What is the reason for Sodium chloride multi-effect evaporation crystallization
What is the reason for Sodium chloride multi-effect evaporation crystallization? Why can sodium chloride be extracted by evaporation and crystallization? Next, let's understand the reasons why sodium chloride can be crystallized by evaporation.
In the treatment of industrial wastewater and salt-containing wastewater, it is often seen that the Sodium chloride multi-effect evaporation crystallization process is used to treat salt-containing and high-salt wastewater.
What is the reason for Sodium chloride multi-effect evaporation crystallization? Before understanding this problem, let us first understand what is evaporation crystallization.
1. The principle of evaporation and crystallization
Evaporative crystallization refers to heating and evaporating the solvent, so that the solution is changed from unsaturated to saturated. If the evaporation continues, the excess solute will precipitate out as crystals. When the solution is evaporated and crystallized, the solution is dissipated (evaporated) by the solvent, so that the solution reaches a saturated state, and then reaches a supersaturated state. The use of evaporative crystallization generally needs to be used for the evaporative crystallization and purification of product solutions whose solubility is not greatly affected by temperature. For the use of evaporative crystallization, the solubility curve can be observed.
2. What is the reason for Sodium chloride multi-effect evaporation crystallization?
After understanding the principle of evaporation crystallization, let's take a look at the conditions and environment of Sodium chloride multi-effect evaporation crystallization. Generally, sodium chloride solution needs to crystallize out of the material liquid, and the material liquid needs to continuously obtain heat energy from the outside to make the material liquid The water is continuously evaporated and concentrated to make it reach a supersaturated state.
By observing the solubility of sodium chloride and the increase in the boiling point of sodium chloride, it can be seen that compared with other salts, sodium chloride has a very narrow metastable range, and it is more difficult to obtain crystals with a larger particle size. To make the crystal grow, the solution must be supersaturated and controlled in the metastable zone. The supersaturation of the solution is completely used for the growth of the seed crystal.
Under the same conditions of time and the same solution supersaturation concentration difference, the higher the temperature of the solution, the lower the viscosity of the solution, the faster the diffusion rate of the solute, and the faster the growth rate of crystals.
The above is the reason for Sodium chloride multi-effect evaporation crystallization, which is mainly based on the solubility and boiling point rise of sodium chloride solution.