Dynamic process simulation for Polish lignite combustion in a 1 MWth circulating fluidized bed during load changes

Abstract

In this study, a sophisticated dynamic process model of a circulating fluidized bed furnace has been developed. The model describes the 1 MWth test facility, erected at the Technical University of Darmstadt, with a high level of detail including the air supply, the circulating fluidized bed, the flue gas path, the water-cooling system, and the control structures. The developed model was tuned using the experimental data at 82% load. After that, the load is decreased to 63% and the obtained numerical results were compared with the measurement data. Then, the dynamic load increases from 63% to 88% to 100%, followed by dynamic load decreases from 100% to 89% to 68% were simulated. During the load change, the pressure and temperature profiles along the riser were compared with measurement data, showing good agreement. Furthermore, the flue gas concentrations at the outlet of the cyclone agree very well with the values of the test facility. Using the validated model, the transient behaviour of the process variables (pressure, temperature, composition, and mass flow rates) of solids and gas flows during the combustion can be determined. Furthermore, the solid circulating, the inertia, and a variety of parameters that cannot be fully measured in the test facility were numerically obtained.