An Experimental Model of Anhydrous Ammonia Dispersion and Safety During Maritime Operations

Anhydrous ammonia plays an ever-expanding role in maritime operations, from its traditional use in marine refrigeration, to the more modern applications that utilize ammonia as a hydrogen carrier or even as fuel in marine propulsion. The expanding use poses an increased risk of leaks and dispersion into the ocean, with potentially devastating consequences for marine life as well as vessel crew members. In order to study the dispersion of anhydrous ammonia in ocean water, we created an experimental setup which models a catastrophic leak scenario from a bunkering pipe at a 100:1 scale. Pressure and temperature of anhydrous ammonia at the injection point are carefully controlled by using a Dewar system upstream of the leak, while the liquid flowrate conforms to full Froude similarity between scales. An ocean analogue is prepared using appropriate buffers, and two pH meters are located under the surface of the water in order to provide real-time nitrogen concentration in these locations. Two electrostatic probes are located above the water surface in order to quantify the real-time concentration of ammonia vapor. One Long-Wave Infrared camera is used to quantify the temperature of the ocean water, and three visible-light cameras are used to determine anhydrous ammonia dispersion, vaporization, and flow above the water surface. The experimental study alongside supplementary CFD modelling create a unique dataset that improves our understanding of ammonia dispersion under real-life marine conditions and supports the development of safer ammonia bunkering protocols and regulatory guidelines.