ASTM D6791-22

Standard Test Method for Determination of Grain Stability of Calcined Petroleum Coke

SIGNIFICANCE AND USE
5.1 The grain stability of calcined petroleum coke determines the resistance to breakdown of + 4 mm particles used in the manufacture of carbon anodes for use in the reduction process of aluminum.  
5.2 Calcined petroleum cokes have to be relatively easy to grind for fines production but strong enough to withstand forming pressures and thermal stresses occurring when the anodes are used in the reduction process.
SCOPE
1.1 This test method covers a laboratory vibration mill method for the determination of the grain stability of calcined petroleum coke for the manufacture of carbon products used in the smelting of aluminum. Calcined petroleum coke with poor mechanical strength may become degraded during mixing. Poor grain stability will affect the grain size and may result in poor quality of baked blocks.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Apr-2022
• ICS: 75.080 - Petroleum products in general
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.05 - Properties of Fuels, Petroleum Coke and Carbon Material

Relations

• Refers: ASTM D2234/D2234M-19 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 01-Dec-2019
• Refers: ASTM D6970-03(2019) - Standard Practice for Collection of Calcined Petroleum Coke Samples for Analysis
• Effective Date: 01-Dec-2019
• Refers: ASTM D2234/D2234M-17 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 15-Oct-2017
• Refers: ASTM D6969-16 - Standard Practice for Preparation of Calcined Petroleum Coke Samples for Analysis
• Effective Date: 01-Jun-2016
• Refers: ASTM D2234/D2234M-16 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 01-Mar-2016
• Refers: ASTM D6969-15 - Standard Practice for Preparation of Calcined Petroleum Coke Samples for Analysis
• Effective Date: 01-Jun-2015
• Refers: ASTM E11-13 - Standard Specification for Woven Wire Test Sieve Cloth and Test Sieves
• Effective Date: 01-Oct-2013
• Refers: ASTM D346-04(2010) - Standard Practice for Collection and Preparation of Coke Samples for Laboratory Analysis
• Effective Date: 01-May-2010
• Refers: ASTM D2234/D2234M-10 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 01-Jan-2010
• Refers: ASTM D2234/D2234M-09a - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 01-Oct-2009
• Refers: ASTM E11-09e1 - Standard Specification for Woven Wire Test Sieve Cloth and Test Sieves
• Effective Date: 01-May-2009
• Refers: ASTM D6970-03(2013)e1 - Standard Practice for Collection of Calcined Petroleum Coke Samples for Analysis
• Effective Date: 15-Oct-2008
• Refers: ASTM D6969-03(2008) - Standard Practice for Preparation of Calcined Petroleum Coke Samples for Analysis
• Effective Date: 15-Oct-2008
• Refers: ASTM D6970-03(2008) - Standard Practice for Collection of Calcined Petroleum Coke Samples for Analysis
• Effective Date: 15-Oct-2008
• Refers: ASTM D2013-07 - Standard Practice for Preparing Coal Samples for Analysis
• Effective Date: 01-Jun-2007

Overview

ASTM D6791-22 is the Standard Test Method for Determination of Grain Stability of Calcined Petroleum Coke. Developed by ASTM International, this standard specifies a laboratory procedure using a vibration mill to evaluate the mechanical stability of calcined petroleum coke grains. The primary purpose of the test is to ensure that calcined petroleum coke used in carbon anode manufacturing for aluminum smelting maintains optimal grain size and resists breakdown during handling, forming, and the electrolytic reduction process.

Grain stability is a key quality parameter. It impacts the performance and integrity of carbon anodes, which are critical in primary aluminum production. Poor grain stability can cause the coke to break down, affecting the physical properties of anodes and, consequently, the efficiency and quality of the aluminum reduction process.

Key Topics

• Test Method and Scope

  • Laboratory vibration mill method is used to measure grain stability.
  • Focuses on coke fractions between 4 mm and 8 mm in size.
  • Only SI units are used as standard for all measurements.

