Abstract Booklet 2006 - Swanson School of Engineering - University ...

environment is of practical value. In this work, the adsorption of aqueous Hg 2+ (200-
400 ppm) and Pb 2+ (570 ppm) onto a series of activated carbons was investigated. The
activated carbons used were prepared from high sulfur coal or petroleum coke via
chemical activation processes using alkaline materials such as KOH and its mixture
with other reagents. Activated carbons were analyzed for specific surface area, porous
size distribution, total sulfur, as well as sulfur functional groups. The adsorption
capacity was determined at controlled pH (5.0~6.0) and temperature (20-60°C) using
ICP and AAS. The activated carbons had total sulfur contents from 0.16 to 20.14 wt%,
and their specific surface areas varied from 47 to 2232 m 2 /g. A pseudo first order
model was applied to describe the adsorption kinetics. Experimental data indicated that
the increase in sulfur content and specific surface area enlarged the adsorption rate and
capacity for both Hg(II) and Pb(II). The type of sulfur in activated carbons was found
to be the most important factor in determining the effectiveness of adsorbing Hg(II)
and Pb(II).
40-3
Novel Sorbents for Removal of Mercury from Flue Gas
Evan Granite, Albert A. Presto, DOE/NETL, USA
Numerous materials have been examined as sorbents for the capture of mercury in a
lab-scale packed-bed reactor located at NETL. The sorbents examined include
activated carbons, Thief carbons, precious metals, fly ash, metal oxides, and metal
sulfides. Simulated flue gases containing sulfur dioxide, nitrogen oxide, oxygen,
carbon dioxide, elemental mercury, and nitrogen were contacted with the sorbents in
the lab-scale packed-bed reactor. Several promising sorbent candidates have been
identified. The mechanisms of mercury capture are discussed. Future research on
sorbents will be conducted in a bench-scale packed-bed reactor employing both
simulated and real flue gas streams generated on-site at NETL.
40-4
Impacts on Trace Metal Leaching from Fly Ash Due to the
Co-Combustion of Switchgrass with Coal
Wayne Seames, Mandar Gadgil, Chunmei Wang, Joshua Fetsch, University of North
Dakota, USA
Biomass/coal blended fuel combustion is gaining popularity as a means to reduce
greenhouse gas emissions. The impact of co-combustion upon the solubility of trace
metals contained in the various fly ash regimes has yet to be addressed. In this study,
Blacksville coal/switch grass blended fuel is combusted in a 19kW laboratory
combustor and sampled using a low pressure impactor. Leaching tests of the three
particle regimes – submicron, fine fragmentation, and bulk ash – were performed. A
modified TCLP-type leaching method was utilized with acidic, neutral, and basic
solvents and the relative solubility of arsenic, selenium, and antimony were determined
as a function of solvent and particle regime. The results were then compared to
comparable results obtained from the combustion of Blacksville coal alone. The results
suggest that co-combustion may have beneficial effects by lowering the solubility of
arsenic, antimony, and to a lesser extent selenium, contained on the surface of
submicron and fine fragmentation particles into acid and basic solutions. By contrast,
the potential to leach these trace elements from bulk ash collected in disposal piles
increases.
40-5
Effect of Hydrogen Chloride in Coal Combustion Flue Gas on the Mercury
Removal Performance of Activated Carbon from Coal Combustion Flue Gas
Toru Yamada, Yuki Yamaji, Eiji Sasaoka, Md. Azhar Uddin, Shengji Wu, Okayama
University, JAPAN
In this study, the effect of HCl on the Hg 0 removal performance for coal combustion
flue gas system using activated carbons prepared from fly ash and pitch and activated
carbon derived from coconut shell (a commercial sample) was investigated. Mercury
(Hg 0 ) removal capacity of fly ash-pitch activated carbon was higher than that of
coconut shell activated carbon in the absence of HCl, however fly ash-pitch activated
carbon showed lower mercury adsorption performance compared to the coconut shell
activated carbon in the presence of HCl. It is suggest that in the absence of HCl,
surface H 2 SO4 was produced by the adsorption of SO 2 , O 2 and H 2 O on the activated
carbon which then reacted with Hg 0 to produce HgSO 4 and enhanced the mercury
adsorption capacity of the activated carbons. The presence of HCl in the feed gas
increased the Hg 0 removal performance of the activated carbon sorbents many fold.
However, the presence of SO 2 has an adverse effect on the adsorption capacity of the
activated carbons in the presence of HCl.
