Environmental Engineering Reference
In-Depth Information
2,50E+07
2,00E+07
1,50E+07
1,00E+07
5,00E+06
0,00E+00
5
6
7
Year
Measured collected landfill gas
Scholl Canyon - collected
Triangular - collected
Modified first order - collected
LandGEM - collected
Figure 9. Comparison of results obtained from the different applied models with the data of collected
LFG.
6.
E
NERGY
R
ECOVERY
The selected Scholl Canyon model has been used to predict the LFG production for the
case-study landfill in order to properly size the energy recovery system along the time. In
particular, reciprocating engines were considered for energy recovery purpose. The LFG
energy recovery by means of reciprocating engines is a quite wide spread practice in modern
landfills, but the energy recovery system definition and sizing, also in reference to its
economic convenience, is a crucial and tricky issue.
For this reason, the selection of the engine configuration along the time has been carried
out with the aim of obtaining the maximum profits from selling the produced electric energy.
It has been assumed that no LFG collection takes place until the fifth year included, then
the assumed collection efficiency coefficient is equal to 40% for the sixth and seventh years,
and 60% for the following years (on the basis of the designed improved collection network in
the specific plant).
Several sizes of engine have been considered with reference to existing Jenbacher
engines (kWe 143, kWe 330, kWe 511, kWe 625, kWe 836, kWe 1048, kWe 1413, kWe
1698). The amount of potential electric energy has been calculated according to:
(12)
EE
=η
⋅
LHV
⋅
V
el
LFG
LFG
where:
EE = electric energy [kW]
η
el
= engine electric energy conversion efficiency
V
LFG
= LFG flow rate [Nm
3
/h]
LHV
LFG
= LFG low heating value [kWh/Nm
3
]
