ISO 4689-3:2017

Overview

ISO 4689-3:2017 specifies a combustion/infrared method for the determination of sulfur content in iron ores. The procedure uses a high-frequency induction furnace to combust a prepared sample in oxygen and measures evolved SO2 with an infrared detector. It applies to natural iron ores, iron ore concentrates and agglomerates (including sinter) with sulfur contents from 0.002 % to 0.25 % (mass fraction). The method has limitations for samples with high combined water content (see Key Topics).

Key topics and technical requirements

• Scope and limits
  • Applicable sulfur range: 0.002 % – 0.25 %.
  • Not applicable to ores with > 1.0 % combined water. With a heated metal filter, apparatus can treat ores with < 3.0 % combined water.
• Principle
  • Sample mixed with a flux (containing iron, tin, tungsten) and combusted in a high-frequency induction furnace using oxygen.
  • Evolved SO2 is carried to an infrared absorption detector for quantification.
• Reagents and calibration
  • Reagents specified (examples): metallic iron, tin, tungsten (very low S content), magnesium perchlorate drying agent, NaOH absorption media.
  • Calibration via standard sulfur solutions prepared from dried potassium sulfate; recommended calibration series provided.
• Apparatus
  • High-frequency induction furnace (heating coil, 1 200 °C capacity).
  • Quartz combustion tube, refractory crucible, tin capsules, metal filter with heating device, dust trap, IR detector and measuring cell.
• Sampling and sample preparation
  • Laboratory sample typically −100 µm (use −160 µm where combined water/oxidizable compounds are significant).
  • Prepare predried test samples by drying at 105 °C ± 2 °C (ISO 7764).
  • Typical test portion: ~0.5 g (use 0.2 g when sulfur > 0.1 %).
• Quality control
  • Minimum duplicate determinations; include blank test and certified reference material (CRM) in each run.
  • Procedures for calibration graph, calculation, repeatability and between-laboratory precision are included.
• Safety
  • Method involves hazardous materials and high temperatures; users must apply appropriate health and safety practices.

Applications and users

• Routine sulfur analysis in mining and mineral processing labs.
• Quality control for iron ore concentrates, sinter products and raw ore prior to smelting or trading.
• Analytical and contract laboratories performing chemical characterization for production control, specification compliance and shipment certification.
• Useful for metallurgical engineers, QA/QC managers, assay labs and regulatory bodies monitoring sulfur content.

Related standards

• ISO 4689 series (other parts for sulfur/iron ore analysis)
• ISO 3082 - Sampling and sample preparation procedures
• ISO 7764 - Preparation of predried test samples
• ISO 2596 - Determination of hygroscopic moisture
• ISO 648 / ISO 1042 - Laboratory glassware specifications
• ISO Guide 35 - Reference material certification

Keywords: ISO 4689-3:2017, sulfur determination, iron ores, combustion/infrared method, high-frequency induction furnace, sulfur analysis, iron ore concentrates, sinter products, laboratory procedures.