9:15 AM - 9:30 AM
[HSC04-02] Examining the effectiveness of the use of nanobubbles for universally-applicable CO2 geological storage
Keywords:CCS, Ultrafine bubbles, Nanobubbles, Porosity
Despite a growing demand for advancing CO2 capture and storage (CCS), there are still various factors to be solved for the practical application of CCS, including locations, environmental conditions, and cost. Here, this study examined the possibility of CCS using low-cost and environmentally-friendly nanobubbles (NBs), by investigating the stability and gas solubility of CO2-NBs. We examined the effectiveness of CO2-NBs by injecting CO2-NBs containing water into the tested porous sand media with different porosities and measuring the temporal change of liquid-phase CO2 concentration within the pore water.
We prepared several different porous sand media with changing porosities (48%, 50%, 55%, and 60%) and median grain sizes of sand particles. The CO2-NBs-containing water was prepared using an ultra-fine-pore & rotary hybrid system of NB generator and pure water at an injection pressure of 0.2 MPa and generated CO2-NBs for only 20 minutes. We measured the dissolved CO2 concentrations within the pore water after 1, 7, 14, 28, and 42 days of CO2-NBs generation.
The dissolved CO2 concentration measured immediately after generating CO2-NBs containing water was 1030±210 ppm. The concentration agreed well with the concentration theoretically estimated from the bubble diameter and number density of generated CO2-NBs. In general, the dissolved CO2 concentration within pore water decreased with time during the test period of 42 days. However, the reduction rates of CO2 concentration were lower when the porosity was higher. Also, CO2 concentration was as high as about 200 ppm even after six weeks, highlighting a remarkable result considering that our experiment was done in open-air conditions. We suggest that the bulk NBs contribute to increasing the dissolved CO2 concentrations in the earlier stage and that the surface NBs favored in being pinned on the particle surfaces play a role in keeping at some higher concentration in the later phase, perhaps later than about a week. These findings may indicate the effectiveness of NBs for universally-applicable CCS, even in shallow subsurfaces.
We prepared several different porous sand media with changing porosities (48%, 50%, 55%, and 60%) and median grain sizes of sand particles. The CO2-NBs-containing water was prepared using an ultra-fine-pore & rotary hybrid system of NB generator and pure water at an injection pressure of 0.2 MPa and generated CO2-NBs for only 20 minutes. We measured the dissolved CO2 concentrations within the pore water after 1, 7, 14, 28, and 42 days of CO2-NBs generation.
The dissolved CO2 concentration measured immediately after generating CO2-NBs containing water was 1030±210 ppm. The concentration agreed well with the concentration theoretically estimated from the bubble diameter and number density of generated CO2-NBs. In general, the dissolved CO2 concentration within pore water decreased with time during the test period of 42 days. However, the reduction rates of CO2 concentration were lower when the porosity was higher. Also, CO2 concentration was as high as about 200 ppm even after six weeks, highlighting a remarkable result considering that our experiment was done in open-air conditions. We suggest that the bulk NBs contribute to increasing the dissolved CO2 concentrations in the earlier stage and that the surface NBs favored in being pinned on the particle surfaces play a role in keeping at some higher concentration in the later phase, perhaps later than about a week. These findings may indicate the effectiveness of NBs for universally-applicable CCS, even in shallow subsurfaces.