GB2391912A

GB2391912A - Energy recycling pump

Info

Publication number: GB2391912A
Application number: GB0218995A
Authority: GB
Inventors: Colin Alfred Pearson
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-08-15
Filing date: 2002-08-15
Publication date: 2004-02-18
Also published as: AU2003259330A1; WO2004016947A1; GB0218995D0

Abstract

A pump powered partly by a mechanical drive and partly by a pressurised fluid flow, in reverse osmosis and similar systems. The pump consists of one or more piston-in-cylinder assemblies. One face of each piston 23 provides a pumping action while a pressurised driving fluid flow is applied to the opposite piston face, thus supplementing the drive force applied to each piston via a piston rod. Input and output of the pumped flow is controlled by pump valves 25 and 26, of a non-return type, operated by the pumped flow. Input and output of the driving fluid is controlled by drive valves 7 and 8, which are themselves controlled by operational connection to the pump valves. The pump may use poppet valves and may have means to limit the pressure differential across the pump, such as pressure relief valves, an elastic connection 14 between the piston and piston rod, elasticity of the piston, allowing axial movement between the piston and piston rod or between the piston and piston seal 24.

Description

Enerav RecVclinu Pump The invention herein described is a pump powered

partly by a mechanical drive and partly by a pressurised fluid flow. The pump is particularly applicable to reverse osmosis systems, which commonly waste a large part of their input energy by failing to recover the energy in a pressurised fluid flow. Energy savings up to 90% are possible.

The pump consists of one or more piston-in-cylinder assemblies. In operation, each piston reciprocates within its cylinder. One face of each piston provides a pumping action while a pressurised driving fluid flow is applied to the opposite piston face, thus supplementing the drive force applied to each piston via a piston rod. Input and output of the pumped flow is controlled by pump valves of a non-return type operated by the pumped flow. Input and output of the driving fluid is controlled by drive valves which are themselves controlled by operational connection to the pump valves.

A feature of the pump is that it may conveniently use poppet valves for both pump and drive valves. A poppet valve in this context is one in which the moving element is referred to as a poppet and has an axis of operational movement which is perpendicular to the plane of the sealing surface. Poppet valves have advantages over other valve types in that there is little wear on their sealing surfaces and no requirement for expensive close-tolerance manufacture.

The pump differs from prior art in having the drive valves in operational connection to the pump

valves, thus allowing simpler construction. Prior art embodies operational connection of the drive

valves to the mechanical drive, (Eg US4187173, US4288326, US4432876 and US4434056), or to the cylinder pressures, (Eg USRE33135, US4124488 and US4929347) Figures 1 to 4 show a single cylinder of an embodiment of the pump.

Figure 5 gives an indication of piston travel and pressures during one cycle of pump operation, and shows those applying to figures 1 to 4.

Figures 6 to 10 show components of alternative embodiments of the pump.

Figure 11 shows a cam means for driving the pump.

Figure 12 shows a reverse osmosis or similar system incorporating the pump.

Figure 1 shows the pump prior to starting. The piston rod and piston are stationary, there is no flow and all the valves are shut. Pressures are assumed to be as shown in figure 5. The piston 23 is free to reciprocate in a cylinder formed in the pump body 21. A piston seal 24 restricts leakage between the piston and the cylinder walls. The piston subdivides the cylinder into a pumping chamber 22 and a driving chamber 13. The piston rod 10 is driven to reciprocate by any convenient means, and applies a force to the piston via piston spring 14. A rod seal 9 restricts leakage between the piston rod and the pump body. The swept volume of the driving chamber is less than that of the pumping chamber by a fraction equal to the piston rod area divided by the piston area. Because of this difference in swept volumes, the driving fluid flow rate is less than the pumped fluid flow rate by the same fraction.

Pumped flow can enter the pumping chamber via pump inlet port 18 and pump inlet valve 25, and can leave via pump outlet valve 26 and pump outlet port 3. Driving flow can enter the driving chamber via drive inlet port 8 and drive inlet valve 7, and can leave via drive outlet valve 12 and drive outlet port 11.

