These burners do the trick, but increase the amounts of unburned carbon left after combustion. Power plants are left with a mixture of fly ash and unburned carbon. Before low NOx emission requirements came into being, power plants marketed the fly ash remaining after burning to the cement industry. Now power plants must dispose of the fly ash and carbon mixture and disposal is expensive. One use for both combustion waste and anthracite coal is as activated carbon.
Wood is the traditional source for activated carbon, which is sometimes called activated charcoal.
Activated carbon traps impurities found in both gases and liquids in pores within the carbon. These carbon products have a huge market, with 350,000 tons sold each year for water treatment, gas purification, gold extraction and other uses. Products as diverse as air conditioning systems, household water purification pitchers and cigarette filters use activated carbon. However, until recently, uses for the remaining carbon were unknown because no one had characterized the unburned carbon. The researchers used both the unburned carbon and anthracite coal to create activated carbon and compared the results from both.