Download - Mercury Measurement and Control
© 2012ADA-ES
Mercury Measurement and Control
Sharon Sjostrom & Connie Senior
ADA Environmental Solutions
NASDAQ: ADES www.adaes.com
Hot Topic Hour
April 12, 2012
© 2012ADA-ES
Topics to Cover
• Overview of MATS for existing & new plants
• Measurement of Hg
• Capabilities of available control technologies for
mercury control
• Coal to Stack: Integrated approaches for multi-
pollutant compliance
© 2012ADA-ES
MATS Final Limits (Coal)
• Standards for new units are based on outputs Subcategory Filterable PM HCl Mercury
New coal, 0.007 lb/MWh 0.0004 lb/MWh 0.0002 lb/GWh
≥8300 Btu/lb
New coal, 0.007 lb/MWh 0.0004 lb/MWh 0.040 lb/GWh
<8300 Btu/lb
Existing coal, 0.30 lb/MWh 0.020 lb/MWh 0.013 lb/GWh
≥8300 Btu/lb
Existing coal, 0.30 lb/MWh 0.020 lb/MWh 0.040 lb/GWh
<8300 Btu/lb
• Standards for existing units are based on inputs
• Standards for new units (bituminous,
subbituminous) are ~65 times lower than for
existing units!
© 2012ADA-ES
Mercury Measurement
• Continuous measurement of Hg required
– CEM or Sorbent Trap
• Emissions averaging
– For existing bituminous/subbituminous units, limit of
1.2 lb/TBtu (30-day average) or 1.0 lb/TBtu (90-day
average)
• Facility-wide averaging for similar units
• Challenges in measuring very low levels of Hg
© 2012ADA-ES
The Compliance Challenge
• Integrated Decisions
Multiple regulations. Decisions on one pollutant may affect
options for others
Long-range, multi-plant CapEx decisions, fuel decisions
• Tight Timeframes
Implementation by 2015 for MATS and CSAPR
Rapid, informed decisions are now required
• Limited Resources
Testing Services, Engineering and Construction Services,
APC Equipment, Chemicals
© 2012ADA-ES
Fuel Choice Affects MATS Compliance
• Mercury inputs vary by region and by mine
within a region
MATS sets limits on Hg emissions, not percent
reduction
The bar is higher (for control) when Hg input is higher
• SO2 and HCl emissions might also have to be
controlled under MATS (or CSAPR)
• Sulfur and chlorine in coal affect ability to reduce
Hg emissions
• Finding the perfect MATS coal…?
© 2012 ADA-ES
MATS Compliance Limits:
Example for Existing Bituminous Plant
Final MACT Limits:
PM,
lb/MMBtu
HCl,
lb/MMBtu
SO2,
lb/MMBtu1 Hg, lb/TBtu
0.03 0.002 0.2 1.2
Estimated control efficiency, based on fuel:
HCl SO21 Mercury
98% 97% 86%1Alternate acid gas l imit for units with scrubbers2Concentrations at 3% O2
INPUT COAL PROPERTIES
Coal Rank Coal S, wt% Coal Ash, wt% Coal HHV, Btu/lb Coal H2O, wt% Coal Cl, µg/g Coal Hg, µg/g
Bituminous 3.60% 10.30% 11,011 3.30% 1000 0.1
As-received coal composition Dry coal composition
© 2012ADA-ES
Factors Affecting Mercury Control
• Coal Type
Halogen content (Cl, Br, other)
Sulfur content
Mercury content
• Flue Gas
Acid Gases (HCl, SO2, SO3)
Gas Temperature
• Boiler type
• Emission Control Equipment (e.g. SCR, ESP, FF, etc.)
