Oxidation of Mercury Across SCR Catalysts in Coal-Fired Power Plants Burning Low Rank Fuels
(DE-FC26-03NT41728) Presented at Mercury Control Technology R&D Program Review Pittsburgh, PA • August 12-13, 2003
77 West 200 South, Suite 210 Salt Lake City, Utah 84101 REACTION ENGINEERING INTERNATIONAL
Project Objectives
• Gather data on the behavior of mercury across SCR catalysts
– Increase understanding of Hg behavior – New model
• Measurements at one power plant burning bituminous/subbituminous blend • Slipstream reactor with six catalysts
– One blank honeycomb – Three commercial honeycomb catalysts – Two commercial plate catalysts
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Project Organization
• Slipstream reactor built under catalyst deactivation program (DE-FC26-00NT40753; Bruce Lani, COR) • Mercury testing carried out under separate program (DE-FC26-03NT41728; José Figueroa, COR) • Additional support from EPRI and Argillon GmbH • Field test support from AEP
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Project Team
REI: Planning/analysis, slipstream reactor operation
– Connie Senior, Temi Linjewile, Darren Shino, Dave Swensen
URS: Mercury measurement and analysis
– Carl Richardson, Mandi Richardson, Tom Mahalek
AEP: Field test support and program review
– Steve Pfeister, Steve Batie – Gary Spitznogle, Aimee Toole
Program review
– José Figueroa, Bruce Lani, Lynn Brickett (DOE-NETL) – Chuck Dene (EPRI) – Jeanette Bock (Argillon GmbH)
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Testing Summary
• Rockport:
– Two 1300 MWe B&W opposed wall-fired, supercritical boilers – Testing on Unit 1 across air preheater
• Burn a bituminous-subbituminous blend • Two test series (March and August) • FIRST TEST SERIES:
– Boiler held at full load, 7:00 to 19:00 during test days – Ontario Hydro measurement at inlet to SCR reactor (3/28/03) – SCEM measurements made 3/28-4/2/03 – Coal and ash samples collected
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Multi-catalyst Slipstream Reactor
One SCR Inlet Heated Sample Line Pneumatic Isolation Valve
Ammonia Injector Ontario Hydro Sample Port Duct Wall Flue Gas
SCR Reactor
Six SCR Outlet Heated Sample Lines to Sequencer
Duct Wall
Flue Gas
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Catalyst Dimensions
Chamber: Catalyst type: Chamber porosity: Length of catalyst in chamber (inch):
2.5" out 2.5" out 5.0" out
1 (Blank) Monolith 58.7% 24.40
2 Monolith 70.0% 21.50
3 Plate 85.0% 39.25
4 Plate 86.9% 43.25
6 Monolith 70.0% 20.06
5 Monolith 68.3% 19.75
2.25 x 2.25 inner dimension
4.75 x 4.75 inner dimension
5.0" out 1/8" wall thickness
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Semi-continuous Hg Monitor (URS)
SCEM Instrumentation Clean Flue Gas Sample Data Acquisition and Control Amalgamation Unit
Ice Bath Impingers CVAA MFC Sampling Pump
KCl Or SnCl2
NaOH
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Coal Properties
Date (As Received): Carbon Hydrogen Oxygen Nitrogen Sulfur Ash Moisture HHV (Dry Basis): Hg, ug/g Cl, ug/g SO2, lb/MBtu Hg, lb/TBtu 3 Hg, ug/dnm (5%O2) 3/28/03 50.67 3.51 10.89 0.76 0.32 5.12 28.74 8,723 4/1/03 51.80 3.64 11.04 0.78 0.30 5.99 26.45 8,989 4/2/03 51.75 3.46 11.18 0.75 0.37 6.10 26.39 8,989
0.088 120 0.74 10.10 8.02
0.118 160 0.67 13.13 10.82
0.091 200 0.82 10.13 8.46
• Coal blend – mostly subbituminous • Higher Cl than typical subbituminous • 8-10 µg/dnm3 Hg (gasphase equivalent) • Ash contains ~6 wt% Fe2O3, ~16 wt% CaO
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Flue Gas Composition
Est. Gas Composition Excess Air O2 CO2 H2O N2 SO2 [ppm] HCl [ppm]* NOx [ppm]* 3/28/03 35% 4.0% 13.3% 10.6% 72.0% 317 7.5 400 4/1/03 35% 4.0% 13.4% 10.2% 72.3% 292 10.1 400 4/2/03 35% 4.0% 13.5% 10.0% 72.4% 360 12.8 400
• Calculated from coal analysis and measured O2, except NOx
*Estimated
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Hg and Cl in ash
% Hg in Ash 0.03% 0.41% -0.44% 0.55% % Cl in Ash 1.71% 1.21% -1.20% 1.11%
Ash sample Economizer ESP, silos 3&4 ESP, silos 3&4 ESP, silos 3&4 ESP, silos 3&4
Date 3/28/03 3/28/03 3/31/03 4/1/03 4/2/03
LOI, wt% 0.08% 0.31% 0.37% 0.31% 0.34%
Hg, ug/g 0.0053 0.0809 0.118 0.127 0.101
Cl, ug/g 28.6 20.2 24.6 23.6 26.8
• • •
Economizer ash has 10-20 times less Hg than ESP ash ESP ash has very little Hg, ~0.5% of coal Hg Cl content of ash is similar in economizer and ESP, ~1.5% of coal Cl
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Ontario Hydro Data
9
Particulate
8 7
Hg, ug/dNm 3 (5% O 2)
Oxidized Elemental
