Patent EA-004968-B1 (EA)
Title: Process and plant for multi-stage desalination of water
Inventor: WILLSON PAUL MICHAEL
IPC: B01D3/06
Filed: 2001-07-18
Abstract: 1. A process for the desalination of salt water comprising the steps of: (a.) providing a brine heater; (b.) providing at least one desalination zone comprising a condenser and means for collecting condensate from the condenser; (c.) providing a heat exchanger; (d.) supplying a feed stream comprising salt water as a coolant to the condenser to pre-heat the feed stream; (e.) supplying the pre-heated feed stream to the brine heater; (f.) supplying a first heating stream comprising steam to the brine heater further to heat the pre-heated feed stream; (g.) optionally recovering at least a portion of the first heating stream from the brine heater; (h.) supplying the heated feed stream from the brine heater to the at least one desalination zone, evaporating at least a portion of the heated feed stream in the desalination zone to provide an evaporate comprising water vapor and condensing the evaporate on the condenser in the desalination zone; (i.) recovering from the desalination zone a product stream comprising the condensate and a depleted feed stream comprising salt water; (j.) supplying as a thermal recycle stream a portion of the product stream to the heat exchanger; (k.) supplying a second heating stream, optionally comprising at least a portion of the recovered first heating stream, to the heat exchanger to heat the thermal recycle stream; and (l.) supplying the heated thermal recycle stream to the at least one desalination zone. 2. A process for the desalination of salt water comprising the steps of: (a.) providing a brine heater; (b.) providing at least one desalination zone comprising a condenser and means for collecting condensate from the condenser; (c.) providing a heat exchanger; (d.) supplying a feed stream comprising salt water as a coolant to the condenser to pre-heat the feed stream; (e.) supplying the pre-heated feed stream to the brine heater; (f.) supplying a first heating stream comprising steam to the brine heater further to heat the pre-heated feed stream; (g.) optionally recovering at least a portion of the first heating stream from the brine heater; (h.) supplying the heated feed stream from the brine heater to the at least one desalination zone, evaporating at least a portion of the heated feed stream in the desalination zone to provide an evaporate comprising water vapor and condensing the evaporate on the condenser in the desalination zone; (i.) recovering from the desalination zone a product stream comprising the condensate and a depleted feed stream comprising salt water; (j.) supplying as a thermal recycle stream a portion of the depleted feed stream to the heat exchanger; (k.) supplying a second heating stream, optionally comprising at least a portion of the recovered first heating stream, to the heat exchanger to heat the thermal recycle stream; and (1.) supplying the heated thermal recycle stream to the at least one desalination zone. 3. A process for the desalination of salt water comprising the steps of: (a.) providing a brine heater; (b.) providing at least one desalination zone comprising a condenser and means for collecting condensate from the condenser; (c.) providing a heat exchanger; (d.) supplying a feed stream comprising salt water as a coolant to the condenser to pre-heat the feed stream; (e.) supplying a first portion of the feed stream as a pre-heated feed stream to the brine heater; (f.) supplying as a thermal recycle stream a second portion of the feed stream to the heat exchanger; (g.) supplying a first heating stream comprising steam to the brine heater further to heat the pre-heated feed stream; (h.) optionally recovering at least a portion of the first heating stream from the brine heater; (i.) supplying a second heating stream, optionally comprising at least a portion of the recovered first heating stream, to the heat exchanger to heat the thermal recycle stream; (j.) supplying the heated feed stream from the brine heater and the heated thermal recycle stream from the heat exchanger to the at least one desalination zone, evaporating at least a portion of the heated feed stream and the heated thermal recycle stream in the desalination zone to provide an evaporate comprising water vapor and condensing the evaporate in the desalination zone; (k.) recovering from the desalination zone a product stream comprising the condensate and a depleted feed stream comprising salt water. 4. A process according to claim 1, wherein the heated thermal recycle stream is supplied to the condensate collecting means of the desalination zone. 5. A process according to claim 4, wherein the ratio of thermal recycle stream to condensate in the collecting means of the desalination zone is from about 0.85: 1 to about 1.15: 1. 6. A process according to any one of claims 1 to 5, wherein there is provided a plurality of desalination zones connected in series. 7. A process according to claim 6, wherein the thermal recycle stream is taken from a first desalination zone and the heated thermal recycle stream is supplied to a second desalination zone. 8. A process according to claim 7, wherein the second desalination zone is nearer in the series of desalination zones to the brine heater than is the first desalination zone. 9. A process according to claim 8, wherein the first desalination zone is maintained at a lower pressure than the second desalination zone. 10. A process according to any one of claims 1 to 9, wherein the thermal recycle stream is supplied to the heat exchanger at a pressure greater than that of the second heating stream supplied to the heat exchanger. 11. A process according to any one of claims 1 to 10, wherein the feed stream is supplied to the brine heater at a pressure greater than that of the first heating stream supplied to the brine heater. 12. A process according to any one of claims 1 to 11, wherein the temperature of the thermal recycle stream is not more than 5 degree C greater than the saturation temperature of water in the at least one desalination zone. 13. A process according to any one of claims 1 to 12, comprising recovering at least a portion of the first heating stream from the brine heater. 14. A process according to claim 13, wherein the second heating stream comprises at least a portion of the recovered first heating stream. 15. A process according to any one of claims 1 to 14, wherein a plurality of heat exchangers for heating the thermal recycle stream are provided. 16. A plant for the desalination of salt water comprising means for operating a process according to any one of claims 1 to 15.