EP3700678B1 - Method for processing a flowable product and centrifuge - Google Patents

Description

The invention relates to a method for processing a free-flowing product according to the preamble of claim 1 and a centrifuge, in particular a separator, according to the preamble of claim 8.

The DE 10 2006 022 156 A1 discloses a method and a device for the treatment of liquids, in which an inflowing free-flowing product is separated in a centrifuge into two liquid phases and a solid phase. For this purpose, the product, for example a contaminated lubricating oil, is separated into two partial streams, which are guided past a positive and a negative electrode. The particles contained in the first partial flow are positively charged and the particles of the second partial flow are negatively charged. Before the liquid is introduced into the centrifuge, both partial flows are combined in a collection tank, with the positively charged particles and the negatively charged particles conglomerating into larger particle aggregates due to the mutual electrostatic attraction. These conglomerates are then easier to separate from the liquid in a centrifugal field.

The SU 5 51 036 discloses a centrifuge that enables electrostatic charging of particles within a discontinuous centrifuge. For this purpose, an electrode is arranged in an inlet chamber on the axis of rotation of the centrifuge. After the particles have been electrostatically charged, they are passed on to a drum room, in which the particles are separated into solids collection bags. The clarified liquid is then discharged from the centrifuge. The solids collection pockets are embedded in the wall of the centrifuge. In contrast to a conventional centrifuge with a disk pack, however, continuous operation is not possible with this centrifuge, since the collection bags have to be emptied at regular intervals.

• Vorbehandeln des fließfähigen Produktes, so dass Teilchen in diesem Produkt verstärkt durch elektrisch aufgeladene Bauteile angezogen werden;
• Zuleiten des fließfähigen Produktes in das Tellerpaket;
• Aufladen der Teller des Tellerpakets; und
• Abscheiden der aufgeladenen Teilchen aus dem fließfähigen Produkt innerhalb des Tellerpakets, und
• Abführen der Feststoffphase kontinuierlich über die Feststoffaustragsöffnungen aus der Separatortrommel.

The U.S. 1,558,382 A discloses a method for processing a free-flowing product with a centrifuge, in particular a separator, with a vertical axis of rotation with a preferably continuously operating rotating centrifuge drum, in which a disk pack is arranged, at least one product outlet for discharging at least one liquid phase and at least one Solids discharge opening for discharging a solid phase, which has the following steps:

• pretreating the flowable product so that particles in this product are more attracted to electrically charged components;
• Feeding the free-flowing product into the plate pack;
• loading the plates of the plate pack; and
• separating the charged particles from the flowable product within the disk pack, and
• The solid phase is discharged continuously from the separator drum via the solid discharge openings.

Extensively analogous solutions reveal the JP H03 143560 A and the JP H02 78454 A .

It is the object of the present invention, starting from the prior art, to create a method for processing a flowable product and to provide a centrifuge which enables an alternative solution for a better separation of particles.

The invention solves this problem by a method having the features of claim 1 and a centrifuge having the features of claim 8.

1. a) Vorbehandeln des fließfähigen Produktes, so dass Teilchen in diesem Produkt verstärkt durch elektrisch aufgeladene Bauteile angezogen werden;
2. b) Zuleiten des fließfähigen Produktes zu dem Tellerpaket;
3. c) Erzeugen einer elektrischen Ladung auf den Tellern des Tellerpakets und
4. d) Abscheiden der aufgeladenen Teilchen aus dem fließfähigen Produkt innerhalb des Tellerpakets (und somit unter Einfluss von elektrostatischen Anziehungskräften und eines Zentrifugalfeldes)und
5. e) Abführen der Feststoffphase SP diskontinuierlich in radialer Richtung über die Feststoffaustragsöffnungen aus der Separatortrommel, welche über einen Kolbenschieber geöffnet und geschlosser werden können.

According to the invention, a method for processing a flowable product with a centrifuge, in particular a separator with a vertical axis of rotation, with a rotatable centrifuge drum in which a disk pack, at least one product outlet and at least one solids discharge opening are arranged, has the following steps:

1. a) pre-treating the flowable product so that particles in this product are attracted to electrically charged components to a greater extent;
2. b) feeding the free-flowing product to the plate pack;
3. c) Generation of an electrical charge on the plates of the plate pack and
4. d) separating the charged particles from the flowable product within the disk pack (and thus under the influence of electrostatic attractive forces and a centrifugal field) and
5. e) discharge of the solid phase SP discontinuously in the radial direction via the solid discharge openings from the separator drum, which can be opened and closed via a piston valve.

