By Yougen Kong, PhD, SOLVAir Products, Solvay Chemicals, Inc.
“Dry Sorbent Injection of Trona and Sodium Bicarbonate for SO2, SO3, NOx and Mercury Mitigation” was presented at Power-Gen 2009 in Las Vegas, Nevada in December. In this case study, two boilers (Unit 2-140 MW and Unit 3 - 350 MW) at Constellation Energy’s Wagner site burnt low sulfur coal. Trona was injected at the inlet of the air preheater, and the test results showed that the targeted 30% and 50% removal rates for SO2 for both units were successfully met with reasonable trona federates. Around 10% additional NOx were also removed.
While results showed that trona could meet established removal rates, when a higher SO2 removal rate was needed, it was clear that sodium bicarbonate would be the product of choice.
For Unit 2, around 90% of mercury was removed with trona injection alone. For Unit 3, only up to 80% of mercury was removed by PAC without trona. Over 90% Hg removal was realized by PAC with trona injection. The positive effect of sodium bicarbonate on Hg removal was also demonstrated and comparable to trona.