DE102023116565A1 - solid bowl screw centrifuge - Google Patents

Abstract

A solid bowl screw centrifuge for processing a suspension Su in a centrifugal field with a housing (100) and a rotor (200) rotatably mounted in the housing (100), which has at least the following: a rotatable drum (210) with a rotation axis D, the drum (210) having a cylindrical section (211) and a conical section (212), a screw (230) arranged in the drum (210) which can be rotated at a differential speed relative to the rotatable drum (210), an inlet pipe (217) projecting into the drum (210) and arranged concentrically to the rotation axis D, through which the suspension Su to be processed can be guided into a separation space (219) of the drum (210), at least one liquid outlet (214) which is arranged in the cylindrical section (211) of the drum (210), at least one solids discharge (218) which is arranged in the conical section (212) of the drum (210) and which is arranged in the center or close to the center of the drum (210) and the solid Fe leaves the drum (210) in the axial direction or substantially in the axial direction with respect to the drum (210), wherein the inlet side of a pump (400) is attached to the solid discharge (218), which is designed such that a counterpressure can be influenced by controlling the pump on the flow side upstream of the pump or in the drum (210).

Description

The invention relates to a solid bowl screw centrifuge according to the preamble of claim 1.

A solid bowl screw centrifuge (also called a decanter) can be used to separate a solid phase from a suspension. Optionally, the suspension clarified of solids in this way can be separated into different liquid phases in a design with two liquid outlets. Solid bowl screw centrifuges are very well suited to processing relatively high solid concentrations in the feed stream, are relatively robust, achieve a very good separation result and ensure good drying of the solids.

In this context, solids are understood to mean solids that have been dehydrated as much as possible, but in practice they often still contain so much residual moisture that they behave like sludge.

Known solid bowl screw centrifuges with a frame that is not rotatable or does not rotate during operation have a rotor that is rotatable relative to the frame or rotates during operation, which in turn has a rotatable drum and a screw that can rotate therein at a speed different to that of the drum. To discharge the solids, essentially radially aligned solids discharge openings are generally provided in a conical section of the drum.

If the energy loss caused by the discharge of solids or sludge from the bowl of the solid bowl screw centrifuge is to be as small as possible, the radius on which the solids discharge openings are located in the drying zone or in the conical section of the bowl must also be as small as possible.

If a solid bowl screw centrifuge is to be operated in such a way that the so-called pond depth - this results from the difference between the inner diameter of the drum and the diameter of the liquid weir to which the suspension in the drum extends - is as large as possible, this requires the solids to be discharged as close to the axis of rotation as possible. For this purpose, the radius on which the solids discharge openings are located in the dry zone or in the conical section of the drum must be as small as possible. A solid bowl screw centrifuge designed advantageously in this direction is used in the DE 10 2019 126 325 A1 described.

It is also desirable to be able to change the position of the separation zone within the separation chamber while minimizing energy loss during solids discharge, so that the solids leave the drum “drier” or “wetter” as required.

The invention has the object of creating a solid bowl screw centrifuge that essentially meets the above requirements.

The invention solves this problem by the subject matter of claim 1.

• - eine drehbare Trommel mit Drehachse D, wobei die Trommel einen zylindrischen Abschnitt und einen konischen Abschnitt aufweist,
• - eine relativ zur drehbaren Trommel mit einer Differenzdrehzahl drehbare, in der Trommel angeordnete Schnecke,
• - ein in die Trommel ragendes, konzentrisch zur Drehachse D angeordnetes Zulaufrohr, durch das die zu verarbeitende Suspension Su in einen Trennraum der Trommel leitbar ist,
• - mindestens einen Flüssigkeitsablauf, der im zylindrischen Abschnitt der Trommel angeordnet ist und
• - mindestens einen Feststoffaustrag, der in Verlängerung des konischen Abschnitts der Trommel angeordnet ist und der im Zentrum oder nahe des Zentrums der Trommel angeordnet ist, so dass der Feststoff Fe die Trommel in axialer Richtung oder im Wesentlichen in axialer Richtung in Bezug auf die Trommel verlässt, wobei an dem Feststoffaustrag die Zulaufseite einer Pumpe angebracht ist, die derart ausgelegt ist, dass durch ein Ansteuern der Pumpe strömungsseitig vor der Pumpe bzw in der Trommel ein Gegendruck beeinflussbar ist.

