3M Membrane Filtration (formerly Membrana)

Degasification of boiler feed water with Liqui-Cel® membrane contactors


Proper treatment of boiler feed water 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. This leads to poor heat transfer

and reduces the efficiency of the boiler. Dissolved gasses such as oxygen and carbon dioxide will react with the metals in the boiler system and lead to boiler corrosion. In order to protect the boiler from these contaminates, they should be

controlled or removed. There are several different technologies that are widely used in the industry for removing these contaminants. Dissolved solids can be removed with reverse osmosis membrane and ion exchange systems. Dissolved gasses have historically been removed using forced draft degasifiers, chemical agents and steam deareators Recently Membrane Contactors have been utilized to remove the dissolved gasses in boiler feed water. Membrane Contactors are widely used in the semiconductor, power, pharmaceutical and other industries to control dissolved gasses in water systems. Their use in boiler feed water degasification systems has grown steadily since the development of new industrial grade devices. Membrane Contactors are constructed using microporous hydrophobic membranes. The membrane is used to bring a gas and liquid 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, compact and can be used inline under pressure.


Chemical Treatment


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, non-volatile 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. They are flushed out of the boiler in a process called blow down. Any chemical that is added to the water can increase the frequency of blow down. If the blow down frequency is increased or decreased this will impact the operating cost of the boiler.

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