United States Patent (19)
`Miller
`
`IIIMINIII
`
`US00569.1270A
`11) Patent Number:
`45 Date of Patent:
`
`5,691,270
`Nov. 25, 1997
`
`54 SHAPED LIGNOCELLULOSIC-BASED
`ACTIVATED CARBON
`
`(75) Inventor: James R. Miller, Mt. Pleasant, S.C.
`73) Assignee: Westvaco Corporation, New York,
`N.Y.
`
`(21) Appl. No.: 613,270
`22 Filed:
`Mar 8, 1996
`(51) Int. Cl. ... B01.J. 20/02
`52 U.S. Cl. ............................ 502/416: 502/80; 502/423;
`502/428; 502/429; 502/174; 502/180; 502/182
`(58) Field of Search ..................................... 502/416, 423,
`502/428,429, 80, 174, 180, 182
`References Cited
`U.S. PATENT DOCUMENTS
`6/1987 McCue et al. ............................ 502/80
`4,677,086
`Primary Examiner-Glenn Caldarola
`
`(56)
`
`Assistant Examiner. In Suk Bullock
`Attorney, Agent, or Firm-Terry B. McDaniel; Daniel B.
`Reece, IV; Richard L. Schmalz
`57
`ABSTRACT
`Extruded pellets comprising a majority of activated carbon
`particles and a minority of a binder material are disclosed to
`provide improved performance when processed through
`tumbling equipment while the pellets are in their "green"
`state (i.e., pellets which are freshoff the extruder and contain
`activated carbon), binder material, and water and have not
`been subjected to any thermal processing (drying or
`calcining). The tumbling action both Smooths and densifies
`(i.e., reduces void volume within) the pellet, thereby closing
`any cracks and greatly improving appearance. Improved
`performance results from an ability to increase the weight of
`carbon pellets which can be packed into a fixed volume and
`thereby increase the volumetric working capacity of the bed
`for adsorbing/desorbing vapors. Another benefit is to greatly
`reduce the levels of dust associated with the carbon, both the
`initial dust and the dust attrition.
`8 Claims, 2 Drawing Sheets
`
`
`
`Activated Carbon POWoder
`Binder -
`Water
`
`Calcine
`
`Product
`
` MAHLE-1025
`U.S. Patent No. RE38,844
`
`

`

`U.S. Patent
`US. Patent
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`Nov. 25, 1997
`Nov. 25, 1997
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`Sheet 1 of 2
`Sheet 1 of 2
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`5,691,270
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`U.S. Patent
`US. Patent
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`Nov. 25, 1997
`Nov. 25, 1997
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`Sheet 2 of 2
`Sheet 2 of 2
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`5,691,270
`5,691,270
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`1.
`1
`SHAPED LIGNOCELLULOSIC-BASED
`SHAPED LGNOCELLULOSC-BASED
`ACTIVATED CARBON
`ACTIVATED CARBON
`
`5,691,270
`5,691,270
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`BACKGROUND OF THE INVENTION
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`1. Field of the Invention
`This invention relates to an active carbon pellet prepared
`This invention relates to an active carbon pellet prepared
`by extruding activated lignocellulosic-based carbon with a
`by extruding activated lignocellulosic—based carbon with a
`binder material. More particularly, the invention relates to an
`binder material. More particularly, the invention relates to an
`improved active carbon pellet characterized by low pellet
`improved active carbon pellet characterized by low pellet
`void volume and low dust attrition.
`void volume and low dust attrition.
`2. Description of the Prior Art
`2. Description of the Prior Art
`Granular carbons and carbon pellets are typically used in
`Granular carbons and carbon pellets are typically used in
`columns or beds for gas and vapor systems as well for
`columns or beds for gas and vapor systems as well for
`processing a number of liquids. Such carbons have been
`processing a number of liquids. Such carbons have been
`used in canisters in automobiles through which gasoline tank
`used in canisters in automobiles through which gasoline tank
`and carburetor vapors are directed prior to release to the
`and carburetor vapors are directed prior to release to the
`environment. To qualify for this application, a carbon must
`environment. To qualify for this application, a carbon must
`possess sufficient mechanical strength to withstand the abra
`possess sufficient mechanical strength to withstand the abra-
`sion incident to continued use.
`sion incident to continued use.
`There generally is a direct correlation between the
`There generally is a direct correlation between the
`mechanical strength of the granular activated carbon product
`mechanical strength of the granular activated carbon product
`and the mechanical strength of its precursor raw material.
