A utilização de equações de estado (EE) na predição de propriedades termodinâmicas de sistemas biocombustíveis

Abstract

To analyze and design processes required in biofuels production, such as separation and purification, some models are required to estimate certain physical properties of the fluids related to manufacturing thereof, such as density, enthalpy of vaporization and saturation pressure. Therefore, this work proposes to investigate the use of state equations (EE) in the prediction of thermodynamic properties of biofuel systems. Cubic state equations were used: van der Waals, Peng-Robinson and Peng-Robinson-Stryjek-Vera equations and Rackett's equation to predict the fluid density of the biofuels research area. It was also evaluated the Maxwell area rule associated with a cubic state equation to estimate the saturation pressure of fatty acids and the Clausius-Clapeyron, Watson and Meyra equations to estimate the enthalpy of vaporization. These models were evaluated according to the relative deviation values calculated with respect to experimental results. The results showed that the van der Waals equation is not recommended when estimating density, or molar volume. And that the Peng-Robinson-Stryjek-Vera equation associated with Maxwell's rule is the best cubic equation to propose values of saturation pressure, also obtaining good results when allied to the Clausius-Clapeyron equation.