Fluidized bed combustion (FBC) of coal gained increasing importance in industrial heat and power station technology during the last decade. with pressurized fluidized bed combustion coal fired combined cycles can be realized with a net thermal efficiency of 45 % compared to an efficiency of 38 % of a pulverized coal fired unit. Even 50 % efficiency can be obtained with hybrid cycles using gas to increase the turbine inlet temperature. This second generation of pressurized fluidized bed systems will drastically reduce the CO2, NOX, N2O, and SO2 emissions. The system will be of the circulating type which is already widely used in atmospheric combustors.
The aim of the present proposal is first to improve the knowledge of the basic fluiddynamic and combustion phenomena. The results of the basic experiments will be used to provide thermo-physical submodels (RWTH, LNETI) which will be integrated in a comprehensive computational fluid dynamic model (FLUENT, RWTH). This fluid dynamic code will be suited to predict the flows of the gas and of the coal/ash mixture within the combustor, the cylones, and the return leg. The combustion process, NOx, N2O, and SO2 production and retention processes, and the heat transfer to the surrounding heat exchanger walls are further topics of interest. It will be a three-dimensional code, so that the influences of secondary and tertiary air, of coal feed, ash recirculation, and other three-dimensional effects can be taken into account. The overall model will be verified and improved (RWTH) with detailed experimental results on velocity, temperature and gas composition from smaller circulating (LNETI) and pressurized (TUD) rigs, with data from a pilot scale unit (RWE) and finally with data from two commercial atmospheric circulating power plants in pforzheim and Saarbrücken (RWTH). The final and experimentally validated computer model will be an advanced tool to be used by industry for scale-up, design, and optimization of pressurized circulating fluidized bed facilities.
Funding SchemeCSC - Cost-sharing contracts
S1 4ES Sheffield
2628 CD Delft