`and the mechanical strength of its precursor raw material.
`Thus, coal-based active carbon generally exhibits a high
`Thus, coal—based active carbon generally exhibits a high
`mechanical strength and density; whereas, lignocellulosic
`mechanical strength and density; whereas, lignocellulosic-
`based active carbons, derived from a much "softer” precur
`based active carbons, derived fi'om a much “softer” precur-
`sor relative to coal, generally exhibit low mechanical
`sor relative to coal, generally exhibit low mechanical
`strengths and densities.
`strengths and densities.
`Also, gas-adsorbing carbons should be as dense as is
`Also, gas-adsorbing carbons should be as dense as is
`consistent with high adsorption capacity so as not to require
`consistent with high adsorption capacity so as not to require
`a large space for the adsorber. The development of high
`a large space for the adsorber. The development of high
`adsorption capacity during thermal activation, however, is
`adsorption capacity during thermal activation, however, is
`accompanied by a loss of mechanical strength and density;
`accompanied by a loss of mechanical strength and density;
`therefore, some compromise is required in selecting the
`therefore, some compromise is required in selecting the
`degree to which the activation is conducted. So, with igno
`degree to which the activation is conducted. So, with ligno-
`cellulosic precursors (or, for lignocellulosic-based active
`cellulosic precursors (or, for lignocellulosic-based active
`carbons), the problem is compounded.
`carbons), the problem is compounded
`Several approaches have been taken to address the prob
`Several approaches have been taken to address the prob-
`lem of low mechanical strength and density of
`lem of low mechanical strength and density of
`lignocellulosic-based active carbons. In U.S. Pat. No. 3,864,
`lignocellulosic—based active carbons. In US. Pat. No. 3,864,
`277, Kovach emphasizes the binder additive in teaching the
`277, Kovach emphasizes the binder additive in teaching the
`phosphoric acid activation of wood, straw, or low-rank
`phosphoric acid activation of wood, straw, or low—rank
`brown coals in the presence of a carbonaceous binder
`brown coals in the presence of a carbonaceous binder
`material such as lignosulfonates and polyvinyl alcohol,
`material such as lignosulfonates and polyvinyl alcohol,
`followed by forming solid granular shaped particles from the
`followed by forming solid granular shaped particles from the
`mixture, and heat-treating at less than 650° C. to give a
`mixture, and heat-treating at less than 650° C. to give a
`granular product having a ball-pan hardness of greater than
`granular product having a ball-pan hardness of greater than
`85%. Given the teaching of Kovach and employing the
`85%. Given the teaching of Kovach and employing the
`knowledge of the relationship of precursor mechanical
`lmowledge of the relationship of precursor mechanical
`strength and density with those characteristics of the active
`strength and density with those characteristics of the active
`carbon product, MacDowall (in U.S. Pat. No. 5,162.286)
`carbon product, MacDowall (in U.S. Pat. No. 5,162,286)
`teaches increasing lignocellulosic-based active carbon den
`teaches increasing lignocellulosic-based active carbon den-
`sity by the use of young carbonaceous vegetable products
`sity by the use of young carbonaceous vegetable products
`high (>30%) in natural binding agent, such as nut shell, fruit
`high (>30%) in natural binding agent, such as nut shell, fruit
`stone, almond shell, and coconut shell, as precursors for
`stone, almond shell, and coconut shell, as precursors for
`treatment with phosphoric acid followed by carbonization.
`treatment with phosphoric acid followed by carbonization.
`A third approach, which relates to the present invention,
`A third approach, which relates to the present invention,
`is taught by McCue et al. in US Pat. No. 4,677,086. To
`is taught by McCue et al. in U.S. Pat. No. 4,677,086. To
`achieve, in a wood-based active carbon, the mechanical
`achieve, in a wood-based active carbon, the mechanical
`strength and product density approaching that achieved with
`strength and product density approaching that achieved with
`coal-based products, McCue et al. teach extruding an active
`coal-based products, McCue et a1. teach extruding an active
`wood-based carbon with bentonite clay, followed by calcin
`wood-based carbon with bentonite clay, followed by calcin-
`ing the extruded active carbon/clay pellets. This technology
`ing the extruded active carbon/clay pellets. This technology
`65
`has been the basis for the commercial products NUCHARO)
`has been the basis for the commercial products NUCHAR®
`65
`BAX-950 and NUCHARGE BAX-1100 marketed by West
`BAX-950 and NUCHAR® BAX-1100 marketed by West-
`vaco Corporation.
