(19) United States
`(12) Reissued Patent
`Hiltzik et al.
`
`(54) METHOD FOR REDUCING EMISSIONS
`FROM EVAPORATIVE EMISSIONS
`CONTROL SYSTEMS
`
`(75) Inventors: Laurence H. Hiltzik, Charleston, SC
`(US); Jacek Z. Jaqiello, Boynton
`Beach, FL (US); Edward Don Tolles,
`Charleston, SC (US); Roger S.
`Williams, Lexington, VA (US)
`(73) Assignee: MeadWestvaco Corporation,
`Stamford, CT (US)
`
`(21) Appl. No.: 10/690,298
`(22) Filed:
`Oct. 21, 2003
`
`Related U.S. Patent Documents
`
`6,540,815
`Apr. 1, 2003
`10/100,362
`Mar. 18, 2002
`
`Reissue of:
`(64) Patent No.:
`Issued:
`Appl. No.:
`Filed:
`U.S. Applications:
`(60) Provisional application No. 60/335,897, filed on Nov. 21,
`2001.
`(51) Int. Cl." ......................... F02M 33/02; B01D 53/04
`(52) U.S. Cl. ............................. 95/146; 95/900; 96/132;
`96/133; 123/519
`(58) Field of Search ............................ 95/90, 146, 148,
`95/900–903; 96/132, 133, 147; 502/416;
`123/518, 519
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,677,086 A 6/1987 McCue et al.
`4,869,739 A 9/1989 Kanome et al.
`4,894,072 A 1/1990 Turner et al.
`5,204,310 A 4/1993 Toles et al.
`5,206.207 A 4/1993 Tolles
`(Continued)
`
`
`
`USOORE38844E
`
`US RE38,844 E
`(10) Patent Number:
`Oct. 25, 2005
`(45) Date of Reissued Patent:
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`EP
`JP
`JP
`KR
`WO
`WO
`
`1094032
`11131.63
`1033921.8
`O2256989
`O12826
`WO 9201585
`WOO162367
`
`4/2001
`7/2001
`12/1998
`11/2002
`2/2002
`2/1992
`8/2001
`
`OTHER PUBLICATIONS
`Williams, R. S. and C. R. Clontz. “Impact and Control of
`Canister Bleed Emissions' Covington Virginia, Society of
`Automotive Engineers, Inc. 2001.
`Primary Examiner Frank M. Lawrence
`(74) Attorney, Agent, or Firm Terry B. McDaniel; Daniel
`B. Reece, IV
`ABSTRACT
`(57)
`Disclosed is a method for Sharply reducing diurnal breathing
`loSS emissions from automotive evaporative emissions con
`trol Systems by providing multiple layers, or Stages, of
`adsorbents. On the fuel Source-side of an emissions control
`System canister, high working capacity carbons are preferred
`in a first canister (adsorb) region. In Subsequent canister
`region(s) on the vent-side, the preferred adsorbent should
`exhibit a flat or flattened adsorption isotherm on a volumet
`ric basis and relatively lower capacity for high concentration
`Vapors as compared with the fuel Source-Side adsorbent.
`Multiple approaches are described for attaining the preferred
`properties for the Vent-Side canister region. One approach is
`to use a filler and/or voidages as a volumetric diluent for
`flattening an adsorption isotherm. Another approach is to
`employ an adsorbent with the desired adsorption isotherm
`properties and to process it into an appropriate shape or form
`without necessarily requiring any special provision for dilu
`tion. The improved combination of high working capacity
`carbons on the fuel Source-Side and preferred lower working
`capacity adsorbent on the vent-side provides Substantially
`lower diurnal breathing emissions without a significant loSS
`in working capacity or increase in flow restriction compared
`with known adsorbents used in canister configurations for
`automotive emissions control Systems.
`
`54 Claims, 3 Drawing Sheets
`
` MAHLE-1001
`U.S. Patent No. RE38,844
`
`

`

`US RE38,844 E
`US RE38,844 E
`
`Page 2
`Page 2
`
`US. PATENT DOCUMENTS
`U.S. PATENT DOCUMENTS
`Haruta et a1.
`5/1993
`5/1993
`Haruta et al.
`Tolles et a1.
`8/1993
`Tolles et al.
`8/1993
`Yan
`10/1993
`10/1993
`Yan
`Matthews et a1.
`1/1994
`Matthews et al.
