Rotary shaft driven reverse osmosis method and apparatus

• US 4,288,326 A
• Filed: 04/06/1979
• Issued: 09/08/1981
• Est. Priority Date: 03/14/1978
• Status: Expired due to Term

• Current Assignee: Seagold Industries Corporation Canada
• Original Assignee: Seagold Industries Corporation Canada
• Inventors: Keefer, Bowie G.
• Primary Examiner(s): SPEAR JR, FRANK
• Application Number:
  US06/027,664
• Time in Patent Office: 886 Days
• Field of Search: 417/541, 417/374, 210/321 R, 210/433 M, 210/416 M, 210/136, 210/134, 210/137
• US Class Current: 210/637
• CPC Class Codes: B01D 2313/18 Specific valves
• CPC Class Codes: B01D 2313/246 Energy recovery means
• CPC Class Codes: B01D 61/06 Energy recovery
• CPC Class Codes: C02F 1/441 by reverse osmosis
• CPC Class Codes: F04B 1/02 having two cylinders in V-arrangement F04B1/04
• CPC Class Codes: F04B 11/0083 the pistons having different cross-sections
• CPC Class Codes: F04B 5/02 with double-acting pistons
• CPC Class Codes: F04B 53/143 Sealing provided on the piston
• CPC Class Codes: F04B 7/0053 for reciprocating distribution members
• CPC Class Codes: F05B 2220/62 for desalination
• CPC Class Codes: Y02A 20/131 Reverse-osmosis
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

Reverse osmosis, particularly for water desalination, uses semipermeable membranes which selectively permeate purified water from a feed solution pressurized by a reciprocating feed pump driven by rotating crankshaft. Pump action is assisted by depressurizing concentrate fluid within the pump cylinder, which has an internal displacer separating feed and concentrate fluids. Directional valves controlling concentrate fluid flow to and from pump cylinder are actuated mechanically by crankshaft. A dwell interval is provided in displacer motion to permit completion of directional valve actuation while displacer is stationary and displacer rod is providing compression or decompression action to approximately equalize pressure differences across valve ports prior to valve actuation. Detrimental concentration polarization is reduced by reducing pressure and flow fluctuations across membranes by using a differential surge absorber, a multi-feed cylinder pump in which the feed cylinders are phased apart, or a single feed cylinder pump with one or more recirculating cylinders phased equally from the feed cylinder to supply pulses of recycled concentrate fluid. In the multi-cylinder pumps, actuation of the piston rod of one cylinder can be used to actuate a directional valve of another cylinder, which can be a spool valve integral with displacer rod.

Claims

1. A pumping apparatus for a membrane separation apparatus for separation of a feed fluid into permeate fluid and concentrate fluid fractions which respectively are permeated and rejected by selective membrane means, the pumping apparatus being characterized by:

(a) a reciprocating feed pump means having a feed cylinder, a feed displacer and a feed displacer rod, the feed displacer dividing the feed cylinder into a pumping chamber in which the feed fluid is pressurized and an expansion chamber in which the concentrate fluid fraction is depressurized, the displacer cooperating with the displacer rod extending through the expansion chamber with sealing means to prevent leakage of fluid from the cylinder, the cylinder and displacer rod having relative diameters which define cylinder/displacer rod proportions such that ratio of swept volume of displacer rod to swept volume of the displacer determines in part recovery ratio of permeate fluid fraction to total feed fluid flow,

(b) inlet conduit means communicating with the pumping chamber to admit feed fluid into the pumping chamber,

(c) outfeed conduit means adapted to communicate the pumping chamber with the membranes so as to conduct pressurized feed fluid from the pumping chamber to the membranes,

(d) return conduit means adapted to communicate the membranes with the expansion chamber so as to conduct the concentrate fluid fraction from the membranes to the expansion chamber,

(e) means communicating with the outfeed and return conduit means to reduce fluctuations in pressure and fluid flow across the membrane means,

(f) first and second valve means, the first valve means communicating with the expansion chamber and having a closed intermediate position between first and second positions, the second valve means being non-return valve means communicating with the pumping chamber, the first and second valve means cooperating with the conduit means so as to direct fluid flow from a feed fluid source, and to and from the membrane means, and to exhaust depressurized concentrate fluid fraction from the expansion chamber,

(g) rotatable drive means activating the feed displacer rod and the first valve means whilst maintaining a phase angle difference between the feed displacer stroke and first valve means actuation,

