Sodium chloride double-effect evaporator

Double-Effect Evaporation Technology and Advantages of Sodium Chloride :

• High Thermal Energy Economy: This is the most prominent advantage of double-effect evaporation. Theoretically, the steam consumption per ton of water evaporated can be reduced to approximately 0.5 tons, compared to single-effect evaporation (approximately 1.1 tons of steam/ton of water), achieving an energy saving rate of over 50%, significantly reducing operating costs.

• Suitable for Heat-Sensitive Materials: Double-effect evaporation operates at low temperatures under high vacuum (boiling points can be as low as 50-60℃), effectively avoiding potential damage to material components caused by high temperatures, making it particularly suitable for sodium chloride solutions containing volatile substances.

• High Degree of Automation: Modern double-effect evaporators integrate PLC or DCS automatic control systems, enabling one-button start/stop, automatic discharge, online cleaning (CIP), fault alarms, and other functions, ensuring continuous and stable system operation and reducing manual operation intensity and errors. 3.4 Significant Environmental Benefits: This technology achieves the resource recovery of sodium chloride from wastewater, turning waste into treasure. The final effluent is condensate with good water quality, which can be reused in production, truly achieving the environmental goals of "reduction, resource recovery, and harmlessness."

Components of a Sodium Chloride Double-Effect Evaporator

• Evaporator Unit: The core heat exchange component, typically employing a shell-and-tube forced circulation (FMCR) or natural circulation system. Given the tendency of sodium chloride to scale and form deposits, forced circulation is more common, effectively preventing scale buildup on the tube walls and ensuring heat transfer efficiency.

• Heating Chamber: The tube bundle assembly within the evaporator unit, where heat exchange occurs between steam and the material.

• Separator: Used to rapidly separate the secondary steam generated by evaporation from entrained droplets, ensuring steam cleanliness.

• Preheater: Utilizes the waste heat of the condensate or secondary steam to preheat the feed, further improving system thermal efficiency.

• Vacuum System: Typically composed of a water ring vacuum pump, hydraulic ejector, or steam jet pump, providing and maintaining the required vacuum environment for the second effect.

• Condenser: Condenses the unusable secondary steam generated in the final effect into water; both mixing and surface types are used.

• CIP Cleaning System: Regularly performs chemical cleaning of the equipment's interior, removing trace amounts of scale that accumulate during operation and ensuring long-term stable operation.

• Automated Control System: The "brain" of the system, providing real-time monitoring and precise control of key parameters such as temperature, pressure, flow rate, liquid level, and density.

Selection and Design Considerations

• Feed Characteristics: Accurate analysis of the feed's COD, pH, salinity, composition, boiling point elevation, etc., is the foundation of the design.

• Corrosive Material Selection: Sodium chloride solution is corrosive to carbon steel. The main equipment typically requires corrosion-resistant materials such as 2205 duplex stainless steel, 2507 duplex stainless steel, or titanium.

• Anti-Scale Design: Forced circulation, selecting appropriate flow rates, and implementing an online cleaning system are key to addressing sodium chloride scaling.

• Energy Integration: Assess the potential utilization of waste heat from the plant area and steam condensate to further optimize the energy structure.