1,721,117 research outputs found
Rigorous formulation for the scheduling of reversible-flow multiproduct pipelines
No full textPipelines play a major role in the petroleum industry by providing a safe, reliable and economical trans-portation mode over land. Frequently, they connect a pair of refineries or harbors with the purpose ofsharing oil products. As the construction of twin pipelines transporting products in opposite directions demands large capital investments, reversible-flow pipelines arise as a promising alternative. This paper introduces a novel continuous-time formulation for the short-term operational planning of reversible multiproduct pipelines. The proposed model allows to change the flow direction as many times as needed to meet terminal demands, determining precise time instants for flow reversals. It provides the input and output schedules in a single step, and the most convenient product used as filler to push current batches out of the line. Three examples are successfully solved with much less computational effort than previous approaches.Fil: Cafaro, Diego Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); ArgentinaFil: Cerda, Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentin
A general resource-constrained scheduling framework for multistage batch facilities with sequence-dependent changeovers
No full textThis work introduces a new MILP sequential approach to the short-term scheduling of multistage batch plants that accounts for sequence-dependent changeover times, intermediate due dates and limited availability of renewable resources. It relies on a continuous-time formulation based on the general precedence notion that uses different sets of binary variables to handle allocation and sequencing decisions. To avoid resource overloading, additional constraints in terms of sequencing variables and a new set of 0-1 overlapping variables are presented. They allow tracking the set of tasks requiring the same resource and running in parallel at the start of another process operation. In this way, the proposed formulation involves a reasonable number of binary variables and constraints and features a very good computational behavior, even in the presence of hard bottleneck resources. Four illustrative examples, one of them including multiple bottleneck resources shared by several processing stages, have been efficiently solved.Fil: Marchetti, Pablo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Cerda, Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin
Operational Scheduling of Refined Products Pipeline Networks with Simultaneous Batch Injections
No full textPetroleum refined products are mostly sent from oil refineries to distribution depots by trunk pipelines. Pipeline networks usually involve multiple input and exit terminals, and even dual-purpose stations. Several pumping operations can be simultaneously performed at different sources. Most of the computational burden on the scheduling of multi-source pipeline networks comes from three operational tasks: pump sequencing, batch sizing, and batch allocation. Previous contributions applied discrete decomposition approaches performing such tasks through heuristic-based decisions. This paper introduces an MILP continuous formulation for the operational scheduling of unidirectional pipeline networks that allows simultaneous batch injections. The problem goal is to satisfy depot requirements at minimum total cost. The optimal schedule of pumping and delivery operations is established all at once. Results show that simultaneous batch injections lead to a better use of the pipeline transport capacity and a substantial reduction on the overall time needed to meet depot demands.Fil: Cafaro, Diego Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); ArgentinaFil: Cerda, Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentin
Short-term operational planning of refined products pipelines
Full text linkPipelines are the safest and least expensive mode for transporting energy products over long distances. Refined products pipelines convey multiple oil derivatives from refineries to marketing terminals, usually through the same duct. Planning the injection, transportation and delivery of batches moving into pipelines is a very complex industrial problem with many operational constraints. This work synthesizes two innovative optimization tools for the short-term planning of oil product pipelines. The first one is a continuous-time mixed-integer linear programming (MILP) formulation for the short-term planning of pipelines connecting a single source node to multiple terminals over a multiperiod horizon. In the second approach, the MILP formulation is extended to deal with the transportation planning of multi-source pipelines. Common-carrier pipelines often present input facilities at non-origin points, whose operation raises new difficulties. Solutions to real-world case studies illustrate the performance of the proposed optimization tools.Fil: Cafaro, Diego Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Cerda, Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin
Optimal Scheduling of Refined Products Pipelines with Multiple Sources
Full text linkMost contributions on short-term planning of multiproduct pipeline operations deal with pipelines featuring a single input terminal. In common-carrier pipelines, however, several refineries located at different sites use the same trunk line for shipping refined petroleum products to downstream output terminals. They can be regarded as multiple-source pipelines with input facilities at non-origin points. The operation of intermediate sources raises some new difficult issues. Pumping runs taking place at intermediate locations can either insert a new lot or increase the size of a batch in transit. Batches are no longer arranged in the line in the same order that they are injected, and tracking the batch sequence becomes a more complex task. This paper introduces a novel continuous formulation for the scheduling of multiple-source pipelines operating on fungible or segregated mode. A case study involving a pipeline with two input and three output terminals, transporting three distillates was successfully solved over a 10-day time horizon.Fil: Cafaro, Diego Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Cerda, Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin
Dynamic Scheduling in Multiproduct Batch Plants