(h) dwell means associated with the pump means and the drive means to ensure that the first valve means is shifted across the closed intermediate position thereof during an interval of essentially zero fluid transfer from the cylinder by the displacer after the beginning of each stroke of the displacer rod, the dwell means being characterized by a yieldable means associated with the feed displacer and the displacer rod to permit relative axial movement between a portion of the feed displacer and the feed displacer rod in response to reversal of pump action, and cooperation between the feed displacer and drive means being such that there is a dwell interval between valve actuation and displacer movement sufficient to approximately equalize pressure differences across ports of the first valve means that are about to be opened prior to opening of such ports,

so that in a first position of the first valve means, pressurized feed fluid from the pumping chamber is fed to the membranes through the second valve means while pressurized concentrate fluid is discharged into the expansion chamber through the first valve means, so that depressurization of the concentrate fluid returning from the membrane means assists in pressurizing of the feed fluid, and in a second position of the first valve means depressurized concentrate fluid is exhausted from the expansion chamber through the first valve means while feed fluid is inducted into the pumping chamber through the second valve means.

2. Pumping apparatus as claimed in claim 1 in which the yieldable means associated with the feed displacer is characterized by:

(a) the feed displacer rod being a piston rod means having a pair of spaced stop means,

(b) the feed displacer having a piston disc with a bore accepted as a sliding fit on the piston rod, the piston disc being interposed between the stop means, space between the stop means and thickness of the disc permitting relative axial sliding between the disc and the piston rod limited by the stop means,

so that stroke of the piston rod means is greater than stroke of the piston means to permit timely valve shifting.

3. Pumping apparatus as claimed in claim 2 further characterized by:

(a) sufficient clearance existing between the bore of the piston disc and the piston rod means to permit transfer of fluid between the piston disc and the piston rod means.

4. Pumping apparatus as claimed in claim 1 in which the displacer, displacer rod and dwell means are characterized by:

(a) flexible diaphragm means attached to piston rod means and separating the pump chamber from expansion chamber,

so that resilience of the diaphragm provides dwell to permit timely valve shifting.

5. Pumping apparatus as claimed in claim 1 in which the yieldable means associated with the feed displacer and displacer rod are characterized by:

(a) a flexible dished piston disc mounted on a piston rod means, the disc deforming such that travel of an outer rim thereof is less than travel of the piston rod means.

6. Pumping apparatus as claimed in claim 1 further characterized by:

(a) the displacer being a piston means which is vented and has passage means to permit transfer of fluid across the piston means between the pumping chamber and the expansion chamber.

7. Pumping apparatus as claimed in claim 1 in which the drive means for the pump means and the dwell means is characterized by:

(a) a rotating shaft having displacement and dwell means cooperating therewith so that after the first valve means has been shifted to attain one of the first or second positions thereof, the direction of displacement of the feed displacer is reversed to transfer fluid to and from the feed cylinder.

8. Pumping apparatus as claimed in claim 7 further characterized by:

(a) the rotating shaft having crank throws and respective rod connecting means coupled to the displacer rod and first valve means respectively, the throws being spaced apart so as to provide the desired phase difference between the valve actuation and pump stroke.

9. A pumping apparatus as claimed in claim 1 further characterized by:

(a) a plurality of feed cylinders where the number of cylinders in a cooperating set is factored by an odd number greater than one, each cylinder having respective feed displacers reciprocable within the respective cylinders, each feed displacer dividing the respective cylinder into a pumping chamber and an expansion chamber, each displacer having a displacer rod extending through the expansion chamber to cooperate with the rotatable drive means in such a manner that the feed displacers are phased angularly equally apart,

(b) the inlet conduit means communicating with respective pumping chambers to admit feed fluid into the pumping chambers.

(c) the outfeed conduit means communicating each pumping chamber with the membrane means so as to conduct pressurized feed fluid from the pumping chambers to the membrane means,

(d) the second valve means communicating with the inlet conduit means and the outfeed conduit means to control direction of feed fluid fed into and out from the pumping chambers,

(e) return conduit means communicating the membrane means with the expansion chambers of each cylinder so as to conduct the concentrate fluid fraction from the membrane means to the expansion chambers,

(f) the first valve means cooperating with the rotatable drive means so that the valve means of each cylinder is phased at a dwell angle relative to the drive means of the respective cylinder to provide the desired dwell interval between respective valve actuation and corresponding feed displacer movement.

10. A pumping apparatus as claimed in claim 9 further characterized by:

(a) the first valve means of each cylinder is actuated by a displacer rod means of another cylinder separated by a phase angle which differs from 90°

by half of the dwell angle.

