Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SORBENT BODIES COMPRISING ACTIVATED CARBON,
PROCESSES FOR MAKING THEM, AND THEIR USE
[0001] This application claims the benefit of priority to U.S. application no.
11/977,843,
filed on October 26, 2007, and to U.S. provisional application no. 60/966,558,
filed on May
14, 2007.
FIELD OF THE DISCLOSURE
[0002] This disclosure relates to sorbent bodies comprising activated carbon,
processes
for making them, and methods of using them. The sorbent bodies can be used to
remove
toxic elements from a fluid, such as from a gas stream. For instance, the
sorbent bodies may
be used to remove elemental mercury or mercury in an oxidized state from a
coal combustion
flue gas.
BACKGROUND
[0003] Emissions of toxins into the atmosphere have become environmental
issues of
increasing concern because of the dangers posed to human health. For instance,
coal-fired
power plants and medical waste incineration are major sources of human
activity related
mercury emissions. Mercury emitted to the atmosphere can travel thousands of
miles before
being deposited to the earth. Studies also show that mercury from the
atmosphere can also be
deposited in areas near the emission source.
[0004] It is estimated that there are 48 tons of mercury emitted from coal-
fired power
plants in the United States annually. One DOE-Energy Information
Administration annual
energy outlook projected that coal consumption for electricity generation will
increase from
976 million tons in 2002 to 1,477 million tons in 2025 as the utilization of
coal-fired
generation capacity increases. However, mercury emission control regulations
have not been
rigorously enforced for coal-fired power plants. A major reason is a lack of
effective control
technologies available at a reasonable cost, especially for elemental mercury
control.
[0005] One technology that has been used for controlling elemental mercury, as
well as
for oxidized mercury, is activated carbon injection (ACI). The ACI process
includes
injecting activated carbon powder into the flue gas stream and using a fabric
fiber or
electrostatic precipitator to collect the activated carbon powder that has
adsorbed mercury.
Generally, ACI technologies require a high carbon to mercury ratio to achieve
the desired
mercury removal level (> 90%), which results in a high cost for sorbent
material. The high
carbon to mercury ratio suggests that ACI does not utilize the mercury
sorption capacity of
carbon powder efficiently. Additionally, if only one particle collection
system is used, the
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commercial value of fly ash is sacrificed due to its mixing with contaminated
activated
carbon powder. A system with two separate powder collectors and injecting
activated carbon
sorbent between the first collector for fly ash and the second collector, or a
baghouse, for
activated carbon powder, may be used. A baghouse with high collection
efficiency may be
installed in the power plant facilities. However, these measures are costly
and may be
impractical, especially for small power plants.
[0006] Since water-soluble (oxidized) mercury is the main mercury species in
bituminous coal flue gas with high concentrations of SO2 and HCI, bituminous
coal-fired
plants may be able to remove 90% mercury using a wet scrubber combined with
NO, and/or
SO2 control technologies. Mercury emission control can also be achieved as a
co-benefit of
particulate emission control. Chelating agents may be added to a wet scrubber
to sequestrate
the mercury from emitting again. A chelating agent adds to the cost due to the
problems of
corrosion of the metal scrubber equipment and treatment of chelating solution.
Elemental
mercury is the dominant mercury species in the flue gas of sub-bituminous coal
or lignite
coal, and a wet scrubber is not effective for removal of elemental mercury
unless additional
chemicals are added to the system. It is undesirable, however, to add
additional potentially
environmentally hazardous material into the flue gas system.
[0007] Certain industrial gases, such as syngas and combustion flue gas, may
contain
toxic elements such as cadmium, chromium, lead, barium, beryllium, nickel,
cobalt,
vanadium, zinc, copper, manganese, antimony, silver, thallium, arsenic or
selenium, in
addition to mercury. Like mercury, these toxic elements may exist in elemental
form or in a
chemical compound comprising the element. It is highly desired that the
presence of one or
more of these toxic elements be substantially reduced before a syngas is
supplied for
industrial and/or residential use or before a gas is emitted to the
atmosphere.
[0008] There is a genuine need of a sorbent material capable of removing
mercury
and/or other toxic elements from fluids such as flue gas and syngas, with a
higher capacity
than activated carbon powder alone. It is also desired that such sorbent
material be produced
at a reasonable cost and conveniently used.
SUMMARY
[0009] Embodiments of the invention relate to sorbent bodies comprising
activated
carbon, processes for making them, and methods of using them. The sorbent
bodies can be
used to remove toxic elements from a fluid, such as from a gas stream. For
instance, the
sorbent bodies may be used to remove elemental mercury or mercury in an
oxidized state
from a coal combustion flue gas.
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[0010] Embodiments of the invention have one or more of the following
advantages.
Sorbent bodies of the invention comprising activated carbon having high
specific surface area
and a large number of active sites capable of sorbing or promoting sorption of
a toxic element
can be produced and used effectively for the sorption of toxic elements,
including arsenic,
cadmium, mercury and selenium. The sorbent bodies of certain embodiments of
the
invention are effective for sorption of not just oxidized mercury, but also
elemental mercury.
Further, the sorbent bodies according to certain embodiments of the invention
are effective in
removing mercury from flue gases with high and low concentrations of HCl
alike. Sorbent
bodies according to certain embodiments of the invention are also effective in
removing
mercury from flue gases with high concentration of SO3.
[0011] Additional features and advantages will be set forth in the detailed
description
which follows, and in part will be readily apparent to those skilled in the
art from the
description or recognized by practicing the invention as described in the
written description
and claims hereof, as well as the appended drawings.
[0012] The foregoing general description and the following detailed
description are
merely exemplary of the invention, and are intended to provide an overview or
framework to
understanding the nature and character of the invention as it is claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
100131 The accompanying drawings are included to provide a further
understanding of
the invention, and are incorporated in and constitute a part of this
specification.
[0014] FIG. 1 is a diagram comparing the mercury removal capability of a
tested sample
of a sorbent comprising an in-situ extruded metal catalyst according to the
invention and a
sorbent which comprises impregnated metal but no in-situ extruded metal
catalyst over time.
[0015] FIG. 2 is a diagram showing the inlet mercury concentration (CHgO) and
outlet
mercury concentration (CHg1) of a sorbent body according to one embodiment of
the
invention at various inlet mercury concentrations.
[0016] FIG. 3 is an SEM image of part of a cross-section of a sorbent body
according to
one embodiment of the invention comprising in-situ extruded metal catalyst.
[0017] FIG. 4 is an SEM image of part of a cross-section of a comparative
sorbent body
comprising post-activation impregnated metal catalyst.
DETAILED DESCRIPTION
[0018] Unless otherwise indicated, all numbers such as those expressing weight
percents
of ingredients, dimensions, and values for certain physical properties used in
the specification
and claims are to be understood as being modified in all instances by the term
"about." It
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should also be understood that the precise numerical values used in the
specification and
claims form additional embodiments of the invention. Efforts have been made to
ensure the
accuracy of the numerical values disclosed in the Examples. Any measured
numerical value,
however, can inherently contain certain errors resulting from the standard
deviation found in
its respective measuring technique.
[0019] As used herein the use of the indefinite article "a" or "an" means "at
least one,"
and should not be limited to "only one" unless explicitly indicated to the
contrary. Thus, for
example, reference to "a metal catalyst" includes embodiments having one, two
or more
metal catalysts, unless the context clearly indicates otherwise.
[0020] As used herein, a "wt%" or "weight percent" or "percent by weight" of a
component, unless specifically stated to the contrary, is based on the total
weight of the
composition or article in which the component is included. As used herein, all
percentages
are by weight unless indicated otherwise. All ppm with respect to gases are by
volume unless
indicated otherwise.
[0021] The term "sulfur" as used herein includes sulfur element at all
oxidation states,
including, inter alia, elemental sulfur (0), sulfate (+6), sulfite (+4), and
sulfide (-2). The term
sulfur thus includes sulfur in any oxidation state, as elemental sulfur or in
a chemical
compound or moiety comprising sulfur. The weight percent of sulfur is
calculated on the
basis of elemental sulfur, with any sulfur in other states converted to
elemental state for the
purpose of calculation of the total amount of sulfur in the material.
[0022] The term "metal catalyst" includes any metal element in any oxidation
state, as
elemental metal or in a chemical compound or moiety comprising the metal,
which is in a
form that promotes the removal of a toxic element (such as cadmium, mercury,
chromium,
lead, barium, beryllium, nickel, cobalt, vanadium, zinc, copper, manganese,
antimony, silver,
thallium, arsenic or selenium, or such as cadmium, mercury, arsenic or
selenium) from a fluid
in contact with a sorbent body of the invention. Metal elements can include
alkali metals,
alkaline earth metals, transition metals, rare earth metals (including
lanthanoids), and other
metals such as aluminum, gallium, indium, tin, lead, thallium and bismuth.
[0023] The weight percent of metal catalyst is calculated on the basis of
elemental metal,
with any metal in other states converted to elemental state for the purpose of
calculation of
the total amount of metal catalyst in the material. Metal elements present in
an inert from,
such as in an inorganic filler compound, are not considered metal catalysts
and do not
contribute to the weight percent of a metal catalyst. The amount of sulfur or
metal catalyst
may be determined using any appropriate analytical technique, such as mass
spectroscopy.
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[0024] By "in-situ extruded" is meant that the relevant material, such as
sulfur and/or
metal catalyst, is introduced into the material by incorporating at least part
of the source
material thereof into the batch mixture material, such that the formed body
comprises the
source materials incorporated therein.
[0025] Distribution of sulfur, metal catalyst or other materials across a
cross-section of
the sorbent body, or an extrusion batch mixture body, or a batch mixture
material of the
invention can be measured by various techniques, including, but not limited
to, microprobe,
XPS (X-ray photoelectron spectroscopy), and laser ablation combined with mass
spectroscopy.
[0026] The methodology of characterizing the distribution of a certain
material (e.g.,
sulfur, metal catalyst, and the like) in a certain planar cross-section of a
sorbent body, or
other body, is described as follows. This methodology is referred to as
"Distribution
Characterization Method."
[0027] Target test areas of the cross-section of at least 500 m x 500 m size
are chosen if
the total cross-section is larger than 500 .m x 500 m. The full cross-
section, if less than or
equal to 500 m x 500 m, would be a single target test area. The total number
of target test
areas is p (a positive integer).
[0028] Each target test area is divided by a grid into multiple separate 20 m
x 20 m
zones. Only zones having an effective area (defined below) not less than 40
mz are
considered and those having an effective area lower than 40 m2 are discarded
in the data
processing below. Thus the total effective area (ATE) of all the square sample
zones of the
target test area is:
n
ATE ae(i),
where ae(i) is the effective area of zone i, and n is the total number of the
square sample
zones in the target test area, where ae(i) > 40 m2. Area of individual square
zone ae(i) in
square micrometers is calculated as follows:
ae(i) = 400 - av(i)
where av(i) is the total area in square micrometers of any voids, pores or
free space larger
than 10 m2 within square zone i.
[0029] Each square zone i is measured to have an average concentration C(i),
expressed
in terms of moles of sulfur atoms per unit effective area for sulfur, or moles
of other relevant
material in the case of a metal catalyst. All C(i) (i=1 to n) are then listed
in descending order
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to form a permutation CON(1), CON(2), CON(3), ... CON(n), where CON(1) is the
highest
C(i) among all n zones, and CON(n) is the lowest C(i) among all n zones. The
arithmetic
average concentration of the 5% of all n zones in the target test area having
the highest
concentrations is CON(max). Thus:
INT(0.05xn)
YCON(m)
CON(max) = INT(O.05 x n)
where INT(0.05xn) is the smallest integer larger than or equal to 0.05xn. As
used herein, the
operator "INT(X)" yields the smallest integer larger than or equal to X.
[0030] The arithmetic average concentration of the 5% of all n zones in the
target test
area having the lowest concentrations is CON(min). Thus:
n
ECON(m)
CON(min) = "' 1lvr(o.95Xn)
n - INT(0.95 x n)
[0031] The arithmetic average concentration of the target test area is
CON(av). Thus:
n
ECON(m)
CON(av) = `
n
[0032] For all p target test areas, all CON(av)(k) (k=1 to p) are then listed
in descending
order to form a permutation CONAV(1), CONAV(2), CONAV(3), ... CONAV(p), where
CONAV(1) is the highest CON(av)(k) among all p target test areas, and CONAV(p)
is the
lowest CON(av)(p) among all p target test areas. The arithmetic average
concentration of all
p target test areas is CONAV(av). Thus:
P
ICONAV(k)
CONA V(av) = k-'
p
[0033] In certain embodiments of the bodies or materials according to the
invention,
where the relevant material is distributed throughout the body, or the
activated carbon matrix,
or the material, it is desired that: in each target test area, the
distribution thereof has the
following feature: CON(av)/CON(min) < 30, and CON(max)/CON(av) < 30. In
certain other
embodiments, it is desired that CON(av)/CON(min) < 20, and CON(max)/CON(av) <
20. In
certain other embodiments, it is desired that CON(av)/CON(min) < 15, and
CON(max)/CON(av) < 15. In certain other embodiments, it is desired that
CON(av)/CON(min) < 10, and CON(max)/CON(av) < 10. In certain other
embodiments, it is
desired that CON(av)/CON(min) < 5, and CON(max)/CON(av) < 5. In certain other
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embodiments, it is desired that CON(av)/CON(min) < 3, and CON(max)/CON(av) <
3. In
certain other embodiments, it is desired that CON(av)/CON(min) < 2, and
CON(max)/CON(av) < 2.