The pump inlet valve is biased towards its closed position by valve spring 17, and mechanically connected to the drive outlet valve via a linkage means 16, which is sealed against leakage where it passes through the pump body 21 by seal means 15. Said linkage means allows limited relative motion between the pump inlet valve and the drive outlet valve, thus compensating for manufacturing inaccuracies and allowing both pump inlet valve and drive outlet valve to close fully. In a similar manner the pump outlet valve is biased by valve spring 5 and connected to the

drive inlet valvevia linkage 4, which is sealed against leakage where it passes through the pump body 21 by seal means 6.

The pump valves have poppets 1 and 20 which are surrounded by closefitting bores, 2 and 19 respectively, for the first part of their travel from a closed position. Said close-fitting bores restrict flow through the pump valves, thus increasing the pressure differentials and thereby the flow forces acting on them.

Typically, in operation as part of a reverse osmosis system desalinating seawater, the pump inlet pressure could be around 2 bar, the drive outlet pressure around 1 bar, the pump outlet pressure around 70 bar and the drive inlet pressure around 65 bar. For 20% recovery of desalinated water, the driving flow rate would be around 80% of the pumped flow rate, requiring the piston rod area to be around 20% of the piston area.

Figure 2 shows the pump on a pumping stroke. Piston rod 10 and piston 23 are moving upwards, compressing the fluid in the pump and drive chambers. Pump chamber and drive chamber pressures have risen to levels at which the pressure force tending to open the pump outlet valve 2 has overcome the closing force of valve spring 5 and the pressure force tending to close drive inlet valve 7, thus causing pump outlet and drive inlet valves to open. This point is marked as 40 on figure 5. Pumped flow is then free to pass out of the pump outlet port, and driving flow is free to enter the drive inlet port. The pump outlet and drive inlet valves are held open by ensuring that the flow force tending to open the pump outlet valve overcomes both the closing force of valve spring 5 and the flow force tending to close the drive inlet valve. During the pumping stroke, the pump inlet valve and drive outlet valve are held closed by the pressure differentials across them.

The pressure differential between the pump chamber and the drive chamber is determined by the characteristics of piston spring 14. Line 41 on figure 5 shows how the drive chamber pressure would drop rather than rise if the piston were rigidly connected to the piston rod, thus increasing the pressure differential across the drive inlet valve and preventing it from being opened. The characteristics of the piston spring 14 are also chosen to avoid excessive relative travel between the piston rod and the piston, which would reduce the stroke of the piston and thereby the delivery of the pump.

The flow force characteristic of the pump outlet valve is modified by the close-fitting bore 2 around the pump outlet valve poppet 1. Said bore restricts flow through the pump outlet valve during the first part of its opening travel, thereby causing the pressure differential and consequent flow force to be greater on the pump outlet valve than on the drive inlet valve, thus causing both valves to open. it may be advantageous to use a pump valves of larger diameter than the connected drive valves, to increase the net pressure force opening each pump and drive valve pair. Figure 3 shows the pump at the end of the pumping stroke. As piston rod 10 and piston 23 slow down towards the end of the stroke, the flow rate through the pump outlet valve, and the consequent flow force on it, reduce to zero. This allows valve spring 5 to close pump outlet valve 2, and allows flow force to close drive inlet valve 7 which is no longer being held open by the pump outlet valve via linkage 4.

Figure 4 shows the pump on a suction stroke. Piston rod 10 and piston 23 are moving downwards. Pump inlet valve 20 and drive inlet valve 12 have opened and remain open under the influence of pressure and flow, in a manner similar to that described above for the pumping stroke shown in figure 2.

Figures 6 to 9 show alternative features, which could be used singly or in combination.

Figure 6 shows a piston 50 rigidly attached to a piston rod 51 and including a flexible portion 52.

Said flexible portion serves the same function as the piston spring 14 shown in figure 1.

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Figure 7 shows a piston 55 which is mounted to piston rod 57 in a way which enables limited relative axial movement between piston rod and piston. Said axial movement serves a similar function to piston spring 14 shown in figure 1, and is equivalent to a variable-rate spring having zero rate over the range of free movement and a very high rate at the extremes of movement.

Seal means 56 restricts leakage between the piston rod and piston. It may alternatively be convenient to restrict said leakage by use of a small clearance between the piston bore and piston rod, coupled with sealing faces on either side of the piston.

Figure 8 shows a piston configuration which is functionally equivalent to that shown in figure 6.

