ASTM D6558-00A(2015)e1
(Test Method)Standard Test Method for Determination of TGA CO2 Reactivity of Baked Carbon Anodes and Cathode Blocks
Standard Test Method for Determination of TGA CO<inf>2</inf> Reactivity of Baked Carbon Anodes and Cathode Blocks
SIGNIFICANCE AND USE
5.1 The CO2 reactivity rates are used to quantify the tendency of a carbon artifact to react with carbon dioxide. Carbon consumed by these unwanted side reactions is unavailable for the primary reactions of reducing alumina to the primary metal. CO2 dusting rates are used to quantify the tendency of the coke aggregate or binder coke of a carbon artifact to selectively react with these gases. Preferential attack of the binder coke or coke aggregate of a carbon artifact by these gases causes some carbon to fall off or dust, making the carbon unavailable for the primary reaction of reducing alumina and, more importantly, reducing the efficiency of the aluminum reduction cell.
5.2 Comparison of CO2 reactivity and dusting rates is useful in selecting raw materials for the manufacture of commercial anodes for specific smelting technologies in the aluminum reduction industry.
5.3 CO2 reactivity rates are used for evaluating effectiveness and beneficiation processes or for research purposes.
SCOPE
1.1 This test method covers the thermogravimetric (TGA) determination of CO2 reactivity and dusting of shaped carbon anodes and cathode blocks used in the aluminum reduction industry. The apparatus selection covers a significant variety of types with various thermal conditions, sample size capability, materials of construction, and procedures for determining the mass loss and subsequent rate of reaction. This test method standardizes the variables of sample dimensions, reaction temperature, gas velocity over the exposed surfaces, and reaction time such that results obtained on different apparatuses are correlatable.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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´1
Designation: D6558 − 00a (Reapproved 2015)
Standard Test Method for
Determination of TGA CO Reactivity of Baked Carbon
Anodes and Cathode Blocks
This standard is issued under the fixed designation D6558; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—SI unit formatting was corrected editorially in December 2015.
1. Scope 3. Terminology
3.1 Definitions of Terms Specific to This Standard:
1.1 This test method covers the thermogravimetric (TGA)
3.1.1 dusting, n—that quantity of carbon that falls off the
determination of CO reactivity and dusting of shaped carbon
carbonartifactwhileinthereactionchamberandiscollectedin
anodes and cathode blocks used in the aluminum reduction
the container at the bottom of the reaction chamber.
industry.Theapparatusselectioncoversasignificantvarietyof
types with various thermal conditions, sample size capability,
3.1.2 final CO reactivity, n—the mass loss of the carbon
materials of construction, and procedures for determining the
artifact during the final 30min of exposure to CO in the
mass loss and subsequent rate of reaction. This test method
reaction chamber divided by the initial geometric (right cylin-
standardizes the variables of sample dimensions, reaction
drical) exposed surface area of the sample, expressed as
temperature, gas velocity over the exposed surfaces, and
milligrams per centimetre squared per hour.
reactiontimesuchthatresultsobtainedondifferentapparatuses
3.1.3 initial CO reactivity, n—the mass loss of the carbon
are correlatable.
artifact during the first 30min of exposure to CO in the
1.2 The values stated in SI units are to be regarded as reaction chamber divided by the initial geometric (right cylin-
drical) exposed surface area of the sample, expressed as
standard. No other units of measurement are included in this
standard. milligrams per centimetre squared per hour.
3.1.4 total CO reactivity, n—the total mass loss of the
1.3 This standard does not purport to address all of the 2
carbonartifact(includingdusting)duringthetotaltimethatthe
safety concerns, if any, associated with its use. It is the
sample is exposed to CO (420min) in the reaction chamber
responsibility of the user of this standard to establish appro- 2
divided by the initial geometric (right cylindrical) exposed
priate safety and health practices and determine the applica-
surface area of the sample, expressed as milligrams per
bility of regulatory limitations prior to use.
centimetre squared per hour.
2. Referenced Documents
4. Summary of Test Method
2.1 ASTM Standards:
4.1 Initial, final, and total CO reactivity and dusting are
D6353Guide for Sampling Plan and Core Sampling for
determined by passing carbon dioxide gas at flow rates giving
Prebaked Anodes Used in Aluminum Production
a standard velocity of reactant gas around cylindrically shaped
D6354Guide for Sampling Plan and Core Sampling of
carbon artifacts under isothermal conditions for a specified
Carbon Cathode Blocks Used in Aluminum Production
length of time. The reactivity is determined by continuously
E691Practice for Conducting an Interlaboratory Study to
monitoring the sample mass loss. The dusting term is deter-
Determine the Precision of a Test Method
mined by collecting and determining the mass of carbon
particles that fall off the sample during reaction.
