Speeds of sound in biogas mixture CH4+N2+CO2+CO from T=(273,325) and P=(1,12)MPa measured with a spherical resonator

Abstract

The present work has the objective of measure the speeds of sound in a biogas mixture of CH4+N2+CO2+CO, in the pressure range p = [1,12] MPa and temperature range T = [273,325] K, by a spherical acoustical resonator. The results are fitted to the virial acoustic equation of state, obtaining the virial acoustic coefficients, 𝛽𝑎 y 𝛾𝑎, and they are extrapolated to null pressure, determining the adiabatic coefficient as perfect gas, 𝛾𝑝𝑔, and the isobaric and isochoric heat capacities as perfect gas, 𝐶𝑝𝑝𝑔 y 𝐶𝑉𝑝𝑔, respectively. The speeds of sound are acquired with a maximum relative uncertainty of 350𝑝𝑝𝑚 and they are compared with the results predicted by the reference equation of state for methane mixtures (natural gas-like mixtures), the EoS GERG-2008: relative deviations between experimental data and values estimated by this model were lower than 700 ppm at T=325K, below 400 ppm and within the uncertainty of measurement at T=300K, but appreciably higher at isotherm T=273K at the highest pressure range of this work.