(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2002/0073847 A1
`Sheline et al.
`(43) Pub. Date:
`Jun. 20, 2002
`
`US 20020073847A1
`
`(54) CELL WITHINA CELL MONOLITH
`STRUCTURE FOR AN EVAPORATIVE
`EMISSIONS HYDROCARBON SCRUBBER
`
`(21) Appl. No.:
`
`09/738,558
`
`(22) Filed:
`
`Dec. 15, 2000
`
`(76) Inventors: Matthew R. Sheline, Grand Blanc, MI
`(US); Charles H. Covert, Manchester,
`NY (US); Susan LaBine, Avon, NY
`(US); Jonathan M. Oemoke,
`Rochester, NY (US); Eileen A.
`Scardino, Rochester, NY (US)
`
`Correspondence Address:
`Vincent A. CichoSZ
`DELPHITECHNOLOGIES, INC.
`1450 West Long Lake
`Troy, MI 48007 (US)
`
`
`
`Publication Classification
`
`(51) Int. Cl." ..................................................... B01D 53/02
`(52) U.S. Cl. ................................................. 95/143; 96/108
`(57)
`ABSTRACT
`A monolith for use in an evaporative emissions hydrocarbon
`scrubber is disclosed. The monolith, which is concentrically
`disposed with a shell, has at least one cell group disposed
`around at least two individual cells, Such that the cell group
`comprises at least three thick walls. The individual cells
`comprise at least on thin wall, with the thick walls being
`thicker than the thin wall. A method for using the evapora
`tive emissions hydrocarbon Scrubber is also disclosed.
`
`26
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`22
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`24
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`BASF-1022
`U.S. Patent No. RE38,844
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`

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`Patent Application Publication Jun. 20, 2002
`
`US 2002/0073847 A1
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`FIG. 1
`Prior Art
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`N
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`Sk1-1
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`7Y30
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`26
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`22
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`24
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`1.
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`28
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`US 2002/0073847 A1
`
`Jun. 20, 2002
`
`CELL WITHINA CELL MONOLTH STRUCTURE
`FOR AN EVAPORATIVE EMISSIONS
`HYDROCARBON SCRUBBER
`
`TECHNICAL FIELD
`0001. The disclosure relates to the evaporative emissions
`from a gasoline tank in motor vehicles and, more particu
`larly, to the Scrubber used in filtering the evaporative emis
`Sions.
`
`BACKGROUND
`0002 Motor vehicles emit hydrocarbons as a result of the
`evaporation of fuel. Generally, Such evaporative emissions
`result from the venting of fuel vapors from the fuel tank due
`to diurnal changes in ambient pressure and/or temperature,
`the vaporization of fuel by a hot engine and/or exhaust
`System, and the escape of fuel vapors during refueling of the
`vehicle. The venting of fuel vapor from the fuel tank due to
`diurnal pressure and/or temperature changes (i.e., diurnal
`emissions) is responsible for a majority of evaporative
`emissions. Diurnal changes in pressure and/or temperature
`cause air to flow into and out of the fuel tank. Air flowing
`out of the fuel tank inevitably carries fuel vapor, which is
`created by the evaporation of fuel into the air contained
`above the fuel within the fuel tank. If this flow of air is left
`untreated and is allowed to escape directly into the atmo
`Sphere, undesirable emissions occur.
`0.003 Motor vehicle manufacturers have reduced the
`level of diurnal emissions through the use of evaporative
`canisterS Such as the evaporative canister Structure and
`operation set forth in U.S. Pat. No. 5,910,637, the disclosure
`of which is incorporated herein by reference. Generally, an
`evaporative canister has a vapor inlet, a purge port and a vent
`port. The vapor inlet is fluidly connected by a vapor conduit
`to the air Space in the fuel tank. Diurnal changes in pressure
`and/or temperature causes air within the fuel tank to flow
`through the vapor conduit and into the evaporative canister
`via the vapor inlet. The air carries fuel vapor and/or hydro
`carbons. The evaporative canister contains a Sorbent mate
`rial, Such as an activated carbon, that Strips fuel vapor from
`the air as it flows through the canister. The treated air then
`flows out the vent port and into the atmosphere. The purge
`port is fluidly connected by a valved purge conduit to the
`combustion air intake of the motor vehicle engine. When the
`engine is running, the combustion air intake is at Sub
`atmospheric pressure, and the valve is opened to thereby
`connect the purge port to the combustion air intake. Fresh air
`is drawn by the Sub-atmospheric pressure through the vent
`port and into the evaporative canister. The fresh air flows
`through the Sorbent material, out the purge port and into the
`combustion air inlet. The flow of fresh air through the
`evaporative canister Strips the Sorbent material of Stored fuel
`Vapor and/or hydrocarbons, thereby purging the evaporative
`canister of hydrocarbons.
