Patent Description:
In the minerals processing industry, one problem relates to transporting ore from underground or subsea locations to a surface level. A novel system for such transportation has been described in PCT application number <CIT>, and is referred to as an HOHS. Other types of HOHS are also available.

One type of HOHS comprises a Positive Displacement (PD) pump, which is used to displace a mixture of ore and water, referred to as ore slurry, into a riser via a Pressure Exchange Chamber (PEC) using a driving fluid. A slurry is a two-phase mixture (a liquid with solid particles suspended or otherwise located therein). A specific advantage of the HOHS as described in PCT/IB2019/<NUM> is the use of a PD pump, which delivers a pressure independent flowrate and allows the use of a driving fluid containing fine particles (typically smaller than <NUM>).

A typical high-level schematic diagram of the HOHS system for use in subsea applications is shown in <FIG> showing both the equipment used and, to some extent, the process flow. After the ore slurry is pumped through the riser <NUM> to the surface, the ore slurry is dewatered (at location <NUM>), and the carrier fluid is re-used again by the PD pump <NUM> as driving fluid in high pressure line <NUM>. In <FIG>, Cv is the volumetric concentration of solids, and Q_up is the total volumetric flowrate of the mixture of fluid and solids delivered to the surface. Additional fluid of the same volume as the removed ore (i.e. Cv x Q_up) is added to a surface driving fluid tank to maintain balanced volumes.

One challenge in the design of the HOHS system, particularly in maritime (subsea) applications, is that the ore input to the ore slurry preparation stage <NUM> is in the form of soft polymetallic nodules, typically between <NUM> and <NUM> long. These soft nodules are easily broken, and once broken the fines that are produced are much more expensive to dewater and process than if the entire nodule was transport intact.

<CIT> discloses a hydraulic ore hoisting system using a positive displacement pump.

<CIT> discloses a pressure exchanger for gas processing that includes a rotor including rotor ducts extending parallel to an axis, a first end cover disposed at a first side of the rotor, and a second end cover disposed at a second side of the rotor.

<CIT> discloses apparatus and methods for reducing pressure exchanger manifold resonance. The apparatus includes a plurality of pressure exchangers each having a high-pressure inlet fluidly connected with a first manifold and a high-pressure outlet fluidly connected with a second manifold.

It is among the objects of an embodiment of the present invention to obviate or mitigate the above disadvantage or other disadvantages of the prior art or to provide a useful alternative to the prior art, or improved operation thereof.

The various aspects detailed hereinafter are independent of each other, except where stated otherwise. Any claim corresponding to one aspect should not be construed as incorporating any element or feature of the other aspects unless explicitly stated in that claim.

Reference in this specification to any prior publication (or information derived from the prior publication), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from the prior publication) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates, or is even citable as prior art against this application.

According to a first aspect, there is provided a pumping system for pumping a medium comprising ore suspended in carrier fluid from an underground or underwater location to a surface at a raised level, the system comprising: (i) at least one pressure exchange chamber comprising a fluid container having a valve arrangement at each end and being located at a lower altitude than the raised level; (ii) a medium inlet at one end of the chamber operable to receive a low pressure medium for transport into the chamber; characterised by (iii) a filling pump located at an opposite side of the chamber to the medium inlet, and being operable to draw medium from the medium inlet at low pressure, through the chamber, and towards the filling pump to fill the chamber without the medium in the chamber having come into contact with the filling pump.

The medium may comprise a fluid having a different property to another fluid which is driven by the medium. The different property may be temperature, salinity, solid content.

The fluid container may comprise any convenient shape and having an inlet at one end and an outlet at another end. The fluid container may comprise a pipe. The pipe may have any convenient cross-sectional shape (in some embodiments the pipe has a generally circular cross-section) and any convenient aspect ratio (length to width). In some embodiments the pipe may be elongate.

The filling pump may comprise a centrifugal pump. Alternatively, the filling pump may comprise a positive displacement pump or another type of pump.

The filling pump is preferably in direct pressure connection (or in direct pressure relation) with the pressure exchange chamber driving fluid outlet such that reducing the pressure at the filling pump results in a reduced pressure at the pressure exchange chamber driving fluid outlet. In other words, the chamber and filling pump form a closed pressure system. In such a system, there is no opening to ambient that would allow fluid at ambient pressure to be drawn in instead of the medium.

