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Views: 0 Author: Site Editor Publish Time: 2026-10-07 Origin: Site
Plant extracts are widely used in food, nutraceutical, cosmetic and pharmaceutical industries. Raw materials come from diverse sources, resulting in extraction liquids with vastly different physical properties. As a core process in plant extraction, concentration directly determines the yield, color and quality of extracts. Different evaporators adopt distinct heat transfer modes, operating temperatures and energy consumption levels. Improper selection may lead to thermal degradation of materials, foam carry-over, equipment scaling and clogging, as well as excessive operating costs.
MVR evaporators, multi-effect evaporators, rising film evaporators, falling film evaporators and forced circulation evaporators are commonly used for concentration in industrial plant extraction lines. Many clients find it difficult to tell the applicable scenarios of different evaporators during project planning and struggle to select equipment matching their material characteristics. Combined with the typical features of plant extraction liquids — heat sensitivity, foaming tendency, fiber and colloid content — this paper compares the working principles and applicable operating conditions of the five major types of evaporators. It helps enterprises clarify the selection logic of concentration equipment and provides references for process design of plant extraction production lines.
MVR stands for Mechanical Vapor Recompression. It's an energy-saving technology that utilizes the secondary steam and its energy generated by the evaporation system itself. A compressor then warms and pressurizes the secondary steam for reuse, continuously supplying heat to the evaporation system and reducing the need for external energy sources. MVR evaporators can significantly reduce steam usage, making them ideal for scenarios where steam is unavailable or expensive.
Multi-effect evaporation is a system composed of single-effect evaporators. The secondary steam produced by the previous evaporator is introduced into the next evaporator as heating steam. Therefore, boiler steam is only introduced into the first effect, and subsequent evaporations utilize the secondary steam produced by the previous evaporators, thus achieving energy reuse. Each reuse is called one effect. Generally, the effect that utilizes boiler steam is called the first-effect evaporator, and subsequent effects are called the second-effect, third-effect, and so on. Finally, when the secondary steam temperature and pressure are too low to be reused, it is condensed into water using a condenser.
The liquid to be processed is added from the bottom and begins to boil. Bubbles are generated in the liquid, producing secondary steam, which then forms a gas-liquid mixture. The secondary steam, carrying liquid droplets, rotates upwards at extremely high speed in the center of the tube, drawing the unevaporated liquid into a thin film that rises along the tube wall. This is called a rising film evaporator. After evaporation, the liquid and secondary steam enter a separator from the top of the evaporator, achieving separation of the liquid and secondary steam. The concentrated liquid is discharged from the bottom. Rising film evaporators are suitable for industries such as traditional Chinese medicine extraction, winemaking, beverage production, bio-fermentation, and wastewater extraction.
The feed liquid is added from the top of the heating chamber and distributed by the liquid distributor. Under the influence of gravity, vacuum induction, and airflow, it flows downwards in a film. Inside the tube, it is heated and vaporized. The vaporized steam and liquid are drawn out from the lower end of the heating tube and, after gas-liquid separation, yield the concentrated liquid. The secondary steam evaporated from the feed liquid is pressurized and heated by the compressor to increase its enthalpy. It then enters the heating chamber, releases its latent heat, and condenses into condensate. Falling film evaporators are suitable for continuous evaporation and concentration operations in industries such as chemical, oilfield, pharmaceutical, bioengineering, food, glucose, starch, and waste liquid recovery.
A forced circulation evaporator crystallizer is a type of continuous crystallizer with a circulating crystal slurry. During operation, the feed liquid is added through the lower part of the circulation pipe, mixes with the supernatant of the crystal slurry leaving the bottom of the crystallization chamber, and is then sent to the heating chamber by a forced circulation pump. The feed liquid heats up in the heating chamber but does not evaporate, and then enters the separator for flash evaporation. The secondary steam after flash evaporation is drawn into the compressor for pressurization and heating, increasing the enthalpy of the secondary steam, and then enters the heating chamber to condense and release latent heat, thus condensing into condensate. The forced circulation evaporator relies on an external force—the circulation pump—to force the liquid to circulate. Its heating chamber has both horizontal and vertical structures, and the liquid circulation speed is adjusted by the forced circulation pump. Forced circulation evaporators are mainly used in fields requiring crystallization, such as high-concentration inorganic salt wastewater treatment, the metallurgical industry, and environmental protection industries requiring "zero discharge" of wastewater.
Different evaporation capacities and material compositions often necessitate the combination of multiple processes to achieve optimal performance. This integrated approach, combining falling film, rising film (tubular or plate), forced circulation (tubular or plate), scraped evaporator, and crystallization technologies, with material flow directions including co-current, counter-current, parallel flow, or mixed flow, and incorporating multi-effect and MVR technologies, is called a multi-process combined evaporator. Examples include falling film + forced circulation MVR evaporator, MVR evaporation + triple-effect evaporator, MVR + triple-effect + scraped evaporator, MVR + triple-effect + single-effect evaporator, and MVR + triple-effect + single-effect + mother liquor drying evaporator. The multi-process combination requires comprehensive consideration of various factors, including material characteristics, throughput, and the user's existing conditions, to achieve a balance between evaporator performance, operating costs, and investment. Therefore, it demands a high level of technical and engineering experience from evaporator suppliers.
Plant extraction liquids are heat-sensitive, prone to foaming, and contain plant fibers and trace colloids. The selection of evaporators in the concentration stage directly affects extract quality, energy consumption and production stability. MVR, multi-effect, rising film, falling film and forced circulation evaporators are the mainstream concentration equipment for plant extraction production lines: MVR evaporators deliver the lowest energy consumption and are suitable for large-scale continuous production; multi-effect evaporators are mature and stable for medium-to-large projects; falling film evaporators offer high heat transfer efficiency and work well for low-viscosity heat-sensitive feed liquids; rising film evaporators fit medium-viscosity, readily evaporable liquids; forced circulation evaporators resist scaling and show outstanding advantages for high-viscosity, crystal-prone plant extracts with solid suspended matter.
There is no universal evaporator for all practical projects. As a manufacturer of complete plant extraction production lines, we match customers with suitable concentration processes and equipment combinations based on raw material properties, target solid content, production capacity, budget and site conditions. Our solutions balance product quality, operating costs and GMP clean production requirements to build stable and efficient plant extraction and concentration systems.
