Evaporators

for effluents

Verdampferanlagen für Abwässer in Grossansicht

Evaporator systems are an important process module for the treatment of industrial wastewaters. Evaporation is one of the thermal methods of wastewater technology. For environmental reasons, it is only used when the substances to be separated are not volatile in steam. The wastewater constituents to be separated are evaporated to form a concentrate which then can be easily passed on to a waste management company. Therefore, disposal costs are low.

In order to transfer the water into a gaseous state, quite a lot of energy has to be applied first. That is why this method requires comparatively more energy than flotation technology or other methods for wastewater treatment. We use this distillation process quite frequently also to meet customer requirements. Due to our longstanding experience with evaporators, we pay special attention to

  • efficient heat transfer
  • low power consumption and
  • low effort required for cleaning


Considering the higher energy demand compared with high-performance flotation, evaporator systems are used when other physical-chemical treatment methods reach their technical and economical limits.

Effect and functioning of an evaporator

The operation principle of an evaporator is simple: the wastewater is heated by supplying energy. As a result, the water evaporates, and the effluent constituents are evaporated to form a concentrate. Depending on the nature of the concentrate, it can be used for thermal recycling or disposal.

Evaporation is of great advantage if the wastewater contains a valuable raw material. This raw material can be isolated by evaporation and reused as a concentrate or secondary raw material.

Therefore, evaporator systems are used particularly

  • for complexed heavy metals, e.g. in the presence of EDTA,
  • for non-volatile AOX,
  • for synthetic emulsions and emulsions that cannot be demulsified,
  • for water-soluble, non-volatile organics.


In these cases, the evaporator system is the preferred choice for successful waste water treatment. Being a plant manufacturer, we select the type of evaporator appropriate for your requirements from all products on the market, such as vapour-compression vacuum evaporators or heat-pump evaporators. The evaporator can be embedded in a customized package including the pretreatment steps necessary for separating solids, oil separation as well as neutralisation.

Which industries use evaporators?

Evaporators can be used in many industries, e.g. in the chemical industry, in metal processing, in plant engineering and in mechanical engineering, whenever process water treatment is involved. It usually is about producing fully demineralised water. When planning such a system, however, you have to take into account that there may be, under certain conditions, more cost-effective processes for producing fully demineralised water. 

What should be considered when using an evaporator? What precautions should be taken?

Evaporation can form highly concentrated substances. So, before using an evaporator, you should consider following questions:

  • Does the wastewater contain organic substances which are volatile in steam and which can pass into the distillate? Such substances can contaminate the distillates by increased hydrocarbon values and COD/DOC values respectively.

  • What is the salt content of the effluent? If salts are present, in particular halides, chlorides, bromides, iodides and fluorides, the appropriate material for the evaporator should be considered beforehand. Salts also limit the concentration maximum.

  • Does the wastewater tend to foam? If an evaporator with vapour compression is used, foam can damage the connected compressor. Therefore, you have to choose appropriate and effective anti-foaming agents for the wastewater to be evaporated while planning the project.

  • Are there any substances in the wastewater that have a flash point in the temperature range of the evaporation process? You have to consider the high surface temperature of the compressor in vacuum evaporators!

     

  • What is the maximum concentration degree of the wastewater? Generally, the concentrate is discharged as a liquid phase from the evaporator. However, as concentration increases, scaling will increase also in the evaporator and in the heat exchangers respectively. A compromise between the maximum concentration factor and an acceptable effort required for cleaning needs to be figured out.

Integration into existing plants – or a turnkey plant

Generally, evaporators can easily be integrated into existing plants. Before integration, however, you have to ensure that the wastewater can be pre-treated by suitable methods and systems, such as neutralisation, sludge trap, separation of free oils or fine filtration.

As an alternative, the evaporator can be supplied together with the required components for pre-treatment as a turnkey plant.

You would like to know more about evaporators?
Just give a call or send us an e-mail:
Telephone:    +49 (0)5152 524410
E-Mail:     contact@oko-tech.de