(12) United States Patent
`Hiltzik et al.
`
`USOO6540815B1
`US 6,540,815 B1
`Apr. 1, 2003
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54)
`
`(75)
`
`(73)
`
`(21)
`(22)
`
`(60)
`
`(51)
`(52)
`(58)
`
`(56)
`
`METHOD FOR REDUCING EMISSIONS
`FROM EVAPORATIVE EMISSIONS
`CONTROL SYSTEMS
`
`Inventors: Laurence H. Hiltzik, Charleston, SC
`(US); Jacek Z. Jagiello, Charleston, SC
`(US); Edward D. Tolles, Charleston,
`SC (US); Roger S. Williams,
`Lexington, VA (US)
`Assignee: MeadWestvaco Corporation,
`Stamford, CT (US)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`Notice:
`
`Appl. No.: 10/100,362
`Filed:
`Mar 18, 2002
`Related U.S. Application Data
`Provisional application No. 60/335,897, filed on Nov. 21,
`2001.
`Int. Cl.......................... F02M 33/02; B01D 53/04
`U.S. Cl. ............................ 95/146; 95/900; 123/519
`Field of Search ............................ 95/90, 146, 148,
`95/900–903; 96/132, 133, 147; 123/518,
`519; 502/416
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,677,086 A * 6/1987 McCue et al. .............. 123/519
`4,894,072 A * 1/1990 Turner et al. ..
`... 123/519
`5,204,310 A * 4/1993 Tolles et al. ...
`... 123/519
`5,206.207 A * 4/1993 Tolles ...........
`... 5O2/423
`5,207,808 A * 5/1993 Haruta et al. ..
`... 123/519
`5,238,470 A * 8/1993 Tolles et al. .................. 95/143
`5,250,491. A * 10/1993 Yan ..................
`... 264/117
`5,276,000 A * 1/1994 Matthews et al.
`... 502/.424
`5,304,527 A * 4/1994 Dimitri .............
`... 5O2/416
`5,324.703 A * 6/1994 McCue et al. ....
`... 502/.424
`5,337,721 A * 8/1994 Kasuya et al. .............. 123/519
`
`
`
`5,408,976 A * 4/1995 Reddy .................... 123/198 D
`5,416,056. A
`5/1995 Baker ......................... 502/425
`5,456,236 A * 10/1995 Wakashiro et al. ......... 123/519
`(List continued on next page.)
`FOREIGN PATENT DOCUMENTS
`
`7/2001
`11 1316.3
`EP
`2002012826 A * 2/2002
`KR
`WO 92/O1585
`9/1992
`WO
`WO 01/62367
`8/2001
`WO
`Primary Examiner David A. Simmons
`ASSistant Examiner-Frank M. Lawrence
`(74) Attorney, Agent, or Firm Terry B. McDaniel; Daniel
`B. Reece, IV; Thomas A. Boshinski
`(57)
`ABSTRACT
`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.
`
`30 Claims, 3 Drawing Sheets
`
` MAHLE-1005
`U.S. Patent No. RE38,844
`
`

