WO2016114663A1

WO2016114663A1 - Centrifugal separator

Info

Publication number: WO2016114663A1
Application number: PCT/NL2016/050032
Authority: WO
Inventors: Hendrik Arie Boele
Original assignee: Evodos B.V.
Priority date: 2015-01-13
Filing date: 2016-01-13
Publication date: 2016-07-21
Also published as: NL2014129A; EP3245004B1; EP3245004A1; NL2014129B1

Abstract

A centrifugal separator comprising a rotatably arranged upwardly extending first element (2) with elongate elements connected thereto and an upwardly extending rotatably arranged second element (3), wherein the first element and the second element are approximately concentrically arranged with respect to each other around an upwardly extending rotation axis resulting in an inner element (4) and an outer element (5) providing a separation chamber (6) therebetween, wherein the outer element is removable with respect to the inner element and wherein the elongate elements (7) extend from the first element towards the second element, wherein at least a part of the elongate element comprises at least one protrusion (8).

Description

Title: Centrifugal separator The invention relates to a centrifugal separator.

Centrifugal separators are commonly known and are generally used for separating particles or components from a dispersion comprising said particles, such as a slurry. A slurry can be considered as a system in which particles or droplets are mixed with a carrying fluid in a continuous phase of a different composition, e.g. a mud being a slurry comprising clay particles in water, hving algae in water, contaminant particles in lubricant, water in oil, or tar sand comprising oil, or drilling muds comprising solids, etc. A slurry may comprise two or more phases, such as a suspended phase and a continuous phase. The suspended phase may be solid or liquid. The continuous phase is a fluid, viz. a gas or a liquid, usually a hquid. Thus, a slurry can be a fluid carrying one or more solid and/or liquid particles. The particles may be for example sohd particles suspended by the fluid or may be liquid particles suspended by a fluid.

The principle of a centrifugal separator is commonly known. The centrifugal separator creates an artificial field of gravity by using the centrifugal force. Due to the difference in specific density of the different particles in the slurry one or more particles may be separated and collected. For example, a well known separator is the Evodos®-separator described in WO 2009/005355. This separator has found a wide field of use and is being used for the separation of various types of dispersions and/or slurries.

It is noted that the separation process in the above mentioned separator is a batch process. The separation chamber of the separator is filled with the slurry or suspension to be separated, prior and/or during the rotation, depending on the type of separator. In a centrifugal separator of the Evodos®-type, typically the slurry or suspension is fed to the separation chamber during rotation. After rotation is ended, the separation chamber is opened and the solid particles are removed from the separation chamber, which is then cleaned and prepared for the next batch. In plants where a lot of slurry and/or suspension is separated, scaling of the plants can be important. To increase for example the volume, the operator can place a number of centrifugal separators. Alternatively and/or additionally, increasing the scale of the centrifugal separator itself may be chosen for and/or shortening the process time of a batch run may be opted for.

However, scaling of a centrifugal separator imposes a lot of problems, due to the large centrifugal forces and/or artificial field of gravity.

It is an object of the invention to provide for a more robust design of the centrifugal separator that obviates at least one of the above

mentioned drawbacks.

Thereto, the invention provides for a centrifugal separator according to claim 1.

By providing a centrifugal separator of which the elongate elements are provided with at least one protrusion, the elongate elements may become more stiff, and as such may withstand higher centrifugal forces, which may be advantageous for example when scaling up the separator and/or increasing the rpm etc. Advantageously, the protrusion extends in a direction transverse to a surface of the elongate element. The elongate element may be embodied as a plate-like element, so, preferably, the protrusion extends in a direction transverse to the plate. The protrusion may be a ridge, or a bulge, or a bubble, or an impress or many other forms may be possible. The elongate elements are at a distance with respect to each other, so between the elongate elements separation may take place. There is no contact between adjacent elongate elements over a main part of the surface of the elongate elements. Preferably, at the position of a protrusion there is no contact between the protrusion and an adjacent elongate element, so some distance remains between the protrusion and an adjacent elongate element, as to not disturb the flow of the slurry or suspension. This is contrary to prior art separators that have notches or ribs as distance keepers to hold apart the adjacent blades and to maintain the distance between adjacent blades. Thus, in prior art separators, the notches or ribs are in contact with the adjacent blade to keep the adjacent blade at a distance, whereas, according to the invention, there is no contact between the elongate elements, also not at the protrusions.