5. Significance and Use
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricantsand is the direct responsibility of
5.1 The CO reactivity rates are used to quantify the
SubcommitteeD02.05onPropertiesofFuels,PetroleumCokeandCarbonMaterial.
tendency of a carbon artifact to react with carbon dioxide.
Current edition approved Oct. 1, 2015. Published December 2015. Originally
Carbon consumed by these unwanted side reactions is unavail-
approved in 2000. Last previous edition approved in 2010 as D6558–00a (2010).
DOI: 10.1520/D6558-00AR15E01.
able for the primary reactions of reducing alumina to the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
primary metal. CO dusting rates are used to quantify the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
tendency of the coke aggregate or binder coke of a carbon
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. artifact to selectively react with these gases. Preferential attack
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D6558 − 00a (2015)
of the binder coke or coke aggregate of a carbon artifact by near the surface of the test sample to allow the furnace
these gases causes some carbon to fall off or dust, making the controller to adjust to exothermic reactions, which occur
carbon unavailable for the primary reaction of reducing alu-
during air reactivity tests, if the furnace is also used for air
mina and, more importantly, reducing the efficiency of the reactivitytesting.Thecontrolthermocoupleshallbepositioned
aluminum reduction cell.
4mm 6 1mm from the side sample surface and centered
verticallywithin5mmofthecenter.Thefurnaceshallbelarge
5.2 ComparisonofCO reactivityanddustingratesisuseful
enough to accept the reaction chamber.
in selecting raw materials for the manufacture of commercial
6.1.1.1 Reaction Chamber, consisting of a vertical tube
anodes for specific smelting technologies in the aluminum
reduction industry. constructed of a material capable of withstanding the tempera-
ture of the reaction (960°C 6 2°C) with sufficient inside
5.3 CO reactivity rates are used for evaluating effective-
diameter(ID)toacceptthesampleandsampleholderwhilenot
ness and beneficiation processes or for research purposes.
affecting the gas flow to and from the sample (100mm 6
25mm ID is recommended). The reaction chamber is to be
6. Apparatus
constructed with a dust collection cup at the bottom that is
6.1 Theapparatustobeusedshouldbeassimpleaspossible
removableandcapableofcapturingallthedustthatfallsoffthe
andbecommensuratewithwhatistobeachieved,theprincipal
sample during the test. The most common materials of con-
criteria being that the reaction rate is to be determined under
struction are quartz and Inconel.
isothermal conditions and unaffected by physical and chemical
6.1.1.2 Sample Holders,capableofsupportingthesamplein
properties inherent to the apparatus (such as gas diffusion
the reaction chamber for the duration of the test and should be
patterns, gas temperature, exposed sample surface area, and so
capable of being reusable. The sample holder shall not change
forth).Atypical apparatus that has been found to be suitable is
in mass during the test, affect the diffusion pattern of the gases
illustrated in Fig. 1.
to or from the sample, limit the gas accessible surface area of
6.1.1 Furnace and Controller, capable of maintaining con-
the test sample, or interfere with the free fall of dust from the
stanttemperature,within 62°Cinthe100mmregioncentered
sample. A typical sample holder is illustrated in Fig. 2.
on the specimen. The example apparatus of Fig. 1 employs a
6.1.1.3 Gas Preheat Tube, extending into the first heat zone
three zone heating element and associated controls to accom-
plish this, but other methods such as tapered windings or long of the reaction chamber to preheat the gases prior to entering
linear heaters are also suitable. The control thermocouple is a the reaction chamber. The length and diameter of the tube can
groundedtypeandshallbelocatedwithinthereactionchamber vary as long as the gases exiting the tube are the same
FIG. 1 Typical CO Reactivity Apparatus
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D6558 − 00a (2015)
7. Reagents
7.1 Purity of Reagents—Reagent grade, conforming to the
specifications of the Committee onAnalytical Reagents of the
American Chemical Society.
7.1.1 Nitrogen—99.95%.
7.1.2 Carbon Dioxide—99.95%.
8. Sampling
8.1 Shape the carbon specimen by coring and cutting or
machining to a right cylindrical geometry, with a length of
50mm 6 1.0mm and diameter of 50mm 6 1.0mm. Most
sample holders require a hole of about 3mm diameter to be
drilled vertically through the center of the cylinder to accom-
modateahanger.Theshapedspecimenistobesmoothandfree
of visible cracks and gouges. Sampling plans for anodes and
cathodeblocksgiveninGuidesD6353andD6354maybeused
if desired.
