Simultaneous Control of Hg°, S02? and NOx by Novel
Oxidized Calcium-Based Sorbents
Paper # 243
S. Behrooz Ghorishi, Carl F. Singer, and Wojciech S. Jozewicz
ARCADIS Geraghty & Miller, Inc., 4915 Prospectus Drive, Durham, NC 27713
Charles B. Sedman and Ravi K. Srivastava
U.S. Environmental Protection Agency, Office of Research and Development, National Risk
Management Research Laboratory, Air Pollution Prevention and Control Division (MD-65),
Research Triangle Park, NC 27711
ABSTRACT
Efforts to develop multipollutant control strategies have demonstrated that adding certain
oxidants to different classes of calcium-based sorbents leads to a significant improvement in
elemental mercury vapor (Hg°), sulfur dioxide (SO2), and nitrogen oxides (NOx) removal from
simulated flue gases. In the study presented here, two classes of calcium-based sorbents
(hydrated limes and silicate compounds) were investigated. A number of oxidizing additives at
different concentrations were used in the calcium-based sorbent production process. The Hg°,
S02, and NOx capture capacities of these oxidant-enriched sorbents were evaluated and
compared to those of a commercially available activated carbon in bench-scale, fixed-bed, and
fluid-bed systems. Calcium-based sorbents prepared with two oxidants, C and P, exhibited Hg°
sorption capacities (about 100 pg/g) comparable to that of the activated carbon; they showed far
superior S02 and NOx sorption capacities. Preliminary cost estimates for the process utilizing
these novel sorbents indicate potential for substantial lowering of control costs, as compared to
other processes currently used or considered for control of Hg°, SO2, and NOx emissions from
coal-fired boilers. The implications of these findings toward development of multipollutant
control technologies and planned pilot and field evaluations of more promising multipollutant
sorbents are summarily discussed.
INTRODUCTION
Of all trace metals emitted during fossil fuel combustion and waste incineration, mercury is
likely considered the most problematic. This concern is based on a combination of issues,
including: the propensity of mercury to concentrate and bioaecumulate by up to a factor of
10,000 within the aquatic food chain;1,2,3,4 documented adverse health effects associated with
mercury exposure;5,6"7'8 and, most importantly, the inability of current pollution control
technologies and strategies, designed primarily for particulate matter (PM), NOx, and S02, to
effectively control volatile mercury species. Modifying existing technologies or developing a
one-step multipollutant control technology capable of simultaneous control of mercury species,
PM, NOx, and SO2, would seem to be sensible and cost-effective approaches to solve this
problem.
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Research on mercury emissions control from coal-fired combustors is currently focused on
activated carbon sorption of mercury compounds9'll)' 12,13> 14,15 or changing the mercury
speciation in the flue gas to water-soluble ionic mercury species (Hg+2) that can be absorbed by
conventional wet SO2 scrubbers.16 While activated carbon is effective for the capture of both
major mercury species, Hg° and Hg+\ it represents an expensive additional technology
specifically designed to control mercury emissions only. As shown in this study, activated
carbons are not effective SO? sorbents; thus, activated carbon injection cannot be considered as a
viable multipollutant control technology. Wet S02 scrubbers are employed only on a fraction of
coal-fired boilers and are capable of removing only Hg+2 Some data suggest that Hg° vapor
concentration can actually increase across a wet limestone scrubber, presumably due to the
reduction of Hg+2 by sulfite in the scrubber.17
In addition, recent data analyses by the U.S. Environmental Protection Agency (EPA) conclude
that in 1999, utility boilers emitted 43 tons of mercury or 57% of mercury contained in coal
burned.18 An evaluation of these data shows mercury to be retained by fly ash and collected in
PM control devices. Potential multipollutant mercury control strategies therefore include:
•	Enhancement of PM control technologies with sorbent injection and/or gas cooling
•	Addition of oxidation catalysts, flue gas oxidants, or scrubber liquor oxidants, which increase
the collectible Hg+~, in conjunction with wet SCb scrubbers
The development of better sorbents for mercury can lead to better ways of augmenting PM
devices, but the most cost-effective use of improved mercury sorbents would appear to be in
absorption technologies that remove several pollutants. By using sorbents that also offer
oxidation potential, all mercury species may be removed with acid gases in certain types of
semidry absorbers, and NOx reductions (through conversion of NOx species to more reactive
forms) may also be obtained. This type of application is the focus of the remaining discussions
on multipollutant sorbent development.
