**2. Modelling Methods**

#### *2.1. Description of the Process Model*

The deployed Aspen Plus ™ model, shown in Figure 2, is largely adopted from a previous study by Ohlemüller et al. [25]. Here, the chemical reactions occurring in the AR and FR are modelled in two separate reactors, whereas gas-solid and solid-solid separation is achieved through cyclones and separators, respectively. In order to reduce model complexity, the AR and FR were modelled as equilibrium RGIBBS reactors in this work, as this simplification allows for a basic description of the most crucial phenomena required for process control and obviates the necessity of accurate kinetic data. To account for the solid circulation in chemical looping processes, a constant mass stream of solids continuously cycles through the system (OCR-TOAR/OCO-TOFR), after being added to the system after initiation of the simulation (INIT).

**Figure 2.** Flow sheet of the Aspen Plus ™ CLG process model.

For completeness and comprehensibility reasons, all components and streams are briefly described in the following:

