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D388-23 – Standard Test Method Technical Guide
📜 Scope and Applicability of ASTM D388-23
ASTM D388-23 establishes the standard classification of coals by rank, defined by their degree of metamorphism or progressive alteration in the natural series from lignite to anthracite. This classification is specifically applicable to coals that are composed mainly of the maceral vitrinite, as the rank‑determining parameters are calibrated for vitrinite‑rich coal seams.
⚠️ Important Limitation for Vitrinite‑Poor Coals: Coals rich in inertinite or liptinite (exinite), or both, cannot be properly classified using the standard rank parameters. In these macerals, the properties that determine rank (calorific value, volatile matter, and agglomerating character) differ greatly from those of vitrinite in the same coal. For such nonbanded coals, the degree of metamorphism can be estimated by isolating vitrinite fractions or by determining the reflectance of the vitrinite using Test Method D2798.
⚙️ Classification Parameters and Reference Methods
Rank is defined by three key parameters: calorific value (moist, mineral‑matter‑free basis), volatile matter (dry, mineral‑matter‑free basis), and agglomerating character. Per the standard, Btu/lb is the standard unit for calorific value limits, with SI equivalents provided for reference. Equilibrium moisture for the moist basis is determined at 96 to 97 % relative humidity and 30 °C (Test Method D1412/D1412M). The following table summarizes the complete classification system.
| 🟦 Class / Group | 📏 Fixed Carbon (dmmf, %) | 📐 Volatile Matter (dmmf, %) | 🎯 Calorific Value (moist mm‑free, Btu/lb) | ⚡ Agglomerating Character |
|---|---|---|---|---|
| I. Anthracitic | ||||
| 1. Meta‑Anthracite | ≥ 98 | ≤ 2 | — | Nonagglomerating |
| 2. Anthracite | 92 – < 98 | 2 – 8 | — | Nonagglomerating |
| 3. Semianthracite¹ | 86 – < 92 | 8 – 14 | — | Nonagglomerating |
| II. Bituminous | ||||
| 1. Low Volatile | 78 – < 86 | 14 – 22 | — | Agglomerating²
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