Biomedical Engineering Reference
In-Depth Information
TABLE 10.2
Economic Analysis of Three Major Biomass Cofiring Options
Direct Firing
External Firing
Gasification
4.373
a
5.67
b
Capital investment (m$)
6.052
Fuel cost savings (m$/yr)
0.596
0.382
0.54
Credit income (m$/yr)
3.373
3.373
3.37
0.657
c
0.33
d
Generation losses (m$/yr)
0
0.026
e
O&M cost (m$/yr)
1.713
1.81
Carrying charge (m$/yr)
0.328
0.454
0.43
Net after tax (m$/yr)
2.957
1.588
1.35
Internal rate of return (%)
49.10
21.11
19.30
a
Scaled up from $279 per kW estimate of Cantwell (2003) using escalation factor 1.1084% per
year.
b
Cantwell (2003) took 25,000 per year using escalation factor 1.1084% per year.
c
Capacity factor loss of 1%.
d
Capacity factor loss of 0.5%.
e
Antares (2003), Table A.1, estimate of $382 per kW
e
.
Source: From Basu et al. (2011).
existing particulate separator and fan system of the main boiler avoiding the
cost of a dust separator, induced fan, and stack.
If one does not account for reliability or technological maturity, direct fir-
ing option of cofiring offers the highest return on investment (Basu et al.,
2011).
Table 10.2
shows a comparison of costs of three options for given
plant with a given fuel and other scenario.
10.6 OPERATING PROBLEMS OF BIOMASS COFIRING
Cofiring of biomass poses some special problems due to the following basic
differences between coal and biomass:
1. The elemental and proximate analysis of coal is much different from that
of biomass. As one can see from the van Krevelen diagram (see
Figure 3.10) biomass is on the top right corner with very high H/C and
O/C ratio, while coal is near the lower left with low H/C and O/C ratio.
2. Unlike coal, the properties of biomass are highly variable and hetero-
geneous. Even
different
parts
of
a
tree
could
have
different
composition.
3. Unlike coal, when stored for an extended period, biomass absorbs mois-
ture and besides the adverse effect on thermal efficiency moisture could
also lead to the development of harmful fungus.
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