The pumping system may further comprise a harvester coupled to the medium inlet for suppling medium thereto. The harvester may create the medium comprising ore suspended in carrier fluid.

A driving fluid pump (such as a positive displacement pump, or one or more centrifugal pumps) may be provided to drive the medium from the pressure exchange chamber(s) up a discharge riser to a surface level. The discharge riser may be located at an end of the pressure exchange chamber(s) opposite the driving fluid pump. The driving fluid pump may be coupled to the pressure exchange chamber via a driving fluid riser.

The harvester may comprise a hydraulic suction device operable to lift ore in the form of nodules from the sea bed and to mix the nodules with sea water to create the medium.

The nodules may comprise particles that are typically between <NUM> and <NUM> in length. The medium may comprise settling particles in a carrier fluid which mixture is referred to as a settling slurry.

The pumping system may comprise a plurality of pressure exchange chambers, each successively filled with the medium. Each pressure exchange chamber includes a fluid container, such as a pipe that is optionally elongate or extended in any convenient configuration, such as a helix, or orientation, such as horizontal, vertical, or at any desired angle. In some embodiments, the pipe length may be selected from the range of <NUM> to <NUM>.

The (or each) pressure exchange chamber may include a separator between driving fluid and the medium being pumped, or the driving fluid may be in direct contact with the medium being pumped.

A first valve arrangement is preferably located at one end of the pressure exchange chamber and comprises a driving fluid entry valve, a driving fluid exit valve, a compression valve, and a decompression valve. These valves are preferably suitable for use with high dynamic pressures (e.g. greater than <NUM> Bar (4MPa)) as there may be a significantly higher pressure above a valve (above the sealing point on the valve seat) than beneath the valve (below the sealing point on the valve seat).

These valves may comprise actuated valves.

A second valve arrangement is preferably located at an end of the pressure exchange chamber near to a pressurised discharge and comprises a pumped fluid (or medium) exit valve (also referred to as a discharge valve) and a pumped fluid (or medium) entry valve (also referred to as a suction valve). The pumped fluid entry and pumped fluid exit valves open in a pressure balanced situation when the pressure exchange chamber is properly decompressed or compressed respectively. These valves may comprise actuated valves or self-actuated valves.

The pumped fluid exit and entry valves are preferably suitable for use with high pressures (e.g. greater than approximately <NUM> Bar (4MPa)).

The driving fluid entry valve may be opened at the same time (or approximately the same time) as the pumped fluid exit valve, during which time the driving fluid exit valve and the pumped fluid entry valve remain closed.

Similarly, the pumped fluid entry valve may be opened at the same time (or approximately the same time) as the driving fluid exit valve, during which time the pumped fluid exit valve and the driving fluid entry valve remain closed.

The underwater location may be seabed or the bed of a lake or estuary.

By locating the filling pump at the opposite end of the pressure exchange chamber to the medium inlet (or the harvester), the medium (and particularly the nodules) does not come into contact with any moving or static part in the filling pump. In embodiments where a centrifugal pump is used, the impeller is particularly destructive to ore particles in the medium. In effect, the filling pump sucks the medium from the medium inlet (and the harvester if one is connected) and into the pressure exchange chamber. The second valve arrangement may be closed before the medium comes into contact with the filling pump. If nodules were allowed to contact the impeller (or any other part of the pump) there is a significant risk of the nodules breaking down into fine particles, which are more difficult and costly to dewater at the surface.

Another advantage of locating the filling pump at the opposite end of the fluid container to the medium inlet (or the harvester) is that it is easier to control the flow rate of the medium because relatively clean water is being pumped (rather than slurry).

Another advantage of locating the filling pump at the opposite end of the fluid container to the medium inlet is that it prevents or minimises wear of the filling pump by the medium being transported.

Another advantage of the medium not coming into contact with the filling pump is that a pump can be used that does not tolerate ore particles that may be suspended in the medium.

Another advantage of the medium not coming into contact with the filling pump is that when the medium comprises ore particles suspended in water, the pump essentially pumps water so that the pump performance matches theoretical pump curve performance more closely than when pumping slurry (ore suspended in water). This makes it easier to control the pump flow velocity.

