OSLO crystallizer

OSLO Cooled Crystallizer

1. Basic Principle: 

• A circulating pump forces a supersaturated solution to flow from bottom to top, ensuring full contact with suspended crystals, promoting crystal growth, and causing them to settle to the bottom and be discharged.

2. Structure and Operation Flow:

• Feeding: A small amount of hot concentrated solution (approximately 0.5%~2%) is added to the feed inlet and mixed with the upper saturated solution.

• Circulation and Cooling: The mixed solution enters the cooler through a circulation pipe (controlling the temperature difference between the solution and coolant to ≤2℃), creating a supersaturated state.

• Crystallization Process: The cooled solution enters the crystallizer from the bottom and flows upwards, contacting the suspended crystals. Crystal nuclei form within the crystal bed and gradually grow. Fine crystals are separated by a hydrocyclone separator and recirculated.

• Product Discharge: Crystals reaching the predetermined size settle to the bottom and are continuously or intermittently discharged through the outlet.

3. Key Parameters:

• Feed rate, temperature, cooling capacity, circulation speed, crystal nucleus removal rate, etc.

4. Features and Applicability: 

• Suitable for materials where the solubility of the solute decreases significantly with decreasing temperature (such as copper sulfate and nickel sulfate).

• Crystal particle size and yield can be adjusted by controlling parameters.

• Note: Supersaturation control is necessary to avoid premature crystal nucleation.

OSLO Evaporative Crystallizer

1. Basic Principle: 

A supersaturated state is created by heating and evaporating the solution, causing the solute to deposit and crystallize on the surface of suspended crystal grains.

2. Structure and Operation Flow:

Feeding and Mixing: The feed solution is added to the circulation pipe, mixed with the circulating mother liquor, and then pumped to the heater.

Evaporation and Crystallization: The heated solution enters the flash evaporator, where it evaporates to generate steam (maintaining constant pressure).

The supersaturated solution flows upward from the bottom of the crystallizer, passing through the crystal fluidized bed, where the solute deposits on the crystal surface, causing it to grow.

Crystal Classification and Circulation: The fluidized bed hydraulically classifies the crystal grains. Large particles are discharged at the bottom, while fine particles are reheated and circulated with the mother liquor. Tiny crystals are dissolved during heating.

3. Features and Applicability: 

The supersaturation generation zone is separated from the crystal growth zone, providing a stable growth environment.

Suitable for producing products with uniform particle size (such as sodium chloride, sodium dichromate, etc.).

Can be connected in series for multi-effect operation to improve efficiency.

Disadvantages: Solute easily deposits on the heat transfer surface; operation is relatively complex, limiting applications.

Similarities and Differences

1. Similarities: 

Both are continuous crystallizers with mother liquor circulation, where crystals grow in suspension within the circulating liquid.

The crystallization process and product characteristics are adjusted by controlling parameters.

2. Differences:

Cooling type: Relies on temperature reduction to achieve supersaturation; suitable for temperature-sensitive materials.

Evaporation type: Achieves supersaturation through evaporation and concentration; requires maintaining pressure conditions; the structure includes a flash evaporation chamber.

Applications: Widely used in chemical, pharmaceutical, and food industries to produce high-purity, uniformly sized crystalline products, such as inorganic salts, organic acids, and metal salts.

The OSLO crystallizer achieves a highly efficient and stable crystallization process through its unique dual-effect design (cooling or evaporation) and mother liquor circulation mechanism. The appropriate type can be selected based on the material characteristics to meet production needs. However, attention must be paid to optimizing operating parameters and maintaining the equipment to avoid problems such as heat transfer surface deposition.