29 March 2007 -- Basin Electric Power Cooperative reportedly plans to spend $25 million next year at its Antelope Valley Station to deal with coal containing more sulfur dioxide than in the past.
Basin's board recently approved construction of an "air jigging" system after a smaller pilot project proved successful. Air jigging is a gravity process that uses an air stream and screens to drop out the heaviest coal that is the most concentrated with sulfur dioxide.
Basin spokesman Daryl Hill said the coal delivered to AVS is changing as its provider, North American's Coteau Freedom Mine, moves into different coal fields. AVS, like other power operators, usually can blend coal deliveries to mix coal to a sulfur dioxide concentration that stays within the limits of their air quality permits.
Hill said blending is becoming more difficult as coal field production shifts, so the company began exploring other ways to reduce the sulfur dioxide.
Basin is still exploring what to do with the heavier coal that drops out of the air jigger, since it will have a higher concentration of sulfur dioxide and trace metals. One possibility is to use it in the Dakota Gasification Co. gasification stream, where coal is liquefied to make synthetic natural gas.