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In-Depth Information
the comminution exergy c
ost
of a galena fragment of 100 m side dimension, is
10 40:40[kJ=kg][m]
0:5
=[
p
10
2
m] = 40.40 kJ/kg whilst the concentration exergy
cost is 85,125 MJ/kg
11
.
Finally, it should be noted that it makes no sense to apply exergy replacement
costs to fossil fuels, due to the impossibility of reproducing the photosynthetic
process that once created the resource. Furthermore, the value of a given fossil
fuel relies on its inherent chemical exergy, which once burnt disappears along with
its inherent usefulness. On the contrary, the chemical exergy of metals and other
non-fuel minerals does not generally disappear upon disposal to landfill. Rather
it is the concentrated state of minerals in deposits that is eventually lost. Hence,
fossil fuels can be thermodynamically compared to the exergy replacement costs of
non-fuel mineral resources. In fact, as seen in Chap. 12, the exergy of fossil fuels is
in the same order of magnitude as the exergy replacement costs of minerals.
9.7 Thermoeconomics in the mining and metallurgical industry
In this chapter's previous sections the authors have provided the specific tools re-
quired for a global exergy assessment of mineral resources. All such tools fall under
the umbrella of Physical Geonomics (Chap. 4). As was seen in Chap. 3, Thermo-
economics evolved into Physical Geonomics, thereby widening the level of analysis
from the industrial to the global scale. Yet curiously, the development of the latter
has led to progress in the former. In this way and although outside the scope of
this topic, the approach can be used to determine the physical cost of producing a
given metal or industrial mineral in a specific facility.
This is something which can be carried out through an extended thermoeconomic
analysis. As was seen in Sec. 3.3.1, Thermoeconomics is essentially an Input-Output
theory (albeit an unconventional one) in which the Second Law, through exergy
analysis, is applied to any process system. In contrast, conventional I-O analyses
are frequently used to track economic transactions related to commodities at a much
more aggregated level, in which money is the yardstick
12
.
Thermoeconomics looks for process details and is used to assess the actual phy-
sical costs of any industrial process. At the core of Thermoeconomics is the idea
that the production purpose defines e
ciency and cost and it is this “motto” which
is systematically applied throughout. The overall industrial purpose (for instance,
the preparation of a set of metals at a given purity in the mining and metallurgical
industry) is subsequently transferred to each and every sub-process.
This novel discipline has been extensively used for the optimisation of power
plants, where predominantly energy flows exist. Energy flows are easily converted
11
This value is taken from Table 12.2.
12
Beyond that, Leontief et al. (1983) first applied I-O analyses to assess the extraction and use
of non-fuel minerals throughout the world economy. Also Nakamura et al. (2007) proposed the
“Waste Input-Output Approach”.
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