Edited by
`Timothy D. Burchell
`
`-I -
`
`*
`
` MAHLE-1013
`U.S. Patent No. RE38,844
`
`

`

`Carbon Materials
`for Advanced
`Technologies
`
`

`

`Carbon Materials
`for Advanced
`Technologies
`
`Edited by
`Timothy D. Burchell
`Oak Ridge, National Laboratory
`Oak Ridge, TN 37831 -6088 U.S.A.
`
`1999
`
`PERGAMON
`A n I m p r i n t o f E l s e v i e r S c i e n c e
`Amsterdam - Lausanne - New York - Oxford - Shannon - Singapore - Tokyo
`
`

`

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`First edition 1999
`Library of congress Cataloging in Publication Data
`A catalog record from the Library of Congress has been applied for.
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`A catalogue record from the British Library has been applied for.
`
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`

`

`Contents
`
`xi
`
`xiii
`
`xv
`
`P
`
`Gon~ibutors ...................................................
`Acknowledgments .............................................
`pref~ce .......................................................
`1 Structure and Bonding in Carbon Materials .....................
`Brian Me ..E naney
`Introduction .............................................
`1
`1
`2 Crystalline Forms of Carbon ................................
`3
`3 The Phase and Transition Diagram for Carbon ................. 12
`4 CarbonFilms ...........................................
`14
`5 Carbon Nanoparticles ....................................
`18
`6 Engineering Carbons .....................................
`20
`7 ConcludingRemarks .....................................
`28
`8 Acknowledgments .......................................
`29
`9 References .............................................
`29
`2 Fullerenes and Nanotubes ...................................
`Mildred S . Dresselhaus . Peter C . Eklund and Gene Dresselhaus
`Introduction ............................................
`1
`Fullerenes and Fullerene-based Solids ........................
`2
`3 Carbon Nanotubes .......................................
`4 Applications ............................................
`5 Acknowledgments .......................................
`6 References .............................................
`3 Active Carbon Fibers .......................................
`Timothy J. Mays
`Introduction ............................................
`1
`2 Background ............................................
`Applications of Active Carbon Fibers .......................
`3
`4 ConcludingRemarks ....................................
`5 Acknowledgments ......................................
`6 References ............................................
`
`95
`96
`101
`110
`111
`111
`
`39
`
`35
`37
`61
`84
`87
`87
`
`95
`
`

`

`vi
`4 High Performance Carbon Fibers ............................
`Dan D . Edie and John J . McHugh
`
`119
`
`Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`119
`Processing Carbon Fibers from Polyacrylonitrile . . . . . . . . . . . . . . 119
`Carbon Fibers from Mesophase Pitch .......................
`123
`High Performance Carbon Fibers from Novel Precursors . . . . . . . . 133
`Carbon Fiber Property Comparison .........................
`133
`Current Areas for High Performance Carbon Fiber Research . . . . . 134
`Summary and Conclusions ...............................
`135
`References ............................................
`135
`5 Vapor Grown Carbon Fiber Composites ......................
`Max L . Lake and Jyh-Ming Ting
`
`139
`
`Introduction ...........................................
`139
`CurrentForms .........................................
`142
`Fiberproperties ........................................
`144
`Composite Properties ....................................
`146
`Potential Applications ...................................
`158
`Manufacturing Issues ....................................
`160
`Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`164
`References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`165
`6 Porous Carbon Fiber-Carbon Binder Composites ............... 169
`Timothy D . Burchell
`
`Introduction ...........................................
`169
`Manufacture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
`Carbon Bonded Carbon Fiber .............................
`173
`Damage Tolerant Light Absorbing Materials . . . . . . . . . . . . . . . . . 181
`Carbon Fiber Composite Molecular Sieves . . . . . . . . . . . . . . . . . . . 183
`Summary and Conclusions ............................... 200
`Acknowledgments ......................................
`201
`References ............................................
`201
`
`