Accordingly, a solid bowl screw centrifuge for processing a suspension Su in a centrifugal field is provided with a housing and a rotor rotatably mounted in the housing, which has at least the following:

• - a rotatable drum with axis of rotation D, the drum having a cylindrical section and a conical section,
• - a screw arranged in the drum which can rotate relative to the rotating drum at a differential speed,
• - an inlet pipe extending into the drum and arranged concentrically to the axis of rotation D, through which the suspension Su to be processed can be fed into a separation chamber of the drum,
• - at least one liquid outlet arranged in the cylindrical portion of the drum and
• - at least one solids discharge which is arranged in extension of the conical section of the drum and which is arranged in the center or close to the center of the drum, so that the solid Fe leaves the drum in the axial direction or substantially in the axial direction with respect to the drum, wherein the inlet side of a pump is attached to the solids discharge, which is designed in such a way that a counterpressure can be influenced by controlling the pump on the flow side upstream of the pump or in the drum.

In this way, simple design means create a very good opportunity to easily change the position of the separation zone within the separation chamber while minimizing energy loss during solids discharge, so that the solids can leave the drum “drier” or “wetter” as required.

In a particularly preferred embodiment of the invention it is provided that the solids discharge does not rotate with the drum when the solid bowl screw centrifuge is in operation. This means that the solids discharge can be connected to the downstream lines or a pump in a structurally simple manner and without great effort in terms of production technology.

According to a further, particularly preferred embodiment of the invention, the solids discharge is in fluid communication with one or more openings in the drum. This creates a solids discharge that is easy to produce.

In another particularly preferred embodiment of the invention, the solids discharge is in turn connected to the rotating rotor via a sliding seal. This means that the pump at the solids discharge is kinematically decoupled from the rotary movement of the rotor in a structurally simple manner and the solids flow is pressure-tightly sealed against the environment.

Furthermore, in another particularly preferred embodiment of the invention, the solids discharge is continued as a pipe in the extension of the conical section of the drum, coaxial to the axis of rotation D of the drum. This provides a simple possibility for forwarding the solids flow outside the solid bowl screw centrifuge and thus an optimal installation location for the pump.

Furthermore, in another particularly preferred embodiment of the invention, the pump is a positive displacement pump. As a result, the pump is advantageously designed to be robust with regard to the fluid to be pumped - namely the solid phase - and is self-priming with regard to its flow dynamic properties.

According to a further, particularly preferred embodiment of the invention, it is appropriately provided that the pump is an eccentric screw pump or a rotary piston pump.

In another particularly preferred embodiment of the invention, the volume flow rate (volume flow/time) through the solids outlet can be varied by the pump via the pump speed. This advantageously makes it easy to change the position of the separation zone within the separation space.

Another particularly preferred embodiment of the invention also provides that the pump can generate a positive or negative counterpressure in the solids discharge, with the pump being controlled by a control device designed for this purpose. This makes it easy and therefore advantageous to set the solids to leave the drum "drier" or "wetter" as required.

• - Bereitstellen einer Vollmantel-Schneckenzentrifuge nach Anspruch 1 oder einem der vorstehenden Ansprüche;
• - Erhöhen oder Verringern der Volumendurchflussrate des Feststoffs Fe durch die Pumpe durch die Steuerungseinrichtung und damit einhergehend Beeinflussen des Gegendrucks in der Trommel, wodurch die Position der Trennzone in der Trommel beeinflusst wird.

The object is also achieved by the method according to claim 11, which is characterized by the following method steps:

• - Providing a solid bowl screw centrifuge according to claim 1 or any preceding claim;
• - Increasing or decreasing the volume flow rate of the solid Fe through the pump by the control device and thereby influencing the back pressure in the drum, thereby influencing the position of the separation zone in the drum.

This method perfectly complements the device according to the invention in order to achieve a change in the position of the separation zone within the separation chamber with the lowest possible energy loss during the solids discharge, so that the solids leave the drum "drier" or "wetter" as required.

