Scrubber

Scrubber systems are used to make coal a "cleaner" fuel.  Scrubbers remove sulfur from a power plant's exhaust.  

 Types 
There are two types of scrubbers: wet scrubbers and dry scrubbers. Wet scrubbers use liquid chemicals to remove pollutants. As polluted air passes through a wet scrubber, chemicals in the scrubber react with the air pollution causing it to precipitate out.  

Dry scrubbers typically use fabric filters. In many cases, both wet and dry scrubbers are used together.Air Pollution Control Engineering, eds. Lawrence K Wang; Norman C Pereira; Yung-Tse Hung (Totowa, NJ: Humana Press, 2004), p. 202 

 Uses 
Modern scrubbers can remove up to 98% of the sulfur and 99% of the precipitate matter from within smokestacks. 

The sulfur and metals that are removed from the scrubbers can be sold.  Sludge from lime scrubbers can be sold to wallboard manufacturers, and fly ash from chimney flues can be sold to make lightweight concrete that can substitute for wood. 

 Effects 
The use of coal in the United States about doubled during the last quarter (25 years) of the 20th century.Harold H. Schobert, Energy and Society: An Introduction, Second Edition (Boca Raton, FL: CRC Press, 2014), p. 267 However, sulfur in the air was reduced by 30% during that same period. This shows that scrubbers work.

 References 

Category:Air pollution