`vaco Corporation.
`
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`Carbons of suitable mechanical strength and density for
`Carbons of suitable mechanical strength and density for
`use in an evaporative emission control device (automotive
`use in an evaporative emission control device (automotive
`canister) for adsorbing gasoline vapors preferably also
`canister) for adsorbing gasoline vapors preferably also
`exhibit a butane working capacity of about 10 to about 17
`exhibit a butane working capacity of about 10 to about 17
`g/100 cc and an apparent density from about 0.25 to about
`g/100 cc and an apparent density from about 0.25 to about
`0.40 g/cc.
`0.40 g/cc.
`In addition to gas column (or, packed bed) requirements
`In addition to gas column (or, packed bed) requirements
`for high mechanical strength and high density, it is also
`for high mechanical strength and high density, it is also
`desirable to reduce the bed void volumein order to maxi-
`desirable to reduce the bed void volume in order to maxi
`mize the carbon content of the bed, and subsequently
`mize the carbon content of the bed, and subsequently
`maximize the adsorptive capacity. This is primarily deter
`maximize the adsorptive capacity. This is primarily deter-
`mined by the shape of the granular or pelleted carbon. In
`mined by the shape of the granular or pelleted carbon. In
`fact, because of the irregular shape of granular carbon, more
`fact, because of the irregular shape of granular carbon, more
`regularly shaped carbon pellets are preferred for their better
`regularly shaped carbon pellets are preferred for their better
`15 n
`"packing.” However, as a result of uneven cutting of the
`15
`packing.” However, as a result of uneven cutting of the
`extrudate to form the pellets, the pellets are, in fact, irregu
`extrudate to form the pellets, the pellets are, in fact, irregu-
`larly shaped, and fissures and cavities often appear along the
`larly shaped, and fissures and cavities often appear along the
`pellet surface. This creates two problems. The resulting
`pellet surface. This creates two problems. The resulting
`irregularities in shape prevent optimization of bed (or
`irregularities in shape prevent optimization of bed (or
`column) packing and detract from maximizing the carbon
`column) packing and detract from maximizing the carbon
`content for a given pellet volume. In addition, the surface
`content for a given pellet volume. In addition, the surface
`irregularities are often removed from the pellet due to
`irregularities are often removed from the pellet due to
`abrasion. These material losses, in addition to debris caused
`abrasion. These material losses, in addition to debris caused
`by cutting the pellets to size, present another problem: dust.
`by cutting the pellets to size, present another problem: dust.
`Typically, dusting due to abrasion, or dust attrition, may be
`Typically, dusting due to abrasion, or dust attrition, may be
`retarded or precluded by spraying a coating on the surface of
`retarded or precluded by spraying a coating on the surface of
`the pellet. Invariably, this remedy is at the expense of butane
`the pellet. Invariably, this remedy is at the expense of butane
`working capacity; thereby providing another trade-off for
`working capacity; thereby providing another trade-ofi for
`the working life of the active carbon material.
`the working life of the active carbon material.
`Besides having a product which may appear to
`Besides having a product which may appear to
`disintegrate, attrited dustin a packed bed, such as a column
`disintegrate, attrited dust in a packed bed, such as a column
`or an automotive canister, can fill the bed voids to create
`or an automotive canister, can fill the bed voids to create
`high pressure drops and impede the flow-through of vapors
`high pressure drops and impede the flow-through of vapors
`to be treated. A particular problem in the automotive appli
`to be treated. A particular problem in the automotive appli—
`cation is concern that the dust will act to interfere with
`cation is concern that the dust will act to interfere with
`various sensing devices connected to the canister to monitor
`various sensing devices connected to the canister to monitor
`performance, resulting either in false readings or in failure
`performance, resulting either in false readings or in failure
`of the sensing devices altogether.
`of the sensing devices altogether.
`Therefore, an object of this invention is to provide an
`Therefore, an object of this invention is to provide an
`improved lignocellulosic-based activated carbon pellet of a
`improved lignocellulosic-based activated carbon pellet of a
`smoother surface and more uniform shape which provides
`smoother sm‘face and more uniform shape which provides
`optimal bed packing, exhibits increased density, and is less
`optimal bed packing, exhibits increased density, and is less
`susceptible to dust attrition. An additional object of this
`susceptible to dust attrition. An additional object of this
`invention is to provide an improved method of manufacture
`invenn'on is to provide an improved method of manufacture
`of such activated carbon pellet.
