US 4,432,876 AGranted

Reverse osmosis apparatus and method incorporating external fluid exchange

AssigneeSeagold Industries Corporation

InventorBowie G. Keefer

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Abstract

Reverse osmosis pump using a fluid volume exchange structure interconnecting pumping and expansion chambers of feed cylinder externally of feed cylinder. This structure permits exchange of volume between pumping and expansion chambers following initiation of induction or pumping stroke. Volume exchange provides a dwell interval to shift main directional valve across closed center position thereof, thus increasing tolerance to valve actuation, and also tends to equalize pressure differences across ports of the valve prior to opening of such ports, thus reducing erosion and valve gear wear. Also tends to reduce pressure differences across feed displacer, thus reducing sealing problems. Volume exchange structure can be a resilient diaphragm with no intermixing of fluid, mechanically timed valve permitting intermixing of fluid, or cross-over relief valves which are pressure responsive to permit intermixing of fluid.

Claims15

Dependent claims

Pumping apparatus for membrane separation apparatus for separating a feed fluid into permeate fluid and concentrate fluid fractions which respectively are permeated and rejected by selective membrane means, the pumping apparatus including:

a reciprocating feed pump having at least one feed cylinder with a feed displacer mounted on a feed displacer rod reciprocable within the feed cylinder, the cylinder and displacer rod having relative diameters which define cylinder interior/displacer rod proportions to determine in part the recovery ratio of permeate fluid fraction to total feed fluid flow;
a pumping chamber on one side of the displacer communicating with inlet conduit means to admit feed fluid, and with outfeed conduit means to conduct feed fluid to the membranes;
return conduit means to conduct concentrate fluid from the membranes to an expansion chamber on an opposite side of the displacer;
means to reduce fluctuations in pressure and fluid flow across the membranes, first and second valve means communicating with the expansion chamber and pumping chamber respectively and cooperating with the conduit means to direct fluid flow to and from the membrane means and to exhaust de-pressurized concentrate fluid fraction from the expansion chamber, the first valve means having a closed intermediate position between two open positions;
reciprocable drive means activating the feed displacer rod and first valve means whilst maintaining a phase difference or angle between the feed displacer stroke and actuation of the first valve means, the pumping apparatus including dwell means having fluid volume exchange means further characterized by:
(a) an exchange conduit means extending externally of the feed cylinder interior and interconnecting the pumping and expansion chambers,
(b) volume exchange control means within the exchange conduit to control volume exchange between the chambers,
so that fluid volume is exchanged between the chambers to approximately equalize pressure between the pumping and expansion chambers following reversal of feed displacer rod movement and to provide a dwell interval or angle sufficient to shift the first valve means across an effectively closed intermediate position thereof while initial movement of the feed displacer rod tends to equalize pressure differences across ports of the first valve means that are about to be opened prior to opening of such ports.

5 more elements

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 at least one feed cylinder with a feed displacer mounted on a feed displacer rod, the rod being driven by reciprocable drive means, the displacer dividing the cylinder into a pumping chamber for feed fluid and an expansion chamber for concentrate fluid, valve means determining fluid flow directions to and from the chambers and the membrane means, the method including steps of:

simultaneously inducting feed fluid into the pumping chamber and exhausting depressurized concentrate fluid from the expansion chamber;
followed by:
pressurizing feed fluid in the pumping chamber and simultaneously admitting pressurized concentrate fluid into the expansion chamber to supplement energy supplied to the feed displacer, the method being characterized by:
(a) following reversal of feed displacer rod movement, exchanging fluid volume between the pumping and expansion chambers externally of the feed cylinder interior so as to approximately equalize pressure difference across ports of a directional valve means that are about to be opened prior to opening of such ports, and essentially simultaneously shifting the first valve means across an effectively closed intermediate position thereof.

1 more element

Dependencies are inferred from the claim text.