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Show R < 2 * + 1 > (13) Thus with vr = 0.05 Vt, R ~ Vt and since e °° d'1 , 6 2 5 and e = 100 for d = 10 ym, one can get d , = 9 ym. According to this analysis, p ' y p.cnt the particles having size below 9 ym will eventually be entrained by the gas streams. Referring to Figure 5 it is seen that particles having d less than about 30 ym will be burnt, and their mineral matter evaporated, prior to reaching wall. From Figure 3, it is observed that there is aobut 60 percent of mass having particle size below 30 ym for Illinois No. 6 coal while for Polish coal, it is only 30 percent. As for Illinois No. 6 coal, 60 percent of mass is burnt in the gas phase and only 40 percent is deposited inertially on the wall. Consequently at most about 40 percent of coal ash is collected as slag with the Illinois No. 6 grind while up to 70 percent could be recovered for the Polish Bytom grind. This is consistent with the experimental results given in Table 2. 4.3 EFFECTS OF BURNING Under diffusion controlled burning with constant density, the particle diameter keeps decreasing while the particle is traveling towards the wall, which results in increased drag force per unit mass. Numerical results including this effect were obtained. In this case, even though initial particle diameter is larger than 30 ym, the particle may reach a size much less than 30 ym by the time it reaches the wall. Consequently the above results are optimistic in terms of ash capture. The results obtained including burning effects suggested that there is about a 10 percent increase in transition size of the particle for capture prior to burnout. -22- ^27AVCO EVERETT |