Progressive Freezing Seawater Desalination Method And Microscopic Mechanism

China is one of the countries with water shortage in the world.Desalination of seawater has been highly valued as an important way to solve the shortage of fresh water resources.In recent years,the government of China has increased its support for clean energy and the LNG receiving station has flourished.A large amount of cold energy is released during the LNG vaporization process.If this part of cold energy can be used as a cold source in the freezing desalination,the cost will be greatly reduced,which will provide an opportunity for the promotion of the freezing desalination method.This thesis is divided into two parts.The first part is the experimental study on the desalination effect of the freezing seawater desalination experiment study at the macro level,including the experimental study of simple progressive freezing desalination and the gravity desalination experiment.The second part is the microscopic study of brine pockets and air bubbles in artificial brine ice using X-ray computed tomography.The experimental study mainly obtained the following conclusions:(1)The higher the freezing temperature is,the better the freeze desalination effect can be gotten.When the freezing temperature is–10?,the maximum salt removal efficiency is69.70%.(2)The freezing-gravity combined desalination method can effectively remove the salt of seawater.The slower the melting rate is,the better the gravity desalination effect is.For the original seawater with an initial TDS content of 35325mg/L,it was frozen almost completely at a freezing temperature of-24°C,and then the ice blocks were dealt with gravity desalination at an ambient temperature of 20°C.When the melting rate reached 80%,the three indicators of Cl~-content,TDS content and total hardness all reach the drinking water standard.(3)The pump consumption is greatly reduced for the freeze-gravity-reverse osmosis treatment compared with the direct reverse osmosis treatment,and the fresh water yield rate is improved compared with feezing-gravity desalination.(4)Comparing the two scanned segments of two NaCl-water solution ice samples whose initial concentration was 3wt%and 9wt%respectively,the area ratio and size of brine pockets of the latter sample are significantly larger,but the air bubble size of the two samples is similar.The size and equivalent diameter dispersion of the brine pockets increase from top to bottom for both the two samples.(5)The fractal dimensions of the brine pockets of sample with initial concentration of9wt%are overall larger than those with initial concentration of that of 3wt%sample,which indicates that the morphology of the brine pockets in the 9wt%ice sample is more complicated than that in the 3wt%ice sample.