Determination of the force transmission error in a single-sinker magnetic suspension densimeter due to the fluid-specific effect and its correction for use with gas mixtures containing oxygen

Abstract

Density measurements from single-sinker magnetic suspension densimeters need to be corrected to compensate for the magnetic effects of the measuring cell materials and the fluid on the coupling transmission system. While the magnetic effect of the densimeter materials can be easily determined, the fluid effect requires the calculation of an apparatus-specific constant, ερ. In this work, the apparatus-specific constant of the single-sinker magnetic suspension densimeter at the University of Valladolid has been determined by using two alternative methods. The first method, which uses density data for the same fluid and conditions and different sinkers, yielded a value of ερ = 4.6•10 -5 . The second method, obtained from measurements with pure oxygen, yielded a value of ερ = 8.822•10 -5 . The second value is considered as more reliable, as the first method presents inherent limitations in this case.

Accurate experimental (p, ρ, T) data of the (CO2 + O2) binary system for the development of models for CCS processes

“…The (p, ρ, T) data were measured using a single-sinker magnetic suspension densimeter (SSMSD) especially designed for density measurements of pure gases and gaseous mixtures. Details of the equipment and measurement procedure have been previously described by Chamorro et al [13], Mondéjar et al [14], and Lozano-Martín et al [15]. The measuring method, originally developed by Brachthäuser et al [16] and improved by Klimeck et al [17], operates on the Archimedes' principle.…”

“…A detailed description of the measurement procedure in SSMSD is presented by Mondéjar et al [14] and Lozano-Martín et al [15] for our equipment; and by McLinden [18] and Richter et al [19] for general aspects. Basically, the density of the fluid can be calculated from Eq.…”

“…The quantities χs0 = 10 -8 m 3 •kg -1 and ρ0 = 1000 kg•m -3 , which appear in equation ( 2), are reducing constants for the mass-based magnetic susceptibility of the fluid χs, the density of the fluid ρfluid, and the density of the sinker ρs. The term ερ, called the 'apparatus-specific constant of the fluid-specific effect', is specific for any particular SSMSD and was calculated for our equipment from density measurements on pure oxygen over a wide range of temperatures and pressures [15]. The obtained value for ερ, as a function of temperature and density, is given by equation ( 5):…”

“…Even though the magnetic susceptibility of pure oxygen may also have a weak dependence with density [23], resulting in a decrease in the magnetic susceptibility with increasing density; this effect is not to be considered here, as it is already taken into account with the density dependence of ερ reflected in equation ( 5) [15].…”

Density Measurements of an Air-Like Binary Mixture over the Temperature Range from 100 K to 298.15 K at Pressures up to 8.0 MPa

“…We would like to expressly point out that the specified small uncertainties for the apparatus-specific constant and the correction model only apply in the present case for the density measurements of an air-like binary mixture. As additional information, we would like to mention here that the apparatus-specific constant, ε ρ , can also be determined accurately by density measurement on pure oxygen, e.g., this was carried out by Lozano-Martín et al [13]. Most densimeters, however, are not designed to measure pure oxygen and do not meet the corresponding safety requirements.…”