ISO 7404-2:2009

Overview

ISO 7404-2:2009 - Methods for the petrographic analysis of coals - Part 2: Methods of preparing coal samples defines standardized procedures for preparing polished particulate blocks (and embedded lumps) from crushed coal for analysis by reflectance microscopy. The standard describes sampling preparation, required apparatus and materials, binder selection, moulding and curing considerations, and grinding/polishing and cleaning regimes to produce a relief‑free, scratch‑free surface suitable for petrographic study.

Key topics and technical requirements

• Scope and principle: Produce a representative, polished surface exposing at least 50% coal for microscopy and reflectance measurements.
• Sample preparation: Air‑drying per ISO 18283, size reduction to pass a 1.00 mm sieve, and laboratory sample division (50–100 g) to ensure representativity.
• Binders and mounting: Properties required include chemical inertness, compatibility with immersion oil, suitable curing temperatures (preferably <60 °C for some resins; PMMA thermoplastic annealing ≈120 °C), good wetting/penetration, hardness comparable to coal, minimal curing shrinkage, and low segregation tendency.
• Apparatus: Test sieve (1.00 mm), grinding mill or mortar, press (capable up to 21 MPa for pressure moulding), moulds, pelletizing/mounting machines, grinder/polisher with contra‑rotating specimen holder, ultrasonic cleaner and desiccator.
• Abrasives and polishing: Recommended silicon carbide grinding papers (examples: 53.5 µm / 240 grit, 23.6 µm / 400 grit, 16.0 µm / 600 grit) or diamond disks; polishing abrasives down to a final particle size ≤ 0.05 µm (e.g., colloidal silica or diamond paste). Thorough washing (tap and distilled water) and ultrasonic cleaning between stages is essential.
• Operator judgement: Due to variability in coal rank, maceral composition and mineral inclusions, the standard allows experienced operators to adapt procedures; Annex A provides example procedures.

Applications

• Preparation of coal samples for vitrinite reflectance measurement and maceral/microlithotype analysis.
• Quality control and characterisation in coal mining, coal preparation plants, power generation, coke and steel industries, research laboratories, and cargo/sample certification.
• Useful when assessing coal rank, blend uniformity and the distribution of mineral matter prior to petrographic or optical analysis.

Who should use this standard

• Coal petrographers, analytical laboratories, QC managers in coal‑related industries, researchers in fuel and geoscience labs, and instrument/mounting technicians performing reflectance microscopy.

Related standards and references

• ISO 7404-1 (Vocabulary)
• ISO 18283 (Manual sampling for hard coal and coke)
• ISO 3310-1 (Test sieves)
• ICCP International Handbook of Coal Petrography

Keywords: ISO 7404-2:2009, petrographic analysis of coals, preparing coal samples, polished particulate block, reflectance microscopy, vitrinite reflectance, coal sample preparation, grinding and polishing.