Highly Efficient Ammonia Cracking as Hydrogen Supply for De-Centralized and Mobile Applications
Dr. Gunther Kolb
Head of Division Energy, Fraunhofer Institute of Microengineering and Microsystems
Fraunhofer IMM is developing fuel processors for a large variety of fuels. The core technology are catalyst coated plate heat-exchangers, which allow a high degree of heat integration of the reactors, which leads to high system efficiencies. A system under development utilizes ammonia as hydrogen source, which is a highly attractive fuel for a variety of applications among them larger mobile (maritime) but also stationary. Downstream pressure swing adsorption (PSA) is applied to purify the hydrogen before it is fed to a 50 kW fuel cell.
Through heat integration combustion of the PSA off-gas suppies the ammonia cracking reaction and the feed evaporation with energy, which increases the overall system efficiency considerably.
The cracking reactor utilizes self-developed, non-noble metal based catalyst technology for ammonia cracking, which has the highest activity (0.2 mol H2/gcat min at 650 °C reaction temperature). reported in open literature to-date according to the knowledge of the authors. The extremely high activity of the catalyst and the application of catalyst coatings which allow very high catalyst utilization generate high reactor productivity at moderate catalyst cost. A productivity of 0.9 LH2/(s Lreactor) was already achieved in a first generation protoype. This is according to Badakhsh et al. the second highest productivity ever reported in open literature for ammonia cracking reactors.