Previous investigations I9'20 have shown that modified calcium (Ca)-based sorbents have a
potential to be viable multipollutant (Hg°, Hg'2, and SC)2) sorbents, thus providing the operators
of coal-fired power plants and waste incinerators with a practical multipollutant control strategy.
It was previously established that mercuric chloride (HgCb) vapor is readily adsorbed as an acid
gas by conventional Ca-based sorbents such as hydrated lime12, while Hg° is partially adsorbed
by Ca-based sorbents when significant modifications are implemented in the sorbent production
process.19,20 Further improvement in the Hg° uptake capabilities of these modified Ca-based
sorbents was necessary before they could be considered as attractive total mercury sorbents.
Current efforts, described in this paper, have attempted to improve the uptake of Hg° by
increasing the number of active sites and adding oxidative species to Ca-based sorbents. Based
on the previous investigations,19'20 the key assumptions for this study were that Ca-based
sorbents, modified or unmodified, will adsorb S02 and Hg+2; and that modified Ca-based
sorbents, having both fine pore structure and oxidizing species in the pore structure, can oxidize
and sequester Hg° and NOx from flue gas. The improvement in the capture of Hg° and NOx by
the oxidant-enrichcd Ca-based sorbents makes them an attractive choice for a multipollutant
control technology.
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PREVIOUS STUDIES ON OXIDANT-ENRICHED Ca-BASED SORBENTS
An earlier study demonstrated that adding oxidants to Ca-based sorbents during their production
process could significantly increase the Hg° uptake capabilities of these sorbents.20 One class of
these Ca-based sorbents, termed "oxidized hydrated limes," was prepared by hydrating
commercial quicklime in the presence of an oxidant in solution. Different concentrations of
oxidant in solution were used. It was shown that the hydration process in the presence of oxidant
solution (as opposed to water) had no effect on the total surface area of these sorbents (13-15
m7g). Oxidized hydrated limes, on average, exhibited a 2-3 times higher Hg° uptake than the
baseline hydrated lime prepared in the presence of water. Increasing the strength of oxidant
solution (from 6 to 30%) increased the Hg° uptake by a factor of 2. It was hypothesized that the
hydration of quicklime in the presence of an oxidant creates active sites. The presence of
oxidizing sites was further confirmed by thermal decomposition to oxygen using thermo-
gravimetric analysis (TGA) coupled with residual gas analysis (RGA). Although an
improvement in Hg° uptake could be achieved by oxidized hydrated lime, the overall uptake was
a factor of 10 lower than a commercially available activated carbon (DARCO FGD, Norit
Americas Inc.). This lower activity was then attributed to the much lower surface area of
oxidized hydrated limes (13-15 m2/g), as opposed to the FGD activated carbon (514 m2/g).
Another class of high-surface-area Ca-based sorbents, silicate sorbents, has been prepared
extensively in EPA laboratories. Silicate sorbents are hydrated lime and silica source reaction
products, a calcium silicate gel. This calcium silicate gel has high surface area (100-200 m2/g),
thin layers of free lime [Ca(OH)2], and substantial moisture that allows simultaneous in-duct
absorption of acid gases and flue gas cooling.21,22,23
It was hypothesized that adding oxidant to silicate sorbents should result in a more efficient Hg°
sorbent due to improved dispersion of active sites over a larger surface area. Placing the oxidant
on the calcium-silicate sorbents proved to be problematic due to oxidant decomposition. Rather
than incorporating the oxidant solution in the calcium-silicate reaction, oxidant solution was
added to the finished dry silicate sorbent. No significant improvement in Hg° uptake was
observed. The oxidant was believed to have decomposed prior to the formation of significant
active sites. This observation, and the fact that oxidized hydrated limes described above were
significantly less efficient in capturing Hg° than an activated carbon, prompted the exploration of
more effective oxidants.
By changing oxidants, decomposition of these compounds may be manageable, resulting in
dispersed oxidant in the pore structure of the Ca-based sorbents. These active sites will be
available to oxidize and sequester Hg°, NOx, and SO?, upon exposure. A series of oxidants and
Ca-based sorbent production processes were investigated. Oxidant-enriched hydrated limes and
silicate sorbents were screened based on Hg°, NOx , and S02 capture efficiency. The capture
efficiency of sorbents toward Hg° and SO2 was further compared to that of an activated carbon.
