The synergistic mechanism of CO2 hydrate formation and blockage in flow loop system: Using a new FBRM experimental setup investigation

• Developed a 30 m high pressure flow loop integrated with FBRM and visualization to simulate deep-sea hydrate conditions. • Pressure acted as the dominant driver, while flow rate and liquid loading exhibited dual regulatory effects on kinetics. • In-situ FBRM analysis revealed a dynamic nucleation-aggregation-deposition coupling mechanism driving flow instability. • A semi-empirical kinetic model accurately predicted induction time (R 2 =0.937) and slurry flow duration (R 2 =0.889). • RSM analysis identified a nonlinear “triple resonance” synergy defining the most dangerous operating boundaries. Formation of gas hydrates poses a major flow assurance challenge for subsea CO 2 pipelines in offshore carbon capture, utilization, and storage (CCUS) systems. In this study, the synergistic effects of pressure, flow rate and liquid loading on the kinetics of CO 2 hydrate formation and slurry flow behavior were comprehensively investigated in a pure water system using a self-designed 30 m high-pressure flow loop installed with on-line Focused Beam Reflectance Measurement (FBRM) and visual observation modules. Results show that pressure is the key thermodynamic driving force. Increasing initial pressure from 2.5 to 4.0 MPa shortened induction time by about 65% and reduced slurry flow duration. The flow rate exhibited a dual influence, a moderate flow rate around 1200 kg/h enhanced mass transfer and promoted nucleation, whereas higher flow rates caused excessive shear, hindering particle agglomeration. A liquid loading of about 50L showed the highest plugging risk due to optimal gas–liquid dispersion and maximum interfacial area. The FBRM analysis indicated that small particles (<100 μm) grew into larger ones (100–1000 μm) and migrated toward the wall, confirming coupling among nucleation, aggregation, and deposition that induced flow instability. A semi-empirical kinetic model was established to accurately predict induction time (R 2 =0.937) and slurry flow duration (R 2 =0.889). Subsequent Response Surface Methodology (RSM) analysis revealed a nonlinear synergistic mechanism, identifying that high pressure combined with moderate flow rate and critical liquid loading (50 L) poses the highest plugging risk. This integrated approach quantitatively evaluates flow risks through combined experimental and model-based analysis.