Hydrocarbon dew point (HCDP) is one of the most important quality specifications of natural gas. Measuring and predicting the HCDP accurately are essential for the natural gas industry. However, the comprehensive experimental HCDP curve data are still rare, and knowledge about adopting proper prediction models remains unclear. In view of this, HCDP determination work by use of an improved test system and model evaluation based on more than 1000 dew points data have been done to improve the aforementioned dilemma. HCDP curve data of three gravimetrically prepared synthetic natural gases (SNGs) and one real gas (RG) are determined first. Then, one set of data containing 712 dew points from 28 SNGs and 334 dew points from 14 RGs is used to evaluate the performance of eight different HCDP prediction models including Soave−Redlich−Kwong (SRK), SRK−Twu, Peng−Robinson (PR), Twu−Sim−Tassone (TST), predictive SRK (PSRK), GERG-2008, PSRK, and perturbed-chain statistical associating fluid theory (PC-SAFT) models. Considerable prediction deviation of these models in the high-pressure region (pressure above 6.0 MPa) is observed compared to that in the low-pressure region (under 6.0 MPa), and the reasons for that difference are discussed. Evaluation results reveal that among the eight prediction models, GERG-2008 has the best performance (overall average absolute deviation (AAD): 1.44 °C) for SNGs, and PSRK and SRK−Twu fits the experimental data best for RGs (overall AAD: 2.50 °C). Therefore, GERG-2008 is recommended for HCDP prediction of relatively lean gas, whereas PSRK and SRK−Twu are recommended for calculating the HCDP of relatively heavy natural gases in low-pressure and high-pressure regions, respectively.

Summary Nowadays, the gas chromatography (GC) method is vastly used in natural gas energy measurement but suffers from slow analysis, high capital investment, and high maintenance costs. With the advent of commercial calorimeters using new principles, the calorimeter measurement (CM) method has the ability to overcome the shortcomings of the GC method and is hoping to be an alternative method for energy measurement. To realize accurate energy metering of natural gas by the CM method, the standard GERG‐88 viral equation (denote hereafter as the SGERG‐88 algorithm) is needed to calculate the compressibility factors (Z‐factors). However, unlike the detailed characterization equation in American gas association report No.8 (denote hereafter as the AGA8‐92 DC algorithm) used in the GC method, the SGERG‐88 algorithm is seldom used since it was published in 1991, thus its applicability and accuracy is not so clear in the natural gas industry. In addition, the original SGERG‐88 algorithm coupled hydrogen and carbon monoxide together with a fixed relation, which is not applicable to natural gas blended with hydrogen (NatualHy) that will be widely used anymore. This paper firstly improves the original SGERG‐88 algorithm to make it applicable to NatualHy. Then, taking the Z‐factor calculated by the AGA8‐92 DC as references, the applicability of the improved SGERG‐88 algorithm to different gases is assessed for natural gas and NatualHy measurement. Results and related conclusions or further study suggestions are drawn to prompt the accurate energy measurement of natural gas by the CM method.