April 2002 - The concentration of liquids in evaporation plants requires a
considerable amount of energy. One of the main tasks of designing this type of
plant consists in minimising the energy consumption and in this way optimising
the efficiency. A particular good opportunity to do this is the use of waste
heat from peripheral systems. GEA Wiegand engineers have commissioned an
evaporation plant for wheat starch wastewater at CARGILL, Poland, in
combination with a dryer of the GEA affiliated company Barr-Rosin.
Dewatered fibre and pre-concentrated wastewater are first mixed
together and then fed into a Ring Dryer which is directly heated by gas. The
ring dryer uses exhaust gas recycle to minimise energy input and produce a low
volume, high humidity exhaust.
The dryer exhaust, which has a dew point at
about 83° C, is then used to heat the new waste water evaporator by condensing
the majority of the water vapour from the dryer exhaust. This allows the energy
of the system to be used twice