H2 production by the steam reforming of excess boil off gas on LNG vessels

Abstract

The gas management system onboard LNG (Liquid Natural Gas) vessels is crucial, since the exploitation of the BOG (Boil Off Gas) produced is of utmost importance for the overall efficiency of the plant. At present, LNG ships with no reliquefaction plant consume the BOG generated in the engines, and the excess is burned in the GCU (Gas Combustion Unit) without any energy use. The need to improve the gas management system, therefore, is evident. This paper proposes hydrogen production through a steam reforming plant, using the excess BOG as raw material and thus avoiding it being burned in the GCU. To test the feasibility of integrating the plant, an actual study of the gas management process on an LNG vessel with 4SDF (4 Stroke Dual Fuel) propulsion and with no reliquefaction plant was conducted, along with a thermodynamic simulation of the reforming plant. With the proposed gas management system, the vessel disposes of different fuels, including H2, a clean fuel with zero ozone-depleting emissions. The availability of H2 on board in areas with strict anti-pollution regulations, such as ECAs (Emission Control Area), means that the vessel may be navigated without using fossil fuels which generate CO2 and SOX emissions. Moreover, while at port, Cold Ironing is avoided, which entails high costs. Thus it is demonstrated that the installation of a reforming plant is both energetically viable and provides greater versatility to the ship. © 2016 Elsevier Ltd