Overview
ISO 21663:2020 specifies an instrumental method for the determination of total carbon (C), hydrogen (H), nitrogen (N) and sulphur (S) in solid recovered fuels (SRF). The standard covers both micro (milligram test portions) and macro (gram test portions) instrumental apparatus, and is applicable on a dry-matter basis for concentrations of C > 0.1%, H > 0.1%, N > 0.1% and S > 0.05%. The method is based on complete combustion of a known sample mass and quantitative gas analysis of the combustion products (CO2, H2O, N2/NOx, SOx).
Key Topics and Requirements
- Principle: Oxidative combustion of the SRF sample (typical furnace temperature ≈ 1 250 °C) with catalytic conversion and subsequent instrumental gas analysis.
- Micro vs. macro methods: Choice of apparatus depends on test‑portion mass (micro: mg, macro: g); micro methods require very careful sample preparation.
- Sample preparation:
- Laboratory sample → general analysis sample → test portion
- Nominal top size of the test sample: ≤ 1 mm (finer sizes may be required for some instruments)
- Moisture determination (if analysis is on dry basis) per ISO 21660‑3
- Storage and conservation guidance in Annex A
- Apparatus and reagents:
- Carrier gas (e.g., helium 99.99% v/v) and oxygen (≥ 99.95% v/v) or instrument‑specified purities
- Combustion tube, catalysts, detectors and a balance with at least 0.1% resolution
- Tungsten wire must not be used for sulfur determination (it acts as a sulfur trap); copper wire is suggested as an alternative
- Calibration and standards:
- Use of pure organic calibration standards (e.g., acetanilide, BBOT) and control biomass materials (examples: alfalfa, oatmeal, flours) with traceable values
- Quality and performance:
- Conversion of NOx to N2, conversion of S and halide-associated hydrogen to H2O, and detector linearity/response characteristics are addressed
- Precision, robustness and reporting requirements are defined (see clauses on performance characteristics and test report)
Applications and Users
- Practical for labs performing CHNS analysis of SRF for regulatory reporting, quality control, fuel characterization and calorific value estimation.
- Primary users: analytical testing laboratories, waste-to-energy facilities, SRF producers, environmental laboratories and regulatory bodies assessing fuel composition and compliance.
- Useful for process optimization, emissions estimation and material specification in recycling and energy recovery operations.
Related Standards
- ISO 21637 - Terminology and definitions for SRF
- ISO 21660‑3 - Moisture determination (oven dry method) for general analysis samples
- ISO 21646 - Sample preparation for solid recovered fuels
Keywords: ISO 21663:2020, solid recovered fuels, SRF, CHNS analysis, carbon hydrogen nitrogen sulphur, instrumental method, combustion analysis, sample preparation, calibration standards.