CRYSTALLIZATION OF A NaCl SOLUTION IN A VACUUM CENTRIFUGAL FILM DISTILLER
Keywords:Crystallization, Centrifugal distiller, Microgravity, NaCl
Background. The use of centrifugal forces in heat exchangers provides high efficiency of heat and mass transfer processes and allows creating devices that are operable under microgravity conditions. The short contact time of the solution with the heat exchange surface prevents deposits of dissolved substances when concentration of the solution increases. As a result, the centrifugal distillation apparatus can operate as a crystallizer, which provides an increase in the coefficient of water recovery in the life support systems for deep space missions.
Objective. The purpose of the paper is investigation of a single-stage centrifugal flash-boiling distiller for concentration of a NaCl solution.
Methods. Experimental studies on a prototype of centrifugal vacuum single-stage distiller.
Results. The results were obtained by concentrating a NaCl solution and in the crystallization mode (when precipitation of dissolved NaCl crystals begins). The physicochemical temperature depression was determined depending on the concentration of the solution and the pressure in the apparatus with quality control of the obtained distillate. The results were compared with the data of other authors, and the match was pretty good. Using a filter in a hot circuit allows you to work in crystallizer mode without the appearance of deposits on the structural elements of the apparatus.Conclusions. Intensive heat transfer in a centrifugal apparatus ensures the complete operation of the solution overheating, which makes it possible to use it to study the physicochemical temperature depression of solutions at different pressures. In this case, the quality of the distillate does not depend on the concentration of dissolved substances in the hot circuit (and in the crystallization mode). The use of the filter in the hot circuit allows the system to operate in crystallizer mode until the filter becomes clogged. After replacing the filter, the process can be extended.
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