Duke Energy SeminarSeptember 3 – 5, 2008Concord, NC

September 4, 2008 2008 WPCA / Duke Energy Seminar

Utility Experiencewith

SCR SO3 Effects

Duke Energy – Belews Creek Steam Station

September 4, 2008 2008 WPCA / Duke Energy Seminar

Introductiono Understanding SO3 & ABSo Determining Tmino Monitoring & Controlling Tmino SCR SO3 Impactso SCR Low-Temp Operationo APH SO3 Impacts

September 4, 2008 2008 WPCA / Duke Energy Seminar

Understanding SO3 & ABS

Sulfur Trioxide (SO3) o > 320ºF Gas Phase SO3o ~ 280ºF to 320ºF H2SO4 Vapor Phaseo < 280ºF H2SO4 Liquid Phase – Acid Dew Point

ABS - Ammonium Bisulfate – (NH4HSO4)o > 625ºF Dissociateso ~ 625ºF to 420ºF Vapor Phaseo < 420ºF Liquid/Sticky Solid Phase –

ABS Dew Point

September 4, 2008 2008 WPCA / Duke Energy Seminar

Determining Tmin - Theoretical

September 4, 2008 2008 WPCA / Duke Energy Seminar

Determining Tmin – Specific

o NH3 Concentration = Inlet NOx Concentrationo Furnace SO2 →SO3 Conversion = 1%o Select Dew Point Temperature from Charto Add +60ºF for Capillary Negative Pressureo Add +10ºF for Temperature Mal-distribution

September 4, 2008 2008 WPCA / Duke Energy Seminar

Monitoring & Controlling Tmin

September 4, 2008 2008 WPCA / Duke Energy Seminar

SCR Low-Temperature Operation

September 4, 2008 2008 WPCA / Duke Energy Seminar

APH SO3/ABS Pluggage

September 4, 2008 2008 WPCA / Duke Energy Seminar

Conclusionso SCR Tmin is Unit Specifico Correct Determination of Tmin is Criticalo Low-Temperature Operation Requires

Recovery @ > ABS Dew Point Tempo No Permanent Deactivation of Catalyst

after Recoveryo Extended Period Low-Temperature

Operation Requires Slower Ramp-up to Avoid Overwhelming SCR and SAH.

o Recovery @ Lower Temperature is Possible with Less or No NH3 Injection