Desalination of salt water by drip freezing at winter sprinkling

Abstract

The purpose of the research is to evaluate the efficiency of winter sprinkling for desalination of seawater. The ice fraction in an individual drop and in a stream of drops in a free fall is estimated. At the air temperatures of −10 and −40 °C, the percentage of ice in a stream of water drops with a mineralization of 35 g/l may amount to 12 and 39%, respectively. Calculations showed that when producing porous ice from water with a mineralization of 35 g/l by means of sprinkling at the same air temperatures, the productivity of the DDN–70 sprinkler system will be equal to 670 (−10 °C) and 2190 (−40 °C) tons of ice per day. When the fraction of ice in the drops of stream increases, the salinity of unfrozen water grows too, and this results in increasing of the porous ice salinity. Experiments did show that at mineralization of the source water of 10 g/l, the moisture content of porous ice amounts 12%, while in the ice frozen from seawater it is 23%. The humidity of a salt porous ice makes influence on the desalination efficiency. At a moisture content of porous ice of 12% and melting of 30% of its volume, the mineralization of the remaining part is 4 times less than that at the a moisture content of 23%, but if the melting reaches 50% of the volume it is 16 times. It was found that with growth of salinity of frozen water the performance of sprinkling and efficiency of desalinization decrease. However, it should be noted that when using sea water with a salinity of 35 g/l after melting of 50% of the porous ice volume, the salinity of the remaining part of water will amount approximately 1 g/l, and after appropriate sanitary and hygienic treatment, it can be used for drinking water supply. It is important also that such water will contain in sufficient amounts the necessary microelements.