Evaporation

Evaporation is one of the options you have for disposing of spent metal removal fluid. Click to read about the other disposal options.

How does evaporation work?

There are several types of industrial evaporators. The most common types in use in the metalworking industry are simple atmospheric evaporators and single effect vacuum evaporators.

In the atmospheric evaporator all of the evaporation is done in the open environment. The evaporated materials are discharged through an appropriate stack or vent. The release to the environment is by steam vapor to the atmosphere.

In a vacuum assisted evaporator, the boiling point is lowered by pulling a vacuum over the fluid to be evaporated. The evaporated water (distillate) is condensed (condensate) and then discharged to the environment as a liquid.

For evaporation, one storage tank, the evaporator, and an oil sludge storage tank are necessary. Spill containment for a haul-away tank may be required. See previous section.

Evaporators can be significant energy consumers. Therefore, an abundant source of energy is also necessary. Click for more details about the energy needs and costs of evaporation.

What are the advantages and disadvantages of evaporation as a disposal method?

Advantages:

The operational concept is easily understood

Evaporation does not require significant operator attention

This method does not require a wastewater discharge permit (atmospheric evaporator only).

Evaporation is essentially unaffected by dissolved metal content in the wastewater.

The method can handle many liquids with a high BOD₅or COD content, such as synthetic-based fluids.

Disadvantages:

Evaporation can require a significant amount of energy.

An air permit may be required(atmospheric evaporator only).

Foam may be a problem.

Efficiency drops as the solution becomes more concentrated (referred to as boiling point rise).

The method may pose a fire hazard (liquids with a low flash point).

Odors from the vapors can be quite obnoxious.

Vapors and or solutions may be corrosive; exotic metals may be required.

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