[0034] For a certain material or component to be "homogeneously distributed"
to have a
"homogeneous distribution" in a body or a material according to the present
application, the
distribution thereof according to the Distribution Characterization Method
satisfies the
following: in each target test area, for all CON(m) where 0.1 n< m< 0.9n: 0.5
<
CON(m)/CON(av) < 2.
[0035] In certain embodiments, it is desired that 0.6 < CON(m)/CON(av) < 1.7.
In
certain other embodiments, it is desired that 0.7 < CON(m)/CON(av) < 1.4. In
certain other
embodiments, it is desired that 0.8 < CON(m)/CON(av) < 1.2. In certain other
embodiments,
it is desired that 0.9 < CON(m)/CON(av) < 1.1. In certain embodiments, for all
CON(m)
where 0.05n < m< 0.95n: 0.5 < CON(m)/CON(av) < 2; in certain embodiments, 0.6
<
CON(m)/CON(av) < 1.7. In certain other embodiments, it is desired that 0.7 <
CON(m)/CON(av) < 1.4. In certain other embodiments, it is desired that 0.8 <
CON(m)/CON(av) < 1.2. In certain other embodiments, it is desired that 0.9 <
CON(m)/CON(av) < 1.1. In certain embodiments of the invention (sorbent body,
extrusion
mixture body, and the like) and material of the invention, in addition to any
one of the
features stated above in this paragraph with respect to each individual target
test area, the
distribution of the relevant material (e.g., sulfur, metal catalyst, and the
like) with respect to
all p target test areas has the following feature: for all CONAV(k) where 0.1
p< k< 0.9p: 0.5
< CONAV(k)/CONAV(av) < 2; in certain embodiments, 0.6 < CONAV(k)/CONAV(av) <
1.7. In certain other embodiments, it is desired that 0.7 < CONAV(k)/CONAV(av)
< 1.4. In
certain other embodiments, it is desired that 0.8 < CONAV(k)/CONAV(av) < 1.2.
In certain
other embodiments, it is desired that 0.9 < CONAV(k)/CONAV(av) < 1.1. In
certain other
embodiments, it is desired that 0.95 < CONAV(k)/CONAV(av) < 1.05. In certain
embodiments, for all CONAV(k) where 0.05p < k< 0.95p: 0.5 < CONAV(k)/CONAV(av)
<
2; in certain embodiments, 0:6 < CONAV(k)/CONAV(av) < 1.7. In certain other
embodiments, it is desired that 0.7 < CONAV(k)/CONAV(av) < 1.4. In certain
other
embodiments, it is desired that 0.8 < CONAV(k)/CONAV(av) < 1.2. In certain
other
embodiments, it is desired that 0.9 < CONAV(k)/CONAV(av) < 1.1. In certain
other
embodiments, it is desired that 0.95 < CONAV(k)/CONAV(av) < 1.05.
[0036] One aspect of the invention is a sorbent body comprising:
an activated carbon matrix;
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sulfur, in any oxidation state, as elemental sulfur or in a chemical compound
or
moiety comprising sulfur; and
a metal catalyst, in any oxidation state, as elemental metal or in a chemical
compound
or moiety comprising the metal;
wherein the metal catalyst is distributed throughout the activated carbon
matrix.
[0037] In this and any other embodiments of sorbent bodies the invention,
sulfur may be
distributed throughout the activated carbon matrix. In some embodiments, the
metal catalyst
and/or sulfur is essentially homogeneously distributed throughout the
activated carbon
matrix. In some embodiments, at least a portion of the metal catalyst is
chemically bound to
at least a portion of the sulfur. Thus, one compound comprising a metal
catalyst and sulfur,
such as a metal sulfide, may provide both the sulfur and metal catalyst in the
sorbent body.
The phrase "at least a portion" of sulfur or metal catalyst refers to some or
all of the sulfur or
metal catalyst content in the sorbent body. In some further embodiments, at
least a portion of
sulfur is chemically bound to at least a portion of carbon in the activated
carbon matrix.
[0038] In this and any other embodiments of sorbent bodies the invention, at
least a
portion of the sulfur, of the metal catalyst, or of both the sulfur and metal
catalyst, is in a state
capable of chemically bonding with cadmium, mercury, chromium, lead, barium,
beryllium,
nickel, cobalt, vanadium, zinc, copper, manganese, antimony, silver, thallium,
arsenic or
selenium. For instance, at least a portion of the sulfur can be in a state
capable of chemically
bonding with mercury.
[0039] The sorbent bodies of this and other embodiments described herein may,
for
example, be adapted for removing mercury and other toxic elements from a fluid
stream such
as a flue gas stream resulting from coal combustion or waste incineration or
syngas produced
during a coal gasification process. Such gas streams can contain various
amounts of mercury
and/or other toxic elements such as cadmium, chromium, lead, barium,
beryllium, nickel,
cobalt, vanadium, zinc, copper, manganese, antimony, silver, thallium, arsenic
and selenium.
Any toxic element, such as mercury, can be present in elemental state or
oxidized state at
various proportions in such gas streams depending on the source material
(e.g., bituminous
coal, sub-bituminous coal, municipal waste, and medical waste) and process
conditions. In
some embodiments, the sorbent body comprises a metal catalyst adapted for
promoting the
removal of arsenic, cadmium, mercury and/or selenium from a fluid stream to be
treated.
[0040] It is believed that, by a combination of a physical and chemical
sorption, the
sorbent bodies of the invention are capable of binding and trapping mercury
and other toxic
elements both at elemental state and oxidized state. The sorbent bodies and
material of
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certain embodiments of the invention are particularly effective for removing
mercury at
elemental state in a flue gas stream. This is particularly advantageous
compared to certain
other technology that is usually less effective in removing elemental mercury.
[0041] The sorbent bodies of the invention may take various shapes. For
example, the
sorbent body may be a powder, pellets, and/or extruded monolith. The sorbent
bodies of the
invention may be incorporated in a fixed sorbent bed through which a fluid
stream to be
treated may flow. In certain embodiments, especially when used in treating the
coal
combustion flue gas in power plants or the syngas produced in coal
gasification processes, it
is highly desired that any fixed bed through which the gas stream passes has a
low pressure-
drop. To that end, it is desired that sorbent pellets packed in the fixed bed
allow for sufficient
gas passageways.
[0042] According to certain embodiments, the sorbent body is in the form of a
monolith.
According to certain embodiments, the sorbent body is in the form of a
monolithic
honeycomb with a plurality of channels through which gas or liquid may pass.
[0043] In certain embodiments, it is particularly advantageous that the
sorbent body of
the invention is in the form of extruded monolithic honeycomb having multiple
channels.
Cell density of the honeycomb can be adjusted during the extrusion process to
achieve
various degree of pressure-drop when in use. Cell density of the honeycomb can
range from
25 to 500 cells-inch-2 (3.88 to 77.5 cells=cm 2) in certain embodiments, from
50 to 200
cells=inch"2 (7.75 to 31.0 cells=cm 2) in certain other embodiments, and from
50 to 100
cells=inch"2 (7.75 to 15.5 cells=cm 2) in certain other embodiments. In
certain embodiments,
the thickness of the cell walls ranges from 1 mil to 50 mil, for example from
10 mil to 30 mil.
To allow for a more intimate contact between the gas stream and the sorbent
body material, it
is desired in certain embodiments that part of the channels are plugged at one
end of the
sorbent body, and part of the channels are plugged at the other end of the
sorbent body. In
certain embodiments, it is desired that at each end of the sorbent body, the
plugged and/or
unplugged channels form a checkerboard pattern. In certain embodiments, it is
desired that
where one channel is plugged on one end (referred to as "the reference end")
but not the
opposite end of the sorbent body, at least a majority of the channels
(preferably all in certain
other embodiments) immediately proximate thereto (those sharing at least one
wall with the
channel of concern) are plugged at the other end of the sorbent body but not
on the reference
end. Multiple honeycombs can be stacked in various manners to form actual
sorbent beds
having various sizes, service duration, and the like, to meet the needs of
differing use
conditions.
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[0044] The "activated carbon matrix," as used herein, means a network formed
by
interconnected carbon atoms and/or particles. In some embodiments, the
activated carbon
matrix in the sorbent bodies of the invention is in the form of an
uninterrupted and continuous
body. As is typical for activated carbon materials, the matrix comprises wall
structure
defining a plurality of pores. The activated carbon matrix, along with sulfur
and the metal
catalyst, can provide the backbone structure of the sorbent body. In addition,
the large
cumulative areas of the pores in the activated carbon matrix provide a
plurality of sites where
mercury sorption can occur directly, or where sulfur and the metal catalyst
can be distributed,
which further promote mercury sorption. It is to be noted that the pores
defined by the
activated carbon matrix can be different from the pores actually present in
the sorbent body.
For example, a portion of the pores defined by the activated carbon matrix may
be filled by a
metal catalyst, sulfur, an inorganic filler, and combinations and mixtures
thereof.
[0045] In certain embodiments, the sorbent body comprises from 50% to 97% by
weight
of activated carbon, in certain embodiments from 60% to 97% or from 85% to
97%. In other
embodiments, the sorbent body comprises at least 50% by weight of activated
carbon, for
example at least 60% by weight, at least 70 % by weight, at least 80% by
weight, at least 90%
by weight, at least 95% by weight, or at least 97% by weight of activated
carbon. Higher
concentrations of activated carbon usually lead to higher porosity if the same
level of
carbonization and activation were used during the process of making the
sorbent body when
made according to the processes described herein.
[0046] The pores defined by the activated carbon matrix can be divided into
two
categories: nanoscale pores having a diameter of less than or equal to 10 nm,
and microscale
pores having a diameter of higher than 10 nm. According to certain
embodiments, the
activated carbon matrix defines a plurality of nanoscale pores. The metal
catalyst or sulfur
may, for example, be present on the wall surface of at least part of the
nanoscale pores.
According to certain embodiments, the activated carbon matrix further defines
a plurality of
microscale pores.
[0047] Pore size and distribution thereof in the sorbent bodies can be
measured by using
techniques available in the art, such as, e.g., nitrogen adsorption. Both the
surfaces of the
nanoscale pores and the microscale pores together provide the overall high
specific area of
the sorbent body of the invention. In certain embodiments, the wall surfaces
of the nanoscale
pores constitute at least 50%, at least 60%, at least 70%, at least 80%, or at
least 90% of the
specific area of the sorbent body.
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[0048] The sorbent bodies of the invention may have large specific surface
areas. In
certain embodiments of the invention, the sorbent bodies have specific areas
ranging from 50
to 2000 m2=g 1, 200 to 2000 m2=g 1, 400 to 1500 m2=g ', 100 to 1800 m2=g I ,
200 to 1500 m2=g , ,
or 300 to 1200 m2=g"l. Higher specific area of the sorbent body can provide
more active sites
in the material for the sorption of toxic elements. However, if the specific
area of the sorbent
body is quite high, e.g., higher than 2000 m2=g ', the sorbent body becomes
quite porous and
the mechanical integrity of the sorbent body may suffer. This could be
undesirable for
certain applications where the strength of the sorbent body may need to meet
certain
threshold requirements.
[0049] The metal catalyst included within embodiments of the invention may
promote
the removal of one or more toxic elements such as cadmium, mercury, chromium,
lead,
barium, beryllium, nickel, cobalt, vanadium, zinc, copper, manganese,
antimony, silver,
thallium, arsenic or selenium from a fluid in contact with the sorbent body,
any of which may
be in any oxidation state and may be in elemental form or in a chemical
compound
comprising the element. Any such metal catalyst capable of promoting the
removal of toxic
elements or compounds (also referred to herein as "abatement" of toxic
elements or
compounds), including mercury, arsenic, cadmium or selenium, from a fluid,
such as a fluid
stream to be treated upon contacting, can be included in the sorbent body of
the invention.
The terms "removal" and "abatement" in this context are used interchangeably
herein.
