Overview
ISO 587:2020 - Coal and coke - Determination of chlorine using Eschka mixture specifies a standardized laboratory method to measure chlorine content in hard coal, brown coals, lignites and coke. The method converts organic-bound chlorine to soluble alkaline chlorides by igniting a weighed test portion in intimate contact with an Eschka mixture, then extracts and quantifies chloride by titration (Volhard or Mohr) or potentiometric titration using an ion selective electrode (ISE).
Key topics and technical requirements
- Principle: Combustion in an oxidizing atmosphere with Eschka mixture to convert chlorine to alkaline chlorides, followed by extraction and titration or potentiometry.
- Eschka mixture composition: 2 parts light calcined magnesium oxide (MgO) to 1 part anhydrous sodium or potassium carbonate; sieved to 0.212 mm.
- Sample preparation: General analysis test sample prepared to nominal top size 212 μm; moisture equilibrium and thorough mixing before analysis.
- Test portion: Approximately 1 g (for expected Cl > 0.1 %) or 2 g (for lower expected chlorine).
- Combustion conditions: Electrically heated muffle furnace maintained at 675 °C ± 25 °C; specified procedures for coals and coke (crucible placement and heating cycles).
- Completion/determination methods:
- Volhard method - precipitation with AgNO3 (c = 0.025 mol/L), back-titration with KSCN; organic solvent and iron(III) alum indicator used.
- Mohr method - direct titration with AgNO3 (c = 0.050 mol/L) using potassium chromate indicator.
- ISE method - potentiometric titration with a chloride ion selective electrode and double-junction reference electrode.
- Apparatus & reagents: Analytical balance (0.1 mg), platinum/silica/glazed porcelain crucibles, muffle furnace, specified reagent grades and concentrations.
- Quality and reporting: Includes provisions for blank tests, expression of results (air-dried or other bases), and precision statements (repeatability and reproducibility limits).
Note: The standard includes safety cautions (toxic/corrosive reagents) and guidance on avoiding unburnt residues and filtration when necessary.
Applications and who uses it
- Laboratories performing routine chemical analysis of coal and coke for quality control and specification compliance.
- Coal producers, coke manufacturers and buyers assessing fuel chlorine content to predict corrosion, fouling, and emissions impacts.
- Environmental and regulatory agencies monitoring chlorine as part of emissions and combustion residue characterization.
- Research institutions studying fuel properties, combustion behavior, and material compatibility.
ISO 587:2020 is essential where accurate chlorine determination in coal and coke affects process design, boiler maintenance, and environmental compliance.
Related standards
Keywords: ISO 587:2020, chlorine determination, Eschka mixture, coal and coke analysis, Volhard, Mohr, ISE, muffle furnace, chloride titration.
