The effect of hydrogen on the physical properties of natural gas and the metrological characteristics of its metering systems

Abstract

Given the promise of the concept of using a mixture of hydrogen and natural gas as an energy source, studies were conducted in the following areas:
 
 determination of the effect of hydrogen impurities on the physical properties of natural gas;
 study of the effect of adding hydrogen to natural gas on the metrological characteristics of its consumption metering systems.
 
 To solve these problems, the following was carried out:
 
 determination of the dependence of the physical parameters of natural gas on the percentage of hydrogen in its composition:
 determination of the permissible fraction (permissible concentration) of hydrogen in natural gas in modern gas transmission and gas consuming systems.
 study of the effect of hydrogen additions on the metrological characteristics of measuring instruments and gas commercial metering systems.
 
 To conduct objective research and modeling, natural gas samples having different component composition were prepared. An analysis of the physical properties of these gases was carried out — their physical parameters were calculated: adiabatic index and sound velocity, density, compressibility factor, higher calorific value and Wobbe number. Based on these samples, modeling was performed — the physical parameters of the gases were calculated by adding hydrogen at different concentrations (from 2 to 23 %).
 Based on the research results, the following conclusions are made:
 
 When hydrogen is added to natural gas in an amount of from 2 to 10 %, the physical parameters of the resulting mixture change slightly (within acceptable limits), therefore, the addition of hydrogen to natural gas in an amount of up to 10 % allows the use of existing gas transmission and gas-consuming systems without any reconstructions, improvements, changes in algorithms for calculating the physical parameters of the gas mixture and calculating (volume) volumetric flow for commercial accounting. The impact on gas meters of consumers will be within the acceptable ranges of accuracy and repeatability and, therefore, will not require the cost of updating the meters.
 The addition of up to 25 % hydrogen by volume does not require a radical new technology of burners and gas transmission systems. Safety will not be compromised by adding 25 % hydrogen by volume to the natural gas network. Changes in the physical properties in the gas mixture have a number of disadvantages, but, in the aggregate, they do not pose any additional safety risk.
 The addition of hydrogen in a volume of more than 25 %, as well as the use of the mixture at high pressures, requires additional research and the development of new algorithms.