Dual-effect salt separation and purification equipment

Process Principle 

The dual-effect salt separation and purification equipment utilizes multi-effect evaporation crystallization technology. By gradually concentrating the feed solution, the salts reach a supersaturated state and crystallize out. This system typically includes a primary purification unit, a secondary purification unit, and a tertiary purification unit. Different temperature and pressure conditions are used to achieve salt separation and purification.

Process Flow

1. Primary Purification Unit: Using multi-effect evaporation, the feed solution is gradually concentrated at each effect, continuously increasing the concentration of sodium sulfate and sodium chloride until a supersaturated state is reached, causing them to gradually precipitate as mixed salt crystals at the salt bottom.

2. Secondary Purification Unit: The sodium sulfate and sodium chloride crystals produced in the primary purification unit are used to prepare a saturated, nitrate-rich mother liquor. Sodium sulfate is then precipitated as decahydrate nitrate through freeze crystallization.

3. Tertiary Purification Unit: Using membrane separation technology, sodium chloride and sodium sulfate are further separated from the lean nitrate mother liquor produced in the secondary purification unit.

Advantages

High-purity products: Through multi-stage purification, the produced sodium chloride and sodium sulfate are of high purity, with a high salt recovery rate.

High adaptability: Capable of treating high-salinity wastewater of various concentrations and properties, unaffected by organic matter, nitrates, and impurities.

Energy saving and environmental protection: Reduces energy consumption and operating costs through heat exchange and steam reuse.

Applications

Chemical industry: Treats wastewater containing inorganic salts such as sodium chloride and sodium sulfate, achieving salt recovery and reuse.

Environmental protection: Treats high-salinity wastewater such as landfill leachate and reverse osmosis concentrate, reducing wastewater discharge and environmental pollution.

Challenges and Solutions

Scale and corrosion: High-salinity wastewater easily leads to scale and corrosion in equipment. Solutions include using corrosion-resistant materials (such as titanium and Hastelloy), regular equipment cleaning, and adding scale inhibitors.

Energy consumption: Although double-effect evaporation technology has reduced energy consumption, it remains a concern for large-scale treatment. Solutions include further optimizing process parameters and adopting multi-effect evaporation technologies.

The dual-effect salt separation and purification equipment achieves effective treatment and resource utilization of high-salinity wastewater through multi-stage purification processes, and is one of the important technologies in the field of high-salinity wastewater treatment.