`0004. Due to incomplete desorption of the hydrocarbons,
`minute levels of hydrocarbons remain stored in the sorbent
`material of a purged evaporative canister. Bleed emissions
`are believed to result from the release of these stored
`hydrocarbons (i.e., the hydrocarbon heel) from the evapo
`rative canister into the atmosphere. Bleed emissions typi
`cally occur, for example, during the heating of the fuel tank
`during a diurnal cycle. The heating of the fuel tank causes air
`
`to flow from the fuel tank, through the canister, out the vent
`port and into the atmosphere. The air carries the hydrocar
`bon heel out of the canister and into the atmosphere, thereby
`resulting in the release of bleed emissions.
`0005. In order to reduce bleed emissions some motor
`vehicles employ an auxiliary canister. The auxiliary canister
`is placed in series with and further filters the treated air
`flowing out the vent port of the main evaporative canister.
`The auxiliary canister typically uses the same Sorbent mate
`rial (i.e., granular or pelletized carbon) as is used in the main
`evaporative canister to thereby increase the hydrocarbon
`capacity of the evaporative emission control System. How
`ever, in order to achieve Sufficient hydrocarbon capacity,
`auxiliary canisters are generally highly restrictive to the flow
`of air. Thus, the auxiliary canister must be bypassed in order
`to be compatible with vehicle refueling vapor recovery
`Systems. Bypassing an auxiliary canister requires the addi
`tion of valves and conduits to the evaporative emissions
`control System, and thus adds cost and complexity to the
`system. Furthermore, the restrictive airflow characteristic of
`the auxiliary canister makes purging the Volume of Sorbent
`material inefficient, especially in Small displacement
`engines. Moreover, vehicles which incorporate a more effi
`cient evaporative canister and/or an auxiliary canister typi
`cally do not reduce bleed emissions to a level required to
`classify the vehicle as a Super Ultra Low Emissions Vehicle
`(SULEV) or as a Practically Zero Emissions Vehicle
`(PZEV).
`0006 AS illustrated in FIG. 1, a prior art cell monolith
`10, e.g., as disclosed in U.S. Pat. No. 5,914.294 to Park et
`al., has a plurality of passages 12 extending through the
`monolith 10 from a frontal end 14 to a rearward end 16. The
`passages 12 are formed by Surrounding walls 18. The
`passages are encased by an Outer Skin 20. While this design
`is adequate for its intended purpose, there is a continued
`need for structurally sound monolith, which reduces bleed
`emissions and should have a low flow restriction, thereby
`increasing purge efficiency.
`
`SUMMARY
`0007. The drawbacks and disadvantages of the prior art
`are overcome by the exemplary embodiments of a cell
`within a cell monolith Structure for an evaporative emissions
`hydrocarbon Scrubber. A monolith for use in an evaporative
`emissions hydrocarbon Scrubber is disclosed. A shell is
`concentrically disposed around a monolith. The monolith
`has at least one cell group disposed around at least two
`individual cells, Such that the cell group comprises at least
`three thick walls. The individual cells comprise at least one
`thin wall, with the thick walls being thicker than the thin
`wall.
`0008. The method for using the evaporative emissions
`hydrocarbon scrubber is also disclosed. The method com
`prises introducing a gas to a first end of a monolith com
`prising carbon. The monolith, which is concentrically dis
`posed within a shell, has at least one cell group disposed
`around at least two individual cells. The cell group com
`prises at least three thick walls, and the individual cells
`comprises at least one thin wall. The thick wall is thicker
`than the thin wall. Hydrocarbons are removed from the gas
`with the monolith prior to exhausting the gas through a
`second end of the monolith. The hydrocarbons can be
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`US 2002/0073847 A1
`
`Jun. 20, 2002
`
`removed from the monolith by passing air from the Second
`end through the monolith and out the first end.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0009 Referring now to the figure, which is meant to be
`exemplary, not limiting.
`0.010
`FIG. 1 is a perspective view of a prior art cell
`monolith Structure.
