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`

`

`Case Docket No. CHR 2001-79
`
`IN THE UNITED STATES PATENT AND TRADEMARK OFFICE
`
`Patent Application for
`
`METHOD FOR REDUCING EMISSIONS
`FROM EVAPORATIVE EMISSIONS CONTROL SYSTEMS
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`This invention relates to a method for reducing emissions from evaporative control
`
`systems including activated carbon particulate-filled canisters and adsorptive monolith(cid:173)
`
`containing canisters, which monoliths include activated carbon, and to using said adsorbing
`
`canisters to remove volatile organic compounds, and other chemical agents from fluid streams.
`
`More particularly, this invention relates to using said vapor-adsorbing materials in hydrocarbon
`
`fuel consuming engines.
`
`2. Description of Related Art (Including Information Disclosed Under 37 CFR 1.97
`and 37 CFR 1.98)
`
`(a)
`
`Standard Working Capacity Adsorbents
`
`Evaporation of gasoline from motor vehicle fuel systems is a major potential source of
`
`hydrocarbon air pollution. The automotive industry is challenged to design engine components
`
`and systems to contain, as much as possible, the almost one billion gallons of gasoline
`
`evaporated from fuel systems each year in the United States alone. Such emissions can be
`
`controlled by canister systems that employ activated carbon to adsorb and hold the vapor that
`
`evaporates. Under certain modes of engine operation, the adsorbed hydrocarbon vapor is
`
`periodically removed from the carbon by drawing air through the canister and burning the
`
`desorbed vapor in the engine. The regenerated carbon is then ready to adsorb additional vapor.
`
`Under EPA mandate, such control systems have been employed in the U.S. for about 30 years,
`
`1
`
`

`

`Case Docket No. CHR 2001-79
`
`and during that time government regulations have gradually reduced the allowable emission
`
`levels for these systems. In response, improvements in the control systems have been largely
`
`focused on improving the capacity of the activated carbon to hold hydrocarbon vapor. For
`
`example, current canister systems, containing activated carbon of uniform capacity, are readily
`
`capable of capturing and releasing 100 grams of vapor during adsorption and air purge
`
`regeneration cycling. These canister systems also must have low flow restrictions in order to
`
`accommodate the bulk flow of displaced air and hydrocarbon vapor from the fuel tank during
`
`refueling. Improvements in activated carbons for automotive emission control systems are
`
`disclosed in U.S. Patent 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; 5,691,270; 5,736,481; 5,736,485; 5,863,858;
`
`5,914,294; 6,136,075; 6,171,373; 6,284,705.
`
`A typical canister employed in a state of the art auto emission control system is shown
`
`in Figure 1. Canister 1 includes support screen 2, dividing wall 3, a vent port 4 to the
`
`atmosphere (for when the engine is off), a vapor source connection 5 (from the fuel tank), a
`
`vacuum purge connection 6 (for when the engine is running), and adsorbent material fill 7.
`
`Other basic auto emission control system canisters are disclosed in U.S. Patent Nos.:
`
`5,456,236;· 5,456,237; 5,460,136; and 5,477,836.
`
`Typical carbons for evaporative emission canisters are characterized by standard
`
`measurements of bed packing density ("apparent density," g/mL), equilibrium saturation
`
`capacity for 100% butane vapor ("butane activity," g/lO0g-carbon), and purgeability ("butane
`
`ratio"), specifically, the proportion of adsorbed butane from the saturation step which can be
`
`recovered from the carbon by an air purge step. The multiplicative product of these three
`
`properties yields a measure of the carbon's effective butane "working capacity" ("BWC", g/dL),
`
`2
`
`