• ACI Design
Distribution, residence time, sorbent characteristics
Similar factors affect
Hg removal from
native carbon in ash
and activated carbon
injection
© 2012ADA-ES
Native Mercury Removal (Average %):
The Good, the Bad, and the Ugly… Bituminous Subbit. Lignite
CSESP 41 17 -2
+ WFGD 73 21 45
HS ESP 22 14
+ WFGD 44 25
FF 87 71
+ WFGD 78
SDA + FF 95 31 29
SDA + ESP 50 50
WPS 14 -2 30
Projected
for MATS
80-90+ 80-90+ 60-90+
Analysis of 1999 EPA ICR data
© 2012 ADA-ES
SCR plus FGD Increases Hg Removal
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Plant 6, U4
(SCR off-line)Plant 6, U4 Plant 7, U1
(SCR off-line)Plant 7, U1
Tota
l Hg
Rem
ova
l
Source: Bituminous-fired plants
from Consol sampling program
© 2012 ADA-ES
SCR-FGD Reduces Hg Emissions
Source: Bituminous-fired plants
from Consol sampling program
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Plant 3, U2
Plant 4, U1
Plant 4, U2
Plant 5, U1
Plant 6, U4
Plant 7, U1
Plant 8, U1
Plant 9, U1
Plant 10, U2
Tota
l Hg
Rem
ova
l
…but >90% removal not always achieved
and trim control with ACI might be needed
© 2012ADA-ES
Halogens Increase Oxidized Mercury
0
20
40
60
80
100
0 500 1000 1500 2000 2500 3000
Halogen in Coal, ppmw dry
%O
xid
ize
d H
g a
t A
ir P
reh
ea
ter
Ou
tle
tNaCl
MgCl2
CaCl2
HCl
CaBr2
Halogen addition at various full-scale PRB boilers
Source: Dombrowski et al., 2006
© 2012ADA-ES
Benefits of Oxidized Mercury
Many plants’ APCDs can take advantage of native
capture…if there’s enough oxidized Hg (Hg2+)
0%
20%
40%
60%
80%
100%
0% 20% 40% 60% 80% 100%
Rem
oval of
Hg a
cro
ss F
GD
Fraction Hg2+ at Inlet
Dry FGD, FF
Wet FGD
© 2012ADA-ES
Halogens in Wet Scrubbers
• Adding halogens (Cl or Br) increases oxidized Hg,
which increase capture of Hg in scrubber
• Wet FGD scrubbers remove halogens efficiently
– Average Cl removals for wet FGDs (2010 ICR): 81% for
subbituminous, 97% for bituminous
– Removal of Br at Plant Miller wet FGD: 94-96%
(Dombrowski et al., 2008)
• Halogens build up in wet scrubber liquor
© 2012ADA-ES
Corrosion in Flue Gas
• Indirect evidence that HBr
might be more corrosive
than HCl at flue gas
temperature
• No direct comparison, but
HBr corrosion higher than
baseline (no HBr) in
simulated flue gas
(6-month study)
0
0.02
0.04
0.06
0.08
0.1
0.12
0 100 200 300 400
Co
rro
sio
n l
oss
, m
m
Temperature, oF
Baseline
51 ppmv HBr
• Chlorine corrosion in furnaces can occur for very
high levels of chlorine in coal (> 2000 µg/g)
– Bromine addition at much lower concentrations
Zhuang et al., 2009
© 2012ADA-ES
US Coal-Fired Generation Fleet
More than 1100 units in
operation
~ 317 GW
~ 66% have SO2 or
NOx controls
Unscrubbed units
~ 50 GW bituminous
~ 60 GW subbituminous
*http://www.eia.gov
0
20
40
60
80
100
120
140
Ge
ne
rati
on
(G
W)
FGD+SCR
SCR
FGD
None
© 2012ADA-ES
Activated Carbon Injection
Configuration Range of AC for 90% Control
(lb/MMacf)
PRB/SDA/FF 1 to 3
PRB/Toxecon 2 to 4
Bit/Toxecon 2 to not achieved
PRB/ESP 2 to not achieved
Bit/ESP 2.5 to not achieved
EPA Estimates 141 GW new ACI
© 2012 ADA-ES
Activated Carbon Injection
Performance Depends on Fuel Choice