The first element of the centrifugal separator may be a rotational shaft and the second element may be a tubular sleeve. The rotational shaft and the tubular sleeve may form a drum of the centrifugal separator. The rotational shaft may be approximately centrally positioned in the tubular sleeve, wherein the tubular sleeve may surround the rotational shaft. The tubular sleeve may be a stationary element, thus the first element, the rotational shaft, with the elongate elements may rotate in the second element, the tubular sleeve. However, the second element may also be a rotational element, so the first element, the second element and the elongate elements may rotate together. Preferably, the first element and the second element rotate with the same speed such that during rotation there is approximately no velocity difference between the first element and the second element. In an embodiment, the elongate elements can extend from the first element until the second element and/or can even rest on the second element such that the first element and the second element are mechanically coupled during rotation. The second element can then during rotation be taken along with the first element. Also, the first and the second element can both be driven by the same drive system, or they can each have an own drive system which may be synchronized. By rotating the first element and the second element with the same rotational speed, turbulence of the dispersion and/or friction between separated particles and the tubular sleeve can be minimized. The elongate elements are during rotation supported at the inner side on the rotational shaft and at the outer side on the outer element, the protrusions then provide additional stiffness to the elongate elements during rotation, in particular the bending stiffness may be increased.

The protrusion may be an elongate protrusion that extends over at least a part of the surface of the elongate element, preferably in a direction along the surface of the elongate element from the first element towards the second element. As such, the protrusion is an elongate protrusion extending in a direction transverse to the rotation axis of the centrifugal separator along the surface of the elongate element. Thus, the stiffness of the elongate element may sufficiently increase to also withstand higher centrifugal forces coming with an increased radius of the elongate elements when scaling up the separator.

In particular, it may be advantageous to provide elongate protrusions on the elongate element, i.e. protrusions that extend in a direction from the first element towards the second element along the surface of the elongate element over a part of the surface of the elongate element. As such, the elongate protrusion extends in a direction

substantially transverse to the direction of the rotation axis, as to not to disturb the flow of the suspension or slurry between two elongate elements during the rotation.

In fact, during rotation droplets, liquid and/or solid, of the suspension or slurry to be separated are moved outwardly in a direction from the inner element to the outer element. The droplets are thus slung radially outwardly until they hit on an elongate element. Then, the droplet may follow a path on the elongate element until the droplet reaches a position on the elongate element where the centrifugal force does not move the droplet further. Solid particles may stick to the elongate element, while liquid particles may also move downwardly and may be collected at a bottom of the separation chamber. Preferably, the elongate elements are curved.

Advantageously, the radial distance between two adjacent elongate elements is relatively small, between about 3 mm and about 15 mm, depending on suspension and/or slurry to be separated and/or the volume to be separated. Due to the relatively small radial distance between adjacent elongate elements, the separation efficiency may be increased.

Preferably, the elongate elements are parallel to each other, such that the radial distance between the elongate elements is about the same over the length of the elongate elements. So, a more balanced separator may be obtained. This distance is also present between the elongate elements at the positions of the protrusions. So, the protrusions do not contact with the next elongate element, contrary to prior art separators wherein protrusions are used as distance keepers to maintain the distance between adjacent elongate elements.

Advantageously, two adjacent elongate elements are provided with the same protrusions and/or the same pattern of protrusions, as to keep the radial distance between the adjacent elongate elements the same, also at the positions of the protrusions, such that the space between adjacent elongate elements is the same over the elongate elements.

In an advantageous embodiment, the elongate elements are hingedly connected to the first element, as to allow rotation around the hinge. The hinge then provides for some movement of the elongate element, while the elongate element itself is relatively stiff in order to withstand higher centrifugal forces during the separation run. It is noted however, that upon cleaning of the elongate elements after a separation run, the centrifugal force applied may be higher than during the separation run. So, during the cleaning run, the elongate elements may elastically deform to swing away the particles stuck on them during the separation run. So, the elongate elements may be sufficiently stiff to allow them to withstand higher centrifugal forces, while remaining sufficiently flexible to allow cleaning of the vanes during the cleaning run.

Further advantageous embodiments are represented in the subclaims. The invention will further be elucidated on the basis of exemplary embodiments which are represented in a drawing. The exemplary

embodiments are given by way of non-limitative illustration.

