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Reverse osmosis method and apparatus

  • US 4,187,173 A
  • Filed: 03/14/1978
  • Issued: 02/05/1980
  • Est. Priority Date: 03/28/1977
  • Status: Expired
First Claim
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1. A method of membrane separation of a feed fluid into permeate fluid and concentrate fluid fractions which respectively are permeated and rejected by selective membrane means, the membrane means being exposed to pressurized feed fluid supplied by a reciprocating pump means having a cylinder and piston means and cooperating with valve means in conduit means, the piston means dividing the cylinder into a pumping chamber in which feed fluid is pressurized and an expansion chamber in which the concentrate fluid is depressurized;

  • the method being characterized by steps of;

    (a) inducting feed fluid into the pumping chamber by an induction stroke of the piston and simultaneously exhausting concentrate fluid from the expansion chamber,(b) reversing direction of force applied to the pump means and simultaneously hydraulically biasing the piston means against movement due to reversal of force so that reaction to reversal of force is transmitted to the valve means causing the valve means to shift in preference to relative piston means movement so as to mechanically shift the valve means to direct fluid flow between the pump means and the membrane means, the transfer of reaction forces causing a dwell period so that the valve means shifts across a closed intermediate position thereof during an interval of substantially zero fluid transfer in the expansion chamber thus incurring timely valve shifting,(c) pressurizing the feed fluid in the pumping chamber by a compression stroke of the piston means which forces pressurized feed fluid to the membranes, and admitting the concentrate fluid fraction from the membrane means into the expansion chamber to supplement energy supplied to the piston in the compression stroke by using pressure of the concentrate fluid,(d) separating the feed fluid into a permeate fluid fraction which passes through the membranes, and a concentrate fluid fraction which is returned from the membranes to the expansion chamber to recover some fluid pressure for pressurizing the feed fluid.

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