Low-Temperature MVR Evaporator

I. Working Principle

The core principle of a low-temperature MVR (Mechanical Vapor Recompression) evaporator is based on the combination of a heat pump cycle and negative pressure evaporation, achieving closed-loop energy utilization.

1. Low-Temperature Evaporation: A negative pressure environment is created within the evaporator through a vacuum system, significantly lowering the boiling point of the liquid (typically between 40℃ and 80℃), thus achieving evaporation of materials at low temperatures and effectively protecting heat-sensitive substances.

2. Vapor Recompression: The secondary steam generated during evaporation is drawn into the steam compressor and mechanically compressed, increasing its pressure, temperature, and enthalpy.

3. Heat Circulation: The heated and pressurized high-temperature steam is introduced into the heating chamber of the evaporator, releasing heat as a heat source and condensing into water, while simultaneously causing continuous evaporation of the material. This process achieves efficient recovery and utilization of the latent heat of the secondary steam.

4. System Operation: Except for a small amount of external energy preheating required during the start-up phase, the system requires almost no replenishment of fresh steam after normal operation, consuming only electrical energy to drive the compressor, forming a highly efficient and energy-saving closed-loop thermodynamic cycle system. II. Structural Composition A low-temperature MVR evaporator is a complex system engineering project, mainly composed of the following core components:

1. Evaporator Body: Depending on the material characteristics, different forms can be selected, such as falling film, forced circulation, or rising film evaporators. Internally, it contains heating tube bundles (or plate heat exchangers) and a separator, and is the core area for material evaporation and vapor-liquid separation.

2. Steam Compressor: The "heart" of the system, responsible for increasing the energy level of the secondary steam. Depending on the operating conditions, a centrifugal compressor (suitable for high flow rates and low compression ratios) or a Roots compressor (suitable for low flow rates and high compression ratios) can be selected.

3. Preheater: Usually a plate or shell-and-tube heat exchanger, it utilizes the high-temperature condensate or waste heat from the steam generated by the system to preheat the feed material, thereby reducing the heat load on the evaporator and improving overall energy efficiency.

4. Separator: Used to achieve efficient gas-liquid separation, typically employing gravity settling, baffle plates, or centrifugal separation to ensure the purity of the steam entering the compressor and prevent liquid droplets from damaging the equipment.

5. Automatic Control System: Composed of a PLC (Programmable Logic Controller) or DCS (Distributed Control System), integrating sensors for temperature, pressure, liquid level, flow rate, etc., to achieve automatic adjustment, safety interlocking, and remote monitoring of the entire process, including feeding, circulation, compression, and discharge.

III. Features Compared to traditional multi-effect evaporators, low-temperature MVR evaporators have the following significant features:

1. High Efficiency and Energy Saving: Utilizing only electrical energy to drive the compressor, no fresh steam is consumed except for startup. Energy consumption per ton of water treated is only 20%-30% of traditional processes, resulting in significant energy savings.

2. Low-Temperature Protection: Operating within a low-temperature range of 40℃-80℃, effectively preventing denaturation and decomposition of heat-sensitive materials (such as pharmaceuticals, food, and biological agents), ensuring product quality and activity.

3. Green and Environmentally Friendly: No waste heat steam is directly discharged, and condensate can be recycled, meeting the environmental requirements of clean production and "zero liquid discharge," reducing environmental pollution.

4. Low Operating Costs: Significantly reduced energy consumption and high automation minimize manual intervention and maintenance costs, resulting in superior long-term economic efficiency.

5. High Automation: Utilizing an intelligent control system, it enables continuous and stable 24-hour unattended operation, and features self-diagnosis and remote maintenance capabilities.

IV. Applications Low-temperature MVR evaporators, with their unique advantages, are widely used in the following fields:

1. Pharmaceutical Industry: Used for the low-temperature concentration of heat-sensitive liquids such as antibiotics, vitamins, amino acids, and traditional Chinese medicine extracts, ensuring that the active ingredients are not destroyed.

2. Food and Beverage Industry: Suitable for the concentration of milk, fruit juice, yeast extracts, and other food products, maximizing the preservation of flavor, color, and nutritional components.

3. Chemical Industry: Used for the concentration and crystallization of chemical intermediates, organic acids, and salt solutions, as well as solvent recovery.

4. Environmental Protection and Water Treatment: A core piece of equipment for treating high-salinity wastewater and achieving "zero liquid discharge," widely used in wastewater treatment in industries such as electroplating, printing and dyeing, pesticides, and coal chemicals.

5. New Energy Industry: Used in the concentration of cathode material precursor solutions during lithium battery manufacturing, and in solution treatment during the recycling of spent lithium batteries.

6. Other Fields: Also applied in various industrial sectors such as seawater desalination, sugar refining, papermaking black liquor treatment, and metallurgical pickling wastewater treatment.