Furthermore, those terms would be understood as covering reducing the presence
of the toxic
elements by a matter of degree in a fluid, i.e. by a certain percentage, and
are not limited to
complete removal or abatement of the toxic elements. In some embodiments, the
metal
catalyst can function in one or more of the following ways to promote the
removal (or
abatement) of toxic elements from a fluid in contact with the sorbent body:
(i) temporary or
permanent chemical sorption (e.g., via covalent and/or ionic bonds) of a toxic
element; (ii)
temporary or permanent physical sorption of a toxic element; (iii) catalyzing
the
reaction/sorption of a toxic element with other components of the sorbent
body; (iv)
catalyzing the reaction of a toxic element with the ambient atmosphere to
convert it from one
form to another; (v) trapping a toxic element already sorbed by other
components of the
sorbent body; and (vi) facilitating the transfer of a toxic element to the
active sorbing sites.
[0050] According to certain embodiments of the sorbent body of the invention,
the metal
catalyst is provided in a form selected from: (i) halides and oxides of alkali
and alkaline
earth metals; (ii) precious metals and compounds thereof; (iii) oxides,
sulfides, and salts of
vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, niobium,
molybdenum,
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silver, tungsten and lanthanoids; and (iv) combinations and mixtures of two or
more of (i), (ii)
and (iii).
[0051] For instance, the metal catalyst may be provided in a form selected
from: (i)
oxides, sulfides and salts of manganese; (ii) oxides, sulfides and salts of
iron; (iii)
combinations of (i) and KI; (iv) combinations of (ii) and KI; and (v) mixtures
and
combinations of any two or more of (i), (ii), (iii) and (iv). According to
certain embodiments
of the invention, the sorbent body comprises an alkaline earth metal hydroxide
as a metal for
promoting the removal of toxic elements, such as Ca(OH)2.
100521 Precious metals (Ru, Th, Pd, Ag, Re, Os, Ir, Pt and Au) and transition
metals and
compounds thereof are exemplary metal catalysts. Further non-limiting metal
catalysts
include alkali and alkaline earth halides, hydroxides or oxides; and oxides,
sulfides, and salts
of vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, niobium,
molybdenum,
silver, tungsten, and lanthanoids. The metal catalysts can exist at any
valency. For example,
if iron is present, it may be present at +3, +2 or 0 valencies or as mixtures
of differing
valencies, and can be present as metallic iron (0), FeO, Fe203, Fe308, FeS,
FeC12, FeC13,
FeSO4, and the like. For another example, if manganese is present, it may be
present at +4,
+2 or 0 valencies or as mixtures of differing valences, and can be present as
metallic
manganese (0), MnO, Mn02, MnS, MnC12, MnC14, MnSO4, and the like. In some
embodiments, the metal catalyst is not in the form of an oxide. In other
embodiments, the
sorbent body comprises at least one metal catalyst that is not in the form of
an oxide.
[0053] In certain embodiments of the sorbent body of the invention, the metal
catalyst is
in a form selected from: alkali halides; and oxides, sulfides and salts of
manganese and iron.
In certain embodiments of the sorbent bodies of the invention, the metal
catalyst is in a form
selected from: combination of KI and oxides, sulfides and salts of manganese;
combination
of KI and oxides, sulfides and salts of iron; or a combination of KI, oxides,
sulfides and salts
of manganese and iron. These combinations are found to be particularly
effective in
removing mercury, especially elemental mercury from a gas stream.
[0054] According to certain embodiments of the invention, the sorbent body
comprises
an alkaline earth metal hydroxide as a metal for promoting the removal of
toxic elements,
such as Ca(OH)2. Experiments have shown that Ca(OH)2 can be particularly
effective in
promoting the removal of arsenic, cadmium and selenium from a gas stream.
[00551 In some embodiments of the invention, the metal catalyst is an alkali
metal such
as lithium, sodium, or potassium. In other embodiments, the metal catalyst is
an alkaline
earth metal such as magnesium, calcium, or barium. In other embodiments, the
metal catalyst
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is a transition metal, such as palladium, platinum, silver, gold, manganese,
or iron. In other
embodiments, the metal catalyst is a rare earth metal such as cerium. In some
embodiments,
the metal catalyst is in elemental form. In other embodiments, the metal
catalyst is a metal
sulfide. In other embodiments, the metal catalyst is a transition metal
sulfide or oxide. In yet
other embodiments, the sorbent body comprises at least on catalyst other than
an alkali metal,
an alkaline earth metal, or transition metal. In other embodiments, the
sorbent body
comprises at least one catalyst other than sodium, other than potassium, other
than
magnesium, other than calcium, other than aluminum, other than titanium, other
than
zirconium, other than chromium, other than magnesium, other than iron and/or
other than
zinc. In other embodiments, the sorbent body comprises at least one metal
catalyst other than
aluminum, vanadium, iron, cobalt, nickel, copper, or zinc, either in elemental
form or as
sulfates.
[0056] The amount of the metal catalyst present in the sorbent bodies can be
selected,
depending on the particular metal catalyst used, and application for which the
sorbent bodies
are used, and the desired toxic element removing capacity and efficiency of
the sorbent body.
In certain embodiments of the sorbent bodies of the invention, the amount of
the metal
catalyst ranges from 1% to 20% by weight, in certain other embodiments from 2%
to 18%, in
certain other embodiments from 5% to 15%, in certain other embodiments from 5%
to 10%.
In yet further embodiments, the sorbent body comprises from 1% to 25% by
weight of the
metal catalyst (in certain embodiments from 1% to 20%, from 1% to 15%, from 3%
to 10%,
or from 3 to 5%).
[0057] If only one metal catalyst is present in a sorbent body in certain
embodiments that
recite a certain distribution of the metal catalyst in the activated carbon
matrix, the metal
catalyst is distributed throughout the activated carbon matrix. If multiple
metal catalysts are
present in these embodiments, at least one of them is distributed throughout
the activated
carbon matrix. By "distributed throughout the activated carbon matrix" is
meant that the
relevant specified material (metal catalyst, sulfur, and the like) is present
not just on the
external surface of the sorbent body or cell walls, but also deep inside the
sorbent body. Thus
the presence of the specific metal catalyst can be, e.g.: (i) on the wall
surfaces of nanoscale
pores defined by the activated carbon matrix; (ii) on the wall surfaces of
microscale pores
defined by the activated carbon matrix; (iii) submerged in the wall structure
of the activated
carbon matrix; (iv) partly embedded in the wall structure of the activated
carbon matrix; (v)
partly fill and/or block some pores defined by the activated carbon matrix;
and (vi)
completely fill and/or block some pores defined by the activated carbon
matrix. In situations
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(iii), (iv), (v) and (vi), the metal catalyst(s) and/or other components
distributed in the
activated carbon matrix actually forms part of the wall structure of the pores
of the sorbent
body. In certain embodiments, multiple metal catalysts are present and all of
them are
distributed throughout the activated carbon matrix. However, it is not
required that all metal
catalysts are distributed throughout the activated carbon matrix. Thus, in
certain
embodiments, multiple metal catalysts are present, with at least one of them
distributed
throughout the activated carbon matrix, and at least one of them distributed
essentially mainly
on the external surface area and/or cell wall surface of the sorbent body,
and/or within a thin
layer beneath the external surface area and/or cell wall surface. In certain
embodiments, at
least a portion of the metal catalysts may be chemically bonded with other
components of the
sorbent body, such as carbon or the sulfur. In certain other embodiments, at
least a portion of
the metal catalysts may be physically bonded with the activated carbon matrix
or other
components. Still in certain other embodiments, at least a portion of the
metal catalyst is
present in the sorbent body in the form of particles having nanoscale or
microscale size.
[00581 Distribution of a metal catalyst in the sorbent body or other body or
material
according to the invention can be measured and characterized by the
Distribution
Characterization Method described sunra. In certain embodiments of the sorbent
body of the
invention, the distribution of a metal catalyst has the following feature: in
each target test area:
CON(av)/CON(min) < 30, and CON(max)/CON(av) < 30. In certain other
embodiments, it is
desired that CON(av)/CON(min) < 20, and CON(max)/CON(av) < 20. In certain
other
embodiments, it is desired that CON(av)/CON(min) < 15, and CON(max)/CON(av) <
15. In
certain other embodiments, it is desired that CON(av)/CON(min) < 10, and
CON(max)/CON(av) < 10. In certain other embodiments, it is desired that
CON(av)/CON(min) < 5, and CON(max)/CON(av) < 5. In certain other embodiments,
it is
desired that CON(av)/CON(min) < 3, and CON(max)/CON(av) < 3. In certain other
embodiments, it is desired that CON(av)/CON(min) < 2, and CON(max)/CON(av) <
2.
[0059] In certain embodiments of the sorbent body of the invention, at least
one metal
catalyst is homogeneously distributed throughout the activated carbon matrix
according to the
Distribution Characterization Method described supra. Thus: in each target
test area, for all
CON(m) where 0.1 n< m< 0.9n: 0.5 < CON(m)/CON(av) < 2.
[0060] In certain embodiments, it is desired that 0.6 < CON(m)/CON(av) < 1.7.
In
certain other embodiments, it is desired that 0.7 < CON(m)/CON(av) < 1.4. In
certain other
embodiments, it is desired that 0.8 < CON(m)/CON(av) < 1.2. In certain other
embodiments,
it is desired that 0.9 < CON(m)/CON(av) < 1.1. In certain embodiments, for all
CON(m)
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where 0.05n < m< 0.95n: 0.5 <_ CON(m)/CON(av) < 2; in certain embodiments, 0.6
<
CON(m)/CON(av) < 1.7. In certain other embodiments, it is desired that 0.7 <
CON(m)/CON(av) < 1.4. In certain other embodiments, it is desired that 0.8 <
CON(m)/CON(av) < 1.2. In certain other embodiments, it is desired that 0.9 <
CON(m)/CON(av) < 1.1. In certain embodiments of the bodies (sorbent body,
extrusion
mixture body, and the like) and material of the invention, in addition to any
one of the
features stated above in this paragraph with respect to each individual target
test area, the
distribution of the relevant material (e.g., sulfur, metal catalyst, and the
like) with respect to
all p target test areas has the following feature: for all CONAV(k) where O.lp
< k< 0.9p: 0.5
< CONAV(k)/CONAV(av) < 2; in certain embodiments, 0.6 < CONAV(k)/CONAV(av) <
1.7. In certain other embodiments, it is desired that 0.7 < CONAV(k)/CONAV(av)
< 1.4. In
certain other embodiments, it is desired that 0.8 < CONAV(k)/CONAV(av) < 1.2.
In certain
other embodiments, it is desired that 0.9 < CONAV(k)/CONAV(av) < 1.1. In
certain other
embodiments, it is desired that 0.95 < CONAV(k)/CONAV(av) < 1.05. In certain
embodiments, for all CONAV(k) where 0.05p < k< 0.95p: 0.5 < CONAV(k)/CONAV(av)
<
2; in certain embodiments, 0.6 < CONAV(k)/CONAV(av) < 1.7. In certain other
embodiments, it is desired that 0.7 < CONAV(k)/CONAV(av) < 1.4. In certain
other
embodiments, it is desired that 0.8 < CONAV(k)/CONAV(av) < 1.2. In certain
other
embodiments, it is desired that 0.9 < CONAV(k)/CONAV(av) < 1.1. In certain
other
embodiments, it is desired that 0.95 < CONAV(k)/CONAV(av) < 1.05.
[0061] In certain embodiments of the invention, the metal catalyst is present
on a
majority of the wall surfaces of the microscale pores. In certain other
embodiments of the
invention, the metal catalyst is present on at least 75%, at least 90% or at
least 95% of the
wall surfaces of the microscale pores.
[0062] In certain embodiments of the invention, the metal catalyst is present
on at least
20%, at least 40%, at least 50%, at least 75%, or at least 85% of the wall
surfaces of the
nanoscale pores. In certain embodiments, a majority of the specific area of
the sorbent body
is provided by the wall surfaces of the nanoscale pores. In these embodiments,
it is desired
that a higher percentage of the wall surface of the nanoscale pores has the
metal catalyst
distributed thereon.
[0063] The sorbent bodies of the invention comprise sulfur. The amount of
sulfur
present in the sorbent bodies can be selected depending on the particular
metal catalyst used,
and application for which the sorbent bodies are used, and the desired toxic
element
removing capacity and efficiency of sorbent body.
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[0064] In some embodiments, the sorbent body comprises from 1% to 20% by
weight of
sulfur (in certain embodiments from 1% to 15%, from 3% to 8%, from 2% to 10%,
from 0.1
to 5%, or from 2 to 5%). Sulfur may be present in the form of elemental sulfur
(0 valency),
sulfides (-2 valency, e.g.), sulfite (+4 valency, e.g.), sulfate (+6 valency,
e.g.). In some
embodiments, sulfur is not present as a sulfate, or, a sulfate is not the only
source of sulfur in
the sorbent body. It is desired that at least part of the sulfur is present in
a valency capable of
chemically bonding with the toxic element to be removed from a fluid stream,
such as with
mercury. To that end, it is desired that at least part of the sulfur is
present at -2 and/or zero
valency. At least a portion of the sulfur may be chemically or physically
bonded to the wall
surface of the activated carbon matrix. At least a portion of the sulfur may
be chemically or
physically bonded to the metal catalyst, as indicated supra, e.g., in the form
of a sulfide (FeS,
MnS, MoZS3, CuS and the like).