`0.011
`FIG. 2 is a cross-sectional view of the cell within
`a cell monolith Structure.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`0012. When evaporative emissions are released from the
`fuel tank due to diurnal pressure and/or temperature
`changes, the emissions can be captured in an evaporative
`canister. The monolith can be employed in the main evapo
`rative canister, an auxiliary canister, or a combination
`thereof. While different designs of monoliths exist, includ
`ing circular or rectangular designs, reference to a particular
`monolith design is intended to also represent Similar com
`ponents in other monolith designs, where applicable. Addi
`tionally, this monolith design can be employed as a Single
`and only canister, or in conjunction with additional canisters.
`0013 FIG. 1 illustrates a cross-sectional view of the cell
`within a cell monolith structure 20 for an evaporative
`emissions hydrocarbon scrubber. The monolith 20 com
`prises a combination of thin walls 24 and thick walls 22.
`These walls, which preferably run the length of the monolith
`20, can be disposed perpendicular to the axis of the mono
`lith. Typically, the walls 22, 24 are disposed horizontal and
`Vertical, at an angle perpendicular to the axis. The thicker
`walls 22 define cell groups 26 comprising Several cells 28
`defined by the thin walls 24. Depending upon the specific
`Size and geometry of the monolith, the number of connected
`main cell groups 26 can vary. The quantity of thin and thick
`walls is a balance between the desired Structural integrity
`and the Surface area desired to adsorb a Sufficient amount of
`hydrocarbons in the fuel vapors. Generally, there are more
`thinner walls 24 disposed within the monolith 20 than
`thicker walls 22.
`0.014. The geometry of the cells, both those defined by
`thick walls 22 and those defined by thin walls 24, is also
`based upon the desired Structural integrity, Surface area, and
`optionally upon ease of manufacture. Possible designs range
`from rounded to multi-sided figures, e.g., Square, rectangle,
`oblong, circular, triangular, hexagonal, octagonal, and the
`like, as well as combinations comprising at least one of the
`foregoing geometries defining either the individual cells 28
`and/or the main cell groups 26. For example, the interlaced
`thick and thin walls 22, 24 can perpendicularly intersect
`creating a Square design as illustrated by individual cell 28,
`with the exception of when the interlaced thick and thin
`walls 22, 24 intersect with the outer wall 30. Additionally,
`the thin walls 24 can form different shaped cells than the cell
`groupS 26. For example, the cell group 26 may comprise a
`rectangular geometry while the cells 28 within the cell group
`26 may comprise a Square geometry.
`0.015 The location and orientation of the thick and thin
`walls 22, 24 can be dependent upon the overall shape of the
`monolith 20, Such as, e.g., circular, oval, rectangular, trap
`
`eZoidal, non-circular, and other Similar geometric configu
`rations, and the like. The cell shape and size is based upon
`the overall cell density. The number of cells within the
`monolith can be about 200 to about 600 individual cells,
`with about 200 to about 400 individual cells preferred. The
`number of individual cells within each cell group can vary,
`with at least four individual cells per cell group preferred,
`and at least nine individual cells per cell group especially
`preferred.
`0016. The thickness of the thick and thin walls 22, 24 is
`typically dependent upon the desired overall Structural integ
`rity of the monolith 20. The thickness is preferably sufficient
`to impart the desired overall Structural integrity, without
`inhibiting the passage of evaporative emissions. Preferably,
`the thickness of the thicker walls 22 can be about 0.008
`inches (in.) or greater, with about 0.008 in. to about 0.020 in.
`preferred, and about 0.010 in. to about 0.012 in. especially
`preferred. The thickness of the thinner walls 24 can be less
`than about 0.008 in., with about 0.001 in. to about 0.008 in.
`preferred, and about 0.003 in. to about 0.004 in. especially
`preferred.
`0017. The monolith 20 can be comprised of a sorbent that
`removes hydrocarbons from an air/vapor flow, including, but
`not limited to, activated carbon, and the like. This sorbent
`can be mixed with a binder to allow for the formation into
`the desired shape. The various amounts of Sorbent and
`binder can readily be determined by an artisan based upon
`the desired Structural integrity of the monolith and the
`monolith production method. One example of a monolith
`production process is disclosed in U.S. Pat. No. 5,914,294 to
`Park et al., which is hereby incorporated by reference.
