WO2008009939A1

WO2008009939A1 - Removal of magnetic particles from a fluid

Info

Publication number: WO2008009939A1
Application number: PCT/GB2007/002729
Authority: WO
Inventors: Martin Mckenzie
Original assignee: Romar International Limited
Priority date: 2006-07-21
Filing date: 2007-07-18
Publication date: 2008-01-24
Also published as: GB0614490D0

Abstract

The invention provides an apparatus (10) for removing magnetic particles from a fluid such as a liquid or slurry. The apparatus (10) includes an inlet port (13) through which fluid is admitted to the apparatus (10). A flat-bed (11) receives the fluid admitted, the flat-bed (11) having side walls to prevent the fluid from flowing off. One or more magnets (30) are located beneath the flat-bed surface and attract magnetic particles against the upper surface of the bed (11). An endless belt or chain (53) driven by a motor carries cleaning means (40) which engage the surface of the bed (11) and particles attracted by the or each magnet (30) along the surface until the particles drop off the end of the bed (11). Jets of air are directed against the flat bed surface to reduce the amount of fluid being carried along with the cleaning means (40).

Description

REMOVAL OF MAGNETIC PARTICLES FROM A FLUID

Field of the Invention

The present invention relates to apparatus for removing magnetic particles from a fluid. The apparatus finds particular application in the oil and gas industry in relation to separating iron swarf from free-flowing or viscous liquid mud.

Background to the Invention

Oil and gas wells usually have their bore holes lined with steel pipes, referred to normally as casing. In mature wells, when oil or gas production drops below economic production levels, it is often useful to utilise at least part of said bore hole to produce new bore holes into as yet untouched reserves. In order to be able to do this one alternative is to remove the casing completely. However, it is more often cost effective to simply drill the pipeline out, or at least to drill a section mill in the pipeline. The section mill can then be used to allow a drilling assembly to exit the bore hole and reach a new part of the reservoir.

Such a method obviously produces large quantities of steel swarf derived primarily from the pipeline. The swarf is mixed during the drilling process with large quantities of mud either from the bore hole or from its introduction as a lubricant. Typically the mud / swarf mixture will comprise a sufficient quantity of water to enable the mixture to flow.

Due to the high steel content of the mud when it exits the bore hole and its potential hazard, in part due to the sharpness of the metal slithers it contains, disposal or re-use of the mud can be problematic. One method of decontamination is simply to remove excess water from the mixture and then separate the larger swarf pieces by hand. This is obviously a time consuming and potentially dangerous mode of separation. It is an object of the present invention to provide an improved apparatus to separate the solid magnetic or magnatisable particles from a fluid system and in particular, apparatus which can be applied in the oil and gas industry.

Summary of the Invention

According to the invention there is provided an apparatus for removing magnetic or magnetisable particles from a fluid such as a liquid or slurry, the apparatus comprising:

an inlet through which fluid enters the apparatus;

a flat-bed to receive the fluid, the flat-bed having side walls extending therefrom to form a channel to retain fluid;

one or more magnets beneath the surface of the flat-bed to attract the particles against the flat-bed;

the apparatus further comprising an endless belt or chain, driven by a motor, a portion of the path of the belt being parallel to the surface of the flat-bed; the belt carrying at spaced intervals cleaning means, which in the parallel portion are in touching or contiguous relationship with the flat-bed, movement of the belt from first end to a second end of the flat-bed causing the cleaning means to push attracted particles along and off the second end of the flat-bed.

The apparatus provides for a large through put of fluid to be decontaminated from steel or other magnets or magnetisable particles retained in for example, drill cuttings.

The second end of the flat-bed is advantageously higher than the first end. This enables the fluid together with magnatisable or non-magnatisable particles to run off the first end of the flat-bed and thus be separated from the magnetic or magnetisable particles. The angle at which the flat-bed is set is preferably from 10- 35°, and especially preferably 23-27°.

The apparatus preferably includes an air-jet flushing a jet of gas onto the flat-bed to hinder or prevent fluid from being carried over the second end of the flat-bed. The magnetic particles are thereby separated in a relatively dry condition.