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 Injection Concentration (lb/MMacf)
Hg
Re
mo
va
l (%
)
PRB ESP
SDA + FF
LS Bit ESP
ESP with SO3
Conditioning
HS Bit ESP
© 2012ADA-ES
SO3 Injection and PAC Effectiveness • Any SO3 in gas phase appears to affect Hg capture
– SO3 is used to condition fly ash for better capture in ESPs
– SO3 higher in bituminous flue gas, especially after SCR
• Typical injection targets < 10ppm in gas phase
0
10
20
30
40
50
60
70
80
90
100
0 2 4 6 8 10
PAC Injection (lb/MMacf)
Hg R
emoval
(%)
No injected SO3
5.4 ppm SO3
10.7 ppm SO3
Ameren Labadie Data: DOE DE-FC26-03NT41986 and
EPRI PRB, ESP
0
20
40
60
80
100
0 2 4 6 8 10
SO3 Off
SO3 On
Sorbent Injection Ratio (lb/MMacf)
Mer
cury
Rem
ov
al (%
)
Mississippi Power Plant Daniel
Low sulfur bituminous coal
© 2012ADA-ES
Compliance Strategies for Mercury
• 80 to >90% control at the stack to meet proposed
MATS emission limits required for most units
• For units with FGD/SCR:
Low conversion SCR catalyst and minimize ammonia slip
Minimize re-emission of Hg0 from wet FGD
• MATS limits achievable with ACI or ACI + coal
additives on most subbituminous units if SO3 flue
gas conditioning (FGC) is eliminated
• MATS limits may be challenging on units with
higher sulfur coals and may require SO3 mitigation
© 2012ADA-ES
Coal to Stack: Integrated
Approaches for Multi-Pollutant
Compliance Examples:
Fuel (low mercury, low sulfur, low chlorine)
DSI as required to meet HCl limits and/or control
SO3 to maximize ACI effectiveness
Manage SCR operation and catalyst choice to
increase fraction of oxidized mercury and
resulting removal in WFGD
Utilize coal additives to manage ACI usage and
Hg removal effectiveness
© 2012 ADA-ES
DSI-ACI Synergy: Example
Medium-sulfur
bituminous plant
Lime injection to
reduce SO3 =>
improve ACI
performance for Hg
control
0
20
40
60
80
100
0 5 10 15 20
% V
ap
or-
ph
ase R
em
oval w
rt B
aselin
e M
easu
rem
en
t
Sorbent (lb/MMacf)
Shawville 3, ESP 1 Darco Hg
Shawville 3, ESP 1 Lime/Darco Hg
© 2012 ADA-ES
DSI-ACI Synergy: Example
Low-sulfur bituminous plant with SCR
Trona injection to reduce SO3 => improve ACI
performance for Hg control
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20
% V
ap
or-
ph
as
e R
em
ov
al
Sorbent (lb/MMacf)
Merrimack 2, Darco Hg-LH
Merrimack 2, Darco Hg-LH, APH In, normal CEA
Merrimack 2, Darco Hg-LH, Trona, normal CEA
Merrimack 2, Darco Hg-LH, Trona, low CEA
Merrimack 2, Darco Hg-LH, Mill Trona, low CEA
Effect of SO3 sorbent
Effect of temperature
Effect of milling
© 2012ADA-ES
Summary: The Multi-Pollutant View Mercury
• 80 to >90% control required for most units
• Achievable on most subbituminous units if
SO3 FGC is eliminated
• Limits may be challenging on units with higher sulfur
coals and may require SO3 mitigation
HCl
• > 90% control required for most bituminous units. May
require new scrubbers for some units.
• < 80% control required for most plants with low-rank
coals. Should be achievable with fuel management,
DSI or existing FGD for most plants.
Total PM
• May result in several new fabric filters