Apparatus and Method for Facilitating a Hydrostatic Pressure Increase in a Fluid Flowing in a Pipe

Abstract

There is described an apparatus (1) and a method to facilitate a hydrostatic pressure increase in a fluid flowing in a first pipe (22), where the hydrostatic pressure increase is provided by means of a pumping device (3) being supplied with energy, the apparatus including: —an energy harvester (5) arranged to be able to draw a portion of an energy carried by a fluid flowing in a second pipe (28); and —a mechanical or hydraulic energy transfer device (9, 60) arranged to be able to transfer a portion of the energy absorbed by the energy harvester (5) to the pumping device (3).

Description

The present invention relates to an energy transfer device for fluid in motion. More particularly the invention relates to an apparatus and a method for facilitating a hydrostatic pressure increase in a fluid flowing in a first pipe, where the hydrostatic pressure increase is provided by means of a pumping device being supplied with energy.

The fluid may be a liquid or a gas or a combination thereof.

In processes where there is a need to drive the fluid through a pipe, the fluid is typically driven by means of a pumping device transferring energy to the fluid so that it for example receives the necessary hydrostatic pressure increase. Examples of such processes are: cooling systems in the process industry wherein cooling water is driven through one or more heat exchangers; water circulation systems for land based fish farms where fresh seawater is pumped up into a basin and where corresponding amounts of water is dumped to sea; and in plants converting seawater to freshwater by means of reversed osmosis, where a portion of supplied water is returned to the sea.

Common for the above exemplary processes is that the fluid being “returned” from the process carries energy, which at the present is not utilised to contribute to be able to achieve the desired pressure increase.

From the publication WO 2008084560 is known an apparatus meant to facilitate a hydrostatic pressure increase in a fluid flowing in a first pipe, where the hydrostatic pressure increase is provided by means of a pumping device being supplied with energy from an energy harvester flowing in a second pipe.

From the publications US 2008/0219831 and WO 2007071975 are known energy harvesters arranged for being able to draw a portion of the energy being carried by a fluid flowing in a pipe.

The object of the invention is to remedy or reduce at least one of the disadvantages of the prior art.

The object is achieved by the features disclosed in the below description and in the subsequent claims.

In a first aspect of the present invention there is provided an apparatus to facilitate a hydrostatic pressure increase in a fluid flowing in a first pipe, where the hydrostatic pressure increase is provided by means of pumping device being supplied with energy, the apparatus including: an energy harvester arranged to be able draw a portion of an energy being carried by a fluid flowing in a second pipe; and a mechanical or hydraulic energy transfer device arranged to be able to transfer to the pumping device a portion of the energy absorbed by the energy harvester, the pumping device and the energy harvester being located in a common housing.

Thus, a portion of the energy carried by the fluid in the second pipe is utilised to drive the pumping device. Thereby is required a pump motor which only need to be fed an amount of energy corresponding to the difference between the energy required to pump the fluid to the desired hydrostatic pressure and the energy being fed to the pumping device from the energy harvester.

One type of energy harvester having turned out to be particularly useful is a so-called differential pressure turbine of the type described in the Norwegian patents NO 326540 and

NO 325981 whose inventors are the same as in the present invention. Said patents relate to an apparatus including two impellers. It is however to be understood that the apparatus according the present invention may have only one impeller. A differential pressure turbine including a so-called lobe pump has in experiments turned out to be very well suitable for the purpose.

A lobe pump may also constitute the pumping device of the apparatus.

The energy transfer device may for example be a shaft, a belt transmission or an impeller, all of which provide more or less direct contact between the energy harvester and the pumping device. In the following such transmissions will be denoted mechanical transmissions.

A hydraulic pump known per se may constitute the energy transfer device, the pump being connected to the energy harvester. The hydraulic pump is hydraulically connected to a hydraulic motor known per se arranged to be able to drive the pumping device according to the present invention. In the following such a transmission will be called a hydraulic transmission.

A hydraulic energy transfer device may be an alternative to a mechanical energy transfer device when the latter is not appropriate or practically possible e.g. due to distance and/or obstacles between the energy harvester and the pumping device.

In one embodiment a rigid shaft being common for the pumping device and the energy harvester constitutes the energy transfer device. The rotational speed of the energy harvester will then be the same as the rotational speed of the pumping device. Placing the pumping device and the energy harvester on a common rigid shaft will be most appropriate when the fluid flow speed in the supply line is the same as the fluid flow speed in the return line. The energy that possibly has to be fed to the pumping device from en external power source such as a power grid is reduced approximately corresponding to the energy transmitted via the rigid shaft from the energy harvester.

