Enabling safe and practicable storage of methanol as a ship's fuel by describing and mitigating venting risks

An analytical modelling approach

Master thesis (2022)

Authors

R.R. Kortenhorst Mechanical Engineering

Contributors

K. Visser Ship Design, Production and Operations - Mechanical, Maritime and Materials Engineering (supervisor 1)
P. de Vos Ship Design, Production and Operations - Mechanical, Maritime and Materials Engineering (supervisor 2)
A.W. Vredeveldt (supervisor 2)
K Jansen (coach)
Faculty
Mechanical Engineering
Copyright: © 2022 Rembert Kortenhorst
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Published Date

11-10-2022

Language

English

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Faculty

Mechanical Engineering

Abstract

To reduce the climate change impact of shipping and retain compliance with increasingly strict emission regulations, alternative fuels are required. Methanol is expected to be one of the renewable alternatives. However, it evaporates easily compared to for example Diesel and its vapours are toxic and flammable. Regulations prescribe the use of 10m radius hazardous areas around the vent mast connected to the ship's tank. These areas pose stringent limitations on the use of a ship. In this context, knowledge is lacking on the actual risks induced by possible outflows, let alone on outflow mitigation measures. In this research an analytical thermodynamical model of a ship's methanol fuel tank is developed, it is analysed what appropriate safety measures are and what their effectiveness is.

The thermodynamical phenomena inside a ship's tank are inventoried from literature and on a selection of these a model is derived. With the model, outflow values of methanol mass with and without outflow mitigation measures are simulated for various scenarios and tank sizes. The scenarios are (1) heating during the transition from night to day or (2) due to a fire and (3) the most critical post bunker situation. The latter occurs after the ship's tank is filled for the first time prior to which no methanol vapours are present.

It is found that outflow values correspond to a hazardous area size much smaller than the prescribed 10m except for the fire scenario. However, mitigating the outflow with a PRV and with locating the tank floor in contact with the seawater is found to be very effective. With application of mitigation measures, only the most critical post bunker situation results in a hazardous area of larger than 1m, being 1.17m. Assessment of the model accuracy is limited to the presented scenarios, limiting the model applicability to the ranges in which the parameters are varied within this research.