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D2799-23 – Standard Test Method Technical Guide
📜 Scope and Application of D2799-23
The ASTM D2799 – 23 standard, Standard Test Method for Microscopical Determination of the Maceral Composition of Coal, establishes the equipment and methodology for determining the physical composition of a coal sample. The analysis results are expressed as the volume fraction of organic components (macerals) and mineral matter, determined specifically through a systematic manual point count. This standard is under the jurisdiction of ASTM Committee D05 on Coal and Coke, specifically Subcommittee D05.28 on Petrographic Analysis of Coal and Coke. Originally approved in 1969, it was last revised and approved in February 2023 (D2799-23).
✅ International Alignment: This international standard was developed in accordance with the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the WTO TBT Committee, ensuring global relevance.
The standard reminds users that while it is comprehensive, it does not address all safety concerns. It is the responsibility of the user to establish appropriate safety, health, and environmental practices. Furthermore, the standard acknowledges that the term “weight” is used temporarily due to established trade usage, cautioning that force (newton) and mass (kilogram) are distinct SI quantities.
🪨 Maceral Groups and Classification Systems
Per Terminology D121, the standard defines specific classifications for microscopic constituents. The table below outlines the three primary maceral groups and their constituent macerals as defined in the standard.
| 🟦 Maceral Group | 📋 Maceral |
|---|---|
| Vitrinite | — |
| Liptinite | alginite, cutinite, resinite, sporinite |
| Inertinite | fusinite, inertodetrinite, macrinite, micrinite, funginite, secretinite, semifusinite |
In addition to the standard classification, the standard provides a simplified classification frequently used by laboratories associated with the coke-making industry for petrographic analysis of bituminous coal.
| 🟧 Simplified Group (Coke Industry) | 📋 Maceral |
|---|---|
| Vitrinite | vitrinite |
| Liptinite | liptinite (other than resinite), resinite |
| Inertinite | semifusinite, micrinite, fusinite, mineral matter |
The standard also defines specific maceral terms, such as alginite, a liptinite maceral that is generally spherical or ovoid, frequently having a crenulated border and somewhat irregular reflectance, sometimes occurring in clusters reflecting an origin from Botryococcus algae.
⚙️ Methodology and Supporting Standards
Successful execution of this test method depends on a thorough understanding of several critical companion ASTM standards:
- D2797 (Sample Preparation): Specifies the exact practice for preparing coal samples for microscopical analysis by reflected light, which is mandatory for accurate maceral identification.
- E562 (Point Count): The core mathematical and procedural framework for determining the volume fraction by systematic manual point count, directly governing the counting statistics.
- D2798 (Vitrinite Reflectance): Provides the complementary method for determining the reflectance of vitrinite, a key parameter for coal rank.
- E691 (Interlaboratory Precision): Provides the standard practice for conducting interlaboratory studies to determine the precision of the test method.
💡 Critical Procedure Note: The manual point count is a systematic process. Accurate identification requires a polished surface free of relief and a proper understanding of maceral morphology. Referencing the photomicrographs and descriptions in the standard (and associated resources) is highly recommended.
❓ Frequently Asked Questions
🔍 What is the official designation of this test method?
The official designation of the standard is D2799-23. The number immediately following the designation indicates the year of original adoption or last revision.
💡 What is the method used for determining the volume fraction of macerals?
The standard specifies the use of a systematic manual point count. This procedure is outlined in the referenced ASTM standard E562, Test Method for Determining Volume Fraction by Systematic Manual Point Count.
⚡ What are the three main maceral groups defined in the standard?
The three main maceral groups are Vitrinite, Liptinite (which includes alginite and sporinite), and Inertinite (which includes fusinite and semifusinite).
📌 How does the standard address the use of the term “weight”?
The standard explicitly notes that the term “weight” is used temporarily due to established trade usage. It cautions the user that it is used to mean both force and mass, and care must be taken to determine which is meant in each case.