Pumping system

Abstract

A pumping system for pumping a medium is described. The system comprises: at least one transverse pressure exchange chamber, but preferably multiple pressure exchange chambers. Each pressure exchange chamber has a valve arrangement at each end. The system also includes a pressurised discharge at a delivery end of the system and a filling mechanism operable to fill the pressure exchange chamber with the medium. A positive displacement pump is operable to pump a driving fluid in direct contact with the medium so that the medium is pumped from the pressure exchange chamber to the pressurised discharge. A method of pumping a medium is also described.

Claims

1. A pumping system for pumping a medium comprising a liquid with ore particles from an underground or subsea location to a surface at a raised level, the system comprising: at least one pressure exchange chamber, located at a lower altitude than the raised level, and comprising an elongate pipe which extends in a transverse orientation, and having a driving fluid valve arrangement at one end, and a pumped medium valve arrangement at an opposite end; a pressurised discharge at a delivery end of the system on the pumped medium valve arrangement side of the pressure exchange chamber; a riser extending upwardly from the delivery end to the raised level and for delivering the medium thereto; a fluid source at approximately the same level as the pressure exchange chamber to provide water to mix with ore to create the medium; a filling mechanism operable to fill the pressure exchange chamber with the medium; and a positive displacement pump connected to the pressure exchange chamber and operable to pump a driving fluid in direct contact with the medium without using a separating element so that the medium is displaced from the pressure exchange chamber to the pressurised discharge by the driving fluid.

2. The pumping system according to claim 1, wherein the driving fluid valve arrangement is located at the end of the pressure exchange chamber connected to the positive displacement pump and comprises a driving fluid entry valve, and a driving fluid exit valve and the pumped medium valve arrangement comprises a pumped fluid entry valve whereby medium can be fed into the pressure exchange chamber and a pumped fluid exit valve whereby medium can be discharged from the pressure exchange chamber, and an actuator associated with each valve and being configured to displace the valve between an open position and a closed position, the valves being configured such that the flow of pumped fluid assists in closing the driving fluid entry and driving fluid exit valves and assists in opening the pumped fluid entry and exit valves.

3. The pumping system according to claim 2, wherein the driving fluid valve arrangement further comprises a compression valve to bypass the driving fluid entry valve so that the pressure in the pressure exchange chamber can be raised prior to opening of the driving fluid entry valve and a decompression valve to bypass the driving fluid exit valve so that the pressure in the pressure exchange chamber can be lowered prior to opening of the driving fluid exit valve and a choke valve connected in series with the compression valve to limit the flow rate of driving fluid through the compression valve.

4. The pumping system according to claim 3, wherein the pumping system comprises a plurality of pressure exchange chambers connected in parallel and filled sequentially with the medium to be pumped and emptied sequentially with driving fluid.

5. The pumping system according to claim 4, wherein the pumping system further comprises a pressure exchange chamber controller operable to actuate the compression and decompression valves, the driving fluid entry and exit valves and when required the pumped fluid entry and exit valves, at the appropriate times to ensure that at least one pressure exchange chamber is full of medium when medium is discharged from a pressure exchange chamber while another pressure exchange chamber is being filled with medium.

6. The pumping system according to claim 1, wherein the positive displacement pump pumps the driving fluid in the same direction as the medium is flowing.

7. The pumping system according to claim 1, wherein the filling mechanism comprises a centrifugal pump.

8. The pumping system according to claim 1, wherein the positive displacement pump is located at approximately the same altitude as the pressure exchange chamber.

9. The pumping system according to claim 1, wherein the positive displacement pump is located at a higher altitude than the pressure exchange chamber.

10. The pumping system according to claim 1, wherein the system further comprises a driving fluid source located at approximately the same altitude as the pressure exchange chamber, wherein the driving fluid source reuses driving fluid expelled from the pressure exchange chamber during a filling step of the chamber.

11. The pumping system according to claim 10, further comprising a second positive displacement pump located at the level of the pressure exchange chamber.

12. The pumping system according to claim 1, wherein the pressurised discharge comprises either a feed to a pressurised container, or a feed into an elongate transportation line requiring a high pressure.

13. The pumping system according to claim 1, wherein the driving fluid and pumped medium valve arrangements comprise actuated, poppet, non-return valves that are oriented and configured so that: (i) a pressure differential across each valve acts on a high pressure side of the valve to assist in maintaining the valve in a closed position when the valves are not actuated, (ii) the flow direction of the driving fluid assists in closing the driving fluid valves, and (iii) the flow direction of the medium and driving fluid assists in opening the pumped medium valves.

14. The pumping system according to claim 13, wherein an actuator force is selected so that the valves only open in the presence of a small pressure differential even when actuated.

15. A method of pumping a medium comprising a liquid with ore particles from an underground or subsea location to a surface at a raised level using a system according to claim 1, the method comprising: (i) de-pressurising a pressure exchange chamber that extends in a transverse orientation and is located an altitude that is lower than a raised level; (ii) filling the pressure exchange chamber with the medium to be pumped using a relatively low pressure source; (iii) pressurising the pressure exchange chamber using a positive displacement pump; (iv) driving out the medium using a driving fluid in direct contact with the medium without using a separating element, where the driving fluid is delivered using the positive displacement pump; and (v) delaying closing pumped fluid entry and exit valves relative to driving fluid entry and exit valves to stop the flow of the medium before the pumped fluid entry and exit valves are closed, thereby allowing larger ore particles in the medium to settle away from the pumped fluid entry and exit valves before they are closed.

