boilerfeedwater

Boiler feedwater is the water supplied to a boiler to produce steam. It must be treated to minimize impurities that can cause scale, corrosion, and carryover, which reduce heat transfer efficiency and shorten equipment life.

Feedwater sources include makeup water and condensate returned from the steam cycle. Condensate is typically hot and contains fewer impurities than makeup water, so reclaiming it reduces makeup requirements and energy use.

Common impurities include dissolved minerals such as calcium and magnesium (hardness), silica, chlorides, sulfates, iron, dissolved oxygen, and carbon dioxide. If left untreated, these substances can form scale, corrode metal surfaces, or promote foaming and carryover into steam.

Treatment strategies vary with boiler type and operating pressure. Thermal and mechanical deaeration remove dissolved oxygen and gases. Chemical treatment may involve oxygen scavengers, pH control using phosphates or caustic, and scale inhibitors. For higher purity, pretreatment followed by demineralization or reverse osmosis may be employed, often with ion-exchange polishing.

Quality control relies on monitoring conductivity, total dissolved solids, silica, alkalinity, and other indicators, with controlled blowdown to limit concentration of impurities. Feedwater heating and condensate return are used to improve efficiency and water use.

Proper management of feedwater quality is essential for efficient, safe boiler operation and to minimize maintenance and downtime.