Environmental Engineering Reference
In-Depth Information
G f is the feed ore flow to the rod mill, with size f 80 ;
G k is the product flow from the rod mill, with size k 80 ;
G p is the plant product ore flow, with size p 80 ;
P eR is the power draw of the rod mill;
P eB j is the power draw of the ball mill in section j
(
j
=
1
,
2
,
3
)
;
j = 1 P eB j is the total power draw of the mills.
The variables f 80 , k 80 and p 80 are the sizes for which 80% of the ore has a smaller
size, at the points shown in Figure 4.21.
P T
=
P eR
+
Time [min]
Figure 4.18 Test of soft sensor 2 in 2.4 days of month 1 using parameters determined on a dif-
ferent day of month 1. Shown is the actual sensor measurement (black) and the soft sensor output
(segmented)
A global operational work index W iog was defined for the grinding plant of Figure
4.21 - following the definitions of operational work indexes for rod mills and ball
mills - as
/
P t
G f
=
) ,
W iog
(4.142)
f 80 1 / 2
p 80 1 / 2
11
.
02 F TG
(
where F TG
857 [24].
From (4.142), there are four variables determining W iog . On the one hand, the
on-line measurements of two of them are almost always available; power P T is mea-
sured by highly reliable wattmeters, and ore flow G f measures the throughput of
the plant so it is maintained to provide a highly reliable measurement. On the other
hand, neither f 80 nor p 80 are measured. However, for this plant a relation has been
found linking p 80 with measured g 65 giving +65# particle size percentage (percent-
age weight of particles larger than 210 μm). This relation is
=
0
.
p 80
=
1
.
78
+
10
.
07 g 65
.
(4.143)
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