1
THE EFFECT OF WATER (VAPOR-PHASE AND
CARBON) ON ELEMENTAL MERCURY REMOVAL IN
A FLOW REACTOR
Paper Number 255
Shannon D. Serre and Brian K. Gullctt
U.S. Environmental Protection Agency, National Risk Management Research Laboratory,
Research Triangle Park, NC 27711
Yong Hua Li
ORISE Post-Doctoral Fellow, U.S. Environmental Protection Agency, National Risk
Management Research Laboratory, Research Triangle Park, NC 27711
ABSTRACT
The effect of vapor-phase moisture on elemental mercury (Hg°) removal by activated carbon was
studied in a flow reactor. Tests were conducted in which activated carbon was injected into both
a dry and 4% moisture nitrogen (N2)/Hg° gas stream. A bituminous-coal-based activated carbon
(Calgon WPL) was injected into a Hg°-laden gas stream (124 ppbv) at 150 °C at carbon to
mercury ratios (C:Hg) between 1300 and 4400:1. The addition of 4% (vol.) water (H2O) into the
gas resulted in a -10% drop in removal (21-80%) compared to tests in dry N2 (26-89%). It is
hypothesized that the H2O molecules can form hydrogen bonds with the carbon thus reducing the
number of active sites available for Hg°.
The effect of activated carbon moisture content on Hg° removal was also studied. Darco FGD
(lignite-based) activated carbon was injected at 100 °C and a Hg° concentration of 86 ppbv. At a
C:Hg of 11000:1, Hg° removal for as-received Darco FGD carbon (3% moisture) was 30%.
Increasing the moisture content of the carbon to 16% resulted in a Hg° removal of 60%. Similar
tests in which the surface moisture in the carbon was reduced to 0% resulted in a Hg° removal of
less than 5%. Similar results were obtained with WPL. The effect of carbon moisture content on
Hg° removal was also tested in a simulated flue gas. Results in the flue gas from a methane
flame (doped with sulfur dioxide) showed that carbon surface moisture had a small impact
(positive) on Hg° removal by FGD carbon and no impact on removal by the WPL carbon.
The injection of dry activated carbon into a wet (4% moisture) N2 stream did not result in
increased Hg° capture. It is believed that the moisture did not have sufficient time to diffuse into
the carbon and mod'fy the carbon-oxygen functional groups that may be responsible for
adsorption.
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INTRODUCTION
Mercury is a naturally occurring element that is contained in coal. Mercury that is emitted from
coal-fired power plants can deposit in our rivers and watersheds and ultimately end up in the
food chain causing adverse health effects in humans. The EPA has determined that the emission
of mercury from co^l-fired power plants poses a risk to human health and the environment. The
EPA has announced its finding that regulation of mercury emissions from electric utility steam
generating units is necessary. Emission standards are to be proposed on or before December 15,
2003, and the standards arc to be promulgated by December 15, 2004
The concentration of mercury in coal is highly variable with average concentrations ranging
from 40 to 330 ppbw2. When coal is burned, mercury is vaporized. As the flue gas is cooled,
the mercury is present as one of several forms including elemental (Hg°) and oxidized species
such as mercuric chloride (HgCI2) and mercuric oxide (HgO) Mercury partitioning depends on
several factors including the type of coal burned; for example, Hg° is the dominant form when
burning North Dakota lignite3. The control strategy may depend on the form in which the
mercury is present. Oxidized species arc water-soluble and can be removed in units that have a
wet scaibber, whereas Hg° is insoluble in water 4,5,6 One of the methods that have been
demonstrated to remove Hg° as well as oxidized forms is adsorption using activated carbon.
Activated carbon is injected upstream of the particulate control device such as an electrostatic
precipitator (ESP) or fabric-filter baghouse where the carbon is removed with the fly ash. Higher
Hg° removals have been obtained in units that have a baghouse as compared to those that have
an ESP for particulate control.
Most bench-scale research on Hg° adsorption has been done in fixed-bed reactors which simulate
capture by a baghouse filter cake.7"10 Most coal-fired power plants use ESPs, in which there is a
short contact time between carbon and the gas to remove any Hg°. In this work a bench-scale
flow reactor was used to study in-flight capture of Hg° in the presence of carbon sorbents, thus
simulating capture through an ESP. The results obtained in this research will be compared to
those obtained in fixed-bed tests.
