Principle:

The washing liquor from mercerizer is pumped through a self cleaning microfilter to a storage tank.
From the storage tank the liquor is brought by a feed pump into the 3 stage evaporation unit.
After passing through a pre heater the lye enters the first stage of the plant.
With the steam-heated thermic process the water is evaporated out of the re-concentrated liquor and condensate.
The distillate is recovered in a buffer tank for further use.
By using 3 evaporation stages the amount of necessary heating steam is reduced, because the thermal energy which is brought into the system is used 2 more times for evaporating.
The condensation in the last stage is done with cooling water which is heated from approx. 30° C to 85° C.
This hot water is recovered in a buffer tank for further use.
The concentrated caustic soda (about 32° Be) is recovered in a settling tank from where it overflows to a strong lye staple tank.