| OCR Text |
Show Model simulations can be now performed as follows. The k value is calculated from eqns.(14)-(16) for a given mill, coal and operating condition. Then, the value of Q i follows from eqn.(13). II m The iterative computation of eqns.(8)-(ll)is performed until a computed value of Q matches with Qdm. 5. Verification of the Model and Further Analysis A typical example of the size distributions of coal pulverized in the pilot mill is shown in Figure 10, compared wi th the computed. Furthermore, Figure 11 shows the variation of the fineness of pulverized coal with the feed rate of coal and the rotational speed of the rotary classifier for three different types of coals in the pilot mill. Agreement between computed and experimental results is expected since the model was developed based on the test results. 100 ~ Coal B (HGI = 36) 99.9 99 Cyclone Coal C 1.6t/h -. i-. 17000 t Coal C '#.. (49) "- 90 ~, , I o 70 Q) N 80 i:i) 70 o 100 V '#.. 60 50 40 0.01 0.1 Particle Size Xi (mm) Fig.10 A typical particle size distribution Actual verification of the model N I is shown in Figure 12 where the operating data obtained in an industrial mill(D=1.9m) is compared with the predicted. Further experimental and analytical studies were carried out using the bench- , pilot- and 'I 1 'II 6.10) , . industr~a sca e m~ s Figure 13 shows the pressure loss, ~p ,due to the particle hold-up c between the nozzle ring and the classifier as a function of the total hold-up in the mill,W, where the mill hold-up was measured by collecting and weighing after a sudden stop. As expected, a linear 7 -. '*- "- Q) N U5 V '*- - Model 0 0 N = 120rpm 70 0 240 0 o 2 3 Make- up coal feed rate Q (t/ h) Fig.11 Test results in pilot-scale mill 100~------------------------~ 80 60 Coal HGI 40 0 G 48 -- Model I:. F 32 20~--~~--~--~~ __ ~~ __ ~ o 10 20 30 40 50 Make- up coal feed rate Q (t/ h) Fig.12 Verification of model |