`

`Case Docket No. CHR 2001-79
`
`measured by ASTM D5228-92, which has been established in the art as a good predictor of the
`
`canister working capacity for gasoline vapors. Carbons that excel for this application have high
`
`BWC, typically 9 to 15+ g/dL BWC, as a result of high saturation capacities on a volumetric(cid:173)
`
`basis for butane (the product of density and butane activity), and high butane ratios (>0.85). In
`
`terms of isothermal equilibrium adsorption capacities across all vapor concentrations, these
`
`carbons characteristically have high incremental capacity as a function of increased vapor
`
`concentration (i.e., isotherm curved upward on a semi-log graph). This isotherm upward curve
`
`reflects the high working capacity performance feature of these carbons, in that gasoline vapors
`
`are adsorbed in high quantity at high concentrations but readily released in high concentration
`
`to an air purge stream. In addition, these carbons tend to be granular (somewhat irregularly
`
`shaped) or cylindrical pellet, typically of a size just about 1-3 mm in diameter. It has been
`
`found that somewhat larger sizes hinder diffusional transport of vapors into and out of the
`
`carbon particle during dynamic adsorb and purge cycles. On the other hand, somewhat smaller
`
`size particles have unacceptably high flow restriction for displaced air and hydrocarbon vapors
`
`during refueling.
`
`(b)
`
`Diurnal Breathing Loss (DBL) Requirements
`
`Recently, regulations have been promulgated that require a change in the approach with
`
`respect to the way in which vapors must be controlled. Allowable emission levels from
`
`canisters would be reduced to such low levels that the primary source of emitted vapor, the fuel
`
`tank, is no longer the primary concern, as current conventional evaporative emission control
`
`appears to have achieved a high efficiency of removal. Rather, the concern now is actually the
`
`hydrocarbon left on the carbon adsorbent itself as a residual "heel" after the regeneration
`
`(purge) step. Such emissions typically occur when a vehicle has been parked and subjected to
`
`3
`
`

`

`Case Docket No. CHR 2001-79
`
`diurnal temperature changes over a period of several days, commonly called "diurnal breathing
`
`losses." Now, the California Low Emission Vehicle Regulation makes it desirable for these
`
`diurnal breathing loss (DBL) emissions from the canister system to be below 10 mg ("PZEV")
`
`for a number of vehicles beginning with the 2003 model year and below 50 mg, typically below
`
`20 mg, ("LEV-II") for a larger number of vehicles beginning with the 2004 model year.
`
`("PZEV" and "LEV-II" are criteria of the California Low Emission Vehicle Regulation.)
`
`While standard carbons used in the commercial canisters excel in terms of working
`
`capacity, these carbons are unable to meet DBL emission targets under normal canister
`
`operation. Furthermore, none of the standard measures of working capacity properties correlate
`
`with DBL emission performance. Nonetheless, one option for meeting emission targets is to
`
`significantly increase the volume of purge gas during regeneration in order to reduce the
`
`amount of residual hydrocarbon heel in the carbon bed and thereby reduce subsequent
`
`emissions. This strategy, however, has the drawback of complicating management of the
`
`fuel/air mixture to the engine during purge regeneration and tends to adversely affect tailpipe
`
`emissions, i.e., moving or redefining the problem rather than solving it. (See U.S. Patent No.
`
`4,894,072.)
`
`Another option is to design the carbon bed so that there is a relatively low cross(cid:173)
`
`sectional area on the vent-side of the canister system (the first portion of the bed to encounter
`
`purge air), either by redesign of the existing canister dimensions or by the installation of a
`
`supplemental, auxiliary vent-side canister of appropriate dimensions. This alternative has the
`
`effect of locally reducing residual hydrocarbon heel by increasing the intensity of purge for that
`
`vent-side portion of the bed, thereby improving its ability to retain vapors that would otherwise
`
`be emitted from the canister system under diurnal breathing conditions. The drawback is that
`
`4
`
`