`0018. Once formed into the cell within a cell structure,
`the monolith is concentrically disposed within a Shell or
`housing (i.e., a canister), and disposed in fluid communica
`tion with the fuel tank and the atmosphere external to the
`motor vehicle. During operation, fuel vapor and air flow into
`a first end of the canister, and through the monolith, where
`the Sorbent Strips the hydrocarbons from the gas Stream,
`releasing the treated air to the atmosphere. The canister is
`fluidly connected by a valved purge conduit to the combus
`tion air intake of the motor vehicle engine. When the engine
`is running, the combustion air intake is at Sub-atmospheric
`preSSure, and the valve is opened to thereby connect the
`purge port to the combustion air intake. Fresh air is drawn
`by the Sub-atmospheric pressure through the vent port and
`into the Second end of the evaporative canister. The fresh air
`flows through the monolith, Stripping the Sorbent of Stored
`hydrocarbons.
`0019. The thinner walls 24 increases the desorption capa
`bility of the monolith 20, allowing for a more thorough
`cleaning of the monolith of hydrocarbons. The performance
`of the monolith 20 improves as the desorption capability is
`increased, since the ability to capture the fuel Vapor and/or
`hydrocarbons is more rapidly restored. The use of the thicker
`walls 22, defining the main cell groups 26, increases the
`structural integrity of the monolith 20 without compromis
`ing the open area for air flow. The plurality of the main cell
`groupS 26 does not add any significant pressure differential
`across the monolith 20, when compared to a monolith with
`uniform thicknesses, as illustrated in the prior art FIG. 1.
`0020 While preferred embodiments have been shown
`and described, various modifications and Substitutions may
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`US 2002/0073847 A1
`
`Jun. 20, 2002
`
`be made thereto without departing from the Spirit and Scope
`of the invention. Accordingly, it is to be understood that the
`apparatus and method have been described by way of
`illustration only, and Such illustrations and embodiments as
`have been disclosed herein are not to be construed as
`limiting to the claims.
`What is claimed is:
`1. An evaporative emissions hydrocarbon Scrubber, com
`prising:
`a monolith comprising carbon having at least one cell
`group disposed around at least two individual cells,
`wherein Said cell group comprises at least three thick
`walls, and Said individual cells comprising at least one
`thin wall, said thick wall being thicker than said thin
`wall; and
`a shell concentrically disposed around Said monolith.
`2. The evaporative emissions hydrocarbon scrubber of
`claim 1, wherein Said thick walls are greater than about
`0.008 in. to about 0.020 in. in thickness.
`3. The evaporative emissions hydrocarbon scrubber of
`claim 2, wherein said thick walls are about 0.010 in. to about
`0.012 in. in thickness.
`4. The evaporative emissions hydrocarbon scrubber of
`claim 1, wherein said thin walls are about 0.001 in. up to
`about 0.008 in. in thickness.
`5. The evaporative emissions hydrocarbon scrubber of
`claim 4, wherein said thin walls are about 0.003 in. to about
`0.004 in. in thickness.
`6. The evaporative emissions hydrocarbon scrubber of
`claim 1, wherein Said monolith further comprises activated
`carbon and a binder.
`
`7. The evaporative emissions hydrocarbon scrubber of
`claim 1, wherein at least four of Said individual cells are
`disposed within each of Said cell groups.
`8. The evaporative emissions hydrocarbon scrubber of
`claim 1, wherein at least nine of Said individual cells are
`disposed within each of Said cell groups.
`9. The evaporative emissions hydrocarbon scrubber of
`claim 1, wherein said monolith comprises about 200 to about
`600 of said individual cells.
`10. The evaporative emissions hydrocarbon scrubber of
`claim 9, wherein said monolith comprises about 200 to about
`400 of said individual cells.
`11. A method for using an evaporative emissions hydro
`carbon Scrubber, comprising:
`introducing a gas to a first end of a monolith comprising
`carbon, Said monolith having at least one cell group
`disposed around at least two individual cells, wherein
`Said cell group comprises at least three thick walls, and
`Said individual cells comprising at least one thin wall,
`Said thick wall being thicker than Said thin wall, Said
`monolith concentrically disposed within a shell;
`removing hydrocarbons from Said gas,
`exhausting Said gas through a Second end of Said mono
`lith;
`introducing air through Said Second end of Said monolith,
`and
`removing Said hydrocarbons from Said monolith.
`12. The method of claim 11, wherein said monolith
`further comprises activated carbon and a binder.
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