11. A pumping apparatus as claimed in claim 1 in which the reciprocating feed pump means has a first feed cylinder and the means (e) is further characterized by:

(a) second and third similar feed cylinders, each cylinder means having a respective feed displacer reciprocable within the respective cylinder, each feed displacer dividing the respective cylinder into a pumping chamber and an expansion chamber, each feed displacer having a feed displacer rod extending through the respective expansion chamber to cooperate with the rotatable drive means in such a manner that the three rods are phased one hundred and twenty degrees apart,

(b) the inlet conduit means communicating with respective pumping chambers to admit feed fluid into the pumping chambers,

(c) the outfeed conduit means communicating each pumping chamber with the membrane means so as to conduct pressurized feed fluid from the pumping chambers to the membrane means,

(d) the second valve means communicating with the inlet conduit means and the outfeed conduit means to control direction of feed fluid fed into and out from the pumping chambers,

(e) return conduit means communicating the membrane means with the expansion chambers of each cylinder so as to conduct the concentrate fluid fraction from the membrane means to the expansion chambers,

(f) the first valve means cooperating with the rotatable drive means so that the first valve means of each cylinder is phased relative to the drive means to provide a nominal dwell interval of approximately sixty degrees between valve actuation and displacer movement to effect fluid transfer.

12. A pumping apparatus as claimed in claim 9 or 11 further characterized by:

(a) the first valve means of each feed cylinder being a slidable valve spool connected with the respective feed displacer rod so that the valve spool connected to the displacer rod of one cylinder controls the direction of pressurized concentrate fluid flow from the membrane means to the expansion chamber of one of the remaining feed cylinders.

13. A pumping apparatus as claimed in claim 11 in which the rotatable drive means is a crankshaft having three crank throws spaced apart at phase angles of one hundred and twenty degrees, each crank throw cooperating with a respective rod connecting means to reciprocate concurrently the respective spool and associated feed displacer rod.

14. A pumping apparatus as claimed in claim 11 or 13 further characterized by:

(a) the first, second and third feed cylinders having respective first, second and third valve spools and valve chambers, each spool being reciprocable within the respective valve chamber and rigidly connected to the respective feed displacer rods,

(b) each valve chamber having at one end thereof interconnected concentrate fluid return conduit means, at an opposite end thereof interconnected exhaust fluid conduit means, and adjacent an intermediate position between ends of the chamber an intermediate concentrate fluid conduit means interconnecting the valve chamber of one cylinder with an expansion chamber of one of the remaining cylinders, so that phase difference between each valve and its respective cylinder is about 120 degrees in the same direction of rotation,

so that at a particular instant when the first valve of the first valve chamber is in an intermediate position, the intermediate concentrate fluid conduit of the first valve chamber is closed, the second spool is positioned to exhaust depressurized concentrate fluid from the expansion chamber of the third cylinder, and the third spool is positioned to direct pressurized concentrate fluid from the membranes into the expansion chamber of the first cylinder.

15. A pumping apparatus as claimed in claim 1 in which the means to reduce fluctuations in pressure and feed fluid flow across the membrane means is characterized by:

(a) a recirculating cylinder having a recirculating displacer reciprocable therein and a recirculating displacer rod connected therewith, the recirculating displacer dividing the cylinder into front and rear chambers, the recirculating displacer rod extending through the rear chamber, the front chamber communicating with the membrane means, and the rear chamber communicating with the expansion chamber of the feed cylinder,

(b) recirculating conduit means, and transfer conduit means, and valve means cooperating with the recirculating cylinder to direct concentrate fluid from the front chamber to the membranes on a pumping stroke of the recirculating cylinder, and to direct concentrate fluid from the rear chamber to the front chamber on a return stroke of the recirculating cylinder,

(c) the rotatable drive means cooperating with the recirculating displacer rod so that the recirculating cylinder is phased equally from the feed cylinder,

(d) the first valve means is connected to the drive means and is phased at a desired phase angle from the feed cylinder, and communicates with the rear chamber of the recirculating cylinder and the expansion chamber of the feed cylinder.

16. A pumping apparatus as claimed in claim 15 in which the first valve means is further chracterized by:

(a) poppet valve means communicating with the rear chamber of the recirculating cylinder and the intermediate concentrate conduit means, and cooperating with the rotatable drive means so as to be phased equally from the actuation of the feed cylinder,

so that the concentrate conduit means connect the rear chamber of the recirculating cylinder with the expansion chamber of the feed cylinder for a pumping stroke of the feed cylinder to direct pressurized concentrate fluid into the expansion chamber and the second intermediate conduit means connects the expansion chamber to exhaust for an induction stroke of the feed cylinder.

