Page 101 - Sustainability in the Process Industry Integration and Optimization

78 Cha p te r F o u r

energy demands. For purposes of Heat Integration, the column is
represented generally by a rectangle: the top side denotes the reboiler
as a cold stream, and the bottom side denotes the condenser as a hot
stream; see Figure 4.40.
There are three options for integrating distillation columns:
across the Pinch, as shown in Figure 4.41(a); and entirely below or
entirely above the Pinch, as shown in Figure 4.41(b). Integrating
across the Pinch only increases overall energy needs, so this option
is not useful. The other two options result in net benefits by
eliminating the need to use an external utility for supplying the
distillation reboiler (above the Pinch) or the condenser (below the
Pinch). The GCC is used to identify the appropriate column integration
options. Figure 4.42 illustrates two examples of appropriately placed
distillation columns.

T *
A Reboiler

A, B

Condenser

B
H
FIGURE 4.40 Distillation column: T–H representation.

(a) (b) A
T* A + Q DIST T* Q DIST
Q DIST Q DIST

PINCH PINCH Q DIST
Q DIST
Q DIST

B + Q DIST B
Across the pinch Below or above the pinch

FIGURE 4.41 Distillation column: Integration options.