Power facilities are the largest generators of Sulfur Dioxide (SO2), which may cause acid rain. In 2012 Power Plants were required to meet the tougher air quality emission standards. Adding Flue Gas Desulphurization Units (FGD) to clean or scrub the exhaust gases reduces SO2 emissions by 98%. By FGD units reduce the emissions by this amount, they have become the most common type of technology used for reducing sulfur oxide emissions from bituminous and coal fired power plants.
There are two different designs used for FGD systems:
- Dry: This is used to heat up the incoming flue gas to vaporize the liquid in the lime slurry, used to scrub the sulfur dioxides from the gas, resulting in a dry waste stream.
- Wet Scrubber: This uses an excess of slurry and produces a wet waste stream. All internal surfaces as subjected to a saturated environment or are in immersion. This type of system is the most common.
A FGD system and its auxiliary equipment provide a wide range of parameters, which must be evaluated to tailor the proper lining system to the required process conditions. The following is a list of the parameters which should be considered as a minimum: Chemical Exposure, Temperature, Immersion, Impingement and, Sliding Abrasion.
Rubber linings are used where abrasion is a major concern. Typically used in scrubber absorption zones, and slurry piping. There are 3 commonly used rubber linings in the FGD units:
Natural Rubber (60 Shore A Durometer): This has the lowest cost out of the 3 styles. This lining is easy to apply for a qualified applicator and will have the highest degree of abrasion resistance, but is limited in heat / hydrocarbon resistance.
Neoprene (60 Shore A Durometer): This lining is the most costly but will offer a degree of fire and oil resistance, which is the advantage where oil fired start up systems are in place.
Chlorobutyl / Bromobutyl (60 Shore A Durometer): This is the most common lining choice because of the low permeation. The abrasion resistance is not as strong as the NR, but is acceptable and the oil resistance is better than the NR but not as good as the neoprene.
Rubber has advantages so that physical or chemical properties of the scrubbing liquid have any major effects on the service life. Because rubber has good resistance to sulfuric acid, rubber lined steel has been consistently used, especially where abrasion resistance is needed. The key ingredients for a successful FGD lining project are the correct lining specification and the proper rubber lining applicator. With the proper specification and application one can expect to achieve a performance life of 15-20 years with extremely low maintenance costs.
Buck Meadows / Rubber Technologist
Technical Sales Manager