Modeling of Noncatalytic Gas–Solid Reactions with a Coupled CFD-DEM-USCM Method: A Case Study on Adsorption of Ammonia

This study presents a novel approach for modeling the noncatalytic gas–solid reaction of adsorption of ammonia by metal ammine complexes. A coupled computational fluid dynamics–discrete element method–unreacted shrinking core model (CFD-DEM-USCM) is developed to simulate the behavior of an ammonia storage reactor. The model integrates both mesoscale gas dynamics and microscale particle interactions, allowing for a comprehensive analysis of the adsorption process. Validation of the model against experimental data demonstrated its accuracy in predicting the conversion. It was shown that the effective gas diffusivity of gas inside the particles greatly affects the overall conversion as well as the mean temperature of the particles and gas. Higher diffusion rates enhance mass transfer, resulting in higher temperatures for both particles and gas. The change in particle size during the absorption of ammonia was investigated, and its influence on the reactor void fraction was studied. Inspecting the change in the imposed pressure of the gas at the diffuser and reactor wall temperature indicated that increasing the pressure or decreasing the wall temperature enhances the conversion in the reactor. Estimating the force distribution among particles and between particles and the reactor wall indicated that increasing the particle size with conversion increases both forces. This study provides insight into efficient ammonia storage solutions, contributing to advancements in selective catalytic reduction technology for vehicle emissions control.