Feed is concentrated into solid crystals and pure water using crystallizers. Solid crystals are produced from a liquid solution through crystallization, a solid-liquid separation method. Liquid waste may be eliminated by crystallizers, resulting in zero liquid discharge (ZLD). Primary nucleation and secondary nucleation are the two phases in the crystallization process. The development of new crystals is called primary nucleation. Secondary nucleation is the key stage in the mass creation of crystals, and this is where they grow. Evaporative crystallization and cooling crystallization are two different types of crystallization.
A crystallizer is a device that feeds a heated saturated solution to a lagged, closed vessel that is kept under a vacuum; the solution evaporates and cools adiabatically, resulting in crystallization. The solution temperature is progressively lowered by flashing the solution in a vacuum. Crystallization occurs as the salt’s solubility is reduced. Preheating can be done with the resulted vapor stream. Alaqua is a vacuum crystallizer supplier in USA that also supplies other processing equipment to meet various industrial demands.
Process of Vacuum Cooling Crystallization
Vacuum cooling crystallization is mostly utilized for salts that lose solubility as the temperature drops. The multi-stage vacuum crystallizer K1-4 is fed a warm, virtually saturated solution. The pressure is progressively lowered in this scenario, allowing the solvent (water) to evaporate and the solution to cool to the boiling point. Salt crystallizes when you reduce the temperature. Air drawn in at the bottom of the crystallizer (air agitation) keeps this in suspension and transports it to the exit. The suspension is then pushed by the suspension pump SP to the cyclone ZY for thickening. In centrifuge Z, the liquid is separated again. In dryer T, the salt is dried. The resultant vapor steam can be condensed with cooling water in the mixing condenser MK or utilized to warm the mother liquor in the bath condenser BK. The use of steam jet pump D can lower the stage pressure and therefore the solution temperature even more. A vacuum pump VP is used to remove the inert gases.
Some of the advantages of Vacuum Crystallization are mentioned below:
- Crystallization under control
- Crystals are larger and more uniform
- Fines are reduced
- The color formation is reduced
- Crystal yield is high
Characteristics of Vacuum Cooling Crystallization
- Cooling surface incrustation (fouling) does not occur since no cooling surfaces in the form of heat exchangers are required for evaporation. As a consequence, the duration between cleaning processes is increased to the maximum.
- After salt separation, heat can be recovered by reheating the draining solution.
- It is feasible to operate with partial loads in a flexible manner.
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- It can be used in different manners.
- Impeller with a hydrodynamic design.
- Calandria has a smooth bottom and a low head for better circulation
- Seeding material is mixed quickly.
Variants of Vacuum Cooling Crystallization
- In order to optimize heat recovery, the number of steps should be increased.
- With or without separation of salt.
- Horizontal crystallizers with air agitation, an external circulation circuit (Forced Circulation, FC), or vertical crystallizers with draught tube and bottom flange stirrer (Draft Tube Baffled, DTB).
- Vacuum generators are created using vacuum pumps and/or steam jet pumps.
- By using acid condensation or refrigerating equipment and refrigerants, the pressures and therefore the discharge temperature of the solution/suspension is reduced.
- In mixing or surface condensers, the vapor from the last step is condensed.
Alaqua is a crystallizers supplier in USA along with other processing equipment supplier to fulfill various industrial processing equipment requirements worldwide. Along with processing equipment suppliers they also provide their services for equipment fabrication, commissioning and installation services, personnel training, field services, retrofitting services, and troubleshooting services. To know more about our processing equipment and services, feel free to contact us today!