve 3 downwardly during the centrifuging periods, the sealing ring 16 closing the orifices of the passages 13. On the underside of the secondary valve 3 there is a control chamber 17 which communicates through passages 18 with an annular groove 19 separated by means of a weir or diaphragm 20 from the paring chamber 11. Thus, the paring chamber 11 provides an annular groove about the drum axis having an upper lip formed by the paring chamber cover 6, the inside diameter of the upper lip being 6a, and a lower lip formed by the weir or diaphragm 20, the inside diameter of the lower lip being 20a. The lower lip 20 is a separating lip between the annular groove or paring chamber 11 and the annular groove 19. The inside diameter 20a of the lower lip or diaphragm 20 is greater than the inside diameter 6a of the upper lip 6. A valve 22 is installed in the line 21 through which the material to be separated is delivered, and a valve 24 is provided in the line 23 through which the clarified liquid is removed.

The drum operates in the following manner:

Let it be assumed that the drum is controlled by a timed programming mechanism. During the centrifuging periods the valves 22 and 24 are open and the sliding valves 1 and 3 are closed. The solids separated from the liquid collect in the solids chamber outside of the plate stack 9, and the clarified liquid, after flowing through the interstices between the plates, passes through the passages 10 into the paring chamber 11 from which it is pumped away under pressure by means of the paring disk 12. The free fluid level in the paring chamber is, let us say, at 25. After the solids chamber has filled up with solids, i.e., at the end of the time period that has previously been calculated and for which the programming mechanism has been set, valves 22 and 24 are closed by the programming mechanism, which is not shown. This shuts off the clarified liquid line 23. The liquid remaining in the feed line 21 flows in and causes an inward displacement of the free fluid level in the paring chamber 11. Since the inside diameter of the weir or diaphragm 20 is greater than the inside diameter 6a of the paring chamber cover 6, liquid passes over into the annular groove 19 and passes from there through passages 18 into the control chamber 17. As soon as the opening force exceeds the closing force of the springs 15, the sliding valve 3 moves upwardly and uncovers the ports of passages 13. The liquid portion of the drum contents and the contents of the control chamber 17 are together released through channels 14 and are captured by the catching means 26. As soon as the receding level of the liquid in the plate stack 9 and in control chamber 17 causes the closing force of springs 15 to predominate, the sliding valve 3 returns to the closed position. At the end of the delay time preset in the programming mechanism, the main valve 1 is opened in a known manner. The solids then ejected through the bores 27 are captured by the catching means 28. The next centrifuging period commences with the closing of the main valve 1 and the opening of valves 22 and 24 by the programming mechanism.

Since only a small amount of liquid is needed in order to fill the control chamber 17, the fluid that is still present in the infeed tube 21 will normally suffice for filling the control chamber 17 for opening of secondary valve 3. For safety reasons, however, it may be desirable to close the valve in the clear phase discharge line 23 somewhat earlier than closing of the valve 22 in the infeed line 21.

Claims

What is claimed is:

1. In a self-dumping drum centrifuge for the separation of a liquid into a solids fraction and a clarified liquid fraction comprising a drum having a separating chamber for said separation and solids collecting chamber disposed radially outwardly of the separating chamber, a paring chamber having a paring chamber cover, said paring chamber communicating with the separating chamber for receiving clarified liquid from the separating chamber, a paring disk for removal of clarified liquid from the paring chamber, a discharge line for receiving clarified liquid from the paring disk for discharge of clarified liquid, a main valve at the periphery of the drum for periodic ejection of solids from the drum for said dumping, and a secondary valve in the drum communicating with the separating chamber for corresponding periodic discharge of liquid from the separating chamber to reduce the discharge of liquid through the main valve during dumping, the improvement which comprises, in the drum, means urging the secondary valve to the closed position, means defining a control chamber for the secondary valve for receiving liquid to urge the secondary valve to the open position, means defining an annular groove separated from the paring chamber by a weir having an inside diameter greater than the inside diameter of the paring chamber cover, and a passageway communicating said annular groove with the control chamber, whereby upon interrupting flow in said discharge line in the dumping operating, liquid overflows said weir and flows through said passageway to the control chamber for urging the secondary valve to the open position.

2. Centrifuge according to claim 1, the means urging the secondary valve to the closed position being a resiliently acting means.

3. A self-dumping drum centrifuge for the separation of a liquid into a solids fraction and a clarified liquid fraction comprising a drum having a separation chamber for said separation and a solids collecting chamber disposed radially outwardly of the separating chamber, a solids discharge aperture at the drum periphery for discharge of solids from the drum periphery, a solids discharge valve for closing and periodically opening of the drum aperture for periodic discharge of solids, a first annular chamber in the drum formed as an annular groove about the drum axis having an upper lip and a lower lip, means for feeding a liquid to the first annular chamber, a liquid discharge aperture in the drum communicating with the separating chamber for discharge of liquid from the separating chamber to reduce the discharge of liquid during dumping through the solids discharge aperture, a liquid discharge valve for closing and periodically opening of said liquid discharge aperture in correspondence with the opening of the solids discharge valve to reduce said discharge of liquid during dumping, means urging the liquid discharge valve to the closed position, means defining a control chamber for the liquid discharge valve for receiving control liquid to urge the liquid discharge valve to the open position, a control liquid receiving chamber in the drum formed as an annular groove about the drum axis, a passageway communicating said control chamber and the control liquid receiving chamber, one of said lips of said first chamber being a separating lip separating the first chamber and the control liquid receiving chamber, said separating lip being of greater inside diameter than the other of said lips.