OCR Text |
Show where MC is the moisture content, Meo is the initial moisture content and n is 6h(Tg - Ta) n=-------- (3) Lp~(MCo / (1 +MCo)d Here h is the external heat transfer coefficient, Tg and T. are the gas and wet bulb temperatures respectively, L is the latent heat of vapourization of water, Pwc is the particle density and d is the diameter of the particle. 1.2..,..----------------., 1.0 ,., .8 J: -Z Z .6 o J: .4 .2 • Best Fit: Y-2.5474t-4.3323b+O.011t~~.OO035J[1 6 8 10 12 14 16 18 20 22 Fuel O/N ratio Figure 2 Ratio of HeN/ammonia as a function of fuel O/N ratio NOx release is modelled for three different levels of NOx chemistry, the first assuming all volatile nitrogen goes to HCN, which then reads via R1 and R2. The second introduces NH3 formation and consumption readions as outlined in Assumptions 1, 5 and 6. The third also includes a hydrocarbon reburning readion, Assumption 4. Description of the furnace and burners A schematic view of the furnace chamber, which is part of a 350 MWe utility boiler, is given in Figure 3. The chamber is approximately 42 metres high by 14.5 metres wide by 11 metres deep and is fitted with 15 burners on each wall, in opposed firing. Low NOx burners occupy columns 1 and 2 of the furnace, and conventional swirl burners columns 3 to 5. Each burner has a thermal capacity of about 35 MW and this paper considers only 7 |