Simulation of a Marine Methanol Fuel Tank Fitted With a Nitrogen Blanket

Kurzfassung

According to the IMO interim guidelines for the safety of ships using methanol as fuel, verification of alternative methanol fuel tank pressure relief outlet arrangements requires a demonstration of safety equivalence. In this study, we integrate existing thermodynamic modeling concepts in a module for simulating the thermodynamic behavior of a marine methanol fuel tank fitted with a nitrogen blanket. Based on heat input and methanol evaporation from the tank, the pressure level in the storage over time is calculated. The release valve is governed to maintain a pressure level below 1.3 bar absolute (bara). The necessary release of evaporated methanol-nitrogen mixture in different operating scenarios can be calculated. Due to a lack of experimental data, a simulation validation is not yet feasible. Instead a comparison with a different tank simulation is carried out and demonstrates good agreement. With the developed module it is possible to investigate the methanol tank behavior under different tank designs and causality scenarios, e.g. permanent or non-methanol releases due to damaged pressure relief valves. The results may provide a starting point for subsequent development of additional modules, such as a release module above and under water or a module for assessing the expansion of the explosion area.