| Popis: |
The design of fixed-bed reactors has gained interest in the light of load-flexible operation. This is due to the expectation that some process feeds will be more volatile in the near future, for example, within the framework of the power-to-methane concept. In this regard, the application of an inert shell onto the catalyst particles has proven advantageous. In this work, a multi-period design optimization of a fixed-bed methanation reactor is performed by employing a heterogeneous reactor model, in which the catalyst particle is divided into an active core and an inert shell. Due to the model's computational demand, it is reduced by using stoichiometric relations at the reactor and catalyst particle scale. Subsequently, dynamic transition simulations between the optimized steady states coming from the multi-period design optimization as well as a reactor start-up and shut-down simulation are carried out, and the results of the full model are compared to those of the reduced model. Our results show that the model size can be reduced significantly by using the stoichiometric relations without loss of accuracy in steady state and negligible accuracy loss in transient scenarios. The optimized fixed-bed methanation reactor can be operated over a wide load range by optimally adjusting the operating variables and the dynamic simulations show smooth transitions between the steady states. |
