Multiphase flow mixing apparatus and method of mixing

Abstract

An apparatus and associated method for mixing at least a first fluid phase having a first density and a second fluid phase having a second density, the apparatus comprising; at least one container (1), the container comprising at least one inlet (2) for a multiphase flow and at least one outlet (3) at a lower axial end of the container (1), a hollow flow regulating device (4) axially arranged within the container (1), wherein a first end of the flow regulating device (4) is arranged in a distance from the outlet (3) providing a drainage gap (5) between the flow regulating device (4) and the outlet (3), which drainage gap (5) has a drainage area, the flow regulating device (4) comprising a number of perforations (6) along the axial length thereof and a discharge means (7) in a first end, which discharge means (7) opens towards the outlet (3), the flow regulating device (4) being connected to a position adjustment device (8), the position adjustment device (8) being arranged to move the flow regulating device (4) in the axial direction, thereby adjusting the drainage area of the drainage gap (5).

Claims

1. A subsea multiphase flow mixing apparatus for mixing a multiphase flow comprising at least a liquid phase and a gas phase, the apparatus comprising: at least one container which is configured to be disposed subsea and includes at least one inlet for the multiphase flow and at least one outlet located at a lower axial end of the container; a hollow flow regulating device which is axially arranged within the container and includes a lower first end located an axial distance from the outlet to thereby provide an axially extending drainage gap between the lower first end of the flow regulating device and a top of the outlet, the drainage gap having a drainage area and the flow regulating device comprising a number of perforations along the axial length thereof and a discharge opening in the first end which opens towards the outlet; and a position adjustment device which is connected to the flow regulating device and is configured to selectively move the flow regulating device in the axial direction to selective stationary positions to thereby adjust the drainage area of the drainage gap; wherein the position adjustment device comprises an external interface arranged on the outside of the container; and wherein the external interface is configured to be manipulated by an ROV manipulator or an actuator wired to a subsea control system.

2. The apparatus according to claim 1, wherein the position adjustment device is connected to an upper second end of the flow regulating device.

3. The apparatus according to claim 1, wherein during operation of the apparatus, the multiphase flow separates into at least the liquid phase and the gas phase in the container, and wherein the inlet and the outlet are arranged such that the liquid phase having the largest density separates at the lower axial end of the container, closest to the outlet.

4. The apparatus according to any of claims 1-3, wherein the container converges as an abutted cone at the outlet.

5. The apparatus according to any of claims 1-3, wherein the diameter of the flow regulating device is equal to the diameter of the outlet.

6. The apparatus according to claim 1, further comprising a venturi located downstream of the outlet.

7. In a subsea multiphase flow mixing apparatus for mixing a multiphase flow comprising at least a liquid phase and a gas phase, the apparatus comprising at least one container which is configured to be disposed subsea and a hollow flow regulating device which is axially arranged within the container, the container including at least one inlet for the multiphase flow and at least one outlet located at a lower axial end of the container, the flow regulating device comprising a lower first end located an axial distance from the outlet, a plurality of perforations extending along the axial length thereof and a discharge opening in the lower first end which opens towards the outlet, the lower first end of the flow regulating device and a top of the outlet defining an axially extending drainage gap having a drainage area, the improvement comprising a position adjustment device which is connected to the flow regulating device and is configured to selectively move the flow regulating device in the axial direction to selective stationary positions to thereby adjust the drainage area of the drainage gap.

8. The apparatus according to claim 7, wherein the position adjustment device is connected to an upper second end of the flow regulating device.

9. The apparatus according to claim 7, wherein during operation of the apparatus, the multiphase flow separates into at least the liquid phase and the gas phase in the container, and wherein the inlet and the outlet are arranged such that the liquid phase having the largest density separates at the lower axial end of the container, closest to the outlet.

10. The apparatus according to claim 7, wherein the container converges as an abutted cone at the outlet.

11. The apparatus according to claim 7, wherein the diameter of the flow regulating device is equal to the diameter of the outlet.

12. The apparatus according to any of claim 7, wherein the position adjustment device comprises an external interface arranged on the outside of the container which is configured to be manipulated by an ROV manipulator.