Placing the feed pump downstream of the PEC is not normally possible in a land based system. This is because in a land based system, hydraulic losses in the suction system (between the pump inlet and the source of the medium) lower the pressure throughout the suction system, including at the inlet of the pump. If the pressure at the inlet of the pump drops to, or near, the vapour pressure of the medium, then cavitation will result. The vapor pressure at room temperature is near to absolute vacuum which means that the pressure reduction in the suction system is limited to approximately <NUM> bar (100kPa). When the suction losses are too high, the vapor pressure is reached locally in the suction system. Vapor bubbles are then formed which are transported in the flow. These bubbles violently collapse when the pressure is locally increased above the vapor pressure. This typically occurs in the pump. This process is called cavitation and limits operation of the pump as flow and pressure generation under cavitation conditions is limited and cavitation can be very destructive to the pump itself.

In land based pump system design, the pump is therefore located as close as possible to the medium source and the suction system is designed for minimum hydraulic losses. The objective is to have a NPSHA (Nett Positive Suction Head Available) of the suction system which is higher than the NPSHR (Nett Positive Suction Head Required) of the pump. As the atmospheric pressure at subsea is much higher than on land (<NUM> bar per <NUM> depth), risk for cavitation is minimised or practically non-existent. Understanding of this physical difference allows the feed pump to be placed anywhere along the line from slurry preparation to water outlet of the pressure exchange chamber.

Another advantage of locating the filling pump at the opposite end of the chamber to the harvester is that it is easier to control the flow rate of the medium <NUM>. The flow rate of a centrifugal pump is dependent on both the pressure load acting on the pump as well as the density of the mixture and the presence of particles in the mixture. To control the flow rate of the feed pump its flow rate needs to be measured with a flowmeter which value can be used as the actual value in a control loop of the centrifugal pump speed. Increase of centrifugal pump speed will result in increased pressure generation by the pump which will result in increase in flow rate.

A difficulty in prior art systems is the location of the flow sensor and the disturbances of the mixture composition on the control behaviour. Ideally the flowmeter should be positioned as close to the centrifugal pump as possible, typically downstream of the pump. In the prior art systems the flowmeter needs to be able to measure the flowrate of a mixture of water and solid particles. Although such flowmeters exist, accuracy is impacted by the presence of solids and furthermore they need to be wear resistant as well. Alternatively the flowmeter can be positioned downstream of the pressure exchange chamber where it measures a relatively clean water flow. A drawback of this approach is the long distance between the pump and the flowmeter and the possible presence of flow dampening devices in-between. This makes the downstream flow measurement indirect, limiting the bandwidth of the flow measurement, limiting speed of the flow control loop. When positioning the feed pump downstream of the pressure exchange chamber, the flowmeter can measure in a relatively clean environment directly up or downstream of the feed pump. The feed pump flow is only dependent on the pressure load on the pump and not of the mixture being transported and the pump only experiences a relatively clean fluid with relatively constant density without large solid particles. In control terminology this means less disturbances which allows a more accurate control response.

According to a second aspect there is provided a method of filling a pressure exchange chamber fluid container located at a low altitude and having a medium inlet coupled to one end of the fluid container and a driving fluid outlet coupled to the other end of the fluid container, the method comprising: (i) opening a medium entry valve at the medium inlet to fill the fluid container; (ii) using a filling pump located at an opposite end of the pressure exchange chamber to the medium inlet to create a lower pressure at the driving fluid outlet of the fluid container than at the medium inlet of the fluid container to draw in medium through the medium inlet without the medium in the fluid container coming into contact with the filling pump; and (iii) closing a valve to stop the intake of medium to the fluid container.

The method may include the step of opening a driving fluid outlet valve (at an opposite side of the pressure exchange chamber to the medium entry valve) after (or simultaneously with) opening the medium entry valve at the medium inlet.

The step of closing a valve to stop the intake of medium to the pressure exchange chamber may comprise closing one or both of a driving fluid outlet valve or the medium entry valve at the medium inlet. The driving fluid outlet valve may be closed first, or both valves may be closed simultaneously. Closing the driving fluid outlet valve first allows the medium entry valve to close with lower risk of medium being located on the valve seat.

As used herein, "ambient pressure" refers to the pressure surrounding the pressure exchange chamber at the medium inlet.

