Big Stone II and air emission controls:
More energy, fewer emissions
What Big Stone II is doing to reduce air emissions.
To meet our obligation to deliver reliable energy to more than a million customers, and in keeping with our commitment to making environmentally responsible decisions, Big Stone II participants have chosen the most efficient, commercially proven technology available to generate electricity with fewer emissions, while minimizing coal consumption.
Factors considered in selecting technology.
In selecting air emission control technology, participants considered a number of factors, including:
- SO2, NOx, and mercury emission control capabilities
- Reduction in CO2 emissions
- Proven technologies
- Federal and state emission standards
- Opportunities for co-benefit removal of pollutants
- Opportunities for beneficial use of coal combustion byproducts, such as fly ash
- Initial capital cost
- Ongoing operating and maintenance costs
The technologies and their configuration represented in this drawing best meet Big Stone II's objectives. Of course, the final selection of air emission controls and the allowable emission limits are subject to review and approval during the air quality construction permit process.
Advantages of Big Stone II technology selections
- Big Stone II will meet or out perform all federal and state air emission regulations.
- While more than doubling the site’s generation capacity, the existing Big Stone plant combined with Big Stone II will produce sulfur dioxide, nitrogen oxides and mercury emissions that are less than or equal to historical emissions from the existing Big Stone Plant alone.
- The existing Big Stone Plant emits 189 pounds of mercury each year. By committing to a 90% removal goal, which mirrors the 2006 Minnesota Mercury Reduction Act, emissions from the combined plants will be reduced to about 70 to 90 pounds — cutting mercury emissions to less than half.
- Big Stone II’s carbon dioxide emissions will be 20% lower than that of existing regional power plants. Project participants also will offset 100% of Big Stone II’s carbon emissions attributable to Minnesota consumers.
- The fly ash and gypsum that would be collected with the wet scrubber technology are saleable products, and every ton of fly ash used in place of cement in concrete production reduces by one ton the carbon dioxide that otherwise would be emitted.
- Big Stone II is designed to be carbon capture retrofit-ready, with the capacity to incorporate carbon capture technology when it becomes available and cost effective.
- A fabric filter baghouse provides superior particulate emissions control and helps remove mercury.
- Highly advanced wet scrubber technology that will serve both Big Stone units has better sulfur dioxide control capabilities than the dry system typically used to control air quality emissions from sub-bituminous coal-fired units.
- A combination of low nitrogen oxides burners and selective catalytic reduction provides superior control of NOx emissions.
For more information, contact:
Dan Sharp, Manager, Communications . 701-426-3650
Steve Schultz, Manager, External Affairs . 218-770-9111
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