Carbon Dioxide Hydrate Formation From a Binary Mixture of Carbon Dioxide and Nitrogen

Carbon dioxide (CO2) hydrates are crystalline solids of water and CO2 that form around 0 °C and at moderate pressures (~ 400 psi) from mixtures of CO2 and water. Hydrates offer an avenue for large-scale, long-term carbon sequestration. Recent work from this group reported ultrafast formation of CO2 hydrates in a bubble column reactor using magnesium as a passive nucleation promoter. While that study utilized pure CO2, we presently study hydrate formation from a binary mixture of CO2 (90% by volume) and nitrogen (10% by volume). Additionally, we study the impact of bubble delivery via a micrometer-sized pore sparger and contrast it with bubble delivery using a straight tube. We report sequestration rates as high as 1163 g h−1 L−1 MPa−1, which is within 10% of the fastest reported rates (using pure CO2). Significantly, this rate is achieved using synthetic ocean water, which itself has an inhibiting effect on hydrate formation. We find that use of the sparger increases the density of hydrates formed and the conversion of CO2 into hydrate. Overall, the high formation rates achieved with impure CO2 vastly improve the techno-economics of CO2 hydrates-based sequestration since purification of CO2 is energy and cost intensive.