The piston 58 is rigidly attached to the piston rod 60, but there is limited relative free axial movement between the piston seal 59 and the piston.

Figure 9 shows a piston 61 rigidly attached to a piston rod and incorporating pressure relief valves 62 and 63. These serve a similar function to the piston spring 14 shown in figure 1, in that they limit the pressure differential across the piston. Said pressure relief valves could alternatively be incorporated in the pump body.

Figure 10 shows an alternative valve arrangement in a pump otherwise as illustrated in figures 1 to 4. The pump inlet and outlet valves 85 & 80 incorporate elastically deformable elements 84 & 81. Said elements firstly allow limited relative movement between the sealing surfaces of a pump valve and its connected drive valve, and secondly restrict pump valve flow. Both these characteristics are beneficial for pump operation, for reasons described above. Compression of a deformable element, 84, permits full closure of a pump valve and its connected drive valve.

Expansion of a deformable element, 81, restricts flow through a pump valve, causing a pump valve opening travel 82 to be less than the opening travel 83 of its connected drive valve.

Figure 11 shows side and end views of a means for driving the piston rods. A pump body 87 is substantially as described above. A shaft 84 carries cams 82 & 83 and is driven to rotate by any convenient means. Said cams drive piston rods 85 & 81 on their upward strokes. Return springs 86 & 80 drive the piston rods on their downward strokes. The use of cams rather than cranks, to drive the piston rods, has the advantage that cam profiles can be chosen to give a substantially constant output flow from a pump having two or more cylinders. Pressure and drive load fluctuations are thereby reduced.

Figure 12 shows a reverse osmosis system incorporating a pump as previously described. An inlet solution flow at low pressure enters the pump 94 through pump inlet port 93 and leaves the pump through pump outlet port 95 at high pressure. The inlet solution then enters a membrane assembly 96. A proportion the solvent, but little of the solute, passes through a semi-permeable membrane 97 and leaves the membrane assembly at low pressure through outlet 90. The remaining flow of concentrated solution leaves the membrane assembly at high pressure, enters the pump through the drive inlet port 91, and leaves the pump through drive outlet port 92 at low pressure. The ratio of piston rod area divided by piston area needs to match the ratio of solvent flow through the membrane divided by solution flow into the membrane assembly. The pump could also be applied to ultrafiltration, using a system as described above for reverse osmosis, but having a filter medium in place of the semi-permeable membrane.

Figure 13 shows an alternative valve means in part section, consisting of a plug, 98, sliding into a resilient sealing sleeve, 99, to effect closure, and sliding out of said sleeve to open. This has the advantage of eliminating the need to allow limited relative motion in the linkage between each pair of connected pump and drive valves.

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Claims

Claims

1 A reciprocating-piston pump having one or more pistons and impelling a pumped fluid flow, said pump being powered partly by mechanical drive to each piston and partly by a driving fluid now, said pumped fluid flow being impelled by a first face of each pump piston and said driving fluid flow being applied to a second face of each pump piston, said pump having pump valve means controlling said pumped fluid flow and drive valve means controlling said driving fluid flow, said pump valve means being nonreturn valves operated by the pressure differential across them of said pumped fluid flow, and said drive valve means having operational connection to said pump valve means.

2) A pump as claimed in claim 1, in which said operational connection between a said pump valve means and a said drive valve means consists of a mechanical connection.

3) A pump as claimed in claim 2, in which a said mechanical connection permits limited travel of a moving element of a said pump valve means relative to a moving element of a said drive valve means. 4) A pump as claimed in claim 2, in which a said pump valve means or a said drive valve means or said mechanical connection incorporate elastically deformable elements.

5) A pump as claimed in any previous claim, in which a said pump inlet valve is operationally connected to a said drive inlet valve and a said pump outlet valve is connected to a said drive outlet valve.

6) A pump as claimed in any previous claim, in which said pump valve means or said drive valve means incorporate valve elements having axes of operational movement substantially perpendicular to the planes of their sealing surfaces.

7) A pump as claimed in any previous claim, in which a said pump valve means incorporates means to restrict flow during the first part of its travel from a closed position.

8) A pump as claimed in any previous claim, having pressure limiting means to limit the pressure differential across a pump piston during all or part of a pump piston stroke.

