Dew Points, Dielectric Permittivities, and Densities for (Hydrogen + Carbon Dioxide) Mixtures Determined with a Microwave Re-Entrant Cavity Resonator

Abstract

Accurate dew-point, dielectric permittivity, and density measurements of two binary (H 2 + CO 2 ) mixtures with CO 2 mole fractions of 0.94638 and 0.74576 were carried out utilizing an apparatus that employs a microwave re-entrant cavity resonator. Isochoric dew-point measurements were conducted at pressures up to 7.1 MPa and temperatures from T = (249.55 to 296.61) K for the (0.05362 H 2 + 0.94638 CO 2 ) mixture and between T = (251.63 and 280.44) K for the (0.25424 H 2 + 0.74576 CO 2 ) mixture. The combined expanded uncertainty with a level of confidence of approximately 95% (k = 2) in dew-point temperature and pressure ranged between (0.016 and 0.065) K and (0.0041 and 0.0177) MPa, respectively. Within 2.5%, the new data were consistent with the predictions of the GERG-2008 equation of state. Measurements of dielectric permittivity in the single-phase vapor region over the temperature range from (273.06 to 313.18) K at pressures up to 8.2 MPa and in the vicinity of the phase boundary were conducted to determine mixture molar densities by applying a method based on the polarizability mixing rule developed by Harvey and Prausnitz. The microwave-determined mixture densities near 5 MPa agree within 0.33% of reported values measured with a precision twosinker magnetic suspension densimeter; mixture densities near 8 MPa agree within 1.33% of values calculated with the GERG-2008 equation of state.

A microwave sensor for detecting impurity freeze out in liquefied natural gas production

“…In general, the relative permittivity of a sample is a complex quantity that provides direct insight into the composition, density and molecular properties of the mixture's constituents. Many workers have developed and used re-entrant cavity resonators over the last twenty years to study and monitor fluid properties as detailed in references [ [7][8][9][10][11][12][13][14][15][16][17][18][19][20]]. For the purposes of a solids-freeze-out sensor, it is sufficient to simply monitor the effective relative dielectric permittivity of the sample, εmeas, as determined from following ratio…”

“…[21,22] In spatially heterogeneous multi-phase samples, the observed resonant frequency will depend on the dielectric permittivity of each phase, the volume occupied by each phase and the electric field intensities in the volumes occupied by each phase. This dependence of a mode's resonance frequency on the spatial distribution of its electric field has been exploited for the study of vapour-liquid equilibrium by Hopkins et al [18] and the measurement of hydrocarbon dew points, [9,10,13,14,16,19,20,23] particularly in lean natural gas mixtures. [13] The current application represents an extension of those ideas but is significantly more challenging for several reasons including, for example, the much smaller contrast between the dielectric properties of the liquid and solid phases than between gas and liquid phases.…”

Framework for In Situ Measurements of Vapor–Liquid Equilibrium Using a Microwave Cavity Resonator

“…Microwave electromagnetic resonant techniques have proven to be a reliable method for synthetic measurements of phase transitions and fluid quality. First introduced by Rogers et al [15] to investigate phase transitions, microwave re-entrant cavities were developed further by Goodwin et al [16] and May et al [17] to investigate molar polarizability, dielectric permittivity, and density and to detect dew points of mixtures [18][19][20][21][22]. May et al [23] and later on Kandil et al [24] employed microwave cavities for two-phase measurements of liquid volume fraction inside the resonator, introducing a normalized quantity, G n , which relates with the dielectric properties of a two-phase fluid, thus, providing a measurement of quality but not composition.…”