In previous work with the tlow reactor, the effects of particle size, temperature, carbon to
mercury ratio (C:Hg), and carbon type were examined11,1 In that work it was found that two
carbons with similar physical properties had different Hg° adsorption results in the flow reactor.
The main difference between the two carbons was the carbon moisture content. In other work,
Li et al.13 found that the surface moisture of activated carbon has a significant effect on Hg°
adsorption in fixed-bed reactors. The present study examines the effects of carbon moisture
content and vapor-phase moisture on Hg° removal in a flow reactor.
Activated carbons contain a variety of chemically reactive surface sites, such as hydroxyl,
carboxyl, quinone, peroxide, and aldehyde groups14. According to Bansal et al.15, these carbon-
oxygen surface complexes are by far the most important structures influencing the surface
characteristics and adsorption behaviors of activated carbons. Heating activated carbon and
reducing the amount of moisture in the carbon may reduce the number of surface carbon-oxygen
functional groups thus creating a less-reactive carbon. Carbon will also adsorb water from the
surrounding gas. Water molecules are first adsorbed on primary adsorption centers, such as
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3
oxygen groups, witli secondary adsorption occurring on the adsorbed water molecules 16. H2O
adsorption at lower relative pressures (e.g., P/Po < 0.4) has been correlated directly to the
amounts of chemisorbed oxygen on the carbon surface 15. It has also been shown that
interactions between !I20 and carbon-oxygen complexes influence the reactivities of activated
carbons for adsorption of organic vapors l7. In tests with a sulfur-impregnated carbon at 140 °C,
Liu et al.18 found that the adsorptive capacity of the carbon decreased by as much as 25% when
10% moisture was added to the gas stream compared to tests in dry N2.
EXPERIMENTAL
A schematic of the flow reactor is shown in Figure 1, and a more detailed description of the
experimental setup can be found in Serre et al.11'12. The quartz reactor is 310.5 cm long with an
inner diameter of 4 cm. Three gas sampling ports are located along the length of the reactor and
are labeled SP1, SP2, and SP3. The reactor is heated with three Lindberg, 3-zone electric
furnaces in series. The baseline Hg° concentration is measured in the absence of activated carbon
using an ultraviolet (UV) analyzer (Buck Scientific, model 400A). Once the baseline is
established, activated carbon is fed into the top of the reactor using a fluidized-bed feeder (0.2-
0.5 std. L/min). The gas-phase Mg° concentration is then measured at one of the sample ports by
pulling a gas sample (0.5 std. L/min) through a 1 (im filter to remove any particles, then through
a reducing furnace to convert any oxidized Hg to Hg° (method described in Ghorishi and Gullett
8). After the reducing furnace, the gas is dried using a Nafion® gas sample dryer (Perma Pure,
Inc.) and is finally sent to a Buck analyzer.
Initial tests were conducted using nitrogen (N2) as the carrier gas with later tests performed in a
flue gas from a methane flame. In the N2 carrier gas tests, industrial grade N2 [1 std. L/min (0
°C, 1 atm)] flows over a Hg° permeation tube that is housed in a permeation oven (VICI
Metronics, model 190) to generate a Hg°-laden gas stream. The N2/Hg° stream is diluted with a
second N2 stream (12 std. L/min) to the desired concentration before entering the top of the
reactor. Other gases (S02, NO, O2, water vapor) can be blended into the N2 carrier gas in the
mixing manifold.
In tests with the methane flame flue gas, methane was burned in a water-cooled burner and NO
and SO2 were added (post-flame). Table 1 shows the typical flue gas composition when
operating the flow reactor with flue gas.
A fluidized-bed feeder is used to inject sorbent into the reactor. An inlet line of N2 is used to
fluidize and carry the activated carbon to the reactor. The carbon feed rate is adjusted by varying
the amount of N2 (0.2 to 0.5 std. L/min) entering the feeder.
Because the UV analyzer used to detect Hg° is sensitive to particles, a filter was used to remove
any carbon that may have been carried with the gas. Tests were conducted to determine if
carbon particles were accumulating on the filter, as this would act like a packed bed and the
reactor's removal of Hg° would be a combination of in-flight + filter (packed-bed) capture.
