Theoretical analysis and experimental results of a 1 kW chem ammonia synthesis reactor for a solar thermochemical energy storage system

Abstract

A closed-loop solar thermochemical energy storage and transport system using the dissociation and synthesis reactions of ammonia has been investigated at the Australian National University (ANU). Work relating to the optimisation of the heat recovery part of the system is reported. Experimental investigation has shown a 1-kW chem laboratory-scale ammonia synthesis reactor to operate in a stable and repeatable manner. A two-dimensional pseudo-homogeneous packed-bed catalytic reactor model previously used successfully for ammonia dissociation reactors is also confirmed to be valid for ammonia synthesis. Experiments were carried out in a closed-loop configuration and involved pressures from 9.3 to 19 MPa with internal peak reactor temperatures of up to 524°C and a constant mass flow of 0.3 g s −1. A simple adjustment of intrinsic rate parameters was required to calibrate the model and reproduce the experimentally observed effects of the variation of reactor wall boundary condition and operating pressure. The investigation revealed that thermal output strongly depends on reactor wall temperature and linearly increases with operating pressure. It is now possible to predict with confidence the performance of future reactor designs. The calibrated model can also be used for detailed theoretical examination of operating strategics designed to maximise thermal and exergetic output from heat recovery reactors.