Overview
ISO 18806:2019 specifies standardized laboratory methods for the determination of chlorine content in solid mineral fuels. The document defines two validated combustion routes - Method A (high temperature combustion) and Method B (high pressure vessel combustion) - and describes sample preparation, reagents, apparatus, analytical finishes and reporting. The procedure is applicable to solid mineral fuels and is intended for chlorine mass fractions > 0.005 %.
Key topics and technical requirements
- Two combustion methods
- Method A - High temperature combustion: sample combusted in an oxygen atmosphere in a fused-silica tube furnace (combustion zone at (1 250 ± 25) °C). Gaseous products are absorbed in water for subsequent analysis.
- Method B - High pressure vessel combustion: sample combusted in an oxygen-filled pressure vessel with an absorption solution to collect combustion products. Vessel safety and pressure control are specified.
- Analytical finishes: chlorine in the absorption solution can be measured by coulometric or potentiometric titration, spectrophotometry, or ion chromatography (IC).
- Reagents and gases: oxygen purity of at least 99.5 %, appropriate combustion aids, and deionised water (conductivity ≤ 0.2 mS/m) or alkaline absorbers (e.g., KOH/NaOH) for Method B/IC eluents.
- Apparatus and consumables: fused silica combustion tubes, porcelain boats, silica pushers, electrical tube furnace, flow meters, digestion vessels, pressure regulators and relief valves (pressure relief valve operating at 3.5 MPa for vessel systems).
- Sampling and sample prep: use the general analysis test sample ground to pass a 212 μm sieve; equilibrate moisture with laboratory atmosphere and determine moisture separately (per ISO moisture methods). Typical test portion sizes are about 50 mg to 1 000 mg depending on chlorine level.
- Quality control: blank-value determination, use of certified reference materials where applicable, and precision data (repeatability and reproducibility) are covered.
Applications and users
ISO 18806 is essential for:
- Coal, coke and solid fuel testing laboratories performing chlorine determination for fuel specification and regulatory compliance.
- Power plants and utilities assessing fuel corrosivity and emissions risk (chlorine can form corrosive compounds and affect ash behavior).
- Mining and fuel suppliers conducting quality control and acceptance testing.
- Environmental and analytical laboratories using ion chromatography, titration or spectrophotometry to quantify chloride from combustion traps.
- Manufacturers of combustion-analysis instrumentation and calorimetry/digestion equipment adapting or validating their systems to ISO requirements.
Related standards
Normative and related references cited in ISO 18806 include:
ISO 18806 provides a robust, traceable framework for accurate chlorine analysis in solid mineral fuels, enabling consistent reporting and informed decisions on fuel handling, combustion and emissions control.
