• A A A text size
  • print page

Clean Air Project

PSNH installed "scrubber" technology at Merrimack Station, which significantly reduces sulfur dioxide and mercury emissions.

CAP_LOGO_175Using wet flue gas desulfurization technology—a “scrubber” system—the Clean Air Project captures at least 80 percent of the mercury in the coal and reduces sulfur dioxide emissions by more than 90 percent. The project was completed and placed into operation on 9/28/11, almost 2 years ahead of the July 2013 requirement. The Clean Air Project supplements more than $50 million in previous investments at Merrimack Station to reduce particulate emissions and nitrogen oxides.

Merrimack Station 2011Key Benefits for New Hampshire:

  • Drastic reduction in mercury and sulfur emissions, Merrimack is one of the cleanest coal plants in the nation
  • Continues to support New England’s fuel diversity, enhancing the stability of the power supply in the region.
  • Coal generation powers 45% of the nation and 6% of New England
  • Will serve as a “bridge” over the next 10 to 20 years as we develop and build alternative energy sources on a much larger scale.

Key Benefits for PSNH Customers:

  • PSNH believes that coal will continue to be a competitively priced fuel. Operated as regulated generation, this provides value to customers.
  • Continued operation of Merrimack Station, with the new mercury and sulfur reduction technology installed, will help maintain the diversity of PSNH’s generation portfolio. That diversity helps ensure a reliable supply of energy at a reasonable price.

What is “scrubber technology”?

How_Scrubber_Works-175During a wet scrubber process, limestone is mixed with water to create a slurry, which is “rained down” on the flue gas before it enters the stack. The wet slurry absorbs the SO2 and reacts to form gypsum. After a dewatering process, the solid gypsum is sold to wallboard manufacturers. The mercury is removed in a new state-of-the-art waste water treatment facility.

 Please click here for a larger version of the diagram. 

Clean Air Project Awards:

  • 2013 – Environmental Business Council’s New England Outstanding Environmental-Energy Technology Application Achievement Award
  • 2013 – International Green Apple Awards for Environmental Best Practice 2013
  • 2012 – Power Magazine Top Plants: Six Innovative Coal-Fired Plants

Safety Awards:

  • Old Republic Construction Program, 1 Million Safe MHS
  • URS President's Award, 1.2 Million Safe MHS 3/09-8/12

Merrimack Station Facts:

  • 440 MW Total Output; Unit 1 (110), Unit 2 (330), two combustion turbines (40)
  • Produces 3 million MWh of low-cost power annually—enough energy for approximately 190,000 New Hampshire homes—35% PSNH's total
  • More than $50 million had previously been invested in environmental initiatives since 1989, significantly reducing particulate emissions, nitrogen oxides (NOx), sulfur oxides (SOX) and mercury (Hg)
  • Merrimack Station currently meets all state and federal clean air requirements. Now that the scrubber is operational, the facility will meet the strict requirements of New Hampshire’s mercury reduction law and is among the cleanest coal burning plants nationally.