Articles

Reprinted with permission from Mining Engineering, December 2002 issue

New Clean Coal Technology Fires Country's Cleanest Power Plant

A new clean coal technology has been developed that eliminates more than 99.99% of the particulate matter that is released when coal is burned. The Advanced Hybrid filter system is in operation at the Big Stone coal-fired plant in South Dakota.

The technology was developed by the Energy and Environmental Research Center (EERC) at the University of North Dakota in cooperation with the U.S. Department of Energy (DOE) and W.L. Gore Associates as well as the power plant’s owners. They are Otter Trail Power, NorthWestern Energy and Montana-Dakota Utilities. The DOE contributed $6.5 million to the research. The plant’s owners funded the remainder of the $13.4 million cost.

The Advance Hybrid Filter system combines two current fly ash-capturing technologies — fabric fil tration and electrostatic precipitation. EERC said the technology reduces particulate emissions so effectively that the air coming out of the plant is cleaner than the air en- tering the plant, with respect to fine particulate.

The Advanced Hybrid Filter technology captures practically all of the particulate matter from coal plant emissions

Electrostatic precipitators use electrodes to give particles an electric charge that draws them to collection plates. The Advance Hybrid technology places rows of filter bags between the collection plates. The bags stop the particles that get by the collectors. Periodically, air is in jected in reverse through the filters. This dislodges built-up particles and sends them back toward the plates where they are collected. The air injection also keeps the bags clean, thus requiring less energy to draw the air through.

Consider a plant that generates 45 kg (100 lbs) of particulate matter over a certain period of time and has a collector with an efficiency rating of 99%. The plant will emit 2.2 kg (1 lb) of particles during that period. The Advanced Hybrid Filter system allows only 0.004 kg (0.01 lb) of particulates to escape.

For more information, contact Gerald Groenewold, EERC director, 15 N. 23rd St., Grand Forks, ND 58202-9018, phone 701-777-5131, fax 701-777-5181, e-mail ggroenewold@undeerc.org, Web site http://www.undeerc.org