Sodium Chloride MVR Evaporator

The sodium chloride MVR evaporator is a highly efficient and energy-saving device specifically designed for the concentration, crystallization, and solid-liquid separation of saline wastewater (especially sodium chloride solutions). It is not merely a simple evaporation device, but a key component for achieving "zero liquid discharge" of industrial wastewater.

I. Sodium Chloride MVR Evaporator Process and Design

Treatment of sodium chloride solutions differs fundamentally from the treatment of ordinary liquids, with the main challenges lying in "anti-scaling" and "forced circulation."

1. Principle: MVR Thermal Energy Cycle

Vapor Compression: The compressor draws in and compresses the secondary steam generated during evaporation, increasing its temperature and pressure, returning it to the heating chamber as high-temperature steam.

Energy Closed Loop: This process recovers the latent heat of the steam, ensuring that the system consumes almost no fresh steam after normal operation, only electrical energy to drive the compressor and circulation pump.

2. Structure: Forced Circulation (FC) Mode

Because sodium chloride crystallizes easily during concentration, ordinary falling film evaporators are prone to clogging. Therefore, sodium chloride MVR evaporators typically employ a forced circulation evaporator as their main structure.

2.1 High-Speed Circulation: A high-flow-rate, high-head circulation pump maintains the material in a high-speed turbulent flow state of 1.5-3.5 m/s within the heating tubes. This high-speed flow effectively flushes the tube walls, preventing salt crystals from depositing and forming scale on the heat exchange surface.

2.2 Crystallization Separation: When the solution is concentrated to supersaturation, salt crystals precipitate. The equipment is typically equipped with a dedicated crystallizer (such as DTB or OSLO type), utilizing density difference or baffle design to allow the crystals to settle and be discharged, while the clear liquid continues to circulate and evaporate.

II. Features and Advantages of Sodium Chloride MVR

1. Extreme Energy Saving: Compared to traditional multi-effect evaporators, energy consumption is reduced by 60%-80%. The energy consumption per ton of water evaporated is only about 1/3 to 1/5 of that of traditional processes, with electricity being the primary energy consumption.

2. Anti-Scale and Easy-to-Clean: The forced circulation design itself has anti-scale function. In addition, the equipment is typically equipped with a CIP (clean-in-place) system, which can automatically clean the heat exchange tube bundle periodically, ensuring long-term stable operation. 

3. Resource Utilization

3.1Production Water Reuse:The produced condensate is of high quality and can be directly reused in production, achieving water resource recycling.

3.2Salt Recovery: The precipitated sodium chloride crystals, after centrifugation and drying, can be sold as industrial salt or reused in production processes (such as the chlor-alkali industry), turning waste into treasure.

4. High Degree of Automation: Utilizing a PLC/DCS system for control, it automatically adjusts the feeding, discharging, compressor frequency, and cleaning cycle, enabling unattended operation.

III. Typical Application Scenarios

Sodium chloride MVR evaporators are widely used in industries that generate high-salt wastewater:

1. Chemical Industry: Treatment of high-salt mother liquor generated during chlor-alkali chemical, pesticide, dye, and intermediate production processes.

2. Environmental Engineering: Concentration treatment of electroplating wastewater, dyeing wastewater, coal chemical wastewater, and landfill leachate.

3. Food and Pharmaceutical Industries: Although the materials in these industries are usually relatively pure, the saline washing water or mother liquor generated during production also needs to be concentrated and recovered using this type of equipment.

IV. Sodium Chloride MVR Selection and Maintenance

1. Material Selection: Sodium chloride solution is highly corrosive at high temperatures and concentrations. Parts in contact with materials are typically made of 316L stainless steel; if the chloride ion concentration or temperature is extremely high, titanium or Hastelloy alloys should be used to prevent corrosion.

2. Compressor Selection: Select based on the evaporation rate and boiling point elevation. Roots type is typically chosen for small flow rates, while centrifugal type is chosen for large flow rates.

3. Pretreatment: The hardness, suspended solids, and COD (Chemical Oxygen Demand) of the influent must be strictly controlled. Excessively hard water can lead to unremovable scale buildup, a major cause of equipment failure.

The sodium chloride MVR evaporator uses "mechanical vapor recompression" technology to transform the energy-intensive evaporation process into a highly efficient, primarily electrical, recycling process. It not only solves the problem of discharging high-salinity industrial wastewater but also creates significant economic and environmental benefits for enterprises by recovering water resources and salt.