Overview
ISO 11632:1998 specifies an analytical method for determining the mass concentration of sulfur dioxide (SO2) in emissions from stationary sources using ion chromatography. The standard describes an integrated manual sampling and analysis approach: extract a representative flue‑gas sample through a heated probe, absorb SO2 into a hydrogen‑peroxide solution to form sulfate, and quantify sulfate by ion chromatography. The method is intended for routine stack testing and performance characterization of emission control.
Key topics and technical requirements
- Sampling principle: heated glass probe and filter, temperature‑controlled sampling line, and absorption into a peroxide solution to convert SO2 to sulfate.
- Absorption solution: 3% H2O2 in sulfate‑free water (prepare fresh when possible).
- Ion chromatography: anion separator column, conductivity detector (with or without suppressor), and data acquisition (recorder/integrator or computerized system). Use of pre‑column/guard recommended.
- Reagents & standards: sulfate stock standard for calibration; eluents selected per column manufacturer (typical suppressed eluents: NaHCO3/Na2CO3).
- Apparatus: heated probe and filter holder (borosilicate or fused silica), quartz‑fibre particle filter, two absorbers (Drechsel type example), dry‑gas meter, rotameter, leak‑free pump, thermometer and barometer.
- Performance considerations: absorption efficiency, resolution of anion peaks (peak resolution Rs requirement), sampling flow control and accuracy, and laboratory quality control (Annex A provides a quality control programme example).
- Range and adaptability: tested for a defined concentration range with typical 30‑minute sampling; the method can be extended to higher concentrations by dilution or larger absorption volumes and to lower concentrations by longer sampling periods.
- Reporting: procedures for expression of results and test reporting are specified.
Practical applications and users
ISO 11632:1998 is relevant for:
- Environmental testing laboratories performing stack emission measurements for regulatory compliance and reporting.
- Stack testing contractors and consultants conducting field sampling for SO2.
- Industrial operators (power plants, refineries, chemical plants) monitoring process and combustion emissions.
- Manufacturers and developers of ion chromatographs and continuous monitoring systems who need a validated manual method for calibration and comparison.
- Environmental regulators and auditors establishing standardized test methods for stationary source emissions.
Related standards
- ISO 7934 - SO2 manual methods (Thorin/peroxide techniques)
- ISO 7935 - Automated SO2 measuring methods (performance characteristics)
- ISO 10396 - Sampling for automated gas concentration determination
- ISO 6879 - Performance characteristics for air quality methods
- ISO Guide 25 - Laboratory competence (calibration/testing)
Keywords: ISO 11632:1998, sulfur dioxide, SO2, ion chromatography, stationary source emissions, stack testing, absorption solution, sulfate analysis, environmental monitoring.