`of such activated carbon pellet.
`BRIEF DESCRIPTION OF THE DRAWINGS
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 shows a block flow diagram of the invention
`FIG. 1 shows a block flow diagram of the invention
`process wherein tumbling is carried out on the green
`process wherein tumbling is carried out on the green
`extrudate, followed by drying and calcination.
`extrudate, followed by drying and calcination.
`FIG. 2 shows a block flow diagram of the invention
`FIG. 2 shows a block flow diagram of»: the invention
`process whereby tumbling is carried out on the green
`process whereby tumbling is carried out on the green
`extrudate as it is being dried, followed by calcination.
`extrudate as it is being dried, followed by calcination.
`SUMMARY OF THE INVENTION
`SUMMARY OF THE INVENTION
`The object of the invention is achieved in the discovery
`The object of the invention is achieved in the discovery
`that extruded pellets comprising a major portion of activated
`that extruded pellets comprising a major portion of activated
`carbon particles and a minor portion of inorganic or organic
`carbon particles and a minor portion of inorganic or organic
`binder provides improved performance when processed
`binder provides improved performance when processed
`through tumbling equipment while the pellets are in their
`through tumbling equipment while the pellets are in their
`"green" state. Green pellets are those which are fresh off the
`“green” state. Green pellets are those which are fi'esh off the
`extruder and contain activated carbon, binder, and moisture
`extruder and contain activated carbon, binder, and moisture
`(from 50-70% water, by weight) and have not been sub
`(from 50—70% water, by weight) and have not been sub-
`jected to any thermal processing (i.e., drying or calcining).
`jected to any thermal processing (i.e., drying or calcining).
`The tumbling action both smooths and densifies (i.e.,
`The tumbling action both smooths and densities (i.e.,
`reduces interparticle voids within) the pellet, thereby
`reduces interparticle voids within) the pellet,
`thereby
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`sealing, or otherwise closing, any cracks and greatly improv
`sealing, or otherwise closing, any cracks and greatly improv—
`ing appearance. (Interestingly, debris caused by cutting the
`ing appearance. (Interestingly, debris caused by cutting the
`pellets to size is assimilated by the tumbling pellets.)
`pellets to size is assimilated by the tumbling pellets.)
`Improved performance results from an ability to increase the
`Improved performance results from an ability to increase the
`weight of carbon pellets which can be packed into a fixed
`weight of carbon pellets which can be packed into a fixed
`volume and thereby increase the volumetric working capac
`volume and thereby increase the volumetric working capac-
`ity of the bed for adsorbing/desorbing vapors. Another
`ity of the bed for adsorbing/desorbing vapors. Another
`benefit is to greatly reduce the levels of dust associated with
`benefit is to greatly reduce the levels of dust associated with
`the carbon, both the initial dust and the dust attrition.
`the carbon, both the initial dust and the dust attrition.
`DESCRIPTION OF THE PREFERRED
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT(S)
`EMBODIMENT(S)
`The process steps for the alternative embodiments of the
`The process steps for the alternative embodiments of the
`invention process are set forth in the drawings. FIG. 1 shows
`invention process are set forth in the drawings. FIG. 1 shows
`that activated carbon powder (produced from grinding
`that activated carbon powder (produced from grinding
`granular lignocellulosic-based activated carbon), binder
`granular lignocellulosic-based activated carbon), binder
`material, and water are sequentially mulled, extruded,
`material, and water are sequentially mulled, extruded,
`tumbled, dried, and calcined to produce the invention active
`tumbled, dried, and calcined to produce the invention active
`carbon pellet. FIG. 2 shows the activated carbon powder,
`carbon pellet. FIG. 2 shows the activated carbon powder,
`binder material, and water to be sequentially mulled,
`binder material, and water to be sequentially mulled,
`extruded, dried while tumbling, and calcined to produce the
`extruded, dried while tumbling, and calcined to produce the
`invention active carbon pellet, The process steps are
`invention active carbon pellet. The process steps are
`described in greater detail in the Examples which follow.
`described in greater detail in the Examples which follow.
`Also, with the exception of the invention improvement, the
`Also, with the exception of the invention improvement, the
`process generally follows the teaching of U.S. Pat. No.
