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Communication Dans Un Congrès Année : 2015

Cryogenic Biogas Upgrading: model and measurements for phase equilibria involving a solid phase.


Cryogenic upgrading of biogas aims to provide energetically efficient process for high purity biomethane production, to be injected in the national gas grid or for vehicle fuel uses. Major components of biogas are methane and carbon dioxide, and for particular type of biogas, called landfill gas, important amount of nitrogen is also present. Cryogenic upgrading processes involve dry ice formation [Clodic and Younes., 2002]., thus accurate predictions of solid-liquid, solid-vapor, and solid-liquid-vapor equilibria are fundamental for a correct design of the heat exchanger surface in order to achieve the desired biomethane purity. Moreover, Liquefied BioGas (LBG) production process is particularly interesting for cryogenic upgrading processes due to the low temperature of the obtained biomethane. It consequently requires an accurate knowledge of carbon dioxide solubility in liquid methane to avoid solid deposition. Finally, knowledge on thermodynamic properties of solid CO2 is needed to simulate the process of upgrading through capture of carbon dioxide as a solid on the fins of a heat exchanger. This work proposes original solid-liquid equilibrium measurements for the binary mixture CO2-CH4 and a thermodynamic model able to represent phase equilibria involving a solid phase for binary (CO2-CH4) and ternary mixture (CO2-CH4-N2), to be used in a heat exchanger simulator with solid formation. Experimental data are obtained with a static analytic experimental method at high pressure (8-15 MPa), conditions at which literature data are missing [Riva et al., 2014]. Measures also allowed to indirectly obtain values of thermodynamic properties of the solid CO2 at temperatures at which direct measures are not available in literature. Thermodynamic model, consisting in a solid phase fugacity expression coupled with a cubic equation of state (Peng Robinson EoS), has been calibrated on solid-liquid-vapor data in order to optimize the representation of phase equilibrium at low temperatures, with particular emphasis on the equilibria involving a solid phase. Comparison of model and data shows a good agreement, so it is possible to conclude that the thermodynamic model is able to predict solid formation condition during the biogas upgrading process. Model and thermodynamic properties are thus used into a simplified heat exchanger dynamic simulator for reproducing solid CO2 capture during the cryogenic process.
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Dates et versions

hal-01158891 , version 1 (02-06-2015)


  • HAL Id : hal-01158891 , version 1


Riva Mauro, Joseph Toubassy, Denis Clodic, Christophe Coquelet, Paolo Stringari. Cryogenic Biogas Upgrading: model and measurements for phase equilibria involving a solid phase.. ECCE10, Sep 2015, NICE, France. ⟨hal-01158891⟩
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