GB2102304A - Fluid pressure device for purifying brine - Google Patents

Abstract

A plunger (31) is reciprocably driven, its movement to the right taking in brine from an inlet (48). On movement to the left, brine is forced through a bore (49) and a conduit 11 past a separation membrane (12). Clean water passes the membrane to an outlet (14). Concentrated brine under pressure enters a chamber (22) via passage (15) and acts on a second plunger (33), mechanically connected with the first plunger (31), to assist the first plunger in its movement to the left. On reverse movement, a valve 41 is operated to open an outlet (47) from which the concentrated brine is exhausted. A reciprocation drive is attached to a collar (40) for actuating the plungers and the valve. <IMAGE>

Description

SPECIFICATION Fluid pressure device This invention relates to a fluid pressure device for forcing fluid through a separation member, e.g.

for forcing liquid through a semi-permeable membrane.

It is known to separate ions from solution, for example, to produce purified water from brine, by moving the solution past a semi-permeable membrane under pressure, so that some water passes through the membrane and concentrated solution, so formed on the opposite side of the membrane, is removed. Solution under pressure is continuously fed past the membrane through a relief valve. As a result, there is a substantial loss of energy, although, on a large scale, it is possible to drive a turbine with the waste pressurised solution.

The present invention permits purification of brine with reduced loss of energy and facilitates production of drinkable water from brine by manual application of energy.

In accordance with this invention, there is provided a fluid pressure device comprising a separation membrane, reciprocable pressure means movable in one direction to force fluid past one side of the separation membrane to exhaust, and a fluid outlet on the other side of the membrane, wherein, between the separation membrane and exhaust, there is provided movable means arranged to be acted on by the pressure of fluid fed from the separation membrane to assist said pressure means, and valve means actuable to direct fluid from the movable means to the exhaust when the pressure means moves in the reverse direction.

The invention also resides in a fluid pressure device for forcing fluid through a separation membrane, the device comprising a fluid circuit incorporating the separation membrane, a fluid inlet to the circuit, a first cylinder including a first plunger surface for forcing fluid received from the inlet past one side of the separation membrane, a fluid outlet on the opposite side of the separation membrane and separated from the circuit by the separation membrane, a second cylinder including a second plunger surface of smaller effective area than the first plunger surface and movable with the latter, means for directing fluid passing said one side of the separation membrane to the second cylinder to act on the second plunger surface, valve means actuable during reverse movement of the second plunger surface to direct fluide from the second cylinder to an exhaust outlet, and drive means for effecting relative reciprocation of the plunger surfaces in the cylinders.

Hence, the energy used to pressurise the fluid to permit fluid to cross the separation membrane, is not lost to exhaust, but is used to move the second plunger surface and hence assist movement of the first plunger surface.

Reference is now made to the accompanying drawings, wherein:~ Figure 1 is a sectional view of a fluid pressurising section of a device according to the invention; Figure 2 is a diagrammatic view of a manually actuable operating section of the device; Figure 3 is a diagrammatic view of an alternative construction of an operating section of a multiple cylinder assembly device; Figure 4 is a sectional view of a cylinder assembly of the alternative construction of Figure 3; and Figure 5 is a sectional view of a modified cylinder assembly.

Referring to Figure 1 , there is shown a conduit 11 housing at one end a semi-permeable membrane 12. In this example, the membrane is in the form of a multiplicity of hollow fibres having potted ends. The interiors of the fibres lead to a manifold 13 and a purified water outlet, hereafter called the "second outlet" 14. A radial passage 15 communicates with the exterior of the membrane fibres and with the main portion of the conduit 11.

The conduit 11 is supported at each end by a respective cylinder block 20,21. One of the blocks,21, has a chamber 22 and incorporates the passage 15, which communicates with the chamber 22. The other block, 20, has a chamber 24 and a passage 25 between the conduit 11 and the chamber 24. The passage 25 accommodates a non-return ball valve 26, which permits flow only in the direction from the chamber 24 to the conduit 11.

A plunger assembly 30 lies axially parallel to the conduit 11 and has a first plunger section 31 slidably engaged in the chamber 24 and a second plunger section 32 slidably engaged in the other chamber 22. The second plunger section 32 is a hollow conduit and has an effective surface 33 within the chamber 22 with an area less than the area of the effective surface 34 of the other plunger 31 in the chamber 24.

The join between the two plunger sections 31,32 is surrounded by a collar 40, which is fixed to the second plunger section 32, but is slidable on the first plunger section 31. The first section 31 has a head 41 within the second section 32, provided with grooves in the periphery to permit passage of liquid past the head. The head has a shoulder 43, which is engageable by a projection 44 of the collar to limit sliding movement in one direction. The head also defines a valve seat 45 supporting a resilient ring 46. The projection 44 defines a valve member which abuts the ring 46 to limit movement of the collar in the reverse direction. The collar 40 includes a first outlet 47, which communicates with the interior of the second plunger section 32, through the grooves in the head 41, when the projection 44 is off the seating ring 46.

