The caustic Soda (or Potash) , which is produced by membrane electrolysers, has a low concentration (approx 32%). High concentration is got by water evaporation inside a double or triple effect evaporators. Actually, multistage evaporators are able to perform a strong reduction of steam specific consumption. Thermal efficiency is further provided by a complete set of 6 dedicated heat exchangers, working as preheater and intercoolers.

Bluestar in very special cases design also the fourth effect evaporation system.

Selection of proper working conditions and right construction materials are relevant to determine low consumption and long lifetime. Process control is easy and safe, due to a lay out which reduces footprint but which exploits vertical levels to implement robust self-control logic based on the differential head of the equipment.