In the drawing:

Fig. 1 shows a schematic perspective view of a centrifugal separator;

Fig. 2a shows a schematic top view of a pack of elongate elements; Fig. 2b shows a detail of two adjacent elongate elements; Fig. 2c shows schematically a detail of two adjacent elongate elements;

Fig. 3 shows a schematic perspective view of two adjacent elongate elements according to an embodiment of the invention; and

Fig. 4 shows four different embodiments of protrusions according to the invention.

It is noted that the figures are only schematic representations of embodiments of the invention that are given by way of non-hmiting example. In the figures, the same or corresponding parts are designated with the same reference numerals.

Figure 1 schematically shows a centrifugal separator 1. The centrifugal separator comprises a rotatably arranged upwardly extending first element 2 and an upwardly extending rotatably arranged second element 3. The first element 2 and the second element 3 are approximately concentrically arranged with respect to each other around an upwardly extending rotation axis A resulting in an inner element 4 and an outer element 5. In this embodiment the first element 2 becomes the inner element 4 and the second element 3 becomes the outer element 5. Between the inner element 4 and the outer element 5, a separation chamber 6 is established. The separation chamber 6 is at a top end 6a closed by a top closing plate 9. At a bottom end 6b is the separation chamber 6 closed by a bottom closing plate 10.

The inner element 2 itself, or alternatively, a tube inside of the inner element 2 may function as a feed tube 11 for feeding the slurry and/or suspension to be separated to the separation chamber 6.

Further, the outer element 5 is removable with respect to the inner element 4. In an embodiment the outer element 5 is axially removable with respect to the inner element 4, for example by moving the outer element 5 upward in a direction parallel to the rotation axis A. In an other embodiment, the outer element 5 may be segmented and each segment or section may be radially moved outwardly.

Elongate elements 7 are connected to the first element 2. The elongate elements 7 are advantageously curved and extend from the first element 2 to the second element 3. The elongate elements 7 may be vanes or plates. The elongate elements 7 may typically be manufactured from steel, e.g. the elongate element may be provided as a curved steel plate. In other embodiments, also depending on the slurry and/or suspension to be separated, other materials may be used, for example aluminum or plastic composite material or even other materials or a combination of various materials, e.g. a composite of metal and plastic material. Many variants are possible. The elongate elements 7 preferably do not contact each other, at least not at a main part and/or central part of a surface of the elongate elements, as to not or minimally disturb the flow of the slurry and/or suspension.

The elongate elements 7 are provided with at least one protrusion 8. The protrusion 8 is here embodied as an elongated ridge extending in a direction from the second element 3 towards the first element 2, i.e. in a direction transverse to the direction of the rotation axis A. The elongated ridge 8 here also extends in a direction approximately transverse to a surface 7a of the plate 7, as can also be seen in Figure 3. Preferably, the elongate elements 7 do not contact each other at least in a central part of the surface 7a of the elongate element 7, also not at a position of a protrusion 8. Also at a position of the protrusions 8, there is some distance between the protrusion 8 and the adjacent elongate element 7.

In use, the slurry and/or suspension to be separated is fed via the feed tube 11 towards the separation chamber 6. The separation process with the centrifugal separator 1 is a batch process. Feeding of the slurry and/or suspension to be separated is typically being done during rotation of the inner element 4 and the vanes 7.

Feeding of the slurry and/or suspension to be separated may be done via feed pipes, or feed holes, or other feeding means. For simplicity's sake, the feeding means are not shown here. The inner element 4 is rotated around the rotation axis A and the vanes 7 connected thereto are also rotated. During rotation, the inner element 4 and the outer element 5 are mechanically coupled via the elongate elements 7 to each other, such that the outer element 5 rotates with the same rotational speed as the inner element 4 and the vanes 7. During rotation, the elongate elements 7 are thus supported at an inner side to the rotational shaft or inner element 4 and at an outer side to the sleeve or outer element 5. During rotation, an artificial field of gravity is created in the separation chamber 6, due to the centrifugal force, and liquid and/or solid particles having a different specific gravity are being moved towards different zones in the separation chamber 6. The separated liquid particles are typically removed from the separation chamber 6 via outlets in the bottom closing plate 10. In this embodiment, the outlets are provided in the bottom closing plate, however, in other embodiments the outlets may be provided elsewhere, e.g. at a side of the separation chamber opposite of the side where the feed tube or feed entrance is located. In some embodiments, the feed tube or feed entrance may be located at the same side of the separation chamber as at least one of the outlets. In an embodiment, the feed entrance may be provided at a bottom side of the separation chamber, and at least one of the outlets may be provided at a top side. In another embodiment, the feed entrance may be provided at a bottom side, and at least one of the outlets may be provided at a bottom side as well. In another embodiment, outlets may be provided in the outer element. Many variants are possible. Depending on the different specific gravities of the particles, outlets may be provided at different radial distances as to collect the separated particles separately. Thus, it is possible to separate a slurry and/or suspension in two or more particle types, e.g. one solid and two different liquid particle types.