The collar 40 also includes an inlet 48, which communicates with an axial passage 49 in the first plunger section 31. This passage 49 communicates with the chamber 24 through a non-return valve 50, which permits flow only in the direction from the inlet to the chamber 24.

In operation, sea water may be fed into the inlet 48. Initial movement of the collar 40 to the right from the position shown moves the projection 44 off the seating ring 46. With the circuit primed continued movement of the collar moves the plunger assembly 30 to the right, so that solution flows past the valve seating ring to the first outlet 47. The non-return valve 26 prevents reverse flow of solution. The first plunger section is simultaneously moved to the right and fresh sea water enters the chamber 24 from the inlet 48.

On movement of the collar 40 to the left, the projection 44 seats on the seating ring 46 and sea water in the chamber 24 is forced into the conduit 11. Water is forced across the membrane 12, so that purified water passes out of the second outlet 14, causing an increase in salt concentration on the other side of the membrane. This concentrated solution is flushed away from the membrane into the chamber 22, as the second plunger section 32 moves to the left. On repetition of this cycle, the concentrated solution is removed from the chamber 22 through the second outlet 47.

Figure 2 shows one arrangement for manual actuation of the device. The collar 40 carries bosses 60, 61 on which are pivotally mounted arms 62, 63. These arms are connected to tension springs 65 through flexible lines 66, 67 and a bar 68. The opposite ends of the springs are secured to a bar 69 fixed relative to the blocks 20, 21. The lines 66, 67 pass over eccentrically pivoted wheels 70, 71. A pulley system connects a handle 72 to the arms 62, 63 and comprises pulley wheels 80 to 86.

The arrangement is such that a pull on the handle moves the collar 40 to the right, as shown in Figure 1, and tensions the springs 65. The collar is moved to the left by the springs 65. The eccentrics 70, 71 serve to control this movement to make the pressure applied to the membrane substantially constant.

A further embodiment of the invention is shown in Figures 3 and 4. Figure 3 shows a multiplicity of cylinder assemblies 100 operated by a common driving means, shown here as a simple crank with multiple connecting rods 130, so disposed as to give a sensibly constant flow and pressure to the separating membrane 121. A pressure reservoir 131 may be included in the fluid circuit if required.

The incoming brine enters through a conduit 101 and is distributed by flexible or sliding connections 101 b to the cylinder assemblies 100; pressurised brine is conducted to the separation membrane 121 via similar flexible or sliding members 1 02b through a conduit 102 and the rejected, or concentrated solution, which is still at high pressure, is similarly returned to the cylinder assemblies 100 via a conduit 103 and connections 1 03b in order that the pressure energy may be recovered. The concentrated solution under low pressure is discharged through a conduit.

Each cylinder assembly 100 is movably constrained in a body structure by guides 123a and the extent of their movement is limited by stop members 1 23b, 1 23c. The body structure also carries bearings 132 supporting the crankshaft 124.

A cylinder assembly 100 is shown in more detail in Figure 4. Brine enters the assembly during leftward movement of a plunger 109 via a conduit 101 a and a non-return valve 105 to a cylinder 126 in which the plunger 109 can reciprocate.

Movement of the plunger 109 to the right forces liquid through a further non-return valve 106 to a conduit 102a and hence by the conduit 102 to the separating membrane 121. Purified water passes through the membrane to the product outlet 122 and the concentrated solution passes to the conduit 103. Solution from this conduit 103 passes through a conduit 103a and a poppet valve 107 to a cylinder 127, so as to urge a plunger 110 therein to the right.

Leftward motion of the plunger 110 forces the concentrated solution through a poppet valve 108 to a conduit 104a and hence to the waste conduit 104.

A piston rod 11 3 is secured to the plunger 110 and extends into a bore in the other plunger 109 in which it is slidable. Fluid in the cylinder 126 is isolated from that in cylinder 127 by a sealing member 115 through which the piston rod extends. Cylinder 126 is larger in swept volume than cylinder 127, typically by 10% to 30%, the difference in swept volumes being in the same proportion as the required ratio of flow to and through the separation membrane 121.

Alternatively the ratio may be slightly greater, such that the excess differential flow causes the plunger 109 to move away from the plunger 110, compressing a spring 111.