8.2 Dry the shaped specimen in an oven at 105°C 65°C
to constant weight.
8.3 Make the sample free of loose carbon dust and impuri-
ties from the shaping process by blowing with dry air.
9. Calibration
FIG. 2 Typical Sample Holder
9.1 The purpose of this procedure is to establish a relation-
shipbetweenthecontrollersettingsforthreezonefurnacesand
the actual temperatures inside the reaction chamber in the
region of the specimen.The length of the zone to be calibrated
temperatureasthereactionchamber.Theinletgasshallexitthe
is 100mm (4in.).
preheat tube downward to prevent channeling of the gas
through the reaction chamber and to prevent plugging of the NOTE1—Forsinglezonefurnaces,thecalibrationprobeshallbeplaced
in center of where sample will be placed and confirm that the zone of
preheat tube with carbon dust.
100mm is within 62°C.
6.1.1.4 Balance, capable of measuring the mass of the
9.1.1 Insert a multiprobe thermocouple (for example, three
sample and sample holder (a maximum of approximately
couples in same sheath with probes located at the tip, and
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: D6558 − 00a (Reapproved 2010) D6558 − 00a (Reapproved 2015)
Standard Test Method for
Determination of TGA CO Reactivity of Baked Carbon
Anodes and Cathode Blocks
This standard is issued under the fixed designation D6558; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—SI unit formatting was corrected editorially in December 2015.
1. Scope
1.1 This test method covers the thermogravimetric (TGA) determination of CO reactivity and dusting of shaped carbon anodes
and cathode blocks used in the aluminum reduction industry. The apparatus selection covers a significant variety of types with
various thermal conditions, sample size capability, materials of construction, and procedures for determining the mass loss and
subsequent rate of reaction. This test method standardizes the variables of sample dimensions, reaction temperature, gas velocity
over the exposed surfaces, and reaction time such that results obtained on different apparatuses are correlatable.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D6353 Guide for Sampling Plan and Core Sampling for Prebaked Anodes Used in Aluminum Production
D6354 Guide for Sampling Plan and Core Sampling of Carbon Cathode Blocks Used in Aluminum Production
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 dusting, n—that quantity of carbon that falls off the carbon artifact while in the reaction chamber and is collected in the
container at the bottom of the reaction chamber.
3.1.2 final CO reactivity,n—the mass loss of the carbon artifact during the final 30 min 30 min of exposure to CO in the
2 2
reaction chamber divided by the initial geometric (right cylindrical) exposed surface area of the sample, expressed as
mg/cmmilligrams -h. per centimetre squared per hour.
3.1.3 initial CO reactivity,n—the mass loss of the carbon artifact during the first 30 min 30 min of exposure to CO in the
2 2
reaction chamber divided by the initial geometric (right cylindrical) exposed surface area of the sample, expressed as
mg/cmmilligrams -h. per centimetre squared per hour.
3.1.4 total CO reactivity,n—the total mass loss of the carbon artifact (including dusting) during the total time that the sample
is exposed to CO (420 min) (420 min) in the reaction chamber divided by the initial geometric (right cylindrical) exposed surface
area of the sample, expressed as mg/cmmilligrams -h. per centimetre squared per hour.
4. Summary of Test Method
4.1 Initial, final, and total CO reactivity and dusting are determined by passing carbon dioxide gas at flow rates giving a
standard velocity of reactant gas around cylindrically shaped carbon artifacts under isothermal conditions for a specified length of
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricantsand is the direct responsibility of Subcommittee
D02.05 on Properties of Fuels, Petroleum Coke and Carbon Material.
Current edition approved May 1, 2010Oct. 1, 2015. Published June 2010December 2015. Originally approved in 2000. Last previous edition approved in 20052010 as
D6558D6558 – 00a (2010).–00a (2005). DOI: 10.1520/D6558-00AR10.10.1520/D6558-00AR15E01.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D6558 − 00a (2015)
time. The reactivity is determined by continuously monitoring the sample mass loss. The dusting term is determined by collecting
and determining the mass of carbon particles that fall off the sample during reaction.
5. Significance and Use
5.1 The CO reactivity rates are used to quantify the tendency of a carbon artifact to react with carbon dioxide. Carbon
consumed by these unwanted side reactions is unavailable for the primary reactions of reducing alumina to the primary metal. CO
dusting rates are used to quantify the tendency of the coke aggregate or binder coke of a carbon artifact to selectively react with
these gases. Preferential attack of the binder coke or coke aggregate of a carbon artifact by these gases causes some carbon to fall
off or dust, making the carbon unavailable for the primary reaction of reducing alumina and, more importantly, reducing the
efficiency of the aluminum reduction cell.
