Vacuum evaporator

The sustainable solution for reusing process water

A vacuum evaporator is an efficient technology for industrial water treatment that separates waste water streams into a reusable distillate and a highly concentrated residual stream. This makes water reuse possible and considerably reduces the volume of waste water that needs to be disposed of.

What is a vacuum evaporator?

Why choose evaporation?

Technology & configurations

Applications

FAQ

What is a vacuum evaporator and how does it work?

The operating principle of a vacuum evaporator is based on the difference in boiling point between water and dissolved components. Carrying out the process under vacuum considerably lowers the boiling point of water. This reduces energy consumption and limits the thermal load on the installation.

Evaporation

The waste water is heated, causing the water to evaporate, while dissolved substances and other components remain in the liquid phase.

Condensation

The vapour that forms is cooled and condensed back into water. We call this purified water the distillate.

Concentration

The remaining stream is concentrated further into a concentrate with a greatly reduced volume, typically only 2 to 10% of the original volume.

Why choose a vacuum evaporator?

A vacuum evaporator is a reliable solution for companies that want to cut their water consumption and waste water costs and get the most out of water reuse. In many applications, 90 to 98% of the waste water can be recovered as distillate, leaving only a small concentrate stream.

Operational benefits

High-quality distillate: the distillate produced often has very low conductivity and can be reused as process water in many applications.

Significant volume reduction: because the waste water is heavily concentrated, the amount of residual stream to be disposed of is considerably reduced. This lowers transport and external processing costs.

Autonomous operation: the installation is designed for highly automated operation and needs only limited monitoring.

Compact installation: a vacuum evaporator takes up relatively little space, so it can also be used where space is limited.

Low chemical consumption: compared with many conventional treatment techniques, only small amounts of chemicals are needed.

Sustainability and cost savings

Reusing the purified water in the production process considerably reduces the need for fresh water. At the same time, the amount of waste water to be discharged or disposed of externally is greatly reduced, and in some applications you can even work towards zero liquid discharge.

Integrating heat pumps or mechanical vapour recompression (MVR) means thermal energy is reused as much as possible within the process. As a result, energy consumption stays low relative to the water recovery and volume reduction achieved.

Technology: tailor-made design

No two waste water streams are the same. That is why we select the most suitable configuration based on flow rate, composition, temperature and the required degree of concentration.

Feature	High temperature (MVR)	Low temperature (heat pump)
Operating principle	Mechanical vapour compression	Heat pump
Temperature	Approx. 85 °C	Approx. 35–45 °C
Energy consumption	Low (40–60 Wh/l)	Higher (110–170 Wh/l)
Ideal capacity	Larger flow rates	Smaller flow rates
Corrosion risk	Higher	Minimal

Material selection and heat exchangers

To guarantee the service life of your installation, we choose materials that can withstand your specific process fluid:

316L stainless steel: The standard for general applications.
Super duplex or Sanicro 28:For streams with high concentrations of chlorides, fluorides or sulphates.
Hastelloy: The very best for extreme chemical resistance.

Different types of evaporators

Depending on the composition of the waste water, we also choose the most suitable heat exchanger design.

Forced circulation: a pump drives the waste water through the heat exchanger. The high circulation velocity limits fouling and ensures good heat transfer.
Scraped-surface evaporator: suitable for waste water with a lot of sludge or solids, or a stream that can be heavily concentrated. A mechanical scraper keeps the heat exchange surface clean at all times.
Inner coil: the heat exchanger sits directly inside the evaporator. This simple design is best suited to waste water with a low risk of fouling.
Natural circulation: the liquid circulates without a separate circulation pump. Because of the lower flow velocity, this design is more prone to fouling and may need cleaning more often.

The right choice depends on factors such as the degree of contamination, viscosity, the presence of solids and the risk of scaling.

Single-, double- or triple-effect evaporator

In a double- or triple-effect evaporator, the heat from an earlier evaporation stage is reused to evaporate the water in the next stage. This considerably reduces the amount of external energy needed compared with a single-effect evaporator.

A double-effect evaporator uses around 35% less energy than a comparable single-effect installation. A triple-effect evaporator can reduce energy consumption even further. This gives multiple-effect evaporators a significant energy advantage, particularly at larger flow rates.

Expertise and pretreatment

A high-performance evaporation installation starts with a thorough analysis of the waste water and the process requirements.

Pilot testing
Laboratory or pilot-scale testing to determine the optimal configuration and the achievable distillate quality.
Pretreatment
Integration of techniques such as filtration, pH correction or physico-chemical treatment to optimise the evaporator's performance.

In which applications do we use it?

Vacuum evaporation is used for industrial waste water streams where conventional treatment is not efficient enough or where maximum water reuse is wanted. Depending on the composition of the waste water, the required water quality and the concentration factor needed, we configure the most suitable evaporation solution.

Metalworking and surface treatment

Treatment and concentration of process water, rinse water and waste water from processes such as electroplating and surface treatment, containing dissolved metals, salts and process chemicals.

Waste water treatment and digestate processing

Concentration of hard-to-treat waste water streams and liquid digestate fractions from anaerobic digestion plants, to reduce volume and cut disposal and processing costs.

Water reuse and Zero Liquid Discharge (ZLD)

Maximum recovery of process water with a minimal residual stream, ideal for companies that want to drastically reduce their water consumption and discharge volume.

Raw material recovery and reuse

Concentration of process streams to recover valuable chemicals, salts or other raw materials and reuse them within the production process.

FAQ: frequently asked questions

How much energy does an evaporator consume?

This depends on the type. A high-temperature evaporator with MVR consumes between 40 and 60 Wh per litre of evaporated water. In low-temperature systems, energy consumption can be reduced further by using multiple stages; a two-stage evaporator consumes around 35% less energy than a comparable single-stage version.

Is the installation difficult to maintain?

No, cleaning is fully automatic. With our forced circulation systems, a cleaning cycle is often only needed once every two weeks.

Can I evaporate all types of wastewater?

In principle, yes, but the choice of materials and pre-treatment are crucial. We evaluate each case individually to prevent corrosion or foaming.

Experience the difference with PCA Water.

Would you like to know how much you could save on your water bill and disposal costs? Our experts are ready to calculate a tailor-made solution for you.

Metal reservoirs at a soft drink factory 2024 10 18 05 17 26 utc 1