Phase behaviour of methane in methanol, ethanol and aqueous solutions

One of the main flow assurance challenges that faces the petroleum industry is hydrate formation, thus it is essential to understand and model the distribution of hydrate inhibitors for the design of efficient and economical gas transportation and processing operations.
Solubility data are an essential element of developing binary interaction parameters for equations of state. The solubility of methane in methanol at 273.15 K and 1.1 to 47 MPa, and methane in ethanol at five different isotherms between 238.15 to 298.15 K and 0.3 to 41.7 MPa was measured. The results showed an average repeatability of 2.5% between the measured points. To fill the significant gap in the open literature data the solubility of methane in 70 and 50 wt% methanol and ethanol solutions at 273.15 to 298.15 K and 0.46 to 44 MPa were measured. The results showed that the addition of water significantly reduces the solubility in methanol and ethanol. Methanol and ethanol are two of the most commonly used gas hydrate inhibitors in the petroleum industry. The results from this work and literature were used to optimize the interaction parameters of the CPA-SRK72 equation of state. The model calculations using a single variable binary interaction parameter was able to reproduce the new experimental results with a significant increase in accuracy. Hydrate dissociation points of systems containing methanol and ethanol were further used to test the model.