`

`US 6,540,815 B1
`US 6,540,815 B1
`
`Page 2
`Page 2
`
`U.S. PATENT DOCUMENTS
`U.S. PATENT DOCUMENTS
`
`5,456,237 A * 10/1995 Yamazaki et al.
`.......... 123/519
`5,456.237 A * 10/1995 Yamazaki et al. .......... 123/519
`5,460,136 A * 10/1995 Yamazaki et al.
`... 123/519
`5,460,136 A * 10/1995 Yamazaki etal.
`123/519
`
`
`5,477,836 A * 12/1995 Hyodoetal. .
`123/519
`5,477,836 A * 12/1995 Hyodo et al. .
`... 123/519
`5,538,932 A * 7/1996 Yan et al. ..
`... 502/.424
`5,538,932 A *
`7/1996 Yan etal. ..
`502/424
`
`5,564,398 A * 10/1996 Maedaetal.
`123/519
`5,564,398 A * 10/1996 Maeda et al.
`... 123/519
`
`5,691,270 A * 11/1997 Miller .......
`... 502/174
`5,691,270 A * 11/1997 Miller
`.......
`502/174
`5,736,481 A *
`4/1998 Miller occ 502/174
`5,736,481. A
`4/1998 Miller ........................ 502/174
`5,736,485 A * 4/1998 Miller ........................ 502/174
`5,736,485 A *
`4/1998 Miller oo. 502/174
`
`5,863,858 A *
`1/1999 Miller et al... 502/180
`5,863.858 A * 1/1999 Miller et al................. 502/18O
`5,914,294 A *
`6/1999 Park et al. voces 501/100
`5,914.294. A * 6/1999 Park et al. .................. 501/100
`5,914,457 A *
`6/1999 Itakura et al. oe 123/519
`5,914,457 A
`6/1999 Itakura et al. .............. 123/519
`6,136,075 A * 10/2000 Bragget al. ...
`... 55/519
`6,136,075 A * 10/2000 Bragg etal. ...
`.. 55/519
`
`6,171,373 Bi *
`1/2001 Park etal.
`.....
`.. 95/138
`6,171,373 B1 * 1/2001 Park et al. .....
`... 95/138
`
`6.279,548 B1 * 8/2001 Reddy ........
`123/519
`6,279,548 Bl *
`8/2001 Reddy........
`vee 123/519
`6,284,705 Bl *
`9/2001 Park et al. cece 502/180
`6.284,705 B1 * 9/2001 Park et al. .................. 502/18O
`6,488,748 B2 12/2002 Yamafuji et al.
`6,488,748 B2
`12/2002 Yamatfujietal.
`* cited by examiner
`* cited by examiner
`
`
`
`

`

`ZAN
`
`

`

`U.S. Patent
`
`Apr. 1, 2003
`
`Sheet 2 of 3
`
`US 6,540,815 B1
`
`FIGURE 2
`
`Pea id inaeidiei aie
`eeRe aa a8
`A en aao
`eeeegh tg Hat alah
`eegeee ae gS,
`PP ar aer 8,
`ee ee a ate SeAOLI 5
`aOe ee LP rs et
`eea ne ENS nt
`
`
`
`69496OF6966644444
`
`$O6600664
` bbbobboed
`hhhhhhhhh
`
`
`

`

`U.S. Patent
`U.S. Patent
`
`Apr.1, 2003
`Apr. 1, 2003
`
`Sheet 3 of 3
`Sheet 3 of 3
`
`US 6,540,815 B1
`US 6,540,815 B1
`
`FIGURE 3
`FIGURE 3
`
`n-Butane Adsorption isotherm at 25°C
`n-Butane Adsorption Isotherm at 25°C
`
`
`|
`
`
`
`!
`
`: BAX 1500
`| BAX 1500
`
`|
`
`
`
`
`
`a
`
`|
`
`
`
`
`Example 3
`Example 1
`at
`Example 3
`Example
`
`
`™ Example 2
`N Example 2
`
`
`
`|
`
`
`
` {{|
`
`,
`
`||
`
`--
`
`—
`
`-
`
`-
`
`18O
`180
`
`160
`160
`
`140
`140
`
`8 O
`80
`
`6 O
`60
`
`4 O
`40
`
`2 O
`20
`
`
`
`Massadsorbed,g/L
`
`O.1
`0.1
`
`1
`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
`
`This application claims the benefit of U.S. Provisional
`This application claims the benefit of U.S. 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 motorvehicle fuel systems
`is a major potential Source of hydrocarbon air pollution. The
`is a major potential source of hydrocarbonair 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 systemsto contain, as muchas possible, the almost
`one billion gallons of gasoline evaporated from fuel Systems
`onebillion 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 vaporin 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 U.S. 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
`gramsof 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 U.S.
`automotive emission control systems are disclosed in US.
`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 off), a vapor Source
`the atmosphere (for when the engine is off), 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 U.S. Pat. Nos. 5,456,236; 5,456,237; 5,460,136;
`disclosed in US. Pat. Nos. 5,456,236; 5,456,237; 5,460,136;
`and 5,477,836.
`and 5,477,836.
`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
`
`10
`
`15
`15
`
`20
`
`25
`25
`
`30
`
`35
`35
`
`40
`40
`
`45
`45
`
`50
`50
`
`55
`55
`
`60
`60
`
`65
`65
`
`US 6,540,815 B1
`US 6,540,815 B1
`
`2
`2
`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 anair purgestep.
`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. Carbonsthat 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 (somewhatirregularly shaped) or cylindricalpellet,
`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 somewhatlarger 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-
`carbonleft on the carbon adsorbentitself 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 emissionstypically
`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 makesit 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 managementofthe fuel/air mixture to
`the engine during purge regeneration and tends to adversely
`the engine during purge regeneration and tends to adversely
`affect tailpipe emissions, i.e., moving or redefining the
`affect
`tailpipe emissions,
`i.e., moving or redefining the
`problem rather than solving it. (See U.S. Pat. No. 4,894,
`problem rather than solving it. (See U.S. Pat. No. 4,894,
`072.)
`072.)
`
`

