GB1096700A - Method and apparatus for distilling scale forming liquor - Google Patents

Abstract

Scale-forming liquor, e.g. sea water, is submitted to distillation by preheating the liquor, passing it through a multiple-effect evaporator, the first effect of which is operated at a temperature above 250 DEG F. e.g. at 315 DEG F., mixing the partially-concentrated liquor, withdrawn from the final effect, with unflashed liquor withdrawn from the last stage of a multi-stage flash evaporator, and passing the liquor admixture through the evaporating stages of the flash evaporator. The feed liquor is preheated by passing it through condensers traversing the upper part of the flash evaporator and then through a series of heat exchangers wherein it is heated by part of the vapours conducted from the heating chambers of the multiple-effect evaporator. After partial preheating in the condenser of the heat rejection section of the flash evaporator, the feed sea water may be degasified by mixing it with acid and passing it through a vessel which is attached to a barometric condenser and a steam-jet ejector. The degasified sea water then flows through the condensers of the heat recovery section of the flash evaporator. The multiple-effect evaporator may be of the type wherein the liquor flows in film-form down long vertical heat-transfer tubes, or flat plate-type heat transfer surfaces can be used. Each effect may be associated with a flash tank for distillate. Reference is made to the concentration of sodium aluminate liquor obtained by the alkaline extraction of bauxite.