The required amount of the concentrated caustic soda NaOH with 50 %wt, for one regeneration is filled in the measuring tank X074 V10. With the dosing pump X074 P10 or P11 the caustic is controlled feed (with frequency converter) to the static mixer X074 A10 and is inline diluted to the regeneration concentration. The dilution water (condensate & demineralised water) is supplied with the regeneration pumps X074 P01 or P02 and is preheated in the heat exchanger X074 E01 to approx. 40 °C. The dilution water stream is controlled with a flow control valve.