16. The method of pumping the medium according to claim 15 wherein step (ii) further comprises filling a pressure exchange chamber such that the medium passes through the pressure exchange chamber and out via a driving fluid exit valve.

17. The method of pumping the medium according to claim 15, wherein step (iv) further comprises driving out the medium using a driving fluid in direct contact with the medium such that the driving fluid passes through the pressure exchange chamber and out via the pumped fluid exit valve.

18. The method of pumping a medium according to claim 15, wherein the method comprises performing steps (i) to (iii) on a first pressure exchange chamber, then performing steps (i) to (iii) on a second pressure exchange chamber, before or while performing step (iv) on the first pressure exchange chamber.

19. The pumping system according to claim 1, wherein the system further comprises a driving fluid riser coupled to the positive displacement pump at the surface, and a driving fluid source located at the surface and operable to extract and reuse fluid from the medium received at the raised level so that fluid from the medium can be used as driving fluid.

20. The pumping system according to claim 19, wherein the system further comprises a fluid recovery filter for removing large particulates from fluid extracted from the medium prior to providing it to the positive displacement pump.

21. A pumping system according to claim 11, wherein the system further comprises a driving fluid riser coupled to the positive displacement pump at the surface, and a driving fluid source located at the surface and operable to extract and reuse fluid from the medium received at the raised level so that extracted fluid from the medium can be used as driving fluid, and with the second positive displacement pump configured to reuse the driving fluid discharged from the driving fluid exit valve whereby a closed loop fluid system is provided that requires very little, if any, external fluid input once it is operational because all driving fluid and fluid extracted from the medium is re-used.

22. A pumping system for pumping a medium comprising a liquid with ore particles from an underground or subsea location to a surface at a raised level, the system comprising: at least one pressure exchange chamber, located at a lower altitude than the raised level, and comprising an elongate pipe which extends in a transverse orientation, and having a driving fluid valve arrangement at one end, and a pumped medium valve arrangement at an opposite end; a pressurised discharge at a delivery end of the system on the pumped medium valve arrangement side of the pressure exchange chamber; a riser extending upwardly from the delivery end to the raised level and for delivering the medium thereto; a fluid source at approximately the same level as the pressure exchange chamber to provide water to mix with ore to create the medium; a filling mechanism operable to fill the pressure exchange chamber with the medium; and a positive displacement pump connected to the pressure exchange chamber and operable to pump a driving fluid in direct contact with the medium so that the medium is displaced from the pressure exchange chamber to the pressurised discharge by the driving fluid, wherein the driving fluid valve arrangement is located at the end of the pressure exchange chamber connected to the positive displacement pump and comprises a driving fluid entry valve, and a driving fluid exit valve and the pumped medium valve arrangement comprises a pumped fluid entry valve whereby the medium can be fed into the pressure exchange chamber and a pumped fluid exit valve whereby the medium can be discharged from the pressure exchange chamber, and an actuator associated with each valve and being configured to displace the valve between an open position and a closed position, the valves being configured such that the flow of the medium and the driving fluid assists in closing the driving fluid entry and driving fluid exit valves and assists in opening the pumped fluid entry and exit valves.

Description

BRIEF DESCRIPTION OF FIGURES

(1) These and other aspects will be apparent from the following specific description, given by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a simplified schematic diagram of a pumping system according to a first embodiment of the present invention, where the first embodiment uses only a single pressure exchange chamber, and where the pressure exchange chamber is located beneath a surface to which medium is to be pumped;

(3) FIG. 1A is a simplified schematic diagram of part of the pumping system of FIG. 1, namely the pressure exchange chamber, to illustrate valve arrangements in the chamber;

(4) FIG. 2 is a flowchart (split over two drawing sheets) illustrating the steps involved in operating the pumping system of FIG. 1;

(5) FIG. 3 is a simplified schematic diagram of the pumping system of FIG. 1 illustrating a part of FIG. 1 (the open pressure exchange system) in a generalised manner;

(6) FIG. 4 is a simplified schematic diagram of another pumping system according to a second embodiment of the present invention, where the second embodiment includes three pressure exchange chambers (in an alternative open pressure exchange system to that of FIG. 1) and an upgraded controller;

(7) FIG. 5 is a flowchart illustrating the steps involved in operating the pumping system of FIG. 4 during a filling (or back-fill) operation;

(8) FIG. 6 is a flowchart illustrating the steps involved in operating the pumping system of FIG. 4 during a discharge operation;

(9) FIG. 7 is a simplified schematic diagram illustrating a third embodiment of a pumping system having an alternative location for part (the positive displacement pump) of the pumping system of either FIG. 1 or FIG. 4; and

(10) FIG. 8 is a simplified schematic diagram illustrating a general configuration of a pumping system 810 for an underground system, with variants shown in broken line, using an underground positive displacement driving fluid injection pump in a closed circuit, according to an embodiment of the present invention.

DETAILED DESCRIPTION

(11) Reference is first made to FIG. 1, which is a simplified schematic diagram of a pumping system 10 according to a first embodiment of the present invention. In typical embodiments, most or all of the pumping system 10 is located at a lower altitude than a final delivery point at which a medium is to be delivered by the pumping system 10. In this embodiment, the medium comprises ore particles ranging in size from 1 to 100 mm located in a liquid carrier to produce a slurry of entrained and suspended ore particles.

(12) The pumping system 10 comprises a single pressure exchange chamber 12, which has a valve arrangement 14, 16 at each end thereof, namely a driving fluid valve arrangement 14 and a pumped medium valve arrangement 16.

