AVT - Research - Research project

The project aims at the development of a membrane reactor for steam reforming of second-generation biofuels. The membrane reactor acts as fuel processor for a PEM fuel cell. Membrane reactor and fuel cell constiute an auxiliary power unit for heavy duty trucks.

Auxiliary Power Units (APU) with PEM-fuel cells are especially promising for commercial applications in heavy-duty trucks due to their feasible short time to market. With an electrical power output of 1 - 5 kW, these systems will not replace the primary engines but should guarantee the on-board power supply of the vehicles. Additionally, the idling of the primary engine can be avoided. This fact became even more important, when some Us-federal states prohibited idle operations. Therefor, a large demand to develop these alternative power supply systems and a huge potential for the fuel cell technology can be expected.

The hydrogen required for the operation of the PEM fuel cell can be generated on board by steam reforming of second-generation biofuels. These fuels are particularly suited due to their low content in sulfur and aromatic compounds. In the conventional process, a fuel gas purification system, usually water gas shift reactors (HTS and LTS) and a selective oxidation (SelOx) reactor, is necessary after the steam reforming. With this gas purification it is possible to generate a process gas applicable for fuel cells. Inside the fuel cell the most of the produced hydrogen is converted into electricity and heat. The anode off-gas can be used in a catalytic burner to heat the reformer unit. This recycling of the anode off-gas leads to a complex regulation of the system.

The direct installation of a metal membrane into the reformer unit leads to a reduction of the system volume and system complexity. Hydrogen permeates across the metal membrane with high selectivity. Thus, the chemical gas processing system is replaced. Additionally, the presence of the membrane favorably influences the reaction kinetics inside the reformer and the fuel cell fuelled by very pure hydrogen operates works more efficiently. The reaction temperature in the membrane reformer can be decreased and the system start up and life time can be improved.