`

`Case Docket No. CHR 2001-79
`
`there is a useful limit to which a portion of the bed can be elongated at reduced cross-sectional
`
`area without otherwise incurring excessive flow restriction by the canister system. In practice,
`
`this limit does not allow employing a sufficiently narrowed and elongated geometry to meet
`
`emission targets. (See U.S. Patent No. 5,957,114.)
`
`Another option for increasing the purge efficiency of a fuel vapor/air mixture fraction
`
`adsorbed in the pores of the adsorbent material is suggested by the teachings of U.S. Patent
`
`Nos. 6,098,601 and 6,279,548 by providing a heating capability internal of the canister, or a
`
`section thereof, either to increase pressure in the vapor storage canister to expel hot vapor
`
`through the vapor/purge conduit back into the fuel tank where it condenses at the lower ambient
`
`temperature therein ('601) or to increase the purging efficiency of hydrocarbons from the heated
`
`adsorbent material and carry the purged fuel vapor to the induction system of an associated
`
`engine (' 548). However, this increases the complexity of control system management, and
`
`there appears some inherent safety concerns in providing heating internal of a canister for
`
`trapping fuel vapors.
`
`Thus, an acceptable remedy, which does not have drawbacks as the cited alternative
`
`approaches, is greatly desired. It is submitted that the invention disclosed and claimed herein
`
`provides the desired solution.
`
`SUMMARY OF THE INVENTION
`
`An invention is disclosed for sharply reducing diurnal breathing loss emissions from
`
`evaporative emissions canisters by the use of multiple layers, or stages, of adsorbents. On the
`
`fuel source-side of the canister, standard high working capacity carbons are preferred. On the
`
`vent-side, the preferred adsorbent volume exhibits a flat or flattened adsorbent isotherm on a
`
`volumetric basis in addition to certain characteristically desirable adsorptive properties across
`
`5
`
`

`

`Case Docket No. CHR 2001-79
`
`broad vapor concentrations, specifically relatively low incremental capacity at high
`
`concentration vapors compared with the fuel source-side adsorbent volume. Two approaches
`
`are described for attaining the preferred properties for the vent-side adsorbent volume. One
`
`approach is to use a filler and/or bed voidages as a volumetric diluent for flattening an isotherm.
`
`A second approach is to employ an adsorbent with the desired isotherm properties and to
`
`process it into an appropriate shape or form without necessarily requiring any special provision
`
`for dilution. Both such approaches provide a substantially lower emissions canister system
`
`without a significant loss in working capacity or an increase in flow restriction compared with
`
`prior art adsorbents used for automotive emissions control.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Figure 1 shows, in cross-section, a prior art canister system.
`
`Figure 2 shows, in cross-section, one embodiment of the invention canister comprising
`
`multiple adsorbents.
`
`Figure 3 shows butane isotherm properties for different activated carbon adsorbents.
`
`DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
`
`The disclosed invention relates to the use of multiple beds (or layers, stages, or
`
`chambers) of adsorbent materials, which, in combination, significantly reduce DBL emissions
`
`while maintaining the high working capacity and low flow restriction properties of the canister
`
`system. (See Figure 2.) These adsorbents include activated carbon from a variety of raw
`
`materials, including wood, peat, coal, coconut, synthetic or natural polymer, and a variety of
`
`processes, including chemical and/or thermal activation, as well as inorganic adsorbents,
`
`including molecular sieves, porous alumina, pillared clays, zeolites, and porous silica, and
`
`organic adsorbents, including porous polymers. The adsorbents may be in granular, spherical,
`
`6
`
`

