(81b) Optimisation of Diesel Blending Scheduling

In recent years, modern refineries have been confronted with higher prices of petroleum, more stringent environment standards and stricter requirements of quality specifications. To achieve the objective of maximizing the profit, it brings great challenge toward planning and scheduling for refinery operators.

Diesel, one of the main petroleum products, has a growing market proportion because of its higher energy utilization ratio and therefore lower carbon dioxide emissions compared with gasoline. Diesel is widely used in industry and transportation. Only high quality diesel product can survive in the more and more competitive market. Refiners haven’t stopped improving the methodology in diesel production and management.

To maximize the profit or minimize the cost is the main driving force in refinery diesel management. It is difficult to achieve the optimal recipe towards the site level as an optimal recipe for one single process may be suboptimal for other processes or even infeasible for the overall refinery. A multi-period planning model, which was based on the decomposition method, was raised by Dave in 2005, making decisions at different time intervals. To optimize the recipe, refinery operators have to deal with volatile prices of crude oil and products, fluctuant market demand, uncertainty of feedstock arrivals and other abrupt changes. An MILP short-term blending and scheduling model is provided by Mendez and Grossmann (2006).

In this work, a model for management of refinery diesel streams is under development to optimize the diesel production of a refinery. A modified property estimation model, which is more accurate for diesel than traditional linear models, is employed in the off-line diesel blending process. Intricate environment regulations and product specifications, such as cetane number, sulphur content and pour point, etc are taken into account. A novel scheduling method, which involves an MINLP model, is used for optimize the profit of the total blending processes within satisfying the market requirements and property specifications. By adopting the methods, a better recipe of a refinery diesel streams can be reached.