| OCR Text |
Show 3 where, A is the frequency factor, E is the activation energy, and subscripts VM, Nand R are volatile matter evolution, NOx formation and NOx reduction, respectively. [NOx], [N], [02] and [VM] are the mass concentrations in unit of mol/m3 of NOx, N compound, 02 and volatile matter, respectively. Ts is the temperature of coal particle, and Tg is the surrounding gas temperature. For the rate of volatile evolution, a single reaction model given by Equation (1) is assumed. Further, the temperature of coal particle (Ts) in Equation (1) is assumed by the surrounding gas temperature (Tg) as the first approxima~ tion because of the experimental difficulty in measuring of solid temperatures in this particular furnace. [Nox] KVM )&323i55~)~ Volatile-N ~lN21 Fig.2 Simple Reaction Model for Volatile Evolution, NOx Formation and Reduction In this study, we clarify experimentally their reaction rates, specifically the frequency factors and the activation energies. Then, for known residence times of the oxidation and reduction zones, it is possible to estimate the NOx concentration formed and reduced in each zone. 3. Experimental Figure 3 illustrates the drop tube furna~e (DTF) used in this study. This is a vertical laminar flow furnace. Pulverized coal was supplied pneumatically with the primary air from a hopper-head rotary feeder to the burner in the upper position of the furnace. The secondary air inlet was located outside of the primary air nozzle (fuel nozzle). A water-quenching sampling probe was inserted upward from the lower part of the furnace for the gas and particle sampling. The NOx concentration was deter-mined with a chemiluminecent analyzer. The 02 concentration was detected with a |
