Desalination of seawater or brackish water is a proven technology for more than 50 years which provides fresh water to millions of people living in areas of water scarcity, whether for drinking or other uses, such as hygiene and even agricultural, helping these communities not only to survive, but to achieve their economic, technological and environmental development. Unfortunately, current commercial desalination requires a large amount of energy, either caloric or electric and mostly covered by conventional sources, increasing both costs and environmental pollution. Freezing desalination can theoretically achieve up to 70 % less energy use than thermal technologies, with other advantages such as that it does not need pre-treatment and low corrosion in the system. The present work shows the results obtained during the experimentation in a prototype of desalination plant of sea water by freezing, coupled to a solar cooling system, managing to increase water production for each energy unit used and it is presented an analysis of salt percent obtained in water produced.
Abstract:Considering the important demand of fresh water and its scarce availability, water 18 desalination is an interesting technology, producing about 44 Mm 3 /year worldwide, but, in general 19 the most common desalination techniques are highly energy demanding. Freezing-Melting (F/M) 20 desalination uses just up to 70% less thermal energy, but is the least used process mainly, due to the 21 difficulty of the salt separation. This study proposes a model able to analyses the thermodynamic 22 potential that allows the salt diffusion during the F/M process, using an aqueous solution of sodium 23 chloride. This should allow to obtain a sensitive analysis of the process to promote the separation 24 between the high concentration brine and the ice with liquid separation by physical process. The 25 unidimensional model is based on the evolution of both processes: thermal and mass diffusions, 26 depending on temperature and saline gradients, predicting whether the salt will remain inside the 27 ice or not. Thus, the thermal potential is adjusted to frozen only when the salt has been "pushed" 28 towards the brine. Mostly models have base their results on the assumption of a "certain value of 29 saline concentration of the liquid fraction", value in which there is great disagreement. In this paper 30 the calculations are based on the concentration in the solid-liquid interface, which has been 31 extensively studied and there is a coincidence in those results, being the main advantage of the 32 proposed model. 33Keywords: freezing/melting desalination process; aqueous solutions of sodium chloride; theoretical 34 diffusive models 35 36
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