Page 261 - Sustainability in the Process Industry Integration and Optimization

238 Cha p te r T e n

• A heat engine could also be a candidate for the pocket in the
GCC below the Pinch. However, since ΔT is small—about 80°C, or
[(190 + 10) – (130 – 10)]—only a small amount of work may be produced.
Answer to (e).
• Reactors. The reaction is endothermic and, to save utility, its heating
medium heat demand should be placed below the Pinch. It is now placed
above the Pinch. If the pressure and temperature of reactor R1 are
reduced, then an alternative heating media with lower temperature levels
could be used. As a result of decreased R1 pressure, the boiling points of
feeds F1 and F2 would also decrease. This would result in different
targets. For instance the GCC could be shifted more to the left and the
Pinch point could be changed, resulting in more process heat recovery.
• Distillation columns. The reboilers of columns A and B currently
evaporate the entire flow from the column bases. The appropriate
arrangement would be to move the reboilers to evaporate only the
branches of these flows that are intended for the columns.
• Feed vaporization. In the base case, the vaporization of F1 and F2 are both
placed below the Pinch. However, as mentioned, the current vaporization
of F2 results in cross-Pinch heat transfer. Also, the vaporization of F1
employs utility heating below the Pinch, which should be eliminated
and substituted for process-to-process heat recovery.
• Soft data. The P1 and P2 target temperatures are soft data that can be
changed. The temperatures could be increased to reduce cold utility
required, but this would not change the CC much.

10.4 Utility Placement

10.4.1 Utility Placement: First Problem

Problem 6: Task Assignment
A set of data for a part of a crude distillation process has been
extracted, and the stream data are shown in Table 10.15. For this
problem, the minimum temperature difference is ΔT = 10°C. The
min
available utilities are presented in Table 10.16.
A targeting procedure was performed for the initial data
summarized in Tables 10.15 and 10.16. Figure 10.20, which exhibits
two Pinch points, shows the balanced CCs for the problem.

(a) Complete the missing entries in Table 10.15.
(b) Identify the Pinches and explain their significance.
(c) Draw the design grid for the problem, including the hot utilities.
Position the streams relative to the location of the Pinches.
(d) Design the MER HEN below the Process Pinch.
(e) Design the MER HEN above the Process Pinch.
(f) Design the MER HEN above the Utility Pinch.