Overview
ISO 17499:2023 - "Carbonaceous materials used in the production of aluminium - Determination of baking level expressed by equivalent temperature" specifies a laboratory and field method to quantify the baking level of carbon anodes and cathodes used in aluminium production. The standard defines the concept of equivalent temperature (°E), describes preparation and use of a reference green coke, and explains how to determine equivalent temperature from the mean crystallite height (Lc) measured by X‑ray diffraction.
Key topics and requirements
- Principle: Embed a graphite container with a test portion of reference green coke in a stub‑hole of an anode or cathode; after baking, recover and analyze the calcined coke to determine Lc and convert to equivalent temperature using a calibration curve.
- Reference coke: Use a single‑source, low‑sulfur green petroleum coke (–4 mm grains, dried at 110 °C). Batch control and mixing by splitting/recombining are recommended.
- Calibration curve: Prepare by heat‑treating multiple reference samples (rapid heating, 2 h hold time, quench) at different hold temperatures and measuring Lc. A third‑order polynomial fit (Tc = a·Lc^3 + b·Lc^2 + c·Lc + d) is used. New reference batches can be calibrated against an existing calibrated coke; calibration should cover about 1 050 °E to 1 400 °E.
- Apparatus & sampling:
- Small furnace able to heat 15–30 g to ~1 000–1 500 °C in 6–8 min (inert gas).
- Graphite crucible (typical: outer Ø 40 mm, inner Ø 20 mm, length 90 mm) with vented lid.
- Swing mill for grinding; X‑ray diffractometer for Lc measurement per ISO 20203.
- Typical test portion: ~15 g.
- Test procedure: Place crucible in anode/cathode before baking; recover carefully to avoid graphite contamination; grind and analyze; convert Lc to °E via calibration curve.
- Expression of results: Rules for duplicate/quadruple parallels and reporting averages and standard deviation for section mapping are specified.
- Precision: Precision figures are reported based on an ISO interlaboratory comparison (referenced in the standard).
Applications and users
ISO 17499:2023 is intended for:
- Aluminium smelter quality control and furnace process engineers monitoring bake uniformity.
- Materials and metallurgical laboratories performing anode/cathode characterization.
- R&D and test laboratories comparing bake cycles, furnace designs, or reference anode samples.
- Suppliers of carbonaceous materials needing to validate baking performance.
Practical applications include furnace mapping, process control, comparative testing of anodes/cathodes, and ensuring consistent calcination conditions for production reliability.
Related standards
- ISO 20203 - Determination of crystallite size of calcined petroleum coke by X‑ray diffraction (referenced for Lc measurement).
- Developed by ISO/TC 226 (Materials for the production of primary aluminium).
Keywords: ISO 17499:2023, equivalent temperature, baking level, carbonaceous materials, aluminium production, reference coke, calibration curve, X‑ray diffractometer, anode baking.
