Plant-wide Scheduling and Marginal Value Analysis for a Refinery

This paper presents an integrated refinery scheduling model and its applications for a refinery located in Jiujiang, Jiangxi, P.R.China. The model integrates a crude oil unloading and storage area, a refining area, a blending area and a product storage area of the refinery. The scheduling model can be applied for optimizing the operation, configuration and production schedule of the refinery. The new modeling technique and solution strategy were developed to schedule crude oil unloading and storage. This method avoids solving an MINLP problem directly and shortens significantly the solution time. In the refining area, processing units such as CDU (crude distillation unit) and FCC (fluidized-bed catalytic cracking) were included and modeled. Yield models for CDU and FCC were used to optimize the CDU cut points and the FCC conversion level. This allows the refinery model to produce much more reliable and cost-effective solutions. A new analytical method called “marginal value analysis” is proposed to provide additional economic information for all stream flows inside the refinery. Important insights are generated using the analysis to find production bottlenecks, assist in decision making and price intermediate materials, etc. A real industrial example is used to illustrate the plant-wide scheduling model and corresponding marginal value analysis.