Overview
ISO/TS 4676:2022 - Coal - Determination of carboxyreactivity - specifies a laboratory method to measure the reactivity of coal (and coke) with carbon dioxide (CO2), commonly called carboxyreactivity. The technique quantifies the ability of coal/coke to convert CO2 to CO under controlled heating and gas-flow conditions. Results help evaluate coal quality for coal gasification, combustion, and related processes such as indirect liquefaction.
Key topics and requirements
- Scope: Applicable to coal and coke for gasification/combustion purposes; integrates/modifies GB/T 220.
- Principle: Carbonize a 3–6 mm coal fraction (except coke), place the coke residue in a high‑temperature reaction tube, pass CO2 at a controlled flow rate and temperature program, and measure residual CO using a gas analyser. Calculate the fraction α (%) of CO produced as the carboxyreactivity index.
- Sample preparation:
- Test fraction: 3 mm to 6 mm (prepared per ISO 13909‑4 and ISO 18283).
- Carbonization: dry distillation at (900 ± 20) °C for 1 h to remove volatiles (not required for coke).
- Apparatus & reagents:
- Reaction furnace and reaction tube capable to 1 100–1 300 °C, Pt/Rh thermocouple, flowmeter, CO cylinder (≥98 %), gas analyser (IR spectrometer or gas chromatograph allowable).
- Reagents like anhydrous CaCl2, H2SO4, KOH/NaOH solution for gas washing/drying.
- Procedure highlights:
- Typical CO2 flow rate: 500 ml/min (adjusted per Annex A for pressure/temperature).
- Start temperatures: ~750 °C for brown coals/lignites, ~800 °C for bituminous/anthracite; measurements taken at 50 °C increments up to 1 100 °C (or 1 300 °C if required).
- Duplicate determinations are required; results rounded to 0.1 %.
- Result expression:
- Compute α (%) from measured CO volume fraction; plot α versus temperature to produce a reactivity curve.
- Reporting & precision:
- Test report must identify the sample, method (ISO/TS 4676:2022), date and results.
- Repeatability and reproducibility limits to be provided after interlaboratory studies.
Applications
- Evaluating coals and cokes for gasification plant feedstock selection.
- Assessing reactivity parameters for combustion optimization and process modelling.
- Supporting coal trading and quality control where CO2 reactivity affects process efficiency and gas composition.
- Research into coal conversion kinetics and comparative fuel performance.
Who should use this standard
- Coal testing laboratories and quality-control units.
- Gasification and combustion plant engineers.
- Coke producers assessing feedstock reactivity.
- Researchers and consultants working on coal conversion technologies.
Related standards
- ISO 1213‑2 (vocabulary - sampling, testing, analysis)
- ISO 18283 (manual sampling of coal and coke)
- ISO 13909‑4 (mechanical sampling - test sample preparation)
Keywords: ISO/TS 4676:2022, coal carboxyreactivity, determination of carboxyreactivity, CO2 reactivity, coal gasification, coke reactivity, gas analysis.