High Purity Hydrogen from Liquid NH3 - Proposal and Evaluation of a Process Chain

Abstract

This study proposes a process chain to gain high purity hydrogen from liquid ammonia. The utilization of the stored hydrogen requires the endothermic decomposition of ammonia2 NH3 ? N2 +3 H2(1)and the subsequent purification of H2. A process model from liquid NH3 to high purity hydrogen was developed. The process model includes the reaction kinetics for the catalytic decomposition of NH3 using a catalyst, such as Ni-Pt/Al2O3, and the necessary purification steps. Based on the simulation, a final process chain is proposed. Finally, heat integration calculations were performed to optimize the energy efficiency of the process. The application of a polyimide membrane system is proposed. The performed calculations show that using membrane separation, a H2 purity of around 97 wt% can be achieved. For a final NH3 content of 99 wt% suitable for PEM fuel cells.