Transcript Document

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
Overview Of Talk
• Background on control of SO3 with Mg(OH)2 and
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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
Control of SO2 and SO3 Using Magnesium-enhanced Lime
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
Control of SO2 and SO3 Using Magnesium-enhanced Lime
Background on SO3 control with
Mg(OH)2
• Furnace injection of magnesium hydroxide
to control SO3
 Reacts selectively with SO3 to form watersoluble MgSO4, but not with SO2
 Decades of experience in oil-fired units
 Some use in coal-fired units
 Increases melting point of slag
Control of SO2 and SO3 Using Magnesium-enhanced Lime
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
Control of SO2 and SO3 Using Magnesium-enhanced Lime
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:
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Slag accumulation
SCR catalyst
ESP
Fly ash composition
Control of SO2 and SO3 Using Magnesium-enhanced Lime
Mg(OH)2 Injection Locations
Furnace
Mg(OH)2
Injection
Locations
Selective
Catalytic
Reduction
ESP
Wet
FGD
Control of SO2 and SO3 Using Magnesium-enhanced Lime
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
Control of SO2 and SO3 Using Magnesium-enhanced Lime
SO3 Removal in 800 MW Furnace
SO3 Removal at ESP Outlet
100%
90%
80%
70%
60%
50%
40%
Long-term test
30%
Short-term test
20%
10%
0%
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Mg:SO3 Ratio (baseline on ESP outlet SO3)
Control of SO2 and SO3 Using Magnesium-enhanced Lime
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SO3 Removal in 1300 MW Furnace
100%
90%
SO3 Removal
80%
70%
60%
50%
40%
30%
20%
10%
0%
0
1
2
3
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5
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Mg:SO3 Molar Ratio based on economizer outlet SO3 concentration
Control of SO2 and SO3 Using Magnesium-enhanced Lime
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SO3 Removal Across 1300 MW
Furnace and SCR
SO3 Removal at ESP Outlet
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
0
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Mg:SO3 Molar Ratio (based on baseline SCR outlet SO3)
Control of SO2 and SO3 Using Magnesium-enhanced Lime
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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 1015%
• Byproduct and commercial Mg(OH)2 gave
similar results
Control of SO2 and SO3 Using Magnesium-enhanced Lime
800 MW and 1300 MW Demonstrations
of Furnace Injection of Mg(OH)2
• Visible opacity significantly reduced
• Flyash composition within spec for sulfate
Control of SO2 and SO3 Using Magnesium-enhanced Lime
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
Control of SO2 and SO3 Using Magnesium-enhanced Lime
Control of SO2 and SO3 Using Magnesium-enhanced Lime
Magnesium-Enhanced FGD Process
with Byproduct Mg(OH)2
Cleaned Gas
Magnesium
Enhanced
Absorber
Lime
Water
Flue
Gas
Slaker
Lime
Slurry
Tank
Oxidizer
Belt Filter
Inerts
Compressed
Air
Gypsum
Byproduct
Pre-Treated
FGD Effluent
Byproduct
Magnesium
Hydroxide Precipitation
Tank
System
pH 9.5 - 10
Gypsum
to Oxidizer
Magnesium
Hydroxide
Control of SO2 and SO3 Using Magnesium-enhanced Lime
Byproduct Mg(OH)2 System at Zimmer
Lime
4 TPH
Ca(OH)2
FGD Effluent
631 gpm
Pre-Treated
FGD Effluent
to Ponds
550 gpm
M
Precipitation
Tank
pH 9.5 - 10.5
Gypsum
to Oxidizer
7 TPH
Magnesium
Hydroxide Slurry
to SO3 Control
3 TPH Mg(OH)2
MgSO4 + Ca(OH)2 + 2H2O →
CaSO4•2H2O (gypsum) + Mg(OH)2
Control of SO2 and SO3 Using Magnesium-enhanced Lime
MagnesiumEnhanced Lime
Absorber
at 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
Control of SO2 and SO3 Using Magnesium-enhanced Lime
Ex-Situ Oxidizer at Zimmer Station
Control of SO2 and SO3 Using Magnesium-enhanced Lime
Byproduct Mg(OH)2 from MagnesiumEnhanced Lime Wet FGD Process
• Byproduct process developed by Carmeuse
• Piloted in 1995 at Cinergy’s 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
Control of SO2 and SO3 Using Magnesium-enhanced Lime
Composition of Byproduct Mg(OH)2
Mg(OH)2, wt. %
Gypsum, wt. %
Inerts, wt. %
Total Suspended
Solids in slurry, %
BET Specific
Surface Area, m2/g
Median Particle
Size, microns
73
21
6
20
55
3
2 m ic ro ns
Control of SO2 and SO3 Using Magnesium-enhanced Lime
1300 MW SO3 Control System Design
Parameters at Zimmer Station
• Mg(OH)2 injection system design
 3 TPH Mg(OH)2
 Mg:SO3 ratio = 8
 90% removal of furnace-generated SO3
• Ca(OH)2 injection system
 4 TPH Ca(OH)2
 Ca:SO3 ratio 7.7
 90% removal of SO3 post-SCR
Control of SO2 and SO3 Using Magnesium-enhanced Lime
SO3 Control Costs with Mg(OH)2
• Study by Carmeuse of 1300 MW byproduct
Mg(OH)2 system
 $5.4 million capital cost
 O&M 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
Control of SO2 and SO3 Using Magnesium-enhanced Lime
Conclusions
• Injection of byproduct Mg(OH)2 demonstrated
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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
Control of SO2 and SO3 Using Magnesium-enhanced Lime