For vapour recompression, two processes are usually applied, namely
- Thermal vapour recompression
- Mechanical vapour recompression
For large evaporation capacities, a mechanical recompression system is
usually applied.
The heat content of the vapours is recovered for heating the chambers
of the evaporators, in that it is brought back by compression (mechanical
vapour recompression) to the condition of the heating steam. Hereby a limited
volume of make-up steam is, however, needed to compensate losses and the
differences in heat content of inflowing and out-flowing solutions.
The evaluation of the energy situation of a mechanical vapour recompression
plant is mainly dependent on the cost of the energy required. The increased
fuel costs influence considerably the economy of a plant and thus favour the
adoption of vapour compressors for evaporation plants of all kinds.