Vapor-liquid equilibrium of the nitrogen-argon system at 100 K

Abstract

Mixed-refrigerant cycles (MRC) are state-of-the-art for efficient LNG production. The development of cryogenic mixed-refrigerant cycles (CMRC) at temperatures below 100 K relies on physical property data of cryogenic mixtures such as vapor-liquid equilibria and enthalpies. This data is insufficient for some binary mixtures and unavailable for most multi-component systems. The cryogenic phase equilibria test stand CryoPHAEQTS provides precise physical property data of cryogenic fluid mixtures at temperatures from 15 K to 300K and at pressures up to 150 bar. Contrary to previous apparatus in the literature, CryoPHAEQTS uses cooling of the equilibrium cell by a pulse-tube cryocooler. Temperature is measured by two CERNOX® sensors directly immersed in the liquid/vapor phase. Pressure is measured through a capillary and a differential pressure sensor connected to a secondary system containing three high precision sensors. Up to three occurring phases can be sampled directly from the cell and analyzed by gas chromatography. Measurement uncertainties are ±13mK in temperature, ±1 mbar in pressure and ±1% in composition. Prior to publishing new phase equilibrium data, the test stand is benchmarked against available vapor-liquid equilibrium data of the widely investigated nitrogen-argon system. In this paper, we report on the first measurement results of cryogenic mixtures in CryoPHAEQTS and compare them against the literature data.