`1/1994
`Dimitri
`4/1994
`Dimitri
`4/1994
`McCue et a1.
`6/1994
`McCue et al.
`6/1994
`8/1994
`Kasuya et a1.
`Kasuya et al.
`8/1994
`Arai
`10/1994
`Arai
`10/1994
`Krohm
`1/1995
`1/1995
`Krohm
`4/1995
`Reddy
`Reddy
`4/1995
`Baker
`5/1995
`5/1995
`Baker
`Wakashiro et a1.
`10/1995
`10/1995
`Wakashiro et al.
`Yamazaki et a1.
`10/1995
`10/1995
`Yamazaki et al.
`Yamazaki et a1.
`10/1995
`10/1995
`Yamazaki et al.
`12/1995
`Hyodo et a1.
`Hyodo et al.
`12/1995
`Hunt et a1.
`1/1996
`Hunt et al.
`1/1996
`
`>>>>>>>>>>>>>>>>
`
`5,207,808
`5,207,808
`5,238,470
`5,238,470
`5,250,491
`5,250,491
`5,276,000
`5,276,000
`5,304,527
`5,304,527
`5,324,703
`5,324,703
`5,337,721
`5,337,721
`5,355,861
`5,355,861
`5,377,644
`5,377,644
`5,408,976
`5,408,976
`5,416,056
`5,416,056
`5,456,236
`5,456,236
`5,456,237
`5,456,237
`5,460,136
`5,460,136
`5,477,836
`5,477,836
`5,482,023
`5,482,023
`
`>>>>>>>>>>>>>
`
`5,538,932
`5,538.932
`5,564,398
`5,564,398
`5,687,697
`5,687,697
`5,691,270
`5,691,270
`5,736,481
`5,736,481
`5,736,485
`5,736,485
`5,863,858
`5,863,858
`5,914,294
`5,914,294
`5,914,457
`5,914,457
`5,931,141
`5,931,141
`5,957,114
`5,957,114
`6,098,601
`6,098.601
`6,136,075
`6,136,075
`6,171,373
`6,171,373
`6,279,548
`6.279,548
`6,284,705
`6,284,705
`6,488,748
`6,488.748
`
`7/1996
`7/1996
`10/1996
`10/1996
`11/1997
`11/1997
`11/1997
`11/1997
`4/1998
`4/1998
`4/1998
`4/1998
`1/1999
`1/1999
`6/1999
`6/1999
`6/1999
`6/1999
`8/1999
`8/1999
`9/1999
`9/1999
`8/2000
`8/2000
`10/2000
`10/2000
`1/2001
`1/2001
`8/2001
`8/2001
`9/2001
`9/2001
`12/2002
`12/2002
`
`Yan et a1.
`Yan et al.
`Maeda et a1.
`Maeda et al.
`Ishikawa
`Ishikawa
`Miller
`Miller
`Miller
`Miller
`Miller
`Miller
`Miller et a1.
`Miller et al.
`Park et a1.
`Park et al.
`Itakura et a1.
`Itakura et al.
`Chino
`Chino
`Johnson et a1.
`Johnson et al.
`Reddy
`Reddy
`Bragg et a1.
`Bragg et al.
`Park et a1.
`Park et al.
`Reddy
`Reddy
`Park et a1.
`Park et al.
`Yamafuji et a1.
`Yamafuji et al.
`
`

`

`1///
`
`

`

`US. Patent
`
`U.S. Patent
`
`Oct. 25, 2005
`
`Oct. 25, 2005
`
`Sheet 2 of 3
`Sheet 2 0f 3
`
`US RE38,844 E
`
`US RE38,844 E
`
`FIGURE 2
`
`
`
`1
`
`9%
`
`2 3 %,
`
`&
`IIIII
`l-IIIIIIII
`
`
`IIII-IIIIIIIIIIII700.,_66.6.99.0.
`finflfiflfiuufl"§§§Q§O§Q§Q§§Q§¢¢QQQ
`
`5555555559...OO§O§§§.§.§.§QQQ
`IVIIIIIII1...¢¢§.§O§..09...
