Membrane contractors for boilers

Recently membrane contractors have been utilized to remove the dissolved gasses (O₂ and CO₂) in boiler feed water. 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. They have displaced the vacuum tower, forced draft deaerator, and oxygen scavengers around the world for over 10 years.

Source: http://www.liqui-cel.com/documents/WWIOCT03MEMBANA.pdf

Membrane contractors are constructed using micro porous hydrophobic membranes. The membrane is used to bring a gas and liquid in direct contact without mixing. Contractors operate by lowering the pressure of gas in contact with the liquid to create a driving force to remove the dissolved gases from the water.
Contactors are used extensively for deaeration of liquids in the microelectronics, pharmaceutical, power, food & beverage, industrial, photographic, ink and analytical markets.
The running cost of a membrane system includes electricity and seal water for a vacuum pump. A typical membrane system designed to degas the water outlined in this example can reach payback in less than two years.

Chemical treatment is also widely used to control dissolved oxygen in a boiler. Any chemical that is added to the water can increase the frequency of blow down, which affects operating costs of the boiler. In smaller low-pressure boilers (< 4500 lb/h and < 3.45 bars), chemical treatment alone may be used. A combination of steam deaeration and chemicals is most often used for larger high-pressure boilers.

Dissolved oxygen and carbon dioxide control in boiler feed water protects the boiler from corrosion. Membrane contractors can be used to replace or supplement the chemical treatment program, which is often used to control dissolved oxygen. The contractors can minimize the volume of chemicals added to the feed water and offer savings to the end user by reducing chemicals and energy costs.

Find extra information about boiler water treatment and deaeration.
Check also our web page about he main problems occurring in boilers: scaling, foaming and priming, and corrosion.
For a description of the characteristics of the ideal boiler water click here.

References
‘Water treatment handbook’ Vol. 1-2, Degremont, 1991
‘Industrial water conditioning’, BeltsDearborn, 1991
http://www.thermidaire.on.ca/boiler-feed.html