17. A pumping apparatus as claimed in claim 15 or 19 in which the transfer valve means and transfer conduit means are characterized by:

(a) the recirculating displacer rod being a recirculating piston rod means having spaced apart inner and outer piston disc stops, the outer stop having transfer bore means extending therethrough and spaced radially of the piston rod means,

(b) the recirculating displacer being a recirculating piston means having a piston disc having a central bore accepting and being slidable on the piston rod means between the spaced stops,

so that on a return stroke of the recirculating piston means when the disc is adjacent the outer stop, the transfer bore means of the outer piston disc stop are registrable with the central bore of the piston disc and sufficient clearance exists between the inner disc stop and the piston disc to permit fluid flowing between the chambers to pass through the central bore and transfer bore means, and on a pumping stroke of the recirculating piston means the central bore of the piston disc is sealed against the inner disc stop.

18. A pumping apparatus as claimed in claim 15 or 19 in which the transfer valve means and transfer conduit means are characterized by:

(a) the recirculating displacer being a recirculating piston disc mounted rigidly adjacent an outer end of a recirculating piston rod means, the disc having transfer conduit means passing therethrough,

(b) transfer valve means adapted to seal or open the transfer conduit means in response to fluid pressure,

so that on a pumping stroke of the recirculating piston disc the transfer valve means closes the transfer conduit means, and on a return stroke the transfer valve means opens the transfer conduit means.

19. A pumping apparatus as claimed in claim 1 in which the means to reduce fluctuations in pressure and feed fluid flow across the membrane means is characterized by:

(a) at least two recirculating cylinders, each cylinder having a respective recirculating displacer reciprocable therein and a recirculating displacer rod connected therewith, each recirculating displacer dividing its cylinder into respective front and rear chambers, the recirculating displacer rods extending through the rear chambers, the front chambers communicating with the membrane means, and the rear chambers being connected together and communicating with the expansion chamber of the feed cylinder,

(b) recirculating conduit means, and transfer conduit means valve means cooperating with each recirculating cylinder to direct concentrate fluid from the front chamber to the membranes on a pumping stroke of the recirculating cylinder, and to direct concentrate fluid from the rear chamber to the front chamber on a return stroke of the recirculating cylinder,

(c) the rotatable drive means cooperating with the recirculating displacer rods so that the recirculating cylinders are phased equally from the feed cylinder,

(d) the first valve means is connected to the drive means and is phased at a desired phase angle from the feed cylinder, and communicates with the rear chambers of the recirculating cylinders and the expansion chamber of the feed cylinder.

20. A pumping apparatus as claimed in claim 19 in which the return conduit means includes:

(a) first intermediate concentrate conduit means extending between the rear chambers of the recirculating cylinders and the first valve means so that the first valve means communicates with at least one rear chamber of the recirculating cylinders,

(b) second intermediate concentrate conduit means extending from the first valve means to the expansion chamber of the feed cylinder to direct concentrate fluid to and from the expansion chamber of the feed cylinder.

21. A pumping apparatus as claimed in claim 20 in which the first valve means is further characterized by:

(a) a valve spool and a valve chamber communicating with a rear chamber of a recirculating cylinder and the first and second intermediate concentrate conduit means, the valve spool being reciprocable within the valve chamber and connected to the recirculating displacer rod of one of the recirculating cylinders so as to be phased at a desired dwell angle from the actuation of the feed cylinder,

so that the first and second intermediate concentrate conduit means connect the rear chamber of the recirculating cylinders with the expansion chamber of the feed cylinder for a pumping stroke of the feed cylinder to direct pressurized concentrate fluid into the expansion chamber, and the second intermediate conduit means connects the expansion chamber to exhaust for an induction stroke of the feed cylinder to exhaust depressurized concentrate fluid.

22. A pumping apparatus as claimed in claim 19 further characterized by:

(a) the recirculating displacer rods of the recirculating cylinders each having displacements of about one half of the displacement of the feed displacer rod of the feed cylinder.

23. A pumping apparatus as claimed in claim 19 further characterized by:

(a) the recirculating conduit means extending from the forward chambers of the recirculating cylinders to the membrane means, with the recirculating valve means provided in the recirculating conduits,

(b) the transfer conduits extending from the forward chambers to the rear chambers of the recirculating cylinders with the transfer valve means in the transfer conduits.

24. A pumping apparatus as claimed in claim 23 or 17 further characterized by:

(a) the recirculating and transfer valves are pressure responsive check valves.

25. Pumping apparatus as claimed in claim 1 in which the means to reduce fluctuations in fluid flow and pressure across the membranes includes:

(a) a differential surge absorber means communicating with the outfeed and return conduit means and interposed between the membrane means and the first and second valve means to absorb pressure fluctuations in the feed fluid flow.