`
`
`
`IIIIIIIIIV......§¢§900.9:0...‘
`
`
`
`IIIIIIIIIIV..*‘“§§Q§Q...0...‘
`
`.3.".3aura.§flfln§
`IHIHIHIHIHIHIHIHI”v:§§§¢¢“§§¢¢§“§§.§fi
`
`
`qrytpypyry y QPvP
`(4-00000d
`()00d
`0000000-00
`400-0-0-0004)
`0.4000000
`0-0--000000
`(84-8-000000
`4-0-0000000
`{) 0000000
`99.999999
`4800
`{}
`d00
`(800
`4)
`4)
`{}
`d
`
`d i i i
`i
`#0699:
`
`A.A.
`
`
`

`

`U.S. Patent
`US. Patent
`
`Oct. 25, 2005
`Oct. 25, 2005
`
`Sheet 3 of 3
`Sheet 3 0f3
`
`US RE38,844 E
`US RE38,844 E
`
`FIGURE 3
`FIGURE 3
`
`n-Butane Adsorption isotherm at 25°C
`n-Butane Adsorption lsotherm at 25°C
`
`
`
`18O
`180
`160 -
`160 '
`
`BAX 1500
`
`
`
`Massadsorbed,g/L
`
`N O
`
`140
`140
`
`120
`'120
`
`1 OO
`100
`
`4>onOo<03
`4.6
`
`2 O
`
`10
`1
`10
`n-Butane Vapor Concentration, volume percent
`n-Butane Vapor Concentration, volume percent
`
`100
`100
`
`

`

`1
`1
`METHOD FOR REDUCING EMISSIONS
`METHOD FOR REDUCING EMISSIONS
`FROM EVAPORATIVE EMISSIONS
`FROM EVAPORATIVE EMISSIONS
`CONTROL SYSTEMS
`CONTROL SYSTEMS
`
`Matter enclosed in heavy brackets
`appears in the
`Matter enclosed in heavy brackets [ ] appears in the
`original patent but forms no part of this reissue specifi
`original patent but forms no part of this reissue specifi-
`cation; matter printed in italics indicates the additions
`cation; matter printed in italics indicates the additions
`made by reissue.
`made by reissue.
`This application claims the benefit of U.S. Provisional
`This application claims the benefit of US. Provisional
`Application No. 60/335,897 filed on Nov. 21, 2001.
`Application No. 60/335,897 filed on Nov. 21, 2001.
`BACKGROUND OF THE INVENTION
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`1. Field of the Invention
`This invention relates to a method for reducing emissions
`This invention relates to a method for reducing emissions
`from evaporative control Systems including activated carbon
`from evaporative control systems including activated carbon
`particulate-filled canisters and adsorptive monolith
`particulate-filled canisters and adsorptive monolith-
`containing canisters, which monoliths include activated
`containing canisters, which monoliths include activated
`carbon, and to using Said adsorbing canisters to remove
`carbon, and to using said adsorbing canisters to remove
`Volatile organic compounds, and other chemical agents from
`volatile organic compounds, and other chemical agents from
`fluid Streams. More particularly, this invention relates to
`fluid streams. More particularly, this invention relates to
`using Said vapor-adsorbing materials in hydrocarbon fuel
`using said vapor-adsorbing materials in hydrocarbon fuel
`consuming engines.
`consuming engines.
`2. Description of Related Art (Including Information
`2. Description of Related Art (Including Information
`Disclosed Under 37 CFR 1.97 and 37 CFR 1.98)
`Disclosed Under 37 CFR 1.97 and 37 CFR 1.98)
`(a) Standard Working Capacity Adsorbents
`(a) Standard Working Capacity Adsorbents
`Evaporation of gasoline from motor vehicle fuel Systems
`Evaporation of gasoline from motor vehicle fuel systems
`is a major potential Source of hydrocarbon air pollution. The
`is a major potential source of hydrocarbon air pollution. The
`automotive industry is challenged to design engine compo
`automotive industry is challenged to design engine compo-
`nents and Systems to contain, as much as possible, the almost
`nents and systems to contain, as much as possible, the almost
`one billion gallons of gasoline evaporated from fuel Systems
`one billion gallons of gasoline evaporated from fuel systems
`each year in the United States alone. Such emissions can be
`each year in the United States alone. Such emissions can be
`controlled by canister Systems that employ activated carbon
`controlled by canister systems that employ activated carbon
`to adsorb and hold the vapor that evaporates. Under certain
`to adsorb and hold the vapor that evaporates. Under certain
`modes of engine operation, the adsorbed hydrocarbon vapor
`modes of engine operation, the adsorbed hydrocarbon vapor
`is periodically removed from the carbon by drawing air
`is periodically removed from the carbon by drawing air
`through the canister and burning the desorbed vapor in the
