Concentrating a liquid means boiling off part of its water. The problem is that many industrial products simply can’t withstand normal boiling temperatures without being damaged: proteins denature, sugars caramelize, aromas are lost, and active ingredients degrade. It’s exactly to solve this dilemma that the vacuum evaporator exists — equipment that reduces internal pressure to make the liquid boil at much lower temperatures, preserving the product’s quality.
The principle rests on a simple physical law: boiling temperature depends on pressure. By creating a vacuum, a vacuum evaporator makes water boil well below 100 °C, which opens the door to the industrial concentration evaporation of products that would otherwise be impossible to process.
How a Vacuum Evaporator Works
A vacuum evaporator operates with internal pressure below atmospheric pressure, generated by a vacuum pump or a steam ejector. Under these conditions, the water in the product boils at mild temperatures, often between 40 °C and 70 °C, depending on the vacuum level reached. The vapor generated is continuously removed and condensed, while the product becomes increasingly concentrated inside the equipment.
This operation brings a second, less obvious but highly relevant benefit: since the liquid boils at a lower temperature, the temperature difference between the heating steam and the product can be maintained even with low-energy heat sources. This makes it possible to use residual steam, hot process water, or vapor generated at another stage, increasing the plant’s overall energy efficiency.
Components of a Vacuum Evaporator
- Heat exchanger: where the product receives energy from the heating steam and begins to boil.
- Separator: the chamber that separates the generated vapor from the concentrated product.
- Condenser: turns the vapor back into liquid, allowing the condensate to be recovered.
- Vacuum system: pump or ejector that maintains the reduced pressure inside the equipment.
- Instrumentation: temperature, pressure, and density sensors that ensure process stability.
Why Use Vacuum in Evaporation
Choosing vacuum is rarely a matter of preference: it’s usually mandatory. Heat-sensitive products lose commercial value when overheated, and the damage is irreversible.
Preserving Heat-Sensitive Products
In the vacuum evaporator, the mild temperature protects the characteristics that define the product’s value. In juices, aroma and natural color are preserved; in dairy, protein denaturation and a cooked taste are avoided; in plant extracts and pharmaceutical products, the integrity of active ingredients is maintained. Concentration happens without the thermal stress the product would face in atmospheric-pressure evaporation.
There’s also a gain in fouling resistance. Lower temperatures reduce the tendency for solids to deposit on heat-exchange surfaces, meaning longer production campaigns, fewer stops for cleaning, and better use of installed capacity throughout the year.
Configurations and Types of Vacuum Evaporator
The vacuum concept combines with different construction arrangements, chosen according to the product’s viscosity, sensitivity, and tendency to foul:
| Configuration | Typical Application |
|---|---|
| Falling film | Low- to medium-viscosity products, high thermal efficiency |
| Forced circulation | Viscous products or ones with a strong tendency to foul |
| Multiple effect | Large flow rates, when the goal is steam savings |
| Mechanical vapor recompression (MVR) | Maximum energy efficiency in continuous operation |
| Single-effect vacuum | Smaller flow rates, batch processes, and highly sensitive products |
Vacuum and multiple effect, incidentally, aren’t competitors — they’re complementary technologies. In a multi-stage system, the final effects typically operate under vacuum precisely so the product, already more concentrated and more sensitive, is treated at the mildest temperatures in the line.
Can’t your product handle high temperatures?
Globe Systems sizes vacuum evaporators based on your product’s actual sensitivity and your concentration targets. Talk to our specialists and get a technical assessment.
How Vacuum Is Generated and Controlled
Vacuum can be produced in two main ways. Steam ejectors have no moving parts and are extremely robust: they use high-pressure steam to draw off gases and create the depression, requiring little maintenance but consuming steam continuously. Liquid ring vacuum pumps, on the other hand, consume electrical energy, offer finer control over the vacuum level, and tend to be more efficient when steam costs are high. The choice between the two depends on the plant’s energy mix and the desired vacuum level.
The condenser plays a central role in this arrangement. It’s what removes the generated vapor, turning it into liquid and freeing up space for evaporation to continue. An undersized condenser compromises the entire system’s vacuum, raising the boiling temperature and canceling out the very advantage being sought. That’s why sizing the cooling water and the condenser’s exchange area is just as critical as sizing the evaporator itself.
Design and Operating Precautions
A few points deserve special attention when specifying a vacuum evaporator. System tightness is essential, since any air leak degrades the vacuum and forces the pump to work harder than necessary, raising energy consumption. The product’s residence time in the equipment must also be controlled: even at mild temperatures, staying too long can cause degradation in highly sensitive products.
In continuous operation, monitoring density or total solids at the outlet allows the feed to be adjusted in real time, keeping the final concentration within specification, batch after batch. Combined with well-defined cleaning routines, this control preserves heat-exchange efficiency and ensures the equipment delivers its designed capacity throughout its entire service life.
Industrial Applications
The vacuum evaporator is used in the food industry for concentrating juices, pulps, extracts, and broths; in dairy, for concentrating milk and whey, as in the production of WPC and MPC from whey and milk; in the pharmaceutical and nutraceutical industry; in fine chemicals; and in wastewater treatment, where the lower temperature prevents accelerated corrosion and allows work with aggressive streams.
In food and pharmaceutical applications, the equipment must meet strict hygiene requirements, with sanitary finishing, full drainage, and CIP cleaning, following guidelines from bodies such as ANVISA. These requirements influence the choice of materials, surface finishing, and the system’s piping layout itself.
The Globe Systems Solution
Globe Systems designs the vacuum evaporator on a consultative, process-by-process basis. The vacuum level, exchanger configuration, metallurgy, and number of effects are defined based on the product’s thermal sensitivity, viscosity, fouling tendency, and the plant’s concentration targets. Every project includes an applied safety factor and BNDES accreditation to make the industrial investment viable.
By allowing the liquid to boil at mild temperatures, the vacuum evaporator resolves the dilemma between concentrating and preserving. It’s the technology that makes it possible to concentrate delicate, high-value products without sacrificing color, aroma, nutrients, or active ingredients — delivering energy efficiency and final quality in a single piece of equipment, with a measurable return for the operation.