5.2 Comparison of CO reactivity and dusting rates is useful in selecting raw materials for the manufacture of commercial
anodes for specific smelting technologies in the aluminum reduction industry.
5.3 CO reactivity rates are used for evaluating effectiveness and beneficiation processes or for research purposes.
6. Apparatus
6.1 The apparatus to be used should be as simple as possible and be commensurate with what is to be achieved, the principal
criteria being that the reaction rate is to be determined under isothermal conditions and unaffected by physical and chemical
properties inherent to the apparatus (such as gas diffusion patterns, gas temperature, exposed sample surface area, and so forth).
A typical apparatus that has been found to be suitable is illustrated in Fig. 1.
6.1.1 Furnace and Controller, capable of maintaining constant temperature, within 62°C62 °C in the 100-mm100 mm region
centered on the specimen. The example apparatus of Fig. 1 employs a three zone heating element and associated controls to
accomplish this, but other methods such as tapered windings or long linear heaters are also suitable. The control thermocouple is
a grounded type and shall be located within the reaction chamber near the surface of the test sample to allow the furnace controller
to adjust to exothermic reactions, which occur during air reactivity tests, if the furnace is also used for air reactivity testing. The
control thermocouple shall be positioned 44 mm 6 1 mm 1 mm from the side sample surface and centered vertically within 5 mm
5 mm of the center. The furnace shall be large enough to accept the reaction chamber.
6.1.1.1 Reaction Chamber, consisting of a vertical tube constructed of a material capable of withstanding the temperature of the
reaction (960(960 °C 6 2°C)2 °C) with sufficient inside diameter (ID) to accept the sample and sample holder while not affecting
FIG. 1 Typical CO Reactivity Apparatus
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D6558 − 00a (2015)
the gas flow to and from the sample (100(100 mm 6 25-mm25 mm ID is recommended). The reaction chamber is to be constructed
with a dust collection cup at the bottom that is removable and capable of capturing all the dust that falls off the sample during the
test. The most common materials of construction are quartz and Inconel.
6.1.1.2 Sample Holders, capable of supporting the sample in the reaction chamber for the duration of the test and should be
capable of being reusable. The sample holder shall not change in mass during the test, affect the diffusion pattern of the gases to
or from the sample, limit the gas accessible surface area of the test sample, or interfere with the free fall of dust from the sample.
A typical sample holder is illustrated in Fig. 2.
6.1.1.3 Gas Preheat Tube, extending into the first heat zone of the reaction chamber to preheat the gases prior to entering the
reaction chamber. The length and diameter of the tube can vary as long as the gases exiting the tube are the same temperature as
the reaction chamber. The inlet gas shall exit the preheat tube downward to prevent channeling of the gas through the reaction
chamber and to prevent plugging of the preheat tube with carbon dust.
6.1.1.4 Balance, capable of measuring the weightmass of the sample and sample holder (approximately 200 g maximum) (a
maximum of approximately 200 g) continuously throughout the duration of the test to the nearest 0.01 g.0.01 g.
6.1.1.5 Gas Flow Meter, capable of monitoring the gas flow rate into the reaction chamber. All gas flow rates are to be
maintained at the rate determined for the particular test apparatus.
6.1.1.6 Needle Valve, to make fine adjustments to the gas flow rate.
6.1.1.7 Pressure Reducing Valve, to reduce the pressure of the compressed gases to near atmospheric pressure prior to entering
the gas flow meter through the needle valve.
6.1.1.8 Thermocouple(s), inserted into the reaction chamber to calibrate the furnace zone controllers. An optional thermocouple
may be used to monitor reaction temperatures. Some users find continuous temperature measurement of the internal reaction
chamber to be of value.
6.1.1.9 Calipers, or other suitable device, capable of measuring to within 0.01 mm 0.01 mm for determining the sample
diameter and height to calculate geometric surface area exposed to the test gases.
6.1.1.10 Optional Equipment, including, but not limited to, automatic control devices, multichannel line selector, and personal
computer to automate data gathering, manipulation, reporting, and storage.
7. Reagents
7.1 Purity of Reagents—Reagent grade, conforming to the specifications of the Committee on Analytical Reagents of the
American Chemical Society.
7.1.1 Nitrogen—99.95 %.
7.1.2 Carbon Dioxide—99.95 %.
FIG. 2 Typical Sample Holder
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D6558 − 00a (2015)
8. Sampling
8.1 Shape the carbon specimen by co
...
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