What is Boiler Feedwater?

In order to prevent issues such as scaling and fouling, water is typically treated before it enters a boiler. This boiler feedwater may be subjected to a variety of different processes including deaeration, filtering, and pre-heating. Caustic elements, such as carbon dioxide and oxygen, can damage the interior components of a boiler or associated pipes and tubing, and sediment in the boiler feedwater can reduce the efficiency of the system or result in sludge buildup. Boiler feedwater may undergo different amounts of conditioning depending on the system, though most applications use one or more methods. The water used in power generation is typically subjected to most of the possible conditioning methods and is also pre-heated before entering the boilers.

A boiler is a sealed vessel that can be used to create hot water or steam that can then be used in a variety of processes. Due to the pressure and heat involved, any impurities or contaminants in the boiler feedwater can create problems in the heated vessel or the apparatus that it sends hot water to. Various issued caused by untreated feedwater can reduce the efficiency of a boiler or even destroy it, along with cooling fins or other pipes and tubings that the hot water or steam passes through.

Lime and other sediments can lead to problems with scale or sludge buildup. The primary issues associated with scale and sludge are related to heat transfer, which can lead to a boiler becoming less efficient. A fouled unit may not heat water sufficiently or can require excessive heat to generate steam. If the scale extends to other parts of the system, they may suffer from decreased efficiency as well. In a boiler heating system, this can manifest in radiators that fail to generate enough heat, and serious buildup may block the circulation within a system entirely.

Another issue that can be caused by not properly conditioning boiler feedwater is corrosion. The primary elements involved in this type of corrosion are carbon dioxide and oxygen, which are typically dissolved in the water from the air. A deaerator may be used to remove much of the oxygen and carbon dioxide in water, though chemical oxygen scrubbers can also be employed. Boiler feedwater typically must be adjusted to a particular level of alkalinity as well, since any oxidation will tend to occur if the pH is lower than nine. If these steps aren't taken, the metal components of the boiler system can corrode and may leak or fail under pressure.