ISO 2613-1:2023 天然ガスの分析 ― バイオメタンのシリコン含有量 ― Part 1: 原子発光分光法 (AES) による総シリコンの測定 | ページ 2

Foreword

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This document was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee SC 1, Analysis of natural gas, in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 408, Biomethane for use in transport and injection in natural gas pipelines, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

Introduction

This document describes a method for the measurement of the total concentration of silicon in biomethane, biogas and similar gaseous matrices when used in the natural gas grids and when using it as a transport fuel. The method is based on using a liquid impinger to accumulate the silicon from a gas sample, followed by instrumental analysis.

Due to the extensive usage of siloxane compounds, their volatility and great affinity to apolar environments, siloxanes are considered as one of the most important impurities in biogas. They are undesired because of their potential for abrasive SiO₂ formation as combustion product that can damage engines and appliances. Furthermore, some of these compounds present a health risk.

For the purpose of this document, silicon species measured is quoted as total silicon. Silicon measured is from organosilicon species that are trapped from the gas phase in liquid media and derivatized into analytical form of hexafluorosilicate (SiF₆^2-) ions which remain present in solution when analysed.

1 Scope

This document is applicable to the measurement of the total silicon content in gaseous matrices such as biomethane and biogas. Silicon is present in a gas phase contained predominantly in siloxane compounds, trimethylsilane and trimethylsilanol. The analytical form of the silicon measured in liquid phase after conducted sampling and derivatization procedure is soluble hexafluorosilicate anion stable in slightly acidified media. Total silicon is expressed as a mass of silicon in the volume of the analysed gas.

This document is applicable to stated gaseous matrices with silicon concentrations up to 5 mg/m³, and it is prevalently intended for the biomethane matrices with Si mass concentration of 0,1 mg/m³ to 0,5 mg/m³.

With adaptation to ensure appropriate absorption efficiency, it can be used for higher concentrations. The detection limit of the method is estimated as 0,05 mg/m³ based on a gas sample volume of 0,020 m³. All compounds present in the gas phase are volatile at the absorption and derivatization temperature and gaseous organosilicon species are trapped in absorbance media and derivatized into analytical silicon that is measured by this method. The concentration of the silicon is measured in diluted derivatization media using atomic emission spectrometry upon atomisation/ionisation in microwave or inductively coupled plasma.

Unless specified otherwise, all volumes and concentrations refer to standard reference conditions (temperature, 273 K, and pressure, 101,325 kPa).

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 14532 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

Bibliography