`process generally follows the teaching of US. Pat. No.
`4,677,086, which disclosure is incorporated herein by ref
`4,677,086, which disclosure is incorporated herein by ref-
`erence.
`eece
`Basically, the blend of activated lignocellulosic-based
`Basically,
`the blend of activated lignocellulosic-based
`carbon, binder material, and water are mixed and then fed
`carbon, binder material, and water are mixed and then fed
`through an extrusion device. The generally continuous
`through an extrusion device. The generally continuous
`extrudate is cut at consistent intervals to produce a cylin
`extrudate is cut at consistent intervals to produce a cylin-
`drical pellet, relatively uniform in length and diameter. The
`drical pellet, relatively uniform in length and diameter. The
`invention process improvement involves taking these
`invention process improvement
`involves taking these
`"green" pellets soon after they are generated and subjecting
`“green” pellets soon after they are generated and subjecting
`them to a tumbling process for a period of time sufficient to
`them to a tumbling process for a period of time suflicient to
`produce a pellet that, upon subsequent drying and/or
`produce a pellet
`that, upon subsequent drying and/or
`calcination, exhibits a pellet void fraction of less than 0.19
`calcination, exhibits a pellet void fraction of less than 0.19
`(determined as the actual pellet density divided by the base
`(determined as the actual pellet density divided by the base
`pellet density and subtracted from 1) and a dust attrition rate
`pellet density and subtracted from 1) and a dust attrition rate
`of less than 1.2 mg/100 cc/minute. In a preferred embodi
`of less than 1.2 mg/lOO cclminute. In a preferred embodi-
`ment of the invention composition, the pellet void fraction
`ment of the invention composition, the pellet void fraction
`is less than 0.17 and the dust attrition rate is 1.0 mg/lOO
`is less than 0.17 and the dust attrition rate is 1.0 mg/100
`cc/minute. In the most preferred embodiment, the pellet void
`cclminute. In the most preferred embodiment, the pellet void
`fraction is less than 0.15 and the dust attrition rate is less
`fraction is less than 0.15 and the dust attrition rate is less
`than 0.8 mg/100 cc/minute. In particular, it has been found
`than 0.8 mg/lOO cclminute. In particular, it has been found
`that the rambling step is effective to provide the improved
`that the rambling step is effective to provide the improved
`composition of the invention if it is performed in lieu of
`composition of the invention if it is performed in lieu of
`immediately drying the green pellets in additional equip
`immediately drying the green pellets in additional equip—
`ment.
`ment.
`It is envisioned that the moisture level of the green pellets
`It is envisioned that the moisture level of the green pellets
`is important in the effectiveness of the tumbling step, and
`is important in the eifectiveness of the tumbling step, and
`that a critical moisture level may exist below which densi
`that a critical moisture level may exist below which densi-
`fication and reduction of dust levels may not occur. As a
`fication and reduction of dust levels may not occur. As a
`result, in an additional embodiment of the invention, the
`result, in an additional embodiment of the invention, the
`tumbling equipment can also be used to dry the green
`tumbling equipment can also be used to dry the green
`pellets, if the dryingrate is kept to a level low enough to give
`pellets. if the drying rate is kept to a level low enough to give
`a sumcient residence time before the critical moisture level
`a sufficient residence time before the critical moisture level
`is reached. The critical moisture level is in the range of
`is reached. The critical moisture level is in the range of
`50-70% water, by weight. A preferred moisture level is
`50—70% water, by weight. A preferred moisture level is
`55-65% water, by weight. The most preferred moisture level
`55—65% water, by weight. The most preferred moisture level
`for the tumbling operation of the green pellets is 58-62%
`for the tumbling operation of the green pellets is 58—62%
`water, by weight.
`water, by weight.
`Any commercial tumbling equipment, based on the nature
`Any cormnercial tumbling equipment, based on the nature
`and volume of material to be treated and whether the process
`and volume of material to be treated and whether the process
`is to be batch or continuous, is considered suitable for use in
`is to be batch or continuous, is considered suitable for use in
`the invention process. Equipment which would be expected
`the invention process. Equipment which would be expected
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`to produce the beneficial product properties in the invention
`to produce the beneficial product properties in the invention
`composition are considered to be equivalent to the equip
`composition are considered to be equivalent to the equip-
`ment employed in the examples below. The tumbling opera
`ment employed in the examples below. The tumbling opera-
`tion may be employed for up to 30 minutes. The process is
`tion may be employed for up to 30 minutes. The process is
`considered to ofler little or no benefit once the moisture level
`considered to offer little or no benefit once the moisture level
`in the pellets is significantly reduced (<50%).
