Overview
ISO 12980:2000 defines an X‑ray fluorescence (XRF) method for determining elemental impurities in green and calcined petroleum coke used to manufacture electrodes (anodes) for aluminium production. The standard covers sample preparation, instrument configuration, calibration, drift monitoring and expression of results for key impurities that affect anode performance and aluminium quality.
Key topics and technical requirements
- Principle: Analysis by XRF of a pressed tablet (pulverized coke + organic binder). Secondary (characteristic) X‑radiation from the sample is wavelength‑dispersed by crystals and detected according to Bragg’s law.
- Sample preparation
- Sampling in accordance with ISO 6375.
- Crush to pass a 4 mm sieve, dry to constant mass at 120 °C, mill to pass a 63 µm sieve.
- Typical mix: ~30 g sample + ~5 g organic binder (e.g., Hoechst wachs G or stearic acid); remill and press into a tablet.
- Pressing: tablet press capable of 20 tonne load; recommended specimen thickness ≥ 4 mm; press 20 t for 20 s.
- Instrumentation
- XRF spectrometer with crystals such as LiF, PE, PX1, Ge, TIAP, LSM; choice of scandium (side‑window tubes) or rhodium (end‑window tubes) depending on elements targeted.
- Detector gas: 90% argon / 10% methane.
- Measurement and calibration
- Typical measurement conditions and collimation, kV/mA and counting times are apparatus‑dependent; example conditions are provided in the standard.
- Calibration uses certified reference materials spanning the specified mass fraction ranges (e.g., S: 0.5–5%; V, Ni, Al, Fe, Si: 20–500 µg/g; Na, Ca: 20–200 µg/g).
- Matrix corrections for absorption/enhancement (de Jongh model, Traill‑Lachance) are applied where required.
- Quality control
- Use of monitor standards or reference samples for drift detection; calculation of drift factor and criteria for recalibration.
- Guidance on counting statistics and minimum counting time to meet targeted precisions (e.g., 2% for Na, 1% for other elements at 2σ).
Applications and users
- Practical use for anode manufacturers, aluminium smelters, process and quality control laboratories, and analytical service providers who need to quantify elemental impurities in petroleum coke.
- Supports materials acceptance, process control, anode quality assurance and investigations into anode consumption and metal quality affected by trace elements.
Related standards
- ISO 6375 - Carbonaceous materials for the production of aluminium - Coke for electrodes - Sampling (referenced for sampling procedure).
- Prepared by ISO/TC 47 (Chemistry), SC 7 - relevant to aluminium and carbonaceous product standardization.
Keywords: ISO 12980:2000, XRF method, green coke, calcined coke, petroleum coke, elemental impurities, anodes, aluminium production, calibration, monitor standard.