(13) Reference is also made to FIG. 1A, which is a simplified schematic diagram of the pressure exchange chamber 12, illustrating the valve arrangements 14,16 in more detail.

(14) A pressurised discharge 20 is provided at a delivery end 22 of the system 10. In this embodiment, the pressurised discharge 20 is an inlet to a pumped medium riser 24 that extends in a generally vertical direction from the delivery end 22 to a collection receptacle 26 at a surface 28. A medium outlet line 29 is coupled between the pumped medium valve arrangement 16 and the pressurised discharge 20.

(15) A filling mechanism 30 is provided, in the form of a centrifugal pump, which is operable to fill the pressure exchange chamber 12 with a medium 32 to be pumped to the surface 28. The centrifugal pump 30 fills the pressure exchange chamber 12 with medium 32 via a medium inlet line 31.

(16) The pumping system 10 also includes a positive displacement pump 34 operable to pump a driving fluid 36 through the pressure exchange chamber 12 and in direct contact with the medium 32 so that the medium 32 is displaced from the pressure exchange chamber 12 to the pressurised discharge 20 and from there to the surface 28 via the pumped medium riser 24.

(17) The positive displacement pump 34 is coupled to the driving fluid valve arrangement 14 via a driving fluid riser 38 and a driving fluid inlet line 40.

(18) A driving fluid outlet line 42 connects the pressure exchange chamber 12 to a driving fluid discharge point 44.

(19) The combination of the pressure exchange chamber 12, the driving fluid valve arrangement 14, the pumped medium valve arrangement 16, the driving fluid inlet and outlet lines 40,42, and the medium inlet and outlet lines 31,29 is referred to herein as an open pressure exchange system 46. Open refers to the direct contact between the driving fluid 36 and the medium 32. Pressure exchange refers to the exchange of pressure between the two different fluids being pumped (driving fluid 36 and medium 32).

(20) The driving fluid valve arrangement 14 is located at a positive displacement pump end 48 and comprises a driving fluid entry valve 50, a driving fluid exit valve 52, a compression valve 54, a decompression valve 56, a choke valve 57, and a master valve actuator 58. The master valve actuator 58 is provided to actuate the various valves 50 to 56 at the correct time for efficient operation of the pumping system 10.

(21) As shown in FIG. 1A, the driving fluid entry valve 50 includes a hydraulic actuator 58a to open and close the fluid entry valve 50. Similarly, a hydraulic actuator 58b,c,d is paired with each of the driving fluid exit valve 52, the compression valve 54, and the decompression valve 56. Each of these hydraulic actuators 58a,b,c,d is controlled by the master valve actuator 58. This is not shown in FIG. 1A for clarity.

(22) In this embodiment, the master valve actuator 58 comprises a hydraulic power unit. This power unit 58 is coupled to a plurality of individual valve actuators 58a,b,c,d, one in each valve 50,52,54,56. These actuators 58a,b,c,d are operable to control their respective valves 50,52,54,56, in response to the master valve actuator 58 receiving a command from the system controller 70.

(23) In this embodiment, these valves are all high pressure (for example, greater than 40 Bar) actuated, non-return, poppet seated valves; however, in other embodiments, different types of valves may be used.

(24) The choke valve 57 (one is illustrated in FIG. 1; whereas, two are illustrated in FIG. 1A) is installed in series with the compression 54 and decompression 56 valves to limit and control the flow rate during compression and decompression of the pressure exchange chamber 12. By limiting the flow rate of the driving fluid 36 (and any medium 32 that passes through these valves 54,56), wear in the compression 54 and decompression 56 valves is reduced.

(25) In other embodiments, a separate, dedicated, choke valve may be provided for each of the compression 54 and decompression 56 valves (i.e. two choke valves may be used, as shown in FIG. 1A). The choke valves may comprise fixed geometry restrictions such as orifice plates and can be positioned up or downstream of the compression and decompression valve.

(26) To allow the entry 50 and exit 52 valves to open in a generally pressure balanced environment, a pressure balancing line 60 is provided. This pressure balancing line 60 couples the compression valve 54 and the decompression valve 56 for the pressure exchange chamber 12 in a bypass arrangement (i.e. bypassing the driving fluid entry 50 and exit 52 valves).

(27) The compression valve 54 is provided to bypass the driving fluid entry valve 50 so that the pressure in the pressure exchange chamber 12 can be raised prior to opening of the driving fluid entry valve 50; thereby reducing the force required to open the valve 50 and reducing the fluid flow rate through the driving fluid entry valve 50 upon opening. This has the advantage of prolonging the life of the driving fluid entry valve 50.

(28) Similarly, the decompression valve 56 is provided to bypass the driving fluid exit valve 52 so that the pressure in the pressure exchange chamber 12 can be lowered prior to opening of the driving fluid exit valve 52; thereby preventing high flow rates of the driving fluid 36 through the driving fluid exit valve 52 upon opening thereof.

(29) The compression 54 and decompression 56 valves are designed to open against a high pressure differential. However, these valves primarily allow flow of the driving fluid 36 (not the ore carrying medium 32 being pumped) and therefor operate on cleaner fluid (having fewer particles, or at least fewer large sized particles). This means that these valves are not subjected to undue wear.

(30) The pumped medium valve arrangement 16 is located at delivery end 22 and comprises a pumped fluid exit valve 62 (also referred to as a discharge valve), a pumped fluid entry valve 64 (also referred to as a suction or filling valve), and a master valve actuator 66 to actuate the valves 62, 64 at the appropriate time. The pumped fluid entry 64 and exit 62 valves open in a pressure balanced situation when the pressure exchange chamber 12 is properly decompressed or compressed respectively.

