Optimal design of different reforming processes of the actual composition of bio-oil for high-temperature PEMFC systems

Abstract

Hydrogen production from bio-oil, a by-product of the pyrolysis of palm empty fruit bunches, using different reforming processes, i.e., steam reforming (SR), partial oxidation (POX) and autothermal reforming (ATR), is theoretically investigated using the actual composition of bio-oil. The effect of the reaction temperature, steam to carbon (S/C) ratio and oxygen to carbon (O/C) ratio on the hydrogen production and coke formation of the reformers is analysed. Favourable operating conditions to inhibit carbon formation, to produce low CO concentrations and to achieve high hydrogen yields for the hydrogen production processes coupled with a high-temperature water-gas shift reactor (HT-WGSR) in a high-temperature proton exchange membrane fuel cell (PEMFC) system is also investigated. The results show that an S/C ratio above two is preferred for the bio-oil steam reformer to keep the CO concentration below the maximum allowable limit of the high-temperature PEMFC. However, the CO concentration in the product gas from an HT-WGSR integrated with an autothermal reformer and a partial oxidation reactor is lower than the 5% limit at all temperatures (300–1000 °C), S/C ratios (1–2) and O/C ratios (0.3–1) considered. The efficiency of different bio-oil reforming processes integrated with high-temperature PEMFC systems is studied. The highest system efficiency is achieved from the integrated system consisting of a bio-oil steam reformer, an HT-WGSR and a high-temperature PEMFC with heat integration.