Valve rods 116,117 and valves 107, 108 are actuated by the stop members 1 23b, 1 23c during movement of the cylinder assembly within the body structure 123. Such movement is caused by the resistance of the plungers 109, 110 sliding in their respective cylinders either by friction or by virtue of hydraulic pressure in the cylinders. An alternative embodiment causes the valve rods 116,117 to be actuated either by cams or cranks attached to the crankshaft 124, or by mechanical connections to the plunger movements of other cylinder assemblies. The use of mechanically operated valves as opposed to hydraulically operated valves such as depicted in Figure 1 means that the separation member 121 can be maintained at conditions of constant pressure and flow.

The connection between plungers 109 and 110 may be of the spring-loaded type as shown, whereby the pressure across the membrane 121 tends to be sensibly constant, or alternatively a rigid connection between the plungers 109. 110 may be used, in which case the flow through the membrane 121 will tend to be a sensibly constant proportion of the inlet flow, the pressure across the membrane 121 varying to accommodate changing characteristics of the membrane.

A further embodiment of a cylinder assembly is shown in Figure 5. This embodiment is similar to that of Figure 4 and has cylinders 126, 127 and plungers 109, 110 including a sliding piston rod 113 and a spring 111. The various valves are replaced by valves 205 to 209, which are actuated by the stop members 223b and 223c.

Brine enters the cylinder 126 through a port 201 in the stop member 223b, the one-way valve 205 and a conduit 200, when the plunger 109 moves to the left. Reverse movement of the plunger 109 forces liquid through the conduit 200, the one-way valve 206 and a port 202 in the stop member 223b to the separating membrane.

Concentrated solution from the separating membrane re-enters the assembly through a port 203 in the other stop member 223c, and past valve 207 to a chamber 210 of a slide valve 209.

This valve is actuated by engagement with the two stop members 223b, 223c. From this chamber, the solution passes by conduit 211 to the cylinder 127, so as to urge the plunger 110 to the right.

Leftward movement of the plunger 110 forces the solution back through the conduit 211, the valve chamber 210, and valve 208 to a waste outlet port 204 in the stop members 223c.

Movement of the plunger 109 to the right forces brine through the separating membrane and, it will be seen that this movement is assisted by the concentrated solution acting on the plunger 110 in the cylinder 127 and the concentrated solution is urged to waste under low pressure.

Claims (14)

1. A fluid device comprising a separation membrane, reciprocable pressure means movable in one direction to force fluid past one side of the separation membrane to exhaust, and a fluid outlet on the other side of the membrane, wherein, between the separation membrane and exhaust, there is provided movable means arranged to be acted on by the pressure of fluid fed from the separation membrane to assist said pressure means, and valve means actuable to direct fluid from the movable means to the exhaust when the pressure means moves in the reverse direction.

2. A fluid device for forcing fluid through a separation membrane, the device comprising a fluid circuit incorporating the separation membrane, a fluid inlet to the circuit, a first cylinder including a first plunger surface for forcing fluid received from the inlet past one side of the separation membrane, a fluid outlet on the opposite side of the separation membrane and separated from the circuit by the separation membrane, a second cylinder including a second plunger surface of smaller effective area than the first plunger surface and movable with the latter, means for directing fluid passing said one side of the separation membrane to the second cylinder to act on the second plunger surface, valve means actuable during reverse movement of the second plunger surface to direct fluid from the second cylinder to an exhaust outlet, and drive means for effecting relative reciprocation of the plunger surfaces in the cylinders.

3. A fluid pressure device according to Claim 2, wherein the first and second plunger surfaces are mechanically interconnected in a plunger assembly.

4. A fluid pressure device according to Claim 3, wherein the plunger assembly is spring-biased in one direction of movement.

5. A fluid pressure device according to Claim 4, wherein the plunger assembly is spring-biased in the direction in which the first plunger surface is acting on the fluid.

6. A fluid pressure device according to Claim 3, 4 or 5, wherein the valve means is actuable by a collar mounted on the plunger assembly for limited movement the collar being connected with the drive means.

7. A fluid pressure device according to Claim 3, including a cylinder assembly provided with said cylinders, the drive means being connected with the cylinder assembly.

8. Afluid pressure device according to Claim 7, wherein the cylinder assembly carries the valve means which is engageable at the ends of the stroke of the assembly with actuating means.

9. A fluid pressure device according to Claim 7 or 8 including a valve arrangement to render the cylinders and plunger surfaces double-acting.

10. Fluid pressure apparatus including a plurality of pressure fluid devices according to any preceding claim including a common fluid inlet and a common separation membrane.

11. Fluid pressure apparatus according to Claim 10 including common drive means for the devices.

12. A fluid pressure device constructed substantially as herein described with reference to Figure 1, or Figures 1 and 2 of the accompanying drawings.

1 3. A fluid pressure device constructed substantially as herein described with reference to Figure 4 or Figure 5 of the accompanying drawings.

14. Fluid pressure apparatus constructed substantially as herein described with reference to Figure 3 of the accompanying drawings.