Advantageously, the apparatus includes a further air jet so orientated to direct air against the rear surface of the cleaning means. Especially advantageously, a yet further air jet is included beneath the flat-bed directing air against those cleaning means not engaging the flat-bed to further remove material adhering to the cleaning means. The or each air jet is preferably pivotally mounted, motion of each air jet moving the air jet back and forth across the width of the flat-bed. It is thereby ensured that the whole area of the flat-bed and cleaning means are cleaned.

Advantageously the magnets are arranged in lines across the flat-bed, alternate lines providing alternate polarities. Each line is particularly advantageously formed of a plurality of spaced apart magnets.

The alternate polarity provides lines of magnetic flux connecting adjacent lines along which the magnetic or magnetisable particles can move and which lines retain the particles on the flat-bed.

The flat-bed is optionally formed of steel which prevents magnetic flux from the magnets extending too far beyond the surface.

The or each cleaning means is preferably a strip of metal or other suitable material extending across the width of the flat bed and providing a cleaning surface in the direction of travel of the strip. Further preferably, the or each cleaning means include a cleaning element formed of resilient material along the lower edge the cleaning means engaging the surface of the flat-bed. Small particles which might otherwise accumulate in irregularities in the flat-bed's surface are thereby removed.

Preferably the apparatus includes one or more grilles to retain larger pieces of material and prevent these from rolling down a sloping flat-bed. The or each grille can advantageously be secured to the endless belt to ensure that large material is removed from the belt.

Especially advantageously the or each grille is secured to a cleaning mass to improve the strength of the grille. The or each grille optionally comprises parallel orientated tines .

Optionally, the apparatus includes a container into which particles pushed off the end of the flat-bed fall, whereby collection of said particles is facilitated.

Brief Description of the Drawings

The invention will now be described with reference to the accompanying drawings which show by way of example only two embodiments of an apparatus for removing magnetic or magnetisable particles from a liquid or slurry. In the drawings:

Figures Ia-Ic are respectively a side, end and top view of a first embodiment of an apparatus;

Figure 2 illustrates a grille comprising tines;

Figures 3 a and 3b are respectively an illustrative side view and underside view of a flat-bed;

Figure 4 is a perspective illustration of a flat-bed and cleaner plates;

Figure 5 is a sectional view along A-A of Figure 1; Figure 6 illustrates cleaner plates on an endless belt; and

Figure 7 is a side view of a second embodiment of an apparatus.

Detailed Description of the Invention

Referring initially to Figure la-c these illustrate an apparatus for removing magnetic or magnetisable particles - referred to in this specification collectively as magnetic - from a liquid. Particularly contemplated is the removal of swarf or metal turnings from a mud slurry produced as part of the oil drilling process. As indicated above, the mud usually exits the bore hole in the form of a flowable mud which can have a low viscosity close to that of water but can also be relatively viscous. The mud contains primarily rock or earth particles at least partially suspended in water, together with contaminants such as steel particles and some organic material.

The apparatus 10 is designed to separate the steel and other magnetic particles from the mud to enable further processing of both components. In order to accomplish this, the apparatus 10 comprises a flat-bed 11 having an upwardly facing flat surface formed of steel to receive the mud. A series of magnets are located against the downward facing surface of the flat-bed 11, which magnets act to attract magnetic particles from the mud and retain the particles against the flatbed 11. As can be seen from Figure Ia, the flat-bed 11 is set at an angle of 27° to the horizontal, and the slope of the upwardly facing surface causes the mud to flow downwardly along the flat-bed 11 to a collection element (not illustrated). It has been found that angles of 10-35° and particularly 23-27° are suitable. In order to keep the mud on the flat-bed 11 as it flows away, the flat-bed 11 has two side walls orientated substantially perpendicularly to the bed 11, which together form a channel to constrain the mud flow. In order to move the magnetic particles along the bed 11 a series of cleaner plates 40 (see Figure 4) are provided. The cleaner plates 40 are substantially rectangular and are mounted such that one of their edges 41 is closely adjacent to or touching the surface of the flat-bed 11. The cleaner plates 40 are moved along the flat-bed

11 towards the higher end of the flat-bed 11. In doing so magnetic particles held to the flat-bed 11 are also pushed along.

