Comparative study of vapor pressure requirements for rule-based design of IMO Type C tanks for LCO2: Guidelines for optimizing pressure conditions

The safe and efficient design of liquefied carbon dioxide (LCO₂) storage tanks is essential for carbon capture, utilization, and storage (CCUS), particularly in maritime transport. IMO Type C pressure vessels are widely used, with minimum design vapor pressure determined by rule-based criteria. These regulations, based on fracture mechanics principles, prevent crack propagation-induced leaks. However, discrepancies between regulatory and operational pressures increase design complexity and iterative modifications. This study presents a thermodynamic framework to assess the gap between rule-based and actual vapor pressures and identifies volume-dependent implications for pressure control and insulation design. Simulations for 1000–5000 m³ tanks show that small tanks (1000–2000 m³) may exceed regulatory pressure limits, requiring enhanced insulation or pressure control. In contrast, large tanks (3000–5000 m³) are governed by conservative rule-based limits, suggesting potential for operational adjustments. The results offer an early-stage design guide balancing efficiency and regulatory compliance, supporting safe, economical marine LCO₂ transport system development.