Modelagem da deposição de asfaltenos em trocadores de calor de baterias de pré-aquecimento em unidades de destilação em refinarias de petróleo

• Autor(a) principal: Sales, Flavio Kubitschek Monteiro
• Data de Publicação: 2022
• Outros Autores: [e-mail]
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/19322
• topic: Asphaltenes; Solubility parameter; Modeling; Fouling; Heat exchangers; Asfaltenos; Petróleo; Parâmetro de solubilidade; Modelagem; Deposição; Trocador de calor; ENGENHARIAS::ENGENHARIA QUIMICA

In refineries, the petroleum distillation is associated with a crude preheat train, which transfers heat from the distillation cuts and pumparound to the crude oil, thus reducing the energy consumption in the furnace. Over time, the heat load of the heat exchangers of the crude preheat train decreases due to fouling, which implies an increase of the fuel consumption. The presence of asphaltenes is an important factor that contributes to the fouling problem. Therefore, this study focuses on the modelling of asphaltene deposition phenomenon in heat exchangers. The model takes into account a material balance in the heat exchanger, an energy balance and a thermodynamic characterization of the stability of asphaltene, in order to predict a temperature profile, a deposition rate and the thickness of the deposit layer. The asphaltene solubility, modelled as a liquid-liquid like equilibrium, using regular solution theory, requires the density, the solubility parameter and the molar volume of the species involved, besides temperature and composition of the system in order to determine the critical concentration of asphaltene in the crude oil as a function of temperature. This thermodynamic model was then applied to other oil systems to evaluate the capability of the regular solution theory in characterizing the stability of both heavy and light oils. The results show a gradual increase in thickness over time. The oil fouling rate increases along the length of the exchanger but tends to decrease with time due to the decrease in temperature, caused by the increase of the fouling layer thickness. The thermodynamic model shows a nonlinear variation of the critical asphaltene concentration as a function of oil density, as the solubility parameter of the oil increases with increasing density. Fitting of precipitation, aggregation, deposition constants allowed reproducing quantitatively well the experimental results of asphaltene deposition, except for cases of asymptotic profiles of the deposit resistance, which perhaps can be well described, for example, by a more sophisticated model, which considers a term associated with the deposit removal.