`

`Case Docket No. CHR 2001-79
`
`or pelletized cylindrical shapes, or may be extruded into special thin-walled cross-sectional
`
`shapes, such as hollow-cylinder, star, twisted spiral, asterisk, configured ribbons, or other
`
`shapes within the technical capabilities of the art. In shaping, inorganic and/or organic binders
`
`may be used. The adsorbents may be formed into a monolith or honeycomb part. The
`
`adsorbents may be incorporated into a canister as one or more layers, or separate chambers, or
`
`they may be inserted in the fluid stream flow as auxiliary canister beds.
`
`One common feature for all of these approaches is to have a vent-side adsorbent with a
`
`relatively flat-shaped isotherm. This isotherm shape is important for reasons related to purge
`
`efficiency across the adsorbent bed depth. For an adsorbent with a flat adsorption isotherm, the
`
`concentration of hydrocarbon vapor in equilibrium with adsorbed hydrocarbon, by definition,
`
`decreases further as the adsorbed hydrocarbon is removed compared with an adsorbent with a
`
`more steeply sloped isotherm. Thus, when such a material is employed as an adsorbent volume
`
`on the vent-side region of a canister, 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 that eventually
`
`emerges as bleed, decreasing this concentration reduces the bleed emission level. The degree of
`
`removal of adsorbed hydrocarbon during purge is determined by the difference between the
`
`concentration of hydrocarbon picked up in the purge gas and the concentration in equilibrium
`
`with the adsorbent at any point in the bed. Thus, adsorbent in the immediate vicinity of the
`
`purge inlet will be most thoroughly regenerated. At points deeper in the adsorbent bed, less
`
`hydrocarbon will be removed because the purge gas will already contain hydrocarbon removed
`
`from previous points in the bed. An adsorbent with a flatter adsorption isotherm will give up
`
`less vapor into the purge stream and this purge will then be more efficient in reducing vapor
`
`concentrations deeper into the bed. Therefore, for a given quantity of purge gas, it will be
`
`7
`
`

`

`Case Docket No. CHR 2001-79
`
`possible to reduce the vapor concentration in a volume of adsorbent with a flat adsorption
`
`isotherm to a lower level than the concentration in the same volume of an adsorbent with a
`
`steep adsorption isotherm. Bleed emission from such a volume will therefore be lower when
`
`the adsorbent has a flatter adsorption isotherm.
`
`A region within a canister containing particulate or in an adsorbent-containing monolith
`
`with the preferred adsorption isotherm properties for achieving low bleed emission levels will,
`
`however, have a relatively low adsorption working capacity compared to the activated carbons
`
`commonly used in automotive evaporative emission control. For example, the BWC of a low
`
`capicity adsorbent will be about 6 g/d.L compared to the 9 g/d.L to 15+ g/d.L range as used in
`
`typical automotive carbons. Therefore, in order to maintain the required hydrocarbon capacity
`
`for normal emission control system operation, the low-bleed adsorbent will be used in a vent(cid:173)
`
`side auxiliary region within the canister or outside the canister in combination with an fuel
`
`source-side region containing a volume of the high capacity carbon normally employed. When
`
`two different adsorbents are used, for example, system design will involve providing sufficient
`
`volume of the high capacity carbon in the main part, or fuel source-side, of an emisssion control
`
`canister to achieve the desired working capacity, and a sufficient volume of the low-bleed
`
`adsorbent to contain vapor emitted from the main bed to such an extent that such vapor does
`
`not materially affect the bleed emissions from the low-bleed adsorbent.
`
`In the context of the invention, "monolith" is intended to include foams, woven and
`
`non-woven fibers, mats, blocks and bound aggregates of particulates.
`
`It is notable that the emission of vapor from the main, high-capacity fuel source-side
`
`volume of adsorbent into the auxiliary lower capacity vent-side volume is significantly affected
`
`by the presence of that vent-side volume. During purge, a vent-side adsorbent volume having a
`
`8
`
`

