Improvement of diesel reformer and heat-up strategy for rapid start-up of solid oxide fuel cell based auxiliary power unit

Abstract

A diesel-driven Auxiliary Power Unit (APU) system based on Metal-Supported Solid Oxide Fuel Cell (MS-SOFC) with high thermal shock resistance was developed. Since the solid oxide fuel cell has high operating temperature, the entire auxiliary power unit system has long start-up time. To overcome the start-up problem, metal supported SOFC was introduced to make faster start-up of the system and more stable diesel reformer operation. In order to secure the fast-starting characteristics of the solid oxide fuel cell-based auxiliary power source, the structure of the diesel reformer was improved, and the heat-up strategy of the fuel cell system was improved. A fuel processor, including a diesel autothermal reformer, a post-reformer, and a desulfurizer, was developed as a block type reactor to simplify the manufacturing process. Structured catalysts for the reformer using monolithic supports were developed to secure high mechanical strength, and the developed structured catalyst showed stable reforming performance despite the instability of fuel supply due to external factors. System components such as heat exchangers and catalytic combustors were designed and tested in consideration of the operating conditions of the fuel cell based auxiliary power unit system. In addition, the starting strategy and system structure of the auxiliary power supply for fuel cells were improved by using an air heater. The fast start-up characteristics of the metal-supported solid oxide fuel cell enabled reducing the start-up time of the auxiliary power unit to less than 90 minutes with improving the stability of the diesel reformer.