The storage of volatile, renewable energies as one of the unsolved questions of the modern energy economy is the focus of the Clean Circles project. Iron is to be investigated as an energy carrier for a climate-neutral circular economy. Part of the concept is the oxidation of iron particles for energy production. The resulting iron oxide particles are subsequently reduced using energy from renewable resources to obtain pure iron and thus close the cycle. The reduction takes place by dissolving the particles in electrolytic liquids. To investigate the relationship between hydrodynamics and mass transfer during these dissolution processes, a Taylor-Couette test rig will be used. The core of this consists of two concentrically arranged tubes with a fluid-filled gap. By independently rotating the tubes around their longitudinal axis, various flow regimes can be selectively set in the gap.