Page 305 - Sustainability in the Process Industry Integration and Optimization

282 Cha p te r T w e l v e

2. Develop a mass and heat balance. This should be based on
the designed process flowsheet data and calculations and/
or on measurements taken from the operating plant (if the
study is for a retrofit).
3. Select the streams. This is a critical step and, as will be shown
in this chapter, not as straightforward as it may seem.
4. Remove all the existing units related to the PI analysis. For
Heat Integration, remove all heat-transferring units, for
mass water integration remove all water interconnections
(the pipes). This step is also critical—without it, the
optimized design would not differ from the initial design.
Section 4.2.4 provides an example illustrating this activity.
5. Extract the stream data for the PI analysis. Different data are
relevant for each PI analysis type. For HI heat loads and
temperatures are extracted.
6. Make a qualified initial guess for the ΔT value; this value
min
can be adjusted later at various stages of the design
optimization.
7. Perform the Pinch analysis: obtain the Pinch temperatures
and the utility targets.
8. Design the initial (heat exchanger) network using the
criterion of maximizing energy recovery.
9. Check for a cross-Pinch transfer and for inappropriate
placement of utilities.
10. Check for proper placement of reactors, separation columns,
heat engines, and heat pumps.
11. Investigate the potential for further modifying the process
in order to minimize energy consumption and reduce
capital costs. Investigate the potential benefits of applying
the plus-minus principle (see Chapter 4) and the KHSH and
KCSC principles (see Figure 4.44).
12. Investigate the potential for integration with other processes—
that is, Total Site Analysis.
13. Consider the implications of pressure drop (trade-offs between
heat savings and extra energy for pumping) and the physical
layout (capital cost of heat exchangers and/or piping).
14. Make the preselection of heat exchange equipment and
perform the preliminary costing. Provision should be made
for variations in the future price of energy.
15. Make the first optimization run of the predesign plant or
site, and make adjustments to ΔT .
min