The Minnesota Pollution Control Agency (MPCA) is taking comment until Sept. 3 on draft air permit changes for Xcel Energy’s (NYSE: XEL) Black Dog power plant, including changes related to retirement of coal-fired capacity at the site.
The Black Dog plant is located at Burnsville in Dakota County, Minn. The facility is composed of two coal-fired boilers and a natural gas-fired combined cycle gas turbine with duct burner.
“At the time of permit issuance, Xcel Energy has stated their intent to discontinue coal combustion at the facility, prior to the compliance date of the NESHAP for Coal‐ and Oil‐Fired Electric Utility Steam Generating Units,” the agency noted. “The permit does not require this discontinuation; if coal combustion is continued, the coal‐fired boilers will be subject to the NESHAP as of the compliance date listed in the standard, and the Permittee will be required to apply for a permit amendment to incorporate all applicable requirements of the NESHAP.”
Northern States Power d/b/a Xcel Energy has indicated for some time that it plans to shut coal-fired capacity at Black Dog by 2015. But it does have further plans for the plant site itself. The utility has bid a self-build option into its recent request for proposals for new capacity. It has proposed construction of three 215-MW combustion turbine generators with in-service dates between 2017 and 2019. The first unit, for service in 2017, would be at Black Dog. The second and third units would be at a new plant site near Hankinson, N.D., for service in 2018 and 2019.
The utility had at one time planned to convert coal-fired capacity at Black Dog to burning natural gas, but dropped that plan when power demand in the region slumped.
The Xcel website says Black Dog is a coal- and gas-fired station, on the Minnesota River just south of the Twin Cities. The original Unit 1 boiler/turbine and the Unit 2 boiler, were 1950s era coal units and were replaced with a natural gas combined-cycle (Unit 5), which includes a natural gas-fired turbine-generator combined with a heat recovery steam generator. Exhaust heat from Unit 5 powers the Unit 2 steam turbine. The repowering project, completed in summer 2002, boosts output from the two original units by more than 100 MW and results in cleaner power production. Units 3 and 4 are dual-fuel boilers with steam turbines that continue to use coal as the primary fuel. Natural gas is the backup or topping fuel used to obtain maximum generation for both units. Unit 3 has 108 MW of capacity and Unit 4 has 170 MW, the website shows.