Algoritmo para cálculo de equilíbrio de fases com precipitação de parafinas

Abstract

Paraffin precipitation is responsible for several problems in industry, being usually mecanically remedied or mitigated by chemical inhibitors, what increases the costs of the production processes. Against such a background, a more economic and efficient approach consists in predicting the wax formation conditions by using simulators, which are still limited by low predictability and high computational cost. In this work, the algorithm for phase envelopes, known as Michelsen method, is adapted and computationally improved by coupling the 𝑇𝑃𝐷 stability analysis method and augmented by the proper selection of residual functions and independent variables. This enables the computation of flash calculations and multiphase equilibria saturation curves for systems with several solid phases and high CO2 content. Aiming a better oil description, especially for large chain compounds, it has been implemented a characterization routine, used to calculate necessary physical properties to the equation of state and the multisolid model. Therefore, it was possible to generate, in an automated form, phase envelopes containing diferent kinds of phase-transition equilibria. Using this algorithm, it was noticed that the Poynting factor presents important influence on solid precipitation conditions at pressures above 100 bar. Also, the addition of CO2 to the oil can increase the wax solubility, reducing the 𝑊𝐴𝑇 by up to 6K.