Experimental investigation of cryogenic leaks during transferring operations

Abstract

Bunkering of alternative marine fuels such as LNG, methanol, ammonia, and hydrogen presents a high risk of leakage due to temporary connections during transfers. Gas clouds from leakages can result in hazardous events including fires, explosion, and sometimes toxic plumes. Release of fuels which are normally stored under cryogenic liquid conditions, results in complex multiphase phenomena including forming of mixture of droplet-vapor near field. Accumulation of droplets on the ground is normally referred to as rainout which effectively reduce the mass of vapor release into the atmosphere. Understanding the rainout behaviour is imperative in quantitative risk assessment for bunkering leakage to ensure safety and reliability of the bunkering process. In this work we perform field experiment of releasing cryogenic liquids to characterize rainout phenomena and understand dispersion characteristics under realistic wind conditions. The experiment adopts alternative cryogenic gases (namely Argon and Nitrogen) to characterize mass of liquid rainout as well as dispersion behaviour. The experiment focuses on measurements of mass of liquid rainout for liquefied Argon and liquefied Nitrogen in both vertical and horizontal releases and concentration of gas dispersion for liquefied Argon release. The transient leak flow rate and pressure during the leak, as well as the site conditions, including wind velocities, humidity, temperature, and solar radiation are measured to provide detailed information for subsequent validation of numerical models. Through the experiment, it is found that it is likely that the release of cryogenic liquids is multiphase with rainout, especially in the presence of obstacles or in confined space. Experiment results show that the vertical leak for liquefied Nitrogen rainout collection ratio ranges from 15% to 46% of the released cryogenic liquid, and for liquefied Argon 28–56% of released liquid is collected as rainout based on the specified release conditions with different release diameters, heights and pressures. No rainout was collected in horizontal releases of Argon. Argon concentrations measured around the dispersion area for vertical leak range from 0 to 25%, while for horizontal leak range from 0 to 15%. Results from the field experiment shed lights on better understanding of multiphase cryogenic releases and provides valuable information for validation of dispersion models.