The present invention relates to apparatus for separating solid particles from a flow of fluid and in particular, but not exclusively, to apparatus for separating solid particles from a flow of fluid from a hydrocarbon well.

Hydrocarbon streams retrieved from oil and gas wells are typically contaminated with unwanted fluids (e.g. water) and suspended solid particles which must be removed. It is particularly desirable to remove suspended solid particles, as they would otherwise potentially collect downstream and restrict or block the fluid flow, requiring potentially expensive intervention to resolve and resulting in expensive non-operating downtime.

The presence of solid particles in hydrocarbon streams tends to be increased from sites where hydraulic fracturing (“fracking”) and similar techniques are carried out, in which fluids in which sand or other proppants are suspended or injected under high pressure into a wellbore to increase the flow of hydrocarbons from rock formations in which the hydrocarbons are held.

It is known to use cyclonic separators to separate solid particles suspended in hydrocarbon streams.

It is an aim of the present invention to provide a cyclonic separator with improved performance.

In accordance with the present invention, an apparatus for separating solid particles from a fluid flow comprises: a housing, the housing comprising: an inlet for the fluid flow; a first outlet for the fluid flow; a second outlet for solid particles separated from the fluid flow; a central region comprising a substantially cylindrical inner surface; an upper end region at a first end of the central region, comprising a concave inner surface; and a lower end region at a second end of the central region, comprising a frusto-conical inner surface.

The substantially cylindrical inner surface in the central portion of the housing helps to separate the solid particles efficiently from the fluid flow as the vortex produced by the flowing fluid can be arranged to be more horizontal than, for example, the vortex produced by a spherical inner wall. This is thought to produce a significantly more predictable flow path and results in an improved separation of solid particles.

The frusto-conical inner surface of the lower end region of the housing offers improves collection of the separated solid particles at a location immediately above the outlet for separated solids. The concave inner surface at the upper end of the housing helps to generate a smooth, predictable vortex and facilitates efficient removal of fluid from the housing.

The housing may comprise a plurality of housing portions, for example two housing portions, assembled and secured together. Forming the housing from a plurality of housing portions significantly facilitates the manufacture of the hollow housing.

The apparatus may comprise upper and lower housing portions.

Each of the upper and lower housing portions may comprise a cylindrical inner surface which forms part of the substantially cylindrical inner surface of the central region when the housing portions are assembled.

The upper housing portion may comprise a cylindrical inner surface at its lowermost end and the lower housing portion may comprise a cylindrical inner surface at its uppermost end which, when the housing portions are assembled, form a substantially cylindrical inner surface of the central region.

The concave inner surface may be formed on the upper housing portion.

The frusto-conical inner surface may be formed on the lower housing portion.

The apparatus may comprise a plurality of housing portions welded together.

Preferably, all of the housing portions are welded together. The inlet for the fluid flow may open into the central region of the housing.

The inlet for the fluid flow may open onto the cylindrical inner surface of the central region of the housing.

The inlet for the fluid flow may comprise an inlet pipe configured to introduce fluid in a direction substantially perpendicular to the longitudinal axis of the cylindrical inner surface of the central region of the housing.

The inlet may be configured to introduce fluid in a direction substantially tangential to the cylindrical inner surface of the central region of the housing.

This produces a vortex in the fluid flow from which suspended particles are separated. By directing the fluid flow tangentially onto the cylindrical inner surface of the central region of housing, a controlled and predictable vortex flow can be achieved.

The first outlet for the fluid flow may be located at the uppermost portion of the concave inner surface of the upper end region.

The frusto-conical inner surface of the lower end region may taper downwardly and the second outlet for solid particles separated from the fluid flow may be located at the lowermost portion of the frusto-conical inner surface.

The frusto-conical inner surface of the lower end region helps to both separate the suspended solid particles from the fluid flow and direct the separated particles towards the solids outlet.

The apparatus may comprise a filter extending into the interior space of the housing, through which fluid must pass in order to exit the housing.

The use of a filter helps to remove solid particles which have not been separated from the fluid flow by movement through the housing, for example smaller or lighter particles which remain entrained in the fluid flow.

The apparatus may comprise an elongate filter extending into the interior space of the housing.

The filter may be positioned in the first outlet for the fluid flow. By way of example only, specific embodiments of the present invention will now be described, with reference to the accompanying drawings, in which:

Figure 1 is a side view of an embodiment of apparatus for separating solid particles from a flow fluid in accordance with the present invention;

Figure 2 is a vertical cross-section through the apparatus of Figure 1 ;

Figure 3 is a vertical cross-section through the apparatus of Figure 1 , fitted with an internal filter; and

Figure 4 is a horizontal cross-section through the apparatus shown in Figure 3, looking in the direction of arrows 4 - 4 in Figure 3.

The apparatus shown in the figures comprises a metal housing indicated generally at 10 which defines an enclosed interior volume indicated generally at 12. The housing is provided with an inlet 14 for the ingress of fluid, a first elongate outlet port 16 at the upper end of the housing for the exit of fluid and a second outlet 18 at the lower end of the housing for the exit of solid particles separated from the fluid, as will be explained.

The exterior of the housing has a cylindrical central outer surface 20, a domed upper outer surface contiguous 21 with the upper end of the cylindrical outer surface 20 and a frusto- conical lower outer surface 22 which merges with the lower end of the cylindrical outer surface 20 at a rounded interface 23. The domed upper outer surface is also provided with a plurality of lifting lugs 24. The cylindrical outer surface 20 is provided at its upper end with a pair of identical, diametrically opposed mounting brackets 25 and a further bracket 26 arranged midway between the brackets 25, for mounting the housing on a supporting framework (not shown). The uppermost end of the housing 10 is formed into an annular planar face 28 around the outer end of the outlet port 16, in which twelve identical equally angularly spaced threaded recesses 30 are formed, each for receipt of a respective identical mounting bolt 32. Similarly, the lowermost end of the housing 10 is formed into an annular planar face 36 around the outer end of the outlet port 18, in which eight identical equally angularly spaced threaded recesses 38 are formed, each for receipt of a respective identical mounting bolt 40.

