Method for processing a flowable product by electrically charging particles in the flowable product and a disc stack of a centrifuge

Abstract

A method for processing a flowable product using a centrifuge includes pretreating the flowable product so that particles in the flowable product are increasingly attracted by electrically charged components, feeding the flowable product into the disc stack, generating an electric charge on the discs of the disc stack, and separating the charged particles from the flowable product within the disc stack under the influence of electrostatic attractive forces and a centrifugal field.

Claims

1. A method for processing a flowable product using a centrifuge, wherein the centrifuge includes a vertical axis of rotation with a rotatable centrifuge drum, wherein a disc stack is disposed in the rotatable centrifuge drum, a product outlet for discharging a liquid phase, and a solids discharge opening for discharging a solid phase, comprising the acts of: a) pretreating the flowable product so that particles in the flowable product become electrically charged; b) feeding the pretreated flowable product into the disc stack; c) electrically charging the disc stack; and d) separating the electrically charged particles from the flowable product within the electrically charged disc stack; wherein the disc stack is electrically charged by applying a pole of a DC voltage source directly to the disc stack, and further comprising the act of reversing a polarity of the disc stack or disconnecting the disc stack from the DC voltage source.

2. The method according to claim 1, wherein the disc stack and the particles have opposite electrical charges.

3. The method according to claim 1, wherein the reversing or the disconnecting occurs periodically in time or as a function of a clarification behavior in the disc stack.

4. The method according to claim 1, wherein the pretreating is performed before the flowable product is introduced into the rotatable centrifuge drum.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The FIGURE shows a sectional partial view of a separator drum of hermetically sealed design.

DETAILED DESCRIPTION OF THE DRAWING

(2) A rotatable separator drum 1 with vertical axis of rotation D is placed on a turning spindle 2, which is driven by a direct drive or by a belt drive, not shown here.

(3) The turning spindle 2 is conically shaped along an upper circumferential area and is fastened to the lower part of the drum 20 with a fastening means 6.

(4) A product feed pipe 4 is followed by a product feed pipe 5 which rotates during operation and is aligned concentrically to the axis of rotation D. From the product feed pipe 5, product P runs into a distributor 7 with distributor holes or ribs from which the flowable product can exit, e.g., in a radial direction into the interior of the separator drum 1. It is also conceivable (not shown here) to lead the product from the distributor into at least one rising channel in the disc stack.

(5) Inside the separator drum 1, the incoming product flows in disc gaps between conical discs of a disc stack 11 axially spaced by means of spacers.

(6) The product is clarified in the disc gaps (and possibly also separated into two or more liquid phases) in that solid particles of the flowable product are deposited on the undersides of the discs, which can then escape into a solids collection chamber 8. From there, the solid phase SP here is discontinuously discharged in a radial direction from the separator drum 1 via solids discharge openings 10, which can be opened and closed via a piston slide 9. The liquid phase LP is led to a pump element 12 and from there it is discharged through a product outlet 13.

(7) In the present case, better separation of solid particles in the disc gaps of a disc stack is made possible by applying an electric charge to disc stack 11. This also causes particles that have already been separated to adhere to the underside of the disc.

(8) For this purpose, an outer wall 18 of the separator drum 1 or an outer wall 19 of the pump element 12 is connected to a positive and a negative pole of a DC voltage source 14 via an electric line 15a or 15b respectively.

(9) A component that is easily accessible from the outside, here the outer wall 19 of pump element 12, consists of an electrically conductive material and is conductively connected to the disc stack so that it is charged positively or negatively depending on the connection to the DC voltage source. Another component, such as the actual separator drum 1, is polarized in the opposite direction.

(10) In order to avoid a short circuit, the disc stack 11 is insulated to the inner wall of the separator drum 1, here by one or more non-conductive material layers 16, 17 above and below the disc stack 11. The distributor 7 is also insulated by an upper material layer 17 and a lower material layer 21.

(11) In addition, the lower part of the drum 20 can also be insulated from the rotating spindle 2 by an electrically non-conductive material layer 22.

(12) The product feed pipe 5 and the distributor 7 are preferably made of an electrically non-conductive material or have a non-conductive coating, so that the parts, which are preferably already charged before entering the drum, do not settle or discharge on the components already here.

(13) In the following, the function of the separator of the FIGURE is explained in more detail by means of a method for processing, in particular for clarifying, a flowable product.

(14) In addition, a pre-treatment according to the type of step a) of claim 1 is carried out. According to a variant of this pre-treatment, before entering the rotating separator drum, the product is first guided past a negatively or positively charged electrode of a DC voltage source, so that the solid particles in the product become electrically charged. This electrode can also be arranged alternatively in the product teed pipe 4 or in the feed pipe 5. However, the solid particles can also be loaded at another point before the product flow enters the disc gap of disc stack 11. A suitable voltage level for such a DC voltage source is in the range between 5000 and 20000 volts.

(15) If charging of the solid particles takes place before the flowable product stream enters the separator, it is advantageous if the product feed pipe 5 and the distributor 7 are made of non-conductive material or are coated with non-conductive material so that separation preferably takes place only in the disc stack.

(16) After the product enters drum 1, it enters the disc gap of disc stack 11. The charge of the particles of the product is opposite to the charge of the discs, so that the discs exert an electrostatic attraction on the charged particles, which increasingly collect on the discs. The disc gaps therefore become increasingly narrow over time.

(17) By reversing the polarity or switching off the DC voltage source 14, the collected particles, in particular the solid particles, are then repelled from the disc surface and transported into the solids collection chamber 8 (preferably with interrupted feed).

(18) As already explained, the disc stack will become clogged with time. It is therefore advantageous if this is suitably monitored during operation (e.g., on the basis of the feed quantity or the discharge quantity) and if, depending on the monitoring—or periodically at specified intervals—the polarity of the disc stack is reversed and, optionally, the drum is emptied in order to flush out the deposited particles. For this purpose, the DC voltage source is preferably connected to the control and regulation system of the centrifuge (not shown here).

(19) The FIGURE shows a separator which enables a solid-liquid separation. However, the process can also be applied analogously to three-phase separators. As an alternative to the design of a separator in which separator drum 1 is mounted on a rotating spindle 2, the separation of solids on a charged disc stack can be used in other designs, e.g., with suspended drums.

(20) The method and centrifuge according to the invention are suitable for a wide variety of products, but especially for cleaning a contaminated oil.

(21) It should also be noted that the design as a hermetically sealed machine with a rotating feed pipe and a guiding pump element, in which the product is pumped through the machine, is preferred but not mandatory.

LIST OF REFERENCE CHARACTERS

(22) 1 Separator drum 2 Turning spindle 4 Product feed 5 Product feed pipe 6 Fastening means 7 Distributor 8 Solids collection chamber 9 Piston slide 10 Solids discharge opening 11 Disc stack 12 Pump element 13 Product outlet 14 DC voltage source 15a, b Power lines 16 Non-conductive material layers 17 Non-conductive material layers 18 Outer wall of separator drum 19 Outer wall of pump element 20 Lower part of the drum 21 Non-conductive material layers 22 Non-conductive material layers D Axis of rotation SP Solid phase LP Liquid phase P Product