In more detail, the apparatus 10 comprises a housing element 12 formed of steel which supports the elements of the apparatus and can enclose the moving parts of the apparatus 10 to prevent injury to operators and also minimise contamination of the surrounding area. As indicated above, a flat-bed 11, also formed of steel is held in position at an acute angle to the horizontal, hi order to enable contaminated mud to be introduced onto the bed, an inlet port 13 is included, opening directly onto the flat-bed 11.

Steel turnings or other magnetic particles contained in the mud are retained on the flat-bed 11 by the magnets 30 shown in Figure 3, located on the underside of the flat-bed 11. An endless belt (see Figure 6, 53) is mounted on motor driven rollers 14A, 14B which maintain the belt 53 in motion such that the belt 53 moves parallel to the upwardly facing surface of the flat-bed 11 towards the higher end of the flat-bed 11. The belt 53 carries a series of cleaner plates 40 which engage or are maintained in contiguous relationship to the flat-bed 11 as they move. The embodiment in Figure Ia shows that attached to each cleaner plate 40 is a grille 15 consisting of a series of parallel tines shown in more detail in Figure 2.

Although the embodiment shown has a grille 15 attached to each cleaner plate 40, this is not essential and grilles 15 can be attached to alternate, or to every third, fourth etc. cleaner plate 40. The purpose of the grilles is to prevent large agglomerates which enter the apparatus 10, from simply rolling down the flat-bed 11. In doing so there is a chance that the steel they may contain would not be recovered. Moreover, sufficient agglomerates may lead to blockage of the outlet for the decontaminated mud stream. Referring to Figures 3a and 3b, these illustrate the location of the magnets 30. Each of the magnets 30 in the embodiment shown is comprised of a layered assembly of smaller magnets 31 arranged such that the North-South (N-S) polarities of the smaller magnet 31 are in alignment with one another. The layered magnets (or magnet assemblies) 30 are arranged in lines across the width of the flat-bed 11 and are so arranged that the magnetic pole against the lower surface of the flat-bed 11 in each line is the same. Moreover adjacent lines are arranged to be of opposite polarity. This arrangement provides for loops of magnets flux extending from the upward facing surface of the flat-bed 11 which provide a path for the motion of swarf along the flat-bed 11. The flat-bed 11 is made of a steel to reduce extension of the magnetic flux lines too far from the surface of the flat-bed 11.

Towards the higher end of the flat-bed 11, there is a region in which no magnets 30 are present. This enables swarf to be more easily released and pushed over the edge of the flat-bed.

The apparatus 10 further comprises an outlet chute 16 which leads to a collection container (not illustrated) for metal particles removed from the mud.

Movement of the cleaner plates 40 inevitably carries a proportion of water and non-magnetic particles from the mud along with the swarf. In order to minimise the amount of water passing into the outlet chute 16 and hence on into the collection chamber, an air-jet 17 is included. The air-jet 17 directs a flow of air onto the flat-bed 11 in a direction pointing in opposition to the upward motion of the cleaner plates 40. Water and non-magnetic mud are thereby blown back down the slope of the flat-bed 11.

To assist flow of non-magnetic material down the flat-bed 11, the cleaner plates 40 can include a number of apertures to allow this material to pass through the plates 40. Moreover, the plates 40 can be orientated such that they subtend an obtuse angle with the flat-bed 11 with reference to the direction of movement.

Fluid can thereby flow more readily over a cleaner plate 40 with a smaller chance of a "bow wave" being formed which would act to push liquid along.

Figures 5 and 6 illustrate a means by which the cleaner plates 40 are maintained in close relationship with the flat-bed 11. Secured to the side of, and running along the edge of the flat-bed 11 is a channel 51 to receive rollers 52 attached to the endless belt 53. The rollers 52 run within the channel 51 and a force is thereby imparted to the cleaner plates 40 to force the cleaner plates 40 towards the flat-bed 11. The apparatus 10 also includes further channels 54 underneath the flat-bed 11 to guide the belt 53 on its return to the flat-bed 11.

