Proper treatment of boiler feedwater is an important part of operating and maintaining a boiler system. As steam is produced, dissolved solids become concentrated and form deposits inside the boiler, leading to poor heat transfer and reduction of boiler efficiency. Dissolved gasses, such as oxygen and carbon dioxide react with metals in the boiler system, resulting in boiler corrosion. These gasses should be controlled or removed to protect the boiler. Several different technologies are widely used in the industry to remove these contaminants. Reverse osmosis membrane and ion exchange systems can remove dissolved solids. Forced draft degasifiers, chemical agents and steam de-aerators have historically been used to remove dissolved gasses. Membrane contactors are increasingly being used to remove dissolved gasses in boiler feedwater. Widely used in the semiconductor, power, pharmaceutical and other industries to control dissolved gasses in water systems, their use in boiler feedwater degasification systems has grown steadily since the development of new industrial grade devices.
Membrane contactors contain microporous hydrophobic membranes, which are used to bring gas and liquids in direct contact without mixing. Contactors operate by lowering the pressure of gas in contact with the liquid to create a driving force to remove the dissolved gasses from the water. They are highly efficient and compact, and can be used inline under pressure.
Chemical treatment is widely used to control dissolved oxygen in a boiler. The cost of operating a chemical treatment program consists of chemical costs and blow down costs. As the water is converted to steam, nonvolatile compounds in the boiler feed water are concentrated inside the boiler. Periodically the water in the boiler must be flushed out to remove these compounds by a process called blow down. Any chemical that is added to the water can increase the frequency of blow down, which affects operating costs of the boiler.