26. Pumping apparatus as claimed in claim 25 in which:

(a) the differential surge absorber is a cylinder and a piston means, the piston means being spring-loaded and double-acting and reciprocable with the cylinder, the cylinder and piston means of the differential surge absorber being of similar proportions to the feed cylinder and feed displacer rod of the feed pump means but having a displacement several times greater.

27. Pumping apparatus as claimed in claim 25 in which the differential surge absorber is characterized by:

(a) a cylinder and a piston means, the piston means dividing the cylinder into a concentrate surge absorber chamber and a feed surge absorber chamber, the feed surge absorber chamber being exposed to pressurized feed fluid in the outfeed conduit means and the concentrate surge absorber chamber being exposed to the concentrate fluid fraction in the return conduit means,

(b) the piston means cooperates with a piston rod means extending through the concentrate surge absorber chamber with sealing means to seal the surge absorber against leakage,

(c) spring means cooperating with the piston means to force the piston in a direction to exhaust the feed surge absorber chamber.

28. Pumping apparatus as claimed in claim 27 in which the piston means of the differential surge absorber is characterized by:

(a) a flexible diaphragm means attached to the piston rod means and separating the feed surge absorber chamber from the concentrate surge absorber chamber.

29. Pumping apparatus as claimed in claim 1 in which:

(a) the first valve means is a two-position, center-closed three-way valve having a movable spool, the spool having a closed center and being adapted to travel between the two positions.

30. Pumping apparatus as claimed in claim 1 in which the first valve means is characterized by:

(a) a cam means cooperating with the rotatable drive means,

(b) a pair of normally-closed, two-way poppet valves to close respective conduit means, the poppet valves being unseated and opened by the cam means, the cam means being adapted to unseat and open one poppet valve whilst leaving the reamining poppet valve seated and closed.

31. A method of membrane separation of a feed fluid into permeate fluid and concentrate fluid fractions which are respectively permeated and rejected by selective membrane means, the membrane means being exposed to pressurized feed fluid supplied by a reciprocating feed pump means having a feed cylinder, a feed displacer and a feed displacer rod, the displacer dividing the cylinder into a pumping chamber in which feed fluid is pressurized and an expansion chamber in which concentrate fluid is depressurized, valve means in conduit means associated with the chambers determining fluid flow directions to and from the membrane means, the method being characterized by steps of:

(a) as the displacer rod initiates an induction stroke, permitting yielding between portions of the displacer and the displacer rod so that there is relative movement therebetween,

(b) whilst inducting feed fluid into the pumping chamber, simultaneously exhausting depressurized concentrate fluid from the expansion chamber,

(c) after the end of the induction stroke of the feed displacer, shifting the valve means across a closed intermediate position thereof during an interval of zero fluid transfer from the cylinder by the displacer, and when pressure difference across the valve means is relatively low,

(d) as a displacer rod initiates a pumping stroke, permitting yielding between portions of the displacer and the diplacer rod so that there is relative movement therebetween,

(e) whilst pressurizing feed fluid in the pumping chamber to force the pressurized feed fluid to the membrane means, simultaneously admitting into the expansion chamber pressurized concentrate fluid fraction from the membrane means to depressurize the concentrate fluid fraction to supplement energy supplied to the feed displacer in the pumping stroke, so that pressure differences across the displacer are relatively low,

(f) after the end of the pumping stroke of the feed displacer, shifting the valve means during an interval of zero fluid transfer in the expansion chamber and when pressure difference across the valve means is relatively low.

32. A method as claimed in claim 31 further characterized by:

(a) upon initiation of an induction stroke and upon initiation of a pumping stroke, simultaneously permitting limited intermixing across the feed displacer of fluid in the expansion and pump chambers.

33. A method as claimed in claim 31 further characterized by:

(a) pumping concentrate fluid across the membranes from a recirculating cylinder coupled to the feed pump means, the recirculating cylinder being phased equally apart from the feed cylinder,

so that a recirculating pulse of re-cycled concentrate fluid is phased equally from a main pulse of feed fluid so as to reduce fluid pressure and flow fluctuations across the membranes and to reduce fluctuations in the torque requirements for the drive means.

34. A method as claimed in claim 31 further characterized by:

(a) pumping concentrate fluid across the membranes from a pair of recirculating cylinders coupled to the feed cylinder means, the recirculating cylinders being phased equally apart from the feed cylinder and from each other,

so that two recirculation pulses of recycled concentrate fluid are phased equally from each main pulse of feed fluid so as to smooth fluid pressure and flow fluctuations across the membranes and to reduce fluctuations in the torque requirements for the drive means.