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News & Trends
NEW TREATMENT FOR FLY ASH
As a coal-combustion product (CCP), fly ash’s main use is to replace Portland cement in the production of concrete. In fact, electric utilities use 35 percent of their fly ash for beneficial applications, according to the Environmental Protection Agency; they landfill the rest. And by avoiding cement production, the use of the cement substitute can reduce carbon dioxide emissions by approximately one ton for each ton of ash.
Fly ash that goes through nitro-gen-oxide converters in the post-combustion process, however, either collects ammonia or retains a good amount of carbon—this lowers the quality of the CCP and can even render it unusable.
Recently, in a project at PPL Generation’s Montour Steam Electric Station in Montour County, PA, researchers tested an ozonation technology designed to overcome those problems. The technology behind the process began as bench-scale work in 2000, when the Department of Energy (DOE) partnered with Brown University and the Electric Power Research Institute to conduct research on alternative ash "beneficiation" processes. The team at Brown discovered that oxidizing carbon surfaces suppresses the adsorption of surfactants used in concrete, the most important carbon-related restriction on fly ash use in concrete production. The ozonation process essentially blends the ash with ozone to render its carbon particles inactive.
Tested at almost full-scale levels of 10 tons per day, the ozonation treatment was successful on various ashes, including low-carbon and activated-carbon-contaminated ashes. According to DOE, ozonation has financial advantages over typical disposal options and is cost-competitive with existing ash beneficiation processes. Moreover, DOE points out that companies can easily retrofit existing coal-fired systems with the technology.
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