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Show IFRF Doc. No. K 70/a/12 August 1989 - 6 - Mathematical Modelling of Pulverised Coal Flames around 4-6% was measured. Thus, there is a strong indication that the rate of turbulent combustion should be estimated using Taylor scale eddies rather than mean size eddies [10]. 3. ADAPTATION OF THE MATHEMATICAL HODEL Two flames, Flame 3 and Flame 4, measured during the AP 17 experiments [11] are computed. Both flames are of highvolatile bituminous Coal Valley coal and have a thermal Proximate VM Ash Ultimate C H N S o analysis urryl - 36.3 % - 10.8 % analysis (DAF) - 75.4 % 4.5 % 0.85% 0.3 % - 18.9 % I.CV - 28. 5 MJ /kg input of 2.2 MWl. The coal properties are listed in Table 1. The flames are issued from an Aerodynamically Air Staged Burner [12, 13]. The burner set up for both flames lS shown in Figure 3. For Flame 3 the coal gun is positioned at the edge of the burner quarl while for Flame 4 the gun is inserted 90 mm insid~. Other burner configurations and flow inputs remain unaltered. The NOx emissions of the flames djffered substantially: TABLE 1 - Properties of while Flame 3 gave 1026 ppm NOx Coal Valley coal (0% 02), the NOx emission for Flame 4 was only 600 ppm. For each flame, measurements of temperature, oxygen, carbon dioxide, carbon monoxide and NOx were taken at about 150 positions inside and just outside of the burner quarl. The overall flow pattern of both flames were also experimentally identified. .---23'---...4 flame l. flame 3 secondary oJr - prirrory aIr with cocl -----+-- Fig. 3. Burner set up for Flames 3 and 4. Primary air: velocity 17 mis, temp. 333 K Secondary air: velocity 34 mis, temp. 553 K Swirl number = 1.0, Coal flow rate 262 kglh The IFRF Furnace No. 1 is 6.25 m long with a square cross section of 2 x 2 m2. At the outlet, the furnace is contracted to 1.0 x 1.0 m2, see Figure 1. Nine cooling loops, extract around 50% of the total thermal input. The heat losses through the furnace walls are less than 5% of the total thermal input. The furnace is modelled as a cylinder with a diameter of 2.26 m. The cooling loops are represented as cold |