part 1: overview of cogeneration and its status in asia - Fire

72 Part II: Cogeneration experiences in Asia and elsewhere
Air
4700 kW
G
Fuel
16.7 MW
Figure 2.3 Gas turbine cogeneration option for the textile mill
The investment, including the custom duty and tax, amounted to US$ 1,617/kW. The annual
maintenance cost was taken as 2.5 per cent of the total investment, i.e., US$ 190,000.
The main drawback of this option was the high price of diesel oil required in the gas turbine
that led to a long payback period. The cost of diesel oil is US$ 0.19/litre as compared with
US$ 0.12 /litre for heavy fuel oil. Moreover, the former has a lower heating value as compared
with the latter (36 MJ/litre versus 39.1 MJ/litre).
2.3.4 Option 3: combined cycle
As can be seen in the schematic diagram of this option in Figure 2.4, this is a combination of
the first two options. As a result, the combined power generation from the gas turbine and
steam turbine reaches 6.8 MW. This allows the plant to be self-sufficient during 93 per cent of
the year. The investment cost, including taxes, was computed as US$ 2,000/kW and the
annual maintenance cost was taken as 2.5 per cent of the investment.
As in the previous case, the main disadvantage of this system is the need for diesel as fuel,
which has a much higher cost when compared with heavy fuel oil.
2.3.5 Option 4: diesel engine
Exhaust
18.8 kg/s
545 o C
C T
Water: 70 o C
11.5 t/hr
(0.94 MW)
160 o C
Supplementary
Firing
Fuel: 200 kW
56 bar/271 º C
5.5 t/h,
(4.26 kW)
12 bar/188 º C
6 t/h,
(4.64 kW)
Steam
56 bar/271º C
1.05 t/h,
(0.81 kW)
Water
120 º C
12.55 t/h (1.76 kW)
This configuration consists of a diesel engine with heat recovery steam boiler with auxiliary
fuel firing option, as shown in Figure 2.5. The investment cost, including taxes, was estimated
to be US$ 1,500/kW. This option provided the best economic result for the factory. Though the
possibility of using 2 diesel engines for generating more power and selling to the utility grid
was explored and led to higher economic returns, the factory management was interested in
this alternative.
H
RS
G