Minnesota Power marks completion of Boswell 4 coal unit retrofit

Minnesota Power on Dec. 17 marked the completion of a major emissions retrofit project on a unit at its coal-fired Boswell Energy Center.

The three-year environmental improvement project at Boswell Unit 4 recently wrapped up and the unit is back online and generating power to meet customers’ energy needs. The environmental upgrade is reducing mercury emissions by 90% and also significantly reducing emissions of SO2 and particulates, meeting all state and federal regulations.

Unit 4, capable of producing 585 MW, is Minnesota Power’s largest coal-fired generating unit. Minnesota Power is an operating division of ALLETE Inc. (NYSE: ALE). Total cost of the Boswell project is about $260 million. Minnesota Power integrated the new emissions control equipment with existing systems during a 10-week outage this fall.

“The new state-of-the-art technology at Boswell 4 will make the generating unit among the cleanest and most efficient in the nation while helping to preserve the reliable and affordable power our customers expect,” said Al Hodnik, ALLETE chairman, president and CEO. “The project is the latest achievement in our initiative to further lower emissions that began in 2006, and it demonstrates Minnesota Power’s commitment to a balanced energy future through its EnergyForward strategy to help transform the nation’s energy landscape.”

EnergyForward is the company’s resource strategy to diversify its power supply to a balanced energy mix of one-third coal, one-third renewable energy and one-third natural gas. Minnesota Power’s renewable energy portfolio has already enabled the company to meet the state of Minnesota’s renewable energy standard of 25% by 2025 a decade early.

“Baseload coal generation remains an important energy supply component supporting Minnesota Power’s mission to deliver safe, reliable and affordable electricity to its customers, even as we add more renewable energy and natural gas and achieve energy savings through conservation,” said Minnesota Power Chief Operating Officer Brad Oachs. “With the retrofit finished, ahead of schedule and under budget, Boswell 4 is cost-effectively serving customers, including the mines, paper mills and other large industrial customers, with cleaner power. It’s ready to perform at the highest level.”

In the past decade, Minnesota Power has invested more than $600 million to cut emissions across its system. The utility has reduced mercury emissions by 90% while lowering sulfur, NOx and fine particulates by more than 70% compared with 2005 levels.

That investment also included the installation of a high efficiency steam turbine at Boswell 4 resulting in 60 MW of increased power capacity with no additional emissions.

The Boswell 4 environmental upgrade involved replacing the existing wet scrubber and particulate control technology with a semi-dry system that uses less water, installing a powdered activated carbon injection system to capture flue gas mercury, and adding a fabric filter to further control particulates. A new 25,000-square-foot building houses a nine-module Alstom NID system that removes mercury, SO2 and particulates. Ash management entails the transport and storage of ash in a state-approved ash cell that complies with applicable rules. The project meets the requirements of Minnesota’s Mercury Emissions Reduction Act and the federal Mercury and Air Toxics Standards.

Minnesota Power provides electric service within a 26,000-square-mile area in northeastern Minnesota, covering 144,000 customers, 16 municipalities and some of the largest industrial customers in the United States.

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.