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Evaporators in the Food Industry: Types, Working, and Maintenance Tips

By PMG Engineering · 7 May 2022

Insight on Evaporators Used in Food Industry

Evaporators play a crucial role in the food processing industry, especially in the production of concentrated food products like jam, condensed milk, whey, and cheese powders. These devices are widely adopted by food manufacturing consultants and food technology experts to improve processing efficiency and product shelf life. This article provides insights into the working principle, types, and maintenance of evaporators in the food industry.

Why Evaporation is Essential in Food Processing

In food production, raw materials typically contain excess water that must be removed to achieve the desired product consistency and shelf stability. Evaporation technology is used to:

Concentrate food products
Reduce bulk weight and volume
Lower transportation and storage costs
Improve microbiological and chemical stability
Enable downstream processes like spray drying or freeze-drying

Working Principle

Evaporation involves simultaneous heat and mass transfer, where a liquid food product is heated to remove water as vapor. The process results in a concentrated liquid that is still pumpable. Key influencing factors include:

Temperature and pressure conditions
Heat propagation rate
Surface area and vacuum control

Reason for Installation of Evaporators

There are several reasons for concentrating food liquids:

To reduces costs for storage and transportation.
To induce crystallization.
It may be used as an economical preparatory step for subsequent dehydration as in the cases of spray drying, vacuum drying, freeze-dried, crystallization and mixing.
To reduce water activity to increase microbiological and chemical stability.
Recover valuable substances and by-products from waste streams.

Components of Evaporator System

Heat Source: Generally steam-based heat exchangers

Evaporation Vessel: Where water is evaporated

Vapour Separator: Separates concentrated product from vapors

Vacuum System: Enhances efficiency by reducing the boiling point

Evaporators may operate singly, or several may operate in series. Each one is referred to as an effect and in multiple-effect systems, the product output from one effect is the feed for the following effect. Similarly, higher-temperature vapour driven out of the product in one effect is used to heat a lower-temperature product in another. Efficiency is gained by using multiple-effect systems.

Types of Evaporators Used

1. Vertical Tube or Calandra Evaporators

Steam circulates vertically through tubes at the bottom of the evaporator
Product recirculates for efficient concentration

2. Horizontal Tube Evaporators

Suitable for low vertical space layouts
Requires flooded operation for full tube coverage

3. Plate Evaporators

Compact and modular design
Allows for easy capacity adjustments

4. Forced Circulation Evaporators

Ideal for viscous products
Requires pumps for circulation efficiency

5. Falling Film Evaporators

Used extensively in dairy plants
Ensures gentle, controlled evaporation for heat-sensitive materials

Maintenance Tips to Improve Energy Efficiency

To keep evaporators running optimally and reduce energy consumption:

Prevent air leaks to maintain vacuum pressure
Clean heat transfer surfaces regularly
Inspect and replace damaged insulation
Clean vapour separation vessels frequently
Avoid water leaks that dilute products

Conclusion

Evaporators are indispensable components in the food processing and manufacturing industry, enabling the efficient concentration of food products while preserving quality and reducing operational costs. From dairy powders to fruit concentrates, their applications span across a wide range of ready-to-eat and shelf-stable products. By selecting the right type of evaporator and maintaining it effectively, food consultants, food processing consultants, and engineering experts can significantly enhance process efficiency, product quality, and energy savings. For any new or expanding food factory design, integrating a well-optimized evaporation system is a key step toward building a world-class food manufacturing facility.

References

Frequently asked

Which evaporator type is best for heat-sensitive dairy products?

Falling film evaporators are used extensively in dairy plants because they ensure gentle, controlled evaporation for heat-sensitive materials. For viscous products, forced circulation evaporators are more appropriate, though they require pumps to maintain circulation efficiency. Plate evaporators suit compact, modular installations where capacity may need adjusting, while horizontal tube evaporators fit layouts with limited vertical space but need flooded operation for full tube coverage.

Why should we install an evaporator instead of drying the product directly?

Concentrating food liquids by evaporation reduces storage and transportation costs, induces crystallization, and lowers water activity to increase microbiological and chemical stability. It is also an economical preparatory step before subsequent dehydration such as spray drying, vacuum drying, freeze-drying, crystallization and mixing, and it allows recovery of valuable substances and by-products from waste streams.

How does a multiple-effect evaporator improve energy efficiency?

Evaporators may operate singly or several in series, each unit being called an effect. In multiple-effect systems, the product output from one effect becomes the feed for the following effect, and higher-temperature vapour driven out of the product in one effect is used to heat a lower-temperature product in another effect. This reuse of vapour is where the efficiency gain comes from.

What are the main components we need to allow for in an evaporation system?

An evaporator system comprises a heat source, generally steam-based heat exchangers; an evaporation vessel where water is evaporated; a vapour separator that separates the concentrated product from the vapours; and a vacuum system that enhances efficiency by reducing the boiling point. Layout must also allow for single-effect or multiple-effect arrangements depending on the duty.

What maintenance keeps evaporator energy consumption down?

To keep evaporators running optimally, prevent air leaks so vacuum pressure is maintained, clean heat transfer surfaces regularly, inspect and replace damaged insulation, clean vapour separation vessels frequently, and avoid water leaks that dilute the product. Neglecting any of these raises energy consumption and can compromise the concentration achieved.

Which food products typically require an evaporation step?

Evaporators are central to producing concentrated food products such as jam, condensed milk, whey and cheese powders, and their applications extend across dairy powders, fruit concentrates and a wide range of ready-to-eat and shelf-stable products. Evaporation removes excess water from raw materials to achieve the desired product consistency and shelf stability while leaving a still-pumpable concentrate.

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PMG Engineering. (2022). Evaporators in the Food Industry: Types, Working, and Maintenance Tips. PMG Engineering. https://pmg.engineering/Article/133/evaporators-in-the-food-industry-types-working-and-maintenance-tips/

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