The common housing in which the pumping device and the energy harvester according to the present invention are located, may be provided with an inlet and an outlet for the first pipe, an inlet and an outlet for the second pipe, and an impeller being common for the first pipe and the second pipe so that the energy transfer device is constituted by the impeller. The advantage of this is that the design may be compact and mechanically very simple.

In a second aspect of the present invention there is provided a method to facilitate hydrostatic pressure increase in a fluid flowing in a first pipe, where the hydrostatic pressure increase is provided by means of a pumping device being supplied with energy, where at least a portion of the energy for the pumping device is generated by means of an energy harvester arranged to be able to draw a portion of an energy carried by a fluid flowing in a second pipe, where the energy is transferred mechanically or hydraulically between the energy harvester and the pumping device, and where the energy harvester and the pumping device being located in a common housing.

A third aspect of the invention concerns the use of a pressure reduction device allocated to a second petroleum well to drive a pumping device allocated to a first petroleum well. The pressure reduction device corresponds to the energy harvester discussed under the first and second aspect of the invention.

In the third aspect the pumping device may be supplied with energy only from the pressure reduction device. A pump motor driven by electric power will then not be necessary.

In the following is described an example of a preferred embodiment illustrated in the accompanying drawings, wherein:

FIG. 1 shows a principle sketch of a land-based fish farm wherein seawater is circulated through the fish farm plant;

FIG. 2 shows a principle sketch of a plant where a fluid is supplied to a process unit from a supply line and where two discharge lines extend from a downstream side of the process unit;

FIG. 3 shows a principle sketch of two wells where the apparatus of the invention is used in connection with well control;

FIG. 4 shows a principle sketch of a cooling water plant for process equipment placed onboard an offshore rig, where cooling water is pumped up from the sea and heat exchanged with a cooling medium onboard the rig before the cooling water is returned to sea;

FIG. 5a shows in a larger scale a view of a combined energy harvester and pumping device located in a common housing; and

FIG. 5b shows a cross-section through the line A-A in FIG. 5a.

Similar or corresponding elements are indicated in the figures with the same reference numeral.

It is to be emphasized that the figures are only principle sketches and that mutual proportions between the various elements may be strongly distorted.

Any position indications such as under, over, lower, upper, right and left refers to positions that the various elements have in the accompanying figures.

In the figures the reference numeral 1 denotes an apparatus according to the present invention. The apparatus 1 includes a pumping device 3 connected to an energy harvester 5 and a pump motor 7. The pumping device 3 is connected with the energy harvester 5 by means of connecting device 9 being a shaft 9 in the embodiment shown.

The connection is arranged to be able to be selectively broken by a not shown means known per se. It has turned out to be advantageous if the connection device 9 is provided with a clutch device to thereby be able to achieve a “soft” connection or disconnection between the pumping device 3 and the energy harvester 5.

The apparatus 1 in FIG. 1 is arranged to be able to pump water from a sea 20 through a supply line 22 to a vat 24 placed on a shore 25. The vat 24 may be such as a basin for farming of aquatic organisms such as fish, mussels or crustaceans.

To provide a possibility for renewal of the water 26 in the vat 24, it is provided with a drain line 28 extending from the vat 24 and back to the sea 20.

In a fish farm of the type shown, it is normal to pump water from the sea more or less continuously to provide the best possible growing up conditions for the aquatic organisms in the vat 24. Over time the rate of water being supplied to the vat 24 by means of the pumping device 3 through the supply line 22 must correspond to the rate of water being drained from the vat 24 through the drain line 28.

The water being drained from the vat 24 carries energy. By leading the drain water through the energy harvester 5, a portion of the energy is drawn from the drain water and is transferred by means of the shaft 9 to the pumping device 3. The energy that must be supplied to the pumping device 3 from the pump motor 7 is thereby reduced with a quantity corresponding to the energy supplied to the pumping device 3 from the energy harvester 5.

In FIG. 2 the reference numeral 24 indicates a process plant for providing freshwater from the sea by means of reverse osmosis. The process itself will be well known to a person skilled in the art and will therefore not be described further here.

Seawater is pumped by means of the pumping device 3 through the line 22 into the process plant 24. The flow rate in the line 22 is F1. Seawater processed in the process plant 24 flows out of the process plant 24 in two lines indicated with the reference numerals 28, 28′. The flow rate in the lines 28, 28′ is F2 and F3 respectively, and their sum corresponds to the flow rate F1 in the line 22.

