Salt is obtained by processing and refining salt-containing brine or seawater after crystallization.

Sea water is introduced into the salt on the beach, and sunlight and wind are used to gradually evaporate the water and slowly concentrate it, so that the salt is crystallized to extract potassium chloride from the salt brine The salt brine left over after sunning contains potassium chloride, magnesium chloride, and a small amount of sodium chloride.

Three substances can be used to separate them from the different solubility. Analysis of the solubility of the three substances shows that the solubility of magnesium chloride (54.3 g) is greater than the solubility of potassium chloride and sodium chloride at room temperature (20°C). Therefore, by adding an appropriate amount of water to the mixture at room temperature, most of the magnesium chloride can be dissolved in water, and thus the magnesium chloride can be separated and removed.

Then, according to the characteristics that the solubility of potassium chloride is more than the solubility of sodium chloride below 27 ℃, the sodium chloride can be dissolved in water by adding appropriate amount of water to the remaining mixture for the second time, so as to obtain the crude product of potassium chloride. The crude potassium chloride is further crystallized and recrystallized to obtain the refined potassium chloride.

Salt refining methods:

1, evaporation method: evaporation method is the oldest way for human beings to obtain salt crystals, refers to the use of solar radiation and heat evaporation to the way of salt, which can be applied to the sea salt, lake salt and pool salt.

2, boiling salt method: also known as boiling method, is the use of fire evaporation brine to concentrate the way to make salt. Its form has the earliest stone pot type by flat pot type, steam use type, vacuum type and today's pressurized and vacuum type.

3, freezing method: freezing method is the use of water molecules solidified into solid ice, and will not be combined with other ions of the characteristics of the way to make salt, mostly for the frigid countries used. This method is to freeze the salt solution precipitation of chloride ions and sodium ions into brine, and then after several freezes to make it crystallize into salt.