Desalination Of Seawater By The Method Of Spray Freezing

The scarcity of fresh water has become the key restriction factor of economic development in the areas around Bohai Sea. But the largest water resource near it is sea water which can not be used directly. There is a large scope of sea ice in Bohai Sea in every winter. Salt separation from sea ice in freezing process results in lower salinity in sea ice, which may become a resolution to the water shortage problem in these areas.This research is the creative initiation of scientific research personnel. It is a method of using sea water indirectly and has Chinese Characteristic. The results are original innovation.During the formation of sea ice, the liquid brine should drain out into the underlying water from the sea ice structure. However, the process is limited by the very fast rate of sea ice formation which due to the abrupt drops of air temperature, some liquid brine has no enough time to drain out. As a result, the liquid brain is trapped with the sea ice structure to form so-called brain pocket. Sea ice is composed of polygonal ice crystal, brain pocket, air pocket and a bit of solid impurities. It is mixture and has salinity. The paper studies on the desalination of sea and sea ice by the method of spray freezing, gravitating and centrifugation respectively.For spray freezing desalination, transporting seawater into nozzle which is several meters high by the method of using pump. Through the nozzle, seawater changes its form by atomizing and becomes seawater droplets. Seawater droplets exchange heat with surrounding cold air, and part of the droplets are frozen by the cold air. During the experiment, the frozen raw sea ice was collected by nylon net, and brine was colleted by the basin beneath the nylon net. Due to the very fast process of sea ice formation, a great deal of liquid brine has no time to escape the ice structure, so the salinity of the raw sea ice is much more high than the sea ice formed in the nature environment. The experimental results showed that the salinity of seawater reduced to 12—15‰of raw sea ice from 25.5‰after spray freezing.For gravitating desalination, using gravitation as outside force which deserves on the mixture of sea ice and liquid brine and this outside force is powerful than the mucilaginous force which limits the brine to the sea ice surface. The experimental results showed that when environmental temperature was -4.0℃and gravitation time was 20h,the salinity of raw sea ice was reduced to 10.4‰from16‰, the rejection of sea ice is 35%.For centrifugation desalination, using centrifugal force as outside force which deserves on the mixture of sea ice and liquid brine and this outside force is powerful than the mucilaginous force and surface tension which limits the brine to the sea ice. By deserves the continues centrifugal force, the liquid brine will eventually leave the sea ice. The experimental results showed that when environmental temperature was 0℃and centrifugal time was 40min,and centrifugal velocity was 3000r/min,the salinity of raw sea ice was reduced to 2.9‰from 14.2‰, the rejection of sea ice is 79.57%.The above experiments showed that gravitating desalination and centrifugation desalination using sea ice as raw material which made by the method of spray freezing could reach good results.