Activated carbon was injected in the absence of Hg°, and a gas sample was pulled through the
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Table 1
Methane Flame Flue Gas Composition
Flue Gas
Concentration
Component
S02
500 ppm
NOx
200 ppm
C02
3.5%
CO
5 ppm
o2
7.1%
H20
6.8%
Fluidized Bed Feeder
{X Hg°/N2
{X Dilution N2
NO
CB
Air
SO:
SP 1
Lindberg
3-Zone
Furnaces
SP 2
Buck Hg SO2/O2
Analyzer Analyzer
SP 3
Filter Reducing Nafion
Furnace Drier
Carbon
Trap
Pump
Exhaust
Carbon
Trap
Figure 1. Schematic of the flow reactor with methane burner.
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filter. After 1 minute, Hg° was added to the gas stream to see if there was a lag in the time it
takes for the baseline to return. The results were the same as for a blank filter, suggesting that
the filter did not have an effect on the results.
The Hg° UV analyzer also responds to any SO2 that is present by increasing the signal on the
analyzer. The net increase in the signal is dependent on the SO2 concentration and was
compensated for by measuring the net increase and subtracting this number from the measured
Hg° concentration.
The total flow through the reactor was 13 std. L/min (0 °C, 1 atm) which gave residence times of
5.2, 11.5, and 17.7 s at ports SP1, SP2, and SP3, respectively. The velocity of the particles
through the reactor is assumed to be the same as that of the gas flow since the terminal velocity
of the particles is smaller than the velocity of the gas through the reactor, by a factor of 3.
Two activated carbons were tested, a lignite-based activated carbon (FGD, Norit Americas, Inc.),
and a bituminous-based carbon (WPL, Calgon Carbon Corp.). The carbons were size classified
to 4-8 ^im for the FGD and 5-25 |im for the WPL. The total surface areas, measured using an
adsorption apparatus (ASAP 2400, Micromeritics Inc.) based on the Brunauer-Emmett-Teller
(BET) method, were 515 for the FGD and 1080 m2/g for the WPL.
Activated carbon contains a small amount of moisture that remains from the activation process.
According to the literature from the carbon manufacturers, the amount of moisture in both the
WPL and FGD carbon should be less than 8% 19,2°. The amount of moisture contained in the
WPL and FGD carbons was checked using an infrared moisture determination balance (AND®
model AD-4714) at 120 °C for 20 minutes. The amount of moisture in the test samples was 3%
for the FGD carbon and 13% for the WPL carbon.
RESULTS AND DISCUSSION
Vapor-phase water
Since water vapor is one of the main products of combustion, its effect on Hg° removal must be
evaluated. The effect of vapor-phase water on Hg° removal, at a given C:Hg ratio, is shown in
Figure 2 for WPL. WPL was fed at a C:Hg ratio of 1250 to 4500:1 into dry nitrogen at 150 °C
and 124 ppbv Hg°. Hg° removal at ports SP1 (3.4 s) and SP3 (11.5 s) is shown. A Hg° removal
of approximately 90% was achieved at a C. Hg ratio of 4500:1 at SP3. Water was then added to
the system at a concentration of 4% (vol.). A 10% drop in removal occurred with the addition of
moisture to the N2/Hg° stream, compared to dry conditions. It is hypothesized that the water
molecules are competing for active sites by forming hydrogen bonds with the carbon thus
reducing the number of active sites available. At high enough concentrations water can
condense in the microporous regions and block access to pores in the carbon, though this is not
likely at a temperature this high. Liu et al.18 found that the total Hg° uptake capacity by a sulfur-
impregnated carbon did not change when 5% moisture was added to the gas stream in fixed-bed
tests. However, the same researchers found that when the vapor-phase moisture reached 10%,
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100
90
80
70
x—s
b 60
IS
1 50
4)
os
°m 40
X
30
20
10
0
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Carbon to Mercury Ratio
Figure 2 Effect of water in gas stream (4% vol.) on Hg° removal at 150 °C and a Hg°
concentration of 124 ppbv for WPL carbon,
the capacity dropped by 25%. Carey et al.21 examined the effect of water-vapor on Hg° capacity
in a fixed-bed reactor using simulated flue gas. They found that capacity was not affected when
water was present in concentrations of 1 to 10% at a temperature of 135 °C. Our experiments
resulted in a higher removal at longer residence times for both dry and moist carrier-gas
conditions (Figure 2).
