Speed of sound measurements for a CO₂ rich mixture

Knowledge of the thermophysical properties of a CO₂-rich natural gas is very important for precise design and optimization of production, processing, storage and transportation. Although different experimental techniques are available to measure thermophysical properties of fluids, for some of these properties like isobaric heat capacity and Joule-Thomson coefficient direct measurement at high pressure is difficult. Therefore, it is preferred to use indirect methods to determine these properties employing other measured properties. The speed of sound in the fluids is one of the most useful thermodynamic properties that can be used to determine other thermodynamic properties like density, isobaric heat capacity and Joule-Thompson coefficient. Moreover, in comparison with other thermodynamic properties, the speed of sound can be measured with high accuracy in the laboratory, which makes it very special. The available data in the open literature on the measurement of sound velocity in CO₂-CH₄ mixtures with a high concentration of CO₂, are limited to the studies conducted by Yo unglove [1] and Estela-Uribe [2] at pressure ranges up 11 MPa and 17 MPa, respectively. The molar composition of CO₂ in the samples used for these studies were 5%, 15%, 20% and 30%. Therefore, experimental measurement of the speed of sound in binary and multicomponenet CO₂-CH₄ mixtures with a higher concentration of CO₂ and at a wider range of pressure is required to fill the gap in the literature data. The key objective of this work is to measure the speed of sound in a multicomponent CO₂-rich natural gas mixture (~70 mol% CO₂ and ~26 mol% CH₄) at pressure range up to 60 MPa and for five isotherms between 323 K to 416 K.