CO2-mineralization and carbonation reactor rig: design and validation for in situ neutron scattering experiments - Engineering and Lessons Learned

CO2 mineralization via aqueous Mg/Ca/Na-carbonate (MgCO3/CaCO3/Na2CO3) formation represents a huge opportunity for the utilization of captured CO2. However, large-scale mineralization is hindered by slow kinetics due to the highly hydrated character of the cations in aqueous solutions (Mg2+ in particular). Reaction conditions can be optimized to accelerate carbonation kinetics, for example by the inclusion of selected additives that promote competitive dehydration of Mg and subsequent agglomeration, nucleation and crystallization. Towards tracking mineralisation and these steps of the reaction, neutron scattering presents unprecedented advantages over traditional techniques for time-resolved in situ measurements. However, a setup providing continuous solution circulation to ensure reactant system homogeneity for industrially relevant CO2-mineralizsation was currently available for use on neutron beamlines. We therefore undertook the design, construction, testing and implementation of such a self-contained reactor rig for use on selected neutron beamlines at the ISIS Neutron and Muon Source (Chilton, UK). The design ensured robust attachment via suspension from the covering flange to stabilize the reactor assembly and all fittings, as well as facilitating precise alignment of the entire reactor and sample (test) cell with respect to beam dimension and direction. The assembly successfully accomplished the principal tasks of providing a continuous flow of the reaction mixture for homogeneity, quantitative control of CO2 flux into the mixture as well as temperature and pressure regulation throughout the reaction and measurements. The design is discussed, with emphasis placed on the reactor including its geometry, components and all technical specifications. Descriptions of the offbeamline bench tests, safety and functionality, as well as the installation on beamlines and trial experimental procedure are provided, together with representative raw neutron scattering results.