(31) As shown in FIG. 1A, the pumped fluid exit valve 62 includes a hydraulic actuator 66a to open and close the fluid exit valve 62. Similarly, a hydraulic actuator 66b is paired with the pumped fluid entry valve 64. Each of these hydraulic actuators 66a,b is controlled by the master valve actuator 66 (shown in broken line in FIG. 1A).

(32) In this embodiment, the master valve actuator 66 is also a hydraulic power unit. This power unit 66 is coupled to two individual valve actuators 66a,b, one in each valve 62,64. These actuators 66a,b are operable to control their respective valves 62,64, in response to the master valve actuator 66 receiving a command from the system controller 70. The pumped fluid exit 62 and entry 64 valves are suitable for use with high pressures (e.g. greater than 40 Bar).

(33) In this embodiment, the pumped fluid entry 64 and exit 62 valves are closed after closing the respective driving fluid entry 50 and exit 52 valves. In other words, the driving fluid entry valve 50 is closed before the pumped fluid exit valve 62; and the driving fluid exit valve 52 is closed before the pumped fluid entry valve 64. This has the advantage of stopping the flow of driving fluid 36 (and hence also the flow of the medium 32) before the pumped fluid entry and exit 50,52 valves are closed. This allows the larger particles in the medium 32 to settle away from the pumped fluid entry and exit valves 64,62, before closing the pumped fluid entry 64 and exit 62 valves; thereby lowering the risk of trapping large particles from the medium 32 in those valves 62,64.

(34) As shown in FIG. 1A, the entry and exit valves 50,52,62,64 are arranged such that the pressure differential across the valves 50,52,62,64 when closed assists in retaining the valves 50,52,62,64 in the closed position. For the pumped fluid entry and pumped fluid exit valves 64,62, the flow direction of the pumped fluid (the medium and the driving fluid) 36,32 assists in opening those valves 64,62. For the driving fluid entry and exit valves 50,52, the flow direction of the pumped fluid (the medium and the driving fluid) 36,32 works in the opposite way, assisting the valves 50,52 to close. This ensures proper sealing of the valves 50,52,54,56,62,64 when closed, assisted by the pressure differential without additional actuator force. The valve 50,52,54,56,62,64 will open in a near to pressure balanced condition when only a small force is applied by the actuator 58a,b,c,d and 66a,b. Small refers to small with respect to the hydraulic closing force across the valve 50,52,54,56,62,64 in the closed position with the full pressure differential between the high and low pressure parts of the system 10 being present across the valve 50,52,54,56,62,64.

(35) Opening in a near to pressure balanced condition applies to the driving fluid entry and exit valves 50,52 and the pumped fluid entry and exit valves 64,62. Opening in a near to pressure balanced situation eliminates high flow velocities in the valve 50,52,54,56,62,64 upon opening which otherwise would occur due to the high pressure differential across the valve 50,52,54,56,62,64. These high flow velocities otherwise would damage the functional sealing surfaces of the valve 50,52,54,56,62,64 because of the small abrasive particles present in both the driving fluid 36 and the pumped medium 32.

(36) The automatic opening in a near to pressure balanced situation allows the relatively small actuator force to be applied before pressure equalization is completed upon opening of the compression or decompression valve 54, 56. This significantly simplifies the system controller 70 as it does not require a pressure measurement to determine correct pressure equalization before actuating the driving fluid 36 and pumped medium 32 entry and exit valves 50,52,64,62.

(37) The compression and decompression valves 54,56 are designed to be opened when the full pressure differential is still present, hence require a larger actuator force in relation to the hydraulic closing force present from the pressure differential across them. In order to limit the flow velocity in the functional sealing surfaces of the compression and decompression valves 54,56, one or more chokes 57 can be installed either up or downstream of the individual compression and decompression valves 54,56. In this embodiment, the choke 57 is a restriction in the bypass lines, such as an orifice plate. Hereby the choking function, with its higher allowance for wear, is separated from the sealing function of the compression and decompression valves 54,56 with their lower wear allowance, lowering their requirements for wear resistance. In other words, by using a restriction (choke 57) the wear experienced by the valves 54,56 is reduced. By separating the flow velocity control function from the sealing function, it is easier to design a wear resistant part to perform the velocity control function than designing high wear resistant sealing parts that must retain complementary formations.

(38) In some embodiments the master valve actuators 58 and 66 can be combined in a single master valve actuator which controls all valve actuators 58a,b,c,d and 66a,b of all actuated valves 50,52,54,56,62,64.

(39) The pumping system 10 also includes a system controller 70 for controlling the operation of the entire system, including the pumps 30,34, the valves 50 to 56 and 62 to 64, and the master valve actuators 58,66.

(40) Each of the pumps 30, 34 needs to be provided with fluid.

(41) In this embodiment, a first (surface) fluid source 74 is provided at the surface 28 to provide water for the driving fluid 36. This provides water from the surface 28, which may be sea water or lake water for sea bed or lake bed applications, or water from a dewatering pump in underground (or open pit) mining applications. This provides the hydrostatic pressure benefit of using surface water. The fluid source 74 may include a filter for removing large particulates from the fluid prior to providing it to the positive displacement pump 34.