6 5 4 3 2 1 0 1 2 3
• Hg conc. in ash higher than in ESP fly ash • BUT fraction of Hg in ash very low • 81% elemental Hg
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Comparison of Hg: Coal v. SCEM
12 Coal analysis 10 SCEM OH
Hg, ug/dm 3, at 5% O 2
8
6
4
2
0 3/28/2003 3/29/2003 3/30/2003 3/31/2003 4/1/2003 4/2/2003
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Testing Summary: Reactor and Flue Gas
Temperatures, F Boiler Duct 727 719 719 717 724 726 Space NH3 (avg) Entrance Chamber Velocity ppm 651 631 602 625 641 658 657 657 657 656 662 667 medium medium low medium medium high 408 452 555 523 0 435 6.04 4.81 Inlet Mercury HgT, Hg0, 3 ug/Nm , ug/Nm 3, %Elemental Hg 5% O2 5% O2 6.17 5.88 5.00 4.82 7.64 8.00 7.00 7.75 7.82 6.47 6.47 93% 80% 81% 74% 71% 56%
Date 3/28/03 3/28/03 3/31/03 4/1/03 4/1/03 4/2/03 4/2/03
Space velocities (1/hr): “low” ~ 3,000 “medium” ~ 6,000-8,000 “high” ~ 12,000-14,000
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28 March, Hg0: 6,000 hr-1, with ammonia
28-March-2003: with ammonia, ~6000 hr-1
Elemental Hg (ug/Nm3 at 5% O2)
Elemental Hg (ug/Nm3 at 5% O2)
28-March-2003: with ammonia, ~6000 hr-1
7 6 5 4 3 2 1 0 8:24:00 10:48:00 13:12:00 time 15:36:00 18:00:00 inlet C1 C2 inlet
8 7 6 5 4 3 2 1 0 8:24:00 10:48:00 13:12:00 time 15:36:00 18:00:00 Inlet C1 C2 Inlet inlet C2
inlet
inlet
• • • •
Initial data points not used to calculated standard deviation (right-hand graph) Inlet elemental Hg consistent over time C1 (blank) did not show oxidation C2 showed oxidation
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28 March, HgT: 6,000 hr-1, with ammonia
28-March-2003: with ammonia, ~6000 hr-1
9 8 7 6 5 4 3 2 1 0 16:48:00
9 Total Hg (ug/Nm3 at 5% O2) 8 7 6 5 4 3 2 1 0 16:48:00 17:16:48 time 17:45:36 18:14:24 inlet C1 C4
28-March-2003: with ammonia, ~6000 hr-1
Total Hg (ug/Nm3 at 5% O2)
inlet C1 C4
17:16:48
17:45:36
18:14:24
18:43:12
19:12:00
time
• Initial data points not used to calculated standard deviation (right-hand graph) • Total mercury the same at inlet and outlet of C1 (blank) • C4 may indicate loss of Hg across catalyst
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Oxidation of Hg0 Across Catalyst
140% 120% Net oxidation of elemental Hg, % 100% 80% 60% 40% 20% 0% -20%
one (blank)
two
three
four
five
six
No NH3 NH3
• • • • • •
No oxidation across blank Some increase in oxidation w/o NH3 SV ~ 7,000 hr-1 T ~ 660 F 380-450 ppm NH3 Errors estimated from quadratic eqn.
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Loss of HgT Across Catalyst
80%
one (blank)
60%
two
three
four
five
six
No NH3 NH3
•
40%
20%
0%
• • • • • •
-20%
Loss of Hg across commercial catalysts observed No loss across blank No clear effect of NH3 SV ~ 7,000 hr-1 T ~ 655 F 420-540 ppm NH3 Errors estimated from quadratic eqn.
Net loss of Hg, %
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Loss of Elemental Hg as a Function of Space Velocity
120% one (blank) 100% two three four five six
net loss of elemental Hg, %
80%
60%
40%
20%
0%
-20% 0 5,000 10,000 15,000 Space velocity, hr-1
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20,000
25,000
30,000
Catalyst Types
100% one (blank) two five six
100% one (blank) 80% net loss of elemental Hg, % three four
80%
net loss of elemental Hg, %
60%
60%
40%
40%
20%
20%
0%
0%
-20% 0 5,000 10,000 15,000 20,000 25,000 30,000 Space velocity, hr-1
-20% 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 Space velocity, hr-1
Honeycomb Catalysts
Plate Catalysts
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Conclusions
• Blank monolith did not oxidize Hg0 • Commercial catalysts oxidized Hg0 • Oxidation of Hg0:
– Function of space velocity (at constant T) – Monoliths generally had same behavior vs. SV – Plate catalysts behaved differently
• Loss (adsorption?) of Hg:
– – – – – No loss of Hg across blank Some loss of HgT across catalysts, but no clear effect of NH3 No clear effect of catalyst pressure drop Assumption that lost Hg0 was oxidized Sampling system problems? Loss of Hg+2?
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Next Test Series: Priorities and Plans
• • • • In progress (August 7 – August 15) Make gas-phase Cl measurements Make simultaneous NOx measurements Look at transients with sample line switch and ammonia on/off • Repeat Hg0 measurements at one SV
– With and without ammonia – NH3/NO ~ 0.9, maybe lower – Determine whether oxidation changes with aging
• Look at possible sampling system effects on loss of Hg
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