URS says full-scale testing of its emissions control technology at a Midwestern power plant has demonstrated greater than 85 percent mercury (Hg) removal and greater than 98 percent sulfur trioxide (SO3) removal, upstream of the plant’s wet scrubber.
The technology uses a single sorbent to simultaneously capture Hg and SO3 from coal combustion gases. URS says the patented process offers a simpler and more effective approach for coal plants’ mercury control and compliance with the Mercury and Air Toxics (MATS) regulation, compared to competing technologies, and costs less.
The new process is based on URS’ SBS Injection sorbent injection technology for control of SO3 emissions from power plants. By reducing SO3 in the flue gas prior to the air heater, the mercury adsorption capacity of unburned carbon, naturally present in fly ash, can be enhanced, the company says. Removal of SO3 prior to the air heater also allows for greater heat recovery and a reduction in flue gas temperature, which further enhances the capture and removal of mercury.
According to URS, SBS Injection is the only sorbent-based technology capable of achieving the SO3 and temperature reductions necessary to achieve high mercury capture.
Sterling Gray, URS business development manager, says the latest test results suggest the new approach could help power plants achieve MATS compliance without using costly mercury controls, such as activated carbon injection or fabric filters.
In December 2011 the EPA issued requirements to control mercury and other toxic air emissions from coal- and oil-fired power plants – what it calls the largest unregulated industrial sources of hazardous air pollution in the US.
Under the much-delayed rules, power plants are equired to install pollution controls within three years. The EPA says the regulations will result in preventing about 90 percent of the mercury in coal burned in power plants being emitted to the air; reducing 88 percent of acid gas emissions from power plants; and reducing 41 percent of sulfur dioxide emissions from power plants beyond the reductions expected from the Cross State Air Pollution Rule.