| OCR Text |
Show parameters. The classification modulus n1 depends on the coal-toair ratio, the cut-off size xso on the air flow rate Q1\ and a constant kl on mill size. The partial classification efficiency value in the secondary classification zone S1 is also expressed as >- 1.0 __ -----~~I111"""~:::ms:"""""':~~ (7) g ~ ·~O.6 ~ where a 2 , n2 and xso are descriptive ~ ~~ parameters, D the classifier diame- m ~ ter, H the cl~ssi f ier inlet height, .2 0.6 ~ F the coal flow rate and v the air ro ~ velocity at the classifierc inlet. ~ 0.4 The parameters of a 2 and n2 depend ~ Primary ~ on the classifier type and further- - 0.2 ClaSSification~ more n2 on the air-to-coal ratio. 'f ~ Figure 7 shows a typical example of ~ OL.----....:..;L..-....-~..;....~.... ~- ---~--- these classification efficiencies 10 50 100 500 1000 computed for a pilot-scale ring- Particle size Xi (~m) roller mill(D=0.61m) operated at normal operating conditions. Fig.7 Classification efficiencies 4. Analysis of Ring-roller Milling System Steady-sta~e continuous grinding tests were performed on a bench-scale(D=0.17m) and the pilot-scale mills. The test data were analyzed as follows. At steady-state conditions, eqn.1 is reduced to ( 8 ) and Wi =(1+C' )(1+C)w1 ( 9 ) where C' and C are the primary and secondary circulation ratios defined as C'= T'/F and C=T/Q, respectively(see Figure 2). This set of equations is readily computed for giveR values of g1' 51' b1j , W, F', c1 and s1' starting with i=l. Since 1~1 w1=1, n E w1=(1+C' )(1+C) (10) 1-1 The mill output rate, Q, is then computed from Q=F' /{(I+C' )(I+C)) Furthermore, the weight fraction of the product of size then computed from the following equation. ( 11 ) (12) The values of Wand F' depend on the mode of operation of the 5 |