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SORBENT PREPARATION
Oxidant-Enriched Hydrated Lime
Lime sorbents were prepared with commercial powdered quicklime (Marblehead Lime Co.) and
degassed deionized (DI) water. The indicated oxidant was added to the quicklime prior to
hydration at a rate of 0.1 equivalents per mole of quicklime. Four oxidants were screened, and
designated S, N, M, and C. Quicklime was hydrated in a sealed Parr Bomb reactor with
stoichiometric water for 30 minutes. As a precaution against further oxidant decomposition,
sorbents were then stored in sealed containers without further drying. The surface areas of these
sorbenls are shown in Table 1.
Table 1. Specific surface area of screened hydrated lime sorbents.
Sorbent
BET Surface Area, m2/g
Baseline lime
11.03
S lime
14.39
N lime
9.54
M lime
14.28
C lime
11.36
Oxidant-Enriched Silicate Sorbents
Silicate sorbents were prepared in glass beakers in a double boiler configuration. Equal parts of
silica fume and reagent grade hydrated lime were slurried in a 90 °C solution of a wetting agent and
degassed DI water for 2 hours. The slurry was vacuum filtered through Whatman #42 paper, and
the filter cake was dried overnight in a vacuum oven at 100 °C. Five milliliters of a 1 mM lime
solution was added to a 60 °C heated mortar containing 0.5 g of the indicated oxidant. Ten
grams of dry silicate was added to the solution in the mortar and mixed. Contents of the mortar
were transferred to a watch glass and dried overnight in a 100 °C vacuum oven. Selected
physical properties of these sorbents are shown in Table 2. Silicate surface areas do not appear
to be greatly affected by the addition of oxidant; however, the surface area remains substantially
less than that of FGD activated carbon (514 m2/g).
Table 2. Specific surface area of screened silicate sorbents.
Sorbent
BET Surface Area, m2/g
Baseline silicate
101.79
M silicate
95.54
C silicate
90.90
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EXPERIMENTAL APPARATUS
Bench-scale Hg0/SO2 removal tests were performed on a vertical fixed-bed reactor apparatus;
operation and construction details of this apparatus have been previously described.1 '19 A
simulated flue gas was generated containing 40 ppbv Hg°, 4 mole% oxygen (O2), 10 mole%
carbon dioxide (CO2), 1 mole% water vapor (H20), and 500 ppmv SO2. Simulated flue gas was
then passed through the sorbent bed, a Lindberg furnace, a NAFION™ Dryer, and serial
ultraviolet Hg° and SO2 analyzers. Sorbent was exposed to 300 cm3/min [dry at standard
temperature and pressure (STP)] simulated flue gas for 2 hours at 80 °C reactor temperature.
The Lindberg furnace was maintained at 100 °C to prevent condensation and to avoid
undesirable reactions. Breakthrough curves from Hg° and S02 analyzers were integrated to
obtain uptake during the 2-hour exposure.
Simultaneous evaluations of Hg°, NOx, and S02 on the fixed-bed reactor were confounded by
experimental artifacts encountered with the NAFION™ Dryer. The further desire to more
closely simulate anticipated field activity led to the construction of a fluidized-bed reactor
apparatus designed to accommodate high-moisture simulated flue gas. Bench-scale NOx/S02
removal tests were performed on the fluidized-bed reactor apparatus. An NO/SO2 span gas
mixture, nitrogen, and dry air were metered through rotameters to produce 12 scfh of a dry
simulated flue gas of 300 ppmv NOx, 600 ppmv S02, 8% 02, and the balance nitrogen. This gas
was preheated to reaction temperature (80 °C) and humidified with vaporized water to an
average 10.5 mole% water. The resulting wet simulated flue gas was passed through a vertical
reactor loaded with fluidized sorbent and sand; it was then passed through a filter to remove any
entrained particulate and to protect the downstream equipment. The reactor and filter assembly
were housed in an oven maintained at 80 °C. The test stand was equipped with a bypass of the
reactor and filter assembly to allow for bias checks. Sorbent was exposed to simulated flue gas
for 30 minutes. Water was removed from the spent flue gas with a NAFION™ Dryer. Dry gas
was then serially analyzed with S02 and NOx continuous emission monitors (CEMs).
Breakthrough curves from NOx and S02 analyzers were integrated to obtain uptake during the
30-minute exposure. Though NOx was introduced to the system as NO, the convention of
reporting in terms of N02 was adopted. Activated carbon could not be evaluated on this system
due to excessive carryover to the filter.