`

`US 6,540,815 B1
`US 6,540,815 B1
`
`5
`
`10
`
`15
`15
`
`20
`
`25
`25
`
`30
`
`35
`35
`
`3
`4
`3
`4
`DESCRIPTION OF THE PREFERRED
`Another option is to design the carbon bed So that there is
`DESCRIPTION OF THE PREFERRED
`Anotheroption is to design the carbon bed so that there is
`EMBODIMENT(S)
`a relatively low cross-sectional area on the Vent-side of the
`EMBODIMENT(S)
`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
`The disclosed invention relates to the use of multiple beds
`The disclosed invention relates to the use of multiple beds
`purge air), either by redesign of the existing canister dimen
`purge air), either by redesign of the existing canister dimen-
`(or layers, stages, or chambers) of adsorbent materials,
`(or layers, stages, or chambers) of adsorbent materials,
`Sions or by the installation of a Supplemental, auxiliary
`sions or by the installation of a supplemental, auxiliary
`which, in combination, Significantly reduce DBL emissions
`which, in combination, significantly reduce DBL emissions
`Vent-side canister of appropriate dimensions. This alterna
`vent-side canister of appropriate dimensions. This alterna-
`while maintaining the high working capacity and low flow
`while maintaining the high working capacity and low flow
`tive has the effect of locally reducing residual hydrocarbon
`tive has the effect of locally reducing residual hydrocarbon
`restriction properties of the canister System. (See FIG. 2.)
`restriction properties of the canister system. (See FIG. 2.)
`heel by increasing the intensity of purge for that vent-side
`heel by increasing the intensity of purge for that vent-side
`These adsorbents include activated carbon from a variety of
`These adsorbents include activated carbon from a variety of
`portion of the bed, thereby improving its ability to retain
`portion of the bed, thereby improving its ability to retain
`raw materials, including wood, peat, coal, coconut, Synthetic
`raw materials, including wood,peat, coal, coconut, synthetic
`vapors that would otherwise be emitted from the canister
`vapors that would otherwise be emitted from the canister
`or natural polymer, and a variety of processes, including
`or natural polymer, and a variety of processes, including
`System under diurnal breathing conditions. The drawback is
`system under diurnal breathing conditions. The drawbackis
`chemical and/or thermal activation, as well as inorganic
`chemical and/or thermal activation, as well as inorganic
`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
`adsorbents, including molecular Sieves, porous alumina,
`adsorbents,
`including molecular sieves, porous alumina,
`be elongated at reduced croSS-Sectional area without other
`be elongated at reduced cross-sectional area without other-
`pillared clays, Zeolites, and porous Silica, and organic
`pillared clays, zeolites, and porous silica, and organic
`wise incurring excessive flow restriction by the canister
`wise incurring excessive flow restriction by the canister
`adsorbents, including porous polymers. The adsorbents may
`adsorbents, including porous polymers. The adsorbents may
`System. In practice, this limit does not allow employing a
`system. In practice, this limit does not allow employing a
`be in granular, Spherical, or pelletized cylindrical shapes, or
`be in granular, spherical, or pelletized cylindrical shapes, or
`Sufficiently narrowed and elongated geometry to meet emis
`sufficiently narrowed and elongated geometry to meet emis-
`may be extruded into special thin-walled cross-sectional
`may be extruded into special
`thin-walled cross-sectional
`sion targets. (See U.S. Pat. No. 5,957,114.)
`sion targets. (See U.S. Pat. No. 5,957,114.)
`shapes, Such as hollow-cylinder, Star, twisted Spiral, asterisk,
`shapes, such as hollow-cylinder, star, twisted spiral, asterisk,
`Another option for increasing the purge efficiency of a
`Another option for increasing the purge efficiency of a
