Overview
SIST EN ISO 6978-1:2005 – Natural gas – Determination of mercury – Part 1: Sampling of mercury by chemisorption on iodine – is a European adopted international standard that defines a method for determining total mercury content in natural gas. Published by CEN, this standard aligns with ISO 6978-1:2003, focusing on sampling at pressures up to 40 MPa by chemisorption on iodine-impregnated silica gel. It serves as a crucial guideline for laboratories and operators involved in quality monitoring and safety of natural gas, providing a standardized approach for quantifying mercury within the range of 0.1 to 5,000 micrograms per cubic meter.
This method is especially relevant where mercury concentrations must be controlled to meet regulatory or commercial requirements and to prevent operational issues during gas processing, liquefaction, or transport.
Key Topics
- Sampling of Mercury in Natural Gas: The standard details a chemisorption technique wherein natural gas is directed through a tube containing iodine-impregnated silica gel, capturing both elemental and organic mercury compounds present in the gas stream.
- Pressure Range: Suitable for gas sampled at pressures up to 40 MPa, enabling use in a variety of operational scenarios, from field collection to high-pressure pipeline sampling.
- Detection Method: Following collection, the mercury is measured by analyzing the absorbance or fluorescence of mercury vapor at a wavelength of 253.7 nm using atomic absorption or atomic fluorescence spectrometry (AAS or AFS).
- Applicability: The method is valid for samples containing less than 20 mg/m³ hydrogen sulfide and no more than 10 g/m³ total liquid hydrocarbon condensate, ensuring reliable results even under challenging pipeline conditions.
- Accuracy and Repeatability: Emphasis is given to equipment calibration, sample handling, and avoidance of contamination or loss, which are essential due to the trace levels of mercury involved.
Applications
SIST EN ISO 6978-1:2005 is widely applied in the following contexts:
- Natural Gas Processing and Transportation: Ensuring compliance with maximum allowable mercury concentrations to avoid equipment corrosion, particularly in cryogenic facilities and pipeline infrastructure.
- Gas Quality Control: Used by laboratories and operators to monitor and verify the effectiveness of mercury removal units and overall gas purity prior to delivery or liquefaction.
- Environmental and Regulatory Compliance: Supports regulatory requirements where mercury emissions or content must be routinely reported, helping operators demonstrate responsible environmental stewardship.
- Research and Development: Standardizes mercury measurement methodologies in sample collection and analysis, providing consistent data for scientific and engineering studies.
By standardizing the sampling and determination process, the standard minimizes risks related to mercury exposure, ensures data consistency, and facilitates international trade and regulatory acceptance of natural gas.
Related Standards
Operators and laboratories using SIST EN ISO 6978-1:2005 often reference the following complementary standards:
- ISO 6978-2: Natural gas - Determination of mercury - Part 2: Sampling of mercury by amalgamation on gold/platinum alloy, providing an alternative sampling method.
- ISO 10715: Guidelines for natural gas sampling practices.
- ISO 14111: Natural gas - Guidelines to traceability in analysis, supporting measurement reliability.
- ISO 6570: Methods for determining potential hydrocarbon liquid content in natural gas.
- ISO 14532: Natural gas - Vocabulary, ensuring uniform terminology.
Adherence to SIST EN ISO 6978-1:2005 assures stakeholders in the natural gas industry that mercury content is determined with accuracy, safety, and in accordance with recognized international best practices.