Carbon water content
0 0
The effect of carbon moisture content on Hg removal at 200 °C and 44 ppbv Hg in a dry N2
atmosphere for the WPL carbon is shown in Figure 3. Hg° removal is shown for port SP3 (10.2
s). The diagonal band of points is Hg° removal for the as-received WPL (13% moisture) as a
function of C:Hg ra'io. Removal approaches 80% for the as-received carbon at a C.Hg of
16000:1. The amount of moisture in the carbon was then adjusted by heating the carbon at 110
°C under vacuum, resulting in carbon moisture contents of 0, 2.5, and 4%. These carbons were
then tested at a single C:Hg ratio.
The results of these experiments show direct correlation between Hg° removal and the moisture
in the carbon. As the carbon moisture content is reduced to 4%, Hg° removal decreases slightly
compared to the as-received carbon. Hg° removal approaches zero as the moisture in-the
As received carbon in dry N2 atmosphere
As received carbon in 4% H20/N2 atmosphere
¦ SP1 (dry Nj)
• SP3 (dry Nj)
~ SP1 (4% HjO)
O SP3 (4% HzO)
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90 1
80 •
70 -
60 -
g
"e3 50
>
o
E
£ 40 -
6Jj
X
30 -
20 -
10 -
0 -
0 2000 4000 6000 8000 10000 12000 14000 16000
Carl>on (o Mercury Ratio
Figure 3 Effect of carbon water content on removal for the WPL carbon at 200 °C and a Hg°
concentration of 44 ppbv in a dry N2 atmosphere at SP3 (10.2 s).
carbon approaches zero. Hg° removal for the 0% moisture sample is nearly zero compared to
80% for the as-received moisture content of 13% at a similar feed rate. In a N2 atmosphere the
presence of moisture in the carbon appears to be necessary for Hg° adsorption.
Evaporation or desorption of moisture from the carbon surface will occur when injecting a
moisture-containing sample into a dry atmosphere. The evaporation of moisture could create a
cooling effect of the carbon particle surface which could increase Hg° capture since removal has
7 8 22 23 24
been shown to increase with a decrease in temperature '' ' . In tests by Delage et al. , a dry
gas (nitrogen and oxygen) was blown over wet granular activated carbon bed to measure the
temperature drop of a carbon bed. A maximum temperature drop of 8 °C was obtained over
several minutes. The drop in temperature was attributed to the desorption of water from the
carbon surface. If the increase in Hg° removal was a sole result of the water desorption from the
carbon surface, the difference of Hg° removal between the 13 and 4% moisture samples would
be expected to be much larger than those between 4 and 2.5%, as well as between the 2.5 and 0%
moisture samples. A 10% difference in Hg° removal was obtained when the moisture content
decreased from 13 to 4%, while there was a difference of more than 25% between the 4 and
2.5% moisture carbon. This suggests that the increase in Hg° removal cannot be entirely
attributed to the cooling effect.
0%h2O f
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To further confirm the effect of surface moisture on Hg° removal, moisture was added to the as-
received FGD carbon and tested at 100 °C and 86 ppbv Hg° in a dry N2 atmosphere. The
moisture content was increased by placing the as-received FGD sample in a sealed container
with a pan of deionized water at 23 °C for 2.5 hr. After this period of exposure the moisture
increased to 16%. Results with the as-received FGD (3% moisture) are shown in Figure 4 by the
solid squares. At a C:Hg ratio of 11000:1, a removal of 30% was obtained. Tests were then
repeated using the moisture-enhanced carbon, shown by the circles in Figure 4. Increasing the
water content of the carbon increased Hg° removal. At a C:Hg of 11000:1, the removal doubled
from 30% for the 3% moisture carbon to 60% for the 16% water carbon. A sample was also
dried under vacuum at a temperature of 110 °C. The dried sample (0% moisture) is also shown
in Figure 4. The 0% moisture sample performed very poorly under these conditions, removal
was below 10% at a C Hg of 16000:1. These results with the moisture-enhanced carbon in
Figure 4 are similar to that of the decreased moisture samples in Figure 3. Thus, it can be
concluded that carbon surface moisture plays an important role in Hg° adsorption in N2.
Eliminating the moisture in the carbon deactivated or reduced some of the active sites in the
carbons.