The housing 10 is formed from upper and lower generally dome-shaped housing portions 44, 46, which are permanently joined together by a circumferential weld 48. The upper housing portion 44 comprises a generally cylindrical inner wall 50 and a curved, torispherical inner wall 52, with a so-called “knuckle” 54 between the cylindrical wall and the torispherical wall. The elongate upper outlet port 16 is located in the centre of the torispherical inner wall 52 and is coaxial with the longitudinal axis A - A of the cylindrical inner wall 50.

The lower housing portion 46 comprises a generally cylindrical inner wall 58 which merges smoothly via a concave inner wall portion 60 with a frusto-conical inner wall 62. The elongate lower outlet port 18 is located symmetrically with respect to the frusto-conical inner wall 62 and is coaxial with the longitudinal axis A - A of the cylindrical inner wall 50.

When the upper and lower housing portions 44, 42 are secured together by the circumferential weld 48, the cylindrical inner walls 50, 58 respectively of the upper and lower housing portions 44, 46 form a continuous central housing portion 66 having a cylindrical inner surface 68, with the torispherical inner wall 52 and the frusto-conical inner wall 62 located at opposite ends of the cylindrical inner surface 68.

As shown in the figures, the fluid inlet 14 comprises a short, straight pipe portion 70 extending from the upper housing portion 44 at right angles to the longitudinal axis A - A of the cylindrical inner wall 50 and arranged tangentially with respect to the cylindrical inner surface 68, as shown by the generally teardrop-shaped opening 72 on the cylindrical inner surface 68. The opening 72 is positioned towards, but below, the upper end of the cylindrical inner surface 68. The fluid inlet also has a mounting flange 74 for connection to an upstream component (not shown).

Optionally, and as shown in Figure 3, a known, cylindrical, elongate filter 80 is located in the upper outlet port 16. The filter 80 extends into the interior volume 12 to a position just above, but spaced from, the inner end of the lower outlet port 18, and is coaxial with the longitudinal axis A - A of the cylindrical inner wall 50. The filter 80 is sealingly mounted in a securing collar 82 mounted to the upper end of the housing 10 by means of the securing bolts 32 and ensures that any fluid leaving the housing via the upper outlet 16 also passes through the filter 80.

In use, the housing 10 is arranged with the longitudinal axis A - A of the cylindrical inner wall 68 extending substantially vertically. Fluid is fed under pressure into the enclosed interior volume 12 through the pipe portion 70 of the inlet 14 which is connected to upstream pipework (not shown) by means of the mounting flange 74. As best seen in Figure 4, the fluid passing through the pipe portion 70 enters the enclosed interior volume 12 through the opening 72 tangentially with respect to the cylindrical surface 68, as shown by arrow A in Figures 2 to 4.

As is known in cyclonic separators, as the solid particles suspended within the fluid flow enter the housing 10, they are subjected to a several different forces, the cumulative effect of which is that they lose momentum and travel downwardly towards the lower end of the housing 10, as shown schematically by arrows B and C in Figures 3 and 4 respectively, while the remaining fluid is drawn upwardly to pass out of the outlet 16 at the upper end of the housing (and also passing through the longitudinal filter 80, if fitted). The actual trajectory taken by the solid particles will depend on many different factors, such as the size and weight of the particles, the speed of the particles as they enter the housing, the fluid within which the solid particles are suspended, etc. however, the particles separated from the flowing fluid are directed by the frusto-conical lower inner wall portion 60 so that they collect in the base of the housing and in the lower outlet 18 located at the apex of the frusto-conical wall portion 60, as illustrated schematically at 88 in Figure 3.

The separated solid particles 88 can then be periodically removed from the housing 10 by opening a valve connected to an outlet pipe (not shown) connected to the lowermost end of the housing 10 by means of the securing bolts 40. The remainder of the fluid exits the housing 10 via the outlet 16 at the upper end of the housing 10.

The substantially cylindrical wall 68 in the central portion of the housing helps to separate the solid particles efficiently from the fluid flow as the vortex produced by the flowing fluid entering the housing tangentially is more horizontal than, for example, the vortex produced by a spherical inner wall. This is thought to produce a significantly more predictable flow path and results in an improved separation of solid particles.

The frusto-conical lower portion 60 of the interior of the housing offers improves collection of the separated solid particles at a location immediately above the solids outlet 18. Finally, the smoothly curved surface 52 at the upper end of the housing 10 (a torispherical surface in the illustrated embodiments) helps to generate a smooth, predictable vortex and facilitates efficient removal of fluid from the housing 10.

The invention is not restricted to the details of the foregoing embodiments.

For example, in the above embodiments, the housing is formed from upper and lower housing portions. However, the housing portions may be joined together along a plane other than a horizontal plane, for example a vertical plane or a plane inclined to the vertical and horizontal. The housing may also be formed from a single housing portion or from more than two housing portions. In the above embodiments, the housing portions are joined together by means of a circumferential weld 48. However, if more than one housing portion is present, they may be joined together by means other than welding, for example by means of bolts.

A plurality of apparatuses accordance the present invention may be connected together in series. The plurality of apparatuses may be substantially identical or may be different from each other, for example to remove different types and/or sizes of suspended solid particles.

In the above embodiments, the upper portion 52 of the inner wall is torispherical. However, other curved wall shapes may be used, if desired.