`through the canister and burning the desorbed vapor in the
`engine. The regenerated carbon is then ready to adsorb
`engine. The regenerated carbon is then ready to adsorb
`additional vapor. Under EPA mandate, Such control Systems
`additional vapor. Under EPA mandate, such control systems
`have been employed in the U.S. for about 30 years, and
`have been employed in the US. for about 30 years, and
`during that time government regulations have gradually
`during that
`time government regulations have gradually
`reduced the allowable emission levels for these systems. In
`reduced the allowable emission levels for these systems. In
`response, improvements in the control Systems have been
`response, improvements in the control systems have been
`largely focused on improving the capacity of the activated
`largely focused on improving the capacity of the activated
`carbon to hold hydrocarbon vapor. For example, current
`carbon to hold hydrocarbon vapor. For example, current
`canister Systems, containing activated carbon of uniform
`canister systems, containing activated carbon of uniform
`capacity, are readily capable of capturing and releasing 100
`capacity, are readily capable of capturing and releasing 100
`grams of vapor during adsorption and air purge regeneration
`grams of vapor during adsorption and air purge regeneration
`cycling. These canister Systems also must have low flow
`cycling. These canister systems also must have low flow
`restrictions in order to accommodate the bulk flow of
`restrictions in order to accommodate the bulk flow of
`displaced air and hydrocarbon vapor from the fuel tank
`displaced air and hydrocarbon vapor from the fuel tank
`during refueling. Improvements in activated carbons for
`during refueling. Improvements in activated carbons for
`automotive emission control systems are disclosed in US.
`automotive emission control Systems are disclosed in U.S.
`Pat. Nos.: 4,677,086; 5,204,310; 5,206,207; 5,250,491;
`Pat. Nos.: 4,677,086; 5,204,310; 5,206,207; 5,250,491;
`5,276,000; 5,304,527; 5,324,703; 5,416,056; 5,538,932;
`5,276,000; 5,304,527; 5,324,703; 5,416,056; 5,538,932;
`5,691,270; 5,736,481; 5,736,485; 5,863,858; 5,914,294;
`5,691,270; 5,736,481; 5,736,485; 5,863,858; 5,914,294;
`6,136,075; 6,171,373; 6,284,705.
`6,136,075; 6,171,373; 6,284,705.
`A typical canister employed in a State of the art auto
`A typical canister employed in a state of the art auto
`emission control system is shown in FIG. 1. Canister 1
`emission control system is shown in FIG. 1. Canister 1
`includes Support Screen 2, dividing wall 3, a vent port 4 to
`includes support screen 2, dividing wall 3, a vent port 4 to
`the atmosphere (for when the engine is oft), a vapor Source
`the atmosphere (for when the engine is oft), a vapor source
`connection 5 (from the fuel tank), a vacuum purge connec
`connection 5 (from the fuel tank), a vacuum purge connec-
`tion 6 (for when the engine is running), and adsorbent
`tion 6 (for when the engine is running), and adsorbent
`material fill 7.
`material fill 7.
`Other basic auto emission control system canisters are
`Other basic auto emission control System canisters are
`disclosed in US. Pat. Nos. 5,456,236; 5,456,237; 5,460,136;
`disclosed in U.S. Pat. Nos. 5,456,236; 5,456,237; 5,460,136;
`and 5,477,836.
`and 5,477,836.
`
`10
`
`15
`15
`
`20
`
`25
`25
`
`30
`
`35
`35
`
`40
`40
`
`45
`45
`
`50
`50
`
`55
`55
`
`60
`60
`
`65
`65
`
`US RE38,844 E
`US RE38,844 E
`
`2
`2
`Typical carbons for evaporative emission canisters are
`Typical carbons for evaporative emission canisters are
`characterized by Standard measurements of bed packing
`characterized by standard measurements of bed packing
`density (“apparent density,” g/mL), equilibrium Saturation
`density (“apparent density,” g/mL), equilibrium saturation
`capacity for 100% butane vapor (“butane activity,” g/100
`capacity for 100% butane vapor (“butane activity,” g/100
`g-carbon), and purgeability (“butane ratio’), specifically, the
`g-carbon), and purgeability (“butane ratio”), specifically, the
`proportion of adsorbed butane from the Saturation Step
`proportion of adsorbed butane from the saturation step
`which can be recovered from the carbon by an air purge Step.