9) A pump as claimed in claim 8 in which said pressure-limiting means consists of pressure relief valve means.

10) A pump as claimed in claim 9 in which said pressure relief valve means is incorporated in a said piston.

11) A pump as claimed in claim 8 in which said pressure-limiting means incorporates an elastic connection between said piston and said piston rod.

12) A pump as claimed in claim 8 in which said pressure-limiting means incorporates elasticity incorporated into said piston.

13) A pump as claimed in claim 8 in which said pressure-limiting means incorporates limited axial movement between a said piston and a said piston rod.

14) A pump as claimed in claim 8 in which said pressure limiting means incorporates limited axial movement between a said piston and the means sealing said piston to the bore of the cylinder in which said piston reciprocates.

15) A pump as claimed in any previous claim, in which said mechanical drive to the piston rod incorporates cam and follower means.

16) A pump as claimed in claim 15 and having two or more cylinders, in which said cam means is configured to give a constant pumped output flow rate.

17) A pump as claimed in any previous claim and incorporated into a reverse osmosis or ultrafiltration or similar system, said pump providing fluid flow to a high-pressure side of a membrane or filter medium and being partly powered by the fluid flow retuning from said high pressure side.

Amendments to the claims have been filed as follows Claims 1 A reciprocating-piston pump having one or more pistons and impelling a pumped fluid flow, said pump being powered partly by mechanical drive to each piston and partly by a driving fluid flow, said pumped fluid now being impelled by a first face of each pump piston and said driving fluid flow being applied to a second face of each pump piston, said pump having pump valve means controlling said pumped fluid flow and drive valve means controlling said driving fluid flow, said pump valve means being nonreturn valves operated by the pressure differential across them of said pumped fluid flow, and said drive valve means having operational connection to said pump valve means.

2) A pump as claimed in claim 1, in which said operational connection between a said pump valve means and a said drive valve means consists of a mechanical connection.

3) A pump as claimed in claim 2, in which a said mechanical connection permits limbed travel of a moving element of a said pump valve means relative to a moving element of a said drive valve means. 4) A pump as claimed in claim 2, in which said pump valve means or said drive valve means or said mechanical connection incorporate elastically deformable elements.

..........CLME: 5) A pump as claimed in any previous claim, in which the pump valve means comprises a pump inlet valve and a pump outlet valve, and the drive valve means comprises a drive inlet valve and a drive outlet valve, a said pump inlet valve being operationally connected to a said drive inlet valve and a said pump outlet valve being connected to a said drive outlet valve.

6) A pump as claimed in any previous claim, in which said pump valve means or said drive valve means incorporate valve elements having axes of operational movement substantially perpendicular to the planes of their sealing surfaces.

7) A pump as claimed in any previous claim, in which a said pump valve means incorporates means to restrict flow during the first part of its travel from a closed position.

8) A pump as claimed in any previous claim, having pressure limiting means to limit the pressure differential across a pump piston during all or part of a pump piston stroke.

9) A pump as claimed in claim 8 in which said pressure-limfflng means consists of pressure relief valve means.

10) A pump as claimed in claim 9 in which said pressure relief valve means is incorporated in a said piston.

11) A pump as claimed in claim 8 in which said pressure-limiting means incorporates an elastic connection between said piston and said piston rod.

12) A pump as claimed in claim 8 in which said pressure-limiting means incorporates elasticity incorporated into said piston.

13) A pump as claimed in claim 8 in which said pressure-limfflng means incorporates limited axial movement between a said piston and a said piston rod.

14) A pump as claimed in claim 8 in which said pressure limiting means incorporates limped axial movement between a said piston and the means sealing said piston to the bore of the cylinder in which said piston reciprocates.

15) A pump as claimed in any previous claim, in which said mechanical drive to the piston rod incorporates cam and follower means.

16) A pump as claimed in claim 15 and having two or more cylinders, in which said cam means is configured to give a constant pumped output flow rate.

17) A reciprocating-piston pump substantially as herein described with reference to the accompanying drawings.

18) A reverse osmosis or ultrafiltration or similar system comprising a pump as claimed in any previous claim arranged to provide fluid flow to a high-pressure side of a membrane or filter medium and to be partly powered by the fluid flow returning from said nigh pressure side.