A Fundamental Study on Separation Of Wasted Water by Freezing

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In the first year, influences of a shape of stirring wing, rotational frequency brine temperature and separation apparatus on a shape of ice, an adhesion of ice to a cooling wall and a separation efficiency were discussed. A 1000 ml of ethylene glycol solution(10 vol %) was used as a wasted water. From experimental results, it was found that there was little influence of the wing shape on concentrations of diluted and/or concentrated solutions. Besides, by setting to 150 - 300 rpm, ice particles among which concentrated solution was hardly trapped could be formed without adhesion of ice to the wall.In the second year, a new experimental apparatus was produced on the basis of experimental results of the previous year. By using the apparatus, at the same solution temperature and separation time, the concentration of diluted solution could be reduced from 5.7 vol % to 2.5 vol %.In order to improve the separation efficiency, it is important that concentrated solution is not trapped among formed ice particles. Hence, it is effective that the sizes of ice particles were made to be larger And then, effects of a cooling rate (brine temperature), degree of super-cooling and size of stirring wing which were expected to affect the sizes of ice particles were discussed. In the case of brine temperature at -6 ℃, the concentration of diluted solution was lower because an amount of separated ice was approximately equal to the ideal value. While, it was recognized that sizes of ice particles ; increased as the degree of super-cooling decreased and/or size of stirring wing increased. However, it wasn't confirmed that they affected remarkably improvement of the separation efficiency. Moreover, increase of the wing size made ice shape be flaky. For suppress of adhesion to the wall, it was useful that a small amount of silane-coupler was added.