Through the targeted use of electrostatic forces in the disc gaps in the centrifugal field of a centrifuge, a better separation behavior of particles on the discs of the disc pack is easily achieved. In addition, the particles that have already been separated stick to the underside of the discs, so that the particle and product feed streams are prevented from crossing at the outer diameter of the discs, and thus also that particles that have already been separated can get into the disc pack a second (or third, ...) time.

Advantageous refinements of the method according to the invention are the subject matter of the dependent claims.

In order to enable the effect of the electrically charged plates on the charged particles over a large area, it is advantageous if this is generated on the plates of the plate stack by a surface charge.

The electric field between the plates of the plate pack and the remaining part of the centrifuge insulated therefrom is particularly preferably generated by impressing a charge from a DC voltage source.

In this case, the positive or negative charge can be transferred from the outside to a component of the centrifuge, with one pole of the DC voltage source being in contact with an outer wall of this component and this component being made of electrically conductive material. After the charge has been transferred, this charge is passed on or transferred to the disk pack of the centrifuge.

The pre-treatment of step a) preferably takes place outside the drum. In addition, the pre-treatment is preferably carried out in such a way that the particles are attracted by the charge on the stack of plates.

According to a first advantageous variant of the invention, the pretreatment in step a) can be carried out by electrostatically charging the particles, for example outside the centrifuge. The product to be processed is guided past a positively or negatively charged electrode, with particles, for example solid particles, being charged on the electrode before they enter the centrifuge. This electrode is preferably outside of the drum arranged. However, it is also conceivable to integrate them into the inlet of the drum.

During deposition, these charged particles are increasingly pulled by the electrostatically charged plates towards the plate surface, where they are deposited and then stick.

According to an alternative variant of the invention, the pretreatment in step a) can also be carried out by adding a ferrofluid in order to achieve the above-mentioned effect in this way.

After the particles have been separated in step d), the electrical field on the stack of plates can advantageously be switched off and/or discharged, so that the separated particles slide off the surface of the plate more easily into the solids space.

During polarity reversal or when the electric field is switched off, the degree of separation decreases by a few percent. In order to advantageously avoid unnecessary polarity reversal or switching off, the separation can be monitored, for example by a probe at a product outlet of the liquid phase or liquid phase. If the proportion of solids exceeds a specified value, the separation on the plate is insufficient. By monitoring the deposition, the process can be adapted to the respective product.

Alternatively, the inlet can be closed during the polarity reversal or switching off of the electric field.

According to the invention, a centrifuge, in particular a separator, has a centrifuge drum, in particular a continuously operable separator drum with a vertical axis of rotation, in which a disk pack is arranged, the centrifuge drum having at least one product inlet for feeding in a product to be processed, a disk pack for phase separation and at least one outlet for discharging a liquid phase and an outlet for discharging at least one further phase, in particular a liquid phase or a solid phase. The centrifuge also has at least one means for generating an electrical charge on the plates of the plate pack or in the plate gaps of the plate pack. The solid phase is discharged discontinuously in the radial direction via solid discharge openings from the separator drum, which can be opened and closed via a piston valve

In the case of a separator with electrostatically charged plates, particles are separated in the area of a centrifuge, on which separation also usually takes place without the additional influence of electrostatics. When a product containing charged particles is processed with the centrifuge, the separation rate of these charged particles is improved and the already separated particles are prevented from crossing the product feed stream.

Advantageous configurations of the centrifuge according to the invention are the subject matter of the dependent claims.

A suitable DC voltage source can be used to generate an electrical charge on the plates of a plate stack, with the level of the generated voltage preferably being adjustable. In this case, there is a positive pole at one point on the separator and a negative pole at another point on the separator. One of the poles is conductively connected to the plate stack. The stack of plates is electrically insulated from the outer wall of the centrifuge drum by a coating or other non-conductive material, so that contact between the two components cannot lead to a short circuit.

