Introduction to Cryogenic Concentration Technology

Low temperature concentration technology is an innovative technology to separate salt water by simulating the natural evaporation and rainfall process; it is an important part of the sewage zero discharge project. Its working process is to use air or other gases to take out (humidify) the water molecules in the saline wastewater, and carry out wild knot (dehumidification) in another field, thus realizing the purpose of concentrating the saline wastewater.

As we all know, concentration is a key step in the zero discharge of salty wastewater. Most of the traditional concentration devices use membrane concentration + evaporative concentration. The limit of membrane concentration is generally not more than 10%, and further concentration to saturation requires evaporative concentration. The energy consumption of the entire concentration process is huge, usually accounting for more than 80% of the total energy consumption, and more energy-efficient processes must be adopted to reduce operating costs.

Traditional evaporation process

Membrane concentration process: Calcium and magnesium ions must be removed in advance, and silicon ions can easily cause membrane blockage, which is difficult to remove. At the same time, it is necessary to ensure that the pH is weakly alkaline, otherwise it is easy to cause membrane poisoning and necrosis, and the pretreatment requirements are very high: even if the pretreatment reaches the standard , there are also work requirements for frequent cleaning and frequent replacement, and the labor intensity and maintenance costs are relatively high: due to the limitation of osmotic pressure, the membrane concentration can only be concentrated to about 10% at most, and the zero-emission scheme still needs to continue to be concentrated in the future.
Evaporation and concentration process: high temperature operation, the stronger the corrosiveness of chloride ions, the higher the requirements for equipment materials; the higher the brine concentration, the higher the boiling point, the greater the energy consumption; the negative pressure operation is prone to the phenomenon of flooding, and the flying method is impacted with salt Compressors are easy to damage the equipment, and at the same time affect the effluent quality: high temperature operation, the actuator is more likely to be scaled, the efficiency of the actuator is seriously reduced, and the evaporation capacity cannot be reached: the high temperature operation has higher safety requirements for the device.
Low temperature concentration technology

Steam (can be secondary steam of crystallization, or waste heat and latent heat of the factory) heats the low-salt wastewater and enters the humidification tower, where mass transfer and heat transfer are carried out in the tower, and the nearly saturated water vapor enters the bottom of the dehumidification tower. Fresh air is blown into the bottom of the humidification tower, and when the concentrated water is nearly saturated, it is discharged to the next process. in the dewarming tower. The cold water sprayed from the top promotes the cooling and condensation of water vapor to generate fresh water, and the fresh water at the bottom of the tower is discharged up to the standard.