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Decomposing large problems into several smaller subproblems is wellknown in any problem solving endeavor and forms the basis for our flowsheet decomposition heuristic (FDH) described in this short note. It can be used as an effective strategy to decrease the time necessary to find good integerfeasible solutions when solving closedshop scheduling problems found in the process industries. The technique is to appropriately assign each piece of equipment (i.e., processunits and storagevessels) into groups and then to sequence these groups according to the materialflowpath of the production network following the engineering structure of the problem. As many mixedinteger linear programming (MILP) problems are solved as there are groups, solved in a prespecified order, fixing the binary variables after each MILP and proceeding to the next. In each MILP, only the binary variables associated with the current group are explicit search variables. The others associated with the unsearched on binary variables (or the next inline equipment) are relaxed. Three examples are detailed which establishes the effectiveness of this relaxandfix type heuristic.
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