(42) The fluid source 74 may be used to extract and reuse fluid from the pumped medium 32 in the collection receptacle 26 so that fluid from the medium 32 can be used as driving fluid 36, optionally, with additional fluid being provided by water sourced locally (in underground or open pit applications from dewatering equipment used for pumping unwanted water from the mine, or excess water if it is readily available; in sea or lake bed applications, from surface water). In sea or lake bed applications reuse of the tailings from the medium that was pumped to the surface has the advantage of removing the requirement to dispose of tailings (unwanted fluid or particles from the medium 32) at the surface. This is because the driving fluid 36 (which contains the tailings) that is displaced from the pressure exchange chamber 12 during the pressure exchange chamber filling step (step 106 in FIG. 2, and steps 402, 406, 410 in FIG. 5) can be discharged directly onto the sea or lake bed.

(43) In this embodiment, a second fluid source 76 is provided at approximately the same level as the pressure exchange chamber 12 to provide water to mix with ore to create the medium 32. This uses local water, which may be sea water or lake water for sea bed or lake bed applications, or mine water in underground (or open pit) mining applications.

(44) Reference is now also made to FIG. 2, which is a flowchart (100) illustrating steps performed during operation of the pumping system 10.

(45) The first step illustrated (step 102) is the decompression step. In this step, the master valve actuator 58 opens the decompression valve 56 to decompress the pressure exchange chamber 12 to the pressure in the driving fluid outlet line 42, thereby allowing the driving fluid exit valve 52 and the pumped fluid entry valve 64 to be opened.

(46) The decompression step continues until a fill command is received (step 103).

(47) Once the fill command is received (which occurs once the pressure exchange chamber 12 is sufficiently decompressed), the master valve actuator 58 opens the driving fluid exit valve 52 (step 104). Master valve actuator 58 may energise the exit valve 52 during the decompression step (step 102). Due to the limited opening pressure of the valve 52, it will only open once the pressure differential has dropped to the opening pressure of the valve 52, as determined by the opening force of the master valve actuator 58. In this embodiment, it is preferred (but not essential) that the master valve actuator 58 closes the decompression valve 56 before driving fluid 36 is displaced out of the pressure exchange chamber 12 to prevent the medium 32 passing through the decompression valve 56.

(48) Once the chamber is decompressed, the master valve actuator 66 then opens the pumped fluid entry valve 64 (suction valve) and once the pumped fluid entry valve 64 (suction valve) is open, the medium 32 automatically flows into the pressure exchange chamber 12 due to the operation of the centrifugal pump 30 (step 106). Master valve actuator 66 may energise the entry valve 64 during the decompression step (step 102). Due to the limited opening pressure the valve 64 will only open once the pressure differential has dropped to the opening pressure of the valve 64, as determined by the opening force of the master valve actuator 66. The medium entering the pressure exchange chamber 12 displaces the driving fluid 36 out of the pressure exchange chamber 12 through the driving fluid exit valve 52, so that the medium 32 starts to fill the pressure exchange chamber 12. The medium 32 is pumped at a relatively high flow rate but relatively low pressure so the pressure exchange chamber 12 fills relatively rapidly.

(49) Once the pressure exchange chamber 12 is filled (which may be determined by a direct or indirect measurement or estimation of filled volume, for example by integration of the measured or estimated flow rate in time by the system controller 70) (step 108), the master valve actuator 58 closes the driving fluid exit valve 52 (step 110), thereby stopping the outflow of driving fluid 36 from the pressure exchange chamber 12 and stopping the inflow of medium 32 to the pressure exchange chamber 12.

(50) After the flow of medium 32 has stopped, the master valve actuator 66 waits for a predetermined time (step 112). In this embodiment, the wait time is 3 seconds, but in other embodiments the wait time may be selected for a time between zero seconds and ten seconds. This wait time allows larger particles in the medium 32 to settle to a lower part of the pressure exchange chamber 12 and away from the valve seat of valve 64, thereby allowing a better closure of the valve 64.

(51) The master valve actuator 66 closes the pumped fluid entry valve 64 (suction valve), after the predetermined wait time has elapsed (step 114).

(52) Once the pumped fluid entry valve 64 (suction valve) is closed, the master valve actuator 58 opens the compression valve 54 (step 116), thereby allowing high pressure driving fluid 36, delivered by the positive displacement pump 34, to enter the pressure exchange chamber 12. This compresses the contents of the pressure exchange chamber 12 to the pressure in the driving fluid inlet line 40.

(53) After compression of the pressure exchange chamber 12 has reached a sufficient level, and an empty (or start) command is received, (step 117), the master valve actuators 58, 66 open the driving fluid entry valve 50 and the pumped fluid exit valve 62 (step 118). As above, the master valve actuators 58,66 may actuate the valves 50,62 prior to pressure equalisation as the valves 50,62 will only open once the pressure differential has dropped to the opening pressure of the valves 50,62, as determined by the opening force of the master valve actuators 58,66. In this embodiment, it is preferred (but not essential) that the master valve actuator 58 closes the compression valve 54 when the pressure is equalised so that driving fluid 36 flows primarily through the driving fluid entry valve 50 rather than the compression valve 54.

(54) Once these valves 50,62 are open, driving fluid 36 flows into the pressure exchange chamber 12 through the driving fluid inlet line 40 and the driving fluid entry valve 50 due to the operation of the positive displacement pump 34 (step 120). The driving fluid 36 displaces the medium 32 through the pumped fluid exit valve 62, the medium outlet line 29, the pressurised discharge 20, and partly up the pumped medium riser 24 (depending on the height of the riser 24).

