CONTROL OF SULFUR DIOXIDE AND SULFUR TRIOXIDE USING MAGNESIUM-ENHANCED LIME

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CONTROL OF SULFUR DIOXIDE AND SULFUR TRIOXIDE
USING MAGNESIUM-ENHANCED LIME

• Joseph Potts and Erich Loch
• Cinergy Corporation
• Lewis Benson, Robert Roden and Kevin Smith
• Carmeuse North America

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Overview Of Talk

• Background on control of SO3 with Mg(OH)2 and
  Ca(OH)2
• Magnesium-enhanced lime FGD process with
  byproduct Mg(OH)2
• Results of 800 MW and 1300 MW demonstrations of
  SO3 control with byproduct Mg(OH)2
• Description of 1300 MW byproduct Mg(OH)2 and SO3
  control system
• SO3 control costs byproduct Mg(OH)2 vs.
  commercial Mg(OH)2

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SO3 Emission from Coal-fired Plants

• From oxidation of SO2 in furnace and SCR
• Up to 3 oxidation, 70 ppmv SO3
• Can foul heat transfer surfaces
• Can cause visible plume
• TRI substance

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Background on SO3 control with Mg(OH)2

• Furnace injection of magnesium hydroxide to
  control SO3
• Reacts selectively with SO3 to form water-soluble
  MgSO4, but not with SO2
• Decades of experience in oil-fired units
• Some use in coal-fired units
• Increases melting point of slag

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Magnesium-Enhanced Lime FGD Process Description

• Wet FGD process (Thiosorbic process)
• Uses lime reagent with 3-6 wt. MgO, balance CaO
• Mg increases SO2 removal and allows low L/G
• 21 L/G (3 l/Nm3) for 91 removal with 4 sulfur
  coal
• Low chemical scaling potential
• Liquid in absorber only 10 gypsum-saturated
• Lime is source of Mg for byproduct Mg(OH)2

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800 MW and 1300 MW Demonstrations of Furnace
Injection of Mg(OH)2

• DOE/NETL program by URS co-sponsored by EPRI,
  First Energy, AEP, TVA, and Carmeuse
• Objectives
• 90 SO3 removal
• Reduce plume opacity
• Study balance-of-plant effects on
• Slag accumulation
• SCR catalyst
• ESP
• Fly ash composition

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Mg(OH)2 Injection Locations
Selective Catalytic Reduction
Furnace
Mg(OH)2 Injection Locations
ESP
Wet FGD
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800 MW and 1300 MW Demonstrations of Furnace
Injection of Mg(OH)2

• 800 MW unit
• AH, ESP (100 SCA), magnesium-enhanced lime wet
  FGD
• Baseline SO3 32-39 ppmv at ESP outlet
• 1300 MW unit
• SCR, AH, ESP (400 SCA), magnesium-enhanced lime
  wet FGD
• Baseline SO3 37 ppmv at economizer outlet, 65
  ppmv at SCR outlet

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SO3 Removal in 800 MW Furnace
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SO3 Removal in 1300 MW Furnace
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SO3 Removal Across 1300 MW Furnace and SCR
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800 MW and 1300 MW Demonstrations of Furnace
Injection of Mg(OH)2

• No adverse impact on SCR catalyst or slagging
• ESP impact
• 800 MW adverse when SO3 reduced to 3-4 ppmv
• 1300 MW - no adverse impact
• Opacity monitor readings reduced from 16-20 to
  10-15
• Byproduct and commercial Mg(OH)2 gave similar
  results

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800 MW and 1300 MW Demonstrations of Furnace
Injection of Mg(OH)2

• Visible opacity significantly reduced
• Flyash composition within spec for sulfate

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Hydrated Lime Ca(OH)2 Injection for SO3 Control

• 12 micron avg. particle size, 16 m2/gram
• Demonstrated at 1300 MW for control of SO3
  following SCR
• Injected after air heater
• Demonstrated at 1300 MW (Zimmer station) with
  post-SCR SO3 concentrations
• Injected after ESP
• Captured in FGD absorber and completely utilized

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Magnesium-Enhanced FGD Processwith Byproduct
Mg(OH)2
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Byproduct Mg(OH)2 System at Zimmer
MgSO4 Ca(OH)2 2H2O ? CaSO42H2O (gypsum)
Mg(OH)2
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Magnesium-Enhanced Lime Absorberat Zimmer
Station

• Babcock Wilcox design
• 54 ft (16.5 m) high straight shell
• L/G is 21 gal/1000 acfm (3 l/m3) for 91 SO2
  removal

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Ex-Situ Oxidizer at Zimmer Station
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Byproduct Mg(OH)2 from Magnesium-Enhanced Lime
Wet FGD Process

• Byproduct process developed by Carmeuse
• Piloted in 1995 at Cinergys Zimmer station with
  support of EPRI, Ohio Coal Development Office and
  Cinergy
• Two plants currently producing byproduct Mg(OH)2
• Pre-treats FGD wastewater
• Reduces dissolved solids by 80, metals

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Composition of Byproduct Mg(OH)2
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1300 MW SO3 Control System Design Parameters at
Zimmer Station

• Mg(OH)2 injection system design
• 3 TPH Mg(OH)2
• MgSO3 ratio 8
• 90 removal of furnace-generated SO3
• Ca(OH)2 injection system
• 4 TPH Ca(OH)2
• CaSO3 ratio 7.7
• 90 removal of SO3 post-SCR

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SO3 Control Costs with Mg(OH)2

• Study by Carmeuse of 1300 MW byproduct Mg(OH)2
  system
• 5.4 million capital cost
• OM cost 67/ton Mg(OH)2
• Compares with commercial Mg(OH)2 cost of
  210/ton
• 2.5 million/yr savings
• 2 year payback
• Wastewater pre-treatment at low cost

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Conclusions

• Injection of byproduct Mg(OH)2 demonstrated at
  800 and 1300 MW for 90 capture of
  furnace-generated SO3
• Byproduct Mg(OH)2 system being installed in 1300
  MW plant, start-up 1st quarter 2004
• Byproduct process pre-treats FGD wastewater
• Byproduct Mg(OH)2 cost compares favorably with
  cost of commercial Mg(OH)2
• Hydrated lime controls SO3 formed during SCR