| 摘要 |
A batch evaporative desalination method and apparatus having a pair of similar systems for substantially continuous output is described. Each system has three evacuated chambers in vapor communication with each other. In the first chamber, precooled seawater is sprayed for partial vaporization and consequent formation of ice crystals as latent heat is removed from the seawater. Ice crystals are permitted to accumulate in the first chamber and water vapor flows to a second chamber in which refrigeration coils, preferably cooled by cold natural gas, are maintained at a temperature below the triple point so that ice condenses thereon. After a selected interval, spraying of precooled seawater into the first chamber and refrigeration in the second chamber are stopped. Warmer seawater is then sprayed into a third chamber also maintained at low pressure so that a portion of the water vaporizes but without formation of ice in the brine. The water vapor flows to the first and second chambers and condenses on the ice therein to transfer latent heat for melting the ice. Fresh water is withdrawn from the second chamber. Fresh water in the first chamber percolates through the ice crystals for washing and when residual brine is removed, fresh water is withdrawn from this chamber also. In a preferred embodiment, natural gas refrigerant is expanded through a turbine for producing shaft horsepower for pumping seawater. The apparatus is arranged with hydraulic legs beneath the first and third chambers at a height at least equal to the head of water at one atmosphere pressure for maintaining low pressure in the three chambers. In a preferred arrangement, a reversible refrigeration loop may be provided between a pair of second chambers for reversibly transferring heat therebetween.
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