This mechanical compressor is most commonly driven with an electric motor. Utilization of the mechanical compressor substantially reduces steam requirements as well as cooling water demand. To keep the evaporation plant as simple as possible and for easy operation, single-effect centrifugal recompressors are frequently used. This can be highpressure fans or centrifugal-compressors. For high pressure increases, multiplestage compressors can be used. Evaporation plants equipped with mechanical-vapor-recompression-type heat pumps require low energy input during normal operation. Jet compressors can compress only a part of the vapor and the energy of the motive steam is discharged as residual heat via the cooling water. In mechanical vapor recompression systems, however, all vapors are compressed to a higher condensation pressure, as shown in the heat diagram. Some additional steam or condensation may be required to maintain the evaporator heat balance and give stable operating conditions. For lower evaporation rates, positive-displacement-type compressors such as sliding vane rotary compressors, or screw-type compressors can be used as well. This is rather rare, however. The specific energy consumption corresponds to the compressor energy input/evaporation rate ratio. This is determined by the compression ratio, which represents the temperature difference between the heating steam and boiling liquid. Furthermore, it depends on the boiling point elevation and the pressure loss in the system. Under favourable conditions this value can be as low as 4 kwh per 450 kgs. of water. Electric motors can be used to supply the motive power for the compressor. They are reasonable priced and easy to operate and maintain. Combustion engines have been used in cases where there is heat available from the cooling water and exhaust gas. If high-pressure steam is available, it is reasonable to install a steam turbine. Utilizing the turbine exhaust steam may provide very high total energy efficiency. With an MVR evaporator system efficiencies can run as high as 90 kgs. of water evaporated per kwh (roughly the equivalent of 25 kgs. water evaporated per kg of steam with a TVR evaporator). Chem MVR Evaporator Systems can be designed for rates from under 5 m3/hr to over 100 m3/hr. Mechanical vapour compressors contribute to lowering the power consumption during the Evaporation Process. The high quality fans used, are custom designed to suit to the needs of the Evaporation Plant, with the tremendous design experience that Chem has in-house.