Design and thermodynamic analysis of a large-scale ammonia reactor for increased load flexibility

Abstract

The prospect of large-scale production of green ammonia creates strong incentives for developing highly load-flexible Haber–Bosch loops to match hydrogen production by electrolysis and ammonia production, reducing the hydrogen buffer volume.In this work, we create a mechanistic model representing the ammonia synthesis reactor at full load and simplified models representing its periphery and its behavior at part load in UniSim® Design. We optimize the reactor using MATLAB, obtaining the minimum equipment size required to achieve a specified maximum load and operate safely at very low load.The reactor obtained by our novel approach allows to reduce the minimum feasible load by 41–48% over a reactor designed only for full load. We find a moderate pressure reduction combined with an adapted heat integration to be a promising way of maintaining safe operating conditions during part-load operation, while changing the gas composition in the synthesis loop cannot reduce the minimum load.