ECO-SO2 Background

In the U.S., sulfur dioxide (SO2) emissions are restricted under the Clean Air Act Amendments of 1990. The CAAA established the Acid Rain Program, under Title IV, which requires major reductions of SO2 (and NOx) emissions in two phases.  A nationwide cap-and-trade program was created to promote the most cost-effective compliance.  Fuel switching to lower sulfur fuels and installation of flue gas desulfurization (FGD) systems (also referred to as scrubbers) have been used to comply with the SO2 limits.  As the nationwide SO2 cap is reduced in 2010 as specified in the CAAA, additional SO2 control equipment will be needed for continued compliance.

In March 2005, the U.S. Environmental Protection Agency promulgated the Clean Air Interstate Rule (CAIR).  The CAIR limits SO2 and NOx emissions in the Eastern U.S. In contrast to the Acid Rain Program, which set a nationwide cap on SO2 emissions, the CAIR sets region-wide emission caps for SO2.  Emission reductions are to be achieved in two phases (2010 and 2015).  When fully implemented, the CAIR will reduce SO2 emissions in 28 Eastern states and the District of Columbia by over 70%.  The CAIR applies to fossil fuel burning, electric generating units in the region that are greater than 25 MW.

Calcium-based FGD systems are the most common form of SO2 control equipment deployed on U.S. coal-fired power plants. Modern systems offer 98 percent removal of SO2 and produce synthetic gypsum as a byproduct. With the increasing supply of synthetic gypsum, the opportunity for beneficial reuse of the material is declining at the same time the regulatory requirements and cost for landfilling options are increasing.

Ammonia scrubbing is an alternative to calcium-based systems and produces an ammonium sulfate fertilizer. Ammonia scrubbing is an existing technology that has not seen widespread use in the power generating industry. Powerspan's ECO-SO2 ammonia scrubbing technology incorporates a number of technical changes to the earlier process, improving ammonia scrubbing's performance and cost-effectiveness. As a result, the ECO-SO2 system can be a cost-efficient and reliable SO2 control technology for many applications.