Coal-Fired Plant Furnace Computer Simulations

Coal combustion mathematical model simulations an presented for pilot plant and laboratory furnace tests. The furnace geometries represent full-scale wall-fired and tangentially-fired utility boiler applications. Laboratory furnace studies explore the near burner performance of industrial operation. The mathematical modeling calculations demonstrate the ability of current computer and engineering technologies to perform a priori predictions of local, in situ furnace properties. Comparisons of three closure schemes for fluid turbulence shows the three dimensional k-e model to be significantly better than a constant eddy diffusivity or simple mixing length model but still somewhat inadequate for 3-D furnace applications. Fine scale numerical grid resolution is shown to be neccesary to simulate observed flow patterns in furnace geometries, even for relatively simple furnace configurations. ThE fight coupling between local heat transfer and other physico-chemical processes occurring in coal combustion applications is emphasized. Differences of 50-70% are shown to be obtained if particle-gas convective/conductive heat exchange is ignored or if turbulent fluctuations are not accounted for. Industrial furnace geometries are shown to require advanced numerical treatment to achieve accurate and efficient solutions. An increase in efficiency of two orders of magnitude is shown to be achieved by using multi-grid methods.