Activated Carbon Injection

Activated carbon injection, often abbreviated ACI, is an air pollution control technology used mainly at coal-fired power plants in which powdered activated carbon is injected into the flue gas stream so that it adsorbs vaporized mercury before the gas reaches the particulate collection equipment of the plant, which then captures the mercury-laden carbon along with the ash. Full-scale trials of the technology for utility mercury control began in North America around 2001 through government and industry-funded programs, and commercial activated carbon injection systems went on sale to power generators starting in 2005. Its use expanded sharply after the United States Environmental Protection Agency finalized the Mercury and Air Toxics Standards on February 16, 2012, which drove roughly 78 gigawatts of coal-fired capacity to install activated carbon injection as their chosen compliance method, and the technology is now considered the most established option for utility-scale mercury control. Reported mercury capture rates vary with the type of carbon and injection rate used, with brominated activated carbon generally achieving higher removal than standard activated carbon at a comparable dose.