Research On Optimal Scheduling Of Fueld Gas System In Refinery And Its Application

Fuel gas system, which is the largest energy source in refinery, is one of the most important parts of refinery's energy system. Optimal scheduling of fuel gas system will play a great part in energy saving, and definitely will bring considerable profit to the refinery at the same time. However, few research works, neither in academic nor in engineering, have been reported on this field. As a result, it is extremely valuable to give a comprehensive research in this problem. After surveyed major research issues in refinery fuel gas system and scheduling problem, some research items about the optimization of fuel gas system scheduling in refinery are investigated systematically. Finally, the application of this optimal scheduling is realized in a real refinery. i he main contributions in this dissertation are listed as follows:1) Fuel gas system is considered as core of the energy system according to its important role in refinery. Consequently, a modeling framework for multi-period optimization of fuel gas system scheduling, which integrate all kinds of the energy form such as fuel gas, steam, electricity and so on, is proposed based on the topology structure of fuel gas networks. The modeling framework is the base of the whole research.2) Some reasonable assumptions are presented so that an MILP model for multi-period optimization of fuel gas system scheduling can be proposed. Marginal value analysis, which provides additional economic information of the fuel gas system, is introduced into the research. This analytical method is used to identify the system bottleneck, propose the improvement measure and assist decision-making in the case study.3) In order to deal with the imprecise natures in the fuel gas system, such as prediction of production rate of fuel gas, prediction of energy demand of equipments and cost coefficient in the objective function, fuzzy possibilistic programming method is introduced. To give the sensitivity analysis of the uncertainty parameters in the fuzzy model, marginal vale analysis method, which will improve the flexibility, is proposed.4) The fuel gas pipeline network is classified by its topology structure. A logical modeling method, which is called generalized disjunctive programming(GDP), is introduced to model the pipeline with self-producing-self-consuming equipment and the pipeline with fuel gas source, while an iterative procedure based on pipeline network simulation is proposed to effectively deal with the loop structure pipeline network. Thus, the solution of a complex MINLP formulation is replaced by the sequential MILP problem in condition that the reliability of the scheduling decisions are guaranteed. This makes it possible to execute optimal fuel gas system scheduling in real refinery.5) The model for optimization of steam system in refinery is introduced. By integrating this model with that for optimization of fuel gas system, an integrated optimal scheduling strategy which consider steam system and fuel gas system simultaneously is presented. Global optimization will be obtained during scheduling of refinery energy system by using this integrated optimal scheduling strategy.6) A model for optimization of fuel gas system scheduling in a domestic complex refinery is proposed. Furthermore, a systematic validation method for engineering application is designed. Through these validations, reliability of the scheduling model and solving strategy and effectiveness of the scheduling decisions is guaranteed, and application of optimal fuel gas system scheduling is realized in this real refinery.Finally, a summary of the research referred above is concluded and the prospect of future study is indicated in this dissertation.