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RESULTS AND DISCUSSION
Effectiveness of Oxidant-Enriched Hydrated Lime Sorbents
Oxidants were screened by testing oxidant-enriched hydrated limes in duplicate for Hg° and SO2
removal in the fixed-bed reactor. Uptakes of Hg° (in (jg Hg°/g sorbent) and SO2 (in mg S02/g
sorbent) by these sorbents are illustrated in Figure 1. Despite a lower surface area, the C lime
exhibited the highest Hg° uptake (19.3 (Jg/g), followed by the M lime (10.4 jag/g). The other
oxidant-enriched hydrated limes did not show any improvement in Hg° uptake over the baseline,
hydrated lime (1.04 |ag/g). The pooled standard deviation of the replicates was 0.77 jag Hg°/g.
In terms of S02 uptake, C lime (20.6 mg/g) and M lime (16.6 mg/g) were not significantly
different from the baseline lime (15.2 mg/g). The pooled standard deviation of the SO2 uptake
was 1.8 mg S02/g. Hg° and S02 uptakes did not show any correlation to the physical parameters
(such as total surface area) of the sorbents, indicating that the generation of active sites
(oxidation sites) in certain oxidant-enriched hydrated limes (C and M limes) was instrumental in
the improvement in Hg° and S02 uptake.
Figure 1. Fixed-bed Hg° and SO? uptake by the oxidant-enriched hydrated limes at 80 °C. Flue
gas consisted of 40 ppbv Hg°, 4 mole% 02, 10 mole% C02, 1 mole% H20, and 500 ppmv S02.
25
Baseline S Lime N Lime M Lime C Lime
Lime
[~Hg Uptake; (jg Hgu/g bS02 Uptake; mg S02/g
Oxidants were also screened in oxidant-enriched hydrated lime sorbents for their ability to
enhance NOx removal in the fluidized-bed test stand. Screening results are shown in Figure 2.
A significant improvement in NOx removal was observed for C lime (3.4 mg N02/g) and M lime
(3.9 mg N02/g) compared to baseline lime (2.1 mg N02/g). Though the enhancement at test
conditions proved modest, the same additives effective for mercury control show promise with
respect to NOx activity. Duplicate testing of the baseline lime performance indicates a standard
deviation of 0.06 mg N02/g. No significant difference in S02 removal was observed between
baseline lime and C or M lime.
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Figure 2. Fluid-bed N0X and S02 uptake by oxidant-enriched hydrated limes at 80 °C. Flue gas
consisted of 300 ppmv NOx, 600 ppmv SO2, 8% O2, and 10.5% H2O.
1
«
1000
100
10
11111
Baseline S Lime N Lime M Lime C Lime
Lime
~ NOx Uptake; mg N02/g bS02 Uptake; mgS02/g
Effectiveness of Oxidant-Enriched Silicate Sorbents
The screening process identified two oxidants as effective in enhancing Hg° and NOx removal
from simulated flue gas with hydrated limes. The next step was to place these oxidants on a
Ca-based silicate sorbent with higher surface area. The Hg° and SO2 uptake of the
oxidant-enriched silicates was measured in duplicate on the fixed-bed reactor and compared to
those of the FGD activated carbon and a baseline silicate (no oxidant). As shown in Figure 3,
C silicate exhibited the highest Hg° uptake capacity (101 pg/g). Despite a much lower surface
area than FGD, C silicate exhibited Hg° removal indistinguishable from that of the FGD
activated carbon (95.5 pg/g). The pooled standard deviation of the Hg uptake was 7.5 (Jg/g. C
silicate also showed a far superior SO2 uptake capacity than the activated carbon (101 as
compared to 8.9 mg/g). C silicate is a superior multipollutant sorbent for Hg° and SO2 than the
activated carbon.
The oxidant-enriched silicates were also evaluated on the fluidized-bed test stand for NOx and
SO? removal. These results are summarized in Figure 4. Baseline silicate sorbent exhibited NOx
removal (7.0 mg N02/g) far superior to the baseline lime (1.6 mg NOa/g) evaluated in this block
of testing. The silicate sorbent is presumed to enhance an oxidation mechanism similar to that
proposed for mercury removal on similar sorbents. Addition of oxidants in C silicate and
M silicate further enhanced NOx removal with these silicate sorbents (14.0 and 15.7 mg N02/g,
respectively). Despite reduced alkali content of the silicate sorbents, SO2 removal has been
dramatically increased in the silicate sorbents, most notably in C silicate (176 mg/g) and
M silicate (177 mg/g), sorbents at conditions tested. Neither NOx nor S02 concentrations
returned to baseline prior to the end of the test for the silicate sorbents, indicating the sorbent was
not exhausted in these tests.