13. The apparatus according to claim 7, further comprising a venturi located downstream of the outlet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an example of a mixing apparatus according to the prior art.

(2) FIG. 2 shows an embodiment of the mixing apparatus according to the present invention.

DETAILED DESCRIPTION OF A PREFERENTIAL EMBODIMENT

(3) FIG. 1 shows an example of a mixing apparatus according to the prior art, where the mixing apparatus is exemplified as a container 1. The container 1 has an inlet 2 for a multiphase flow. The multiphase flow comprises a mixture of at least a first fluid phase having a first density, e.g. a liquid, and a second fluid phase having a second density, e.g. a gas. An outlet 3 is arranged at the lower axial end of the container 1. The liquid level inside the container 1 is shown as a gas-liquid interface 10. A hollow flow regulating device 4 is axially arranged inside the container 1. The flow regulating device 4 is connected at an upper part of the inner surface of the container 1 and extends a fixed distance towards the outlet 3. The flow regulating device 4 opens towards the outlet 3 through discharge means 7. Further, the flow regulating device 4 is provided with perforations 6 along its circumference, which perforations 6 extend along the axial length of the flow regulating device 4. A drainage gap 5 forms a fixed drainage area between the lower axial end of the flow regulating device 4 and the outlet 3. Multiphase flow entering through inlet 2 will, due to gravity, separate into a gas phase and a liquid phase inside the container 1, shown by the gas-liquid interface 10. The gas flows through the perforations 6 to the inside of the flow regulating device 4. The liquid, which due to gravity separates in the lower part of the container 1 closest to the outlet 3, draws out gas through the discharge means 7 and the mixed gas-liquid flow flows through the outlet 3 as a homogenous flow. This is due to a pressure difference between the inside of the container 1 and downstream of the outlet 3. The pressure difference might be created by a narrowing of the flow are e.g. a venturi (not shown), or by a pump creating a suction pressure.

(4) FIG. 2 shows an embodiment of the mixing apparatus according to the present invention. Similar to FIG. 1 there is shown a container 1 having an inlet 2 for a multiphase flow. An outlet 3 is arranged at the lower axial end of the container 1. The liquid level inside the container 1 is shown as a gas-liquid interface 10, A hollow flow regulating device 4 is axially arranged inside the container 1. The flow regulating device 4 is connected to an adjustment device 8 in the upper axial end of the container, which adjustment device 8 comprises a flexible arrangement 11 and an external interface 9. The flow regulating device 4 opens towards the outlet 3 through discharge means 7. Further, the flow regulating device 4 is provided with perforations 6 along its circumference, which perforations 6 extend along the axial length of the flow regulating device 4. The external interlace 9 is arranged on the outside of the container 1 and can be manipulated from the outside. The external interface 9 might be in the form of a screw, bolt or any other interlace suitable for manipulation by a ROV manipulator, a torque tool or an actuator wired to a subsea control system (not shown). By manipulating the external interface 9 of the position adjustment device 8, the position adjustment device 8 causes the flow regulating device 4 to move in the axial direction such that the drainage gap 5, and thus the drainage area, between the lower axial end of the flow regulating device 4 and the outlet 3, is modified. Depending on the mixture of the multiphase flow through the inlet 2, the drainage gap 5 may be adjusted according to the multiphase flow mixture. Moving the flow regulation device 4 away from the outlet 3 will lead to a larger amount of liquid flowing out of the container 1. Correspondingly, by moving the flow regulating device 4 towards the outlet 3, a larger amount of gas will flow out of the container 3. In cases where sand or debris has gathered at the outlet 3, the flow regulating device 4 can be moved away from the outlet 3, allowing the sand or debris to be flushed out through the outlet 3.

(5) By the use of the arrangement as described herein, one is able to adjust the amount of liquid and/or gas flowing out from the flow mixer through the outlet, and thus minimize slug flow.

(6) The invention is herein described in non-limiting embodiments. A person skilled in the art will understand that there may be made alterations and modifications to the embodiments that are within the scope of the invention as described in the attached claims.