Page 97 - Sustainability in the Process Industry Integration and Optimization

74 Cha p te r F o u r

(a) T * Q Hmin–(Q HP+W) (b) T * Steam

Q HP+W

PINCH Q HP +W
HEAT
Q HP W W
PUMP
Q HP
CW
Q cmin–Q HP
ΔH
Appropriate placement Load and temperature lift on the GCC
FIGURE 4.32 Heat pump placement against a heat recovery problem.

T*
Q HP +W COP
5
W
6
MAX
2
Q HP +W 3
W T* SINK
½ΔT min ΔT PUMP
T* SOURCE 4 4
Q HP
1
MAX
3
ΔH ΔT PUMP
FIGURE 4.33 Procedure for heat-pump sizing.

As a specific example, assume that the GCC in Figure 4.34 reflects
an industrial process with ΔT = 20°C and that a heat pump is
min
available, described as follows:

˜
0.874
COP 100.18 T pump (4.8)
Focusing on the Pinch “nose” (a sharp nose provides a better
integration option) allows choosing a shifted temperature for the
* = 85˚C; see Figure 4.35. Using this
source
heat source, in this example: T
value allows extracting a maximum of 6.9 MW from the GCC below
* = 100˚C results in an upper bound of 2.634
sink
the Pinch. Setting T
MW for the sink load. Transforming to real temperatures and taking
the difference yields a temperature lift of ΔT = 35°C. By Eq. (4.8),
pump
the COP is thus equal to 4.4799. Given the upper bounds on the sink