`

`7 Coal-DerivedCarbons .....................................
`Peter G . Stansberry. John W . Zondlo and Alfred H . Stiller
`
`205
`
`1 Review of Coal Derived Carbons . . . . . . . . . . . . . . . . . . . . . . . . . .
`205
`2 SolventExtractionofCoal ................................ 211
`3 Preparation and Characteristics of Cokes Produced from Solvent
`Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`4 Preparation and Evaluation of Graphite from Coal-Derived
`Feedstocks ............................................
`229
`5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
`6 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`233
`7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`233
`8 Activated Carbon for Automotive Applications ................. 235
`Philip J. Johnson. David J. Setsuda and Roger S . Williams
`
`223
`
`Background ...........................................
`235
`Activated Carbon .......................................
`239
`Vehicle Fuel Vapor Systems ..............................
`244
`Adsorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`246
`Carbon Canister Design ..................................
`252
`Application of Canisters in Running Loss Emission Control . . . . . 257
`Application of Canisters in ORVR Control . . . . . . . . . . . . . . . . . . . 263
`Summary and Conclusions ...............................
`265
`References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`266
`9 Adsorbent Storage for Natural Gas Vehicles ................... 269
`Terv L . Cook. Costa Komodromos. David F . Quinn and
`Steve Ragun
`
`Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`269
`1
`2 Storage of Natural Gas ...................................
`274
`3 Adsorbents ............................................
`280
`4 Adsorbent Fill-Empty Testing .............................
`293
`5 GuardBeds ...........................................
`294
`6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
`7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`299
`
`

`

`303
`
`...
`vlll
`10 Adsorption Refrigerators and Heat Pumps ....................
`Robert E . Critoph
`Why Adsorption Cycles? .................................
`1
`303
`2 The Basic Adsorption Cycle ..............................
`306
`Basic Cycle Analysis and Results ..........................
`313
`3
`Choice of Refrigerant . Adsorbent Pairs .....................
`4
`319
`Improving Cost Effectiveness .............................
`322
`5
`6 Summary and Conclusions ...............................
`339
`7 References ............................................
`339
`11 Applications of Carbon in Lithium-Ion Batteries ............... 341
`Tao Zheng and Jeff Dahn
`1 . Introduction ...........................................
`341
`2 . Useful Characterization Methods ...........................
`347
`3 . GraphiticCarbons ......................................
`353
`4 . Hydrogen-Containing Carbons from Pyrolyzed Organic Precursors 358
`5 . Microporous Carbons from Pyrolyzed Hard-Carbon Precursors . . . 375
`6 . Carbons Used in Commercial Applications . . . . . . . . . . . . . . . . . . . 384
`7 . References ............................................
`385
`12 Fusion Energy Applications .................................
`Lance L . Snead
`
`389
`
`1 . Introduction ...........................................
`389
`2 .
`The Advantages of Carbon as a Plasma-Facing Component . . . . . . 394
`3 . Irradiation Effects on Thennophysical Properties of Graphite and
`Carbon Fiber Composites ................................
`4 . Plasma Wall Interactions .................................
`5 . Tritium Retention in Graphite .............................
`6 . Summary and Conclusions ...............................
`7 . Acknowledgments ......................................
`8 . References ............................................
`
`400
`412
`420
`424
`424
`425
`
`

`

`ix
`
`429
`
`13 Fission Reactor Applications of Carbon .......................
`Timothy D . Burchell
`1 . The Role of Carbon Materials in Fission Reactors . . . . . . . . . . . . . 429
`2 . Graphite Moderated Power Producing Reactors ............... 438
`3 . Radiation Damage in Graphite .............................
`458
`4 . RadiolyticOxidation ....................................
`469
`. . . . . . . . . . . . . 473
`Other Applications of Carbon in Fission Reactors
`5 .
`6 . Summary and Conclusions ...............................
`477
`7 . Acknowledgments ......................................
`478
`8 . References ............................................
`478
`14 Fracture in Graphite .......................................
`Glenn R . Romanoski and Timothy D . Burchell
`1 .
`Introduction ........................................... 485
`Studies and Models of Fracture Processes in Graphite . . . . . . . . . . 486
`2 .
`Linear Elastic Fracture Mechanics Behavior of Graphite ........ 4911
`3 .
`Elastic-plastic Fracture Mechanics Behavior of Graphite ........ 497
`4 .
`Fracture Behavior of Small Flaws in Nuclear Graphites ......... 503
`5 .
`The Burchell Fracture Model ..............................
`6 .
`515
`Summary and Conclusions ...............................
`7 .
`530
`Acknowledgments ......................................
`531
`8 .
`References ............................................
`532
`9 .
`Index .......................................................
`
`485
`
`539
`
`

