Freeze desalination by the integration of falling film and block freeze-concentration techniques

Block and falling film freeze concentration are two technologies that separate water by freezing, with the potential to desalinate seawater. In this study, the integration of two freeze concentration techniques as an alternative to obtain potable water was analysed. Water with 0.5%-8% NaCl was freeze-concentrated by the falling film technique. The ice from each stage was fractionally thawed to recover the solids retained in the ice. The diluted fractions of the thawing stage were freeze-concentrated using the block technique to increase water purity. Falling film freeze concentration was effective to separate the salt from the solution, even at high salt concentrations. Block freeze concentration was effective to increase the water purity until drinkable water was obtained. A multistage process with the integration of these techniques was proposed to obtain 74% of the amount of the initial solution at 0.05% of salt, and 26% at 13.4% of salt. With this process, a salt removal efficiency of 98.5% was achieved. The energy consumption was analysed. The integration of these techniques results in water that meets the requirements for drinkable water and demonstrates the technical feasibility of the process.