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Purification of gases from water using reverse osmosis

  • US 5,670,053 A
  • Filed: 08/07/1995
  • Issued: 09/23/1997
  • Est. Priority Date: 08/07/1995
  • Status: Expired due to Fees
First Claim
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1. A process for purifying water including removing cations, anions, carbon dioxide and/or ammonia from a water feed stream to produce high purity water having a resistivity of greater than 1 megohm-era, comprising the steps of:

  • (a) providing water feed stream to be purified, said stream containing cations, anions, carbon dioxide and/or ammonia;

    (b) pretreating said feed stream by passing said feed stream through a nonofiltration membrane to remove membrane foulants prior to introducing said feed stream to a first reverse osmosis membrane;

    (c) introducing said water feed stream to a high pressure side of a first reverse osmosis membrane module;

    (d) passing water through said first reverse osmosis membrane to provide a first retentate having cations and anions concentrated therein and a first permeate depleted in cations and anions and containing carbon dioxide and/or ammonia;

    (e) passing said first permeate to a high pressure side, of a first gas permeable hydrophobic membrane module, andpermeating carbon dioxide and/or ammonia through said gas-permeable membrane from said first permeate in the high pressure side of said gas-permeable hydrophobic membrane to provide a carbon dioxide and/or ammonia permeate on a low pressure side of said hydrophobic membrane and to provide a carbon dioxide and/or ammonia depleted retentate thereby removing carbon dioxide and/or ammonia from said first permeate;

    (f) maintaining the low pressure side of said hydrophobic membrane liquid free and subjecting said low pressure side of said hydrophobic membrane to a gas purge to remove carbon dioxide or ammonia that has permeated the hydrophobic membrane; and

    (g) transferring said carbon dioxide and/or ammonia depleted retentate to the high pressure side of a second reverse osmosis membrane, andfurther purifying said carbon dioxide and/or ammonia depleted retentate by passing at least a portion thereof through said second reverse osmosis membrane to provide a second retentate and a second permeate, the second permeate having low levels of carbon dioxide and/or ammonia and having a resistivity of greater than 1 megohm-cm.

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