Impact of hydrogen addition, up to 20 % (mol/mol), on the thermodynamic ($p$, $\rho$, $T$) properties of a reference high-calorific natural gas mixture with significant ethane and propane content

TL;DR

This study provides precise density measurements for high-calorific natural gas mixtures with ethane and propane, including hydrogen-enriched variants, to validate equations of state used in natural gas modeling.

Contribution

It offers new experimental density data for ethane/propane-rich natural gas with hydrogen addition, aiding the validation of thermodynamic models.

Findings

Models perform better for methane-dominant mixtures.

Density measurements align with existing equations of state.

Hydrogen addition affects the accuracy of thermodynamic predictions.

Abstract

Injecting hydrogen into the natural gas grid supports gradual decarbonization. To check the accuracy of equations of state for hydrogen-enriched natural gas mixtures, precise density data from well-characterized reference mixtures are essential. In a prior study, we provided experimental measurements for a natural gas constituted mainly of methane and for two derived hydrogen-enriched mixtures. In the present study, being the second and final part of our investigation, density measurements for a high-calorific natural gas with significant ethane and propane content, along with two hydrogen-enriched variants (10 and 20 mol-% hydrogen) are provided. The mixtures are gravimetrically prepared following ISO 6142-1. Density measurements, conducted with a single-sinker densimeter at temperatures from (260-350) K and pressures up to 20 MPa, are compared with three equations of state: AGA8-DC92, GERG-2008, and an improved GERG-2008. Results indicate that all models perform better for methane-dominant mixtures than for those containing heavier hydrocarbons.