Simulação e otimização da produção de GLP em uma coluna desbutanizadora

Abstract

Distillation is widely used in the chemical industry as one of the main separation methods. This unit operation is performed through a distillation column, a piece of equipment designed to promote the separation of components in a mixture, taking into account the differences in volatilities of these constituents. A relevant example of distillation application is the production of liquefied petroleum gas (LPG), commonly known as cooking gas. The column studied in this work is part of the Natural Gas Processing Unit (UPGN) located in Pilar-AL. The process variables that compose this deisobutanizer tower are manually adjusted by operators using conventional instruments. The main variables of the tower are related to the reboiler temperature, reflux flow rate, pressure, and composition of the feed stream. Thus, the present study aimed to analyze the influence of the main process variables of a deisobutanizer column on LPG specification and identify conditions that allow the reduction of energy consumption. Initially, the operational conditions of the column were simulated using an Aspen Plus® simulator, and it was found that the best thermodynamic model was Peng-Robson for validation with actual operating data. Next, a sensitivity analysis was carried out on the previously selected variables to assess their impact on the specification of the overhead product. Based on these data, an energy optimization proposal was made to minimize the specific energy consumption (kWh/kg of LPG) of the column. A significant reduction in equipment energy consumption was achieved due to the reduction of the operational values of the evaluated controlled variables. These decreases had a significant impact on energy consumption, as their operation required less energy from the system. The operational cost analysis estimated a reduction in production cost of 1,409.64 R$/h and an increase in profit of 9,297.37 R$/h. From a macro perspective, the impact generated would result in savings of 223,136.88 R$/day. According to the simulations, this new column operation proposal would not result in a loss in the specification of the overhead product, which remained within the limits established by ANP Resolution Nº 825, of August 28,2020, with less than 2%(V) of pentanes and heavier componentes (𝐶5+).