A promising technology developed by the US Department of Energy’s National Energy Technology Laboratory to capture and remove mercury from coal-fired power plants.has been licensed by Powerspan Corp., a clean energy technology company. The patented process uses UV light to oxidise and remove mercury. Powerspan has initiated a test program to develop the process for commercial application.

In power plant flue gas streams the elemental form of Hg is the more difficult to capture. The photochemical oxidation, or PCO, process uses UV light to produce an excited state mercury species in coal combustion flue gas, leading to the oxidation of elemental mercury. In this form it can be collected in existing air pollution control devices. With this ability to work with conventional pollution control systems, PCO has the potential to serve as a low-cost technology for reducing mercury emissions from power plants.

Preliminary tests of PCO have shown 90 %t oxidation and removal of elemental mercury from simulated flue gas streams. Powerspan is now planning a test program at an actual power plant.

• In a February 1998 report to Congress on toxic air pollutants emitted from electricity generating plants, the U.S. Environmental Protection Agency (EPA) identified mercury emissions from coal-fired power plants as the toxic air pollutant of greatest concern for public health from these sources. In December the EPA proposed a rule to permanently cap and reduce mercury emissions from power plants. It intends to finalise the rule by December 2004.