MVR Vacuum Evaporator

MVR vacuum evaporators represent a new generation of high-efficiency and energy-saving evaporation technology. They combine mechanical vapor recompression with vacuum evaporation to achieve thermal energy recycling. The core principle involves using a high-efficiency steam compressor to compress and heat the secondary steam generated during evaporation, increasing its enthalpy before reheating the feed liquid, forming a closed-loop thermal energy cycle with energy savings of 60%-90%.

I. Core Components and System Structure

The MVR vacuum evaporator consists of seven core systems:

1. Preheating System: Employs a shell-and-tube or plate heat exchanger to recover waste heat from the condensate and preheat the feed liquid to 60-80°C, fully utilizing the system's thermal energy and reducing energy consumption.

2. Evaporation Heater: Selected based on material characteristics, it can be a falling film, rising film, or forced circulation type. The falling film type uses a distributor at the top of the heat exchange tubes to form a uniform liquid film, resulting in a high heat transfer coefficient and no liquid column static pressure loss, making it particularly suitable for heat-sensitive materials.

3. Steam Compressor: The "heart" of the system, primarily available in centrifugal, Roots , and magnetic levitation centrifugal . The compressor pressurizes secondary steam at approximately 78℃ to 88-98℃, converting electrical energy into heat energy, achieving energy upgrading.

4. Vapor-Liquid Separator: Separates steam from concentrated liquid, equipped with a demister to prevent droplets from entering the compressor. For crystallization operations, a crystallizer function can be integrated, working with a forced circulation pump to complete the integrated evaporation and crystallization operation.

5. Vacuum System: Maintains negative pressure in the system using a vacuum pump, lowering the boiling point of the material to 60-85℃, protecting heat-sensitive components and reducing the compressor compression ratio, thus reducing power consumption.

6. Control System: Employs PLC/DCS for fully automatic operation, real-time monitoring of parameters such as temperature, pressure, liquid level, and concentration, automatically adjusting compressor speed and valve opening, enabling unattended operation and integration with smart factories. 7. Cleaning System: Equipped with a CIP online cleaning device, which periodically removes scale from heat exchange tubes using chemical solvents to ensure heat transfer efficiency. Titanium or duplex steel materials can extend the cleaning cycle.

II. Complete Workflow

Upon system startup, a small amount of live steam is first used to preheat the material to its boiling point. After stable operation, the workflow forms a closed loop:

1. Raw material preheating: The raw liquid is heated to the set value in stages through a condensate preheater and a steam preheater;

2. Vacuum evaporation: The preheated material enters the evaporation chamber and boils under negative pressure, generating secondary steam;

3. Steam compression: The secondary steam is pressurized and heated by the compressor , significantly increasing its enthalpy;

4. Heat recovery: The compressed steam enters the shell side of the heater, exchanges heat with the material in the tube side, and condenses into water, releasing latent heat to continue evaporating the material;

5. Condensation discharge: The condensate is pumped out of the system and can be reused or sent to a pure water system;

6. Concentration and crystallization: After the material concentration reaches the set value, it is discharged by a circulating pump; if crystallization is required, it is transferred to a crystallizer for further concentration, and centrifuged after the solid-liquid ratio of the crystal slurry reaches the standard.

This process is cyclical, consuming almost no live steam except during the start-up phase, relying solely on the compressor's electrical energy to maintain thermal balance. The economic efficiency of live steam is equivalent to that of a traditional 30-efficiency evaporator.

III. Technical Advantages and Features

1. Extreme Energy Saving: Evaporating 1 ton of water consumes only 15-30 kWh of electricity, just 1/5 the energy consumption of traditional triple-effect evaporators, reducing annual operating costs by 50%-70%.

2. Low-Temperature Protection: Vacuum evaporation temperatures can be as low as 30-60℃, making it particularly suitable for heat-sensitive materials such as amino acids, antibiotics, and traditional Chinese medicine extracts, preventing loss of active ingredients.

3. Environmentally Friendly: No cooling water system or boiler is required, resulting in no waste heat emissions and reducing carbon emissions by over 70%, aligning with the "dual carbon" target.

4. Automation and Intelligence: Industrial control computer + PLC + frequency converter technology enables fully automated control of the entire process. IoT technology allows integration with smart factory systems for remote monitoring and unattended operation.

5. Compact Structure: The footprint is reduced by over 60% compared to traditional multi-effect evaporators, and the modular skid-mounted design shortens the installation cycle to 2-4 weeks.

6. Strong Anti-scaling Properties: Low-temperature evaporation slows down the crystallization rate of inorganic salts such as calcium sulfate and sodium carbonate; the falling film evaporator has a fast liquid film flow rate, making it less prone to clogging; the smooth titanium surface makes it easier to clean.

IV. Application Areas

MVR vacuum evaporators are widely used in:

Environmental Protection: Electroplating wastewater, landfill leachate, RO concentrate with zero discharge , concentration ratio up to 10 times, mother liquor reduced to 10% of raw water;

Chemical Industry: Evaporation and crystallization of inorganic salts such as sodium sulfate, sodium chloride, and sodium persulfate, acid and alkali recovery;

Pharmaceutical Industry: Concentration of antibiotic fermentation broth, traditional Chinese medicine extracts, and amino acid wastewater, meeting GMP standards;

Food Industry: Concentration of fruit juice, whey protein, and soy sauce, preserving flavor and nutrition;

New Energy: Wastewater treatment in lithium battery cathode material production, recovering valuable metal salts.

V. Selection and Maintenance Considerations

Selection should consider material viscosity, scaling tendency, foaming tendency, corrosiveness, boiling point elevation, and processing capacity. Forced circulation evaporators are recommended for high-viscosity materials; falling film evaporators are preferred for heat-sensitive materials; and titanium or Hastelloy materials are necessary for corrosive media. Compressor selection is based on evaporation capacity and compression ratio; centrifugal compressors are used for high flow rates, while Roots or multi-stage cascade compressors are used for high compression ratios.

Key daily maintenance points: 

① Regularly lubricate and monitor the compressor for vibration to prevent impeller scaling; 

② Chemically clean the heat exchanger every 3-6 months to remove crystals; 

③ Check the vacuum pump's sealing to ensure stable vacuum levels; 

④ Backup control system parameters and periodically calibrate sensors.

MVR vacuum evaporators, with their revolutionary energy-saving concept and reliable operation, have become the preferred alternative to traditional multi-effect evaporators in the industrial evaporation field.