• Significance of Grain Stability

  • Ensures sufficient mechanical strength of calcined petroleum coke.
  • Protects +4 mm particles from degradation during anode formation and use in aluminum electrolysis.
  • Balances the need for ease of grinding with resistance to forming pressures and high temperatures.

• Sample Preparation and Analysis

  • Coke samples are sieved and appropriately weighed before testing.
  • Duplicate tests are performed for accuracy and repeatability.
  • Results are reported as a percentage of the original grain retained after vibration milling.

• Precision and Reproducibility

  • Repeatability difference should not exceed 2% for individual results.
  • Reproducibility between labs should not differ by more than 3%.

• Safety and Compliance

  • Users must establish safety, health, and environmental protocols.
  • Aligns with internationally recognized guidelines for standardization.

Applications

ASTM D6791-22 is widely applied in industries that rely on calcined petroleum coke, particularly:

• Aluminum Smelting: Ensures the anode material maintains appropriate grain stability, directly impacting the quality of baked blocks and the efficiency of the reduction process.
• Quality Control: Used by material testing laboratories and coke manufacturers to certify batches of calcined petroleum coke before supply or use.
• Product Development: Guides improvements in calcined coke processing to optimize physical properties required by demanding applications.

Accurate assessment of grain stability helps prevent breakdown of large coke particles, minimizing fines production and ensuring consistent anode performance under high-pressure and high-temperature conditions found in aluminum electrolysis cells.

Related Standards

For best results and full compliance, ASTM D6791-22 should be used in conjunction with related ASTM and ISO standards:

• ASTM D346: Practice for Collection and Preparation of Coke Samples for Laboratory Analysis
• ASTM D2013: Practice for Preparing Coal Samples for Analysis
• ASTM D2234/D2234M: Practice for Collection of Gross Sample of Coal
• ASTM D6969: Practice for Preparation of Calcined Petroleum Coke Samples for Analysis
• ASTM D6970: Practice for Collection of Calcined Petroleum Coke Samples for Analysis
• ASTM E11: Specification for Woven Wire Test Sieve Cloth and Test Sieves
• ISO 6375: Carbonaceous Materials for the Production of Aluminum-Coke for Electrodes-Sampling

