Overview
ISO 23873:2010 - Hard coal - Method for the measurement of the swelling of hard coal using a dilatometer specifies a laboratory method to measure the thermal swelling (dilatation) and contraction behaviour of hard coal. The method uses a dilatometer in which a pencil-shaped coal test piece is heated in a steel retort while a piston resting on the sample records vertical movement. The recorded piston trace characterizes softening temperature, maximum contraction, and maximum dilatation of the coal.
Keywords: ISO 23873:2010, hard coal swelling, dilatometer, coal dilatometry, coal testing
Key topics and technical requirements
- Principle: Heat a prepared coal pencil at a controlled rate and continuously record piston movement versus time/temperature to derive swelling characteristics.
- Temperature control & calibration:
- Heating rate: 3 °C/min (mean) up to 550 °C.
- Calibration using reference metals (lead mp 327.0 °C, zinc mp 419.3 °C) or an independently calibrated probe; periodic recalibration required (e.g., after set number of tests or months).
- Apparatus:
- Steel mould and press for preparing pencil test pieces.
- Dilatometer furnace with multiple retorts; retort internal diameter 8.00 mm ± 0.05 mm.
- Steel piston assembly adjusted to a combined mass of 150 g ± 5 g; piston-to-retort clearance specified.
- Recording system for piston movement (mechanical pen/chart or transducer/recorder) with defined vertical and horizontal scales.
- Procedure:
- Test-sample preparation (powdered coal compressed into pencils).
- Temperature calibration, sample placement in retort, controlled heating, and continuous recording.
- Expression of results includes softening temperature, temperatures of maximum contraction/dilatation, and percent changes relative to initial length.
- Quality and precision: The standard addresses repeatability and reproducibility criteria and requires specific checks (e.g., retort wear limits, furnace temperature uniformity).
Applications
- Characterizing swelling behaviour relevant to coking, carbonization and thermal processing of coal.
- Coal quality control in mines and coke-producing plants.
- Research and development in coal petrography, fuel performance, and thermal treatment processes.
- Comparative testing for coal classification and process optimisation.
Who should use this standard
- Coal testing laboratories and QA/QC teams
- Coke and metallurgical coal producers
- Research institutions studying coal thermal properties
- Standards bodies and equipment manufacturers of dilatometers
Related standards
- ISO 1213-2 (vocabulary for sampling/testing)
- ISO 13909-4 (mechanical sampling and preparation of coal test samples)
This concise summary helps engineers, laboratory managers, and researchers find, interpret and apply ISO 23873:2010 for regulated and reproducible measurement of hard coal swelling using a dilatometer.