Effective utilization of equations of state for thermodynamic properties in process simulation

Thermodynamic property computations using equations of state first require computation of the density root. Since higher level calculations such as single‐stage flash, distillation and data regression are usually performed iteratively, properties are often demanded at conditions where the appropriate density root does not exist. A strategy of returning suitable pseudoproperties under such conditions is proposed. It has been successfully used in ASPEN (Advanced System for Process Engineering), a general process simulator developed at the Massachusetts Institute of Technology.