Environmental Engineering Reference
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p
u
=(
I
−
C
)
f
,
(5.9)
p
o
=
Cf
.
There many forms for the efficiency curve [3]. In this work, the empirical effi-
ciency curve proposed by Hatch and Mular [8] is used:
(
−
)
1
c
i
E
(
x
i
)=
c
i
+
,
(5.10)
x
50
−
x
i
1
+
ex p
(
)
k
where
E
is the weight fraction of a narrow size range
x
i
of feed that reports to
oversize,
c
i
is a term accounting for bypassing small particles to oversize and
x
50
is constant for a given set of operating conditions. In other words, it is modeled as
a polynomial function depending on the screen opening
h
, the screen feedrate of
solids and the percentage of +1 inch material in the screen feed. Ore hardness of
undersize and oversize is assumed to have the same value as feed hardness.
(
x
i
)
5.3.3 Conveyor Belts
Fixed speed conveyor belts are modeled as a pure time delay;
i.e.
, the product is
p
(
t
)=
f
(
t
−
d
)
(5.11)
feed
Flowrate
f
Size distribution
f
Hardness γ
f
oversize
Flowrate
p
o
Size distribution
p
o
Hardness
γ
undersize
Flowrate
p
u
Size distribution
p
u
Hardness
γ
Figure 5.3
A screen
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