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Show IFRF Doc. No. K 70/a/12 August 1989 - 3 - Mathematical Modelling of Pulverised Coal Flames and gas phase is accomplished by appropriate source terms in the Eulerian momenta, enthalpy and chemical species equations. Every fifteen iterations on the Eulerian balance equations, typically 180 particles are tracked. The size distribution of coal particles is split into fifteen classes, each represented by three particles. The particles are injected into the flow from four positions inside the primary air gun. In total around 36,000 tracks are performed for each flame. The particle calculations take around 20% of the total cpu time. near burner zone I , , -U25 o 0.25 (m) Fig 2. Numerical grid in the quarl zone. 2.2 COAL DEVOLATILISATION For a good mathematical description of coal pyrolysis, the most important properties to determine are rate and yield. These properties should be established under conditions encountered in swirling industrial flames which are: heating rate of around 10' CIs, temperatures up to around 15000 C, and chemical environment of C02, H20 and 02. The IFRF coal characterisation experiments determined those properties for a number of coals [7, 8]. For the coal used in this study (HV Coal Valley coal), the high temperature yield (Yield) is 65% and the rate of the pyrolysis is limited by the heating rate of the particles. Thus, for this particular coal, the release of volatile matter is directly related to the particle temperature [8]: Tp < 500 0 C 500 0 C < Tp < 1000 0 C 1000 0 C < Tp Yield = 0 Yield = Tp /1000 x Ymax Yield = Ymax (1) |