`

`235
`
`CHAPTER 8
`Activated Carbon for
`Automotive Applications
`
`PHILIP J. JOHNSON AND DAVID J. SETSUDA
`Ford Motor. Company
`Automotive Components Division
`Dearborn, Michigan
`
`ROGER S. WILLIAMS
`Westvaco
`Chemical Division
`Covtngton, Virginia
`
`1 Background
`
`Research datmg back to the mid 1950's has shown that volatde organic compounds
`(VOC's) photochemically react m the atmosphere and contribute to the formahon
`of ground level ozone, a precursor to smog [l]. Medical studies have shown that
`human exposure to ozone can result in eye and smus tract mitation, and can lead
`to respiratory related illnesses [2]. Due to the unique and severe smog problems
`that affected many cities in the state of Califorma, studies of the causes of air
`pollution were inibakd m the 1950's [3]. Based on its fmdmgs, Califomia formed
`the Motor Vehcle Pollution Control Board m 1960 to regulate pollution fiom
`automobiles.
`
`The generaQon of alr pollutants, including VOC's, from automotive vehicles was
`identified to come from two principal sources: vehicle exhaust emssions, and fuel
`system evaporatwe emissions [4]. Evaporative emssions are defimed as the
`automotwe fuel vapors generated and released from the vehicle's fuel system due
`to the interactions of the specific fuel in use, the fuel system characteristics, and
`environmental factors. The sources of the evaporative emissions are discussed
`below and, as presented rn the remainder of ths chapter, control of these
`evaporative emissions are the focus of the application of achvated carbon
`technology in automotwe systems.
`
`

`

`1.1 Evaporative emission sources
`
`Pnor to the implementation of any evaporahve emission controls, fuel vapors were
`freely vented from the fuel tank to the atmosphere. Diurnal, hot soak, running
`losses, resting losses, and refueling ermssions are the typical evaporatwe
`contributions from a motor vehicle. Diurnal emissions occur while a vehicle 1s
`parked and the fuel tank is heated due to dally temperature changes Hot soak
`emissions are the losses that occur due to the heat stored in the fuel tank and engine
`compartment immediately after a fully warmed up vehicle has been shut down.
`Running loss emissions are the evaporative ermssions that are generated as a result
`of fuel heating during driving conditions. Resting losses are due to hydrocarbon
`migration through materials used in fuel system components. Refueling ermssions
`occur due to the fuel vapor that is displaced from the fuel tank as liquid fuel is
`pumped m.
`
`I . 2 Development of evaporative emission controls
`
`In 1968 California committed additional resources to fight its unique air polluhon
`problems with the establishment of the Cahfomia Air Resource Board (CAW).
`Although the federal government has junsdichon over the states in the area of
`automotive emission control regulation, California has been given a waiver to
`implement its own regulations provided that they are more stringent than the federal
`requirements [ 5 ] . California has since been a leader in the development and
`nnplementation of increasingly stringent automotive ermssion control regulations.
`
`The Environmental Protection Agency (EPA) was established in 1970 by an act of
`Congress, the primary purpose of the agency being to promulgate and implement
`environmental regulations that are mandated by law Congress fiist mandated
`automotive polluhon control regulations in the Clean Air Act (CAA) Amendments
`of 1970. The CAA was amended in 1977 and 1990 to further improve an quality.
`The primary purpose of the amendments was to push industry mto developmg and
`mplementmg control technologies. The 1990 CAA Amendment also gave other
`states the option of adoptmg the California regulations.
`
`Industry has not always worked in full cooperation with government to meet the
`technology forcing standards. In the early 1970's, the U.S auto mdustry was
`characterized by slow development of the required technologies to meet the
`regulations. The slow response and seemingly insurmountable technical issues
`forced congressional and administrative delays to the original regulatory
`implementahon [l]. However, since the late 1970's, the auto industry has
`responded favorably, allocating enormous resources to meet the mcreasmgly
`strmgent regulations.
`
`

