Overview
ISO 20729:2017 specifies a method for determining the total sulfur content in natural gas using the ultraviolet (UV) fluorescence method. The standard covers sulfur mass concentrations from 1 mg/m3 to 200 mg/m3; higher concentrations can be measured after dilution with a suitable sulfur‑free solvent. The method oxidizes sulfur species to SO2 in a high‑temperature furnace and measures SO2 fluorescence under UV excitation to quantify total sulfur.
Key SEO keywords: ISO 20729:2017, natural gas total sulfur, ultraviolet fluorescence, UV fluorescence method, sulfur compounds, sulfur concentration.
Key topics and requirements
- Scope and range: Measurement range 1–200 mg/m3 (dilute >200 mg/m3).
- Principle: Combustion/oxidation to SO2 → UV excitation → fluorescence detection by photomultiplier.
- Instruments & conditions:
- High‑temperature furnace at 1000 °C ± 50 °C.
- Quartz cracking tube, dryer (membrane or osmotic) to remove water vapour.
- UV fluorescence detector and data recording system.
- Gases & reagents:
- Carrier gas: argon or helium, purity ≥ 99.99%.
- Oxygen: purity ≥ 99.99%.
- Calibration gases: certified working standards (H2S or COS in methane/nitrogen) with certificates per ISO 6141.
- Calibration:
- At least three concentration points, each injected ≥ three times.
- Linear regression calibration with correlation coefficient ≥ 0.998.
- Sampling & preparation:
- Sampling per ISO 10715; materials must be inert to sulfur compounds.
- Purge lines 30 s to 2 min to avoid sorption effects.
- Precision:
- Repeatability and reproducibility limits specified by concentration ranges (examples):
- Repeatability: 1–6 mg/m3 → 0.8 mg/m3; 100–200 mg/m3 → 7.4 mg/m3.
- Reproducibility: 1–6 mg/m3 → 1.1 mg/m3; 100–200 mg/m3 → 11.6 mg/m3.
- Safety: Warning that many sulfur compounds are extremely toxic - handle with precautions.
Applications and users
Who benefits from ISO 20729:2017:
- Gas laboratories performing routine quality control and compliance testing.
- Pipeline operators and transmission companies monitoring sulfur for corrosion and odorization control.
- Petrochemical and LNG facilities requiring sulfur-speciation or total sulfur monitoring.
- Instrument manufacturers and calibration service providers designing or certifying UV fluorescence analyzers.
- Regulatory bodies and auditors establishing measurement protocols for gas quality and safety.
Practical uses:
- On‑line and off‑line analysis of pipeline and process gas.
- Quality assurance for custody transfer, environmental reporting, and corrosion management.
- Instrument calibration and method validation against certified reference gases.
Related standards
- ISO 6326‑3 (potentiometry for H2S, mercaptans, COS)
- ISO 6326‑5 (Lingener combustion method)
- ISO 19739 (gas chromatography for sulfur compounds)
- ISO 16960 (oxidative microcoulometry for total sulfur)
- ISO 6141, ISO 6142/6144/6145 (reference gas and calibration mixture requirements)
- ISO 10715 (natural gas sampling)
This concise guide helps laboratories and industry professionals understand the scope, technical requirements, and practical value of ISO 20729:2017 for accurate natural gas total sulfur measurement using UV fluorescence.
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