The pump 3 may for example be arranged for produce a flow rate F1 of 400 l/sec having a liquid pressure of 70 bar. Downstream of the apparatus 24 the flow rate F2 may for example be 300 l/sec having a liquid pressure of 70 bar. The flow rate F3 must then be 100 l/sec. The pressure in the liquid flowing in the line 28′ may for example be 1 bar. A person skilled in the art will understand that the liquid in the line 28 is so-called brine, while the liquid in the line 28′ is freshwater.

The pump 3 must transfer relatively large quantities of energy to the seawater being pumped into the process plant 24. In the above example the liquid F2 flowing in the line 28 has 75% of the energy of the liquid being between the pump 3 and the process plant 24.

To utilise a portion of the energy in the liquid flow F2, the energy harvester 5 is allocated to the line 28.

The energy harvester 5 is mechanically connected to the pumping device 3 by means of a rigid shaft 9.

The energy having to be supplied to the pumping device 3 from the pump motor 7 is reduced by an amount corresponding to the energy supplied to the pumping device 3 from the energy harvester 5.

In FIG. 3 is shown a principle sketch of a portion of a first well pipe 22 having a first well pressure P_L and an adjacent second well pipe 28 having a second well pressure P_H.

In the embodiment the second well pressure P_H is too high and has to be reduced. This is a relatively common situation in the petroleum exploitation industry. The first well pressure P_L is however too low to be able to lift the well stream up to the surface. To remedy this situation there is a need to reduce the gravity induced pressure drop in the well.

In the embodiment shown a pumping device 3 is allocated to the first well pipe 22 to relieve the static pressure from the fluid column in the well pipe 22.

The second well pipe 28 is provided with an energy harvester 5. The energy harvester 5 may for example be constituted by a differential pressure turbine having the purpose to reduce the well pressure downstream of the energy harvester 5, this being achieved by draw energy from the well stream. This energy is transferred by means of an energy transmission device 9 to the pumping device 3. In FIG. 3 the energy transmission device 9 is shown as a rigid shaft.

Thus, a pressure-reducing device that is allocated to a second petroleum well is used to drive a pumping device allocated to a first petroleum well.

As an alternative to said rigid shaft 9, the energy harvester 5 may be allocated an energy converter (not shown) such as a generator for producing electric power. The electric power may be transferred via a cable to an electric motor allocated to the pumping device 3.

In FIG. 4 is shown a production rig supported by a seabed 30 by means of a support structure 32. The support structure 32 extends from the seabed 30 through a sea surface 20 to the underside of the rig.

The rig is provided with four decks, a lower deck 34, an upper deck 36, a first intermediate deck 38, and a second intermediate deck 38′.

On the lower deck 34, the first intermediate deck 38 and the upper deck 36 there is placed a total of four cooling water users all of which, for the sake of simplicity, being denoted by reference numeral 40. The cooling water users 40 may for example, but not limited to, be heat exchangers, motors, vanes, process plants or other equipment from which heat has to be removed.

To supply the cooling water users 40 with cooling fluid, the rig is provided with a supply line 22 including supply loops 22′. The supply loops 22′ are fluid-wise connected to each of the cooling water users 40 such that cooling water from the supply line 22 is circulated through these by means of an apparatus 1 of the present invention.

The apparatus 1 shown in principle in FIG. 4, is of a type wherein a pump and an energy harvester are placed in a common housing 53 (see FIG. 5B), and wherein an impeller constitutes the energy transfer device. The apparatus 1 in FIG. 4 is shown in greater detail in FIGS. 5a and particularly FIG. 5b.

To be able to bring cooling water up to the cooling water users 40, a valve 42 is placed in a downstream portion of the supply line 22 after the last branch to the supply loops 22′.

The flow direction of the cooling water is shown with arrows.

The cooling water having been supplied with heat from the cooling water users 40 flows in the supply loops 22′ to a return or drain line 28.

The drain line 28 is fluid-wise connected to the energy harvester of the apparatus 1. The kinetic energy of the cooling water in the drain line 28 as it flows through the energy harvester is transferred via said impeller to the pumping device of the apparatus 1.

The energy that has to be supplied from a pump motor 7 to the pumping device of apparatus 1 is thereby reduced with an amount corresponding to the energy supplied to the pumping device from the energy harvester.

In an end portion 28′ of the drain line 28 the cooling water discharges freely over the sea surface 20.

FIG. 5a shows a side view of an apparatus 1 according to one embodiment of the present invention, but without a possible pump motor which may be connected to a centrally arranged shaft 61. FIG. 5b shows a section through the line A-A in FIG. 5a.