`

`237
`
`The buyers of motor vehicles have been substantially positive concerning the need
`to have cleaner running vehicles. Although the required emission control devices
`and other mandated safety equipment have increased the cost of new motor
`vehicles, sales have not been significantly effected. The current environmental
`awareness and concern are evidence of the general population's new found
`knowledge and acceptance of both mobile and stationary source emission controls.
`
`I .3 Evaporative emission control measures
`
`The earliest implementation of evaporative emission control occurred in 1963 when
`the State of California mandated that crankcase emissions be eliminated. This early
`regulation was easily met by venting crankcase emissions at a metered rate into the
`air induction system. The next areas to be regulated were the hot soak and diurnal
`losses, which California required starting in the 1970 model year. Prior to 1970,
`the uncontrolled hydrocarbon (HC) emission rate was reported to be 46.6 grams per
`vehicle for a one hour hot soak plus one hour heat build [6]. Canisters containing
`activated carbon were installed on vehicles to collect the hydrocarbons that were
`previously freely vented from the vehicles. These vapors are later purged
`(desorbed) fi-om the canister by pulling air through the carbon bed and into the air
`induction stream.
`
`The early test methodology [6] employed activated carbon traps sealed to possible
`HC sources, such as the air cleaner and fuel cap, during the test procedure. The
`carbon trap's weight was measured before and after the test procedure to establish
`the total emissions. General Motors [7] developed the Sealed Housing for
`Evaporative Determination(SHED) as a more precise and repeatable method to
`measure evaporative losses. The SHED method proved to be more accurate at
`measuring evaporative emissions that had previously escaped through openings
`other than where the carbon traps were attached. The EPA and CARB subsequently
`changed their test procedures from the carbon trap to the SHED method.
`
`The early carbon trap and SHED methods measured two components of evaporative
`emissions. Hot soak emissions were measured for a one hour period immediately
`after a vehicle had been driven on a prescribed cycle and the engine turned off.
`Diurnal emissions were also measured during a one hour event where the fuel tank
`was artificially heated. The one hour fuel temperature heat build was an accelerated
`test that was developed to represent a full day temperature heat build.
`
`The latest CARBEPA procedures require diurnal emissions to be measured during
`a real time, three day test that exposes the complete vehicle to daily temperature
`fluctuations. This test method has been employed to more accurately reflect the
`real world diumal emissions that occur. Running loss emission measurements were
`also initiated in the latest test procedures. Evaporative emissions are measured
`
`

`

`238
`
`whle the vehicle is dnven on a chassis dynamometer with heat applied to the fuel
`tank simulating a hot reflective road surface.
`
`Onboard Refueling Vapor Recovery (ORVR) regulabons were first proposed 111
`1987 but were met with a litany of technical and safety issues that delayed the
`requirement. The 1990 CAA amendments required the mplementabon of ORVR
`and the EPA regulation requires passenger cars to fist have the systems starting in
`1998. The ORVR test wll be performed in a SHED and will require that not more
`than 0.2 grams of hydrocarbon vapor per gallon of dispensed fuel be released from
`the vehicle.
`
`Fig.1 shows the typical events in the EPA's evaporative emission control test
`sequence. These test procedures cover the entire range of evaporative emissions,
`includmg the refueling emissions which are now being addressed through the
`ORVR system development. Typically, emission regulations are phased in over a
`number of years. Manufacturers are required to sell a defined percentage of their
`fleet each year that meet the requirements. Globally, the Umted States has led the
`way in terms of technology forcing evaporative emission regulabons.
`
`Fuel Draia & 40% Fill
`
`canisoerpreconditioning
`
`2 Day Diurnal Evap. Test 57 Vehicle Soak
`Refueling Test 7
`
`i
`
`13 Day Diurnal Evap. Test]
`
`Fig. 1. U. S EPA federal test procedure
`
`