`configured ribbons, or other shapes within the technical
`configured ribbons, or other shapes within the technical
`fuel vapor/air mixture fraction adsorbed in the pores of the
`fuel vapor/air mixture fraction adsorbed in the pores of the
`capabilities of the art. In Shaping, inorganic and/or organic
`capabilities of the art. In shaping, inorganic and/or organic
`adsorbent material is Suggested by the teachings of U.S. Pat.
`adsorbent material is suggested by the teachings of U.S. Pat.
`binders may be used. The adsorbents may be formed into a
`binders may be used. The adsorbents may be formedinto a
`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-
`monolith or honeycomb part. The adsorbents may be incor
`monolith or honeycombpart. The adsorbents maybe incor-
`bility internal of the canister, or a Section thereof, either to
`bility internal of the canister, or a section thereof, either to
`porated into a canister as one or more layers, or Separate
`porated into a canister as one or more layers, or separate
`increase pressure in the vapor Storage canister to expel hot
`increase pressure in the vapor storage canister to expel hot
`chambers, or they may be inserted in the fluid stream flow
`chambers, or they may be inserted in the fluid stream flow
`Vapor through the vapor/purge conduit back into the fuel
`vapor through the vapor/purge conduit back into the fuel
`as auxiliary canister beds.
`as auxiliary canister beds.
`tank where it condenses at the lower ambient temperature
`tank where it condenses at the lower ambient temperature
`One common feature for all of these approaches is to have
`One commonfeature for all of these approachesis to have
`therein (601) or to increase the purging efficiency of hydro
`therein (’601) or to increase the purging efficiency of hydro-
`a Vent-Side adsorbent with a relatively flat-shaped isotherm.
`a vent-side adsorbent with a relatively flat-shaped isotherm.
`carbons from the heated adsorbent material and carry the
`carbons from the heated adsorbent material and carry the
`This isotherm shape is important for reasons related to purge
`This isotherm shape is important for reasonsrelated to purge
`purged fuel vapor to the induction System of an associated
`purged fuel vapor to the induction system of an associated
`efficiency across the adsorbent bed depth. For an adsorbent
`efficiency across the adsorbent bed depth. For an adsorbent
`engine (548). However, this increases the complexity of
`engine (7548). However, this increases the complexity of
`with a flat adsorption isotherm, the concentration of hydro
`with a flat adsorption isotherm, the concentration of hydro-
`control System management, and there appears Some inher
`control system management, and there appears some inher-
`carbon vapor in equilibrium with adsorbed hydrocarbon, by
`carbon vapor in equilibrium with adsorbed hydrocarbon, by
`ent Safety concerns in providing heating internal of a can
`ent safety concerns in providing heating internal of a can-
`definition, decreases further as the adsorbed hydrocarbon is
`definition, decreases further as the adsorbed hydrocarbonis
`ister for trapping fuel vapors.
`ister for trapping fuel vapors.
`removed compared with an adsorbent with a more steeply
`removed compared with an adsorbent with a more steeply
`Thus, an acceptable remedy, which does not have draw
`Thus, an acceptable remedy, which does not have draw-
`Sloped isotherm. Thus, when Such a material is employed as
`sloped isotherm. Thus, when such a material is employed as
`backs as the cited alternative approaches, is greatly desired.
`backsas the cited alternative approaches, is greatly desired.
`an adsorbent volume on the vent-side region of a canister,
`an adsorbent volume on the vent-side region of a canister,
`It is submitted that the invention disclosed and claimed
`It is Submitted that the invention disclosed and claimed
`purge is able to reduce the vapor concentration in the area of
`purgeis able to reduce the vapor concentration in the area of
