Modeling And Solution Algorithm For Short-Term Scheduling Of Crude Oil In Refinery Based On Mathematical Programming

Short-term scheduling of crude oil operation issue has been greatly concerned by refiner-ies.The quality of detailed short-term production schedule directly affects the efficiency and production safety of refineries.Researches on crude oil scheduling in the literature are mainly based on mathematical programming formulations,from the earlier discrete time models to synchronous continuous time representation models,to nowadays asynchronous time repre-sentation continuous time models.This thesis focuses on the crude oil scheduling problem of typical inland refineries,and also conducts a research on the scheduling problems of spe-cial inland refineries that process high fusion point crude oil.The main research work and contributions are as follows:·Up to now,mathematical programming models constructed for crude oil scheduling problems in the literature have not considered the regulation requirements of actual pro-duction processes such as crude oil residency time constraints,charging tank switch constraints,simultaneously supplying oil to a distillation tower by multiple charging tanks,etc.Establishing a mathematical programming model that meets the requirements of a actual production process is one of the research goals of this thesis.For a typical in-land refinery,this thesis introduces some necessary process constraints in actual refining production,and illustrates and analyzes the impact of these constraints on actual crude oil operation scheduling problems.Two important factors affecting the schedulability of a system,the crude oil residency time and the highest crude oil transport speed are analyzed in detail.·A dual-pipeline crude oil transportation system requires the transfer of high fusion point crude oil and the sharing of storage tanks between the two types of crude oil,which is more challenging than single-pipeline system scheduling.In this thesis,the asynchronous continuous time representation mathematical programming model is used to study the short-term operation scheduling problem of crude oil operation of dual-pipeline system.The model considers the pipeline ejecting and reverse ejecting in the dual-pipeline crude oil transportation system,the pipeline preheating and the high fu-sion point crude oil continuous transmission process,and the pipeline is not empty.The experimental results of the model show that the model achieves a good control for the continuous transmission of high fusion point crude oil,and it is ready to transport as much high fusion point crude oil as possible.·Propose a new algorithm for iterative solution of MINLP model,which can eliminate the composition concentration discrepancy by developing a valid inequality and an algo-rithm to determine the number of priority time slots.In order to find a solution without composition concentration discrepancy,after analyzing the properties of the problem,an effective inequality is added to the model to ensure that the composition concentra-tion of the crude oil injected into a charging tank is in the range of regulation required by the production process.It can handle the concentration range of the composition of crude oil.In the process of modeling the short-term scheduling problem of crude oil,it is necessary to know in advance the number of priority time slots that have a great in-fluence on the size of the model.In order to reduce the size of the model,an algorithm is proposed to find the number of priority time slots.Then,a new method for solving the MINLP model of short-term scheduling problem of crude oil is proposed.Each iteration solves an MILP problem and obtains a partial solution without composition concentration discrepancy.According to the partial solution,some nonlinear constraints are converted into linear constraints to obtain a simplified MILP problem,and the next iteration is used to solve this problem.In this way,we are relieve to solving the NLP problem;when a feasible solution is found,the composition concentration discrepancy is completely eliminated.This is a significant development in this area of research.·Propose a stochastic approximation algorithm for short-term crude oil operations schedul-ing problems.Starting from the definition of computational model and complexity,after giving some lemmas and theorems for algorithm performance analysis and proof,this thesis proposes a random approximation algorithm for the size of set unions,and then analyzes and proves its performance.Since the DNF counting problem is a special case of the set union problem,we apply the algorithm to the DNF counting problem.Through the appropriate modification of the DNF counting problem,a random ap-proximation algorithm for short-term crude oil scheduling problems is proposed.The algorithm greatly reduces the search space of the original problem,and does not need to solve an MILP problem.After executing the set number of trials,the best feasible solution found by the algorithm is given with high probability.In this thesis,the actual production process demand in the production process of refinery is studied,and an effective algorithm for removing the composition concentration discrepancy is proposed.A random approximation algorithm applied to short-term scheduling of crude oil operations is proposed.The research of this thesis fills the gap in this aspect and realizes comprehensive automation of refining enterprises.Implementation of these algorithms makes a useful contribution.