Thermal vapour recompression

Principle

A part of the vapour steam is compressed to a higher pressure and temperature level by a steam jet pump with steam, so that it can be used as a heating medium.

Process description

The solution is preheated with condensate and enters the evaporation circuit. Here it mixes with the circulated solution and is warmed up in heater H. In the evaporator V, solvent (water) evaporates while cooling the solution to the boiling temperature. The resulting vapour steam is compressed to a higher pressure and temperature level by the steam jet pump with the help of steam, so that it can be used as a heating medium for heating the circulated solution. The excess vapour is condensed. If salt shall be crystallized in the plant, further evaporation concentrates the solution to such an extent that crystals are formed. If desired, the crystals in the suspension can then be separated from the solution and dried.

Characteristics

• Only a fraction of the evaporation energy has to be used in the form of live steam.
• Low investment costs.
• Retrofitting in existing plants is possible.
• Suitable for various applications.

Variants

• Increase in the number of stages to reduce steam consumption.
• With or without salt separation.
• Different preheating concepts.
• Condensation of surplus vapour in mixing- or surface condensers.