Usibelli tries clean coal technology.

• Author: Richardson, Jeffrey
• Position: Usibelli Caol Mine Inc.

Mixing government seed money with innovative private sector technology, Usibelli Coal Mine Inc. and several partners will test prospects for burning coal more cleanly. Usibelli is supplying the coal and a site at Healy for construction of a new power plant, which will be built and operated by Golden Valley Electric Association to supply power to its growing market in Fairbanks.

The U.S. Department of Energy is putting up $93.2 million and the Alaska Legislature has appropriated $29 million for the project that will be owned by the Alaska Industrial Development and Export Authority.

At the heart of the project is a leading-edge coal combustion unit designed by TRW Combustion Business Unit. Besides burning coal with a lower level of waste emission, the technology provides other cost-saving and conversion advantages. According to Charles Green, a Usibelli marketing specialist, the system reduces maintenance costs and allows retro fitting existing coal- and oil-burning plants with lower capital costs.

Green says the'clean coal'project is a scaled back version of original plans that called for waste heat from the plant to be used to dry Usibelli coal to create a more exportable fuel for sale to the Orient. According to Usibelli consultants, early coal drying tests were not sufficiently conclusive to warrant construction of a plant for that purpose. The experts recommended that the coal-drying element of the project be dropped to strengthen the proposal for federal funding.

What's left, says Green, is 'essentially a demonstration use of new technology to burn coal cleaner than it's been done before.'

Experiments in coal beneficiation the process of upgrading raw coal to increase its quality - will continue, according to Green. In fact, techniques such as mild gasification and conversion of coal to liquids have shown somewhat more promise than drying and will be pursued by Usibelli on a path parallel to the Healy clean coal project.

According to the federal Department of Energy, a number of recent advances in coal-burning technology have focused on combining high combustion efficiency with pollutant removal. A number of these new developments are based on the 'cyclone' combustor concept. The coal is burned in a separate chamber outside the furnace cavity. The hot combustion gases then pass into the boiler where the actual heat exchange takes place.

The advantage of a cyclone combustor is that the ash is kept out of the furnace cavity where it...