Dynamic simulation of reactive fluidized bed systems on the example of the Chemical-Looping-Combustion (CLC) process for solid fuels

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Objective of the project is the development of models for the simulation of systems of interconnected fluidized bed reactors. The models should describe the transient system behavior with reasonable accuracy while having a low demand on computing resources. This should allow for an iterative calculation of interconnected systems with recycle streams. The aim of the simulation is to describe the dynamic behavior of the entire system, and to optimize the whole system and especially procedures for load-change, startup and shutdown, respectively. Separate models for reactors with bubbling and circulating fluidized beds will be formulated. As reactions gas/solid and homogeneous gas reactions are taken into account, both with and without change in the gas volume. The chemical looping combustion process for solid fuels shall be used as an example process The models shall finally be validated by measurements in the CLC system of TUHH. One focus of the current project shall be the formulation, implementation and validation of a new semi-empirical model for the circulating fluidized bed. Especially the description of the dynamic behavior of a fluidized bed shall be improved compared to the current assumption of an instantaneous adoption of the fluid mechanics to changes of operating parameters. CFD-calculations with the MP-PIC method shall be used for determining model parameters for geometries and sizes which deviate from those the empirically determined parameters are based on. To facilitate this process for the parameter determination, an interface shall be implemented for the data exchange between the CFD simulator with the module to be developed.In addition an enthalpy balance shall be added to the reactor model. It will take into account the reaction enthalpies as well as heat losses and heat exchange. This balancing of the enthalpy will enable the simulation system to determine also the thermal behavior of interconnected fluidized bed reactors.After implementation into the Dyssol framework the models shall be validated with measurement at the TUHH pilot CLC-plant. Finally a technical CLC plant with a thermal power of 100 MWth will be simulated and analyzed with respect to its dynamic behavior. Of special interest for such analysis are the hot-start, the shutdown and the dynamics of load changes. Beside that simulation of a technical plant following the concept of TUHHs CLC-plant, other process configurations will be simulated and also the Chemical Looping Reforming process to study their dynamic behavior and to proof the flexibility of the simulation system.