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Duke Energy SeminarSeptember 3 – 5, 2008Concord, NC
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September 4, 2008 2008 WPCA / Duke Energy Seminar
Utility Experiencewith
SCR SO3 Effects
Duke Energy – Belews Creek Steam Station
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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
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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
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September 4, 2008 2008 WPCA / Duke Energy Seminar
Determining Tmin - Theoretical
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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
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September 4, 2008 2008 WPCA / Duke Energy Seminar
Monitoring & Controlling Tmin
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September 4, 2008 2008 WPCA / Duke Energy Seminar
SCR Low-Temperature Operation
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September 4, 2008 2008 WPCA / Duke Energy Seminar
APH SO3/ABS Pluggage
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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