Further advantageous embodiments of the invention can be found in the subclaims.

• 1: eine schematische Ansicht im Schnitt eines Rotors einer erfindungsgemäßen Vollmantel-Schneckenzentrifuge mit horizontaler Drehachse;
• 2: eine schematische Ansicht im Schnitt eines Rotors einer Vollmantel-Schneckenzentrifuge nach dem Stand der Technik.

The invention is described in more detail below with reference to the drawings using exemplary embodiments. Features that are described in connection with these exemplary embodiments can also be used in other - not shown - exemplary embodiments of the invention and can therefore also be used as features for claims. They show:

• 1 : a schematic sectional view of a rotor of a solid bowl screw centrifuge according to the invention with a horizontal axis of rotation;
• 2 : a schematic sectional view of a rotor of a solid bowl screw centrifuge according to the state of the art.

In the following description of the figures, one or more embodiments of a solid bowl screw centrifuge are described. The individual features of these embodiments can also be combined with embodiments not shown and are also suitable as advantageous embodiments of the objects described in one or more of the main and subclaims.

First, the construction of the 2 described in 1 is further developed according to the invention.

2 shows a solid bowl screw centrifuge with a frame 100 that is not rotatable or does not rotate during operation - which can preferably be designed as a type of housing - and a rotor 200 that is rotatable or rotates during operation.

The rotor 200 has a rotatable drum 210 with a horizontal axis of rotation D. The axis of rotation D can also be oriented differently in space, in particular vertically. The rotor 200 also includes a screw 230 arranged in the drum 210, the axis of rotation of which coincides with the axis of rotation D of the drum 210.

The drum 210 has a cylindrical section 211 and a conical section 212 axially adjoining thereto. The cylindrical section 211 is closed off here by a substantially radially extending drum cover 213. In the conical section 212, the drum 210 is preferably conical on the inside and outside (relative to the drum shell).

The screw 230 here also has a cylindrical section 231 and a conical section 232 axially adjoining thereto. It is arranged inside the drum 210. During operation, the screw 230 can be rotated at a speed different from that of the drum 210.

The worm 230 has a worm spiral 233 and a worm hub 234. The worm 230 is preferably designed in one piece, but it can also be assembled from the worm hub 232 and the worm spiral 231.

The screw flights 233 can have a progressive or degressive pitch. The pitch can be linear or have areas with different pitches. Depending on the pitch direction of the screw flight 233, the screw 230 rotates in the same direction as or opposite to the direction of rotation of the drum.

An inlet pipe 214 extends into the drum 210, which runs concentrically to the axis of rotation D and opens into a distributor 215 through which a suspension Su to be processed can be guided radially into a separation chamber 216 of the drum 210. The inlet pipe 214 can either be guided into the drum 210 from the side of the cylindrical drum section 211 or it can be guided into the drum 210 from the side of the conical drum section 212.

One or more liquid outlets 217 can be formed in or on the drum cover 213. These can be formed in various ways, such as as openings in the drum cover 213, which have a type of overflow weir or in another way, such as as a peeling disk.

At the end of the conical section 212, at least one solids discharge 218 is formed.

The drum 210 is designed as a solid-shell drum. In the rotating drum 210, at least one liquid phase FI is clarified from solids Fe. The at least one liquid phase FI exits the liquid outlet 217 at the drum cover 213. The solids Fe, on the other hand, are transported by the screw 230 in the direction of the solids discharge 218 and ejected from the drum 210 there.

A first drum shaft section 219, which is connected in a rotationally fixed manner to the drum 210, can be connected axially to the drum cover 213 or to the actual drum 210, and a second drum shaft section 220, which is also connected in a rotationally fixed manner to the drum 210, can be connected to the conical drum section 212 in the radial direction with respect to the drum 210.

A first worm shaft section 235, which can be connected to the worm 230 in a rotationally fixed manner, is axially connected to the cylindrical section 231 of the worm 230. A worm bearing 236 is placed on the first worm shaft section 235. The conical section 232 of the worm 230 is also supported here. The conical section 232 of the worm 230 has a second worm shaft section 237. A further worm bearing 238 is placed on the second worm shaft section 237.

