Continuous Crystallization
There are two kinds of continuous crystallization, vacuum evaporating crystallization and vacuum cooling crystallization, determined by the solubility curve.
If the solubility curve is smooth, means solubility changes little along with temperature rising, we select vacuum evaporating crystallization, eg. Sodium chloride, sodium sulfate, ammonium sulfate, calcium chloride and etc;
If the solubility curve is steep, we select vacuum cooling crystallization, eg. Potassium chloride, potassium nitrate, copper sulfate, magnesium sulfate and etc.
Process Principle
Evaporating crystallizer is getting part of solvent evaporated and making the solution oversaturated, thus the crystals would be separated out.
There are various types of evaporating crystallizers, and according to the flow type, it could be divided into 2 types: mother liquor circulating type and crystal slurry (mother liquor+ crystals) circulating type. Mother liquor circulating type is able to get good quality crystals during evaporation, as the crystals is separated from the mother liquor and grows bigger at the bottom of the crystallizer, is generally adopted in case good quality crystals was requred. And crystal slurry circulating type is more simple in structure and lower in construction cost, is widely adopted in case there was solids produced during evaporation and no requirements on crystal size.
Application Scope
Multiple-effect crystallization evaporator is a high-efficiency and energy-saving evaporator, it works under condtion of high vacuum and low temperature, has features of high flow velocity, rapid evaporation efficiency, and free of fouling. It has been widely adopted in petrochemical industry, chlroine alkali chemical industry, fine chemical and etc, for wastewater treatment and production, and has successful application on sodium chloride, barium chloride, sodium sulfate, sodium sulfite, ammonium chloride, magnesium sulfate, magnesium nitrate, calcium chloride and etc.
1. Evaporate under condition of high vacuum and lower temperature, which ensure higher evaporation efficiency and less energy consumption;
2. Easy to operate because of Continuous input and output;
3. Forced circulating type process, makes feed material flowing at a higher viscosity and being evaporated easily even at a higher concentration;
4. Independent heatesr and separators is convenient for washing and maintenance;
5. All parts are made from high-quality stainless steel, parts contact with materials are well-polishe, external parts are pickling or matte finishing.
Multi-effect Vacuum Crystallization Evaporator is composed of multi sets of heaters , multi sets of separators , condenser, vacuum pump, forced circulation pumps, discharging pump, condensate pump, electrical cabinet, operation platform and all the pipe fittings, valves, instruments and etc.
Heater: vertical type tubular heater. The feed liquid is pumped into the heater by forced circulation pump. The heated liquid flow downwards in tubes, and flow into separator by tangential direction, better performance of vapor-liquid separation.
Separator: vertical type, the secondary steam is discharged from the top, pass through a vapor-liquid separator before entering into condenser. The bottom of separator is connected with a forced circulation pump.
