EPA Technology Available for Licensing: Wet Scrubber Additive for Oxides and Metals Removal
Inventors: Nick D. Hutson, Ravi K. Srivastava, Renata Krzyzynska, Yongxin Zhao
Owned by EPA
Patent Information from the U.S. Patent and Trademark Office website
Federal Technology Transfer Act (FTTA) staff: Contact us if you are interested in learning more about how to license this technology.
This technology is a method for controlling multipollutant emissions from a gas stream of a stationary combustion source. The technology is both a wet scrubber additive and an apparatus for controlling multipollutant emissions.
Background
In 2005, EPA issued the Clean Air Interstate Rule (CAIR) to reduce sulfur dioxide (SO2) and nitrogen oxide (NOx) emissions in the eastern U.S. Both SO2 and NOx contribute to the formation of fine particulate matter (PM), and NOx contributes to the formation of ground-level ozone.
Fine particles and ozone are associated with thousands of premature deaths and illnesses each year. These pollutants also reduce visibility and damage sensitive ecosystems.
Power plants are a major source of SO2 and NOx emissions. A number of power plants use wet flue gas desulfurization (FGD) technologies to control SO2 emissions. In 2005, it was estimated that approximately one-third of U.S. coal-fired utility capacity employed some type of FGD technology.
EPA enacted the Mercury and Air Toxics Standards (MATS) for control of mercury (Hg) and other hazardous air pollutant emissions from coal-fired power plants. Mercury is a toxic air pollutant that poses serious health concerns because it can bioaccumulate in the food chain, primarily in fish. Coal-fired utility boilers are believed to be the largest uncontrolled domestic source of anthropogenic Hg emissions.
New Approach
To date, wet-FGD scrubbers have been designed to specifically remove SO2 from combustion flue gas. Under appropriate conditions, wet-FGD scrubbers can also remove other pollutants such as Hg and NOX. Deeper emission limits, however, will likely require the use of additional control technologies specific to mercury.
Wet-FGD scrubbers have the potential to provide a high level of Hg control because of their substantial gas-liquid mass transfer and the high solubility of most oxidized Hg compounds (such as HgCl2). This control is only effective for flue gas streams containing oxidized forms of Hg, however. The elemental form is not soluble and tends to pass through the wet scrubber.
This EPA technology introduces an oxidizing agent to assist in the oxidation of elemental Hg to form the soluble Hg+2 form. It also partially oxidizes nitric oxide to nitrogen dioxide for removal in the multipollutant scrubber.
