Wastewater is purified and then reused in a closed cycle. That’s why evaporators are THE sustainable solution for the future!
What does an evaporator do?
In an evaporator the wastewater is evaporated. This vapour is then condensed again. The liquid that is obtained after the condensation is called 'distillate'. The pollution from the wastewater is highly concentrated and discharged as a liquid: 'the concentrate'. The distillate is almost always of a better quality than city water or rainwater. Depending on the wastewater to be treated, in some cases it can even produce demineralised water.
The concentrate flow can usually no longer be further purified and must therefore be discharged externally. In most cases this concentrate stream is 5 to 10% of the treated wastewater. About 90 to 95% of the incoming stream can be reused thanks to the evaporator.
Types of evaporator by materials
For both types of evaporators, you can choose between different materials. Concerning the materials which come into contact with the liquid, 3 types of materials can be used:
- Stainless steel 316L: the cheapest and most commonly used material, but also the most sensitive to pitting corrosion.
- Superduplex: affordable yet high resistance (much more resistant to chlorides and fluorides, which usually cause pitting corrosion).
- Hastelloy: most resistant to corrosion, but on the other hand very expensive.
As mentioned above, a low temperature evaporator is less susceptible to corrosion than a high temperature evaporator. This is simply because the fluorides and chlorides are much more aggressive at a higher temperature.
In special cases it is also possible to work with plastic evaporators. These evaporators are resistant to very corrosive materials. But this has to be evaluated case by case.
Types of evaporators by circulation
In addition to the operating temperature and the material used, we can also subdivide the types of evaporators by way of circulation:
- Forced circulation: the liquid is pumped through the heat exchanger by means of a pump. This technology gives the best heat exchange and requires the lowest cleaning frequency.
- Natural circulation: the liquid only flows past the heat exchanger under natural force. This is much slower than forced circulation (with pump). There is much more charging and a much more frequent cleaning cycle is required.
- With scraper: if the liquid contains a lot of sludge, we recommend the use of a scraper. The heat exchanger is continuously scraped and cleaning is therefore rarely necessary.
PCA works almost exclusively with the forced circulation and scraper models.