The apparatus 1 includes a housing 53 provided with two mutually spaced apart parallel bores 52, 58. The bores 52, 58 extend through a chamber 55 in the housing 53. The bores 52, 58 are arranged to be connectable to for example the supply line 22 and the drain line 28 respectively, shown in FIG. 4.

An impeller 60 is rotatably mounted in the chamber 55. The impeller 60 includes the central shaft 61. A drum 63 provided with six vanes 65 encloses the shaft 61. The vanes 65 are arranged to be able to be displaced in a vane chamber 66 formed in the drum 63, in a direction towards and away from the shaft 61 of the impeller 60. The purpose of the displaceable vanes 65 is among other things to provide two essentially separate chamber portions to thereby limit leaking, via the chamber 55, of fluid flowing in the bores 52, 58.

The movement and guiding of the vanes 65 past the bores 52, 58 may be controlled in a way known per se, for example as suggested in Norwegian patent application NO 20092085 appurtenant the present applicant.

To provide a flow F1 through the bore 52, the impeller 60 must be supplied with energy to be set in rotation R. The impeller 60 thus drives the fluid through the bore 52 and further in for example the supply line 22 shown in FIG. 4.

A fluid flow F2 being led through the bore 58 from for example the drain line 28 shown in FIG. 4 will contribute to rotation of the impeller 60.

The energy that has to be supplied to the impeller 60 from the motor 7, see for example FIG. 4, to provide the desired flow and hydrostatic pressure increase, is thereby reduced corresponding to the amount of energy supplies to the impeller from the fluid flow F2.

The present invention thus provides an apparatus, which in a simple manner will be able to facilitate hydrostatic pressure increase for a fluid flowing in a first pipe, by means of a device utilising energy present in a second pipe. The apparatus of the invention is simple and may easily be integrated in already existing piping systems as well as in new piping systems.

Claims

1. An apparatus (1) to facilitate a hydrostatic pressure increase in a fluid flowing in a first pipe (22), where the hydrostatic pressure increase is provided by means of a pumping device (3) being supplied with energy, the apparatus including:

an energy harvester (5) arranged to be able to draw a portion of an energy carried by a fluid flowing in a second pipe (28); and

a mechanical or hydraulic energy transfer device (9, 60) arranged to be able to transfer to the pumping device (3) a portion of the energy absorbed by the energy harvester (5), characterised in that the pumping device and the energy harvester (5) being located in a common housing (53).

2. An apparatus according to claim 1, wherein the energy harvester (5) is constituted by a volumetric differential pressure turbine.

3. An apparatus according to claim 1, wherein the energy transfer device (9, 60) is selected from one of or a combination of the group consisting of: a shaft; a belt drive; an impeller; a hydraulic transmission.

4. An apparatus according to claim 1, wherein the housing (53) is provided with an inlet and an outlet for the first pipe (22), an inlet and an outlet for the second pipe (28), and an impeller (60) being common for the first pipe (22) and the second pipe (28) such that the energy transfer device (9, 60) is constituted by the impeller (60).

5. An apparatus according to claim 1, wherein the first pipe (22) is arranged upstream of a process plant (24) for reverse osmosis and wherein the second pipe (28) is arranged downstream of said process plant (24).

6. An apparatus according to claim 1, wherein the first pipe (22) is arranged upstream of a liquid container (24) for storage of aquatic organisms in a land-based fish farm and wherein the second pipe (28) is a drain pipe for said liquid container (24).

7. An apparatus according to claim 1, wherein the first pipe (22) is a supply pipe for cooling water for a process plant (40) and the second pipe (28) is a discharge pipe for the cooling water.

8. An apparatus according to claim 1, wherein the pumping device (3) is arranged in connection with a first well pipe (22) having a fluid at a first well pressure and the energy harvester (5) is arranged in connection with a second well pipe (28) having a fluid at a second well pressure, the first well pressure is less than the second well pressure.

9. A method to facilitate a hydrostatic pressure increase in a fluid flowing in a first pipe (22), where the hydrostatic pressure increase is provided by means of a pumping device (3) being supplied with energy, wherein at least a portion of the energy for the pumping device (3) is generated by means of an energy harvester (5) arranged to be able to draw a portion of an energy carried by a fluid flowing in a second pipe (28), where the energy is transferred mechanically or hydraulically between the energy harvester (5) and the pumping device (3), characterised in that the energy harvester (5) and the pumping device (3) being located in a common housing (53).

10. Use of a pressure reducing device (5) allocated to a second petroleum well (28) to drive a pumping device (3) allocated to a first petroleum well (22).