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Show relationship holds between ~P and W. Furthermore, the effect of the mill size on ~Pc was inv~stigated and the following general relationship was then obtained. (17) where a 4 and n4 are descriptive parameters and Do is taken as 1 m. Thus, the hold-up in the mill can be evaluated from eqn.(17) since data on mill differential(pressure loss between the nozzle inlet and classifier inlet )are usually available even for industrial mills. The mass flow versus mill hold-up relation of eqn. (3) postulated was then analyzed for various mills by the simulation model, resulting in the following relationship. (3a) where Wst is the hold-up at a standard capaci ty Q.t for a given mill, and as and n5 are descriptive parameters. Figure 14 shows a plot of data analyzed according to eqn.(3a). .- 1000 2 ~0- 0= 0.61 m E o (m) 0 E 6 0.61 '-/ (,) 0- 0 1.9 <J 0 3.0 0 a. ,-... :J 1J '-/ (5 £. 100 ... 0 en +J Coal ~ Q) " 1:JJ 0 C ~ (/) 6 B (/) 0 0 0 Q) v H ~ :J <> I (/) 6 (/) Q) ~ 0- 10,0 0 1000 0 5 10 Holdup W (kg) (01 Do )n5 F' lOst (-) Fig.13 Pressure loss due to Fig.14 Mass transport hold-up relation It is now possible to ~valuate the mill differential via eqns.(17) and (18) by the model. In addition, since the net mill power draw is expected to be proportional to the volume of particles in the bed compressed by rollers, the estimation of the mill power draw can be made, although these are not shown here. Furthermore, since the mass transport relation was developed as eqn.(3a), it is possible to compute a simulation model for unsteady-state ring-roller milling by solving eqns.(l),(2) and(3a) simultaneously, together with eqns.(14) through (16). 8 |