Experimental investigation of liquid CO2 discharge from the emergency release system’s coupler of a loading arm

CO2 shipping is the transportation alternative to pipelines for Carbon Dioxide Capture and Storage projects, characterised by a high flexibility to decarbonise scattered or small emitters. Sea carriers discharging liquid cargo in bulk quantities have the necessity for an appropriate emergency release system that can de-risk loading/unloading operations of the marine arm in the event of sudden movement of the ship away from the berthing line. In this work, a cryogenic test facility was designed and commissioned to handle CO2 in proximity of the triple point and at higher pressures (~0.87 MPa – 1.65 MPa, 227 K - 239 K) and investigate liquefied CO2 discharge from the coupler of an emergency release system during an unplanned shutdown. Findings show that separation of the coupler results in a violent discharge of the liquefied CO2 inventory within a mere 0.6 s; significant differences are moreover observed in relation to the initial pressure of the stream. Formation of carbon dioxide solids around the facility and inside the test vessel is found in the tests, with the jetted cloud rapidly dispersing away from the release point whilst entraining air in the process. The implementation of protective barriers appeared to reduce the impact of the release, though the risk of asphyxiation or cryogenic burns to surrounding personnel cannot be totally eliminated given the intensity of the phenomena. Findings from this work are intended to assist in the design of emergency release systems for future CO2 shipping projects whilst also contributing to development of appropriate safety protocols.