`which can be recovered from the carbon by an air purge step.
`The multiplicative product of these three properties yields a
`The multiplicative product of these three properties yields a
`measure of the carbon's effective butane “working capacity'
`measure of the carbon’s effective butane “working capacity”
`(“BWC", g/dL), measured by ASTM D5228-92, which has
`(“BWC”, g/dL), measured by ASTM D5228-92, which has
`been established in the art as a good predictor of the canister
`been established in the art as a good predictor of the canister
`working capacity for gasoline vapors. Carbons that eXcel for
`working capacity for gasoline vapors. Carbons that excel for
`this application have high BWC, typically 9 to 15+g/dL
`this application have high BWC, typically 9 to 15+g/dL
`BWC, as a result of high Saturation capacities on a
`BWC, as a result of high saturation capacities on a
`volumetric-basis for butane (the product of density and
`volumetric-basis for butane (the product of density and
`butane activity), and high butane ratios (>0.85). In terms of
`butane activity), and high butane ratios (>0.85). In terms of
`isothermal equilibrium adsorption capacities acroSS all
`isothermal equilibrium adsorption capacities across all
`Vapor concentrations, these carbons characteristically have
`vapor concentrations, these carbons characteristically have
`high incremental capacity as a function of increased vapor
`high incremental capacity as a function of increased vapor
`concentration (i.e., isotherm curved upward on a semi-log
`concentration (i.e., isotherm curved upward on a semi-log
`graph). This isotherm upward curve reflects the high work
`graph). This isotherm upward curve reflects the high work-
`ing capacity performance feature of these carbons, in that
`ing capacity performance feature of these carbons, in that
`gasoline vapors are adsorbed in high quantity at high con
`gasoline vapors are adsorbed in high quantity at high con-
`centrations but readily released in high concentration to an
`centrations but readily released in high concentration to an
`air purge Stream. In addition, these carbons tend to be
`air purge stream. In addition,
`these carbons tend to be
`granular (Somewhat irregularly shaped) or cylindrical pellet,
`granular (somewhat irregularly shaped) or cylindrical pellet,
`typically of a size just about 1-3 mm in diameter. It has been
`typically of a size just about 1—3 mm in diameter. It has been
`found that Somewhat larger sizes hinder diffusional transport
`found that somewhat larger sizes hinder diffusional transport
`of vapors into and out of the carbon particle during dynamic
`of vapors into and out of the carbon particle during dynamic
`adsorb and purge cycles. On the other hand, Somewhat
`adsorb and purge cycles. On the other hand, somewhat
`Smaller size particles have unacceptably high flow restric
`smaller size particles have unacceptably high flow restric-
`tion for displaced air and hydrocarbon vapors during refu
`tion for displaced air and hydrocarbon vapors during refu-
`eling.
`eling.
`(b) Diurnal Breathing Loss (DBL) Requirements
`(b) Diurnal Breathing Loss (DBL) Requirements
`Recently, regulations have been promulgated that require
`Recently, regulations have been promulgated that require
`a change in the approach with respect to the way in which
`a change in the approach with respect to the way in which
`vapors must be controlled. Allowable emission levels from
`vapors must be controlled. Allowable emission levels from
`canisters would be reduced to such low levels that
`the
`canisters would be reduced to Such low levels that the
`primary Source of emitted vapor, the fuel tank, is no longer
`primary source of emitted vapor, the fuel tank, is no longer
`the primary concern, as current conventional evaporative
`the primary concern, as current conventional evaporative
`emission control appears to have achieved a high efficiency
`emission control appears to have achieved a high efficiency
`of removal. Rather, the concern now is actually the hydro
`of removal. Rather, the concern now is actually the hydro-
`carbon left on the carbon adsorbent itself as a residual “heel”
`carbon left on the carbon adsorbent itself as a residual "heel'
`after the regeneration (purge) Step. Such emissions typically
`after the regeneration (purge) step. Such emissions typically
`occur when a vehicle has been parked and Subjected to
`occur when a vehicle has been parked and subjected to
`diurnal temperature changes over a period of Several days,
`diurnal temperature changes over a period of several days,
`commonly called “diurnal breathing losses.” Now, the Cali
`commonly called “diurnal breathing losses.” Now, the Cali-
`fornia Low Emission Vehicle Regulation makes it desirable
`fornia Low Emission Vehicle Regulation makes it desirable
`for these diurnal breathing loss (DBL) emissions from the
`for these diurnal breathing loss (DBL) emissions from the
`canister system to be below 10 mg (“PZEV) for a number
`canister system to be below 10 mg (“PZEV”) for a number
`of vehicles beginning with the 2003 model year and below
`of vehicles beginning with the 2003 model year and below
`50 mg, typically below 20 mg, (“LEV-II”) for a larger
`50 mg,
`typically below 20 mg, (“LEV-II”) for a larger
`number of vehicles beginning with the 2004 model year.
