(30e) Optimum Product Yields of Vacuum Distillation Unit from Petroleum Refinery Process

Vacuum distillation is employed on heavy petroleum fractions, with large applications on heavy and ultra-heavy crude processing, motivated by difficulties founded in processing these crudes at atmospheric pressure, due to the boiling range of the compounds in their compositions. These compounds would be easily decomposed if they were distillated under atmospheric pressure. The products obtained from this unit are used as feedstock for Fluid Catalytic Cracking Unit (FCCU). The relevance of this work can be based on many aspects, such as the trend of refineries in promoting modifications in vacuum towers and their related systems. Economically, due to the need of increasing the yield of gas oil production, used as feed in the Fluid Catalytic Cracking Unit (FCCU), and the production of asphalt and other products, as well as the need of a better recovery and use of the heavy fractions of the crude, caused by the raising market value of petroleum crudes. Technologically, due to the need of new technologies that could allow a higher participation of Brazilian crudes in national refineries processes, since the majority of crudes produced nowadays in Brazil are composed by heavy crudes, with a high amount of residue produced. The main objective of this work is the comprehension of the steady state and dynamic behavior of the system in order to define on-line optimization strategies and control. To achieve the objective a distillation vacuum column is established in a simulator with all auxiliary equipment, defining and characterizing feed and products, evaluating convergence criteria of the entire system in the steady state, followed by an optimization of the system. The dynamic behavior of the system is simulated, in order to evaluate the impact of load changes, even in operational variables as in design variables. The steady state simulation allow to take into account the whole plant with the main auxiliary equipment, and provided the study of many conditions, as well as a guide to choose variables to be manipulated in order to achieve product requirements. Some blends of crudes were tested, and optimization in steady state were applied, according to energy consumption and product yield goals. The optimization in the steady state has lead the choose of a set of control variables, and respective set-points. The dynamic behavior of allowed to evaluate the impact of load changes, with an atmospheric column placed before the vacuum tower. The effect of heat load changes in furnace, as well as heat load changes in the condenser of vacuum column were considered, and the set of control variables reacted to the load changes, even in feed changes, such as feed flow rate and others.