September 2002 - For the concentration of large waste water streams by thermal separation, considerable amounts of energy can be saved and the efficiency of the overall plant can decisively be improved by the specific combination of different technologies.
The plant recently delivered by GEA Wiegand represents the efficient combination of different evaporation principles in 3 plant sections, which form an inseparable overall plant by their interconnection.
Plant section 1
preconcentration of the thin waste water in a falling film evaporator heated by dryer vapour at low temperatures with integrated system for scrubbing the dryer exhaust/air mixture.
Advantages:
- utilization of waste heat, no use of primary energy
- reduction of emissions into atmosphere
Plant section 2
intermediate concentration of the waste water at low product concentrations within the low temperature range with optimum utilization of the energy (heat recovery) by means of mechanical vapour recompression
Advantages
- low specific electrical energy consumption
- simple concept with high operational reliability
- low tendency to incrust
Plant section 3
final concentration of the waste water in a multiple-effect falling film forced circulation evaporator heated by thermal vapour recompressor
Advantages:
- low live steam consumption due to multiple effects heated by vapour recompressor
- high final concentration due to forced circulation evaporation and pretreatment of the waste water
Advantages of the overall plant
- suitable for large waste water streams
- long operating periods, high availability
- low specific energy consumption.