Study of the Effects of Changes in Gas Composition as Well as Ambient and Gas Temperature on Errors of Indications of Thermal Gas Meters

Abstract

Thermal gas meters represent a promising technology for billing customers for gaseous fuels, however, it is essential to ensure that measurement accuracy is maintained in the long term and in a broad range of operating conditions. The effect of hydrogen addition to natural gas will change the physicochemical properties of the mixture of natural gas and hydrogen. Such a mixture will be supplied through the gas system, to consumers, including households, where the amounts of received gas will be metered. The physicochemical properties of hydrogen, including the specific density or viscosity, differ significantly from those of the natural gas components, such as methane, ethane, propane, nitrogen, etc. Therefore, it is of utmost importance to establish the impact of the changes in the gas composition caused by the addition of hydrogen to natural gas on the metrological properties of household gas meters, including thermal gas meters. Furthermore, since household gas meters can be installed outdoors and, taking into account the fact that household gas meters are good heat exchangers, the influence of ambient and gas temperature on the metrological properties of those meters should be investigated. This article reviews a test bench and a testing method concerning errors of thermal gas meter indicators using air and natural gas, including the type containing hydrogen. The indication errors for thermal gas meters using air, natural gas and natural gas with an addition of 2%, 4%, 5%, 10% and 15% hydrogen were determined and then subjected to metrological analysis. Moreover, the test method and test bench are discussed and the results of tests on the impact of ambient and gas temperatures (‒25 °C and 55 °C, respectively) on the errors of indications of thermal gas meters are presented. Conclusions for distribution system operators in terms of gas meter selection were drawn based on the test results.

Studies of the Impact of Hydrogen on the Stability of Gaseous Mixtures of THT

“…As emphasized by the authors of the abovementioned research [10,11], the produced results are not of a statistical nature, and they do not exhaust the possibilities of further limitations for the permissible safe levels of the hydrogen content of network gas. Forecasts related to further limitations result from the predicted sensitivity of the control and measurement apparatus to hydrogen.…”

“…For years, the Oil and Gas Institute-National Research Institute played a major role in the selection and test of odorants for the gas industry, methods for monitoring gas odorization levels and the ability to improve the efficiency of odorization [27,28]. The present article shows the results of INiG-PIB's initial studies related to the impact of hydrogen in a concentration predicted based on its own earlier research [10,11], on the stability of the THT concentration in gaseous mixtures with the addition of hydrogen, taking into account the conditions of the Polish gas network. The results of the research are a basis for forecasting the impact of hydrogen on the quality of odorization of gas using THT.…”

“…According to the assumptions of the INiG-PIB, the selection of gas compositions tested for the stability of the THT concentration (indirectly: the stability of odorization by means of THT) was based on its previous own experience [9][10][11] concerning the permissible hydrogen content of network gas. On this basis, the mixtures of methane and hydrogen, as well as methane-rich natural gas and hydrogen, used as reference gases for tests were made up of the following compositions:…”

“…At present, there are no legal regulations defining the maximum permissible hydrogen content that can be introduced safely into natural gas networks [8]. Research commenced in this area focuses on determining the most probable and permitted ranges of hydrogen concentrations in the gas network, guaranteeing the safety of the gas system [5,[9][10][11][12][13]. It is necessary, on the one hand, to determine the conditions present in a gas network via which hydrogen can be potentially transported (pressure, temperature) and, on the other hand, assess the impact of hydrogen pumped into the networks in an acceptable amount on the quality of fuel gases, devices burning fuel gases or the operation of control and measurement infrastructures [14].…”

“…The reduction of the hydrogen content of gas to acceptable values results from the necessity to ensure the safety of the gas network, as well as the users of gas. The maximum levels of hydrogen established so far by the INiG-PIB which can be added 'safely' to methane-rich natural gas are [10,11]:…”