CO2 removal from a CO2-CH4 gas mixture by hydrate formation: evaluation of additives and operating conditions
Résumé
This paper presents an experimental study of CO2 capture by means of gas hydrate crystallization, which seems to be a promising alternative to conventional processes for removal of CO2 from natural gas streams, especially when the CO2 is to be reinjected in a geological formation. The gas phase used here is a mixture of 25 mol% CH4 and 75 mol% CO2. Different mixtures of kinetic and thermodynamic additives (sodium dodecyl sulfate, SDS, and tetrahydrofuran, THF) dissolved in water are used with the aim to accelerate the hydrate formation and to enhance CO2 capture selectivity. The experiments are performed in a batch reactor under quiescent conditions. The composition of the gas phase is monitored by gas chromatography in the course of the experiments. The influence of THF concentration and operating conditions (particularly the load pressure) has been evaluated on the gas mixture solubility, the hydrate formation kinetics and the CO2 capture selectivity. The results show that THF (used in combination with SDS) plays a key role in the hydrate formation process and does not influence the CO2 capture selectivity, at least in the range of concentrations studied. It is also shown that decreasing the gas loading pressure improves the selectivity of CO2 capture.
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