[0065] In some embodiments, at least a portion of the sulfur is at zero
valency. For
instance, at least 10% of the sulfur on the surface of the walls of the pores
of the activated
carbon matrix may be essentially at zero valency when measured by XPS. In
other
embodiments at least a portion of the sulfur is not at zero valency. In some
embodiments, the
sorbent bodies comprise a portion of sulfur at zero valency and a portion of
sulfur not at zero
valency. In some embodiments, the sorbent bodies comprise elemental sulfur as
well as
sulfur present in chemical compound comprising sulfur, such as a metal
sulfide.
[0066] In certain embodiments, it is desired that at least 40%, at least 50%,
at least 60%,
or at least 70% by mole of the sulfur in the sorbent body be at zero valency.
According to
certain embodiments, at least 10%, at least 20%, at least 30%, at least 40%,
at least 50% or at
least 60% of the sulfur on the surface of the walls of the pores is
essentially at zero valency,
when measured by XPS.
[0067] Experiments have demonstrated that sorbent bodies of activated carbon,
sulfur
and metal catalyst can be effective for removing arsenic, cadmium as well as
selenium, in
addition to mercury, from a gas stream. Experiments have demonstrated that
sorbent bodies
comprising elemental sulfur tend to have higher mercury removal capability
than those
without elemental sulfur but with essentially the same total sulfur
concentration.
[0068] In certain embodiments, sulfur is distributed throughout the activated
carbon
matrix. By "distributed throughout the activated carbon matrix" is meant that
sulfur is
present not just on the external surface of the sorbent body or cell walls,
but also deep inside
the sorbent body. Thus the presence of sulfur can be, e.g.: (i) on the wall
surfaces of
nanoscale pores; (ii) on the wall surfaces of microscale pores; (iii)
submerged in the wall
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structure of the activated carbon matrix; and (iv) partly embedded in the wall
structure of the
activated carbon matrix. In situations (iii) and (iv), sulfur actually forms
part of the wall
structure of the pores of the sorbent body. Therefore, in certain embodiments,
some of sulfur
may be chemically bonded (covalently and/or ionically) with other components
of the sorbent
body, such as carbon or the metal catalyst. In certain other embodiments, some
of the sulfur
may be physically bonded with the activated carbon matrix or other components.
Still in
certain other embodiments, some of the sulfur is present in the sorbent body
in the form of
particles having nanoscale or microscale size.
[0069] Distribution of sulfur in the sorbent body or other body or material
according to
the present invention can be measured and characterized by the Distribution
Characterization
Method described supra.
[0070] In certain embodiments, the distribution of sulfur in any target test
area has the
following feature: CON(max)/CON(min) > 100. In certain other embodiments:
CON(max)/
CON(min) > 200. In certain other embodiments: CON(max) / CON(min) > 300. In
certain
other embodiments: CON(max) / CON(min) > 400. In certain other embodiments:
CON(max)
/ CON(min) > 500. In certain other embodiments: CON(max) / CON(min) > 1000. In
certain other embodiments: CON(max) /CON(av) > 50. In certain other
embodiments:
CON(max) / CON(av) > 100. In certain other embodiments: CON(max) / CON(av) >
200.
In certain other embodiments: CON(max) / CON(av) > 300. In certain other
embodiments:
CON(max) / CON(av) > 400. In certain other embodiments: CON(max) / CON(av) >
500.
In certain other embodiments: CON(max) / CON(av) > 1000.
[0071] In certain embodiments, with regard to sulfur distributed in the
sorbent body, the
distribution thereof in all p target test areas has the following feature:
CONAV(1)/CONAV(n) > 2. In certain other embodiments: CONAV(1)/ CONAV(n) > 5.
In
certain other embodiments: CONAV(1)/ CONAV(n) > 8. In certain other
embodiments:
CONAV(1)/ CONAV(n) > 1.5. In certain other embodiments: CONAV(1) / CONAV(av) >
2.
In certain other embodiments: CONAV(1) / CONAV(av) > 3. In certain other
embodiments:
CONAV(1) / CONAV(av) > 4. In certain other embodiments: CONAV(l) / CONAV(av) >
5.
In certain other embodiments: CONAV(1) / CONAV(av) > 8. In certain other
embodiments:
CONAV(l) / CONAV(av) > 10.
[0072] In certain other embodiments, with regard to sulfur distributed in the
sorbent
body, in each target test area, the distribution thereof has the following
feature:
CON(av)/CON(min) < 30. In certain other embodiments: CON(av)/CON(min) < 20. In
certain other embodiments: CON(av)/CON(min) < 15. In certain other
embodiments:
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CON(av)/CON(min) < 10. In certain other embodiments: CON(av)/CON(min) < 5. In
certain other embodiments: CON(av)/CON(min) < 3. In certain other embodiments:
CON(av)/CON(min) < 2. In certain other embodiments: CON(max)/CON(av) < 30. In
certain other embodiments: CON(max)/CON(av) < 20. In certain other
embodiments:
CON(max)/CON(av) < 15. In certain other embodiments: CON(max)/CON(av) < 10. In
certain other embodiments: CON(max)/CON(av) < 5. In certain other embodiments:
CON(max)/CON(av) < 3. In certain other embodiments: CON(max)/CON(av) < 2.
[0073] In certain embodiments of the sorbent body of the present invention,
the
distribution of sulfur has the following feature: in each target test area,
CON(av)/CON(min) <
30, and CON(max)/CON(av) < 30. In certain other embodiments, it is desired
that
CON(av)/CON(min) < 20, and CON(max)/CON(av) < 20. In certain other
embodiments, it is
desired that CON(av)/CON(min) < 15, and CON(max)/CON(av) < 15. In certain
other
embodiments, it is desired that CON(av)/CON(min) < 10, and CON(max)/CON(av) <
10. In
certain other embodiments, it is desired that CON(av)/CON(min) < 5, and
CON(max)/CON(av) < 5. In certain other embodiments, it is desired that
CON(av)/CON(min) < 3, and CON(max)/CON(av) < 3. In certain other embodiments,
it is
desired that CON(av)/CON(min) < 2, and CON(max)/CON(av) < 2.
[0074] In certain embodiments of the sorbent body of the present invention,
sulfur is
homogeneously distributed throughout the activated carbon matrix according to
the
Distribution Characterization Method described supra. Thus: in each target
test area, for all
CON(m) where 0.1 n< m< 0.9n: 0.5 < CON(m)/CON(av) < 2.
[0075] In certain embodiments, it is desired that 0.6 < CON(m)/CON(av) < 1.7.
In
certain other embodiments, it is desired that- 0.7 < CON(m)/CON(av) < 1.4. In
certain other
embodiments, it is desired that 0.8 < CON(m)/CON(av) < 1.2. In certain other
embodiments,
it is desired that 0.9 < CON(m)/CON(av) < 1.1. In certain embodiments, for all
CON(m)
where 0.05n < m< 0.95n: 0.5 < CON(m)/CON(av) < 2; in certain embodiments, 0.6
CON(m)/CON(av) < 1.7. In certain other embodiments, it is desired that 0.7 <
CON(m)/CON(av) < 1.4. In certain other embodiments, it is desired that 0.8 <
CON(m)/CON(av) < 1.2. In certain other embodiments, it is desired that 0.9 <
CON(m)/CON(av) < 1.1. In certain embodiments of the bodies (sorbent body,
extrusion
mixture body, and the like) and material of the present invention, in addition
to any one of the
features stated above in this paragraph with respect to each individual target
test area, the
distribution of the relevant material (e.g., sulfur, metal catalyst, and the
like) with respect to
all p target test areas has the following feature: for all CONAV(k) where 0.1
p< k< 0.9p: 0.5
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< CONAV(k)/CONAV(av) < 2; in certain embodiments, 0.6 < CONAV(k)/CONAV(av) <
1.7. In certain other embodiments, it is desired that 0.7 < CONAV(k)/CONAV(av)
< 1.4. In
certain other embodiments, it is desired that 0.8 < CONAV(k)/CONAV(av) < 1.2.
In certain
other embodiments, it is desired that 0.9 < CONAV(k)/CONAV(av) < 1.1. In
certain other
embodiments, it is desired that 0.95 < CONAV(k)/CONAV(av) < 1.05: In certain
embodiments, for all CONAV(k) where 0.05p < k< 0.95p: 0.5 < CONAV(k)/CONAV(av)
<
2; in certain embodiments, 0.6 < CONAV(k)/CONAV(av) < 1.7. In certain other
embodiments, it is desired that 0.7 < CONAV(k)/CONAV(av) < 1.4. In certain
other
embodiments, it is desired that 0.8 < CONAV(k)/CONAV(av) < 1.2. In certain
other
embodiments, it is desired that 0.9 <_ CONAV(k)/CONAV(av) < 1.1. In certain
other
embodiments, it is desired that 0.95 < CONAV(k)/CONAV(av) < 1.05.
[0076] In certain embodiments, sulfur is present on a majority of the wall
surfaces of the
microscale pores. In certain other embodiments, sulfur is present on at least
75%, at least
90%, or at least 95% of the wall surfaces of the microscale pores.
[0077] In certain embodiments, sulfur is present on at least 20%, at least
30%, at least
40%, at least 50%, at least 75%, or at least 85% of the wall surfaces of the
nanoscale pores.
In certain embodiments, a majority of the specific area of the sorbent body is
provided by the
wall surfaces of the nanoscale pores. In these embodiments, it is desired that
a high
percentage (such as at least 40%, at least 50%, or at least 60%) of the wall
surface of the
nanoscale pores has sulfur distributed thereon.
[0078] The sorbent body may further comprise inorganic filler material. In
contrast to
the metal catalyst, any metal element in the inorganic filler material is
chemically and
physically inert. As such, the metal element included in the inorganic filler
does not function
in one or more of the following ways to promote the removal of the toxic
elements from a
fluid in contact with a sorbent body of the invention: (i) temporary or
permanent chemical
sorption (e.g., via covalent and/or ionic bonds) of a toxic element; (ii)
temporary or
permanent physical sorption of a toxic element; (iii) catalyzing the
reaction/sorption of a
toxic element with other components of the sorbent body; (iv) catalyzing the
reaction of a
toxic element with the ambient atmosphere to convert it from one form to
another; (v)
trapping a toxic element already sorbed by other components of the sorbent
body; and (vi)
facilitating the transfer of a toxic element to the active sorbing sites.
[0079] Inorganic fillers may be included for the purpose of, inter ali
reducing cost, and
improving physical (coefficient of thermal expansion; modulus of rupture,
e.g.); or chemical
properties (water resistance; high temperature resistance; corrosion-
resistance, e.g.) of the
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sorbent body. Such inorganic filler can be an oxide glass, oxide ceramic, or
certain refractory
materials. Non-limiting examples of inorganic fillers include: silica;
alumina; zircon;
zirconia; mullite; cordierite; refractory metals; and the like. In certain
embodiments, the
inorganic fillers are per se porous. A high porosity of the inorganic fillers
can improve the
mechanical strength of the sorbent body without unduly sacrificing the
specific area. The
inorganic filler may be distributed throughout the sorbent body. The inorganic
filler may be
present in the form of minuscule particles distributed in the sorbent body.
Depending on the
application of the sorbent body and other factors, in certain embodiments, the
sorbent body
may comprise, e.g., up to 50% by weight of inorganic filler, in certain other
embodiments up
to 40%, in certain other embodiments up to 30%, in certain other embodiments
up to 20%, in
certain other embodiments up to 10%.
[0080] In order to obtain a high specific surface area of the sorbent body, it
is desired
that, if inorganic fillers are included, such inorganic fillers in and of
themselves are porous
and contribute partly to the high specific area of the sorbent body. Inorganic
fillers having
specific surface area comparable to that of the activated carbon is usually
difficult or costly to
be included in the sorbent body. Therefore, along with the typical mechanical
reinforcement
such inorganic fillers would bring to the final sorbent body, it also tends to
compromise the
overall specific area of the sorbent body. This can be highly undesirable in
some cases. A
high surface area of the sorbent body usually means more active sites
(including carbon sites
capable of sorption of the toxic elements, sulfur capable of promoting or
direct sorption of the
toxic elements, and the metal catalyst capable of promoting sorption of the
toxic elements)
for the sorption of the toxic elements. It is further believed that close
proximity of the three
categories of active sorption sites in the sorbent body is conducive to the
overall sorption
capability.
