Pilot Testing of Oxidation Catalysts for Enhanced Mercury Control by Wet FGD
Gary Blythe URS Corporation Austin, TX
Hg Control Technology Concept
• Catalytic oxidation of Hg0 in flue gas to increase overall Hg removal across wet FGD systems • Initial development is focused on PRB and lignite fuels - higher Hg0 percentages in flue gas • Catalyst to be installed at ESP outlet
Illustration of Process Concept
Mercury Oxidation Catalyst
ESP Wet FGD System (SO2/Hg Removal)
Process Development Background
• Initial concept development funded by EPRI (early 1990s) • Further development in DOE NETL/ EPRI co-funded MegaPRDA Project
– Lab screening of candidate catalyst materials – 6-month sand bed tests with promising catalysts at three coal fired sites – Completed in 2001
Current Project
• Conduct pilot-scale tests of honeycomb Hg0 oxidation catalysts at two sites
– – – – 4 catalysts tested in parallel (~2000 acfm each) 14-months automated operation at each site Monthly activity measurements with Hg SCEM Ontario Hydro relative accuracy tests at beginning, middle, end of test periods
• DOE/NETL, EPRI, utility co-funded • Host stations include ND lignite (GRE’s Coal Creek), PRB fuels (CPS’s Spruce)
Catalyst Types
• Metal-based
– Palladium (Pd #1) - both sites – Ti/V from Argillon (SCR) - both sites – Gold (Au) - Spruce only
• Carbon-based
– Experimental activated carbon (C #6) - both sites
• Fly-ash-based
– Subbituminous coal ash from one particular plant (SBA #5) - CCS only
Pilot Unit Concept
From ESP or Baghouse Induced Draft Fan
To FGD
Data Logger
FIC
TI
DPI
TE
Hg
Hg
Mercury Oxidation Catalyst
Pilot Testing Status
• First pilot unit started up at Coal Creek in October 02
– 2 of 4 catalysts installed (Pd #1 and SCR) – Delivery of other two catalysts delayed due to developmental nature of their production
– 3rd catalyst (SBA #5) installed December 02 – 4th catalyst (C #6) installed June 03
• Second pilot unit to start up at Spruce Plant later this month
Pilot Unit at Coal Creek Station
Catalyst Dimensions for Pilot Unit
Cells per in.2 Catalyst (cpsi) Pd #1 C #6 SBA #5 SCR 64 80* 80* 46 Cross Section (in. x in.) 30 x 30 36 x 36 36 x 36 35.4 x 35.4 Area Length Velocity (sft/hr) (in.) 9 9 9 19.7 49 27 27 14**
*Die sized for 64 cpsi, cores shrank during drying **1500 acfm, other catalysts operate at 2000 acfm
Photo of Argillon GmbH SCR Catalyst Module
One of Three SBA #5 Catalyst Modules
Close-up of One SBA #5 Block
Initial CCS Pilot Activity Results
Oct. 02 field results vs. lab predictions
100 Hg Oxidation Across Catalyst, % 90 80 70 60 50 40 30 20 10 0 0 10 20 30 40 50 60 Area Velocity, sft/hr Pd #1 - CCS Pd #1 - Predicted SCR - CCS SCR - Predicted
0
Pilot Results Through January 03
• Measured activity losses in Dec 02 and Jan 03 compared to initial Oct 02 results • Catalyst pressure drop data indicated fly ash buildup as a likely cause • Opened catalyst boxes, confirmed fly ash buildup • Used compressed air and vacuum to clean • Re-measured performance
Effect of Fly Ash Buildup, Cleaning on Catalyst Activity
Hg Oxidation across Catalyst (%) Catalyst (Flow Rate, acfm) Pd #1 (2000) SCR (1500 ) SBA #5 (2000) January (after October December January cleaning)
0
93 67 na*
53 28 na*
58 37 59
91 61 75
*na - catalyst not in service yet
Surface of Pd #1 Catalyst Prior to Cleaning
Surface of Pd #1 Catalyst after Cleaning
Efforts to Resolve Ash Buildup
• Identified sonic horns as a likely mechanism to limit fly ash buildup
– Commonly used to clean SCR catalysts – Easier to retrofit than soot blowers
• Tested horn (Analytec 17”) on Pd #1 catalyst chamber
– Installed on chamber inlet transition duct – Appeared effective in 2 mos. of operation – Installed on other chambers June 03
Sonic Horn Installation on Pilot Unit
Sonic Horn Locations
Catalyst Pressure Drop thru 5/27
