基于燃烧法的天然气发热量直接测量不确定度评估

Evaluation of direct measurement uncertainty of natural gas calorific value based on combustion method

目的准确测量天然气发热量,实现天然气贸易交接公平准确。方法以定质量式开放火焰燃烧法为原理设计了一种扩展不确定度优于0.3%(k=2)的天然气发热量直接测量实验台;在发热量理论公式的基础上,建立了天然气发热量测量数学模型,综合考虑经济成本,选定了具有适当技术指标的测量设备,以甲烷为气体样品,对天然气发热量直接测量实验台进行了不确定度评估,确定了该实验台研制的可行性,并分析了各不确定度分量的贡献率。结果该实验台测量甲烷发热量的不确定度为0.27%(k=2)。结论满足常用的1.0级及其以下的热值仪的发热量的量值溯源,为实验台搭建奠定了基础。

Objective The aims are to measure the calorific value of natural gas accurately and achieve a fair and accurate natural gas trade.Methods Based on the principle of the fixed-mass open flame combustion method,a direct measurement experimental platform of natural gas calorific value is designed,which has an extended uncertainty better than 0.3%(k=2).Based on the theoretical formula of calorific value,a mathematical model for measuring the calorific value of natural gas is established.Considering the economic cost comprehensively,the measurement equipment with appropriate technical indicators is selected.The uncertainty of the direct measurement experiment platform of natural gas calorific value is evaluated by taking methane as the gas sample,the feasibility of the development of the experimental platform is confirmed,and the contribution rate of each uncertainty component is analyzed.Results The uncertainty of measuring methane calorific value is 0.27%(k=2).Conclusions The uncertainty of measuring methane calorific value meets the value traceability of the calorific value of the commonly used 1.0 level and below calorific value meter,which lays a foundation for the establishment of the experimental platform.