`

`Case Docket No. CHR 2001-79
`
`flat adsorption isotherm will give up a relatively small hydrocarbon load into the purge gas.
`
`Therefore, the concentration of vapor carried by the purge gas will be low as it emerges from
`
`the low-bleed vent-side volume and enters the high-capacity, fuel source-side volume. This
`
`allows good regeneration of the high-capacity adsorbent in the vicinity of the junction of the
`
`two adsorbent volumes, and helps protect the vent-side volume from emissions from the fuel
`
`source-side region of the canister during diurnal breathing flow. Specifically, the greater
`
`regeneration efficiency of the fuel source-side volume reduces diurnal emissions by retarding
`
`the rate of bulk phase diffusion across the flow length of the canister system. Since bulk phase
`
`diffusion is a major mode of vapor transport during diurnal breathing conditions, by reducing
`
`the vapor concentration difference across the flow length of the canister system by enhanced
`
`regeneration, the redistribution of vapors within the canister system and subsequent emissions
`
`into the vent-side volume and out of the vent port are reduced.
`
`Examples of adsorbents with isotherms having the preferred shape to provide low bleed
`
`performance are compared with standard canister-fill carbons (Westvaco Corporation's BAX
`
`1100 and BAX 1500) in Figure 3. It is important to note that, as shown in this figure, the
`
`isotherm properties must be defined in terms of volumetric capacity. On this basis, the
`
`preferred low-bleed adsorbent portion will have an incremental n-butane capacity of less than
`
`about 35 g/liter between 5 and 50 volume percent n-butane vapor concentration.
`
`While in some instances, known adsorbents may have the preferred properties for the
`
`vent-side, these adsorbents would not be expected to be useful in an evaporative canister. In
`
`some cases, these materials have low purgeability (butane ratio less than 0.85) and low working
`
`capacity (BWC less than 9 g/dL) as measured by the standard BWC test for qualifying canister
`
`carbons. Common wisdom and experience in the art associate low butane ratio with high
`
`9
`
`

`

`Case Docket No. CHR 2001-79
`
`residual hydrocarbon heel, which is the potential source for high emissions. Furthermore, low
`
`BWC adsorbents were not considered useful for inclusion into a canister system as working
`
`capacity for gasoline vapors would be assumed impaired, with no expectation that there would
`
`be a utility for reducing emissions. In fact, one preferred embodiment of this invention, lower
`
`capacity adsorbents have BWC values preferably below 8 g/dL, which is well below the 9-15+
`
`g/dL BWC level normally deemed suitable for use in evaporative emission control canister
`
`systems. The preferred selection of these low BWC materials for inclusion into a canister
`
`system as a vent-side layer to produce low emissions was only realized once the dynamics
`
`within the adsorbent bed were realized (i.e., the significance of low residual vapor
`
`concentration within the vent-side bed volume and the interactive effect that the vent-side bed
`
`volume has on the distribution and diffusion of vapor across the entire canister system during
`
`the diurnal breathing loss period).
`
`Therefore, it has been found that the preferred vent-side adsorbent properties, in
`
`addition to a relatively low BWC, includes butane ratios between 0.40 and 0.98, which in total
`
`are substantially different properties compared with adsorbents previously conceived as useful
`
`for these canister systems.
`
`The proposed alternative approaches described above are shown to be effective in
`
`canister bleed emission control in the following examples. One approach for preparing the
`
`vent-side adsorbent is to volumetrically dilute a high working capacity adsorbent so that its
`
`resulting isotherm is flattened on a volumetric basis. A second approach is to begin with an
`
`adsorbent that has the desired adsorption capacity and flat isotherm shape and process it into a
`
`shape or form, such as a pellet or honeycomb.
`
`10
`
`

