vacuum evaporator

A vacuum evaporator is a core piece of equipment for liquid evaporation and concentration under negative pressure. Its basic principle is to use a vacuum system to reduce the pressure inside the evaporation chamber, causing the solution to boil and vaporize at a temperature below its boiling point under normal pressure, thus separating the solute from the solvent. Because the evaporation temperature is significantly reduced (typically to 40-80℃), this equipment is particularly suitable for processing heat-sensitive materials, effectively avoiding problems such as damage to active ingredients, coking, or deterioration caused by high temperatures.

I. Working Principle and Process

The vacuum evaporator maintains a negative pressure in the system through a vacuum pump or steam injection device. After the material enters the heating chamber, it is heated and evaporated at a lower boiling point. The generated secondary steam enters the separation chamber for vapor-liquid separation. The steam is condensed and discharged through a condenser, while the concentrated liquid is continuously or intermittently discharged through a discharge pump. The system precisely controls the evaporation intensity by adjusting the vacuum degree and heating temperature to achieve stable and continuous operation. Multi-effect evaporators also utilize the secondary steam generated in the previous effect as a heat source for the subsequent effect, significantly improving thermal energy utilization.

II. Main Types and Structures

Evaporators can be classified according to steam utilization method into single-effect, double-effect, triple-effect, and multi-effect evaporators; and according to heating method into natural circulation, forced circulation, falling film, and rising film evaporators. MVR (Mechanical Vapor Recompression) evaporators are a mainstream technology in recent years. They use a compressor to pressurize and heat secondary steam and reuse it as a heat source, achieving energy efficiency of 60%-80%. Core components include a heating chamber (shell or plate type), a separation chamber, a condenser, a vacuum system, a circulation pump, and an automatic control system. Materials are mostly corrosion-resistant 316L stainless steel, titanium, or duplex steel to adapt to different media requirements.

III. Technical Advantages and Features

1. Low Temperature and High Efficiency: Reduces boiling point and energy consumption, protecting heat-sensitive components.

2. Significant Energy Saving: Multi-effect evaporation can save 30%-70% of steam; MVR technology requires almost no live steam.

3. Strong Anti-scaling Properties: Low temperature delays the crystallization of inorganic salts and the formation of organic scale layers.

4. High Processing Capacity: Daily processing capacity can be flexibly configured from several tons to thousands of tons.

5. High Degree of Automation: PLC/DCS system achieves precise control of temperature, pressure, and liquid level.

6. Good Environmental Performance: Can be equipped with a tail gas absorption system to achieve zero emissions.

IV. Typical Application Areas

In industrial wastewater treatment, it is used for zero-discharge treatment of high-salinity wastewater (TDS>5%), electroplating wastewater, and reverse osmosis concentrate, recovering salts through evaporation and crystallization; in the chemical industry, it is used to treat organic acids, dye intermediates, and fine chemicals; in the pharmaceutical industry, it is used to concentrate traditional Chinese medicine extracts and antibiotic fermentation broth; in the food industry, it is used to produce concentrated fruit juice, whey protein, soy sauce, etc.; and it is also widely used in seawater desalination.

V. Key Selection Factors

The viscosity, scaling tendency, foaming properties, and corrosiveness of the material, as well as the processing capacity, feed concentration, target concentration rate, and investment budget, must be comprehensively considered. For high-viscosity, easily scaling materials, forced circulation systems are recommended; for heat-sensitive materials, falling film systems are suitable; and for those seeking ultimate energy efficiency, MVR or multi-effect systems are preferred.

VI. Development Trends

Current technology is evolving towards modular skid-mounted design, AI-optimized control, the application of new corrosion-resistant materials, and the resource utilization of mixed salts. With increasingly stringent environmental requirements, vacuum evaporators have become standard equipment in the fields of high-salinity wastewater and resource recovery, with broad market prospects.