[0081] The incorporation of large amounts of inorganic fillers dilutes the
metal catalyst
and sulfur in the carbon matrix, adding to the overall average distances
between and among
these three categories of active sites. Hence, in some embodiments, the
sorbent body has a
relative low percentage of inorganic filler (the remainder of the sorbent body
being carbon,
sulfur and metal catalyst). In certain embodiments, the sorbent body comprises
less than 40%,
less than 30%, less than 20%, less than 10%, less than 9%, less than 8%, less
than 7%, less
than 6%, less than 5%, less than 4%, less than 3%, less than 2%, less than 1%,
or less than
0.5% by weight of inorganic filler. In one embodiment, the sorbent body
comprises no
inorganic filler. Sorbent bodies, which comprise lesser amounts of inorganic
fillers, can lead
to a more uniform distribution of mercury capture throughout the cross-section
of the walls of
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the activated carbon matrix. Thus, in certain embodiments, the sorbent body
comprises at
least 90% by weight (in certain embodiments at least 91%, at least 92%, at
least 93%, at least
94%, at least 95%, at least 96%, at least 97%, or at least 98%) of activated
carbon, sulfur and
the metal catalyst in total.
[0082] A further embodiment of the invention is a sorbent body comprising:
activated carbon;
sulfur, in any oxidation state, as elemental sulfur or in a chemical compound
or
moiety comprising sulfur; and
a metal catalyst, in any oxidation state, as elemental metal or in a chemical
compound
or moiety comprising the metal;
wherein at least a portion of the metal catalyst is chemically bound to at
least a
portion of the sulfiu.
[0083] As in other embodiments of sorbent bodies disclosed herein, at least a
portion of
the sulfur may be chemically bound to at least a portion of carbon in the
activated carbon
matrix. The sulfur and/or metal catalyst may be, in some embodiments,
distributed
throughout the activated carbon matrix. In other embodiments, the sulfur
and/or metal
catalyst is not distributed throughout the activated carbon matrix. The
sorbent body of this
and any other embodiment may comprise, for example, a metal sulfide such as
manganese
sulfide. The sorbent body of this embodiment may also have any one or more of
the other
characteristics mentioned for any other sorbent bodies of the invention,
including
characteristics of the activated carbon, of sulfur, and of the metal catalyst,
that have been
described earlier.
[0084] It is believed that embodiments of the sorbent bodies of the invention
are capable
of sorbing and removing toxic elements such as cadmium, mercury, chromium,
lead, barium,
beryllium, nickel, cobalt, vanadium, zinc, copper, manganese, antimony,
silver, thallium,
arsenic and selenium from fluids such as syngas streams and combustion flue
gas streams. It
has been found that the sorbent bodies are particularly effective in removing
mercury from a
flue gas stream. The removal capabilities of the sorbent materials with
respect to a certain
toxic element, e.g., mercury, are typically characterized by two parameters:
initial removal
efficiency and long term removal capacity. With respect to mercury, the
following procedure
is to be used to characterize the initial mercury removal efficiency and long
term mercury
removal capacity:
[0085] The sorbent body to be tested is loaded into a fixed bed through which
a
reference flue gas at 160 C having a specific composition is passed at a space
velocity of
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7500 hr-1. Concentrations of mercury in the gas stream are measured before and
after the
sorbent bed. At any given time, the instant mercury removal efficiency
(Eff(Hg)) is
calculated as follows:
E.f,.f,(Hg) = C - C, x 100%,
Co
where Co is the total mercury concentration in g=m 3 in the flue gas stream
immediately
before the sorbent bed, and C, is the total mercury concentration in g=m 3
immediately after
the sorbent bed. Initial mercury removal efficiency is defined as the average
mercury
removal efficiency during the first 1(one) hour of test after the fresh test
sorbent material is
loaded. Typically, the mercury removal efficiency of a fixed sorbent bed
diminishes over
time as the sorbent bed is loaded with more and more mercury. Mercury removal
capacity is
defined as the total amount of mercury trapped by the sorbent bed per unit
mass of the
sorbent body material until the instant mercury removal efficiency diminishes
to 90% under
the above testing conditions. Mercury removal capacity is typically expressed
in terms of mg
of mercury trapped per gram of the sorbent material (mg=g 1).
[0086] An exemplary test reference flue gas (referenced as RFG1 herein) has
the
following composition by volume: 02 5%; COZ 14%; SO2 1500 ppm; NOx 300 ppm;
HCl
100 ppm; Hg 20-25 gg=m"3; N2 balance; wherein NOX is a combination of NO2, N20
and NO;
Hg is a combination of elemental mercury (Hg(0), 50-60% by mole) and oxidized
mercury
(40-50% by mole). In certain embodiments, the sorbent body has an initial
mercury removal
efficiency with respect to RFG1 of at least 90%, at least 91%, at least 92%,
at least 95%, at
least 97%, at least 98%, at least 99%, or of at least 99.5%.
[0087] In certain embodiments, the sorbent body advantageously has a high
initial
mercury removal efficiency of at least 90% for flue gases comprising 02 5%;
CO2 14%; SO2
1500 ppm; NO3, 300 ppm; Hg 20-25 gg=m 3, having high concentrations of HCl and
low
concentrations of HCl alike. By "high concentrations of HCl" is meant that HCl
concentration in the gas to be treated is at least 20 ppm. By "low
concentration of HCl" is
meant that HCl concentration in the gas to be treated is at most 10 ppm. The
sorbent body of
certain embodiments has a high initial mercury removal efficiency of at least
90%, at least
91%, at least 93%, at least 95%, at least 96%, at least 98%, at least 99%, or
at least 99.5% for
a flue gas (referred to as RFG2) having the following composition: 02 5%; COZ
14%; SOZ
1500 ppm; NOX 300 ppm; HCI 5 ppm; Hg 20-25 gg=m 3; N2 balance. High mercury
removal
efficiency of these embodiments for low HCl flue gas is particularly
advantageous compared
to the prior art. In the prior art processes involving the injection of
activated carbon powder,
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it is typically required that HCl be added to the flue gas in order to obtain
a sufficient initial
mercury removal efficiency. The embodiments presenting high mercury efficiency
at low
HCI concentration allows for the efficient and effective removal of mercury
from a flue gas
stream without the need of injecting HCl into the gas stream.
[0088] In certain embodiments, the sorbent body has a high initial mercury
removal
efficiency of at least 91% for flue gases comprising 02 5%; CO2 14%; SO2 1500
ppm; NOX
300 ppm; Hg 20-25 g=m 3, having high concentrations of SO3 (such as 5 ppm, 8
ppm, 10
ppm, 15 ppm, 20 ppm, 30 ppm, 40 ppm) and low concentrations of SO3 alike (such
as 0.01
ppm, 0.1 ppm, 0.5 ppm, 1 ppm, 2 ppm). By "high concentrations of SO3" is meant
that SO3
concentration in the gas to be treated is at least 3 ppm by volume. By "low
concentration of
SO3" is meant that SO3 concentration in the gas to be treated is less than 3
ppm. The sorbent
body of certain embodiments advantageously has a high initial mercury removal
efficiency of
at least 90%, at least 91%, at least 95%, at least 98%, or at least 99% for a
flue gas (referred
to as RFG3) having the following composition: 02 5%; COZ 14%; SO2 1500 ppm;
NOX 300
ppm; SO3 5 ppm; Hg 20-25 g=m 3; N2 balance. High mercury removal efficiency
of certain
embodiments for high SO3 flue gas is particularly advantageous compared to the
prior art. In
the prior art processes involving the injection of activated carbon powder, it
is typically
required that SO3 be removed from the flue gas in order to obtain a sufficient
initial mercury
removal efficiency. The embodiments presenting high mercury efficiency at high
SO3
concentration allows for the efficient and effective removal of mercury from a
flue gas stream
without the need of prior removal of SO3 from the gas stream.
[0089] According to certain embodiments, the sorbent body has a Hg removal
capacity
of 0.05 mg=g with respect to RFG1, in certain embodiments of at least 0.10
mg=g 1, at least
0.15 mg=g at least 0.20 mg=g at least 0.25 mg=g at least 0.30 mg=g at least
0.50 mg=g
at least 1.0 mg=g 1, least 2.0 mg=g 1, or at least 3.0 mg=g lor with respect
to RFG1.
[00901 According to certain embodiments, the sorbent body has an Hg removal
capacity
of 0.05 mg=g 1 with respect to RFG2, in certain embodiments of at feast 0.10
mg=g ], at least
0.15 mg=g 1, at least 0.20 mg=g"1, at least 0.25 mg=g 1, at least 0.30 mg=g 1,
at least 0.50 mg=g 1,
at least 1.0 mg=g 1, least 2.0 mg=g"1, or at least 3.0 mg=g twith respect to
RFG2. Thus, the
sorbent bodies according to these embodiments have a high mercury removal
capacity with
respect to low HCl flue gas streams. This is particularly advantageous
compared to prior art
mercury abatement processes.
[0091] According to certain embodiments, the sorbent body has an Hg removal
capacity
of 0.05 mg=g I with respect to RFG3, in certain embodiments of at least 0.10
mg=g 1, at least
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0.15 mg=g"1, at least 0.20 mg=g 1, at least 0.25 mg=g 1, at least 0.30 mg=g 1,
at least 0.50 mg=g 1,
at least 1.0 mg=g 1, least 2.0 mg=g 1, or at least 3.0 mg=g"I with respect to
RFG3. Thus, the
sorbent bodies according to these embodiments have a high mercury removal
capacity with
respect to high SO3 flue gas streams. This is particularly advantageous
compared to the prior
art mercury abatement processes.
[0092] A further embodiment of the invention is thus any sorbent body
described herein,
wherein the sorbent body has an initial mercury removal efficiency of at least
90% with
respect to RFG1, RFG2 and/or RFG3, or wherein the sorbent body has a mercury
removal
capacity of at least 0.05 mg=gl with respect to RFG1, RFG2 and/or RFG3.
[0093] In view of the above, an embodiment of the invention is a sorbent body
comprising:
activated carbon;
sulfur, in any oxidation state, as elemental sulfur or in a chemical compound
or
moiety comprising sulfur; and
a metal catalyst, in any oxidation state, as elemental metal or in a chemical
compound
or moiety comprising the metal;
wherein the sorbent body has an initial mercury removal efficiency of at least
90%
with respect to RFG1, RFG2 and/or RFG3. For instance, the sorbent body may
have an
initial mercury removal efficiency of at least 91%, at least 95%, at least 98%
or at least 99%
with respect to RFG1, RFG2 and/or RFG3. The sulfur and/or metal catalyst may
be, in some
embodiments, distributed throughout the activated carbon matrix. In other
embodiments, the
sulfur and/or metal catalyst is not distributed throughout the activated
carbon matrix. The
sorbent body of this embodiment may also have any one or more of the other
characteristics
mentioned for any other sorbent bodies of the invention, including
characteristics of the
activated carbon, of sulfur, and of the metal catalyst, that have been
described earlier.
[0094] A further embodiment of the invention is a sorbent body comprising:
activated carbon;
sulfur, in any oxidation state, as elemental sulfur or in a chemical compound
or
moiety comprising sulfur; and
a metal catalyst, in any oxidation state, as elemental metal or in a chemical
compound
or moiety comprising the metal;
wherein the sorbent body has a mercury removal capacity of at least 0.05 mg=g
1 with
respect to RFG1, RFG2 and/or RFG3. For instance, the sorbent body may have a
mercury
removal capacity of at least 0.10 mg=g , at least 0.15 mg=g at least 0.20 mg=g
at least 0.25
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mg=g-1, at least 0.30 mg=g 1, at least 0.50 mg=g 1, at least 1.0 mg=g"1, least
2.0 mg=g 1, or at least
3.0 mg=g 1 with respect to RFG1, RFG2 and/or RFG3. The sulfur and/or metal
catalyst may
be, in some embodiments, distributed throughout the activated carbon matrix.
In other
embodiments, the sulfur and/or metal catalyst is not distributed throughout
the activated
carbon matrix. The sorbent body of this embodiment may also have any one or
more of the
other characteristics mentioned for any other sorbent bodies of the invention,
including
characteristics of the activated carbon, of sulfur, and of the metal catalyst,
that have been
described earlier.
(0095] Another aspect of the invention is a method for the removal of a toxic
element
from a fluid, which comprises contacting the fluid containing the toxic
element with a sorbent
body according to the invention. Toxic elements include cadmium, mercury,
chromium, lead,
barium, beryllium, nickel, cobalt, vanadium, zinc, copper, manganese,
antimony, silver,
thallium, arsenic and selenium, any of which may be in any oxidation state and
may be in
elemental form or in a chemical compound comprising the element. The sorbent
bodies may
be used, for instance, for treating fluid streams, including gas streams and
fluid streams
comprising toxic elements, such as arsenic, cadmium, mercury and/or selenium,
for abating
them. Such processes typically comprise a step of placing the sorbent body in
the fluid
stream. Such treatment process is particularly advantageous for abating
mercury from the
fluid stream.
