Process and plant for multi-stage flash desalination of water

摘要

In a multi-stage desalination process, the pre-heated recirculated feed stream is heated in brine heater 1 and then released to flash in first desalination stage via valve 3. The feed stream is flashed through a series of desalination zones 4, the steam condensing on tubes 5 cooled by the recirculated feed stream. Product water is collected in water trough 6, and flashes down between stages to heat rejection stage(s) 7. Feed stream is recirculated by pumps 8 through desalination and heat rejection zones. Non-condensible gases are extracted by ejectors 9. Condensing sections of heat exchange rejection stages are cooled by sea water 11. Warm sea water is recycled via deaerator 12 and make up pump 13. The thermal recycle stream may be a portion of the product stream, a portion of the depleted feed stream or the feed stream before it is supplied to the first heat exchange zone.