These documents provide supplementary procedures for sample collection, preparation, and analytical methods essential for accurate and reliable results according to ASTM D6791-22. Using these standards together supports best practices in testing, compliance, and the overall quality of calcined petroleum coke in industrial applications.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6791 − 22
Standard Test Method for
Determination of Grain Stability of Calcined Petroleum
Coke
This standard is issued under the fixed designation D6791; 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.
1. Scope* D6970Practice for Collection of Calcined Petroleum Coke
Samples for Analysis
1.1 This test method covers a laboratory vibration mill
E11Specification forWovenWireTest Sieve Cloth andTest
method for the determination of the grain stability of calcined
Sieves
petroleumcokeforthemanufactureofcarbonproductsusedin
the smelting of aluminum. Calcined petroleum coke with poor 2.2 ISO Standard:
mechanical strength may become degraded during mixing. ISO 6375Carbonaceous Materials for the Production of
Poor grain stability will affect the grain size and may result in Aluminum—Coke for Electrodes—Sampling
poor quality of baked blocks.
3. Terminology
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
3.1 Definitions:
standard.
3.1.1 calcined petroleum coke, n—petroleum coke that has
been thermally treated to drive off the volatile matter and to
1.3 This standard does not purport to address all of the
develop crystalline structure.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3.1.2 petroleum coke, n—solid, carbonaceous residue pro-
priate safety, health, and environmental practices and deter-
duced by thermal decomposition of heavy petroleum fractions,
mine the applicability of regulatory limitations prior to use.
or cracked stocks, or both.
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard-
4. Summary of Test Method
ization established in the Decision on Principles for the
4.1 A representative sample of calcined petroleum coke is
Development of International Standards, Guides and Recom-
dried and screened to a 4mm to 8mm fraction. The resultant
mendations issued by the World Trade Organization Technical
sample is weighed so that two separate portions of 100.0g 6
Barriers to Trade (TBT) Committee.
0.5g mass are obtained. The samples are place into the
2. Referenced Documents laboratorymillandgroundforaspecifiedperiodoftime.After
2 grinding the sample is screened and the mass of the + 4mm
2.1 ASTM Standards:
material is determined. The grain stability is the percent of the
D346Practice for Collection and Preparation of Coke
original material remaining on the + 4mm sieve.
Samples for Laboratory Analysis
D2013Practice for Preparing Coal Samples for Analysis
5. Significance and Use
D2234/D2234MPractice for Collection of a Gross Sample
of Coal
5.1 The grain stability of calcined petroleum coke deter-
D6969Practice for Preparation of Calcined Petroleum Coke
mines the resistance to breakdown of + 4mm particles used in
Samples for Analysis
the manufacture of carbon anodes for use in the reduction
process of aluminum.
5.2 Calcined petroleum cokes have to be relatively easy to
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
grind for fines production but strong enough to withstand
SubcommitteeD02.05onPropertiesofFuels,PetroleumCokeandCarbonMaterial.
forming pressures and thermal stresses occurring when the
Current edition approved May 1, 2022. Published May 2022. Originally
ɛ1 anodes are used in the reduction process.
approved in 2002. Last previous edition approved in 2017 as D6791–11 (2017) .
DOI: 10.1520/D6791-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6791 − 22
1 = mill
2 = common base plate
4 = flat springs
5 = adjustable straps
7,8 = grinding vessels
9 = motor
13 = quick release catch
NOTE 1—All dimensions are in millimetres.
FIG. 1 Laboratory Vibration Mill (Front View)
6. Interferences suspension system is designed to allow the machine to be
operated without any fastenings or anchorage. The grinding
6.1 No material normally applied to the calcined petroleum
vessels are secured by adjustable straps which have a quick-
coke is found to cause analytical interference with this proce-
release catch.The oscillator is supported on a bearing, fitted to
dure.
the body of the mill, and is driven by the motor by way of a
special clutch and a hollow flexible shaft.
7. Apparatus
7.4.2 The peak-to-peak amplitude of the vibration shall be
7.1 Analytical Balance, accurate to 6 0.1g.
4mm 6 0.5mm. A reference disc is fitted to the front of the
7.2 Rifflers, with hoppers and closures.
machine to measure the amplitude of vibration.
7.3 Wire Sieves,8mm( ⁄16in.)and4mm(5mesh),meeting 7.4.3 The motor shall be capable of 1450 r⁄min to
Specification E11. 1470r⁄min. The motor may be set up for 50Hz rather than
4 60Hzpower.Atachometercanbeusedtoverifythatthemotor
7.4 Laboratory Vibration Mill , having two grinding
is the specified r/min. The motor speed can be regulated with
vessels,eachfilledwith1kgofclean,hardsteelballs,diameter
a dc speed controller to adjust it to the specified r/min. The
10mm 6 0.4mm. The main features of the mill are shown in
bearing housing is rigidly connected to the bearings. The shaft
Figs. 1-5.
rotates inside the bearings with two steel imbalance discs
7.4.1 The mill and drive motor are mounted on a common
attached and is connected to the motor by way of the clutch.
baseplate.Thegrindingvesselsareinstalledinthebodyofthe
The imbalance discs are shown in Fig. 4.
mill, w
...

