天然气计量中物性计算方法适用性探讨

Research on the adaptability of physical property calculation method in natural gas measurement

针对目前天然气体积计量中面临的物性参数计算问题,在GB/T 17747.2-2011和ISO 20765-2:2015的基础上,采用Matlab软件建立AGA8-92DC和GERG-2008状态方程天然气物性求解程序,以相对偏差(RD)和平均相对偏差(ARD)为评价指标,评估了两种方程在计算不同种类天然气物性上的准确性。结果表明,在管输天然气压力0~10 MPa、温度280~320 K的范围内,AGA8-92DC和GERG-2008状态方程的计算结果准确度一致,ARD均为0.03%;对于含重烃天然气,压力小于30 MPa、温度250~500 K的范围内,GERG-2008状态方程的计算表现更优,压力大于30 MPa,部分温度范围内AGA8-92DC状态方程的计算表现更优;AGA8-92DC状态方程和GERG-2008状态方程分别在计算高含硫天然气和液化天然气物性上具有优越性,但当含硫量和重烃含量较大时,偏差会显著增大。研究结果可为天然气计量工作的持续推进提供实际参考。

At present,based on GB/T 17747.2—2011 and ISO 20765-2:2015,faced with the cal-culation problem of physical property in the volumetric measurement of natural gas,the Matlab soft-ware is used to establish the natural gas physical property solving programs for AGA8-92DC and GERG-2008 equation of state.Using relative deviation(RD)and average relative deviation(ARD)as evaluation indexes,the accuracy of the two equations in calculating the physical properties of differ-ent kinds of natural gas is evaluated.The results show that when the pressure of pipeline natural gas ranges from 0 MPa to 10 MPa and the temperature ranges from 280 K to 320 K,the accuracy of AGA8-92DC and GERG-2008 equation of state is consistent and ARD is 0.03%.For natural gas con-taining heavy hydrocarbon,the GERG-2008 equation of state is performed better when the pressure is less than 30 MPa and the temperature is ranges from 250 K to 500 K while the calculation performance of AGA8-92DC equation is better when the pressure is greater than 30 MPa and some temperature ranges.In addition,the AGA8-92DC equation of state and GERG-2008 equation of state have ad-vantages in calculating the physical properties of high sulfur natural gas and liquefied natural gas respec-tively.However,the deviation will be increased significantly when the sulfur content and heavy hydro-carbon content are large.Even more to the point,the research results can be provided practical refer-ence for the continuous development of natural gas measurement.