Effects of Bubble Size and Density on CO2 Hydrate Slurry Production for Carbon Sequestration

CO2 hydrates are crystalline solids of water and CO2 that form around 0°C and elevated pressures from mixtures of CO2 and water. We report the fastest-even formation rate of carbon dioxide (CO2) hydrate slurry without the use of any conventional chemical promoters or mechanical agitation. This is achieved by sparging CO2 gas as bubbles (size in the order of 100 μm) at high flowrates in a water column in a bubble column reactor. Importantly, the enhancement in the CO2 sequestration rate (based on net gas consumption) is achieved using synthetic oceanwater, which has traditionally slowed hydrate formation. Use of a 2μm-pore sized sparger results in a three orders of magnitude increase in gas-liquid interfacial area compared to our previous studies which used millimetric sized bubbles delivered by a tube into the reactor. Enhanced bubbling continuously renews the gas-water-hydrate interface and improves the heat/mass transfer. We measure CO2 gas consumption rate and hydrate slurry composition (hydrate, CO2 dissolved in water, trapped CO2 gas) as a function of the bubble delivery method, operating pressure, and gas flowrate and duration. Our best results show that hydrate slurries can be formed in 10s of seconds; we report sequestration rate of 2.4 kg h−1 L−1 MPa−1, which is 2X higher than our previous best result. Overall, these results further improve the prospects of large-scale carbon sequestration via ultrafast CO2 hydrate formation.