Solid particles radially with a specific gravity larger than the specific gravity of the carrying fluid move outwardly during rotation and hit a vane. Depending on e.g. the specific gravity and/or the size of the size of the solid particle, the solid particle may move further onto the surface 7a of the vane 7 until the solid particle reaches a position where it remains stuck.

When the rotation of a separation run is ended, the outer element 5 is removed and the elongate elements 7 can be reached. Then, the inner element 4 is set into rotation again for a cleaning run. During the cleaning run, the vanes 7 may elastically deform, e.g. to a state with a lesser curvature or a more straight form, so the solid particles are swung outwardly and removed from the vanes 7, thereby the vanes 7 are cleaned. When all the solid particles have been removed, the cleaning run may terminate, the outer element 5 may be moved over the inner element 4 again and the separator 1 may be prepared for a next batch run.

The inner element 4 may be driven by a drive unit, e.g. a motor, and set into rotation by the motor. Due to the mechanical coupling of the outer element 5 with the inner element 4, via the vanes 7, the outer element 5 is also rotated. Alternatively, the inner element 4 and the outer element 5 may be driven by different drive units at the same rotational speed, for example via electronical or mechanical synchronization, or may be driven by the same drive unit having two output axes, one output to the inner element and one output to the outer element. When then removing the outer element, the outer element may be uncoupled from the drive unit.

A top view of a set of elongate elements 7 connected to the inner element 2 is schematically shown in Figure 2a. For simplicity's sake, the protrusions on the vanes 7 are not shown in this figure. The set of elongate elements 7 as shown here, is also called a 'blade pack'. As can be seen in figure 2a, the elongate elements 7 are in this embodiment curved about an angle of 45 degrees with respect to a radial direction. This influences the path a - solid - particle may follow during rotation. It can also be seen that the distance between the elongate elements 7 is relatively small, in other words, the blade pack is relatively dense. In fact, the elongate elements 7 or vanes or blades are so configured that the distance "D" in radial direction R is the same over the elongate elements 7. Typically the distance D is between approximately 3 mm and approximately 15 mm, in an embodiment, the distance D is about 7 mm. The distance D depends on multiple

variables, e.g. the concentration of solids in the suspension or slurry. A higher concentration of the solid particles may result in a larger distance D. So, the distance a solid particle may have to travel before it hits a blade is relatively limited and is maximum the distance D. This increases the separation efficiency of the centrifugal separator 1. The distance is also the same between a protrusion and the adjacent elongate element. In particular during use, i.e. during a separation run, the distance between the elongate elements is the same over the elongate element, also at the positions of the protrusions. In Figure 2c can be seen that a particle that is launched in the separation chamber 6 is moved radially outwardly due to the centrifugal force and then hits the vane 7, the particle may then further travel onto the vane. The flow between the vanes 7 is a laminar flow during rotation, so particles move radially outwardly due to the centrifugal force. For example a particle may describe a path P. Therefore, it is important that the pattern of the protrusions 8 of adjacent vanes 7 is the same, such that the distance D between adjacent elongate elements 7 remains the same, also at the positions of the

protrusions 8. This is also illustrated in figure 3. In an embodiment, the radial distance between the elongate elements 7 may be maintained due to the relative stiffness of the elongate elements 7 and/or due to the elongate elements 7 contacting the outer element 5. In another embodiment, the radial distance between adjacent elongate elements may be maintained for example by distance keepers at a side and/or and edge of the elongate elements, leaving a central part of the elongate elements free to allow a distance between adjacent elongate elements, while allowing contact at the positions of the distance keepers, so not to disturb the flow of the suspension and/or slurry between the vanes 7.