According to a third aspect there is provided a hydraulic ore hoisting system including the pumping system of the first aspect.

It will now be appreciated that a hydraulic ore hoisting system can be provided that minimises breakage of nodules by ensuring that a filling pump does not come into contact with the nodules being transported to a surface level. If the pumping system was at ground level then the filling pump may experience excessive cavitation, but by location the filling pump at the same (or similar) elevation to the pressure exchange chamber on a sea bed, the static head of the water above the pressure exchange chamber ensures that cavitation effects are reduced.

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:.

Reference is first made to <FIG> and <FIG>, which are simplified schematic diagrams of a hydraulic ore hoisting system (HOHS) <NUM> according to a first embodiment of the present invention, including the pressure exchange chamber (PEC) <NUM>. The HOHS <NUM> is used for underwater (in this embodiment seabed) mining activities. In <FIG> and <FIG>, similar parts use the same reference numerals as <FIG> to illustrate that the primary difference is in the location of the centrifugal pump <NUM>, which is at the downstream end of the PEC <NUM>.

In typical embodiments, all of the PEC <NUM> is located at a lower altitude than a final delivery point at which a medium is to be delivered by the HOHS <NUM>. In this embodiment, the medium comprises ore particles (also referred to as nodules) ranging in size from <NUM> to <NUM> located in a carrier fluid (a liquid carrier) to produce a slurry of entrained and suspended ore particles.

In this embodiment, the HOHS <NUM> is a subsea system, the PEC <NUM> is located at or near the sea bed, the ore comprises polymetallic nodules, and the liquid carrier comprises sea water. Other embodiments may be land based (as described below with reference to <FIG>) or on a bed of a freshwater lake or an estuary.

The PEC <NUM> comprises a single fluid container (pipe) <NUM>, which has a valve arrangement <NUM>, <NUM> at each end thereof, referred to as a driving fluid valve arrangement <NUM> and a pumped medium valve arrangement <NUM>.

A pressurised discharge <NUM> is provided at a delivery end <NUM> of the PEC <NUM>. In this embodiment, the pressurised discharge <NUM> is an inlet to a pumped medium riser <NUM> that extends in a generally vertical direction from the delivery end <NUM> to a collection receptacle <NUM> at a surface <NUM>. A medium outlet line <NUM> couples the pumped medium valve arrangement <NUM> and the pressurised discharge <NUM>.

The pumped medium riser <NUM> may be coupled to (and extend downwards from) a vessel floating on the surface <NUM>. The vessel may comprise a ship, a barge, or the like.

A filling mechanism <NUM> is provided, in the form of a centrifugal pump, which is operable to fill the pipe <NUM> with a medium <NUM> to be pumped to the surface <NUM>. The centrifugal pump <NUM> fills the pipe <NUM> with medium <NUM> via a medium inlet line <NUM>. The medium inlet line <NUM> couples to the pipe <NUM> at a medium inlet <NUM>. Significantly, the centrifugal pump <NUM> is located at an opposite side of the PEC <NUM> to a harvester <NUM> (in other words, the centrifugal pump <NUM> is downstream of the PEC <NUM>). The harvester <NUM> collects ore particles (or nodules) from the sea bed, and water from a second fluid source (in this embodiment local seawater around the nodules). The mixture of the nodules and the sea water comprises the medium <NUM>.

The HOHS <NUM> also includes a positive displacement pump <NUM>, located at the surface <NUM> in this embodiment, which is operable to pump a driving fluid <NUM> through the PEC <NUM> and in direct contact with the medium <NUM> so that the medium <NUM> is displaced from the PEC <NUM> to the pressurised discharge <NUM> and from there to the surface <NUM> via the pumped medium riser <NUM>. However, in other embodiments a different type of pump, or pump arrangement, may be used, or lifting technology that does not use any pumps.

The positive displacement pump <NUM> is coupled to the driving fluid valve arrangement <NUM> via a driving fluid riser <NUM> and a driving fluid inlet line <NUM>.

A driving fluid outlet line <NUM> connects the PEC <NUM> (and particularly the pipe <NUM>) to a driving fluid discharge point <NUM>.