(55) Once the medium 32 is displaced into the medium outlet line 29 (which may be determined by a direct or indirect measurement or estimation of filled volume, for example by integration of the measured or estimated flow rate in time by the system controller 70) (implemented by a stop command being generated by the system controller 70, step 121), the driving fluid entry valve 50 is closed (step 122). This stops the inflow of driving fluid 36 into the pressure exchange chamber 12, and stops the outflow of medium 32 from the pressure exchange chamber 12.

(56) After the outflow of medium 32 has stopped, the master valve actuator 66 waits for a predetermined time (step 124). In this embodiment, the wait time is 3 seconds, but in other embodiments the wait time may be selected for a time between zero seconds and ten seconds. This wait time allows larger particles in the medium 32 to settle to a lower part of the pressure exchange chamber 12 and away from the valve seat of the pumped fluid exit valve 62, thereby allowing a better closure of the valve 62.

(57) In other embodiments, as an addition, or alternative, step 120 is extended so that the driving fluid 36 flows through the pumped fluid exit valve 62. This ensures that the pumped fluid exit valve 62 closes in the presence of the driving fluid 36, which may be cleaner, or may have fewer large particles, than the medium 36. In such embodiments, the pumped fluid (or medium) 32 may include some driving fluid 36. This also prevents the build-up of particles from the medium in the pressure exchange chamber 12.

(58) The master valve actuator 66 closes the pumped fluid exit valve 62 (discharge valve), after the predetermined wait time has elapsed (step 126).

(59) Once the pumped fluid exit valve 62 is closed, the sequence goes back to step 102 for decompression of the pressure exchange chamber 12 and starting a new medium fill process.

(60) Reference is now made to FIG. 3, which is a simplified schematic diagram of the pumping system 10 of FIG. 1. In FIG. 3, the open pressure exchange system 46 (that is, the pressure exchange chamber 12, the driving fluid valve arrangement 14, the pumped medium valve arrangement 16, the driving fluid inlet and outlet lines 40,42, and the medium inlet and outlet lines 31,29) is indicated generally by numeral 46.

(61) Reference is now made to FIG. 4, which is a simplified schematic diagram of another pumping system 310, according to a second embodiment of the present invention. For clarity, those parts that are common with the parts of the FIG. 1 embodiment have been removed. This pumping system 310 is very similar to pumping system 10. The main differences are that the open pressure exchange system 346 comprises three pressure exchange chambers 312a,b,c instead of one pressure exchange chamber 12, and the system controller 370 manages the sequential filling and discharge of the three pressure exchange chambers 312.

(62) Each of the three pressure exchange chambers 312a,b,c includes identical valves to those described with reference to the pumping system 10 of FIG. 1 (choke valve 57 is not illustrated in FIG. 4 for clarity, but it is included in each pressure exchange chamber 312). Each of the three pressure exchange chambers 312a,b,c, is identical (or at least very similar for all practical purposes) to the pressure exchange chamber 12 of FIG. 1. Pump system 310 also includes a pump system controller 370 that is similar to pump system controller 70 but additionally manages the sequential filling and discharge of the three pressure exchange chambers 312. The sequencing of pressure exchange chamber 312a,b,c filling and discharge may be governed primarily by timing settings in the pump system controller 370, or may be influenced by the status (or a condition) of another pressure exchange chamber 312a,b,c.

(63) By having multiple pressure exchange chambers 312 arranged in parallel, the pumping system 310 can ensure that at least one pressure exchange chamber 312 is always filled with medium 32 and ready for discharge, thereby allowing a continuous feed of driving fluid 36 to the pressure exchange chambers 312 and a continuous feed of medium 32 to the pressure exchange chambers 312.

(64) Reference is now made to FIGS. 5 and 6, which are flowcharts 400, 420 illustrating steps performed during operation of the pumping system 310 (filling and discharge, respectively).

(65) Initially, one of the pressure exchange chambers (e.g. the first pressure exchange chamber 312a) is filled using step 106 of the process 100 of FIG. 2 (step 402).

(66) The system controller 370 then allows the first pressure exchange chamber 312a to fill until step 108 (FIG. 2) is reached (step 404).

(67) Once the first chamber 312a has reached step 108 (FIG. 2), then the system controller 370 starts filling the next pressure exchange chamber 312b (step 406).

(68) The system controller 370 then allows the second pressure exchange chamber 312b to fill until step 108 (FIG. 2) is reached (step 408).

(69) Once the second chamber 312b has reached step 108 (FIG. 2), then the system controller 370 starts filling the next pressure exchange chamber 312c (step 410).

(70) The system controller 370 then allows the third pressure exchange chamber 312c to fill until step 108 (FIG. 2) is reached (step 412).

(71) The process then reverts to filling the first pressure exchange chamber 312a (step 402).

(72) With reference to FIG. 6, initially, the system controller 370 starts discharging the first pressure exchange chamber 312a using step 120 of the process 100 of FIG. 2 (step 422).

(73) The system controller 370 then allows the first pressure exchange chamber 312a to discharge until step 122 (FIG. 2) is reached (step 424).

(74) Once the first chamber 312a has reached step 122 (FIG. 2), then the system controller 370 starts discharging the next pressure exchange chamber 312b (step 426).

(75) The system controller 370 then allows the second pressure exchange chamber 312b to discharge until step 122 (FIG. 2) is reached (step 428).

(76) Once the second chamber 312b has reached step 122 (FIG. 2), then the system controller 370 starts discharging the next pressure exchange chamber 312c (step 430).

(77) The system controller 370 then allows the third pressure exchange chamber 312c to discharge until step 122 (FIG. 2) is reached (step 432).

