(638g) Carbon Dioxide-Induced Liberation of Methane from Laboratory-Formed Methane Hydrates: A Pathway to Economical Carbon Sequestration
AIChE Annual Meeting
Thursday, November 17, 2016 - 10:42am to 11:04am
In this talk, we will describe several laboratory-scale experiments to understand the CH4-CO2 hydrate exchange kinetics. Five hydrate formation-decomposition runs focused on CH4-CO2 exchange, two baselines and three with host sediments, were performed in a 200 mL high-pressure Jerguson cell fitted with two glass windows that allowed visualization of the time-resolved hydrate phenomenon. The data show that the induction time for hydrate appearance was the largest at 96 h with CH4 while with CO2, the time shortened by a factor of four. However, when the secondary gas (CO2 or CH4) was injected into the system containing preformed hydrates, the entering gas formed the hydrate phase instantly (within minutes) and no lag was observed. In a system containing host Ottawa sand (104 g) and artificial seawater (38 mL), the induction period reduced to 24 h. The CO2 hydrate formation in a system that already contained CH4 hydrates was facile and they remained stable, whereas CH4 hydrate formation in a system consisting of CO2 hydrates as hosts were initially stable, but CH4 gas in hydrates quickly exchanged with free CO2 gas to form more stable CO2 hydrates. In all five runs, even though the system was depressurized, left for over a week at room temperature, and flushed with nitrogen gas in between runs, hydrates formed instantaneously, irrespective of the gas used. The â??memory effectâ? was exhibited with either gas, a result in contradiction with that reported previously in the literature. The facile CH4-CO2 exchange observed under temperature-pressure conditions that mimic naturally-occurring CH4 hydrates show promise to develop a commercial carbon sequestration system.