`number of vehicles beginning with the 2004 model year.
`(“PZEV" and “LEV-II" are criteria of the California Low
`(“PZEV” and “LEV-II” are criteria of the California Low
`Emission Vehicle Regulation.)
`Emission Vehicle Regulation.)
`While standard carbons used in the commercial canisters
`While Standard carbons used in the commercial canisters
`eXcel in terms of working capacity, these carbons are unable
`excel in terms of working capacity, these carbons are unable
`to meet DBL emission targets under normal canister opera-
`to meet DBL emission targets under normal canister opera
`tion. Furthermore, none of the standard measures of working
`tion. Furthermore, none of the Standard measures of working
`capacity properties correlate with DBL emission perfor
`capacity properties correlate with DBL emission perfor-
`mance. Nonetheless, one option for meeting emission targets
`mance. Nonetheless, one option for meeting emission targets
`is to Significantly increase the Volume of purge gas during
`is to significantly increase the volume of purge gas during
`regeneration in order to reduce the amount of residual
`regeneration in order to reduce the amount of residual
`hydrocarbon heel in the carbon bed and thereby reduce
`hydrocarbon heel in the carbon bed and thereby reduce
`Subsequent emissions. This Strategy, however, has the draw
`subsequent emissions. This strategy, however, has the draw-
`back of complicating management of the fuel/air mixture to
`back of complicating management of the fuel/air mixture to
`the engine during purge regeneration and tends to adversely
`the engine during purge regeneration and tends to adversely
`
`

`

`3
`3
`affect tailpipe emissions, i.e., moving or redefining the
`i.e., moving or redefining the
`affect
`tailpipe emissions,
`problem rather than solving it. (See U.S. Pat. No. 4,894,
`problem rather than solving it. (See US. Pat. No. 4,894,
`072.)
`072.)
`Another option is to design the carbon bed So that there is
`Another option is to design the carbon bed so that there is
`a relatively low cross-sectional area on the Vent-side of the
`a relatively low cross-sectional area on the vent-side of the
`canister System (the first portion of the bed to encounter
`canister system (the first portion of the bed to encounter
`purge air), either by redesign of the existing canister dimen
`purge air), either by redesign of the existing canister dimen-
`Sions or by the installation of a Supplemental, auxiliary
`sions or by the installation of a supplemental, auxiliary
`Vent-side canister of appropriate dimensions. This alterna
`vent-side canister of appropriate dimensions. This alterna-
`tive has the effect of locally reducing residual hydrocarbon
`tive has the effect of locally reducing residual hydrocarbon
`heel by increasing the intensity of purge for that vent-side
`heel by increasing the intensity of purge for that vent-side
`portion of the bed, thereby improving its ability to retain
`portion of the bed, thereby improving its ability to retain
`vapors that would otherwise be emitted from the canister
`vapors that would otherwise be emitted from the canister
`System under diurnal breathing conditions. The drawback is
`system under diurnal breathing conditions. The drawback is
`that there is a useful limit to which a portion of the bed can
`that there is a useful limit to which a portion of the bed can
`be elongated at reduced croSS-Sectional area without other
`be elongated at reduced cross-sectional area without other-
`wise incurring excessive flow restriction by the canister
`wise incurring excessive flow restriction by the canister
`System. In practice, this limit does not allow employing a
`system. In practice, this limit does not allow employing a
`Sufficiently narrowed and elongated geometry to meet emis
`sufficiently narrowed and elongated geometry to meet emis-
`sion targets. (See U.S. Pat. No. 5,957,114.)
`sion targets. (See US. Pat. No. 5,957,114.)
`Another option for increasing the purge efficiency of a
`Another option for increasing the purge efficiency of a
`fuel vapor/air mixture fraction adsorbed in the pores of the
`fuel vapor/air mixture fraction adsorbed in the pores of the
`adsorbent material is Suggested by the teachings of U.S. Pat.
