vapor recompression evaporator

I. Working Principle of Vapor Recompression Evaporation

The core of the MVR system lies in the energy cycle of "compression-heating-reuse". Traditional evaporators directly condense and discharge the generated secondary steam, resulting in a significant waste of heat energy. MVR, however, uses a mechanical compressor to compress the secondary steam to a higher pressure. According to thermodynamic principles, the saturation temperature of steam increases with pressure. The temperature of the compressed steam can be increased by 8-20°C, and it returns to the shell side of the evaporator as a heat source, exchanging heat with the liquid in the tube side, releasing latent heat, and condensing into water. The entire process requires only a small amount of external steam or electricity to drive the compressor to maintain continuous system operation.

II. System Composition

A typical MVR system mainly consists of a preheater, evaporator, compressor, vacuum system, and control system. The compressor is the "heart" of the system, and types include Roots, centrifugal, and screw evaporators. Selection requires comprehensive consideration of temperature rise requirements, throughput, and feed liquid characteristics. Evaporators often employ a falling film structure, where the feed liquid is evenly distributed along the inner wall of the heat exchange tubes in a film form from the top, offering advantages such as high heat transfer efficiency, short residence time, and reduced scaling.

III. Advantages of Vapor Recompression Technology

A significant characteristic of MVR is its extremely low energy consumption. The electricity consumption for evaporating one ton of water is only 15-50 kWh, equivalent to one-quarter to one-third of the energy consumption of a traditional triple-effect evaporator. Since no cooling circulating water system is required, water conservation is significant. The equipment has a compact structure, reducing the footprint by more than 50% compared to multi-effect evaporators. The low operating temperature makes it particularly suitable for processing heat-sensitive materials, effectively preserving active ingredients. Fully automated control ensures stable operation, small evaporation temperature differences, and reduced equipment corrosion and scaling tendencies.

IV. Application Areas of Steam Recompression Evaporators

This technology excels in seawater desalination and zero-discharge wastewater treatment, capable of handling high-salinity wastewater such as desulfurization wastewater and concentrated brine from coal chemical processes. In the bio-fermentation industry, it is used for the concentration and purification of amino acids, vitamins, and antibiotics. In the food industry, it maximizes the retention of flavor compounds in the concentration of fruit juices, dairy products, and sugar solutions. In the pharmaceutical industry, MVR is used for the pre-crystallization concentration of active pharmaceutical ingredients and the concentration of traditional Chinese medicine extracts. Furthermore, it is gradually replacing older evaporation equipment in traditional industries such as salt production, papermaking, and printing and dyeing.

V. Technology Comparison

Compared to multi-effect evaporation, MVR has a higher initial investment but lower operating costs, with a payback period typically of 1-2 years. Compared to thermal steam recompression , MVR uses mechanical compression, resulting in higher efficiency and is unaffected by fluctuations in plant steam pressure. Compared to heat pump technology, MVR has a higher compression ratio and stronger temperature rise capability, making it suitable for larger-scale industrial production.

VI. Development Trends of Vapor Recompression Evaporators

Currently, MVR technology is evolving towards intelligentization, achieving better compression ratio control through AI algorithms and reducing failure rates through predictive maintenance. The application of new materials improves the equipment's corrosion resistance and heat transfer efficiency. Coupled with membrane separation and crystallization technologies, it forms a more efficient salt resource recovery process. Under the "dual carbon" target, MVR, as a key technology for energy conservation and emission reduction, has broad market prospects and is continuously developing towards larger scale, higher energy efficiency, and wider material adaptability.