Multistage flash evaporator e.g. for desalination - comprises concentric vertical tubes and heating passage surrounding expansion chambers

摘要

In a multi-stage flash evaporator consisting of concentric vertical tubes, the heating passage is a narrow gap surrounding the expansion chambers. The feedstock is preheat in passing upwards through annulus between outer and inner pipes, and finally heated by e.g. steam or electricity in annulus. Used e.g. in prodn. of drinking water from sea water or brackish water, esp. in small quantities e.g. 1000 kg/h evaporation. The evaporator is more economical to build in small capacities than conventional evaporators. Its length is comparatively short and includes no bends where crystalline deposits can develop. The mean temp. difference is also high because of the absence of a multi-pass configuration. The evaporator is made up of a number of identical components and is thus cheap to produce.