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Figure 3. Fixed-bed Hg and SO2 uptake by the oxidant-enriched calcium-silicate at 80 °C. Flue
gas consisted of 40 ppbv Hg°, 4 mo!e% O2, 10 mole% CO2, 1 mole% H20, and 500 ppmv S02.
r
160
d) 100
2C
BaseLine
Silicate
M Silicate
C Silicate
FGD
~ Hg Uptake; pg Hgu/g bS02 Uptake; mg S02/g
Figure 4. Fluid-bed NOx and S02 uptake by silicates at 80°C. Flue gas consisted of 300 ppmv
NOx, 600 ppmv S02, 8% 02, and 10.5% H20.
a>
to
1000
100
10
Baseline Lime Baseline M Silicate C Silicate
Silicate
~ NOx Uptake; mg N02/g bS02 Uptake; mg S02/g
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Cost Analysis
Approximately 75% of the existing coal-fired utility boilers in the U.S. are equipped only with
electrostatic precipitators (ESPs) for the control of PM. EPA's mercury control cost estimation
work considered this configuration as one of the 16 dry sorbent-based technology application
cases reflecting differences in flue gas cleaning equipment and type of coal burned. For this
configuration, EPA estimated the total annual cost for an 80% mercury control on a 100 MW
boiler with 65% capacity factor and flue gas mercury concentration of 10 pg/dscm at 1.79
mills/kWh.24 The cost of activated carbon sorbent used to derive the above estimated total
annual cost was $1.00/kg.
Excellent bench-scalc mercury removal was observed with sorbents other than activated carbon.
Therefore, it is of interest to estimate total annual cost for the mercury control system installed
on an identical boiler, as described above, but operated with sorbents other than activated carbon.
As previously discussed, C silicate Hg° removal performance was indistinguishable from that of
FGD activated carbon in bench-scale packed-bed tests. Therefore, it was assumed that 80%
mercury could be removed by injecting C silicate at the same sorbent-to-mercury ratio as used
before with activated carbon injection. The cost of C silicate was taken to be $0.20/kg of
sorbent. Calculations were performed using the same methodology used by EPA for a 100 MWe
boiler firing low-sulfur bituminous coal and with 65% capacity factor. Utilizing the above
assumptions, the total annual cost was estimated to be 0.36 mills/kWh for 80% mercury removal.
Substitution of C lime for activated carbon results in somewhat smaller, though still significant,
cost savings. Based on bench-scale removal, injection rates of C lime necessary to accomplish
mercury removal similar to that observed with activated carbon are estimated at 5 times the
injection rates of activated carbon. At an estimated cost of $0.13/kg, total annual cost of C lime
injection is estimated at 1.16 mills/kWh for the comparable 100 MWe unit requiring 80%
mercury removal.
In summary, the preliminary cost estimate described above indicated that approximately 80%
reduction of the total annual cost of mercury control could be possible when using C silicate in
lieu of activated carbon. Assuming sorbent injection was carried out for Hg control in the
presence of a relative abundance of SO2, injection of C silicate or similar Ca-bascd sorbent
would result in significant SO? removal, resulting in the generation of S02 emission credits.
Fluidized-bed reactor data suggest that, without optimizing for S02 or NOx removal, 0.17 tons of
SO2 may be removed per ton of C silicate. This SO2 emission credit could be sold or contribute
to operational flexibility of a plant. NOx reduction by such sorbents also has the potential to
provide direct economic benefit through the production of credits, if and when a NOx trading
system is implemented, but is likely to have a more immediate impact through increased
operational flexibility.
CONCLUSIONS
Multipollutant sorbents have been developed that can remove both Hg° and Hg+2 as effectively
as FGD activated carbon in fixed-bed simulations of coal-fired flue gas at 80 °C. Oxidant-
enriched calcium-based sorbents proved far superior to activated carbon with respect to SO2
9

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uptake on the same fixed-bed simulations. These oxidani-enriched, calcium-based sorbents also
performed better with respect to NOx and SO2 uptake than baseline lime hydrates for fixed and
fluid-bed simulations at 80 °C.
