Overview
ISO 540:2008 - Hard coal and coke - Determination of ash fusibility - specifies a laboratory method to determine the characteristic fusion temperatures of ash produced from hard coal and coke. Based on the traditional Seger‑cone approach, the standard defines how to prepare ash test pieces, heat them under controlled conditions, observe defined shape transitions and record fusion points. This test provides an indicator of ash melting behavior and slagging propensity in thermal processes.
Key topics and technical requirements
- Scope: Determines deformation and melting behavior of coal and coke ash under controlled heating.
- Characteristic temperatures (defined terms):
- DT (Deformation Temperature) - first rounding of edges.
- ST (Sphere Temperature) - height equals base width (or edges fully round).
- HT (Hemisphere Temperature) - height equals half the base diameter.
- FT (Flow Temperature) - melt spread height equals one‑third of the hemisphere height.
- Principle: Heat an ash test piece at a controlled rate and continuously observe shape changes.
- Test atmosphere:
- Reducing: CO/CO2 (55–65% CO) or H2/CO2 mixtures - minimum flow ~400 mm/min past the specimen.
- Oxidizing: air or CO2.
- Safety warning: vent CO/H2 exhaust and purge to avoid explosion risk.
- Apparatus & materials:
- High‑temperature electrically heated furnace (up to ~1 500 °C) with observation window.
- Pyrometer (Pt/Pt‑Rh thermocouple) and regular calibration checks using gold, nickel, palladium melting points.
- Moulds for producing sharp‑edged test pieces (pyramids, cubes, cylinders, truncated cones) and non‑reactive supports (sintered alumina, mullite, or platinum foil where needed).
- Flowmeters, agate mortar, 0.075 mm sieve, and optical/video observation equipment.
- Sample preparation: Ash prepared per ISO 1171, ground (