`herein provides the desired Solution.
`herein provides the desired solution.
`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
`SUMMARYOF THE INVENTION
`the purge inlet that eventually emerges as bleed, decreasing
`SUMMARY OF THE INVENTION
`the purge inlet that eventually emerges as bleed, decreasing
`this concentration reduces the bleed emission level. The
`this concentration reduces the bleed emission level. The
`An invention is disclosed for Sharply reducing diurnal
`An invention is disclosed for sharply reducing diurnal
`degree of removal of adsorbed hydrocarbon during purge is
`degree of removal of adsorbed hydrocarbon during purge is
`breathing loSS emissions from evaporative emissions canis
`breathing loss emissions from evaporative emissions canis-
`determined by the difference between the concentration of
`determined by the difference between the concentration of
`ters by the use of multiple layers, or Stages, of adsorbents.
`ters by the use of multiple layers, or stages, of adsorbents.
`hydrocarbon picked up in the purge gas and the concentra
`hydrocarbon picked up in the purge gas and the concentra-
`On the fuel Source-Side of the canister, Standard high work
`On the fuel source-side of the canister, standard high work-
`tion in equilibrium with the adsorbent at any point in the bed.
`tion in equilibrium with the adsorbentat any pointin the bed.
`ing capacity carbons are preferred. On the vent-side, the
`ing capacity carbons are preferred. On the vent-side, the
`Thus, adsorbent in the immediate vicinity of the purge inlet
`Thus, adsorbent in the immediate vicinity of the purge inlet
`preferred adsorbent volume exhibits a flat or flattened adsor
`preferred adsorbent volumeexhibits a flat or flattened adsor-
`will be most thoroughly regenerated. At points deeper in the
`bent isotherm on a volumetric basis in addition to certain
`will be most thoroughly regenerated. At points deeper in the
`bent isotherm on a Volumetric basis in addition to certain
`adsorbent bed, less hydrocarbon will be removed because
`adsorbent bed, less hydrocarbon will be removed because
`characteristically desirable adsorptive properties acroSS
`characteristically desirable adsorptive properties across
`the purge gas will already contain hydrocarbon removed
`the purge gas will already contain hydrocarbon removed
`broad vapor concentrations, Specifically relatively low incre
`broad vapor concentrations,specifically relatively low incre-
`from previous points in the bed. An adsorbent with a flatter
`from previous points in the bed. An adsorbent with a flatter
`mental capacity at high concentration vapors compared with
`mental capacity at high concentration vapors compared with
`adsorption isotherm will give up leSS Vapor into the purge
`adsorption isotherm will give up less vapor into the purge
`the fuel Source-Side adsorbent volume. Two approaches are
`the fuel source-side adsorbent volume. Two approaches are
`50
`Stream and this purge will then be more efficient in reducing
`stream and this purge will then be moreefficient in reducing
`described for attaining the preferred properties for the Vent
`described for attaining the preferred properties for the vent-
`50
`Vapor concentrations deeper into the bed. Therefore, for a
`vapor concentrations deeper into the bed. Therefore, for a
`Side adsorbent Volume. One approach is to use a filler and/or
`side adsorbent volume. One approachis to useafiller and/or
`given quantity of purge gas, it will be possible to reduce the
`given quantity of purge gas, it will be possible to reduce the
`bed Voidages as a volumetric diluent for flattening an
`bed voidages as a volumetric diluent
`for flattening an
`Vapor concentration in a Volume of adsorbent with a flat
`vapor concentration in a volume of adsorbent with a flat
`isotherm. A Second approach is to employ an adsorbent with
`isotherm. A second approach is to employ an adsorbent with
`adsorption is