Overview
ISO 975:2021 specifies a semi-automatic method for determining the yield of benzene-soluble extract in brown coals and lignites. This standard outlines the use of a dedicated extraction instrument that combines extraction, rinsing, and evaporation processes to accurately quantify benzene-soluble extracts. This procedure is vital for assessing the quality and chemical characteristics of brown coal and lignite samples in both research and industrial settings.
Key Topics
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Scope and Application
The method applies specifically to brown coals and lignites, focusing on the yield of benzene-soluble extracts reported on a dry basis after moisture correction.
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Semi-Automatic Extraction Instrument
The standard describes the apparatus consisting of an extraction chamber with a water jacket, conical flask, condenser, and controller. This automation allows standardized and reproducible testing conditions by controlling temperature and timing during extraction.
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Test Procedure
The sample (~2 g) is placed in an extraction thimble, benzene solvent added, and the instrument undergoes extraction (~180 min), rinsing (~10 min), and evaporation (~50 min) steps automatically. The extracted solvent residue is dried to constant mass to determine the benzene-soluble yield.
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Reagent and Safety
High-purity benzene (analytical reagent grade) is used as a solvent. The standard emphasizes strict safety measures due to benzene’s toxicity and flammability, recommending usage in a fume hood and complete recovery of benzene.
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Calculation of Results
The benzene-soluble extract percentage is calculated based on the mass of dried residue relative to the test sample, with results expressed on a dry basis after moisture adjustment according to ISO 5068-2.
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Precision and Repeatability
ISO 975:2021 defines limits for repeatability and reproducibility. Duplicate tests in the same lab should have differences within 0.3% to 0.5%, while inter-laboratory reproducibility limits vary between 0.5% and 0.7% depending on extract yield.
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Documentation and Reporting
Test reports must include sample identification, reference to ISO 975:2021, test dates, and detailed results with expressions used for clarity.
Applications
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Coal Quality Assessment
The determination of benzene-soluble extracts is crucial in evaluating brown coals and lignites’ chemical composition. This parameter helps identify the presence of volatile organic compounds and extractables impacting coal utilization processes.
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Industrial Process Optimization
Measuring benzene-soluble yields assists industries such as power generation, gasification, and coal processing in optimizing feedstock selection and processing parameters.
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Research and Development
Laboratories engaged in coal chemistry research utilize this standardized method for consistent data generation and comparison across studies focusing on brown coal and lignite properties.
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Environmental Monitoring
Understanding extractable organic matter assists in assessing environmental impact and emission characteristics related to coal combustion.
Related Standards
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ISO 5068-2 – Brown coals and lignites - Determination of moisture content by indirect gravimetric method on the analysis sample. Essential for correcting moisture content in yield calculations.
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ISO 13909-4 – Hard coal and coke - Mechanical sampling - Preparation of test samples, ensuring representative sampling prior to extract determination.
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ISO 18283 – Coal and coke - Manual sampling, providing guidelines for sample collection critical to test accuracy.
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ISO/IEC Directives – Editorial and procedural guidelines for ISO standards maintenance and revision, ensuring consistent document quality and updates.
By adhering to ISO 975:2021, laboratories and industries can ensure precise, reproducible, and standardized measurement of benzene-soluble extracts in brown coals and lignites, enhancing data quality in coal analysis and contributing to improved processing and environmental compliance.