`adsorbent material is suggested by the teachings of US. Pat.
`Nos. 6,098,601 and 6,279.548 by providing a heating capa
`Nos. 6,098,601 and 6,279,548 by providing a heating capa-
`bility internal of the canister, or a section thereof, either to
`bility internal of the canister, or a Section thereof, either to
`increase pressure in the vapor Storage canister to expel hot
`increase pressure in the vapor storage canister to expel hot
`Vapor through the vapor/purge conduit back into the fuel
`vapor through the vapor/purge conduit back into the fuel
`tank where it condenses at the lower ambient temperature
`tank where it condenses at the lower ambient temperature
`therein (601) or to increase the purging efficiency of hydro
`therein (’601) or to increase the purging efficiency of hydro-
`carbons from the heated adsorbent material and carry the
`carbons from the heated adsorbent material and carry the
`purged fuel vapor to the induction System of an associated
`purged fuel vapor to the induction system of an associated
`engine (548). However, this increases the complexity of
`engine (’548). However, this increases the complexity of
`control System management, and there appears Some inher
`control system management, and there appears some inher-
`ent Safety concerns in providing heating internal of a can
`ent safety concerns in providing heating internal of a can-
`ister for trapping fuel vapors.
`ister for trapping fuel vapors.
`Thus, an acceptable remedy, which does not have draw
`Thus, an acceptable remedy, which does not have draw-
`backs as the cited alternative approaches, is greatly desired.
`backs as the cited alternative approaches, is greatly desired.
`It is submitted that the invention disclosed and claimed
`It is Submitted that the invention disclosed and claimed
`herein provides the desired Solution.
`herein provides the desired solution.
`SUMMARY OF THE INVENTION
`SUMMARY OF THE INVENTION
`An invention is disclosed for Sharply reducing diurnal
`An invention is disclosed for sharply reducing diurnal
`breathing loSS emissions from evaporative emissions canis
`breathing loss emissions from evaporative emissions canis-
`ters by the use of multiple layers, or Stages, of adsorbents.
`ters by the use of multiple layers, or stages, of adsorbents.
`On the fuel source-side of the canister, standard high work-
`On the fuel Source-Side of the canister, Standard high work
`ing capacity carbons are preferred. On the vent-side, the
`ing capacity carbons are preferred. On the vent-side, the
`preferred adsorbent volume exhibits a flat or flattened adsor-
`preferred adsorbent volume exhibits a flat or flattened adsor
`bent isotherm on a volumetric basis in addition to certain
`bent isotherm on a Volumetric basis in addition to certain
`characteristically desirable adsorptive properties acroSS
`characteristically desirable adsorptive properties across
`broad vapor concentrations, Specifically relatively low incre
`broad vapor concentrations, specifically relatively low incre-
`mental capacity at high concentration vapors compared with
`mental capacity at high concentration vapors compared with
`the fuel source-side adsorbent volume. Two approaches are
`the fuel Source-Side adsorbent volume. Two approaches are
`described for attaining the preferred properties for the Vent
`described for attaining the preferred properties for the vent-
`side adsorbent volume. One approach is to use a filler and/or
`Side adsorbent Volume. One approach is to use a filler and/or
`bed Voidages as a volumetric diluent for flattening an
`bed voidages as a volumetric diluent
`for flattening an
`isotherm. A Second approach is to employ an adsorbent with
`isotherm. Asecond approach is to employ an adsorbent with
`the desired isotherm properties and to process it into an
`the desired isotherm properties and to process it into an
`appropriate shape or form without necessarily requiring any
`appropriate shape or form without necessarily requiring any
`Special provision for dilution. Both Such approaches provide
`special provision for dilution. Both such approaches provide
`a Substantially lower emissions canister System without a
`a substantially lower emissions canister system without a
`Significant loSS in working capacity or an increase in flow
`significant loss in working capacity or an increase in flow
`restriction compared with prior art adsorbents used for
`restriction compared with prior art adsorbents used for
`automotive emissions control.
`automotive emissions control.
`BRIEF DESCRIPTION OF THE DRAWINGS
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 shows, in cross-section, a prior art canister system.
`FIG. 1 shows, in croSS-Section, a prior art canister System.
