Environmental Engineering Reference
In-Depth Information
related to economic costs. Three main components are assumed for f1(x), that are, recycling
cost
r
g
C
(
x
)
C
(
x
)
B
(
x
)
, maintenance costs
, and benefits
related to either energy or RDF
production, leading to the following expression:
f
(
x
)
=
C
r
(
x
)
+
C
g
(
x
)
−
B
(
x
)
(3.7)
1
All these costs are function of the previously defined decision variables.
Unrecycled material, in this model, is simply the total waste produced R minus the waste
separately collected, namely:
9
∑
=
f
(
x
)
=
R
−
α
i
r
(3.8)
2
i
i
1
Q
in this work) is function
of the decision variables (and of the different parameters that characterize each treatment
plant efficiency). The third objective is:
(
x
)
The quantity of waste per year sent to the landfill (called
f
(
x
)
=
Q
(
x
)
(3.9)
3
5
Finally, emission concentrations and quantities depend on the chemical reactions, which
take place among the various elements present in the entering refuse. Every material present
in the wastehas a specific percentage of S, Cl, C, N, O, H, F, that can give the following
compounds: CO
2
, H
2
O, HCl, O
2
, N
2
, SO
2
, HF. The quantities produced depend on the mole
numbers, on the flows entering the incinerator plant, and on the efficiency of exhaust gas
treatment. In the proposed approach, only HCl emissions have been taken into account.
The fourth objective is:
f
(
x
)
=
M
(
x
)
(3.10)
4
HCl
where
M
HCl
(
x
)
is the overall amount of chlorine entering daily the incinerator plant.
3.4.2.Constraints
Different classes of constraints have been included in the formalization of the
mathematical optimization problem: minimum recycling constraints, treatment plants' size
constraints, flow conservation constraints, RDF and SOM composition constraints,
incineration emissions constraints, landfill saturation constraints.
3.5. The Case Study
The model proposed in this paper has been applied to a case study concerning the
municipality of Genova where refuse disposal is a very critical problem. With a daily waste
production of 1355 t, the current solution is the disposal in a unique landfill, whose residual
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