`

`239
`
`The following countries also have evaporatwe emssion regulabons; Canada,,
`European Economic Community (EEC), Japan, Brazil, Mexico, Australla, South
`Korea. Regulabons in these countries have requirements that are typically less
`stnngent than the U.S. imperakves. Table 1 depicts the chronology of evaporative
`emission regulabon developments in the United States.
`
`Table 1. Chronology of U. S. evaporative emission development [l]
`Model
`Mandated
`Test
`Cerhficabon
`Year
`Sales Area
`Method
`Standard
`1970
`California
`Carbon Trap
`6 grams HC
`1971
`49 States
`6 grams HC
`Carbon Trap
`1972
`50 States
`2 grams HC
`Carbon Trap
`6 grams HC
`1978
`50 States
`SHED
`1980
`California
`SHED
`2 grams HC
`2 grams HC
`50 States
`SHED [8]
`1981
`2 grams HC
`1995
`California
`VT SHED [9]
`Run Loss
`I995
`Callfornia
`0.05 g/mile
`1996
`50 States
`VT SHED
`2 grams HC
`50 States
`1996
`0.05 g/mtle
`Run Loss
`1998
`50 States
`0 2 g/gal
`ORVR [ 101
`50 States
`0.2 glgal
`ORVR
`200 1
`
`Note
`One hour test
`One hour test
`One hour test
`One hour test
`One hour test
`One hour test
`Three day test
`
`Three day test
`
`Passenger cars
`Lt Duty Trucks
`
`2 Activated Carbon
`
`Activated carbon is an amorphous solid with a large internal surface aredpore
`structure that adsorbs molecules from both the liquid and gas phase [ 1 11. It has
`been manufactured from a number of raw matenials mcluding wood, coconut shell,
`and coal [ 1 1,121. Specific processes have been developed to produce actwated
`carbon in powdered, granular, and specially shaped (pellet) forms. The key to
`development of activated carbon products has been the selection of the
`manufacturing process, raw material, and an understandmg of the basic adsorption
`process to tailor the product to a specific adsorpbon applicabon.
`
`2 1 Production methods
`
`Based upon raw matenal and intended applicabon, the manufactunng of acbvated
`carbon falls into two mam categories: thermal acbvabon and chemcal acbvation.
`In general, thermal activabon involves the heatinglgasificabon of carbon at high
`temperatures [13], while chemical activation is characterrzed by the chemcal
`dehydration of the raw material at significantly lower temperatures [11,14].
`
`2.1,l Thermal acbvabon processes
`Thermal activation is characterrzed by
`
`two processing stages: thermal
`
`

`

`240
`
`decomposition or carbonization of the precursor, and gasification or activation of
`the carbonized char material. In the carbonization step, hydrogen and oxygen are
`removed from the precursor (raw material) to generate a basic carbon pore
`structure. During activation, an oxidizing atmosphere such as steam is used to
`increase the pore volume and particle surface area through elimination of volatile
`prohcts and carbon burn-off [14]. Thermal activation precursors include coal and
`coconut shells. Thermal activation is usually carried out in directly fiied rotary
`kilns or multi-hearth furnaces, with temperatures of greater than 1000 "C achieved
`in process. A thermal activation process for the production of activated carbon
`from coal is shown in Fig. 2 [ 111.
`
`To
`
`Bi
`
`Fig. 2. Thermal activation process for production of activated carbon. Reprinted from [l 11,
`copyright 0 1992 John Willey & Sons, Inc., with permission.
`
`2.1.2 Chemical activation processes
`In chemical activation processes, the precursor is fiist treated with a chemical
`activation agent, often phosphoric acid, and then heated to a temperature of 450 -
`700 "C in an activation kiln. The char is then washed with water to remove the
`acid from the carbon. The filtrate is passed to a chemical recovery unit for
`recycling. The carbon is dried, and the product is often screened to obtain a
`specific particle size range. A diagram of a process for the chemical activation of
`a wood precursor is shown in Fig. 3.
`
`2.2 Applications/characteristics of activated carbon
`
`The activated carbon materials are produced by either thermal or chemical
`activation as granular, powdered, or shaped products. In addition to the form of
`the activated carbon, the fiial product can differ in both particle size and pore
`structure. The properties of the activated carbon will determine the type of
`application for which the carbon will be used.
`
`2.2.1 Liquid phase applications
`Liquid phase applications account for nearly 80% of the total use of activated
`carbon. Activated carbon used in liquid phase applications typically have a high
`fraction of pores in the macropore (>50nm) range. This is to permit the liquid
`phase molecules to diffuse more rapidly into the rest of the pore structure [ 151.
`
`

