Optimization of pressure and flow rate for CO2 microbubble generation using porous ceramic membrane: Insights for CO₂ geological storage

CO 2 microbubbles show significant potential in carbon capture and storage (CCS) through enhancing CO 2 dissolution and improving the residual trapping mechanism. To take full advantage of microbubbles, maximizing their generation by selecting the optimal operational conditions, including injection pressure and flow rate, is essential. In this study, we examined a wide range of experimental conditions to quantitatively evaluate the potential of a porous ceramic membrane for producing CO 2 microbubbles in a chemical-free manner. In particular, the effects of injection pressure (5.0-10.0 MPa) and CO 2 flow rate (0.25-5 mL/min) on mean bubble diameter ( D MB ¯ ) and microbubble yield efficiency ( Y MB ) were systematically investigated through image analysis technique. Results suggest that increasing injection pressures significantly enhances the chance of microbubble generation. At pressures ≥8.33 MPa and all examined flow rates, 98-100% of bubbles were within the microbubble range (10-100 µm), compared to only 12% at 5.0 MPa and 5.0 mL/min. Also, D MB ¯ decreased from 106 µm at 5.0 MPa to 17 µm at 10.0 MPa, at a flow rate of 0.25 mL/min. In contrast, increasing the injection flow rate produced larger bubbles; however, its effect diminished at higher pressures, where Y MB remained near 100%, regardless of flow rate. Furthermore, the optimized condition was determined to be at a pressure of 10.00 MPa and a flow rate of 0.5 mL/min. The developed framework in this research eliminates the need for chemical materials, e.g., surfactants or polymers, leading to a cost-effective and environmentally friendly CO 2 microbubbles generation, which can potentially be applicable in CCS, EOR, and various other industries. • CO 2 microbubbles were generated using a porous ceramic membrane, without additives. • Injection pressure and flow rate strongly controlled microbubble characteristics. • Near-complete microbubble yield was achieved under optimized operating conditions.