GB1013871A - Distillation system of the vapour-compression type - Google Patents

Abstract

1,013,871. Distillation apparatus of the vapour-compression type; distilling saline water. AQUA-CHEM Inc. April 23, 1963, No. 15925/63. Heading BIB. Liquid such as saline water is submitted to distillation in an apparatus of the vapourcompression type having a heat-exchanger comprising tubes 38, 40, inclined at a small angle to the horizontal, the saline water being preheated and sprayed downwardly from nozzles 36 over the outer surface of the tubes of the heat-exchanger. The vapours evolved from the saline water are compressed in compressor 45 and introduced into the tubes of the heat-exchanger where the vapours condense, the distillate being withdrawn by pump 62. Some of the concentrated brine withdrawn from hot-well 14 is mixed with fresh feed and conveyed to spray-manifold 32. The remainder of the concentrated brine is discharged from the system via control valve 68 and conduit 74. The rate of spraying of the mixture of recirculated brine and raw feed from the nozzles 36 is preferably such that the weight of vaporizable liquid flowing over the tubes at any time is from 4 to 10 times the weight of distillate being produced inside the tubes. In order to inhibit scale formation, a chemical additive is added to the saline water. Tetrasodium pyrophosphate, sodium tripolyphosphate or sodium hexametaphosphate may be used as additive when the water is vaporized at a temperature of about 190 ‹F.; but when the vaporization-temperature is higher, e.g. 212 ‹F., sulphuric acid, hydrochloric acid, sodium bisulphate, sulphamic acid or citric acid is used as additive. The saline water, which is introduced into the system through conduit 10, flows through heat-exchanger 64 where it is heated by the distillate and by the waste-brine, which are discharged from the system via conduits 75 and 74 respectively. The warm saline water is treated with additive, to prevent scaling, from tank 150; and the treated water is sprayed down vessel 90, which is provided with perforated trays or with packing, in countercurrent flow to gases, which de-aerate the water. Gases from the tubes of the heat-exchanger pass through conduit 102 into the vaporizing chamber; and the gases next flow into the de-aerator 90 through conduit 100. The pH of the de-aerated water is adjusted, if necessary, by addition of alkali from tank 153; and the water then flows to hot-well 14 via conduit 99. The water-to-besprayed is withdrawn from hot-well 14 by pump 22, and is raised to boiling-temperature in heater 26. The treatment of sulphite liquors is mentioned.