A suitable voltage level for such a DC voltage source is in the range between 5000 and 20000 volts.

In order to enable simple operability, the means for generating an electrical charge on the plates of the plate pack is preferably arranged outside of the centrifuge drum.

In an advantageous embodiment, a first pole of the DC voltage source with a positive or negative charge can be arranged on the outer wall of a pump element of the centrifuge, which is connected to the plate stack. To do this, the pole only has to be attached to the pump element, further structural adjustments to the centrifuge drum are not necessary. This is an advantage because it means that an existing centrifuge can also be retrofitted.

The invention is described in more detail below using an exemplary embodiment and a drawing. It shows:
Fig.1 a sectional partial view of a separator drum in hermetically sealed design.

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

The rotary spindle 2 has a conical shape along an upper peripheral area and is fastened to the lower drum part 20 with a fastening means 6 .

A product feed pipe 5 , which rotates during operation and is aligned concentrically to the axis of rotation D, is connected to a product feed 4 . The product P runs from the product feed pipe 5 into a distributor 7 with distributor bores or ribs, from which the free-flowing 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 direct the product from the distributor into at least one riser channel in the plate stack.

Inside the separator drum 1, the inflowing product flows into disc gaps between conical discs of a disc pack 11, spaced apart axially by means of spacers.

The product is clarified in the plate gaps (and possibly also separated into two or more liquid phases), in that solid particles of the free-flowing product are deposited on the underside of the plates, which can escape from there into a solids collection space 8 . From there, the solid phase SP is discharged discontinuously in the radial direction via solid discharge openings 10 from the separator bowl 1, which can be opened and closed by a piston valve 9. The liquid phase LP is conducted to a pump element 12 and discharged from there through a product outlet 13 .

A better separation of solid particles in the plate gaps of a plate pack is made possible in the present case by applying an electrical charge to the plate pack 11 . This also means that particles that have already been separated stick to the underside of the plate.

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 electrical line 15a or 15b.

A component that is easily accessible from the outside, here the outer wall 19 of the pump element 12, consists of an electrically conductive material and is conductively connected to the disk pack, 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, has the opposite polarity.

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

In addition to this, the lower drum part 20 can also be insulated from the rotary spindle 2 by an electrically non-conductive material layer 22 .

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 already settle on the components or discharge here.

The following describes how the separator works 1 explained in more detail using a process for processing, in particular for clarification, of a free-flowing product.

In addition, there is a pretreatment in the manner of step a) of claim 1. According to a variant of this pretreatment, the product is first guided past a negatively or positively charged electrode of a DC voltage source before entering the rotating separator drum, so that the solid particles in the product are electrically charge. Alternatively, this electrode can also be arranged in the product inlet 4 or in the inlet pipe 5 . However, the loading of the solid particles can also take place elsewhere before the product flow enters the disc gap of the disc stack 11 . A suitable one The voltage level for such a DC voltage source is in the range between 5000 and 20000 volts.

If the solid particles are charged before the free-flowing 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 the separation preferably only takes place in the plate stack.

After the product has entered the drum 1, it enters the disc gaps of the pack of discs 11. The charge on the particles of the product is opposite to the charge on the plates, so that the plate exerts an electrostatic attraction on the charged particles, which increasingly collect on the plates. The plate gaps therefore continue to clog over time.

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

As already explained, the plate stack clogs over time. It is therefore advantageous if this is suitably monitored during operation (e.g. based on the inflow volume or the outflow volume) and if, depending on the monitoring - or periodically at specified time intervals - the polarity of the disk stack is reversed and the drum is emptied, if necessary, in order to to rinse out the attached particles. For this purpose, the DC voltage source is preferably connected to the control and regulation system of the centrifuge (not shown here).

In Fig.1 a separator is shown, which enables solid-liquid separation. However, the method can also be applied analogously to three-phase separators. As an alternative to the design of a separator, in which the separator drum 1 is placed on a rotating spindle 2, the separation of solids on a charged plate stack can be used in other designs, for example with hanging drums.

The method according to the invention and the centrifuge are suitable for a wide variety of products, but in particular for cleaning a contaminated oil.

It should also be noted that although the design as a hermetically sealed machine with a rotating inlet pipe and a guiding pump element, in which the product is pumped through the machine, is preferred, it is not mandatory.