SESSION 41
COAL UTILIZATION BY-PRODUCTS – 1
41-1
Overview of C2P2, the Industrial Resources Council, and
the Green Highways Initiative
David Goss, American Coal Ash Association, USA; Mark Bryant, AmerenEnergy,
USA
The use of coal combustion products (CCPs) in a wide variety of applications allows
for the use, reuse and recycling of nearly 50 million tons annually of these materials.
As new emission control systems are added to coal fueled power plants, there are new
challenges facing producers and markets of CCPs. The formation of private and public
sector partnerships is having a positive impact on developing new markets for CCPs
and in increasing the awareness of the value of these products to potential end-users
and specifiers. The Coal Combustion Products Partnership (C2P2), the Industrial
Resources Council and the Green Highways Initiative all are providing information
and outreach to those whose decisions could increase the beneficial use of these
materials. This paper will provide an overview of these partnerships and the results of
their efforts.
41-2
Beneficial Land Application Uses of FGD Products
Warren Dick, David A. Kost, Liming Chen, The Ohio State University, USA
Combustion of fossil fuels for energy production releases sulfur dioxide (SO 2 ) at a rate
proportional to the S concentration in the fuel. Industrialized nations have adopted flue
gas desulfurization (FGD) technologies to reduce SO 2 emissions. FGD technologies
will generate increased amounts of product in the future as more utilities install
scrubbers for SO 2 control. These FGD products raise economic and environmental
issues for which satisfactory solutions still need to be found. The type of coal and
desulfurization process used influences the chemical composition and properties of an
FGD product. The properties of the FGD material have a direct impact on potential
land application uses. FGD properties most commonly captured for beneficial purposes
are (1) ability to neutralize acid, (2) high amounts of soluble calcium and sulfate, (3)
source of plant nutrients, and (4) uniform particle size. Land application uses of FGD
materials are identified by matching the properties of the FGD material with
improvement in some ecosystem function (or functions). For beneficial use, the change
in ecosystem function is assumed to be positive. FGD use must be considered in terms
of recommended application rates, environmental impact and economic return.
Beneficial land application implies the applied FGD material will improve the soil
(primarily) and also the total environment. Often, the intended benefit relates to plant
growth, but there may be other benefits to soil or water such as reduction of erosion,
improved quality of runoff and/or leachate water, or improved internal drainage. The
application rate must be sufficient to cause soil improvement, but not so great as to
constitute disposal of the FGD material. Although there is recognition of the potential
of using FGD materials in agriculture, there is also uncertainty whether this use is
sustainable. Currently, there is a general lack of acceptance in the agricultural
community for using FGD materials. This barrier can only be overcome by research
and sound knowledge that sometimes already exists in the scientific and technical
literature. To promote use of FGD products, especially FGD gypsum, a national
network of agricultural demonstration and research sites has been established. Network
sites, strategically located in the United States, are available to producers, users and
marketers of FGD products to provide places where observations can be made as to the
benefits of FGD product use under regional agricultural conditions. In addition, data on
crop yields, environmental impacts and economic benefits will aid in the marketing of
the FGD products.
41-3
On the Behavior of Coal Combustion By-Products (CCP) under
Different Geotechnical and Geoenvironmental Stress Conditions
Vincent (Tobi) Ogunro, Mutiu Ayoola, Hilary Inyang, Brian Anderson, John Daniels,
University of North Carolina, USA
Environmental and economic concerns regarding management of coal combustion
products (referred to as Recycled Granular waste Media, RGWMs, in this study) have
led to several investigations into potential contaminant releases from RGWMs used as
substitute materials in construction of geotechnical and geoenvironmental
infrastructures. Most of these studies understandably have been focus on assessing the
leaching potential of RGWMs. The results of these studies have provided only limited
data on the behavior of RGWMs compared with conventional construction materials.
In order to provide further insight into the engineering behavior and leaching potentials
of RGWMs especially under unusual stress conditions, series of drained and undrained
triaxial compression tests are performed. It was observed that RGWMs exhibit
significantly different behavior compared with sand subjected to the same stress
condition. This include significant volumetric contraction of specimen compacted at
95% maximum unit weight, deviation from Rowe’s dilatancy theory and steady state
concept, static liquefaction of medium dense specimen at low confining stresses,
significant loading rate sensitivity and pseudo-viscoelastoplastic behavior within some
strain rate regimes. Also, stress-dependent contaminant releases from fresh and aged
RGWM are being investigated.
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