`

`Case Docket No. CHR 2001-79
`
`A particular preferred embodiment for a canister with multiple adsorbents is shown in
`
`Figure 2. Figure 2 shows a canister system comprising a primary canister body 1, a support
`
`screen 2, a dividing wall 3, a vent port 4 to the atmosphere, a vapor source connection 5, a
`
`vacuum purge connection 6, a fuel source-side region 7, vent-side canister regions 8 -11 of
`
`varying low-capacities, supplemental canister body 12, and connecting hose 13 permitting fluid
`
`stream flow from the primary canister body 1 to the supplemental canister body 12. Additional
`
`embodiments, as discussed above, are also envisioned to be within the scope of the subject of
`
`the invention.
`
`The desired results for the subject matter of the invention can be attained with a single
`
`vent-side uniform lower capacity adsorbent material as the subsequent adsorbent material. The
`
`option of multiples of lower capacity adsorbents with the desirable adsorptive properties across
`
`broad vapor concentrations is demonstrated merely as one embodiment.
`
`The measures for gasoline working capacity (GWC) and emissions in the Table were
`
`derived from the Westvaco DBL test that uses a 2.lL canister. The pellet examples were tested
`
`as a 300 rnL vent-side layer within the canister, with the 1800 rnL of BAX 1500 pellets as the
`
`remaining canister fill. The honeycomb was tested as an auxiliary bed canister that was placed
`
`in-line with the 2.lL main canister of BAX 1500 pellets. For all examples, the canister system
`
`was uniformly first preconditioned by repetitive cycling of gasoline vapor adsorption and air
`
`purge (400 bed volumes air). This cycling generated the GWC value. Butane emissions were
`
`subsequently measured after a butane adsorption and an air purge step, specifically during a
`
`diurnal breathing loss period when the canister system was attached to a temperature-cycled
`
`fuel tank. The reported value is the 2nd day DBL emissions during an 11-hour period when the
`
`fuel tank was warmed and vapor-laden air was vented to the canister system and exhausted
`
`11
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`Case Docket No. CHR 2001-79
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`from the vent-side adsorbent where the emissions were measured. The procedure employed for
`
`measuring DBL emissions has been described in SAE Technical Paper 2001-01-0733, titled
`
`"Impact and Control of Canister Bleed Emissions," by R. S. Williams and C. R. Clontz.
`
`Example 1: Microsphere Filler Pellets. These 2 mm pellets are an example of the
`
`volumetric dilution method by adding a solid filler to the extrusion formulation. The pellets
`
`were prepared from an extrusion blend consisting of Westvaco SA-1500 powder (12.8 wt%),
`
`solid glass microsphere filler (79.7 wt% PQ Corporation A3000), bentonite clay (7.2 wt%), and
`
`phosphoric acid (0.3 wt%). The pellets were tumbled for four minutes, dried overnight at
`
`105°C, and subsequently heat-treated in steam at 650°C for 15 minutes. An appropriate non(cid:173)
`
`adsorbing filler reduces adsorption capacities across all vapor concentrations, resulting in a
`
`flattened adsorption isotherm ("Example l" in Figure 3). Alternative methods for diluting the
`
`vent-side region are to co-mix adsorbent granules or pellets with inert filler particles of similar
`
`size, to form the extrusion paste into high voidage shapes such as hollow cylinders, asterisks,
`
`stars, or twisted, bent, or spiral ribbon pieces, or to place multiple thin layers of non-adsorbing
`
`particles or porous mats (e.g., foam), or simply trapped air space between layers of adsorbent.
`
`Example 2: Ceramic-Bound Honeycomb. The 200 cpsi (cells per square inch) carbon(cid:173)
`
`containing honeycomb is another example of the volumetric dilution method. The honeycomb
`
`in the Table was prepared according to the method described in U.S. Patent No. 5,914,294,
`
`which discloses forming an adsorptive monolith comprising the steps of (a) extruding an