`

`241
`
`ch-sim
`Granuies
`10 x 25 Mesh4
`as Example
`
`Off-size Granules
`
`, Powdered
`Carbon
`
`Fig. 3. Chemical activation process for production of activated carbon
`
`The principal liquid phase applications, the type of carbon used, and 1987
`consumption levels are presented in Table 2.
`
`Table 2. Liquid phase activated carbon consumption [11,16]. Reprinted from [l I],
`copyright Q 1992 John Willey & Sons, Inc., with permission.
`U.S. 1987 consumption, metric ton (1000's)
`GranularlShaped
`4.5
`6.4
`0.9
`6.8
`4.1
`0.9
`2.0
`1.6
`0.9
`1.4
`0.7
`- 0.2
`30.4
`
`Potable water
`Wastewater, industrial
`Wastewater, municipal
`Sweetener decolorization
`Chemical processing and misc.
`Food, beverage, and oils
`Pharmaceuticals
`Mining
`Groundwater
`Household uses
`Dry cleaning
`Electroplating
`Total
`
`Powdered
`13.6
`6.6
`2.0
`9.1
`2.3
`3.9
`.3
`2.5
`2.3
`0.9
`0.4
`0.4
`46.3
`
`Total
`18.1
`13.0
`2.9
`15.9
`6.4
`4.8
`4.3
`4.1
`3.2
`2.3
`1.1
`- 0.6
`76.7
`
`2.2.2 Gas phase applications
`Gas phase applications of activated carbon fall into the main categories of
`separation, gas storage, and catalysis. These applications account for about 20%
`of the total use of activated carbon, with the majority using either granular or pellet
`type. Table 3 shows the major gas phase applications, again along with 1987
`consumption levels.
`
`

`

`242
`
`Table 3. Gas phase activated carbon consumption. Reprinted from [ 1 11, copyright 0 1992
`John Willey & Sons, Inc., with permission.
`U.S. 1987 consumption, metric ton (1000's)
`Solvent Recovery
`Automotive/Gasoline Recovery
`Industrial off-gas Control
`Catalysis
`Pressure Swing Separation
`Air Conditioning
`Gas Mask
`Cigarette Filters
`Nuclear Industry
`Total
`
`4.5
`4.1
`3.2
`2.7
`1.1
`0.5
`0.5
`0.5
`- 0.3
`17.4
`
`2.2.3 Physical properties
`Properties for typical activated carbons used in both liquid and gas phase
`applications are shown in Table 4.
`
`2.3 Automotive applications
`
`The major automotive application for activated carbon is the capture of gasoline
`vapors from vehicle fuel vapor systems. With the creation of emission control
`standards in the early 1970's, vehicles began to be equipped with evaporative
`emission control systems [17,18]. The activated carbons to be used in these
`emission control systems were required to adsorb gasoline vapors at high efficiency
`and to release them during the purge regeneration cycle. The durability of the
`activated carbon became an important characteristic, as the adsorptiodpurge
`regeneration cycle would be repeated many times over the life of a vehicle [12].
`The operation of the evaporative emission control system is detailed in Section 3.
`
`Initial evaporative emission control systems utilized coal-base granular carbons,
`which were
`followed by chemically activated, wood-base carbons [ 191.
`Increasingly stringent emission control standards [20-221 led to further activated
`carbon development, including the production of a pellet shaped product
`specifically designed for automotive applications [ 191. The most recent emission
`control requirements have addressed capturing vapors emitted during refueling
`[23,24], which will require a better understanding of the performance of activated
`carbon in hydrocarbon adsorption over a larger range of operation.
`
`Properties of activated carbons produced by Westvaco for automotive applications
`are presented in Table 5.
`
`

