TITLE:
Sequential Ordering Algorithm for Mass Integration: The Case of Direct Recycling
AUTHORS:
Filippo Marchione, Stavros Papadokonstantakis, Konrad Hungerbuehler
KEYWORDS:
Process Integration, Preemptive Goal Programming, Conditional Optimality, Recycling Activities Prioritization, Linear Programming
JOURNAL NAME:
Advances in Chemical Engineering and Science,
Vol.6 No.2,
April
21,
2016
ABSTRACT: In the last three decades
much effort has been devoted in process integration as a way to improve
economic and environmental performance of chemical processes. Although the
established frameworks have undergone constant refinement toward formulating
and solving complicated process integration problems, less attention has been
drawn to the problem of sequential applications of mass integration. This work
addresses this problem by proposing an algorithm for optimal ordering of the
process sinks in direct recycling problems, which is compatible with the typical
mass integration formulation. The order consists in selecting the optimal sink
at a specific integration step given the selection of the previous steps and
the remaining process sources. Such order is identified through a succession of
preemptive goal programming problems, namely of optimization problems
characterized by more objectives at different priority levels. Indeed, the
target for each sink is obtained by maximizing the total flow recycled from the
available process sources to this sink and then minimizing the use of pure
sources, starting from the purest one; the hierarchy is respected through a
succession of linear optimization problems with a single objective function.
While the conditional optimality of the algorithm holds always, a thorough statistical
analysis including structured to random scenarios of process sources and
process sinks shows how frequently the sequential ordering algorithm is
outperformed with respect to the total recycled amount by a different selection
of process sinks with the same cardinality. Two more case studies proving the
usefulness of ordering the process sinks are illustrated. Extensions of the
algorithm are also identified to cover more aspects of the process integration
framework.