Salt Crystallization and Concentration

industrial-plant-ammonia-synthesis-piping-photo_1041338-2536.jpg

Salt Crystallization and Concentration

Application Examples:

Sodium chloride (NaCl)
Sodium sulfate (Na₂SO₄)
Ammonium nitrate (NH₄NO₃) production
Contact Us

Process Role

Evaporation and concentration

Heating salt solutions to supersaturation for crystallization.

Cooling crystallization

Controlling temperature to precipitate solutes (e.g., Glauber’s salt cooling).

KDP PHE Selection

Anti-scaling design

Wide flow channels or embossed patterns to reduce clogging.

Materials

316L stainless steel (chloride-resistant) or nickel-based alloys (ammonium salt-resistant).

6d6e8e3f66934147bf94ffb6dee6203c.jpeg

Salt Crystallization & Concentration Process Flow

Typical Salts Produced: NaCl, Na₂SO₄, NH₄Cl, KCl

Here’s a detailed step-by-step explanation of the salt crystallization and concentration process, including equipment used (with emphasis on plate heat exchangers) and key technical parameters:

Key Stages：Feed Preparation

Input：

Raw brine

(e.g., seawater, salt lake brine, or industrial wastewater).

Pretreatment

Filtration: Remove suspended solids (sand, organics) via sand filters or centrifuges.

Chemical Treatment: Add NaOH/Na₂CO₃ to precipitate Ca²⁺/Mg²⁺ (softening).

Output

Clarified brine (20–25% salt concentration).

Key Equipment

Plate heat exchangers (PHEs) preheat brine to ~60–80°C using waste heat.

Key Stages：Evaporation Concentration

Objective:

Increase salt concentration to near saturation (e.g., ~28% for NaCl).

Method:

Multi-effect evaporation (energy-efficient) or mechanical vapor recompression (MVR).

Process:

Brine enters 1st-effect evaporator (heated by steam at ~120°C).

Water evaporates; concentrated brine flows to next effect at lower pressure/temperature.

Final concentrate exits at ~40–50% salt (super-saturated).

Role of Plate Heat Exchangers

Brine Heating:

PHEs transfer heat from steam/live vapor to brine.

Condensate Cooling:

Recover heat from vapor condensate.

Materials:

NaCl/KCl: 316L stainless steel PHEs.

NH₄Cl/Na₂SO₄: Titanium or nickel-alloy PHEs (anti-corrosion).

Key Stages：Crystallization

Objective:

Form uniform salt crystals from super-saturated brine.

Equipment:

Forced-circulation crystallizer or Oslo-type crystallizer.

Process:

Super-saturated brine enters crystallizer vessel.

Seeding: Add fine salt crystals to initiate controlled growth.

Cooling: Plate heat exchangers maintain ~30–50°C (for cooling crystallization) or ~60–100°C (for evaporative crystallization).

Crystals grow to 0.2–1.0 mm size.

PHE Application:

Cooling Duty:

Chilled water circulates through PHEs to remove latent heat.

Anti-Scaling Design:

Wide-gap plates or pulsed flow to prevent fouling.

Key Stages：Separation & Drying

Centrifugation:

Separate crystals from mother liquor (residual brine).

Equipment:

Screen-scroll centrifuges (moisture reduced to 3–5%).

Washing:

Spray with fresh water to remove impurities (optional).

Drying:

Fluidized-bed dryers (hot air at ~150°C) for final moisture <0.5%.

Packaging:

Sized crystals stored in silos or bags.

Heat Recovery:

PHEs recycle waste heat from dryer exhaust air to preheat incoming brine.

Process Flow Diagram (Simplified)

Clarified Brine (25%)

↓  

[Plate Heat Exchanger] → Preheat to 80°C  

↓  

[Multi-Effect Evaporator] → Concentrate to 40%  

↓  

[Crystallizer] + [PHE for Cooling/Heating]  

↓  

[Centrifuge] → Wet Crystals (5% H₂O)  

↓  

[Fluidized-Bed Dryer] → Dry Salt (<0.5% H₂O)  

↓  

[Packaging/Silo Storage]
MVR-Evaporator-Introduction-1.jpg
板式蒸发器.png

Role of KDP Plate Heat Exchangers (PHEs)

Brine Preheating:

Recovers heat from condensate/exhaust streams (30% energy savings).

Evaporator Feed Heating:

Uses steam/vapor to raise brine temperature.

Crystallizer Cooling:

Controls supersaturation by precise temperature adjustment.

Anti-Fouling Designs:

Detachable plates: For cleaning scale (CaSO₄, Mg(OH)₂).

Electropolished surfaces: Reduce crystal adhesion.

Key Technical Parameters

ParameterTypical Value
Brine feed conc.20–25% salt
Evaporation temp.60–120°C (multi-effect)
Crystallization temp.30–100°C (depends on salt type)
Crystal size0.2–1.0 mm
Energy consumption40–80 kWh/ton salt (MVR)

Comparison of Crystallization Methods

MethodCooling CrystallizationEvaporative Crystallization
Energy UseLower (chilling only)Higher (steam/vapor needed)
Salt TypesNa₂SO₄·10H₂O, NH₄ClNaCl, KCl
PHE RoleChilled water circulationSteam condensation

Optimization Tips

Scale Prevention

Use pulsed flow or ultrasonic PHEs to disrupt scaling.

Material Selection

NaCl: 316L stainless steel.

Ammonium salts: Titanium or Hastelloy.

Automation

Control supersaturation via real-time temperature monitoring.

Top