MODELLING AND OPTIMISATION BASED ON A COMPREHENSIVE OPTIMALITY CRITERION THE PRIMARY OIL REFINING PROCESS

Abstract

The article discusses the control of the primary oil treatment process. An analysis of previous studies revealed an unresolved aspect of the general problem: the lack of a dynamic mathematical model integrated with multi-criteria optimisation for automated control systems capable of effectively accounting for nonlinear effects and technological disturbances in real time. Existing models tend to focus on steady-state modes or use multi-criteria optimisation without sufficient dynamic coupling. The aim of this work is to develop a dynamics mathematical model of the primary oil treatment process and to determine an integral criterion of optimality for the control systems synthesis. This criterion provides an effective balance between energy efficiency, the quality of the prepared oil, and economic production indicators. To achieve this aim, a process dynamic model is proposed, combining the heat balance equation, the kinetic equation, and the modified viscosity equation. In the research it is suggested to use a generalised integral optimality criterion, which aggregates the dewatering quality, restrictions on salt content, and total energy consumption, consisting of thermal and electrical components. Based on expert assessments, a normalised vector of weight coefficients is obtained. A dynamic optimisation problem is formulated, which was solved by a genetic algorithm that realised using in the Python environment, using the direct collcation method. Optimisation is carried out for three types of oil: light, medium, and heavy, with different initial conditions and within technological temperature constraints. The proposed approach allows determining the optimal trajectory of temperature change in the electric dehydrator over time. This allows us to achieve a 15–25% reduction in energy costs with a greater effect for heavy oils, while guaranteeing the target water content less than 0,1%. The results can be used to improve energy efficiency and product quality of oil refineries.