Measurements and modeling of vapor liquid equilibria in binary systems of methane + {n-C5, n-C6, or BTEX compounds} at cryogenic temperatures and high pressures

E. May1, M. Kandil1, B. Graham1, K. Marsh1 and S. Huang2

1Centre for Energy, The University of Western Australia, Crawley, Australia
2Chevron Energy Technology Company, Houston, TX, USA

Keywords: methane
property: VLE
material: benzene, methylbenzene, m-xylene

Accurate vapor liquid equilibrium (VLE) data are needed for improved process simulations of LNG plants, especially to avoid the inadvertent carryover of heavy components into the scrub column’s vapor overhead stream which can freeze out in the main cryogenic heat exchanger. In process simulations of the scrub column, the predicted amount of carry over for heavy components is very sensitive to the property package selected, even if they are nominally equivalent. In this presentation experimental pTxy data measured with a custom high-pressure, cryogenic VLE cell are reported for several binary systems of methane + one of the following components: pentane, hexane, benzene, toluene, ethyl-benzene or m-xylene. The data were measured at pressures to 14 MPa over the temperature range 173 to 330 K. Rapid on-line sampling injectors and a carefully calibrated gas chromatograph were used to capture and measure the composition of representative micro-liter samples from the liquid and gas phases in the cell. The measured data are compared with literature data and the predictions of cubic EOS contained in commercial process simulators. The challenges, uncertainties and limitations of the experimental technique are also discussed.

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