`in the pellets is significantly reduced (60%).
`The lignocellulosic material precursor to the
`The lignocellulosic material precursor to the
`lignocellulosic-based active carbon used in the invention
`lignocellulosic-based active carbon used in the invention
`process to form the invention composition is selected from
`process to form the invention composition is selected from
`the group consisting of wood chips, wood flour, sawdust,
`the group consisting of wood chips, wood flour, sawdust,
`coconut shell, nut shells, fruit pits, kernal, olive stone, and
`coconut shell, nut shells, fruit pits, kernal, olive stone, and
`almond shell.
`almond shell.
`The binder materials include bentonite clays or chemi-
`The binder materials include bentonite clays or chemi
`cally modified bentonite clays. Preferred binders are sodium
`cally modified bentonite clays. Preferred binders are sodium
`bentonite and calcium bentonite.
`bentonite and calcium bentonite.
`In the Examples to follow, the various analyses were
`In the Examples to follow, the various analyses were
`performed in measurements determining the benefits of the
`performed in measurements determining the benefits of the
`invention product and process:
`invention product and process:
`Apparent Density (AD)-ISO No. 960-050: weight of dry
`Apparent Density (AD)—ISO No. 960-050: weight of dry
`carbon per unit volume of the carbon bed;
`carbon per unit volume of the carbon bed;
`Butane Working Capacity (BWC)-ISO No. 960-080:
`Butane Working Capacity (BWC)—ISO No. 960-080:
`weight of butane purged from a sample of dried carbon after
`weight of butane purged from a sample of dried carbon after
`it had been saturated with butane per unit volume of the
`it had been saturated with butane per unit volume of the
`carbon bed;
`carbon bed;
`Dusting Attrition (DA)-ISO No. 960–380: weight of dust
`Dusting Attrition (DA)-ISO No. 960-380: weight of dust
`attrited from a 100 ml sample of carbon per unit time;
`attrited from a 100 ml sample of carbon per unit time;
`Initial Dust (ID)- same as dusting attrition: Weight of dust
`Initial Dust (ID)- same as dusting attrition: weight of dust
`initially present on a 100 ml sample of carbon prior to
`initially present on a 100 ml sample of carbon prior to
`attrition test;
`attrition test;
`Actual Pellet Density (APD); weight of dry carbon per
`Actual Pellet Density (APD); weight of dry carbon per
`unit volume of entire carbon pellet, determined using mer
`unit volume of entire carbon pellet, determined using mer—
`cury porosimetry;
`cury porosimetry;
`Base Pellet Density (BPD); weight of dry carbon per unit
`Base Pellet Density (BPD); weight of dry carbon per unit
`volume of carbon pellet including only pore space less than
`volume of carbon pellet including only pore space less than
`0.5 microns equivalent diameter, determined using mercury
`0.5 microns equivalent diameter, determined using mercury
`porosimetry;
`porosimetry;
`Bed Void Fraction (BVF): volume of space between
`Bed Void Fraction (BVF): volume of space between
`carbon pellets per unit volume of carbon bed, determined by
`carbon pellets per unit volume of carbon bed, determined by
`the equation 1-(AD/APD); and
`the equation l-(AD/APD); and
`Pellet Void Fraction (PVF) (pellet interparticle void
`Pellet Void Fraction (PVF) (pellet
`interparticle void
`fraction): volume of space within a carbon pellet including
`fraction): volume of space within a carbon pellet including
`only pore space greater than 0.5 microns equivalent diameter
`only pore space greater than 0.5 microns equivalent diameter
`per unit volume of entire carbon pellet, determined by the
`per unit volume of entire carbon pellet, determined by the
`equation 1-(APD/BPD).
`equation 1-(APD/BPD).
`The invention process and composition are further
`The invention process and composition are further
`described in the following specific examples:
`described in the following specific examples:
`EXAMPLE 1
`EXAMPLE 1.
