Optimizing the Polynomial to Represent the Extended True Boiling Point Curve from High Vacuum Distillation Data Using Genetic Algorithms

Molecular distillation process has been used to obtain an extended true boiling point (TBP) curve (above 565 °C up to 700 °C), compared with the results offered by traditional methodologies like ASTM D 2892 and ASTM D 5236. This separation process has the advantage of operating under conditions that reduce the thermal decomposition of the oil. In this paper, polynomials to represent the extended true boiling point curve up to 565 °C from molecular distillation data are proposed. The development is based on molecular distillation experimental results of 14 atmospheric and 5 vacuum oil residues obtained in Pilot and lab scale distiller in other works of the research group at Separation Processes Development Laboratory (UNICAMP). The experimental data were classified in seven different classes based on API density. In first instance, a database was built to perform an extension of the TBP curve of each oil, using the DESTMOL correlation to find the atmospheric temperatures that correspond to the distiller operation temperatures. The results of the three methodologies (ASTM D 2892, ASTM D 5236 and molecular distillation) were adjusted to a 3rd order polynomial as function of the accumulated mass percent. The coefficients were optimized using genetic algorithms. Finally, a variable analysis procedure was developed in order to determine the influence of the genetic algorithm parameters (population size and number of generations) in the obtained response and improve the average absolute deviation percent (%AAD). As a result, a third order fitting polynomial was found for every oil class, presenting %ADD lower than 3%.