Boswell Unit 4 down for ten weeks to tie in new air emissions controls

The coal-fired Boswell Energy Center Unit 4 is down right now for tie-in of new air emissions controls, with the final check-out of those controls to be wrapped up in early 2016.

Minnesota Power on Sept. 30 petitioned the Minnesota Public Utilities Commission for approval of its 2016 Boswell Unit 4 Emission Reduction Factor. This involves cost recovery of investments, expenditures and costs related to the Boswell Energy Center Unit 4 mercury emission reduction project through Minnesota Power’s Rider for Boswell Unit 4 Emission Reduction.

The BEC4 Plan is a multi-pollutant solution for reducing mercury, particulate matter (PM), sulfur dioxide (SO2), and other hazardous air pollutants being addressed by U.S. Environmental Protection Agency regulations while also reducing plant wastewater. Minnesota Power is installing a semi-dry flue gas desulfurization system, fabric filter and powder activated carbon (PAC) injection system to help achieve compliance with the Minnesota Mercury Emissions Reduction Act (MERA), EPA’s Mercury and Air Toxics Standards (MATS), and other enacted or pending federal and state environmental rulemakings regulating air and water emissions and solid byproducts from coal-fired power plants.

Minnesota Power is installing Alstom’s circulating dry scrubber (CDS) technology, referred to as the NID system, for the removal of PM, SO2, acid gases including hydrochloric acid and trace metals, and other hazardous air pollutants being addressed by EPA regulations, while also reducing plant wastewater. In addition to the NID system, Minnesota Power is installing a PAC system to capture flue gas mercury, in combination with the fabric filter integral to the NID to control PM.

The utility said in the Sept. 30 application: “Construction activities have been proceeding well. Erection of the NID building, as well as all internal components, is nearly complete. Construction has moved into system turnover for start-up status and Unit 4 is currently off line for the tie in of the duct work. … Overall, construction is approximately 90 percent complete, engineering is more than 98 percent complete and the project stands at more than 90 percent complete.”

Work continues on the electrical and control components which can only be completed while the 585-MW Unit 4 is off line during the ten-week scheduled outage that started on Aug. 15. The outage period is when all tie in occurs as well as checkout and commissioning for tuning of the new equipment. Outage activities include:

  • Air heater outlet duct demo and tie in to new NID inlet duct
  • ID fan inlet duct demo and tie in to NID outlet duct
  • ID fan motor removal and installation of new motors
  • Removal of old variable frequency drive (VFD) equipment and installation of new VFD and transformers
  • Start up and check out of all systems
  • Stack choke removal
  • Completion of insulation and lagging of duct work
  • Completion of electrical system tie in 

The BEC4 Project total anticipated project cost has not changed since Minnesota Power submitted its 2015 BEC4 Factor and Compliance Filing in November 2014, remaining at an estimate of approximately $260 million from an originally estimated approximately $350 million. The total project cost reflects Minnesota Power’s 80% ownership interest in the equipment and facilities that comprise the BEC4 Project. WPPI Energy owns the other 20% of the unit.

U.S. Energy Information Administration data shows that coal suppliers to the Boswell plant earlier this year were mines in the Powder River Basin, including Arch Coal‘s Black Thunder mine in Wyoming, Peabody Energy‘s North Antelope Rochelle mine in Wyoming and Cloud Peak Energy‘s Antelope mine in Wyoming and Spring Creek mine in Montana.

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.