Low temperature flash vaporization for desalination

The feasibility of desalination by low pressure vaporization of seawater at temperatures between 26°C and 32°C was demonstrated in a pilot plant. The plant operated at vacuum pressures between 1.3 KPa and 2.3 KPa. The saline water was sprayed into the vaporizer as fine droplets using a swirl nozzle and evaporated at the low pressure. The maximum flow rate was 1,000 1/h. Condensation of the vapor so formed, was carried out in a shell and tube heat exchanger. The yield of fresh water was up to 4% as predicted by theory. The quality of the condensed water was excellent. The investigation demonstrated a novel concept of devising a desalination system by using warm water from the upper strata of the ocean for flash vaporization at low pressures and condensing the vapors using cold water from the lower strata of the ocean. The performance of the pilot plant was determined for different feed water temperatures, vacuum and water injection pressures.