Geology Reference
In-Depth Information
Calculation of the theoretical
exergy of the mining and
concentration process from the
ore grade xm to the refining
conditions xr
D
b(xm->xr)
Assessment of the real
mining and concentration
energy
E(
xm->xr)
Calculation of unit exergy
costs
k(xm)= E(xm->xr)/
D
b(xm->xr)
Calculation of the theoretical
exergy of the concentration
process from the crespuscular
concentration xc to the mine
conditions xm
D
b(xc->xm)
Extrapolation of unit exergy
costs to xc
k(xc)
Calculation of the exergy
replacement costs (mineral
exergy bonus)
b*= k(xc)
.
D
b(xc->xm)
Fig. 12.1 Calculation procedure for obtaining a mineral's exergy replacement cost
output stream and the quantity of metal in the input. The recovery e
ciency of
the smelting operation is represented as
R
s
and for the concentration process as
R
c
. Additionally, in the mining process a quantity of waste rock always arises, and
is referred to as the stripping ratio, denoted by
S
. Hence the total quantity of rock
mined is equal to (
S
+1) times the quantity of ore mined. All these variables are
included in Eq. (12.7). This estimates the gross energy requirement (ger) of metal
production arising as a result of the contributions from mining and concentration,
with
F
mm
being the part of the ger which is inversely proportional to ore grade.
1
F
mm
=
·
[(
S
+ 1)
F
m
+
F
c
]
(12.7)
x
m
·
R
s
·
R
c
Chapman and Roberts (1983) undertook a compilation of the typical values used
in the above equation for several of the most important metals (see Table 12.1). To
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