Overview
ISO 2950:1974 is an international standard developed by the International Organization for Standardization (ISO) that provides a systematic classification of brown coals and lignites. The classification is based primarily on two critical properties: total moisture content and tar yield. Both properties are calculated on specific bases to ensure consistency - total moisture on an ash-free basis, and tar yield on a dry, ash-free basis. This standard supports the coal industry and related sectors by offering a clear, comparable framework to categorize brown coals according to these influential quality factors.
Key Topics
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Classification by Moisture Content
Brown coals and lignites are first divided into classes depending on their total moisture content. This is calculated on an ash-free basis to provide a consistent parameter across different samples. The moisture content ranges from less than 20% up to more than 60%, grouped into six distinct classes. This classification impacts the usage, handling, and energy properties of the coal.
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Classification by Tar Yield
Within each moisture class, the coal is further grouped by tar yield - a measure of the tar produced during low-temperature distillation of coal. Tar yield is calculated on a dry, ash-free basis, reflecting the coal's potential for byproduct recovery and energy value. Group numbers are assigned based on defined tar percentages.
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Two-Digit Code System
ISO 2950 defines a two-digit code to represent the coal type, where:
- The first digit indicates the class based on total moisture content
- The second digit represents the tar yield group
This coding provides a concise and standardized way to identify and compare brown coal types internationally.
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Reference Methods for Determination
The standard references precise analytical methods for determining moisture content (ISO/R 1015), tar yield (ISO/R 647), and ash content (ISO/R 1171), ensuring reliable and reproducible results in classification.
Applications
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Coal Industry and Mining Operations
Accurate classification according to ISO 2950 facilitates optimized extraction strategies and quality control, helping producers classify brown coal reserves by commercial and technical value.
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Energy Production and Fuel Selection
Power plants and fuel suppliers utilize these classifications to select suitable coal types, balancing moisture and tar content for efficient combustion and energy output.
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Byproduct Recovery and Chemical Processing
Understanding tar yield is essential for processes aiming to recover coal tar and related chemicals, allowing industries to evaluate feedstock suitability.
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International Trade and Regulation
Standardized classification supports transparent communication, trade negotiations, and regulatory compliance by providing a universally accepted terminology and categorization.
Related Standards
- ISO/R 647: Method for determining yields of tar, water, gas, and coke residue from low-temperature distillation of brown coal and lignite.
- ISO/R 1015: Method for determining moisture in brown coals and lignites by direct volumetric measurement.
- ISO/R 1171: Method for determining ash content in solid mineral fuels.
Summary
ISO 2950:1974 provides a practical and internationally recognized framework for classifying brown coals and lignites based on moisture and tar yield. This classification enhances quality assessment, process optimization, and international trade within the coal and energy sectors. It supports consistent communication and technical evaluation across global markets by establishing clear parameters and coding systems essential for stakeholders involved in coal utilization and processing.
Open preview (PDF)Brown coals and lignites — Classification by types on the basis of total moisture content and tar yield
