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

Sample case study in a pulp and paper mill 105
Table 2.1 Process steam rates and power demand used in the sizing options
(A) Thermal Match
Process steam (kg/hr) Annual steam generation (TJ) Heat deficit (TJ) Excess heat (TJ)
5,000
13,000
103
269
(B) Power Match
Power demand (kW) Annual power generation (MWh) Power deficit (MWh) Excess power (MWh)
1,500
2,430
11,235
18,200
Notes: 1. Enthalpy of required process steam is 2,761 kJ/kg.
2. Annual actual working period is 7,884 hours/year.
55
0
1,480
3. Total annual thermal energy requirement of CCP is 158 TJ.
4. Total power requirement of CCP is 12,715 MWh.
b) Technical potential evaluation
Steam Turbine
Fuel
Boiler
Figure 2.2 Backpressure steam turbine cogeneration system
0
0
111
0
5,485
Figure 2.2 shows a backpressure steam turbine cogeneration system. Superheated steam
was considered for typical inlet pressures of 20, 30, 40, 50, 60 70 bars respectively. The
power to steam ratio, the power generated by the steam turbine for a given process steam
requirement as well as the steam generated for a given power requirement can be estimated
by using the following formulas:
• Power to Heat Ratio
PHR =
Steam
− × η × η
( H H )
in out tb gen
H
out
Turbine
Process
G
(kWe/kWth)
Electricity