Page 181 - Sustainability in the Process Industry Integration and Optimization

158 Cha p te r S e v e n

1995) is used to enumerate all the combinatorially feasible process
structures that satisfy Axioms (S1)–(S5) or the accelerated branch and
bound (ABB) algorithm (Friedler et al., 1996) is used to generate the
optimal process structure together with a ranked, finite list of near-
optimal structures.
Figure 7.5 illustrates the connections among the three
algorithms. Algorithm MSG generates the maximal structure, and
it can be followed either by algorithm SSG to generate all
combinatorially feasible process structures or by algorithm ABB to
generate the optimal and near-optimal processes. Algorithms MSG
and SSG require as input the list of candidate operating units, each
defined by the set of its input materials (preconditions) and
products (effects). Algorithm ABB requires, in addition to these
data, quantitative information (e.g., prices of raw materials, costs
and capacity constraints of operating units) relevant to assessing
network optimality.
These algorithms and their description are available online
(www.p-graph.com). The methodology has been demonstrated via
typical engineering decision problems (see Chapter 8 for details). A
considerable advantage of the P-graph framework is its potential for
solving large industrial problems, as indicated by its application in
solving various process systems engineering problems (see, e.g., Liu
et al. 2004; Halasz, Povoden, and Narodoslawsky, 2005; Liu et al.,
2006; Fan et al., 2008; Varbanov and Friedler, 2008).

Process Synthesis Problem

Algorithm MSG

Maximal Structure

Algorithm SSG Algorithm ABB

Combinatorially Feasible
Optimal Process
Structures (n-best Processes)
(for further evaluation)
FIGURE 7.5 Inputs to and outputs from the three P-graph algorithms.