(shows sonic horn effect on Pd #1 catalyst)
10 9 Catalyst Pressure Drop, in. H2O 8 Pd #1 7 6 5 4 3 2 1 0
0:01:42 10/1/02
5:01:43 10/31/02
6:01:41 11/30/02
8:01:42 12/30/02
8:01:59 1/29/03
10:35:10 3/1/03
6:01:40 4/1/03
10:43:38 5/11/03
Date/Time
Catalyst Pressure Drop since 6/5
(sonic horns in all 4 compartments)
2 1.8 Catalyst Pressure Drop, in. H2O 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 12:53:12 9:04:37 5:01:53 20:01:51 16:01:52 12:01:52 9:00:39 5:01:49 20:01:36 4:01:50 6/5/03 6/10/03 6/15/03 6/20/03 6/25/03 6/30/03 7/5/03 7/10/03 7/16/03 7/23/03 Date/Time SBA #5 SCR C #6 Pd #1
Catalyst Activity Trends over First 10 Months at Coal Creek
100 Hg0 Ox. Across Catalyst, % 80 60 40
Pd #1
Cleaned Installed Sonic Catalyst Horn
Cleaned Catalyst (removed light dusting)
20 0 1-Oct
C #6
1-Dec 31-Jan
2-Apr Date
2-Jun
2-Aug
2-Oct
Catalyst Activity Trends over First 10 Months at Coal Creek
100 Hg Ox. Across Catalyst, % 80 60 40 20 0 10/1
Installed Sonic Horn Cleaned Catalysts
0
SCR SBA #5
12/1
1/31
4/2 Date
6/2
8/2
10/2
Flue Gas Characterization Results
• Ontario Hydro results show good agreement with EPRI Hg SCEM • No effects seen on other flue gas species – Controlled Condensation results showed no oxidation of SO2 across catalysts
• Catalyst inlet and outlet SO3 ~0.1 ppmv
– No oxidation of NO across catalysts
• Inlet and outlet NO, total NOX values agree within <1 ppm
– M26a showed no change in HCl (~1 ppm) or HF (~6 ppm) across catalysts
Recent Lab Testing
• 1 to 2 l/min testing of catalyst cores in simulated flue gas (SO2, HCl, NOX, etc.) • Tested TVA’s patented gold catalyst in honeycomb form, varied gold loadings
– Activity compares favorably with Pd #1 – May be effective at lower loading on alumina than Pd #1 – Selected as 4th catalyst for Spruce (SBA #5 fly ash not a likely commercial catalyst source)
• Tested other catalyst materials at Spruce conditions
Results of Spruce Laboratory Simulations
100 90 80 % Hg0 Oxidation 70 60 50 40 30 20 0 20 40 60 80 Area Velocity (std ft/hr) 100 120 Pd #1, 3x, 1" length SBA #5, 0.5" length Au, 1x, 1" length (preliminary) Au 1x, 1"length, repeat SCR, 1"length C #6, 1"length
Catalyst Selection for Spruce Pilot
• Pd #1 and C #6 selected based on high activity at CCS • Au selected based on positive lab results
– Need field results to compare activity, life to Pd #1
• Will test SCR catalyst in spite of activity loss at CCS (although with increased catalyst depth) – Loss could be site specific based on previous PRDA sand bed results with other catalysts • All catalysts re-ordered at current pitch (Au the same as Pd)
Current Schedule
• Continue SCEM measurement trips to Coal Creek through early 04
– Conduct 3rd set of Ontario Hydro SCEM relative accuracy tests ~March 04
• Start up 2nd pilot unit at Spruce later in August
– Initial shake-down operation w/o catalysts this week – Expect Pd and Au catalysts by end of August – SCR and C #6 catalysts in October
Proposed Follow-on Project
• Proposal submitted in NETL large-scale Hg control testing solicitation • Would use existing pilot units to test Hg oxidation catalysts at 2 new sites starting Spring 04
– TXU’s Monticello Station (Tx lignite/PRB blend) – Duke Energy’s Marshall Station (low S Eastern bit.)
• Proposed effort would integrate new wet FGD pilot unit downstream of oxidation catalysts – 2000 acfm flow rate to match catalysts
– Would test LSFO vs. Mg-lime chemistries
Summary
• Pilot tests results verify previous sand-bed results for the ability to catalytically oxidize Hg0 in flue gases
– Honeycomb catalysts have achieved over 90% oxidation of Hg0 in ND lignite flue gas
• On-line cleaning (sonic horns) needed to prevent fly ash buildup in horizontal gas flow catalysts • Continued testing will establish catalyst lives for ND lignite and PRB coal types