Reference List

1

separator drum

2

turning spindle

4

product feed

5

product inlet pipe

6

fasteners

7

distributor

8th

solids collection space

9

piston slider

10

solids discharge opening

11

plate pack

12

pump element

13

product expiration

14

DC voltage source

15a, b

power lines

16

non-conductive material layers

17

non-conductive material layers

18

Outer wall separator drum

19

outer wall of the pump element

20

drum base

21

non-conductive material layers

22

non-conductive material layers

D

axis of rotation

SP

solid phase

LP

liquid phase

P

product

Claims (15)

1. Method for processing a flowable product (P) using a centrifuge, in particular a separator, having a vertical axis of rotation (D) with a preferably continuously operating rotatable separator drum (1) in which a disc stack (11) is arranged, at least one product outlet (13) for discharging at least one liquid phase (LP) and at least one solids discharge opening (10) for discharging a solid phase (SP), characterized by the following steps:

   a) pretreating the flowable product (P) so that particles in this product are increasingly attracted by electrically charged components;

   b) feeding the flowable product (P) into the disc stack (11);

   c) charging the discs of the disc stack (11); and

   d) separating the charged particles from the flowable product (P) within the disc stack (11), and

   discharge of the solid phase SP discontinuously in the radial direction via the solid discharge openings (10) from the separator drum (1), which can be opened and closed by a piston slide (9).
2. Method according to claim 1, characterized in that the generation of the electrical charge on the disc stack (11) is effected by applying a pole of a DC voltage source (14) directly to the disc stack (11) or to a part of the separator drum (1) conductively connected to the disc stack.
3. Method according to claim 2, characterized in that the disc stack (11) is charged or polarized in the opposite direction to the charge of the particles of the product.
4. Method according to one of the preceding claims, characterized in that the disc stack (11) is reversed in polarity or disconnected from the DC voltage source.
5. Method according to claim 4, characterized in that the reversal or switching off of the electric field takes place periodically in time or as a function of the clarification behavior in the disc stack (11).
6. Method according to one of the preceding claims, characterized in that the pretreatment of step a) is carried out by electrically charging particles of the flowable product (P).
7. Method according to one of the preceding claims, characterized in that the pretreatment in step a) is carried out before the product is introduced into the rotating drum (11).
8. Centrifuge, in particular separator with a separator drum, in particular a separator drum (1) having a vertical axis of rotation (D) in which a disc stack (11) is arranged, wherein the separator drum (1) has at least one product feed pipe (5) for feeding a product to be processed, a disc stack (11) for phase separation and at least one outlet (13) for discharging a liquid phase and an outlet (10) for discharging at least one further phase, in particular a liquid phase or a solid phase, wherein the centrifuge is designed to carry an electric charge on the discs of the disc stack (11), characterized in that the solid phase SP is discharged discontinuously in the radial direction via solid discharge openings (10) from the separator drum (1), which can be opened and closed via a piston slide (9).
9. Centrifuge according to claim 8, characterized in that an electric charge is applied to the discs of a disc stack with the aid of a direct voltage source (14).
10. Centrifuge according to one of the preceding claims 8 or 9, characterized in that the disc stack (11) is electrically insulated by means of insulating layers (16, 17) from the distributor (7) and the inner wall of the separator drum (1).
11. Centrifuge according to one of the preceding claims 8 to 10, characterized in that a product feed pipe (5) adjacent to the product feed (4), a rotary spindle attachment (6), a rotary spindle (2) and/or a rotary spindle mount are made of an electrically non-conductive material or are coated with an electrically non-conductive material (21, 22).
12. Centrifuge according to one of the preceding claims 8 to 11, characterized in that the means for generating an electric charge on the discs of the disc stack (11) is arranged outside the separator drum (1).
13. Centrifuge according to one of the preceding claims 8 to 12, characterized in that a first pole of the DC voltage source (14) is connected to a component of the centrifuge which is conductively connected to the disc stack (11).
14. Centrifuge according to claim 13, characterized in that the second pole of the DC voltage source (14) is connected to a drum part which is electrically non-conductively connected to the disc stack.
15. Centrifuge according to claim 14, characterized in that it is designed as a hermetically sealed construction.

Images