GB1377782A - Desalination of water by flash 'vaporation - Google Patents

Abstract

1377782 Flash-type evaporators; desalination of water SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ NV 27 Jan 1972 3864/72 Heading B1B [Also in Division F4] Coolant comprising liquefied natural gas, liquefied methane or water, which coolant has been cooled by heat exchange with liquified natural gas or liquified methane, flows countercurrent to water passing through a flash evaporator/condensor for desalination. Water coolant may be water subsequently passed through the flash evaporator/condensor for desalination. Thus, water, such as sea water, is desalinated by heating it in coal 17 and then passing it through chambers 1 to 6 where flash evaporation takes place, the vapours being condensed on condensers 9 to 14 cooled by passing therethrough the feed water which has been previously cooled to just above freezing point by heat exchange with liquefied natural gas or liquefied methane. The feed water is passed through coil 28; and the liquefied gas is passed countercurrently through coil 26. The condensate, i.e. desalinated water, is collected in tray 30. The feed water is heated in coil 17 by passing low-pressure steam through the adjacent coil 23. In a modified apparatus (Fig. 2, not shown) liquefied gas is used as cooling-medium in the condensers. In this case, the seawater need not be raised in temperature before evaporation, and the process can be operated so that the flashed steam initially condenses as ice on the condenser surfaces, but later condenses as water on the ice surfaces. Alternatively, the condensers may be arranged in parallel so that ice blocks may be released therefrom by passing warm gas through some of the condensers, while the others remain in service for condensing flashed steam as ice. The evaporator may be made of concrete.