Figure 5 further illustrates a steel pole piece 55 located beneath the magnet assemblies 30. The pole piece 55 reduces downward extension of the magnetic field and increases the magnetic flux extending upwards from the flat-bed 11.

Figure 6 illustrates in greater detail a cleaner plate 40. The cleaner plate 40 comprises an elongate support piece 60 formed of a steel strip formed into a right angle. A cleaning element 61 is supported across the support piece 60 and is positioned such that its lower edge engages, or is contiguous with the upper surface of the flat-bed 11.

A second embodiment of an apparatus 70 for removing magnetic particles from a liquid is shown in Figure 7. The apparatus 70 includes a number of similarities to the apparatus 10 of the first embodiment. The apparatus 70 comprises a flat-bed

71 set at an angle of 25° to the horizontal. An endless belt 72 is mounted on rollers 73, 74 which moves the belt 72 around the flat-bed 71. A series of magnets 75 are positioned beneath the upper surface of the flat-bed 71. In order to increase the extension of magnetic flux beyond the upper surface of the flat-bed 71, a steel layer is included beneath the magnets 75. Cleaner plates 76 are attached to the endless belt 72 to remove magnetic swarf held to the surface of flat- bed 71. An inlet port 77 is provided through which the mud slurry is introduced into the apparatus 70 and onto the flat-bed 71. The apparatus 70 includes a set of tines 78 fixed across the width of the flat-bed 71. The tines 78 prevent large pieces of material, which would otherwise roll down the slope of the flat-bed 71, from so doing. The large pieces are then carried up the flat-bed 71 and over the upper end. In order to remove material which accumulates between the individual elements of the tines 78 a number of further sets of tines 79 are attached at spaced apart intervals connected to the cleaner plate 76. The individual elements of the tines 79 are approximately 7.5cm in length and set so that they pass through those of the tines 78. The tines 79 act to clean the tines 78 as they pass through and also assist in the carriage of the larger material along the flat-bed 71.

In order to reduce the amount of water passing up the flat-bed 71, an air jet 80 directs a jet of air against the flat-bed 71, in a direction counter to the flow of the endless belt 72. The air jet 80 is connected to a motor 81 which causes the air jet

80 to move back and forth across the width of the flat-bed 71. A further air jet 82 is orientated in the plane perpendicular to the flat-bed 71, and directs a jet of air towards the back of the cleaner plate 76 as they pass over the end of the flat-bed 71. The air jet 82 acts to blow residual material from the back of the cleaner plate

76. The air jet 82 is moved back and forth across the flat-bed 71 by a motor 83.

A further air jet 84 is located on the underside of the flat-bed 71, and is again so directed to oppose the movement of the endless belt 72. The air jet 84 removes residual material from the front of the cleaner plate 76. Again, a motor 85 moves the air jet 84 back and forth across the width of the flat-bed 71.

The apparatus 70 includes a rubber sheet 86, 5mm in thickness. The sheet 86 acts to reduce turbulence of the mud slurry flowing down the slope and to prevent contamination of the outer casing 87 of the apparatus 70. In addition to the above, a number of the cleaner plates 76 include rubber strips (not illustrated) along the lower surface of the cleaner plates 76. The rubber strips closely engage the flat-bed 71 and remove small pieces of swarf which might otherwise accumulate in any irregularities in the upper surface of the fiat-bed 71.

Pn use therefore, the machine is activated and the endless belt set in motion. Mud slurry from a storage facility is pumped through the inlet port 13. The slurry passes through the inlet port 13 and flows onto the flat-bed 11. Swarf 42 contained within the slurry is attracted to one of the magnets 30 and held against the surface of the flat-bed 11 by magnetic attraction. The non-magnetic components of the slurry such as the water and mud particles flow down the slope of the flat-bed 11.

The swarf 42 thus held against the surface is pushed in an upwards direction along the flat-bed 11 by the cleaner plates 40 attached to the endless belt. The motion is assisted by the magnetic flux lines from the adjacent lines of magnets 30 which have a component away from the surface and so act to lift the swarf 42 slightly away from the surface. Frictional resistance is thereby reduced. The swarf 42 is pushed to the end of the flat-bed 11 to a region adjacent to the upper roller 14B.

