(613f) Chemical Looping Based Hydrogen Production from Ammonia: System Analysis and Experiments of a Two Reactor and a Three Reactor System

Authors: 
Kathe, M., The Ohio State University
Baser, D., The Ohio State University
Clelland, K., The Ohio State University
Fan, L. S., The Ohio State University
Tong, A., The Ohio State University
Hydrogen (H2) is a promising carbon neutral liquid fuel with a high specific energy of 39.8 kWh/kg (HHV). The market penetration of H2 is limited by the high transportation costs associated with its low energy density of 0.8kWh/L ( by comparison gasoline is 8.76 kWh/L) . A potential solution to reduce transportation costs for H2 is to use ammonia (energy density: 4.25 kW/L). Ammonia (NH3) is proposed to be an alternative H2 carrier, due to its lower transportation costs and it is widely produced on an industrial scale using Haber-Bosch chemistry. From an end-user perspective, if ammonia is used as a H2 carrier and if H2 is still used as the primary energy source, there exists a technological need to convert NH3 back to H2 in an efficient way.

OSU has proposed a thermochemical solids looping based based NH3 to H2 (ATH) process that can operate at high thermal and H2 production efficiencies. The ATH system can be operated as a two reactor system or a three reactor system, wherein the first the reducer reactor utilizes an intrinsic O2 gradient driven by the reduction potential of NH3 and a metal oxide Fe2O3/Fe3O4) to efficiently crack NH3 to a mixture of N2, H2 and H2O. The reduced metal-oxide from the reducer reactor is re-oxidized in a second reactor oxidizer using H2O as the oxygen source.

This presentation will initially compare and contrast the two reactor ATH system to the three reactor ATH system. Specifics of the thermodynamic rationale for optimizing the H2 production from NH3 using these configurations, while minimizing the operating temperature will be presented. The study uses guidance from the thermodynamic simulations to design reaction-engineering experiments in a thermo-gravimetric analyzer and a fixed bed system for generating proof of concept data. A techno-economic analysis model based on reaction engineering parameters is constructed and analyzed using sensitivity studies that provide insights into further process development will also be presented.