`Ground wood—based activated carbon was mixed with
`Ground wood-based activated carbon was mixed with
`bentonite clay and water in a muller mixer. The dry basis
`bentonite clay and water in a muller mixer. The dry basis
`clay concentration was 14 wt %. The mixture was mulled
`clay concentration was 14 wt %. The mixture was mulled
`until it reached a consistency which could be extruded. It
`until it reached a consistency which could be extruded. It
`was extruded in a twin screw auger extruder through a die
`was extruded in a twin screw auger extruder through a die
`plate containing 2 mm holes and cut as it exited the die plate
`plate containing 2 mm holes and cut as it exited the die plate
`into "green” pellets ranging in length from 2-6 mm. The
`into “green” pellets ranging in length from 2—6 mm. The
`green pellets had amoisture content of approximately 55-60
`green pellets had a moisture content of approximately 55—60
`wt % (wet basis). Following extrusion, a portion of the green
`wt % (wet basis). Following extrusion, a portion of the green
`pellets was loaded into a rotating disc pan pelletizer in order
`pellets was loaded into a rotating disc pan pelletizer in order
`to tumble the pellets. The pan was angled above the hori
`to tumble the pellets. The pan was angled above the hori-
`zontal to retain the pellets and rotated at 15 rpm for 5
`zontal to retain the pellets and rotated at 15 rpm for 5
`minutes. After 5 minutes, pellets were collected from the pan
`minutes. After 5 minutes, pellets were collected from the pan
`and dried in a batch, convection oven. The portion of green
`and dried in a batch, convection oven. The portion of green
`pellets which was not tumbled was also dried in the same
`pellets which was not tumbled was also dried in the same
`oven for the same amount of time. The two batches of dried
`oven for the same amount of time. The two batches of dried
`pellets were calcined separately to 1200° F in a batch
`pellets were calcined separately to 1200° F.
`in a batch
`
`

`

`5,691,270
`5,691,270
`
`6
`6
`
`5
`5
`indirect-fired rotary furnace for 15 minutes. Following
`indirect-fired rotary furnace for 15 minutes. Following
`calcination, they were discharged and cooled separately
`calcination, they were discharged and cooled separately
`under a nitrogen purge prior to analysis.
`under a nitrogen purge prior to analysis.
`The pertinent properties of each product are shown in
`The pertinent properties of each product are shown in
`Table I. From the data, it can be seen that BWC increased
`Table I. From the data, it can be seen that BWC increased
`7.5%, apparent density increased 9.2%, initial dust was
`7.5%, apparent density increased 9.2%,
`initial dust was
`reduced by 70%, and dust attrition was reduced by 45%
`reduced by 70%, and dust attrition was reduced by 45%
`(from 2.16 to 1.19).
`(from 2.16 to 1.19).
`
`TABLE I
`
`TABLE I
`DA
`1])
`BWC
`AD
`DA
`D
`BWC
`AD
`
`(g/100 cc)
`(glee)
`(mg)
`(mg/min)
`Batch I.D.
`(g/100 cc)
`(gfcc)
`(mg)
`(mg/min)
`Batch I.D.
`095-0342
`10.7
`0.336
`58.8
`2.16
`C-95-0342
`10.7
`0.336
`58.8
`2.16
`-Not Tumbled-
`-Not Tumbled
`C-950343
`11.5
`0.367
`17.8
`1.19
`C-95.0343
`11.5
`0.367
`17.8
`1.19
`-Tumbled—
`
`-Tumbled
`
`10
`10
`
`15
`15
`
`20
`20
`
`25
`25
`
`30
`30
`
`EXAMPLE 2
`EXAMPLE 2
`Ground lignocellulosic-based activated carbon was mixed
`Ground lignocellulosic-based activated carbon was mixed
`with bentonite clay and water in a Muller mixer. The dry
`with bentonite clay and water in a Muller mixer. The dry
`basis clay concentration was 9 wt %. The mixture was
`basis clay concentration was 9 wt %. The mixture was
`mulled until it reached a consistency which could be
`mulled until it reached a consistency which could be
`extruded. It was extruded in a single screw auger extruder
`extruded. It was extruded in a single screw auger extruder
`through a die plate containing 2 mmholes and cut as it exited
`through a die plate containing 2 mmholes and cut as it exited
`the die plate into "green” pellets ranging in length from 2-6
`the die plate into “green” pellets ranging in length from 2—6
`mm. The green pellets had a moisture content of approxi
`mm. The green pellets had a moisture content of approxi-
`mately 55-60 wt % (wet basis). Following extrusion, a
`mately 55—60 wt % (wet basis). Following extrusion, a
`portion of the green pellets was taken and loaded into a 24
`portion of the green pellets was taken and loaded