Full text linkThis work introduces a novel MILP formulation for reactive scheduling of multiproduct batch plants to optimally generate updated schedules due to the occurrence of unforeseen events. It can also be used to improve a non-optimal production schedule before it is executed. The approach is based on a continuous-time problem representation that takes into account the schedule in progress, the updated information on the batches still to be processed, the present plant state and the time data. To limit the changes on the current schedule, rescheduling operations involving local reordering and unit reallocation of old batches as well as the insertion of new batches are just permitted. In contrast to previous contributions, multiple rescheduling operations can be performed at the same time. The MILP problem formulation is iteratively solved until no further improvement on the current schedule is obtained. Three large-size example problems were successfully solved with low computational cost.Fil: Mendez, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Cerda, Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin
A Sweep-Heuristic Based Formulation for the Vehicle Routing Problem with Cross Docking
Full text linkCross-docking is a warehousing strategy in logistics used by process industries manufacturing products with high proportions of distribution costs. It is described as the process of moving goods from suppliers to customers through a cross-dock terminal without a long-term storage in this facility. The vehicle routing problem with cross-docking (VRPCD) consists of fulfilling a set of transportation requests using a fleet of homogeneous vehicles to sequentially accomplish the pickup and delivery tasks. Between those operations, there is a consolidation process of incoming shipments at the cross-dock. This work introduces a monolithic formulation for the VRPCD that determines pickup/delivery routes and schedules simultaneously with the truck scheduling at the terminal. To derive a more efficient formulation, a constraint set mimicking the widely known sweep algorithm was incorporated into the rigorous model. The resulting formulation based on the sweep-heuristic can find near-optimal solutions to large problems at very acceptable CPU times.Fil: Dondo, Rodolfo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); ArgentinaFil: Cerda, Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentin
A continuous-time tightened formulation for single-stage batch scheduling with sequence dependent changeovers
Full text linkThis work presents a new mixed-integer linear programming (MILP) continuous-time approach for the shortterm scheduling of single-stage multiproduct batch plants with parallel units and sequence-dependent changeovers. It uses a unit-specific precedence-based representation, combined with effective, nontrivial tightening constraints, to develop a very efficient problem formulation. The additional cuts account for the updated information provided by allocation and sequencing binary variables to systematically reduce the solution space of the corresponding LP at every node of the enumeration tree. In this way, close bounds for key variables like makespan, task earliness, and task starting/completion times are generated and continually improved throughout the search in order to accelerate the node pruning process. Alternative problem objectives like the minimum total earliness or the shortest makespan can be managed. To make a thorough comparison with previous continuous-time scheduling approaches, several benchmark examples have been solved. Results show that the proposed approach usually presents the best computational performance.Fil: Marchetti, Pablo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Cerda, Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin
A monolithic approach to vehicle routing and operations scheduling of a cross-dock system with multiple dock doors
No full textCross-docking is a logistic strategy for moving goods from suppliers to customers via a cross-dock terminal with no permanent storage. The operational planning of a cross-dock facility involves different issues such as vehicle routing, dock door assignment and truck scheduling. The vehicle routing problem seeks the optimal routes for a homogeneous fleet of vehicles that sequentially collects goods at pickup points and delivers them to their destinations. The truck scheduling problem deals with the timing of unloading and reloading operations at the cross-dock. This work introduces a mixed-integer linear programming formulation for the scheduling of single cross-dock systems that, in addition to selecting the pickup/delivery routes, simultaneously decides on the dock door assignment and the truck scheduling at the cross-dock. The proposed monolithic formulation is able to provide near-optimal solutions to medium-size problems involving up to 70 transportation orders, 16 vehicles and 7 strip/stack dock doors at acceptable CPU times.Fil: Dondo, Rodolfo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Cerda, Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin
A Hybrid Local Improvement Algorithm for Large-scale Multi-depot Vehicle Routing Problems with Time Windows
No full textOne of the major research topics in the supply chain management field is the multi-depot vehicle routing problem with time windows (m-VRPTW). It aims to designing a set of minimum-cost routes for a vehicle fleet servicing many customers with known demands and predefined time windows. This paper presents an m-VRPTW local search improvement algorithm that explores a large neighborhood of the current solution to discover a cheaper set of feasible routes. The neighborhood structure comprises all solutions that can be generated by iteratively performing node exchanges among nearby trips followed by a node reordering on every route. Manageable mixed-integer linear programming (MILP) formulations for both algorithmic steps were developed. To further reduce the problem size, a spatial decomposition scheme has also been applied. A significant number of large-scale benchmark problems, some of them including up to 200 customers, multiple depots and different vehicle-types, were solved in quite reasonable CPU times.Fil: Dondo, Rodolfo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Cerda, Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin
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