Advantageously, to provide for a minimum disturbance of the path of the solid particles, the protrusions 8 preferably extend in a direction from the first element 2 towards the second element 3, or vice versa. As such, as can be seen in figure 3, elongated protrusions 8 extending in a direction transverse to the rotation axis A may be obtained along a longitudinal direction L of the plate 7. Also, the protrusions 8 preferably extend in a direction transverse to the surface 7a of the plate 7 to provide for increased stiffness against bending of the plates due to the centrifugal forces. Advantageously, the protrusions 8 are provided more towards an outer end 7b of the elongate elements 7. The outer end 7b contacts the outer element 5 during rotation.

An inner end 7c of the elongate elements 7 is hingedly connected to the inner element 4. The inner end 7c of the elongate element 7 can thereto be provided with openings 12 through which hooks of the inner element 4 may be hooked. As such, a hinged connection may be obtained. Of course, also other types of hinged connections may be possible, e.g. the inner element may be provided with upwardly extending pins around which sleeves of the elongate element fits, or vice versa. Due to the hinged connection, the elongate element 7 is rotatable connected to the inner element and its angular position may thus be altered for example during a cleaning run.

In figure 4 some embodiments of protrusions 8 are shown. It may be understood that more embodiments are possible. For example, figure 4a shows a pattern of elongated protrusions 8 with two protrusions in line in a direction from the outer end 7b to the inner end 7a, or vice versa, i.e. in the longitudinal direction L , of the elongate element 7. Figure 4b shows protrusions 8 in a wave-like pattern wherein the wave-like protrusions 8 extend on both sides of the plate 7. The waves 8 also extend in the

longitudinal direction but may end before reaching the inner end 7c of the plate 7, for example by fading out, or by simply terminating the wave- pattern. Figure 4c gives another example of protrusion 8, here embodied as relatively small rounded or cylindrical protrusions which may be provided in various patterns. Figure 4d shows another example of protrusion 8 that become larger towards the outer end 7b of the plate 7 and extend in the longitudinal direction L.

For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include

embodiments having combinations of all or some of the features described. It may be understood that the embodiments shown have the same or similar components, apart from where they are described as being different.

Many variants will be apparent to the person skilled in the art. AH variants are understood to be comprised within the scope of the invention defined in the following claims.

Claims

1. A centrifugal separator comprising a rotatably arranged upwardly extending first element with elongate elements connected thereto and an upwardly extending rotatably arranged second element, wherein the first element and the second element are approximately concentrically arranged with respect to each other around an upwardly extending rotation axis resulting in an inner element and an outer element providing a separation chamber therebetween, wherein the outer element is removable with respect to the inner element and wherein the elongate elements extend from the first element towards the second element, wherein at least a part of the elongate element comprises at least one protrusion.

2. The centrifugal separator according to claim 1, wherein the elongate elements are at a distance with respect to each other.

3. The centrifugal separator according to claim 1 or 2, wherein the at least one protrusion extends in a direction approximately transverse to a surface of the elongate element.

4. The centrifugal separator according to any of the preceding claims, wherein the at least one protrusion extends in a direction along the elongate element.

5. The centrifugal separator according to any of the preceding claims, wherein the at least one protrusion extends in a longitudinal direction from an outer end towards an inner end of the elongate element.

6. The centrifugal separator according to claim 5, wherein the at least one protrusion extends over a part of the length of the elongate element taken in the longitudinal direction of the elongate element.

7. The centrifugal separator according to any of the preceding claims, wherein the elongate element comprises a plurality of protrusions approximately parallel to each other.

8. The centrifugal separator according to any of the preceding claims, wherein a plurality of protrusions on an elongate element are provided in a pattern and adjacent elongate elements are provided with the same pattern of protrusions.

9. The centrifugal separator according to any of the preceding claims, wherein the protrusion is provided as a ridge in the elongate element.

10. The centrifugal separator according to any of the preceding claims, wherein the protrusion has a wave-like cross-section.

11. The centrifugal separator according to any of the preceding claims, wherein the elongate elements are hingedly connected to the first element.

12. The centrifugal separator according to any of the preceding claims, wherein the elongate elements are curved.

13. Elongate element provided with connection means for connection to a first element of a centrifugal separator according to any of claims 1 - 12, wherein the elongate element comprises at least one protrusion.

14. Pack of elongate elements comprising at least one protrusion for use in a centrifugal separator according to any of claims 1 - 12.