Experimental measurement and model prediction of solid-liquid equilibrium for methane-ethane binary system

Abstract

Solid-liquid equilibrium characteristics of light alkane mixtures are of great significance for their applications in chemical engineering and liquified natural gas industry. However, the related researches, especially on their eutectic characteristics and phase change behaviors, are insufficient. Therefore, in the present study, a test rig with a temperature preparing capacity below 70 K is built to measure the freezing point temperatures of different methane-ethane mixture samples. Fifteen experimental points are obtained from the tests in which the freezing temperature varies from 73.88 K to 90.65 K and the molar fraction of methane changes from 0 to 1. Three models are utilized to predict the solid–liquid equilibrium of methane-ethane binary system, and the comparison study shows that SRK model reaches the most accuracy with a relative standard deviation of 1.27%. Based on the data regression of experimental results, the binary interaction coefficient with k12 = -0.073 instead of k12 = 0 is recommended in the prediction of SLE of methane-ethane binary system. Furthermore, a cubic polynomial formula is proposed to corelate k12 variation with temperature, and the modified SRK model with temperature-dependent k12 gives a more accurate prediction on the SLE of methane-ethane binary system with the standard deviation of 0.99%. The predicted eutectic temperature of methane-ethane binary system by the modified model is about 72.71 K and the corresponding methane molar fraction is about 0.668, which are closer to the test data.