Page 158 - Sustainability in the Process Industry Integration and Optimization

Fu r t h e r A p p l i c a t i o n s o f P r o c e s s I n t e g r a t i o n 135

Unused Materials or
Discharged Waste

U + U + U 3
1
2
Source 2
U 1 + U 2

Load [kg/s] U 1

Source 1

Flowrate [kg/s]
Minimum
Fresh Usage
FIGURE 6.11 Property-based material reuse Pinch diagram that combines
fresh usages to determine minimum fresh consumption (after Kazantzi and El-
Halwagi, 2005).

network design. Another graphical targeting tool that can be used to
determine minimum resource targets is the Material Surplus
Composite Curve (MSCC). The MSCC was developed by Saw et al.
(2009) based on hydrogen and water surplus diagrams (Alves and
Towler, 2002; Hallale, 2002), but it eliminates the latter’s iterative
steps; see Figure 6.12.
The drawbacks of the graphical approach can be resolved by
using an equivalent numerical tool, the PCA. This technique is
discussed in detail by Foo et al. (2006) for a case study on solvent
recycling in metal degreasing (Kazantzi and El-Halwagi, 2005).
Applying the PCA makes it possible to use the targeted fresh solvent
flow rate to construct a “balanced” material sink and source composite
diagram. Foo et al. (2006) also suggested a technique for using the
Property Pinch Analysis (graphical or algebraic) to synthesize a
property network that achieves previously established resource
targets. In addition, their paper discusses applicability of the PCA
procedure to process modifications.