(78) The process then reverts to discharging the first pressure exchange chamber 312a (step 422).

(79) This sequence of filling and discharging provides a gradual take-over of the filling flow from one pressure exchange chamber 312 to the next, and of the discharge flow from one pressure exchange chamber 312 to the next.

(80) To maintain an uninterrupted feed into and out of the pumping system 310 the timing of the sequence of the individual pressure exchange chambers 312 is controlled and aligned by the system controller 370.

(81) Multiple parameters can be used to control the timing of the sequence. For example, the flow rate of the driving fluid 36 can be adjusted. The flow rate of the driving fluid 36 is directly proportional to the pump speed of the positive displacement pump 34. The duration of the pressure exchange chamber discharge step (step 120) can be adjusted. In preferred embodiments, the chamber discharge step (step 120) continues after displacing the medium 32 out of the pressure exchange chamber 312 allowing the pumped fluid exit (discharge) valve 62 to close through the less contaminated driving fluid 36 rather than in the pumped medium 32.

(82) The flow rate of the filling mechanism (centrifugal pump in the above embodiments) 30 can be adjusted. The flow rate of such a pump can be changed by changing either the speed of the pump 30 itself, or by changing the pressure load on the pump 30 by using a flow control valve in the driving fluid outlet line 42. As the flow rate of a centrifugal pump is dependent on both the speed of the pump as well as the pressure load of the pump a flow rate measurement in the driving fluid outlet line 42 may be used to ascertain the actual flow rate.

(83) The duration of the chamber fill step (step 106) can be adjusted. In preferred embodiments, the chamber fill step (step 106) stops before displacing the medium 32 out of the pressure exchange chamber 312 through the driving fluid exit valve 52, allowing the driving fluid exit valve 52 to close in the less contaminated driving fluid 36 rather than in the pumped medium 32.

(84) One advantage of the pumping system 10, 310 with a direct contact between the driving fluid 36 and the pumped medium 32 is that the duration of the fill and discharge steps can be extended almost without limit. This is in contrast to the fixed end stops on the stroke in a crankshaft or hydraulic driven pump, or the pressure exchange systems using a separating element between the driving fluid and the pumped mixture. This allows great flexibility in the timing of the sequence making it very robust even if there are timing variations due to varying conditions in the pump 34.

(85) As an alternative to the embodiments of FIGS. 1 to 6, it is possible to locate the first fluid source 74 at the same level as the pressure exchange chamber(s) 12, 312. This is illustrated as low level fluid source 74 in broken line in FIG. 1. The low level fluid source 74 can reuse the driving fluid 36 expelled by the pressure exchange chamber(s) 12, 312 during the pressure exchange chamber filling step (step 106 in FIG. 2, and steps 402, 406, 410 in FIG. 5) by feeding it into the driving fluid inlet line 40, either partially (with some driving fluid provided from elsewhere) or fully (with all driving fluid provided from the fluid source 74). However, this expelled fluid is at a much lower altitude than the location of the surface positive displacement pump 34, and the driving fluid inlet line 40 is at a high pressure (fed by the positive displacement pump 34), so it would require the low level fluid source 74 to be driven by a second positive displacement pump 34 located at the level of the pressure exchange chamber 12 (shown in broken line FIG. 1). The second positive displacement pump 34 may be used to deliver all of the driving fluid, negating the requirement for a surface positive displacement pump 34 (as shown in FIG. 7). This has advantages in underground mine locations where there is water available at the underground level for creating the slurry mix, and excess water from the pumped medium can be removed and disposed of at the surface. This would lower the mine dewatering requirements that most underground mines already have.

(86) It is possible to combine the surface fluid source 74 configured to extract and reuse fluid from the pumped medium 32 so that fluid from the medium 32 can be used as driving fluid 36, with the second positive displacement pump 34 configured to reuse the driving fluid 36 discharged during the pump filling chamber step (step 106 in FIG. 2, and steps 402, 406, 410 in FIG. 5) so that a theoretically closed loop fluid system is provided that does not require any (or only very little) external fluid input once it is operational because all driving fluid 36 and medium 32 fluid is re-used (shown by solid lines in FIG. 8). In this example, the second positive displacement pump 34 compensates for the shortage of driving fluid 36 coming from the dewatering of the medium 32 at the surface 28. The use of positive displacement driving fluid pumps 34, 34 allows this parallel driving fluid pump installation which would be much more difficult to do with parallel centrifugal driving fluid pumps as the pressure sensitivity of the flow rate would result in interaction between the individual centrifugal pumps.

(87) Reference will now be made to FIG. 7, which is a simplified schematic diagram illustrating a third embodiment of a pumping system 710 having an alternative location for part (the positive displacement pump) of the pumping system of FIG. 1 or FIG. 4.

(88) In the first and second embodiments (FIGS. 1 to 6), the positive displacement pump 34 is located at the surface 28, significantly higher than the pressure exchange chamber(s) 12, 312. For example, the surface 28 may be from 50 m to 5000 m higher in altitude than the pressure exchange chamber 12. However, it is possible to locate the positive displacement pump at approximately the same level (or altitude or depth) as the pressure exchange chamber 12 or chambers 312. This is illustrated as low level positive displacement pump 734 in FIG. 7.