`

`Table 4. Properties of selected activated carbon products. Reprinted from [l 11, copyright 0 1992 John Willey & Sons, Inc., with permission.
`Liquid-Phase Carbons
`
`Gas-Phase Carbons
`
`Typical Range
`
`Manufacturer
`Precursor
`Product Grade
`Product Form
`Product Property
`Particle Size (US. mesh)
`Apparent Density (g/cm’)
`
`<4
`0.2-0.6
`0.4-0.9
`Particle Density (g/cm’)
`50-100
`Hardness or Abrasion Number
`1-20
`Ash (wt. %)
`500-2500
`BET Surface Area (N2, m2/g)
`0.5-2.5
`Total Pore Volume (cm’/g)
`35-125
`CC14 Activity (wt. %)
`Butane Working Capacity (g/100cm3) 4-14
`500-1200
`Iodine Number
`15-25
`Decolorizing Index (Westvaco)
`50-250
`Molasses Number
`(Calgon)
`
`Calgon
`Coal
`BPL
`Granular
`
`12x30
`>0.48
`
`0.8
`>90
`18
`1050-1 150
`0.8
`>60
`
`21050
`
`Norit
`Peat
`B4
`Extruded
`
`Westvaco
`Wood
`WV-A 1100
`Granular
`
`3.8 mm dia.
`0.43
`
`99
`6
`1100-1200
`0.9
`
`1 OX25
`0.27
`0.5
`
`1750
`1.2
`
`>11
`
`(Norit)
`Heat Capacity (lOO°C, cal/g/K)
`Thermal Conductivity (W/m/K)
`
`300-1500
`0.2-0.3
`0.05-0.1
`
`0.25
`
`Calgon
`Coal
`SGL
`Granular
`
`8x30
`0.52
`0.8
`>75
`d o
`900-1000
`0.85
`
`>900
`
`>200
`
`0.25
`
`Norit
`Peat
`SA 3
`Powdered
`
`Westvaco
`Wood
`SA-20
`Powdered
`
`64% <325
`0.46
`
`65-85% <325
`0.34-0.37
`
`3-5
`1400-1 800
`2.2-2.5
`
`>loo0
`>20
`
`6
`750
`
`800
`
`440
`
`h, P w
`
`

`

`244
`
`Table 5. Properties of Westvaco automotive grade activated carbons [19]
`WV-A 900 BAX 950 WV-A 1100 BAX 1100 BAX 1500
`Grade
`Granular Pelleted
`Granular
`Pelleted
`Pelleted
`Shape
`
`Mesh Size
`
`10x25
`
`2mm
`
`10x25
`
`2mm
`
`2mm
`
`BET Surface Area (m*/g) 1400-1600 1300-1500 1600-1900
`
`1400-1600 1800-2000
`
`Butane Working
`Capacity (g/lOOml)
`
`9.0min
`
`9.5min
`
`11.Omin
`
`11.0min
`
`15.0min
`
`Apparent Density (g/cm3) 0.2-0.32
`
`0.3-0.4
`
`0.2-0.32
`
`0.3-0.4
`
`0.27-0.35
`
`Moisture, as Packed (%)
`
`10 max
`
`5 max
`
`10 max
`
`5 max
`
`5 max
`
`Particle Size (U.S.Sieve Series)
`8max
`Oversize (“h)
`Smax
`Undersize (“h)
`
`2max
`Smax
`
`8 max
`5 rnax
`
`2max
`5max
`
`2 max
`5 max
`
`3 Vehicle Fuel Vapor System
`
`A current vehicle fuel system designed for evaporative emission control should
`address enhanced SHED, running loss, and ORVR emission level requirements (see
`Table 1). A typical vehicle fuel system is shown in Fig. 4. The primary fimctions
`of the system are to store the liquid and vapor phases of the fuel with acceptable
`loss levels, and to pump liquid fuel to the engine for vehicle operation. The
`operation of the various components in the fuel system, and how they work to
`minimize