Minnesota Power completes environmental improvement project

Minnesota Power‘s Boswell Energy Center will generate electricity more cleanly and reliably for many years to come with the completion of a major emissions reduction project.

The three-year environmental improvement project at Boswell Unit 4 recently wrapped up in Cohasset and is online and generating power to meet customers’ energy needs. The environmental upgrade is reducing mercury emissions by 90 percent and also reducing emissions of sulfur dioxide 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.

Total cost of the Boswell project is about $260 million. At the peak of construction, local trades and other workers numbered 600 on-site. Minnesota Power integrated the new emissions control equipment with existing systems during a 10-week outage this fall.

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 percent by 2025 a decade early.

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 percent while lowering sulfur, nitrogen oxide and fine particulates by more than 70 percent 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. In November 2015, the Minnesota Pollution Control Agency recognized Minnesota Power for its leadership in reducing mercury 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, sulfur dioxide 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 MATS rule (Mercury and Air Toxics Standards).

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

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