A drive device 300, which can have one or two motors, is used to drive the rotor 200. At least one gear 310 can be connected downstream of the drive device 300, on which two pulleys 320, 330 are shown schematically here, which indicates that the gear 310 can have at least two interfaces for feeding a respective torque of the motor or motors into the gear 310 in order to drive the drum 210 and the worm 230. Alternatively (not shown here), the rotor 200 can also be driven in another way.

The gear 310 rotates 2 (and preferably also according to the invention) on the one hand the drum 210 and on the other hand the screw 230.

The drum 210 can be rotatably mounted with two drum bearings 221, 222 arranged axially offset in the direction of the axis of rotation.

The drum bearings 221, 222 can advantageously be arranged between the drum 210 and the frame 100 or one or more elements connected to the frame 100 so that the drum 210 can be rotated relative to the frame 100.

The worm bearings 236, 238, however, can be arranged radially between the worm 230 and the drum 210, so that the worm 230 can be rotatable relative to the drum 210.

The term "bearing" should not be interpreted too narrowly. Each of the bearings 221, 222, 236, 238 can consist of one or more individual bearings, which are then arranged axially directly next to one another, so that they can each be considered functionally as an individual bearing.

In a possible design variant (not shown), one of the screw bearings 238 in the area of the solids discharge 218 can be omitted. This can be provided, for example, in a vertical arrangement of the solid bowl screw centrifuge.

The mounting of the drum 210 in or on the frame 100 as well as the mounting of the screw 230 in the drum 210 can also be designed differently than shown.

In a preferred embodiment, the above features can also be used for the solid bowl screw centrifuge of 1 as well as other variants of the invention. In these, however, the solids discharge 218 in particular is designed in a different way.

The solids discharge 218 is arranged in the center or near the center of the drum 210. The solids discharge 218 is arranged in the solid bowl screw centrifuge in 1 in fluid communication with one or more solid discharge openings 223 in the drum 210. Preferably, the one or more solid discharge openings 223 are aligned axially or substantially in the axial direction with respect to the drum 210, in other words aligned coaxially with the axis of rotation D of the drum 210. This advantageously reduces shear forces that arise when the solid Fe exits the drum 210.

When designing the solid bowl screw centrifuge according to 1 the solids discharge 218 is connected to the rotor 200 via a sliding seal 224. In this way, the solids Fe to be discharged is guided through the solids discharge openings 223, which rotate with the drum 210 during operation of the solid bowl screw centrifuge, at the axial end of the rotating drum 210 via the seal 224 into a non-rotating solids discharge (section) 218, which is arranged here as an axial extension of the drum 210. It can - as shown here by way of example - be designed like a pipeline and have a conical section and an adjoining cylindrical section. This solids discharge section 218 is connected to the inlet side of a pump 400. This pump 400 is preferably a positive displacement pump, particularly preferably an eccentric screw pump or a rotary piston pump, in which the volume flow rate through the solids outlet 218 can be varied via the pump speed.

If the volume flow rate through the pump 400 is less than the unaffected volume flow rate of the solid Fe solely by the transport of the screw 230, then the pump 400 generates a positive back pressure in the drum 210. If the volume flow rate through the pump 400 is greater than the unaffected volume flow rate of the solid Fe solely by the transport of the screw 230, then the pump 400 generates a negative back pressure in the drum 210.

The pump 400 is thus designed in such a way that, by appropriately controlling - depending on the requirement - a counterpressure can be influenced on the flow side in front of the pump or in the drum 210. The pump 400 is controlled by a control device designed for this purpose (not shown here). The control device acts on corresponding actuators that influence the speed of the pump 400, such as a frequency converter, which in turn acts on the pump motor. This control device can also be integrated into the control of the solid bowl screw centrifuge.

By varying the counter pressure in the solids discharge, the position of the separation zone in the solid bowl screw centrifuge can be easily and advantageously changed almost continuously and thus the moisture content of the ejected solid Fe can be optimally adjusted depending on the requirements.

If the pump 400 generates a positive counterpressure in the solids discharge 218, the position of the separation zone changes in the direction of the liquid outlet 217. The solid Fe therefore leaves the drum 210 drier.

