Dynamic flowsheet simulation of gas and solids flows in a system of coupled fluidized bed reactors for chemical looping combustion

Abstract

A novel flowsheet simulation environment is applied to simulate a system of interconnected fluidized bed reactors as they are used for the process of chemical looping combustion of solid fuels. Dynamic models of the main process equipment are used in order to capture dynamic behavior of hydrodynamics inside an actual system, which delivers the experimental validation data. The process itself is carried out in a pair of strongly coupled fluidized bed reactors. Furthermore, a cyclone is used for gas-solid separation and two loop seal siphons prevent gas leakages from one reactor to another. The experimental plant operated at Hamburg University of Technology, which is modeled here, comprises a circulating fluidized bed air reactor and a two-stage bubbling bed fuel reactor. Operation of the plant is carried out at ambient condition and so are the simulations.All the mentioned process units are connected into a flowsheet via material streams and the whole process is simulated for 750s of runtime. Within this time, the fluidization velocity of the fuel and the air reactor are changed to mimic effects, which occur during actual operation. The simulation was closely accompanied by experiments at the experimental facility and the results of simulation and experiments were compared. The bed mass, solid circulation and pressure profiles were simulated with good agreement to experimental findings. Dynamic effects were captured by the simulations and the system's response to varying the fluidization speed, that is the change of bed masses, was predicted correctly. Time scales, in which these changes occur, were in the same range for experiments and simulations.