[0096] Due to their ability to remove elemental mercury from fluids, a
particularly
advantageous embodiment of the process comprises placing the sorbent bodies in
a gas
stream comprising mercury wherein at least 10%, at least 20%, at least 30%, at
least 40%, at
least 50%, at least 60% or at least 70% by mole of the mercury is in elemental
state.
[0097] Due to their ability to remove mercury from fluids even if a gas stream
comprises
HCl at a very low level, a particularly advantageous embodiment of the process
comprises
placing the sorbent bodies in a gas stream comprising mercury and HCl at a HCl
concentration of lower than 50 ppm by volume, lower than 40 ppm, lower than 30
ppm,
lower than 20 ppm, or lower than 10 ppm.
[0098] Due to their ability to remove mercury from fluids even if a gas stream
comprises
SO3 at a high level, a particularly advantageous embodiment of the process
comprises placing
the sorbent bodies in a gas stream comprising mercury and SO3 at a SO3
concentration of at
least 3 ppm by volume, in certain embodiments higher than 5 ppm, higher than 8
ppm, higher
than 10 ppm, or higher than 20 ppm.
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[0099] A further aspect of the invention is a process for making a sorbent
body,
comprising:
(A) providing a batch mixture body formed of a batch mixture material
comprising a
carbon-source material, a sulfur-source material, a metal catalyst-source
material and an
optional filler material, wherein the metal catalyst-source material is
substantially
homogeneously distributed in the mixture;
(B) carbonizing the batch mixture body; and
(C) activating the carbonized batch mixture body.
[001001 In certain embodiments, the carbon-source material comprises:
synthetic carbon-
containing polymeric material; activated carbon powder; charcoal powder; coal
tar pitch;
petroleum pitch; wood flour; cellulose and derivatives thereof; natural
organic materials such
as wheat flour; wood flour, corn flour, nut-shell flour; starch; coke; coal;
or mixtures or
combinations of any two or more of these. All these materials contain certain
components
comprising carbon atoms in its structure units on a molecular level that can
be at least partly
retained in the final activated carbon matrix of the sorbent body. According
to certain
embodiments the carbon-source material comprises a phenolic resin or a resin
based on
furfuryl alcohol.
[00101] In one embodiment, the synthetic polymeric material can be a synthetic
resin in
the form of a solution or low viscosity liquid at ambient temperatures.
Alternatively, the
synthetic polymeric material can be a solid at ambient temperature and capable
of being
liquefied by heating or other means. Examples of useful polymeric carbon-
source materials
include thermosetting resins and thermoplastic resins (e.g., polyvinylidene
chloride,
polyvinyl chloride, polyvinyl alcohol, and the like). Still further, in one
embodiment,
relatively low viscosity carbon precursors (e.g., thermosetting resins) can be
preferred,
having exemplary viscosity ranges from about 50 to 100 cps. In another
embodiment, any
high carbon yield resin can be used. To this end, by high carbon yield is
meant that greater
than about 10% of the starting weight of the resin is converted to carbon on
carbonization. In
another embodiment, the synthetic polymeric material can comprise a phenolic
resin or a
furfural alcohol based resin such as furan resins. Phenolic resins can again
be preferred due
to their low viscosity, high carbon yield, high degree of cross-linking upon
curing relative to
other precursors, and low cost. Exemplary suitable phenolic resins are resole
resin such as
plyophen resin. An exemplary suitable furan liquid resin is Furcab-LP from QO
Chemicals
Inc., IN, U.S.A. An exemplary solid resin well suited for use as a synthetic
carbon precursor
is solid phenolic resin or novolak. Still further, it should be understood
that mixtures of
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novolak and one or more resole resins can also be used as suitable polymeric
carbon-source
material. The phenolic resin may be pre-cured or uncured when mixed with other
material to
form the batch mixture material. Where the phenolic resin is pre-cured, the
pre-cured
material may comprise sulfur, metal catalyst or the optional inorganic filler
pre-loaded. In
certain embodiments, it is desired that a curable, uncured resin is included
as part of the
carbon-source material in the batch mixture material. Curable materials,
thermoplastic or
thermosetting, undergo certain reactions, such as chain propagation,
crosslinking, and the like,
to form a cured material with higher degree of polymerization when being
subjected to cure
conditions, such as mild heat treatment, irradiation, chemical activation, and
the like.
[00102] In certain embodiments, organic binders typically used in extrusion
and/or
injection molding processes can be part of the carbon-source material as well.
Exemplary
binders that can be used are plasticizing organic binders such as cellulose
ethers. Typical
cellulose ethers include methylcellulose, ethylhydroxy ethylcellulose,
hydroxybutyl-cellulose,
hydroxybutyl methylcellulose, hydroxyethylcellulose, hydroxymethylcellulose,
hydroxypropylcellulose, hydroxypropyl methylcellulose, hydroxyethyl
methylcellulose,
sodium carboxy methylcellulose, and mixtures thereof. Further, cellulose
ethers such as
methylcellulose and/or methylcellulose derivatives are especially suited as
organic binders,
with methylcellulose, hydroxypropyl methylcellulose, or combinations of these
being
preferred. An example methylcellulose binder is METHOCEL A, sold by the Dow
Chemical
Company. Example hydroxypropyl methylcellulose binders include METHOCEL E, F,
J, K,
also sold by the Dow Chemical Company. Binders in the METHCEL 310 Series, also
sold
by the Dow Chemical Company, can also be used in the context of the invention.
METHOCEL A4M is an example binder for use with a RAM extruder. METHOCEL F240C
is an example binder for use with a twin screw extruder.
[00103] Carbonizable organic fillers may be used as part of the carbon-source
material in
certain embodiments of the process. Exemplary carbonizable fillers include
both natural and
synthetic, hydrophobic and hydrophilic, fibrous and non-fibrous fillers. For
example some
natural fillers are soft woods, e.g., pine, spruce, redwood, etc.; hardwoods,
e.g., ash, beech,
birch, maple, oak, etc.; sawdust, shell fibers, e.g., ground almond shell,
coconut shell, apricot
pit shell, peanut shell, pecan shell, walnut shell, etc.; cotton fibers, e.g.,
cotton flock, cotton
fabric, cellulose fibers, cotton seed fiber; chopped vegetable fibers, for
example, hemp,
coconut fiber, jute, sisal, and other materials such as corn cobs, citrus pulp
(dried), soybean
meal, peat moss, wheat flour, wool fibers, corn, potato, rice, tapiocas, etc.
Some synthetic
materials are regenerated cellulose, rayon fabric, cellophane, etc. One
especially suited
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carbonizable fiber filler is cellulose fiber as supplied by International
Filler Corporation,
North Tonawanda, N.Y. This material has the following sieve analysis: 1-2% on
40 mesh
(420 micrometers), 90-95% thru 100 mesh (149 micrometers), and 55-60% thru 200
mesh
(74 micrometers). Some hydrophobic organic synthetic fillers are
polyacrylonitrile fibers,
polyester fibers (flock), nylon fibers, polypropylene fibers (flock) or
powder, acrylic fibers or
powder, aramid fibers, polyvinyl alcohol, etc. Such organic fiberous fillers
may function in
part as part of the carbon-source material, in part as mechanical property
enhancer to the
batch mixture body, and in part as pore-forming agents that would mostly
vaporize upon
carbonization.
[00104] Non-limiting examples of metal catalyst-source material include:
alkali and
alkaline earth halides, oxides and hydroxides; oxides, sulfides, and salts of
vanadium,
chromium, manganese, iron, cobalt, nickel, copper, zinc, niobium, molybdenum,
silver,
tungsten, and lanthanoids. The metallic elements in the metal catalyst-source
materials can
be at various valencies. For example, if iron is included in the metal
catalyst-source material,
it may be present at +3, +2 or 0 valencies or as mixtures of differing
valencies, and can be
present as metallic iron (0), FeO, Fe203, Fe308, FeS, FeC12, FeC13, FeSO4, and
the like. For
another example, if manganese is present in the metal catalyst source, it may
be present at +4,
+2 or 0 valencies or mixtures of differing valences, and can be present as
metallic manganese
(0), MnO, Mn02, MnS, MnC12, MnCI¾, MnSO¾, and the like.
[00105] According to certain embodiments the metal catalyst-source material is
in a form
selected from: (i) halides and oxides of alkali and alkaline earth metals;
(ii) precious metals
and compounds thereof; (iii) oxides, sulfides, and salts of vanadium,
chromium, manganese,
iron, cobalt, nickel, copper, zinc, niobium, molybdenum, silver, tungsten and
lanthanoids; or
(iv) combinations and mixtures of two or more of (i), (ii) and (iii).
According to certain
embodiments of the process, the metal catalyst-source material is in a form
selected from: (i)
oxides, sulfides, sulfates, acetates and salts of manganese; (ii) oxides,
sulfides and salts of
iron; (iii) combinations of (i) and KI; (iv) combinations of (ii) and KI;
and/or (v) mixtures
and combinations of any two or more of (i), (ii), (iii) and (iv).
[00106] Non-limiting examples of sulfur-source material include: sulfur
powder; sulfur-
containing powdered resin; sulfides; sulfates; and other sulfur-containing
compounds; or
mixtures or combination of any two or more of these. Exemplary sulfur-
containing
compounds can include hydrogen sulfide and/or its salts, carbon disulfide,
sulfur dioxide,
thiophene, sulfur anhydride, sulfur halides, sulfuric ester, sulfurous acid,
sulfacid, sulfatol,
sulfamic acid, sulfan, sulfanes, sulfuric acid and its salts, sulfite,
sulfoacid, sulfobenzide, and
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mixtures thereof. When elemental sulfur powder is used, in one embodiment it
can be
preferred to have an average particle diameter that does not exceed about 100
micrometers.
Still further, it is preferred in certain embodiments that the elemental
sulfur powder has an
average particle diameter that does not exceed about 10 micrometers.
[001071 Inorganic fillers are not required to be present in the batch mixture
material.
However, if present, the filler material can be, e.g.: oxide glass; oxide
ceramics; or other
refractory materials. Exemplary inorganic fillers that can be used include
oxygen-containing
minerals or salts thereof, such as clays, zeolites, talc, etc., carbonates,
such as calcium
carbonate, alumninosilicates such as kaolin (an aluminosilicate clay), flyash.
(an
aluminosilicate ash obtained after coal firing in power plants), silicates,
e.g., wollastonite
(calcium metasilicate), titanates, zirconates, zirconia, zirconia spinel,
magnesium aluminum
silicates, mullite, alumina, alumina trihydrate, boehmite, spinel, feldspar,
attapulgites, and
aluminosilicate fibers, cordierite powder, mullite; cordierite; silica;
alumina; other oxide glass;
other oxide ceramics; or other refractory material.
[00108] Some examples of especially suited inorganic fillers are cordierite
powder, talcs,
clays, and aluminosilicate fibers such as provided by Carborundum Co. Niagara
Falls, N.Y.
under the name of Fiberfax, and combinations of these. Fiberfax
aluminosilicate fibers
measure about 2-6 micrometers in diameter and about 20-50 micrometers in
length.
Additional examples of inorganic fillers are various carbides, such as silicon
carbide, titanium
carbide, aluminum carbide, zirconium carbide, boron carbide, and aluminum
titanium
carbide; carbonates or carbonate-bearing minerals such as baking soda,
nahcolite, calcite,
hanksite and liottite; and nitrides such as silicon nitride.
[00109] The batch mixture material may also optionally comprise forming aids.
Exemplary forming aids can include soaps, fatty acids, such as oleic, linoleic
acid, etc.,
polyoxyethylene stearate, etc. or combinations thereof. In one embodiment,
sodium stearate
is a preferred forming aid. Optimized amounts of the optional extrusion aid(s)
will depend on
the composition and binder. Other additives that are useful for improving the
extrusion and
curing characteristics of the batch are phosphoric acid and oil. Phosphoric
acid improves the
cure rate and increases adsorption capacity. If included, it is typically
about 0.1 % to 5 wt%
in the batch mixture material. Still further, an oil addition can aid in
extrusion and can result
in increases in surface area and porosity. To this end, an optional oil can be
added in an
amount in the range from about 0.1 to 5 wt. % of the batch mixture material.
Exemplary oils
that can be used include petroleum oils with molecular weights from about 250
to 1000,
containing paraffinic and/or aromatic and/or alicyclic compounds. So called
paraffinic oils
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composed primarily of paraffinic and alicyclic structures are preferred. These
can contain
additives such as rust inhibitors or oxidation inhibitors such as are commonly
present in
commercially available oils. Some useful oils are 3 in I oil from 3M Co., or 3
in 1 household
oil from Reckitt and Coleman Inc., Wayne, N.J. Other useful oils can include
synthetic oils
based on poly (alpha olefins), esters, polyalkylene glycols, polybutenes,
silicones, polyphenyl
ether, CTFE oils, and other commercially available oils. Vegetable oils such
as sunflower oil,
sesame oil, peanut oil, soyabean oil etc. are also useful. Especially suited
are oils having a
viscosity of about 10 to 300 cps, and preferably about 10 to 150 cps.