If a negative counterpressure is generated in the solids discharge 218 by the pump 400, the position of the separation zone changes in the direction of the solids discharge 218. The solid Fe therefore leaves the drum 218 moister.

• In einem ersten Verfahrensschritt wird eine Vollmantel-Schneckenzentrifuge nach Anspruch 1 oder einem der vorstehenden Ansprüche bereitgestellt.

The following procedure is specified for influencing a separation zone between two defined positions in the drum 210 of a solid bowl screw centrifuge:

• In a first method step, a solid bowl screw centrifuge according to claim 1 or one of the preceding claims is provided.

In a subsequent process step, the volume flow rate of the solid Fe through the pump is increased or decreased by the control device and thus the back pressure in the drum, thereby influencing the position of the separation zone in the drum.

This creates a simple process for changing the position of the separation zone within the separation chamber with as little energy loss as possible during solids discharge, so that the solids or sludge leaves the drum “drier” or “wetter” as required.

list of reference symbols

100

frame

200

rotor

210

drum

211

cylindrical section

212

conical section

213

drum lid

214

inlet pipe

215

distributor

216

separation space

217

fluid drainage

218

solids discharge

219

drum shaft section

220

drum shaft section

221

drum bearings

222

drum bearings

223

solids outlet opening

224

seal

230

Snail

231

cylindrical section

232

conical section

233

screw flight

234

worm hub

235

worm shaft section

236

worm bearings

237

worm shaft section

238

worm bearings

300

drive system

310

transmission

320

pulley

330

pulley

400

pump

D

axis of rotation

Su

suspension

Fe

solids

FI

liquid phase

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 10 2019 126 325 A1 [0006]

Claims (11)

Solid bowl screw centrifuge for processing a suspension Su in a centrifugal field with a housing (100) and a rotor (200) rotatably mounted in the housing (100), which has at least the following: a) a rotatable drum (210) with an axis of rotation D, the drum (210) having a cylindrical section (211) and a conical section (212), b) a screw (230) arranged in the drum (210) and rotatable at a differential speed relative to the rotatable drum (210), c) an inlet pipe (217) projecting into the drum (210) and arranged concentrically to the axis of rotation D, through which the suspension Su to be processed can be guided into a separation space (219) of the drum (210), d) at least one liquid outlet (214) arranged in the cylindrical section (211) of the drum (210), e) at least one solids discharge (218) which is arranged in extension of the conical section (212) of the drum (210) and which is arranged in the center or close to the center of the drum (210) and the solid Fe leaves the drum (210) in the axial direction or substantially in the axial direction with respect to the drum (210), characterized in that f) the inlet side of a pump (400) is attached to the solids discharge (218), which is designed in such a way that a counterpressure can be influenced by controlling the pump on the flow side upstream of the pump or in the drum (210). Solid bowl screw centrifuge according to claim 1 , characterized in that the solids outlet (218) does not rotate with the drum (210) during operation of the solid bowl screw centrifuge. Solid bowl screw centrifuge according to claim 1 or 2 , characterized in that the solids discharge (218) is in fluid communication with one or more solids discharge openings (223) in the drum (210). Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the solids discharge (218) is connected to the rotor (200) via a sliding seal (224). Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the solids discharge (218) is continued as a pipe coaxial to the axis of rotation D of the drum (210) in an extension of the conical section (212) of the drum (210). Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the pump (400) is a positive displacement pump. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the pump (400) is an eccentric screw pump or a rotary piston pump. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the volume flow rate through the solids outlet (218) can be varied by the pump (400) via the pump speed. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that a positive or a negative counterpressure can be generated in the solids outlet (218) by the pump (400). Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the pump (400) is controlled by a control device designed for this purpose. Method for influencing a separation zone between two defined positions in the drum (210) of a solid bowl screw centrifuge, characterized by the following method steps: a) providing a solid bowl screw centrifuge according to one of the preceding Claims 1 until 10 ; b) increasing or decreasing the volume flow rate of the solid Fe through the pump (400) by the control device and thereby influencing the back pressure in the drum (210), thereby influencing the position of the separation zone in the drum (210).

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