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: D6791 − 11 (Reapproved 2017) D6791 − 22
Standard Test Method for
Determination of Grain Stability of Calcined Petroleum
Coke
This standard is issued under the fixed designation D6791; 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—Units formatting was corrected editorially in February 2017.
1. Scope Scope*
1.1 This test method covers a laboratory vibration mill method for the determination of the grain stability of calcined petroleum
coke for the manufacture of carbon products used in the smelting of aluminum. Calcined petroleum coke with poor mechanical
strength may become degraded during mixing. Poor grain stability will affect the grain size and may result in poor quality of baked
blocks.
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D346 Practice for Collection and Preparation of Coke Samples for Laboratory Analysis
D2013 Practice for Preparing Coal Samples for Analysis
D2234/D2234M Practice for Collection of a Gross Sample of Coal
D6969 Practice for Preparation of Calcined Petroleum Coke Samples for Analysis
D6970 Practice for Collection of Calcined Petroleum Coke Samples for Analysis
E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves
2.2 ISO Standard:
ISO 6375 Carbonaceous Materials for the Production of Aluminum—Coke for Electrodes—Sampling
3. Terminology
3.1 Definitions:
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.05 on Properties of Fuels, Petroleum Coke and Carbon Material.
Current edition approved Jan. 1, 2017May 1, 2022. Published February 2017May 2022. Originally approved in 2002. Last previous edition approved in 20112017 as
ɛ1
D6791 – 11.D6791 – 11 (2017) . DOI: 10.1520/D6791-11R17E01.10.1520/D6791-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6791 − 22
3.1.1 calcined petroleum coke, n—petroleum coke that has been thermally treated to drive off the volatile matter and to develop
crystalline structure.
3.1.2 petroleum coke, n—solid, carbonaceous residue produced by thermal decomposition of heavy petroleum fractions, or
cracked stocks, or both.
4. Summary of Test Method
4.1 A representative sample of calcined petroleum coke is dried and screened to a 4 mm to 8 mm fraction. The resultant sample
is weighed so that two separate portions of 100.0 g 6 0.5 g mass are obtained. The samples are place into the laboratory mill and
ground for a specified period of time. After grinding the sample is screened and the mass of the +4 mm + 4 mm material is
determined. The grain stability is the percent of the original material remaining on the +4 mm + 4 mm sieve.
5. Significance and Use
5.1 The grain stability of calcined petroleum coke determines the resistance to breakdown of +4 mm + 4 mm particles used in the
manufacture of carbon anodes for use in the reduction process of aluminum.
5.2 Calcined petroleum cokes have to be relatively easy to grind for fines production but strong enough to withstand forming
pressures and thermal stresses occurring when the anodes are used in the reduction process.
6. Interferences
6.1 No material normally applied to the calcined petroleum coke is found to cause analytical interference with this procedure.
7. Apparatus
7.1 Analytical Balance, accurate to 60.1 g.6 0.1 g.
7.2 Rifflers, with hoppers and closures.
7.3 Wire Sieves, 8 mm ( ⁄16 in.) and 4 mm (5 mesh), meeting Specification E11.
7.4 Laboratory Vibration Mill , having two grinding vessels, each filled with 1 kg of clean, hard steel balls, diameter 10 mm 6
0.4 mm. The main features of the mill are shown in Figs. 1-5.
7.4.1 The mill and drive motor are mounted on a common base plate. The grinding vessels are installed in the body of the mill,
which is supported by four soft, flat springs. The spring suspension system is designed to allow the machine to be operated without
any fastenings or anchorage. The grinding vessels are secured by adjustable straps which have a quick-release catch. The oscillator
is supported on a bearing, fitted to the body of the mill, and is driven by the motor by way of a special clutch and a hollow flexible
shaft.
7.4.2 The peak-to-peak amplitude of the vibration shall be 4 mm 6 0.5 mm. A reference disc is fitted to the front of the machine
to measure the amplitude of vibration.
7.4.3 The motor shall be capable of 1450 r ⁄min to 1470 r ⁄min. The motor may be set up for 50 Hz rather than 60 Hz power. A
tachometer can be used to verify that the motor is the specified r/min. The motor speed can be regulated with a dc speed controller
to adjust it to the specified r/min. The bearing housing is rigidly connected to the bearings. The shaft rotates inside the bearings
with two steel imbalance discs attached and is connected to the motor by way of the clutch. The imbalance discs are shown in Fig.
4.
The sole source of supply of the vibration mill is Siebtechnik GmbH, P.O. Box/Postfach 10 17 51, D-25417 MUELHEIM an der RUHR, Germany. If you are aware
of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible
techni
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