Constellation Energy’s 340-MW Wagner Unit 3 with SCR, tubular air preheater and cold side ESP and 130-MW Unit 2 with Ljungstrom air preheater and cold side ESP participated in Solvay Chemicals testing of Trona and sodium bicarbonate injection for SO2, SO3, NOx and mercury reduction. Industrial Accessories Company (IAC) provided the rigs, injection lances and test management. The required SO2 removal rate was 30 to 50 percent. Both units use activated carbon (PAC) injection for mercury control. The units fire CAPP coal (0.83 percent sulfur) or a blend of CAPP and PRB. Youngen Kong and Stan Carpenter of Solvay Chemicals, Salil Bose and Matthew McMillian of Constellation Energy, and Pramodh Nijhawan of IAC reported at Power-Gen International 2009 that Trona was able to meet the SO2 removal targets for various fuel types at feed rates between 1.1 and 2 NSR. A higher SO2 removal rate was obtained with sodium bicarbonate. ESP performance was enhanced by Trona (with no PAC injection) and NSR 1.1, which reduces SO2 by 29 percent. Around 10 percent NOx was also removed (a bonus) with both sorbents. For Unit 2, mercury removal increased from 82 to 90 percent with Trona injection alone (NSR 1.1). For Unit 3, up to 80 percent of the mercury was removed by PAC without Trona. Over 90 percent mercury removal was realized by PAC with Trona injection (NSR=0.1). The positive effect of sodium bicarbonate on mercury removal was also demonstrated and is comparable to Trona.
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