Page 113 - Sustainability in the Process Industry Integration and Optimization

90 Cha p te r F o u r

CP PINCH
[kW/°C]
T<100 100°C
35 1
T<100 100°C
60 2
?
90°C
24 3
90°C
30 4
90°C
20 5

(a) More Cold Streams than Hot Streams

CP PINCH
[kW/°C]
100°C 1
35
100°C
60 2

90°C
24 3
90°C
30 4
90°C
20 5

(b) Split a Hot Stream
FIGURE 4.58 Splitting below the Pinch for N > N .
C H

The loads of the matches involving stream branches are again
determined using the tick-off heuristic. Because each stream splitter
presents an additional degree of freedom, it is necessary to decide
how to divide the overall stream CP between the branches. One
possibility is illustrated in Figure 4.60. The suggested split ratio is 4:3.
This approach would completely satisfy the heating needs of the cold
stream branches.
The arrangement in Figure 4.60 is actually trivial and can be
improved upon. Unless the stream combinations impose some severe
constraints, there is a large number of possible split ratios. This fact
can be exploited to optimize the network. In many cases it is possible
to save an extra heat exchanger unit by ticking off two steams with a