Overview
ISO 9406:1995 is an internationally recognized standard specifying a gravimetric analysis method for determining the volatile matter content in green coke used in aluminium production. This second edition replaces the original 1988 version, providing a refined approach to measuring volatile constituents in green coke with volatile matter contents exceeding 1% by mass. Green coke, a carbonaceous material derived from the distillation of mineral oil, undergoes this analysis to ensure it meets the technical and economic requirements essential for aluminium electrolytic processes.
Key Topics
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Scope and Applicability
Applicable to green coke used in aluminium production, particularly when volatile matter exceeds 1% (m/m). It ensures quality control by determining the precise volatile matter content, which impacts coke calcination and performance.
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Method Principle
Gravimetric analysis involves heating a test sample in a silica crucible at 900°C ± 20°C to expel volatile components, with the mass loss indicating the volatile matter percentage.
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Apparatus and Equipment
Essential equipment includes:
- Silica crucibles with tightly fitting lids (10–15g)
- A muffle furnace capable of maintaining 900°C ± 20°C
- Temperature measuring devices with thermocouples (0°C to 1000°C range)
- Laboratory oven adjustable to 120°C ± 5°C for sample drying
- A support for holding multiple crucibles to ensure uniform heating
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Sampling and Sample Preparation
Samples must be prepared according to ISO 6375, with careful crushing and sieving through a 250 µm mesh. Drying the sample to a constant mass at 120°C ± 5°C is crucial before testing. Two test portions per sample ensure accuracy.
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Testing Procedure
After weighing the dry sample, it is heated in the muffle furnace for approximately 7 minutes, then cooled, desiccated, and reweighed. The volatile matter content is calculated from the mass loss.
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Precision and Accuracy
Repeatability (r) is approximately 0.2% m/m, while reproducibility (R) is about 0.7% m/m. These values reflect the method’s reliability for laboratory testing.
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Reporting Requirements
Test reports should include sample identification, reference to ISO 9406:1995, detailed results with units, any observations, and deviations from standard procedures.
Applications
ISO 9406:1995 is critical for industries and laboratories involved in:
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Aluminium Production
Ensuring green coke quality for efficient and effective calcination processes, directly impacting electrode manufacturing and overall aluminium electrolytic cell performance.
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Quality Control Laboratories
Routine testing of green coke batches to monitor volatile matter content, facilitating inventory management, process optimization, and supplier compliance.
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Carbon Materials Manufacturing
Standardizing volatile matter measurement in green coke to support consistent raw material specifications.
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Research and Development
Investigating the influence of volatile matter on carbonaceous materials properties and behaviours in aluminium production processes.
Related Standards
- ISO 6375:1980 – Carbon products for aluminium production - Sampling of cokes for electrodes
- ISO 565:1990 – Laboratory sieves - Nominal dimensions and test sieves
- ISO 5725-1:1994 – Accuracy (trueness and precision) of measurement methods - General principles and definitions
- ISO 5725-2:1994 – Accuracy (trueness and precision) of measurement methods - Basic method for the determination of repeatability and reproducibility
Keywords
carbonaceous materials, green coke, volatile matter, gravimetric analysis, aluminium production, coke analysis, ISO 9406, quality control, calcination, muffle furnace, metallurgical coke, laboratory testing, sample preparation, repeatability, reproducibility, industrial standards
ISO 9406:1995 defines a robust, reproducible method essential for maintaining the quality and consistency of green coke used in aluminium manufacturing. Adopting this standard supports efficient production, cost control, and safety in the aluminium industry worldwide.