Use of pitzer generalized equations for thermodynamic gas assessment

Abstract

The Virial equation was the basis for generalized Pitzer equation and considered the interaction forces between molecules, as preponderant to know the mechanical behavior of process. The Virial equation was based on polynomial equation whose degree takes into account the number of molecules that interact with each other. The absence of experimental data for the application of the Virial equation resulted in the proposal of generalized correlations that make it possible to determine the thermodynamic parameters, based on the critical and reduced properties of each gas, in addition to the acentric factor that relates the size of the molecules. For this correlation, was insited the acentric factor that relates with moleculares size. In this way, here were evaluate the behavior of gas compressibility factor (Zi) as function of pressure and temperature, based on a numerical study carried out from a computer program, developed in C++ language, using generalized Pitzer`s equation, for three differents gases. From the results obtained, it was possible to observe the similarity of Zi behavour and its dependence with pressure and temperature. For this, we concluded that molecular attraction and repulsion forces are more effective for systems with high pressure. The attractive forces are more intense above 200 bar, when the repulsive forces prevail. It was also concluded that thermodynamic gases behavior is directly related to characteristics of type of gas evaluate.