A freshwater demineralisation system can be installed downstream of the water softener which is required in all steam boilers.
Info on Demineralisation
This reduces the surface blowdown rate in particular, which in turn reduces the loss of heat and water from the boiler. It reduces the conductivity of the boiler water which also improves the quality of the steam. A method commonly used is reverse osmosis by means of a membrane module.
Info on Demineralisation – Reverse osmosis