As described previously, adsorbed surface moisture plays an important role in Hg° adsorption,
and the presence of surface moisture appears to be necessary for Hg° adsorption in N2. However,
it should be understood that, with microporous material such as activated carbon, adsorption is a
dynamic process and consists of several steps: bulk phase transportation, pore diffusion and
16% Moisture
3% Moisture
0% Moisture
T
0 2000 4000 6000 8000 10000 12000 14000 16000 18000
Carbon to Mercury Ratio
Figure 4 Hg° removal as a function of carbon water content for FGD carbon at 100 °C and 86
ppbv in a dry N2 atmosphere. The size of the carbon is 16-24 urn.
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9
adsorption. The dynamic effect of adsorption by activated carbon would be more pronounced in
a flow reactor system with a short residence time, than in fixed-bed reactor studies.
It was shown that Hg° removal correlates with carbon moisture content, but the addition of
moisture to the N? gas stream resulted in a slightly lower Hg° removal (Fig. 2). What happens
when dry activated carbon is injected into a gas stream that contains water? Will the carbon be
able to absorb moisture from the vapor phase thus increasing the carbon moisture content?
These questions are addressed in this section Hg° removal for WPL at 150 °C and 124 ppbv at a
C:Hg ratio of 3750:1 is shown in Figure 5 for 0 and 4% moisture contents. The first set of bars
for the 0% moisture carbon show that Hg° removal is below 5%. The addition of 4% water to
the nitrogen/Fig0 stream did not improve removal. The next data set for the 4% moisture carbon
shows a similar trend It appears that the water did not have time to diffuse into the carbon and
modify the carbon-oxygen functional groups that may be the active sites for adsorption.
4% H20 carbon
4% I J20 carbon
4% H20/N2
Figure 5 Hg° removal for WPL carbon with varying moisture contents in the carbon and gas
stream at 150 °C and a Hg° concentration of 124 ppbv at a C:Hg = 3750:1.
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10
Effect of carbon water content in a methane flame flue gas atmosphere
All the data presented to this point have been obtained in experiments with N2 as the carrier gas.
The effect of carbon moisture content on Hg° removal in a methane flame flue gas (doped with
S02 and NO) is shown in Figure 6 with a gas composition shown in Table 1. The 0 and 13%
moisture samples ofWPL were fed into the reactor at an average C:Hg ratio of 3100 (± 200):1.
Hg° removal for the 0% moisture sample was 10% and 17% for the 13% moisture sample. A
slight increase in removal was observed for the higher moisture containing carbon, though not as
great as was seen in the tests in dry N2. The main difference between the tests is the presence of
acid gases, which have been shown to have a negative effect on Hg° adsorption 25,26.
The two carbons (0 and 13% moisture) were also injected in the absence of S02. Hg° removal
increased to 21% for the 0% moisture WPL carbon and to 43% for the 13% moisture content
WPL carbon. Since SO? is present at a much higher concentration than the Hg°, the S02 may be
competing for the active sites in the carbon. The SO2 may also act as a poison for the active sites
that are responsible for Hg° adsorption. In fixed-bed tests by Miller et al.26, the addition of S02,
in the presence of NO;, resulted in desorption of any Hg° that had been captured by the carbon
sorbent.
50 •
40 ¦
30
c
B
V
©
W)
X
20
10 -
0
0% M,<) Carbon
(!% SO,
0% 11,(.) Carbon
500 ppm SO.,
13% II20 Carbon
0% SO,
! 3% H,0 Carbon
500 ppm S02
A
Figure 6 Effect of carbon moisture content on Hg° removal for WPL carbon (C Hg 3100:1) in
methane flame flue gas at 100 °C and 86 ppbv Hg° Error bars represent 1 standard deviation
(n:-3)
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u
Hg° removal for PGD carbon in a methane flue gas is shown in Figure 7 for a C:Hg of 10000 (±
1000):]. Increasing the moisture from 3% for the as-received carbon to 16% for the moisture-
enhanced carbon resulted in approximately a 2-fold increase in Hg° removal. Increasing the
carbon moisture did not produce the same results as seen in the N2 tests, similar to the WPL tests.
The effect of S02 was also examined. The presence of SG2 in the flue gas did not have an
impact on Hg° removal for both the 3 and 16% moisture samples. Other interactions may have
been occurring in the tests with flue gas Future tests are planned to further evaluate the effect of
S02 and NOx on Hg° control.
CONCLUSION
The effect of carbon moisture content on Hg° removal was tested for lignite- and bituminous-
coal-based carbons. The moisture content of the carbon had a significant effect on Hg° removal
in a N2 gas stream, simply increasing the moisture content resulted in an increase in removal.
