ISO 609:2025

Overview

ISO 609:2025 - "Coal and coke - Determination of carbon and hydrogen - High temperature combustion method" specifies a laboratory procedure for determining total carbon and total hydrogen in coal and coke by high‑temperature combustion and gravimetric absorption. The third edition (2025) updates the 1996 version and defines equipment, reagents, sample preparation, combustion conditions and calculations so results include carbonates and hydrogen in moisture and silicates (with provision for corrections).

Keywords: ISO 609:2025, coal and coke, high temperature combustion method, determination of carbon and hydrogen, total carbon, total hydrogen.

Key topics and technical requirements

• Principle: Burn a known mass of sample in oxygen at ~1 350 °C; convert hydrogen to H2O and carbon to CO2; absorb and determine products gravimetrically.
• Apparatus: furnace with a 125 mm hot zone reaching 1 350 °C, auxiliary zone to keep the silver gauze roll at ~600–800 °C, refractory combustion tube (≈28 mm OD, 650 mm length), combustion boats, and Midvale absorption tubes.
• Absorption train: arranged in the flow direction with magnesium perchlorate (for water), sodium hydroxide on inert base (for CO2), then magnesium perchlorate again; glass wool used to prevent carry‑over.
• Reagents: anhydrous magnesium perchlorate, coarse sodium hydroxide on inert base (self‑indicating preferred), alumina lining, sodium tetraborate titrant, hydrogen peroxide, mixed indicators and oxygen (hydrogen‑free). Safety warnings are specified for toxic/corrosive reagents and disposal of perchlorate.
• Procedure highlights: sample preparation, conditioning of the absorption train, combustion steps, blank tests, simultaneous moisture determination and corrections (for moisture and carbonate carbon), and gravimetric/titrimetric calculations.
• Quality: Clauses on precision (repeatability and reproducibility) and detailed test reporting requirements are included.

Applications and users

ISO 609:2025 is intended for:

• Analytical laboratories performing routine and reference testing of coal and coke.
• Quality control teams in mining, coke production and power generation to determine fuel composition.
• Engineers and researchers assessing fuel properties for combustion performance, emissions estimation and material balance.
• Regulatory bodies and certification agencies requiring standardized composition data for trade and environmental compliance.

Practical benefits: reliable total carbon/hydrogen values for calorific calculations, emissions inventories, process optimization and contract quality verification.

Related standards

• ISO 625 - alternative method for carbon/hydrogen determination.
• Normative references cited: ISO 687, ISO 925, ISO 5068‑2, ISO 11722, ISO 13909‑4 / ISO 13909‑6, ISO 18283.

Using ISO 609:2025 ensures reproducible, internationally comparable measurements of carbon and hydrogen in coal and coke by a well‑specified high‑temperature combustion method.