Here the endless belt and the cleaner plates 40 curve around the end of the flat-bed 11 and return to the bottom of the flat-bed 11. The swarf 42 pushed by the cleaner plates 40 is here no longer under the influence of the magnets 30 and falls off the flat-bed 11, into the outlet chute 16 and thence to a collection container for suitable disposal.

The water and mud flowing off the bottom end of the flat bed 11 are collected in a suitable container for disposal or re-use.

Large agglomerates contained in the original slurry are not permitted to roll down the flat-bed as they could cause damage, cause a blockage at the base of the slope, or knock swarf off the surface of the flat-bed 11. Instead the large agglomerates are captured on grilles 15 which are attached to and move with the cleaner plates 40. They therefore pass into the outlet chute 16 and can be readily separated and if necessary broken and reintroduced through the inlet port 13 to allow any swarf they contain to be reclaimed.

It will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention.

Claims

1. An apparatus (10) for removing magnetic particles from a fluid such as a liquid or slurry, the apparatus (10) comprising:

an inlet (13) through which fluid enters the apparatus (10);

a flat-bed (11) to receive the fluid, the bed (11) having side walls extending therefrom to form a channel to retain fluid;

one or more magnets (30) beneath the surface of the bed (11) to attract particles against the flat-bed (11);

the apparatus further comprising an endless belt or chain (53) driven by a motor, a portion of the path of the belt (53) being parallel to the surface of the flat-bed (11);

cleaning means (40) at spaced intervals along the belt (53), which cleaning means (40) are in touching or contiguous relationship with the flat-bed (11) in the parallel portion, movement of the belt (53) from a first end to a second end of the flat-bed (11) causing the cleaning means (40) to push attracted particles along and off the second end of the flat-bed (11)

2. An apparatus according to Claim 1, wherein the second end of the flat-bed (11) is at a higher elevation than the first end.

3. An apparatus according to Claim 2, wherein the angle at which the flat- bed (11) is set is from 10-35° to the horizontal.

4. An apparatus according to Claim 3, wherein the angle is from 23-27°.

5. An apparatus according to any preceding Claim, wherein the apparatus includes an air-jet to flush a jet of gas onto the flat-bed (11) to hinder or prevent fluid from being carried over the second end of the flat-bed (11).

6. An apparatus according to Claim 5, wherein the apparatus includes a further air jet so orientated to direct air against a rear surface of the cleaning means.

7. An apparatus according to Claim 6, wherein a yet further air jet is included beneath the flat-bed directing air against those cleaning means not engaging the flat-bed.

8. An apparatus according to Claims 5-7, wherein the or each air jet is pivotally mounted, motion of the or each air jet directing jets of gas back and forth across the width of the flat-bed.

9. An apparatus according to any preceding Claim, wherein the magnets are arranged in lines across the flat-bed, alternate lines providing alternate polarities.

10. An apparatus according to Claim 9, wherein each line is formed of a plurality of spaced apart magnets.

11. An apparatus according to any preceding Claim, wherein the flat-bed is formed of steel.

12. An apparatus according to any preceding Claim, wherein the or each cleaning means is a strip of material extending across the width of the flatbed and providing a cleaning surface in the direction of travel of the strip.

13. An apparatus according to Claim 12, wherein the strip is formed of steel.

14. An apparatus according to Claim 12 or Claim 13, wherein one or more strips includes a cleaning element formed of resilient material along the lower edge of the cleaning means engaging the surface of the flat-bed.

15. An apparatus according to any preceding Claim, wherein the apparatus includes one or more grilles to retain larger pieces of material.

16. An apparatus according to Claim 15, wherein the or each grille is secured to the endless belt.

17. An apparatus according to Claim 15 or Claim 16, wherein the or each grille is secured to a cleaning means to increase the strength of the grille.

18. An apparatus according to Claim 15-17, wherein the or each grille comprises parallel-orientated tines.

19. An apparatus according to any preceding Claim, wherein the apparatus includes a container to catch particles pushed off the end of the flat bed.

20. An apparatus substantially as herein described with reference to and as illustrated by the accompanying drawings.