Conversely, removing moisture from the carbon resulted in a decrease in removal. This suggests
that certain hydrated functional groups may act as active sites for binding Hg° Similar tests in a
methane flue gas showed a small improvement in Hg° removal for the FGD carbon with an
increase in carbon moisture. However, tests with the WPL carbon showed that carbon moisture
did not have an effect on removal in the flue gas. The main difference between the two sets of
tests (N2 vs. flue gas) is the presence of acid gases.
12
6% I IjO Carbon
500 ppm SOj
10
8
6
3% 1120 Carbon
0% SO,
4
2
0
Figure 7 Effect of carbon moisture content on Hg° removal for FGD carbon (C:Hg=10000:l) in
methane flame flue gas at 100 °C and 86 ppbv Hg°. Error bars represent I standard deviation
(n=3).
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The effect of vapor-phase moisture was also studied in N2. The addition of moisture to the gas
stream resulted in a slight decrease in Hg° removal. Water molecules may be forming hydrogen
bonds with the carbon, thus reducing the number of active sites available for Hg° Injecting a dry
carbon into a wet gas stream did not improve Hg° removal. The vapor-phase moisture may not
have had sufficient time to diffuse into the carbon pore structure and modify the carbon-oxygen
functional groups that may be the active sites for adsorption.
The presence of SO? in the flue gas had an effect on Hg° removal using the WPL (C Hg-3 100:1)
carbon, but not the FGD (C:Hg= 10000:1) carbon. Further tests are planned to examine the effect
of SO2 and other acid gases on Hg° removal using activated carbon.
REFERENCES
1. U.S. Environmental Protection Agency, http://www.epa.gov/mercury. accessed 01/2001.
2. Brown, T.D., Smith, D.N., Hargis, R A, O'Dowd, W.J. In Proceedings of the Air and Waste
Management Association's 92" Annual Meeting, St. Louis, MO, June 23, 1999,
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1798-1804, 1999.
4. Chang, R , Offen, G.R, Power Engineering, November 1995,
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Utility Air Pollution Control Symposium (The Mega Symposium), August 25-29, 1997,
Washington, DC.
6. Redinger, K.E.; Evans, A.P.; Bailey, R.T.; Nolan, P.S. In Proceedings of the First EPRI-
DOE-EPA Combined Utility Air Pollution Control Symposium (The Mega Symposium),
August 25-29, 1997, Washington, DC,
7. Krishnan, S.V.; Gullett, B.K.; Jozewicz, W. Environ. Sci. Technol., 28, 1506, 1994,
8. Ghorishi, B.; Gullett, B K Waste Manage. Res., 16, 582, 1998,
9. Vidic, R.D.; Chang, M , Thurnau, R C ,/. Air and Waste Manage. Assoc., 48, 247, 1998,
10. Jozewicz, W.; Krishnan, S.V.; Gullett, B.K. In Proceedings of Second International
Conference: Managing Hazardous Air Pollutants, July 13-15, 1993, Washington, DC.
11. Serre, S.D.; Gullett, B.K.; Ghorishi, S.B, In Proceedings of the Air and Waste Management
Association's 93rd Annual Meeting, Salt Lake City, UT, June 18-22, 2000,
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13
12. Serre, S.D.; Gullet! B.K.; Ghorishi S.B. ./. Air and Waste Manage. Assoc., submitted for
publication,
13. Li, Y.H.; Serre, S.D., Lee, C.W.; Gullett, B.K In Proceedings of the Air Quality II
Conference: Mercury Trace Elements, and Particulate Matter, September 19-21, 2000,
McLean, VA.
14. Bohm, H P, Carbon, 32, 759, 1994.
15. Bansal, R.C.; Don net J.B.; Stoeckli, F Active Carbon, Marcel Dekker, New York, NY, 1988.
16. Dubinin, M M : Serpinsky, V.V. Carhop 19, 402, 1981.
17. Biron, E.; Evans, M. Carbon, 36, 1191-1 197, 1998.
18. Liu, W.; Vidic, R.D., Brown, I' D Environ. Sa, Techno!., 34, 154-159, 2000. ¦
19. Calgon Carbon Corporation, Product Bulletin: WPL/WPM/WPH Powdered Activated
Carbons, Calgon Carbon Corp., Pittsburgh, PA, 1999.
