Brand-new air systems at Big Stone coal plant went commercial on Dec. 29

The Big Stone coal plant air quality control system (AQCS) project was declared commercially operational on Dec. 29, completing six years of effort, plant operator Otter Tail Power told the Minnesota Public Utilities Commission in a Jan. 13 quarterly update.

Testing of the systems and demolition of obsolete facilities will continue, but there is nothing foreseen that will keep the project from coming in at, or under budget, Otter Tail added.

The commission had approved this project on this South Dakota power plant in January 2012.

During this past quarter, activity has centered around the commissioning and testing of all the systems. Only minor problems have been identified, and are being rectified. Reliable operation has been achieved and the systems were declared commercially operational on Dec. 29. Performance tests have been run on the systems and equipment vendors are all meeting their guarantees for environmental performance. There are several operational guarantees that are still being addressed, including long-term reliability/availability, noise levels, and reagent consumption. These will be monitored and assessed, and any problems will be resolved over the coming months.

Also, the demolition of the old baghouse, ID fans, and ash silo has started, and will likely continue into the second quarter of 2016. Other activity this past quarter has centered around closeout of contracts, establishing units of property, and transferring responsibility to plant operations.

The project budget was reviewed in early 2013 and then again in early 2014. Following both reviews the projected project budget was reduced. The original project budget was $491 million, which was reduced in 2013 to $405 million and again in 2014 to $384 million.

The U.S. EPA’s MATS rule as issued requires the Big Stone Plant to reduce mercury emissions, which can be controlled by adding Activated Carbon Injection (ACI) to the project. The estimated cost to add ACI as a standalone project was $5 million. Because of the synergies of installing the system at the same time as the AQCS, the owners installed the ACI system as part of the scope of the AQCS project. The final installed cost of the ACI system was $3.8 million.

The 475-MW Big Stone plant is majority owned by Otter Tail Power, with other shares held by NorthWestern Energy and Montana-Dakota Utilities. The AQCS project includes a scrubber and selective catalytic reduction.

Otter Tail Power, a subsidiary of Otter Tail Corp. (NASDAQ Global Select Market: OTTR), is headquartered in Fergus Falls, Minnesota. It provides electricity and energy services to more than a quarter million people in Minnesota, North Dakota, and South Dakota.

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.