(89) This has the advantage that the positive displacement pump 734 is located near to the pressure exchange chamber(s) 12, 312 thereby improving load response time when switching between pressure exchange chambers 312. Another advantage is that a driving fluid riser (riser 38 in FIG. 1) is not required as the driving fluid 36 can be provided by the low level fluid source 74. Alternatively, a driving fluid riser may be used to provide the driving fluid 36 from the surface 28 directly to positive displacement pump 734. This has the advantage that the hydrostatic pressure in the driving fluid riser creates a high suction pressure on the positive displacement pump 734 reducing its energy consumption.

(90) Where the pressure exchange chamber(s) 12, 312 are located underground (as opposed to on a sea or lake bed), the positive displacement pump 734 has to deliver the full power to overcome the pressurised discharge 20 (i.e. to lift the medium 32 to the surface 28). Where the pressure exchange chamber(s) 12, 312 are located on a sea (or lake) bed, the surrounding water can be used as the driving fluid 36, and this has hydrostatic pressure based on the depth of the water, so the positive displacement pump 734 only has to overcome the pressure difference due to the density difference of the sea water and the medium 32 in the pumped medium riser 24, plus the frictional losses in the pumped medium riser 24.

(91) Alternatively, in a similar way as described with reference to FIG. 1, the driving fluid 36 may be supplied from a surface fluid source 74 via a driving fluid riser 38.

(92) Providing the positive displacement pump 34 at the same level as the pressure exchange chambers 312 has the disadvantage that it may be expensive to provide a high energy power source where the pressure exchange chambers 312 are located (e.g. down a mine or on a sea bed).

(93) It will now be appreciated that the positive displacement pump 34 may be located at the surface 28 or at a negative altitude. Similarly, the driving fluid 36 may be provided from the surface 28 or from the negative altitude, or a combination of the two.

(94) Reference will now be made to FIG. 8, which is a simplified schematic diagram illustrating a general configuration of a pumping system 810, with variants shown in broken line, for an underground system using an underground positive displacement driving fluid injection pump in a closed circuit, according to an embodiment of the present invention. The pumping system 810 includes the open pressure exchange system 46,346 as described above.

(95) In FIG. 8, C.sub.v refers to the volumetric concentration of solids in a slurry and Q_up refers to the total flowrate that the pumping system 810 delivers. The surface fluid source 74 is illustrated as a water tank at atmospheric pressure. This (first) surface fluid source 74 may be fed by any readily available water (illustrated by box 74) from the surface of a sea, lake, or pond, or from dewatering equipment when required depending on which system variant is used.

(96) A broken line box 811 is shown around the second positive displacement pump 34 (or in some embodiments, the only positive displacement pump 34) and the second fluid source 76. In underground (not sea or lake bed) environments, the second fluid source 76 is required to capture fluid from the open pressure exchange system 46,346, otherwise the discharged driving fluid would flood the area. In such applications, the second fluid source 76 can feed a slurry preparation mixer 813 that mixes fluid from the second fluid source 76 with ore that has been mined (not shown). The embodiments of FIGS. 1, 3, and 7 also include a slurry preparation mixer 813, but it is not shown on those figures for clarity. In sea or lake bed environments, the second fluid source 76 is not required, because there is no need to capture fluid from the open pressure exchange system 46,34, because it can be discharged to the sea or lake water around the pressure exchange chamber 12,312.

(97) FIG. 8 also shows an underground fluid source 876 (which may be a pond or tanks used for holding water) that can be used for supplying any fluid shortage, or receiving any excess fluid when required depending on which system variant is used.

(98) The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate.

(99) The terms comprising, including, incorporating, and having are used herein to recite an open-ended list of one or more elements or steps, not a closed list. When such terms are used, those elements or steps recited in the list are not exclusive of other elements or steps that may be added to the list.

(100) Unless otherwise indicated by the context, the terms a and an are used herein to denote at least one of the elements, integers, steps, features, operations, or components mentioned thereafter, but do not exclude additional elements, integers, steps, features, operations, or components.

(101) The presence of broadening words and phrases such as one or more, at least, but not limited to or other similar phrases in some instances does not mean, and should not be construed as meaning, that the narrower case is intended or in instances where such broadening phrases are not used.

(102) In other embodiments, the filling mechanism 30 may comprise a dredge pump, or any other convenient pump.

(103) The reference numerals and corresponding parts that are used herein are provided below: 10 pumping system 12 pressure exchange chamber 14 driving fluid valve arrangement 16 pumped medium valve arrangement 20 pressurized discharge 22 delivery end 24 pumped medium riser 26 collection receptacle 28 surface 29 medium outlet line 30 filling mechanism 31 medium inlet line 32 medium (slurry pumped) 34 positive displacement pump 34 second positive displacement pump 36 driving fluid 38 driving fluid riser 40 driving fluid inlet line 42 driving fluid outlet line 44 driving fluid discharge point 46 open pressure exchange system 48 positive displacement pump end 50 driving fluid entry valve 52 driving fluid exit valve 54 compression valve 56 decompression valve 57 choke valve 58 master valve actuator (for valves 50 to 56) 60 pressure balancing line 62 pumped fluid exit valve 64 pumped fluid entry valve 66 master valve actuator (for valves 60, 62) 70 system controller 72 second positive displacement pump 74 surface fluid source 74 low level fluid source 76 second fluid source 100 flowchart 310 alternative pumping system 312a,b,c pressure exchange chambers 346 open pressure exchange system (3 chambers) 370 system controller 400 flowchart for filling the pressure exchange chamber 310 420 flowchart for discharging the pressure exchange chamber 310 710 pumping system 734 low level positive displacement pump 810 pumping system 811 box with optional components 813 slurry preparation mixer 876 underground fluid source