The combination of the pipe <NUM>, the driving fluid valve arrangement <NUM>, the pumped medium valve arrangement <NUM>, the driving fluid inlet and outlet lines <NUM>,<NUM>, and the medium inlet and outlet lines <NUM>, <NUM> is referred to herein as an open PEC <NUM>. "Open" refers to the direct contact between the driving fluid <NUM> and the medium <NUM>. "Pressure exchange" refers to the exchange of pressure between the two different fluids being pumped (driving fluid <NUM> and medium <NUM>). However, in other embodiments a spacer may be provided between the driving fluid <NUM> and the medium <NUM> so that it is an indirect pressure exchange system.

The driving fluid valve arrangement <NUM> is located at a positive displacement pump end <NUM> and comprises a driving fluid entry valve <NUM>, a driving fluid exit valve <NUM>, a compression valve <NUM>, a decompression valve <NUM>, a choke valve <NUM> (which may be in the form of a restriction in the pipe, i.e. a reduced diameter pipe portion), and a master valve actuator <NUM>. The master valve actuator <NUM> is provided to actuate the various valves <NUM> to <NUM> at the correct time for efficient operation of the HOHS <NUM>, as described in <CIT>.

Although not shown in the drawings, the driving fluid entry valve <NUM> is opened and closed by a hydraulic actuator. Similarly, a hydraulic actuator is paired with each of the driving fluid exit valve <NUM>, the compression valve <NUM>, and the decompression valve <NUM>. Each of these hydraulic actuators is controlled by the master valve actuator <NUM>.

In this embodiment, the master valve actuator <NUM> comprises a hydraulic power unit, and controls the individual hydraulic actuator in each valve <NUM>,<NUM>,<NUM>,<NUM>, in response to the master valve actuator <NUM> receiving a command from a system controller <NUM>.

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

To allow the entry <NUM> and exit <NUM> valves to open in a generally pressure balanced environment, a pressure balancing line <NUM> having a restriction (orifice) functioning as the choke valve <NUM>, is provided. This pressure balancing line <NUM> provides a bypass arrangement by coupling the compression valve <NUM> to the pipe <NUM> (bypassing the driving fluid entry valve <NUM>), and coupling the decompression valve <NUM> to the pipe <NUM> (bypassing the driving fluid exit valve <NUM>).

The compression valve <NUM> is provided to bypass the driving fluid entry valve <NUM> so that the pressure in the pipe <NUM> can be raised prior to opening of the driving fluid entry valve <NUM>; thereby reducing the force required to open the valve <NUM> and reducing the fluid flow rate through the driving fluid entry valve <NUM> upon opening. This has the advantage of prolonging the life of the driving fluid entry valve <NUM>.

Similarly, the decompression valve <NUM> is provided to bypass the driving fluid exit valve <NUM> so that the pressure in the pipe <NUM> can be lowered prior to opening of the driving fluid exit valve <NUM>; thereby preventing high flow rates of the driving fluid <NUM> through the driving fluid exit valve <NUM> upon opening thereof.

This limits and controls the flow rate during compression and decompression of the pipe <NUM>, thereby reducing wear in the compression <NUM> and decompression <NUM> valves.

The pumped medium valve arrangement <NUM> is located at delivery end <NUM> and comprises a pumped fluid exit valve <NUM> (also referred to as a discharge valve), a pumped fluid entry valve <NUM> (also referred to as a suction or filling valve), and a master valve actuator <NUM> to actuate the valves <NUM>, <NUM> at the appropriate time. The pumped fluid entry <NUM> and exit <NUM> valves open in a pressure balanced situation when the PEC <NUM> is properly decompressed or compressed respectively.

In some embodiments the master valve actuators <NUM> and <NUM> can be combined in a single master valve actuator which controls all valve actuators of all actuated valves <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>.

In some embodiments, two choke valves (or restrictions) <NUM> may be provided, one in series with the compression valve <NUM> and one in series with the decompression valve <NUM>. Other arrangements are also possible.

The HOHS <NUM> also includes a system controller <NUM> for controlling the operation of the entire system, including the pumps <NUM>,<NUM>, the valves <NUM> to <NUM> and <NUM> to <NUM>, and the master valve actuators <NUM>,<NUM>.