`
`10
`
`15
`15
`
`20
`
`25
`25
`
`30
`
`35
`35
`
`40
`40
`
`45
`45
`
`50
`50
`
`55
`55
`
`60
`60
`
`65
`65
`
`US RE38,844 E
`US RE38,844 E
`
`4
`4
`FIG. 2 shows, in cross-section, one embodiment-of the
`FIG. 2 shows, in cross-section, one embodiment-of the
`invention canister comprising multiple adsorbents.
`invention canister comprising multiple adsorbents.
`FIG. 3 shows butane isotherm properties for different
`FIG. 3 shows butane isotherm properties for different
`activated carbon adsorbents.
`activated carbon adsorbents.
`DESCRIPTION OF THE PREFERRED
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT(S)
`EMBODIMENT(S)
`The disclosed invention relates to the use of multiple beds
`The disclosed invention relates to the use of multiple beds
`(or layers, stages, or chambers) of adsorbent materials,
`(or layers, stages, or chambers) of adsorbent materials,
`which, in combination, Significantly reduce DBL emissions
`which, in combination, significantly reduce DBL emissions
`while maintaining the high working capacity and low flow
`while maintaining the high working capacity and low flow
`restriction properties of the canister System. (See FIG. 2.)
`restriction properties of the canister system. (See FIG. 2.)
`These adsorbents include activated carbon from a variety of
`These adsorbents include activated carbon from a variety of
`raw materials, including wood, peat, coal, coconut, Synthetic
`raw materials, including wood, peat, coal, coconut, synthetic
`or natural polymer, and a variety of processes, including
`or natural polymer, and a variety of processes, including
`chemical and/or thermal activation, as well as inorganic
`chemical and/or thermal activation, as well as inorganic
`adsorbents, including molecular Sieves, porous alumina,
`adsorbents,
`including molecular sieves, porous alumina,
`pillared clays, Zeolites, and porous Silica, and organic
`pillared clays, zeolites, and porous silica, and organic
`adsorbents, including porous polymers. The adsorbents may
`adsorbents, including porous polymers. The adsorbents may
`be in granular, Spherical, or pelletized cylindrical shapes, or
`be in granular, spherical, or pelletized cylindrical shapes, or
`may be extruded into special thin-walled cross-sectional
`may be extruded into special
`thin-walled cross-sectional
`shapes, Such as hollow-cylinder, Star, twisted Spiral, asterisk,
`shapes, such as hollow-cylinder, star, twisted spiral, asterisk,
`configured ribbons, or other shapes within the technical
`configured ribbons, or other shapes within the technical
`capabilities of the art. In Shaping, inorganic and/or organic
`capabilities of the art. In shaping, inorganic and/or organic
`binders may be used. The adsorbents may be formed into a
`binders may be used. The adsorbents may be formed into a
`monolith or honeycomb part. The adsorbents may be incor
`monolith or honeycomb part. The adsorbents may be incor-
`porated into a canister as one or more layers, or Separate
`porated into a canister as one or more layers, or separate
`chambers, or they may be inserted in the fluid stream flow
`chambers, or they may be inserted in the fluid stream flow
`as auxiliary canister beds.
`as auxiliary canister beds.
`One common feature for all of these approaches is to have
`One common feature for all of these approaches is to have
`a vent-side adsorbent with a relatively flat-shaped isotherm.
`a vent-side adsorbent with a relatively flat-shaped isotherm.
`This isotherm shape is important for reasons related to purge
`This isotherm shape is important for reasons related to purge
`efficiency across the adsorbent bed depth. For an adsorbent
`efficiency across the adsorbent bed depth. For an adsorbent
`with a flat adsorption isotherm, the concentration of hydro
`with a flat adsorption isotherm, the concentration of hydro-
`carbon vapor in equilibrium with adsorbed hydrocarbon, by
`carbon vapor in equilibrium with adsorbed hydrocarbon, by
`definition, decreases further as the adsorbed hydrocarbon is
`definition, decreases further as the adsorbed hydrocarbon is
`removed compared with an adsorbent with a more Steeply
`removed compared with an adsorbent with a more steeply
`Sloped isotherm. Thus, when Such a material is employed as
`sloped isotherm. Thus, when such a material is employed as
`an adsorbent volume on the vent-side region of a canister,
`an adsorbent volume on the vent-side region of a canister,
`purge is able to reduce the vapor concentration in the area of
`purge is able to reduce the vapor concentration in the area of
`the purge inlet to a very low level. Since it is the vapor near
`the purge inlet to a very low level. Since it is the vapor near
`the