Design and optimization of a steam methane reformer for ship-based hydrogen production on LNG-fueled ship

Abstract

Owing to the severity of global environmental problems caused by climate change, efforts to efficiently use energy are being further strengthened. In this study, to improve energy efficiency, part of the boil-off gas generated from an LNG-fueled ship fuel tank was extracted and converted into hydrogen and then utilized as an auxiliary power source for the ship through a high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC). There are several methods for converting methane to hydrogen; however, steam methane reforming was used in this study. Integrating steam methane reforming into ship-based hydrogen production solves the problem of pure hydrogen storage and transportation as well as addresses environmental concerns by reducing pollutant emissions. Before designing the steam methane reforming reactor, a performance analysis of the reformer was performed using several parameters. The methane conversion rate decreased as the operating pressure of the reformer increased. The methane conversion rate exceeded 90 % when the reformer temperature was above 973 K, the S/C ratio was above 3, and the pressure was below 2 bar. The hydrogen yield was greater than 40 % when the S/C ratio was greater than 4 at the same temperature and pressure. Based on these results, the length of the reformer decreased as its operating temperature increased; at temperatures below 1000 K, the length of the reformer changed significantly as the pressure changed. When the S/C ratio is 3 or 4, the optimal design of the reformer is possible at a temperature range of 1023 K or more at a pressure of 2 bar and 923 K or more at a pressure of 4 bar, and it is reasonable to set the length of the reformer within 2 m considering the limited space on board.