The PD pump <NUM> needs to be provided with fluid. In this embodiment, a first (surface) fluid source <NUM> is provided at the surface <NUM> to provide water for the driving fluid <NUM>. This provides water from the surface <NUM>, which may be sea water in this embodiment. This provides the hydrostatic pressure benefit of using surface water. The fluid source <NUM> may include a filter for removing large particulates from the fluid prior to providing it to the positive displacement pump <NUM>.

Reference is now also made to <FIG>, which is a simplified schematic diagram of the harvester <NUM>. The harvester <NUM> comprises a chassis <NUM> in which is mounted a movement system <NUM> (in the form of hydraulic thrusters) operable to move the harvester <NUM> along a sea bed <NUM>. The chassis <NUM> defines an aperture <NUM> at a lower part thereof and aligned with a collection head <NUM> directed at the sea bed <NUM> through the aperture <NUM>. The collection head <NUM> lifts nodules (illustrated (not to scale) by numeral <NUM>) from the sea bed <NUM> and deposits them in a nodule hopper <NUM>, which effectively performs the slurry preparation function <NUM> of <FIG>. A flexible suction hose <NUM> couples the nodule hopper <NUM> to the medium inlet line <NUM>.

The nodule harvester <NUM> also includes a guidance system <NUM> that provides navigational information to the hydraulic thrusters <NUM> to guide it to deposits of nodules. The guidance system <NUM> may be connected to a transceiver on a surface ship by a wired or wireless connection (illustrated by numeral <NUM> in <FIG>).

When the pumped fluid entry (suction) valve <NUM> is open and the filling pump <NUM> is operating, the filling pump <NUM> reduces the pressure in the pipe <NUM>, causing the pressure to drop in the medium inlet line <NUM> and the flexible suction hose <NUM>, thereby creating hydraulic suction. This, in turn, causes the mixture of nodules <NUM> and sea water from the nodule hopper <NUM> (that is, medium <NUM>) to be sucked through the flexible suction hose <NUM>, the medium inlet line <NUM> and into the pipe <NUM>. This fills up the pipe <NUM> without the medium <NUM> coming into contact with the filling pump <NUM>. This reduces any damage to the polymetallic nodules <NUM> entrained in the sea water. It also has the benefit of avoiding the requirement for a pump on the harvester <NUM> to feed the pipe <NUM> with medium <NUM>.

The operation of the HOHS <NUM> is generally the same as that of prior art HOHS <NUM>, which is described in detail in described in PCT/IB2019/<NUM>.

Initially, there is a decompression step for the pipe <NUM> to the pressure in the driving fluid outlet line <NUM>, thereby allowing the driving fluid exit valve <NUM> and the pumped fluid entry valve <NUM> to be opened. Once decompressed, the chamber <NUM> is filled with the medium <NUM>, which automatically flows into the pipe <NUM> due to the operation of the centrifugal (filling) pump <NUM> reducing the pressure in the pipe <NUM> (the driving fluid exit valve <NUM> being in the open position). The filling pump <NUM> draws (or sucks) out the driving fluid <NUM> from the pipe <NUM> through the driving fluid exit valve <NUM>, so that the medium <NUM> starts to fill the pipe <NUM> via the suction valve <NUM>. The medium <NUM> enters the pipe <NUM> at a relatively high flow rate so the pipe <NUM> fills relatively rapidly.

Once the pipe <NUM> is filled, the driving fluid exit valve <NUM> is closed, thereby stopping the outflow of relatively low pressure driving fluid <NUM> from the pipe <NUM> and stopping the inflow of medium <NUM> to the pipe <NUM>.

The nodules in the medium <NUM> are allowed to settle to a lower part of the PEC <NUM> and away from the valve seat of suction valve <NUM>, thereby allowing a better closure of the suction valve <NUM>.

The chamber <NUM> is then compressed to the pressure in the driving fluid inlet line <NUM> by allowing high pressure driving fluid <NUM>, delivered by the positive displacement pump <NUM>, to enter the pipe <NUM> via the compression valve <NUM> and the pressure balancing line <NUM>.

The driving fluid entry valve <NUM> and the pumped fluid exit valve <NUM> are then opened so that high pressure driving fluid <NUM> flows into the pipe <NUM> displacing the pressurised medium <NUM> through the pumped fluid exit valve <NUM>, the medium outlet line <NUM>, the pressurised discharge <NUM>, and partly up the pumped medium riser <NUM> (depending on the height of the riser <NUM>).

