Dispersion of Secondary Refrigerant Liquids in NaOH Solution by Mechanical Agitation

Abstract

Four low boiling organic compounds of Fron-11, Fron-12, Fron-114 and n-butane were selected and used in this experiment, as usable secondary refrigerants for the crystallization of NaOH·2H₂O in NaOH solution by secondary refrigerant freezing method. The hold up and drop size distribution of the dispersed refrigerant liguid (dispersion phase) in 49.1% NaOH solution were directly measured by taking photographs and using a glass vessel equipped with an agitator.
The limited agitator speed for dispersion was determined with the correlation between the hold up and agitator speed. The total surface area of dispersion phase was calculated by using the hold up and the average drop diameter.
The limited agitator speed was correlated to the density difference between the dispersion phase and the solution, and then, was increased according to the order of Fron-11, Fron-114, Fron-12 and n-butane. But, the total surface area of the dispersion phase, which was related to the evaporation rate of the secondary refrigeran tin the NaOH·2H₂O crystallizer, was mainly characterized by the viscosity of the dispersion phase, and the total surface area of dispersed Fron-12 liquid was larger than that of Fron-11.
From these experimental results, it was found that Fron-12 was the most suitable secondary refrigerant for the crystallization of NaOH·2H₂O.