Performance of conical ammonia dissociation reactors for solar thermochemical energy storage

Solar thermochemical energy storage cannot only have a high energy density but the capability of storing energy at ambient temperature with little heat loss. Recently, lots of research has been done to advance the heat recovery process of an ammonia synthesis system in the context of ammonia-based solar thermochemical energy storage. However, there has not been much enhancement proposed to improve the conversion of the ammonia dissociation reactor, which determines the solar energy absorbed. This paper explores the effects of geometry and configuration on the conversion of ammonia dissociation reactors. A two-dimensional pseudo-homogeneous model has been developed to simulate reaction kinetics and thermodynamics in conical as well as cylindrical ammonia dissociation reactors. The model has been validated by comparing model-predicted and experimentally measured reactor wall temperature profiles and conversions. The effect of the configuration, i.e., cylindrical, diverging and converging, on reactor performance has been investigated. The results show that converging reactors can achieve a higher conversion with a fixed preheating heat exchanger, i.e., a 5.3% increase in the conversion with less than a 1 degrees slope in the tube wall.