In-situ neutron imaging study of NH3 absorption and desorption in SrCl2 within a heat storage prototype reactor

Abstract Strontium chloride octaammine Sr(NH3)8Cl2 offers high volumetric and gravimetric NH3 densities and can store and release heat upon exo-/endothermal absorption and desorption of NH3. Thus, it is a promising material for thermochemical heat storage (THS) applications. In the present work, in-situ neutron imaging was applied to analyze spatio-temporal development of Sr(NH3)8Cl2 powder in a thermochemical heat storage prototype reactor during NH3 absorption and desorption processes. The powder was embedded in a stainless steel honeycomb for the efficient heat transfer during the NH3 desorption process. 2D radiography images were obtained during NH3 ab-/desorption cycles at selected temperatures. The swelling and formation of the porous structure in SrCl2 is monitored during the first cycles. A powder bed expansion of up to 10% upon NH3 absorption was observed. Neutron tomography experiment were also performed to acquire 3D information which revealed the deformation of the honeycomb. This neutron imaging experiment brought crucial information for optimizing the design of efficient and safe THS systems.