Vacuum desalination using waste heat from a steam turbine

Abstract

The process reported is known as vacuum desalination. This technique takes advantage of the drop in boiling point of sea water if pressure is reduced. By doing so, the temperature of a turbine exhaust steam is sufficiently high to cause boiling of sea water at the pressure of about 10 kPa. The system comprises of a saturated vapour heater and superheated vapour heater. Initially, the sea water is converted to a wet steam in the saturated vapour heater after receiving heat from a superheated steam which is due for condensation. The dry component of the wet steam is then channelled to the superheated vapour heater and is heated to superheated condition by the turbine waste steam. The system is designed in such a way that heat from the superheated steam is reused for heating up the incoming sea water in the saturated vapour heater. The consumption of heat from the turbine waste steam is kept to a minimum and most of which is to compensate for heat losses in the system. In the saturated vapour heater, the superheated steam after rejecting its latent heat to the incoming sea water is condensed and is pumped out from the system by a positive displacement pump.