Construction on Boswell Unit 4 air controls due to begin this summer

Minnesota Power, a division of ALLETE (NYSE: ALE), plans to begin construction this summer on new air emissions controls at the coal-fired Boswell Energy Center Unit 4, pending receipt of an approved air permit from Minnesota regulators.

The Minnesota Public Utilities Commission (MPUC) on June 6 approved a project that will reduce mercury emissions by 90% at the company’s largest and newest coal-fired unit. The Boswell 4 retrofit project, first announced in May 2012, will meet requirements in the EPA’s Mercury and Air Toxics Standards (MATS) and the Minnesota Mercury Emission Reduction Act.

The commission approved a motion that the installation of new environmental controls did not require an environmental assessment worksheet. Boswell Unit 4, which is capable of producing 585 MW (net), has been meeting the region’s energy needs since the 1980s. The Boswell Unit 4 project is described as a “multi-pollutant control” project, since it includes installation of a semi-dry flue gas desulfurization (FGD) system, a fabric filter, and a powdered activated carbon injection system.

“We appreciate the Commission’s decision which allows us to progress on this important project without an unjustified and costly delay,” said Margaret Hodnik, VP of Legislative and Regulatory Affairs for Minnesota Power. “A retrofitted Boswell 4 is a critical part of our Energy Forward strategy to balance our resource portfolio and further improve environmental performance while meeting our customers’ expectations for affordable and reliable energy.”

Minnesota Power’s long-term goal under its Energy Forward strategy is a generation mix that is one-third renewable, one-third natural gas and one-third coal-based. The Boswell 4 project, combined with $355m in other emission reduction investments the company has made since 2006, will result in system-wide emission reductions of 70% by 2016.

Boswell 4 was placed into service in 1980. Its boiler is a tangentially-fired steam generator that operates at over 635 MW gross capability and 585 MW net capability available as net output due to 50 MW of existing station service required to operate auxiliary equipment. Several semi-dry FGD system technologies were considered for this project and in October 2012, Minnesota Power awarded the contract to Alstom. Alstom’s CDS technology will also further reduce emissions of acid gases, including HCl and trace metals.

From 1980 to 2011, Minnesota Power burned low-mercury, low-sulfur Montana Powder River Basin (PRB) coal at Boswell. Based on testing done in recent years, Minnesota Power began burning a new blend of coal from Wyoming and Montana at the plant in January 2011.

The Minnesota Pollution Control Agency was taking public comment until March 29 on a draft air permit change that would allow Minnesota Power and unit co-owner WPPI Energy to install new air controls on Boswell Unit 4.

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.