[00110] The batch mixture material may also optionally comprise natural and/or
synthetic
pore-forming agents. The pore-forming agents may then be removed, for example,
before or
during carbonization and/or activation of the sorbent body. Removal of the
pore-forming
agents can impart certain characteristics to the pore structure of the sorbent
body, such as
voids of various sizes and dimensions.
[00111] In one embodiment, exemplary pore forming agents can include natural
or
synthetic pore-forming agents that, upon carbonization of the sorbent body,
bum out and
leave little or no residue behind in the sorbent body. Examples of such pore-
forming agents
include polymeric materials, such as polymeric beads. Example polymeric
materials, such as
polymeric beads, include polypropylene and polyethylene materials and beads.
In one
embodiment, the batch mixture material may comprise, as a pore-forming agent,
polypropylene, polyester or acrylic powders or fibers that decompose in inert
atmosphere at
high temperature (>400 C) to leave little or no residue.
[00112] Additional pore-forming agents include natural and synthetic starches.
In some
embodiments, when the pore-forming agent is water soluble, such as a starch,
the pore-
forming agent may be removed after curing the sorbent body via water
dissolution before
carbonization. In another embodiment, a suitable pore-forming agent can form
macropores
due to particle expansion. For example, intercalated graphite, which contains
an acid such as
hydrochloric acid, sulfuric acid or nitric acid, will form macropores when
heated, due to the
resulting expansion of the acid. Still further, macropores can also be formed
by dissolving
certain fugitive materials. For example, baking soda, calcium carbonate or
limestone
particles having a particle size corresponding to desired pore size can be
extruded with
carbonaceous materials to form monolithic sorbents. Baking soda, calcium
carbonate or
limestone forms water soluble oxides during the carbonization and activation
processes,
which can subsequently be leached to form macropores by soaking the monolithic
sorbent in
water.
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[00113] In order to obtain a distribution of a metal catalyst throughout the
final sorbent
body, it is highly desired that the carbon-source materials and the metal
catalyst-source
materials are intimately mixed to form the batch mixture material. To that
end, it is desired
in certain embodiments that the various source materials are provided in the
form of fine
powders, or solutions if possible, and then mixed intimately by using an
effective mixing
equipment. When powders are used, they are provided in certain embodiments
with average
size not larger than 100 m, in certain other embodiments not larger than 10
m, in certain
other embodiments not larger than 1 m.
[00114] Various equipment and processes may be used to form the batch mixture
material
into a desired shape of the batch mixture body. For example, extrusion,
injection molding
(include reactive injection molding), compression molding, casting, pressing,
or rapid
prototyping may be used to shape the batch mixture body. The body may be cured
as it is
being shaped, for example, when shaped by injection molding or compression
molding.
Alternatively, the body may be cured after it is shaped, for example, when
shaped by
extrusion, casting, or rapid prototyping. According to some embodiments, the
extruded batch
mixture or cured batch mixture body takes the shape of a monolithic honeycomb
having a
plurality of channels
[00115] Extrusion is especially preferred in certain embodiments for forming
the batch
mixture material into a desired shape of the batch mixture body. Extrusion can
be done by
using standard extruders (ram extruder, single-screw, double-screw, and the
like) and custom
extrusion dies, to make sorbent bodies with various shapes and geometries,
such as
honeycombs, pellets, rods, spaghetti, and the like. Extrusion is particularly
effective for
making monolithic honeycomb bodies having a plurality of empty channels that
can serve as
fluid passageways. Extrusion is advantageous in that it can achieve a highly
intimate mixing
of all the source materials as well during the extrusion process.
[00116] Molds of various shapes and dimensions may also be used for shaping
the batch
material through injection molding, compression molding and casting, all of
which are well-
known shaping techniques. Rapid prototyping, the automatic construction of
physical objects
using solid freeform fabrication, may also be used to shape the batch
material. One
advantage of rapid prototyping is that it may be used to create virtually
almost any shape or
geometric feature. Rapid prototyping comprises obtaining a virtual design, for
example a
computer aided design, converting the design into virtual thin horizontal
cross sections, then
creating each cross section of the design in physical space, one after the
next, until the shape
is completed. One embodiment includes obtaining a virtual design of a shaped
batch material,
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converting the design into virtual thin horizontal cross sections, and
creating each cross
section in physical space from the batch material. One example of rapid
prototyping is 3D
printing.
[00117] In certain embodiments, it is desired that the batch mixture material
comprises an
uncured curable material. In those embodiments, upon forming of the batch
mixture body,
the sorbent body is typically subjected to a curing condition, e.g., heat
treatment, such that the
curable component cures, and a cured batch mixture body forms as a result. The
cured batch
mixture body tends to have better mechanical properties than its non-cured
predecessor, and
thus handles better in down-stream processing steps. Moreover, without the
intention or
necessity to be bound by any particular theory, it is believed that the curing
step can result in
a polymer network having a carbon backbone, which can be conducive to the
formation of
carbon network during the subsequent carbonization and activation steps. In
certain
embodiments the curing is generally performed in air at atmospheric pressures
and typically
by heating the formed batch mixture body at a temperature of from 70 C to 200
C for about
0.5 to about 5.0 hours. In certain embodiments, the batch mixture body is
heated from a low
temperature to a higher temperature in stages, for example, from 70 C, to 90
C, to 125 C, to
150 C, each temperature being held for a period of time. Alternatively, when
using certain
precursors, (e.g., furfuryl alcohol or furan resins) curing can also be
accomplished by adding
a curing additive such as an acid additive at room temperature. The curing
can, in one
embodiment, serve to retain the uniformity of the metal catalyst distribution
in the carbon.
[00118] After formation of the batch mixture body, drying thereof, or optional
curing
thereof, the shaped body is subjected to a carbonization step. For example,
the batch mixture
body (cured or uncured) may be carbonized by subjecting it to an elevated
carbonizing
temperature in an O2-depleted atmosphere. The carbonization temperature can
range from
600 to 1200 C, in certain embodiments from 700 to 1000 C. The carbonizing
atmosphere
can be inert, comprising mainly a non reactive gas, such as N2, Ne, Ar,
mixtures thereof, and
the like. At the carbonizing temperature in an 02-depleted atmosphere, the
organic
substances contained in the batch mixture body decompose to leave a
carbonaceous residue.
As can be expected, complex chemical reactions take place in this high-
temperature step.
Such reactions can include, inter alia:
(i) decomposition of the carbon-source materials to leave a carbonaceous body;
(ii) decomposition of the metal catalyst-source materials;
(iii) decomposition of the sulfur-source materials;
(iv) reactions between the sulfur-source materials and the carbon-source
materials;
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(v) reactions between the sulfur-source materials and carbon;
(vi) reactions between the sulfur-source materials and metal catalyst-source
materials;
(vii) reactions between the metal catalyst-source materials and carbon-source
materials; and
(viii) reactions between the metal catalyst-source materials and carbon.
[00119) The net effect can include, inter alia: (1) re-distribution of the
metal catalyst-
source material and/or the metal catalyst; (2) re-distribution of sulfur; (3)
formation of
elemental sulfur from the sulfur-source material (such as sulfates, sulfites,
and the like); (4)
formation of sulfur-containing compounds from the sulfur-source material (such
as elemental
sulfur); (5) formation of metal catalyst in oxide form; (6) formation of metal
catalyst in
sulfide form; (7) reduction of part of the metal catalyst-source materials.
Part of the sulfur
(especially those in elemental state), and part of the metal catalyst-source
material (such as
KI) may be swept away by the carbonization atmosphere during carbonization.
The result of the carbonization step is a carbonaceous body with sulfur and
metal
catalyst distributed therein. However, this carbonized batch mixture body
typically does not
have the desired specific surface area for an effective sorption of toxic
elements. To obtain
the final sorbent body with a high specific surface area, the carbonized batch
mixture body is
further activated. The carbonized batch mixture body may be activated, for
example, in a
gaseous atmosphere selected from C02, H20, a mixture of CO2 and H20, a mixture
of COZ
and nitrogen, a mixture of H20 and nitrogen, and a mixture of CO2 and another
inert gas, for
example, at an elevated activating temperature in a CO2 and/or H20-containing
atmosphere.
The atmosphere may be essentially pure CO2 or H20 (steam), a mixture of CO2
and H20, or a
combination of CO2 and/or H20 with an inert gas such as nitrogen and/or argon.
Utilizing a
combination of nitrogen and COZ, for example, may result in cost savings. A
COZ and
nitrogen mixture may be used, for example, with COZ content as low as 2% or
more.
Typically a mixture of COZ and nitrogen with a CO2 content of 5-50% may be
used to reduce
process costs. The activating temperature can range from 600 C to 1000 C, in
certain
embodiments from 600 C to 900 C. During this step, part of the carbonaceous
structure of
the carbonized batch mixture body is mildly oxidized:
CO2 (g) + C (s) 4 2C0 (g),
H20 (g) + C (s) 4 H2 (g) + CO (g),
resulting in the etching of the structure of the carbonaceous body and
formation of an
activated carbon matrix defining a plurality of pores on nanoscale and
microscale. The
activating conditions (time, temperature and atmosphere) can be adjusted to
produce the final
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product with the desired specific area and composition. Similar to the
carbonizing step, due
to the high temperature of this activating step, complex chemical reactions
and physical
changes occur. It is highly desired that at the end of the activation step,
the metal catalyst is
distributed throughout the activated carbon matrix. It is highly desired that
at the end of the
activation step, the metal catalyst is distributed substantially homogeneously
throughout the
activated carbon matrix. It is highly desired that at the end of the
activation step, the metal
catalyst is present on at least 30%, at least 40%, at least 50%, at least 60%,
or at least 80% of
the wall surface area of the pores. It is highly desired that at the end of
the activation step,
sulfur is distributed throughout the activated carbon matrix. It is highly
desired that at the
end of the activation step, sulfur is distributed substantially homogeneously
throughout the
activated carbon matrix. It is highly desired that at the end of the
activation step, sulfur is
present on at least 30%, at least 40%, at least 50%, at least 60%, or at least
80% of the wall
surface area of the pores.
[00120] According to certain embodiments the batch mixture material is
selected such
after activation, the sorbent body comprises less than 20% by weight of
inorganic materials
other than carbon, sulfur, and the metal catalyst (in certain embodiments less
than 10%, in
certain other embodiments less than 5%).
[00121] According to certain embodiments, the batch mixture material is
selected such
that, after activation, the sorbent body comprises from 30%-50% by weight of
inorganic
materials other than carbon, sulfur, and the metal catalyst, based on the
total weight of carbon,
sulfur, and the metal catalyst.
1001221 In certain embodiments of the process of the invention, all metal
catalyst-source
materials and all sulfur-source materials are included into the batch mixture
body by in-situ
forming, such as in-situ extrusion, casting, and the like. This process has
the advantages of,
inter alia: (a) avoiding a subsequent step (such as impregnation) of loading a
metal catalyst
and/or sulfur onto the activated carbon body, thus potentially reducing
process steps,
increasing overall process yield, and reducing process costs; (b) obtaining a
more
homogeneous distribution of active sorption sites (metal catalyst and sulfur)
in the sorbent
body than what is typically obtainable by impregnation; and (c) obtaining a
durable and
robust fixation of the metal catalyst and sulfur in the sorbent body, which
can withstand the
flow of the fluid stream to be treated for a long service period. Impregnation
can result in
preferential distribution of impregnated species (such as metal catalyst and
sulfur) on extemal
cell walls, wall surface of large pores (such as those on the micrometer
scale). Loading of
impregnated species onto a high percentage of the wall surfaces of the
nanoscale pores can be
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time-consuming and difficult. Most of the surface area of activated carbon
having high
specific area of from 400 to 2000 m2=g 1 are contributed by the nanoscale
pores. Thus, it is
believed that it is difficult for a typical impregnation step to result in
loading of the
impregnated species onto a majority of the specific area of such activated
carbon material.
Moreover, it is believed that a typical impregnation step can result in a
thick, relatively dense
layer of the impregnated species on the external cell walls and/or wall
surface of large pores,
which blocks the fluid passageways into or out of the smaller pores,
effectively reducing the
sorptive function of the activated carbon. Still further, it is believed that
the fixation of the
impregnated species in a typical impregnation step in the sorbent body is
mainly by relatively
weak physical force, which may be insufficient for prolonged use in fluid
streams.
