Crystallization risk of aromatic compounds in LNG production Part III: The solubility of o-xylene in methane down to cryogenic temperatures

Following a series of works dealing with the experimental determination of the solubility limits of the BTEX components in methane rich-mixtures down to cryogenic temperatures, this work presents new measurements for the solubility of solid o-xylene in solvent methane. The measurements have been obtained using a static-analytic method that allows sampling of the fluid phase at equilibrium with the solid one at temperatures from 242 K down to 123 K and at nominal pressures of 3 and 6 MPa. Despite the importance of BTEX in assessing the risk of crystallization during the liquefaction of natural gas, the solubility of o-xylene in methane rich mixtures was not known in the literature before this work. As a consequence, these original data will give new insights into the solid-fluid equilibrium behaviour of the o-xylene + methane mixture down to LNG temperatures and then provide crucial information for the proper tailoring of the purification units upstream of the liquefaction unit. Measured solid-liquid and solid-vapor equilibria have been compared to the modelling results obtained by coupling a cubic equation of state and a model for the solid phase, and good agreement has been observed.