`
`extrudable mixture through an extrusion die such that a monolith is formed having a shape
`
`wherein the monolith has at least one passage therethrough and the extrudable mixture
`
`comprises activated carbon, a ceramic forming material, a flux material, and water, (b) drying
`
`the extruded monolith, and (c) firing the dried monolith at a temperature and for a time period
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`Case Docket No. CHR 2001-79
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`sufficient to react the ceramic fonning material together and form a ceramic matrix. The
`
`extrudable mixture is capable of maintaining the shape of the monolith after extrusion and
`
`during drying of the monolith.
`
`In this example, the extrusion formulation ingredients partially dilute the carbon
`
`adsorbent, and in addition, the adsorbent is further diluted by the open cell structure of the
`
`extruded part. These cells create more bed voidages within the part, compared with a similar
`
`bed volume of pellets (65 vol% voidages for the honeycomb versus 35 vol% for pellets or
`
`granules). The cell structure and high bed voidages have the added advantage of imposing
`
`minimal additional flow restriction compared with a bed of pellets, thereby allowing the
`
`honeycomb to be installed to the main canister as an add-on auxiliary device of greatly reduced
`
`cross-sectional area (see supplemental canister body 12 in Figure 2).
`
`Example 3: Special Precursor Pellets: These 2 mm pellets were prepared by selecting
`
`the adsorbent to be extruded according to its intrinsic flat isotherm adsorption properties. In
`
`this example, there was no special provision for filler in the formulation or bed voidage dilution
`
`from the extruded shape. The ingredients for the extrusion blend producing the tested activated
`
`carbon pellets consisted of SX 1 grade activated carbon produced by NORIT (93.2 wt%) and
`
`sodium carboxymethyl cellulose binder system (6.8 wt%). The pellets were tumbled for four
`
`minutes, dried overnight at 105°C, and subsequently heat-treated in air at 150°C for three hours.
`
`As noted above, the comparisons of these activated carbon containing materials,
`
`prepared as set forth in the examples, is shown in the following Table.
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`Case Docket No. CHR 2001-79
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`TABLE
`
`Perlormance, Properties, and Formulations for Alternative Vent-Side Adsorbents
`
`Filled
`Pellet
`
`Ceramic-
`Bound
`Honeycomb
`
`Prior Art: High
`Special
`Precursor Working Capacity Carbons
`Pellet
`
`Fuel source-side BAX 1500
`Volume:
`
`1800mL
`
`2100mL
`
`1800 mL
`
`1800 mL
`
`1800 mL
`
`Vent-Side Adsorbent Type:
`
`"Ex. 1"
`
`"Ex. 2"
`
`"Ex. 3"
`
`BAX 1100
`
`BAX 1500
`
`Vent-Side Mode:
`
`Layer
`
`Auxiliary Bed
`
`Layer
`
`Layer
`
`Layer
`
`Vent-Side Adsorbent Volume:
`
`300mL
`
`300mL
`
`300mL
`
`300mL
`
`200mL
`41mm diameter
`x 150 mm long,
`200 cpsi
`
`Canister System Performance: Westvaco DBL Test
`
`Gasoline Working Capacity, g:
`
`138
`
`2nd Day DBL Emissions, mg-C4:
`
`Note:
`
`29
`
`(1)
`
`144
`
`10
`
`(2)
`
`132
`
`13
`
`(3)
`
`143
`
`88
`
`(4)
`
`139
`
`221
`
`(5)
`
`Vent-Side Properties (6)
`
`Incremental Adsorption At 25°C
`
`5 -50 vol% butane vapor, g/L:
`
`24
`
`16
`
`18
`
`52
`
`80
`
`Apparent Density, g/mL:
`Butane Activity, g/lO0g:
`BWC, g/dL:
`Butane Ratio:
`
`0.869
`7.0
`5.7
`0.929
`
`0.355
`13.1
`4.0
`0.852
`
`0.453
`18.5
`5.0
`0.593
`
`0.358
`39.0
`11.9
`0.852
`
`0.284
`64.7
`16.0
`0.868
`
`(1) Two DBL Tests; Averaged data for GWC (400 bed volume purge) and DBL e1Illss10ns (150 bed volume purge); 2.lL
`canister, 1500 mL fuel source-side chamber, 600 mL vent-side chamber, fuel source-side chamber cross-sectional area 2.5
`times the vent-side cross-sectional area.
`(2) Single DBL Test
`(3) Average of three DBL Tests
`(4) Average of three DBL Tests
`(5) Average of six DBL Tests
`(6) Density and BWC by ASTM standard techn