Xcel says mercury controls for two Sherco coal units are coming on-line

New air controls to comply with the Minnesota Mercury Emission Reduction Act of 2006 are due to be operating by the end of this month on the coal-fired Units 1 and 2 at the Sherburne County (Sherco) power plant, the Northern States Power subsidiary of Xcel Energy (NYSE: XEL) told the Minnesota Public Utilities Commission in a Dec. 5 update.

There are two coal plants where the 2006 law has an impact.

  • Sherco Unit 3 – Installation of a Sorbent Injection system was completed in 2009. In 2011, Xcel provided the Minnesota Pollution Control Agency (MPCA) with updated information regarding monitoring results and a recommended range to consider when setting the mercury limit to be incorporated into the air emission permit. The MPCA stated that it wished to wait for the U.S. Environmental Protection Agency to issue federal rules regulating mercury emissions and to consider those requirements in establishing the appropriate limits. “Based on the operating history for this control system, we know that it is effective and significantly reduces mercury emissions,” the utility noted. “As pointed out in our October 14, 2011 letter to the MPCA, several issues remained to be resolved as part of the limit setting process, including the difficulties in reliably measuring the small volume of mercury emissions during all operating conditions. We engaged the MPCA in preliminary discussions on setting mercury emission limits for Sherco Unit 3. However, during the extended outage of Unit 3, no such discussions were pursued. On February 16, 2012, the EPA finalized federal standards regulating mercury emissions which require compliance by April 16, 2015. The mercury control system installed on Sherco Unit 3 for compliance with the [2006 state law] will also be used to demonstrate compliance with the federal mercury requirements. We expect these discussions with the MPCA to resume in 2015 to incorporate both state and federal limits into the permit.”
  • King – The sorbent injection system at the King facility has been in service since 2010. The MPCA incorporated mercury-specific permit limitations in the King plant permit issued in 2013. These conditions establish mercury emission limits, pollution control equipment operating parameters and optimization evaluation and monitoring requirements. In August 2013, Xcel submitted its mercury optimization control plan to the MPCA in accordance with permit requirements. The plan addressed monitoring equipment, evaluation of the impact of plant operations on the ability to capture mercury, monitoring of sorbent options, sorbent injection tuning, and continued focus on fuel options at the plant. In 2012, the EPA finalized federal standards regulating mercury emissions which require compliance by April 16, 2015. The mercury control system installed on the King facility for compliance with the [2006 state law] will also be used to demonstrate compliance with the federal mercury requirements.
  • Sherco 1 and 2 – In a 2013 filing, Xcel updated the commission on various mercury reduction technologies. It also reported that it was moving forward with the installation of sorbent injection systems on Sherco Units 1 and 2. “We have been utilizing our knowledge and experience with Sherco Unit 3 mercury controls for the Sherco Units 1 and 2 installations,” Xcel noted. “Because these units are designed differently than Unit 3, however, we expect we will need to fine-tune our mercury sorbent usage. These systems will be installed and operational by December 31, 2014. In 2015, we will gain operating experience that will help us optimize the performance of these systems.”

 

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.