[00123] Nonetheless, in certain embodiments, it is not necessary that all the
metal catalyst
and/or sulfur is distributed throughout the activated carbon matrix, let alone
substantially
homogeneously. In these embodiments, not all of the metal catalyst-source
materials and
sulfur-source materials are formed in situ into the batch mixture body. It is
contemplated that,
after the activation step, a step of impregnation of certain metal catalysts
and/or sulfur may be
carried out. Alternatively, after the activated step, a step of treating the
activated body by a
sulfur-containing and/or metal catalyst-containing atmosphere may be carried
out. Such
post-activation loading of metal catalyst is especially useful for metals that
cannot withstand
the carbonization and/or carbonization steps, such as those based on
organometallic
compounds, e.g., iron acetylacetonate.
[00124] Once the activated sorbent body of the invention is formed, it may be
subjected to
post-finishing steps, such as pellitizing, grinding, assembling by stacking,
and the like.
Sorbent bodies of various shapes and compositions of the present invention may
then be
loaded into a fixed bed which will be placed into the fluid stream to be
treated.
[00125] Another aspect of the invention is an extruded batch mixture body
comprising:
(I) a carbon-source material comprising an uncured, curable polymeric resin;
(II) particles of sulfur-containing material;
(III) a metal catalyst, either in elemental form or in a chemical compound
comprising the metal;
wherein the metal catalyst is distributed substantially homogeneously in the
material
forming the extruded batch mixture body.
[00126] According to certain embodiments of the extruded batch mixture body of
the
invention, the particles of sulfur-containing material are distributed
substantially
homogeneously in the material forming the extruded batch mixture body.
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[00127] According to certain embodiments of the extruded batch mixture body of
the
invention, the sulfur-containing material comprises at least 50% by mole of
elemental sulfur.
[00128] According to certain embodiments of the extruded batch mixture body of
the
invention, the sulfur-containing material comprises elemental sulfur,
sulfates, sulfites,
sulfides, CS2, and other sulfur-containing compounds.
[00129] According to certain embodiments of the extruded batch mixture body of
the
invention, the extruded batch mixture further comprises:
(IV) a binder material; and/or
(V) an inorganic filler material; and/or
(VI) a lubricant.
[00130] According to certain embodiments, the extruded batch mixture comprises
less
than 20% by weight of inorganic material other than carbon, sulfur-containing
inorganic
material, water and the metal catalyst, in certain embodiments less than 10%,
in certain other
embodiments less than 5%.
[00131] According to certain embodiments, the extruded batch mixture comprises
from
20% to 50% by weight of an inorganic material other than carbon, sulfur-
containing
inorganic material, water and the metal catalyst. In certain embodiments, the
material is a
heat-resistant inorganic material that is chemically stable at 800 C, in
certain other
embodiments at 1000 C.
[00132] According to certain embodiments, the extruded batch mixture comprises
a heat-
resistant inorganic material selected from cordierite, mullite, silica,
alumina, other oxide glass,
other oxide ceramic, other refractory materials, and mixtures and combinations
thereof.
According to certain embodiments, the heat-resistant inorganic material
comprises microscale
pores.
[00133] The present invention is further illustrated by the following non-
limiting
examples.
EXAMPLES
Example 1
[00134] An extrusion composition was formulated with 46% liquid phenolic
resole resin,
1% lubricating oil, 13% cordierite powder, 9% sulfur powder, 7% iron
acetylacetonate, 18%
cellulose fiber, 5% Methocel binder and 1% sodium stearate. This mixture was
compounded
and then extruded. The extruded honeycomb was then dried and cured in air at
150 C
followed by carbonization in nitrogen and activation in carbon dioxide. The
activated carbon
honeycomb samples were then tested for the mercury removal capability. The
test was done
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at 160 C with 22 g=m"3 inlet elemental mercury concentration. The carrier gas
for mercury
contained N2, SO2, 02 and CO2. The gas flow rate was 750 ml/minute. The total
mercury
removal efficiency was 86% while elemental mercury removal efficiency was
100%.
Example 2
[00135] Another extrusion composition was extruded similar to Example 1 but
with 12%
cordierite powder instead of 13% and the iron acetylacetonate at 4% and
potassium iodide at
4% instead of 7% iron acetylacetonate. After activation these samples showed
90% total
mercury removal and 100% elemental mercury removal. The presence of KI in the
composition thus increased the efficiency.
Example 3
[00136] In this experiment the extrusion composition was 59% phenolic resole,
1%
phosphoric acid, 1% oil, 9% sulfur powder, 3% iron oxide, 19% cellulose fiber,
7% methocel
binder and 1% sodium stearate. These samples were extruded, cured carbonized,
activated
and tested as in Example 1 for mercury removal performance. The mercury
removal
efficiency was 87% and 97% for total and elemental mercury, respectively.
Example 4
[00137] In this experiment manganese oxide was used as a metal catalyst source
with the
composition of 6% Mn02, 13% cordierite, 7% sulfur, 19% cellulose fiber, 5%
methocel
binder, 1% sodium stearate, 47% phenolic resole, 1% phosphoric acid and 1%
oil. The
mercury removal efficiency of the samples based on this composition was 92%
and 98% for
total and elemental mercury, respectively.
Example 5
[00138] In this example sulfur was added combined with manganese as MnS
instead of as
elemental sulfur. The composition was 15% cordierite, 10% MnS, 20% cellulose
fiber, 5%
methocel binder, 1% sodium stearate, 47% phenolic resole, and 1% oil.
[00139] On cure, carbonization and activation the mercury removal efficiency
of these
honeycombs was. 84% and 93 % for total and elemental mercury, respectively.
Example 6
[00140] The experiment of Example 5 was repeated but with molybdenum disulfide
(MoS2) in place of MnS. These samples gave mercury removal efficiency of 90%
and 96%
for total and elemental mercury, respectively.
[00141] These Examples show that the sorbent bodies of the invention can
demonstrate
high mercury removal efficiencies. It is expected that the sorbent bodies of
the invention will
also be useful for the sorption of other toxic elements such as cadmium,
chromium, lead,
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barium, beryllium, nickel, cobalt, vanadium, zinc, copper, manganese,
antimony, silver,
thallium, arsenic and selenium from fluids such as flue gases as well as in
coal gasification.
Example 7
[00142] In this experiment the extrusion composition was 14% charcoal, 47%
phenol
resin, 7% sulfur, 7% manganese oxide, 18% cellulose fiber, 5% mythical binder
and 1%
sodium separate. These samples were extruded, cured, carbonized and activated
as in
Example 1.
[00143] The samples were then tested for mercury removal capability. The test
was done
at 140 C with 24 g/m3 inlet elemental mercury concentration. The carrier gas
for mercury
contained N2, HCI, SO2, NO,, 02 and COZ. The gas flow rate was 650m1/minute.
The
mercury removal efficiency was 100% and 99% for both total and elemental
mercury,
respectively. See TABLE II below.
Example 8
[00144] In this example, the extrusion composition was 16% cured sulfur-
containing
phenol resin, 45 % phenol resin, 8% sulfur, 7% manganese oxide, 18% cellulose
fiber, 4%
mythical binder and 1% sodium separate. These samples were extruded, cured,
carbonized
and activated as in Example 1. The activated carbon samples were tested as in
Example 7.
The mercury removal efficiency was 100% and 99% for total and elemental
mercury,
respectively. See TABLE II below. Thus both Examples 7 and 8 achieved
excellent mercury
removal results.
[00145] Various sorbent bodies comprising differing components were tested for
mercury
removal efficiency. Test results are listed in TABLE I below. In all tables
and drawings in
the present application, Hg or Hg(0) means elemental mercury; HgT or Hg(T)
means total
mercury, including elemental and oxidized mercury. Ef~Hg ) or Ef, f(Hg(0))
means the instant
mercury removal efficiency with respect to elemental mercury, and Eff(HgT) or
Eff(Hg(T))
means instant mercury removal efficiency with respect to mercury at all
oxidation states. Just
as described above, Eff(Hg(x)) is calculated as follows:
Eff(Hg(x)) = C - C, x 100%,
Co
where C is the inlet concentration of Hg(x), and Ci is the outlet
concentration of Hg(x),
respectively, at a given test time.
[00146] Comparison of Sample Nos. C and D in TABLE I clearly shows that a
sorbent
material comprising MnS tends have higher performance if it also comprises
elemental sulfur
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in the batch mixture material than if it does not comprise elemental sulfur in
the batch
mixture material.
[00147] FIG. 1 is a diagram comparing the mercury removal capability of a
tested sample
of a sorbent according to the present invention and a comparative sorbent over
time. On the
left vertical axis is the aggregate amount of mercury per unit mass (MSS, mg=g
i) trapped by
the tested samples of the tested sorbents. On the right vertical axis is
instant mercury
removal efficiency of the tested sorbents (Eff(Hg)), which is the instant
total mercury removal
efficiency measured and calculated according to the formula above. On the
horizontal axis is
the time the sample was exposed to the test gas. Part of the Eff(Hg) data in
this figure are
also presented in TABLE III below. The sorbent according to the present
invention
comprises sulfur, in-situ extruded Mn02 as the metal catalyst source and about
45% by
weight of cordierite as an inorganic filler. Sample 2.2 is a comparative
sorbent comprising
no in-situ extruded metal catalyst source, comparable amount of sulfur and
cordierite, and
impregnated FeSO4 and KI. Curves 101 and 103 show the Eff(Hg) and MSS of the
sorbent
according to the present invention, respectively. Curves 201 and 203 show the
Eff(Hg) and
MSS of the comparative sorbent, respectively. As can be seen from this figure
and the data
of TABLE III, the sorbent did not show an abrupt drop of mercury removal
efficiency even
after 250 hours of exposure to a simulated flue gas comprising total mercury
at about 20
Pg=m 3, indicating a fairly large amount of mercury can be trapped by the
sorbent material
before it reaches saturation (or mercury break-through point). The curve 201
and data of
TABLE III show that the comparative sorbent had an abrupt, continuous drop of
instant
mercury removal efficiency within 50 hours until about 70 hours when the test
was
terminated, indicating an early saturation of the sorbent. Curves 103 and 203
overlap to a
certain extent at the early stage of test peiiod, but 203 ends at about 69
hours.
[00148] FIG. 1 shows that the sorbent of this embodiment of the present
invention,
comprising in-situ extruded metal catalyst source, can have much higher
mercury removal
capability, especially on the long term, than sorbent having an impregnated
metal catalyst
sources. Without the intention or necessity to be bound by a particular
theory, it is believed
that the superior performance of the sorbent of the present invention is due
to the more
homogeneous distribution of the metal catalyst, and less blockage of the pores
in the
activated carbon matrix by the metal catalyst.
[00149] FIG. 2 is a diagram showing the inlet mercury concentration (CHgO) and
outlet
mercury concentration (CHgl) of sorbent bodies according to one embodiment of
the present
invention various inlet mercury concentrations. This diagram clearly indicates
that the
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sorbent bodies of certain embodiments of the present invention can be used to
remove
mercury effectively at various mercury concentration (ranging from above 70 to
about 25
,ug'm 3)=
[00150] FIG. 3 is a SEM image of part of a cross-section of a sorbent body
according to
the present invention comprising in-situ extruded metal catalyst. From the
image,
preferential accumulation of metal catalyst or sulfur is not observed. FIG. 4
is a SEM image
of part of a cross-section of a comparative sorbent body comprising post-
activation
impregnated metal catalyst. The clearly visible white layer of material on the
cell wall is the
impregnated metal catalyst. It is believed that this relatively dense layer of
impregnated layer
of metal catalyst can block the entrances into many macroscale and nanoscale
pores inside
the cell walls, reducing the overall performance of the comparative sorbent
body.
[00151] It will be apparent to those skilled in the art that various
modifications and
alterations can be made to the present invention without departing from the
scope and spirit
of the invention. Thus, it is intended that the present invention cover the
modifications and
variations of this invention provided they come within the scope of the
appended claims and
their equivalents.
TABLE I
Sample Test Time Hg' Inlet Eff(Hg ) Eff(HgT)
3 tration (oo) (oo)
No. Metal catalyst-Source (Hours) Concen
( g'm )
A Mn02 20 22 98 92
B MoS2 24 22 96 90
C MnS (with elemental 20 22 98 92
sulfur in batch)
MnS (without
D elemental sulfur in 19 22 93 84
batch)
E Cr203 24 22 98 88
F CuO and Cu2S 19 22 97 90
G Fe203 20 22 97 87
H Iron Acetylacetonate 19 22 100 87
(FeAT)
I FeAT and KI 20 22 100 90
TABLE II
Example Test Time Hg(T), Inlet Hg(0) Removal Hg(T) Removal
No. (Hours) Conc.( g=m 3) Efficiency (%) Efficiency (%)
7 72 24 99 100
8 72 22 99 100
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CA 02686986 2009-11-09
WO 2008/143831 PCT/US2008/006082
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