| OCR Text |
Show RESULTS Combustion experiments involved burning four different coals with air. Optimum burner settings for minimum NOx and LOI were established at full load (100 MBtulhr) and 17% excess air (1.17 stoichiometric ratio) by systematic adjustment of swirl vanes and/or the mixing device position inside the coal nozzle. Other major experimental variables included coal fineness, excess air, and thennalload. For each test, LOI and gas species concentrations were measured. Unburned carbon loss (UBCL) values were calculated using the LOI levels. UBCL is a measure of the unutilized fuel and combustion efficiency. Approximate flame lengths were determined from the available furnace sight ports shown in Figure 1. Selected results (N0x, CO, UBCL, and flame length) are presented and discussed in this section. Table 1 lists the proximate, ultimate, and heating value analyses of the as-received coals. Fixed carbon-to-volatile matter ratios for these coals range from 1.16 to 3.02. Table 1. Fuel Analysis Montana Ohio Mahoning Pennsylvania Alabama Jim Decker 7 A Seam High Middle Kittanning Walter Low Subbituminous Volatile Medium Volatile Volatile Coal PrQ3im~ Coal Bituminous Coal Coal Fixed Carbon (%) 37.06 49.98 55.00 57.46 Volatile Matter (%) 31.93 37.85 22.21 19.00 Moisture (%) 26.36 5.70 3.25 11.11 Ash (%) 4.65 6.47 19.54 12.43 Fixed CarbonIV olatile Matter 1.16 1.32 2.48 3.02 Ultimate Carbon (%) 53.64 73.63 66.45 68.25 Hydrogen (%) 3.73 4.98 4.14 3.74 Nitrogen (%) 0.88 1.56 1.19 1.32 Sulfur (%) 0.51 0.93 1.91 0.55 Oxygen (%) 10.23 6.73 3.52 2.60 H~"tin~ Valu~ (Btyllbl 9237 13120 11647 11828 H,,[d&rQv~ Grindabili~ Ind~x 47 50 84 86 6 |
