OCR Text |
Show Fuel nitrogen release: Rate of Thermal NO Formation: Reaction Rates Rates for Fuel NO: NO-Char Reduction Rate: Here the bar (-) denotes the averaging of reaction rates over the PDF according to Eq. 11. Three-Dimensional Fluidized Bed Freeboard Model To perform the combustion and NO analyses, a three-dimensional slab model of the fluidized bed freeboard has been developed. This model accounts for all of the important features of the freeboard while remaining computationally efficient. With this model gas and particle flows, heat transfer, combustion and pollutant concentrations can be predicted. Comparisons with experimental data can then be made to evaluate the model. The 6x6 AFBC is shown in Figure 1. It consists of a bed of limestone and coal approximately 4 feet in height. The freeboard and convection bank are above the bed. Coal, air and limestone enter the combustor at the bottom through bubble caps and a distributor plate. The coal devolatilizes and most of it burns in the bed. The unburned char escapes from the bed into the freeboard where additional char oxidation occurs. Very fine (< 28 mesh) particles consisting of coal, ash, char and limestone leave the combustor. At the furnace exit, « 0 - ? W N S f ^ (25) *1 " h ^ t021/2 Veq •*P<-VRT) (26) *2 " pm *2 YHCN \ b Mmb exP( "V*1' (27» *3 " pm A3 YHCN YN0 \ ^-hW (28» *4 " A4 "m *E PN0 "Pl-V*" (29) -14- |