Production of purified water and high value chemicals from salt water
First Claim
1. A method of producing purified water and sodium chloride from salt water that contains sodium chloride, the method comprising:
- feeding the salt water to a reverse osmosis unit;
operating the reverse osmosis unit to separate the salt water into a permeate of purified water which is recovered and a retentate that contains sodium chloride that is concentrated with reference to the salt water;
feeding the retentate to an electrodialysis unit having a plurality of membranes, wherein at least one electrodialysis membrane is a univalent anion-selective membrane and at least one other electrodialysis membrane is a univalent cation-selective membrane;
operating the electrodialysis unit to separate the retentate into a diluate that is depleted in sodium chloride with reference to the retentate, and a concentrate that is concentrated in sodium chloride with reference to the retentate, wherein at least a portion of the diluate is recycled back to the feed to the reverse osmosis unit;
feeding the concentrate to a salt-recovery unit; and
operating the salt-recovery unit to recover sodium chloride from the concentrate.
1 Assignment
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Accused Products
Abstract
Sodium chloride and purified water are recovered by treating salt water that contains sodium chloride with an integrated reverse osmosis and electrodialysis system, which includes an efficiency-enhancing feature that is one or more of the following: the use of univalent anion and univalent cation selective membranes in the electrodialysis unit; the addition of a nanofiltration unit to process the diluate from the electrodialysis unit; or operation of the electrodialysis unit at an elevated pressure. Magnesium and bromine can optionally be produced when the salt water contains these materials.
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Citations
60 Claims
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1. A method of producing purified water and sodium chloride from salt water that contains sodium chloride, the method comprising:
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feeding the salt water to a reverse osmosis unit;
operating the reverse osmosis unit to separate the salt water into a permeate of purified water which is recovered and a retentate that contains sodium chloride that is concentrated with reference to the salt water;
feeding the retentate to an electrodialysis unit having a plurality of membranes, wherein at least one electrodialysis membrane is a univalent anion-selective membrane and at least one other electrodialysis membrane is a univalent cation-selective membrane;
operating the electrodialysis unit to separate the retentate into a diluate that is depleted in sodium chloride with reference to the retentate, and a concentrate that is concentrated in sodium chloride with reference to the retentate, wherein at least a portion of the diluate is recycled back to the feed to the reverse osmosis unit;
feeding the concentrate to a salt-recovery unit; and
operating the salt-recovery unit to recover sodium chloride from the concentrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of producing purified water and sodium chloride from salt water that contains sodium chloride, the method comprising:
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feeding the salt water to a reverse osmosis unit;
operating the reverse osmosis unit to separate the salt water into a permeate of purified water which is recovered and a retentate that contains sodium chloride that is concentrated with reference to the salt water;
feeding the retentate to an electrodialysis unit having a plurality of membranes;
operating the electrodialysis unit to separate the retentate into a diluate that is depleted in sodium chloride with reference to the retentate, and a concentrate that is concentrated in sodium chloride with reference to the retentate;
feeding the diluate to a nanofiltration unit;
operating the nanofiltration unit to selectively concentrate divalent ions in the diluate into an NF retentate and to produce an NF permeate that is depleted of divalent ions with reference to the diluate, and wherein at least a portion of the NF permeate is recycled back to the feed to the reverse osmosis unit;
feeding the concentrate to a salt-recovery unit; and
operating the salt-recovery unit to recover sodium chloride from the concentrate. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 34, 35)
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24. A method of producing purified water and sodium chloride from salt water that contains sodium chloride, the method comprising:
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feeding the salt water to a reverse osmosis unit;
operating the reverse osmosis unit to separate the salt water into a permeate of purified water which is recovered and a retentate that contains sodium chloride that is concentrated with reference to the salt water;
feeding the retentate to an electrodialysis unit that is designed to operate at an elevated pressure and which has a plurality of membranes;
operating the electrodialysis unit at the elevated pressure to separate the retentate into a diluate that is depleted in sodium chloride with reference to the retentate, and a concentrate that is concentrated in sodium chloride with reference to the retentate, wherein at least a portion of the diluate is recycled back to the feed to the reverse osmosis unit;
feeding the concentrate to a salt-recovery unit; and
operating the salt-recovery unit to recover sodium chloride from the concentrate. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 36)
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37. An apparatus for recovering sodium chloride and purified water from salt water containing sodium chloride, the apparatus comprising:
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a pump that is designed to feed salt water from a source of salt water to a reverse osmosis unit that is designed to produce a permeate of purified water and a retentate that contains sodium chloride that is concentrated with reference to the salt water, wherein the reverse osmosis unit is operatively connected to transfer the retentate to an electrodialysis unit comprising a plurality of ion-exchange membranes, wherein at least one membrane is a univalent anion-selective membrane and at least one other membrane is a univalent cation-selective membrane, and wherein the electrodialysis unit is designed to separate the retentate into a diluate that is depleted in sodium chloride with reference to the retentate, and a concentrate that is concentrated in sodium chloride with reference to the retentate, wherein the electrodialysis unit is operatively connected to transfer at least a portion of the diluate to the feed to the reverse osmosis unit, and is also operatively connected to transfer the concentrate to a salt-recovery unit that is designed to recover sodium chloride from the concentrate. - View Dependent Claims (38, 39, 40, 41, 42)
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43. An apparatus for recovery of sodium chloride and purified water from salt water containing sodium chloride, the apparatus comprising:
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a pump that is designed to feed salt water from a source of salt water to a reverse osmosis unit that is designed to produce a permeate of purified water and a retentate that contains sodium chloride that is concentrated with reference to the salt water and, wherein the reverse osmosis unit is operatively connected to transfer the retentate to an electrodialysis unit which is designed to separate the retentate into a diluate that is depleted in sodium chloride with reference to the retentate, and a concentrate that is concentrated in sodium chloride with reference to the retentate, wherein the electrodialysis unit is operatively connected to transfer the concentrate to a salt-recovery unit that is designed to recover sodium chloride from the concentrate, and wherein the electrodialysis unit is operatively connected to transfer at least a portion of the diluate to a nanofiltration unit that is designed to selectively concentrate divalent ions in the diluate into an NF retentate and to produce an NF permeate that is depleted of divalent ions with reference to the diluate, and wherein the nanofiltration unit is operatively connected to recycle at least a portion of the NF permeate back to the feed to the reverse osmosis unit. - View Dependent Claims (44, 45, 46, 47, 48, 49, 50, 51, 52)
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53. An apparatus for recovery of sodium chloride and potable water from salt water comprising:
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a pump that is designed to feed salt water from a source of salt water to a reverse osmosis unit that is designed to produce a permeate stream of potable water and a retentate stream that contains sodium chloride that is concentrated with reference to the salt water, and wherein the reverse osmosis unit is operatively connected to transfer the retentate to an electrodialysis unit that is designed to operate at elevated pressure and is designed to separate its feed into a diluate that is depleted in sodium chloride with reference to the feed, and a concentrate that is concentrated in sodium chloride with reference to the feed, wherein the electrodialysis unit is operatively connected to recycle at least a portion of the diluate back to the feed to the reverse osmosis unit, and wherein the electrodialysis unit is operatively connected to transfer the concentrate to a salt-recovery unit that is designed to recover sodium chloride from the concentrate. - View Dependent Claims (54, 55, 56, 57, 58, 59, 60)
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Specification