The driving fluid entry valve <NUM> is then closed, stopping the inflow of driving fluid <NUM> into the pipe <NUM>, and stopping the outflow of medium <NUM> from the pipe <NUM>.

Although only a single pipe <NUM> is illustrated in the HOHS <NUM> of <FIG>, in other embodiments a plurality of pressure exchange chambers may be used. For example, in <FIG>, three PECs 201a, 201b, and 201c are provided in a pressure exchange system <NUM>, and a system controller <NUM> manages the sequential filling and discharge of the three PECs 201a,b,c to provide a continuous flow of medium <NUM> to the surface <NUM>.

Each of the three PECs 201a,b,c includes identical valves to those described with reference to the PEC <NUM> of <FIG> (choke valve <NUM> is not illustrated in <FIG> for clarity, but it is included in each PEC <NUM>). Each of the three pressure exchange chambers 201a,b,c, is identical (or at least very similar for all practical purposes) to the PEC <NUM>.

By having multiple PECs <NUM> arranged in parallel, at least one PEC pipe 212a,b,c is always filled with medium <NUM> and ready for discharge, thereby allowing a continuous feed of driving fluid <NUM> to the PECs <NUM> and a continuous feed of medium <NUM> to the PECs <NUM>.

Reference is now made to <FIG>, which is a simplified schematic diagram of another embodiment of an HOHS <NUM>, where the PEC <NUM> (or pressure exchange system <NUM> could be used instead of PEC <NUM> if three pipes are desired) is land based and the pipe <NUM> (or pipes 212a,b,c) is located beneath an area from which medium is to be pumped. In other words, the medium preparation area is higher than the PEC <NUM>.

The PEC <NUM> of <FIG> is identical to that of <FIG>, and is located at a low altitude (a sub terranean level) in a mine. However, the medium is prepared by an ore mixer <NUM> (combining ore with water) on a raised shelf <NUM> that is at a higher altitude (for example at least <NUM> higher) than the pipe <NUM> so that there is an elevated pressure at the medium inlet <NUM> compared with the static pressure at the ore mixer <NUM>. This ensures that there is sufficient pressure difference to prevent cavitation and thereby allow the filling pump to be installed at the opposite end of the pressure exchange chamber. In other embodiments, the ore mixer <NUM> may be at least <NUM> (in some embodiments, at least <NUM>, in other embodiments at least <NUM>) above the medium inlet <NUM>. The height selected may depend on the desired reduction in cavitation.

Although the above embodiments have only described a direct pressure exchange chamber, the above teachings could equally be applied to an indirect pressure exchange chamber (that is, one having a separator between the driving fluid and the medium being pumped to the surface).

Similarly, although the above embodiments have only described generally horizontal pressure exchange chambers, the above teachings could equally be applied to vertical, an angled pressure exchange chambers.

Similarly, although the above embodiments have only described a positive displacement pump being used to raise the medium to the surface, other pumps could be used (such as centrifugal pumps).

In other embodiments, the filling pump may be any kind of pump (not just a centrifugal pump) because it only needs to handle a relatively clean driving fluid when it is positioned downstream of the pressure exchange chamber.

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.

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.

Claim 1:
A pumping system (<NUM>, <NUM>) for pumping a medium (<NUM>) comprising ore suspended in carrier fluid from an underground or underwater location to a surface (<NUM>) at a raised level, the system comprising:
(i) at least one pressure exchange chamber (<NUM>, <NUM>) comprising a fluid container (<NUM>, <NUM>) having a valve arrangement (<NUM>, <NUM>) at each end and being located at a lower altitude than the raised level;
(ii) a medium inlet (<NUM>) at one end of the chamber (<NUM>, <NUM>) operable to receive a low pressure medium (<NUM>) for transport into the chamber (<NUM>, <NUM>); characterised by
(iii) a filling pump (<NUM>) located at an opposite side of the chamber (<NUM>, <NUM>) to the medium inlet (<NUM>), and being operable to draw medium (<NUM>) from the medium inlet (<NUM>) at low pressure, through the chamber (<NUM>, <NUM>), and towards the filling pump (<NUM>) to fill the chamber (<NUM>, <NUM>) without the medium (<NUM>) in the chamber (<NUM>, <NUM>) having come into contact with the filling pump (<NUM>).