Investigation of the Operating Flexibility of a CFB Furnace - Experimental Measurements and Dynamic Simulation

In this study, various experimental campaigns were carried out using a 1 MWth circulating fluidized bed experimental plant constructed at the Technical University of Darmstadt, Germany to investigate the combustion and co-combustion behaviour of different fuels under steady-state operating and load cycling conditions. Initially, combustion tests were performed with low-calorific Polish lignite and with German lignite as a reference case for co-combustion. In the co-combustion test series, straw pellets and refuse-derived fuel were used as co-fuels with German lignite. In addition, a sophisticated dynamic 1.5-D process simulation model was developed for a 1 MWth circulating fluidized bed test facility. The model created with the software “APROS” accurately represents both the gas/solids and the water/steam sides of the experimental plant. All the components, comprising the riser and the cyclone, the flue gas path with its heat exchangers, the cooling system, and the control circuits, were modelled based on the real pilot plant specification data. The generated dynamic process simulation model was first validated at various steady-state operating points. Subsequently, a dynamic load increase was simulated, which was followed in a second step by a dynamic load decrease. Numerical results, such as the pressure drop profiles and the temperature profiles along the riser, as well as the concentrations of flue gas at the cyclone exit, were compared with the measurements during the load cycling. The comparative studies show that the generated model accurately represents the most relevant parameters throughout the experimental long-term campaigns.