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Planning and Scheduling of Production and Distribution Operations in Oil Refineries

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Abstract:
This work discusses planning and scheduling applications for refinery operations. Firstly, we present the several issues inherent to this study in the Chemical Processing Industry in general, as well as in the Oil Industry in particular, that are relevant to the development of models for process operations based on mathematical programming. Following, the major solution methods are summarized, with emphasis on those aimed at mixed-integer linear and nonlinear optimization models. The development of a nonlinear planning model for refinery production is presented. The model is able to represent a general refinery topology and allows the implementation of nonlinear process models as well as blending relations. Real-world applications are developed for the planning of diesel production in the RPBC refinery in Cubatão (SP, Brazil) among others. The optimization results were compared to the current situation, where no computer algorithm is used and the stream allocation is made based on experience, with the aid of manual calculations. The new operating point represents an increase of several million dollars in annual profitability. The second portion of the work addresses scheduling problems in oil refineries that are formulated as mixed integer optimization models and rely on both continuous and discrete time representations. The problem of crude oil inventory management that involves the optimal operation of crude oil unloading from pipelines, transfer to storage tanks and the charging schedule for each crude oil distillation unit are discussed. Furthermore, we consider the development and solution of optimization models for short-term scheduling of a set of operations that includes: product receiving from processing units, storage and inventory management in intermediate tanks, blending in order to attend oil specifications and demands, and transport sequencing in oil pipelines. Important real-world examples on refinery production and distribution are reported such as: the diesel distribution problem at RPBC refinery and the production problems related to the fuel oil/asphalt and LPG areas of the REVAP refinery in São José dos Campos (SP, Brazil). The short-term crude oil scheduling supply problem on a distribution complex that contains ports, refineries and a pipeline infrastructure capable of transferring oil from the former to the latter, is addressed. The ports comprise piers, which receive vessels for discharging, storage tanks and a network that connects each other. The model considers a number of other issues, including intermediate storage, settling tasks and allocation of crude oil by its qualitative characteristics. The model is represented through a mixed-integer linear programming (MILP) continuous-time model based on events. Branch and Bound algorithms based on LP relaxation are employed in order to generate feasible solutions. Finally, the problem of crude unloading from vessels until charging the crude distillation units in a single refinery is discussed, with the objective of integrating the supply and production steps in a simple structure.

Type of Seminar:
Public Seminar
Speaker:
Prof. Jose M. Pinto
Dept of Chemical Engineering University of Sao Paulo, Brazil
Date/Time:
May 12, 2000   16:00
Location:

ETH Zurich, ETL K 25, Physikstr.3, 8006 Zurich
Contact Person:

Prof.M. Morari
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Biographical Sketch:
José Mauricio Pinto. Assistant Professor of Chemical Engineering at the University of São Paulo. Received his M.Sc. from COPPE-UFRJ and Ph.D. from Carnegie Mellon University. Areas of interest include the development of optimization methods and their application in process systems engineering including operations, scheduling and control as well as their integration. Process planning and scheduling. Activities include the development of optimization models and solution techniques for chemical processes. Important industrial-scale development projects are currently being carried on with chemical and petrochemical companies. Another important issue that is under development is the integration of planning and scheduling models for large systems. Process Integration. This includes the modeling of raw material and distribution logistics. As for batch processes, performance models are being incorporated in short term scheduling models. Also, logic based and metaheuristic techniques as well as disjunctive approaches must be explored in the search of efficient solutions from the computational standpoint. Process operations. Models are being developed for the optimal operation of water treatment plants. Other systems include fed-batch and batch reactors, for which optimal control methodologies are being studied. Developments are being considered for the optimal multistage operation of crystallization units. Process design and synthesis methods. Applications include the optimal selection, sequencing and design of downstream processes, the optimal design of multiproduct biochemical plants as well as the optimal synthesis of chromatographic steps for the purification of proteins. Optimal configuration models for plate heat exchangers are being tackled. Currently coordinates research projects on optimal operations of batch plants sponsored by PADCT and VITAE and is involved in projects for the development of scheduling models in oil refineries, sponsored by Petrobras and FAPESP.