Comparative study on uncertainty evaluation methods for natural gas composition analysis

With the promotion of natural gas energy measurement methods by governments, enterprises, and users, research and preparatory work related to natural gas energy measurement have garnered widespread attention. Among these, the uncertainty of natural gas energy value is a crucial indicator for assessing the accuracy of measurement data under the energy measurement model. The uncertainty in natural gas composition analysis affects both the volumetric quantity and the unit calorific value in the calculation of natural gas energy value, playing a significant role in the uncertainty evaluation process. Within China’s natural gas energy measurement standard system, two standards—GB/T 35186-2017 and GB/T 27894.2-2020—specify different evaluation methods for composition analysis uncertainty. This paper compares the composition analysis uncertainty evaluation methods outlined in these two standards. Using analysis data from five measurement stations as examples, the results calculated using both methods indicate that the method in GB/T 35186-2017 tends to yield smaller uncertainty values because it does not account for uncertainty components such as instrument linearity error correction, normalization methods, and composition content calculation. To address these shortcomings, it is recommended that the standard be revised to adopt the composition analysis uncertainty evaluation method specified in GB/T 27894.2-2020. This adjustment would help compensate for the deficiencies in the current approach.