Determining the physical-chemical parametere of fuel mixtures of natural gas with hydrogen in gas networks

The object of this study is a gas mixture of natural gas and hydrogen. The physical and chemical parameters of fuel mixtures of natural gas with hydrogen have been investigated with the aim of further regulating the hydrogen content in the gas transmission system in accordance with the state standards of Ukraine and the European Union. The task addressed was the safe use of green hydrogen in a mixture with natural gas. The permissible hydrogen content in municipal network gas was established at 7 mol %, which would allow efficient and safe use of existing gas transmission systems. Currently, a 4 % increase in pressure is recommended for low-pressure networks. This is because the calorific value of natural gas is regulated by the Code of Gas Transmission and Distribution Systems and must be within certain limits, and compliance with this particular hydrogen content in natural gas allows this indicator to be kept within the normal range. The 4 % increase in pressure is due to the preservation of the thermal power of gas burners when one gaseous fuel is replaced by another. The content of the mixture of combustible gases at the lower and upper flash points was analyzed. It was found that at 7 % hydrogen content, the flash point range is 5.07–16.75 vol %, which is within the permissible range of 5–15 vol %. With an increase in the hydrogen content of the gas, an explosion may occur in a wider range of concentrations and require additional safety measures. The defined hydrogen limit does not affect the explosiveness of network gas and ensures the safety of its use since the lower concentration limit of flammability (in terms of methane) in a mixture with air in volume percentage is 4.4, and the upper limit is 17.0 vol % according to Annex 2 of the technical regulations