20. Norit Americas Inc., Datasheet for DARCO FGD carbon, Atlanta, GA, 1997.
21. Carey T.R , Hargrove, O.W., Jr, Richardson, C.F.; Chang, R , Meserole, F.B. J. Air & Waste
Manage. Assoc., 48, 1166-1174, 1998.
22. Karatza, D.; Lancia, A.; Musmarra, D.; Pepe, F. Twenty-Sixth International Symposium on
Combustion, July 28 - August 2, 1996, Pittsburgh, PA.
23. Karatza, D.; Lancia, A.; Musmarra, D.; Pepe, F., Volpicelli, G. Hazardous Wastes and
Hazardous Materials, 13, 95-104, 1996.
24. Delage, F ; Pascaline, P.; Le Cloirec, P../. Envir. Engrg., 125, 1160-1167, 1999.
25. Dunham, G.E., Miller, S.J. Investigation of Sorhent Injection for Mercury Control in Coal-
Fired Boilers, Final report prepared for the Electric Power Research Institute and the U.S.
Department of Energy, September 1998.
26, Miller, S.J.; Dunham, G.E.; Olson, E.S.; Brown, T D In Proceedings of the Conference on
Air Quality: Mercury Trace Elements, and Particulate Matter, December 1998, McLean, VA.
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Tv,r>iv/rr>T dtd d con TECHNICAL REPORT DATA
JM rtlvi Iti_i til i" Jr~Doy (Please read Instructions on the reverse before completing)
lailHIIIIMI 1 Mil 111
1. REPORT NO. 2.
EPA/600/A-01/061
3, RECIP
III Nil II ¦¦¦
4. TITLE ANO SUBTITLE
The effect of Water (Vapor-phase and Carbon) on
Elemental Mercury Removal in a Flow Reactor
5. REPORT DATE
6. PERFORMING ORGANIZATION COOE
7. AUTHOR(S)
S. D, Serre, B.K, Gullett, and Y. H. Li (Post-
doctoral Fellow)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME ANO ADDRESS
See Block 12
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
NA
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PEFUOD COVERED
Published paper; 6/00-3/01
14, SPONSORING AGENCY CODE
EPA/600/13
15. supplementary NOTES appcd project officer is Shannon D. Serre, Mail Drop t>5» 919/
541-3817. Presented at AWMA Annual Conference, Orlando, FL, 6/24-28/01.
i6. ABSTRACTTlie paper gives results of studying the effect of vapor-phase moisture on
elemental mercury (Hgo) removal by activated carbon (AC) in a flow reactor. Tests
involved injecting AC into both a dry and a 4% moisture nitrogen (N2)/Hgo gas str-
eam. A bituminous-coal-based AC (Calgon WPL) was injected into an Hgo-laden gas
stream (124 ppbv) at 150 C at carbon-to-mercury ratios (C:Hg) between 1300 and 4400
:1. Adding 4% (vol.) water (H2C) into the gas .resulted in about a 10% drop in removal
(21-80%). compared to tests in dry N2 (26~8S%). The H20 molecules probably form
hydrogen bonds with the AC, reducing the number of active sites available for Hgo.
The effect of AC moisture content on Hgo removal was also studied. Darco FGD
(lignite-based) AC was injected at 100 C and 86 ppbv Hgo. At a C:Hg of 11000:1, Hgo
removal for as-received Darco FGD AC (3% moisture) was 30%. Increasing the moi-
sture content of the AC to 16% resulted in an Hgo removal of 60%. Similar tests, in
which the surface moisture of the AC was reduced to 0%, resulted in an Hgo removal
of < 5%. Similar results were obtained with WPL. The effect of AC moisture content
on Hgo removal was also tested in a simulated flue gas (small positive impact with
FGD; no impact with WPL). Injecting dry AC into a wet (4% moisture) N2 stream did
not increase Hgo capture. The moisture probably had insufficient time to diffuse into
the AC and modify the carbon-oxygen functional groups that may be responsible for
adsorption.
17. KEY WORDS AND DOCUMENT ANALYSIS
a, DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. cosati Field/Group
Pollution
Mercury (Metal)
Activated Carbon
Moisture
Vapor Phases
Pollution Control
Stationary Sources
Flow Reactors
13 B
07B
11G
07D
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
13
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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