Southern company tests of wood/coal cofiring in pulverized coal units

Abstract

Tests were conducted in June 1992 at Georgia Power Company's plant Hammond Unit 1 to evaluate the impact of cofiring wood waste with pulverized coal on plant performance. Hammond 1 is a 100 MW Babcock and Wilcox (B & W) unit fueled by pulverized coal. Over a three day period, 11 full load performance tests were conducted, five with coal and six with wood/coal mixture. A total of 125 tonnes (140 tons) (as received, 19% moisture) was burned, the wood waste a mixture of sawdust and ground tree trimming waste. Wood percentage in the fuel ranged between 9.7 and 13.5%, with an average for the cofire tests of 11.5% (all percentages by weight). At medium and high O 2 levels, boiler efficiency with wood cofiring was within 0.2-0.4% of boiler efficiency with coal alone. Mill fineness was slightly affected, as the wood particles did not grind as small as the coal particles. Coal particles experienced only a minimal effect due to the presence of the wood. Mill power increased with wood cofiring. Opacity was observed to increase with wood cofiring, the cause of which is presently under investigation. NO x emissions with wood were about the same or slightly less than with coal firing. Sulfur emissions theoretically should have been 6–7% lower with wood cofiring. This decrease was not observed because of fluctuations in the coal sulfur content.