For the development of the overall model within the framework of Clean Circles (link), scale- and complexity-reduced models must be developed to describe the oxidation and reduction of iron (oxide). A suitable approach is chemical reactor network modelling (CRN), whereby technically relevant systems (reactors) are divided into functional macrozones, also known as compartments, with representative concentrations and temperatures. The individual compartments are represented using ideal reactor models (stirred tank, flow tube), the combination of which in a network can, for example, approximate the residence time or conversion behaviour of the real reactor. Temperature and flow profiles from CFD simulations are used for suitable compartmentalisation. Experimental data of global residence time distributions enable the calibration of the reactor networks to the technical reactor with regard to the residence time behaviour. Reactor network modelling thus greatly simplifies the fluid dynamics compared to CFD simulations and enables a detailed description of the thermochemistry of the system with significantly less computational effort.
In order to be able to use reactor network modelling for the oxidation and reduction of iron (oxides), the models must be extended, calibrated and applied to suitable test cases. The description of heterogeneous reactions between solid particles and the gas phase is carried out using multiphase reactor models. Furthermore, heating rate effects and the transport of particles across compartment boundaries are to be taken into account. With a suitable reactor network, it is possible to analyse the sensitivities and validity ranges of key parameters in detail and consolidate them in the overall model. Thanks to the extensions and the available data, reactor network modelling can be applied on a technical scale.