Preliminary economic analyses suggest that silicate sorbents with oxidants are 20% of the cost of
activated carbon for mercury removal, while oxidant-enriched lime hydrates offer reduced, but
significant savings. Credits for SO2 and NOx increase the savings for multipollutant sorbents
over activated carbon.
The apparent superiority of multipollutant lime and silicate hydrates enhanced with oxidants has
been confirmed at conditions typical of gas-cooled, sernidry absorption processes on coal-fired
boilers; performance of sorbents at higher-temperature conditions of duct sorbent injection
technologies remains to be evaluated. Planned field evaluations of both semidry absorption and
duct sorbent injection will allow better economic and performance comparisons of activated
carbon sorbents to that of oxidant-cnriched lime and silicate hydrates.
REFERENCES
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and Sea Trout of Various Ages." Science, 1973,181, 567-568.
2	Carpi, A. "Mercury from Combustion Sources: A Review of the Chemical Species Emitted and
Their Transport in the Atmosphere." Water, Air, Soil Pollut., 1997, 98, 241-254,
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of Reactive Gaseous Mercury in Ambient Air." Environ. Sci. Technol, 1998, 32(1), 49-57.
4	Engstrom, D. R.; Balogh, S. J.; Swain, E.B. "Evidence for historic increases in mercury
methylation from the sediments of 14 lakes in northeastern Minnesota," Proceedings of the Air
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5	Clarkson, T.W. Environ. Health Per sped, 1987, 74, 59-64.
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Goyer, R.A. "Toxic effects of metals, in Casarett and Doull's toxicology the basic science of
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NY, 1991.
9	Krishnan, S.V.; Gullett, B.K.; Jozewicz, W. "Sorption of Elemental Mercury by Activated
Carbons," Environ. Sci. Technol, 1994,25(8), 1506-1512.
10	Krishnan, S.V.; Gullett, B.K.; Jozewicz, W. "Mercury Control in Municipal Waste
Combustors and Coal-Fired Utilities," Environ. Prog., 1997,16(1), 47-53.
" Vidic, R. D.; McLaughlin, J. B. "Uptake of Elemental Mercury Vapors by Activated
Carbons." J. Air & Waste Manage. Assoc., 1996, 46, 241-250.
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12	Ghorishi, S.B.; Gullctt, B.K. "Sorption of Mercury Species by Activated Carbons and
Calcium-based Sorbents: Effect of Temperature, Mercury Concentration and Acid Gases," Waste
Manage. & Res., 1998, 76(6), 582-593.
13	Lancia, A.; Musmarra, D.; Pepe, F.; Volpicelli, G. "Adsorption of Mercuric Chloride Vapors
from Incinerator Flue Gases in Calcium Hydroxide Particles," Combust. Sci. Technol., 1993, 93,
277-289.
14	Lancia, A.; Musmarra, D.; Pepe, F.; Volpicelli, G. "Adsorption of Metallic Mercury on
Activated Carbon," Proceedings of the Twenty-Sixth Symposium (International) on Combustion,
The Combustion Institute, Pittsburgh, PA, 1996.
15	Srivastava, R.K.; Sedman, C.B.; Kilgroe, J.D. "Preliminary Performance and Cost Estimates
of Mercury Emission Control Options for Electric Utility Boilers," Proceedings of the 93rd Air &
Waste Management Association Annual Meeting, Salt Lake City, UT, June 18-22, 2000.
16	Richardson, C.; Blythe, G.; Rhudy, R.; Brown, T. "Enhanced Control of Mercury by Wet FGD
Systems," Proceedings of the 93rd Air and Waste Management Association Annual Conference
and Exhibition, Salt Lake City, UT, June 18-22, 2000.
17	Redinger, K.E. Babcock & Wilcox to William Maxwell, letter, U.S. EPA, Office of Air
Quality Planning and Standards, Durham, NC, November 7, 1996.
18	Federal Register Vol. 65, No. 245, December 20, 2000, 79825-79831.
19	Ghorishi, S.B.; Sedman, C.B. "Low Concentration Mercury Sorption Mechanisms and Control
by Calcium-based Sorbents: Application in Coal-fired Processes," J. Air & Waste Manage.
Assoc., 1998, 48, 1191-1198.
20	Ghorishi, S.B.; Singer, C.F.; Sedman, C.B. "Preparation and Evaluation of Modified Lime and
Silica-Lime Sorbents for Mercury Vapor Emissions Control," Proceedings of the 2nd
EPRI-DOE-EPA Combined Utility Air Pollutant Control Symposium, Atlanta, GA, 1999.
21	Jozewicz, W. "Program to Demonstrate ADVACATE Technology in Poland," Proceedings of
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Europe, Prague, Czech Republic, 1994, 661-669.
22	Jozewicz,W.; Rochelle, G.T.; Stroud, D.E. "Novel Techniques for the Enhanced Utilization of
Ca(OH)2 under Duct Injection Conditions," Proceedings of the Seventh Annual Coal
Preparation, Utilization, and Environmental Control Contractors' Conference, Pittsburgh, PA,
July 15-18, 1991,246-253.
23	Jozewicz,W.; Chang,J.C.S. "Evaluation of FGD Dry Injection Sorbents and Additives,
Volume I: Development of High Reactivity Sorbents," EPA-600/7-89-006a (NTIS PB 89-208
920), Air and Energy Engineering Research Laboratory, Research Triangle Park, NC, May 1989.
24	Srivastava, R.K.; Sedman, C.B.; Kilgroe, J.D. "Performance and Cost of Mercury Emission
Control Technology Applications on Electric Utility Boilers," EPA-600/R-00-083, National Risk
Management Research Laboratory, Research Triangle Park, NC, September 2000.
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KEY WORDS
Multipollutant Mercury
Sorbent
Emissions Control
Activated Carbon
Oxidant

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NnUDT DTD o co TECHNICAL REPORT DATA
IviVi ru - ri 1 -t ir ,jy O (Please read Instructions on the reverse before completin;
1. REPORT NO, 2.
EPA/600/A-01/064
3. R!
mm; u iiiiiiiiiKniiii sihihh
4. TITLE ANO SUBTITLE
Simultaneous Control of Hg , SC2. and NCX by Novel
Oxidized Calcium-based Sorbents
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. author(s) S. B. Ghorishi, C. F. Singer, andW.S. Joze-
wicz (A RCA D1S); and C. B. Sedman and R. K. Srivastav;;
(EPA)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND AODRESS
ARCAD1S Geraghty and Miller, Inc.
4915 Prospectus Drive
Durham, North Carolina 27713
10. PROGRAM ELEMENT NO.
11, CONTRACT/GRANT NO.
68-C-99201
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 PERIOD COVERED
Published paper; 10/99-1/01
14. SPONSORING AGENCY CODE
EPA/600/13
15.supplementary notes APPCD pr0ject officer is Charles B. Sedman, Mail Drop 04, 919/
541-7700. Presented at 94th Annual AWMA Meeting, Orlando, FL, 6/24-27/01.
is. abstract papcr gives results of an investigation of two classes of calcium (Ca)-
based sorbents (hydrated limes and silicate compounds), (NOTE: Efforts to develop
multipollutant control strategies have demonstrated that adding certain oxidants to
different classes of Ca-based sorbents significantly improves the removal of ele-
mental mercury vapor (Hgo), sulfur dioxide (S02), and nitrogen oxides (NOx) from
simulated flue gases.) A number of oxidizing additives were used at different con-
centrations in the Ca~based sorbent process. The Hgo, S02, and NOx capture cap-
acities of these oxidant-enriched sorbents were evaluated and compared to those of
a commercially available activated carbon in bench-scale, fixed-bed, and fluid-bed
systems, Ca-based sorbents prepared with two oxidants, designated C and P, ex-
hibited Hgo sorption capacities (about 100 /jg/g) comparable to that of the activated
carbon; they showed far superior SO2 and NCx sorption capacities., Preliminary
cost estimates for the process utilizing these novel sorbents indicate potential for
substantial lowering of control costs, compared to other processes currently used
or considered for control of Hgo, S02, and NOx emissions from coal-fired boilers.
The implications of these findings toward development of multipollutant control tech-
nologies are summarized.
17. KEY WORDS ANO DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/OPEN ended terms
c. cos ATI Field/Group
Pollution Flue Gases
Mercury (Metal) Calcium Oxides
Sulfur Dioxide Silicate Minerals
Nitrogen Oxides Activated Carbon
Sorbents Coal
Calcium Combustion
Pollution Control
Stationary Sources
13B 21B
07B
QBG
11G 2 ID
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
12
20. SECURITY CLASS (This page)
Unclassified
22, PRICE
EPA Form 2220-1 (9-73)

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