HF hexamerization in Fluid Types

Hydrogen fluoride (HF) is an important chemical used in many vital processes, such as HF alkylation and the manufacturing of refrigerants and other halogenated compounds. Unlike hydrocarbons, HF is polar and hydrogen-bonded. Therefore, it self-associates in both the liquid phase and the vapor phase. Experimental evidence strongly suggests that the HF vapor exists primarily as a mixture of monomer and hexamer. In addition, evidence points to the hexamer existing in the form of a cyclic benzene-like species. This behavior results in significant departures from ideality, especially in calculating fugacity coefficients, vapor compressibility factors, heat of vaporization, and enthalpies.

The hexamerization calculations for HF fluids rely on a specialized configuration for the Fluid Type within AVEVA Process Simulation. The Fluid Type uses the same thermodynamic calculations as the thermodynamic method that you select in the System list for the Fluid Type. However, it uses an additional reaction submodel to include the reaction equilibrium between the HF monomer and hexamer species as part of the phase and composition calculations. Typically, this reaction submodel includes equations for the rate constant and the reaction rates that you develop from empirical data for the reaction system. See Reaction submodel for HF hexamerization for more information.

We provide a custom HF thermodynamic library that includes thermodynamic data for the HF hexamer as part of the AVEVA Process Simulation installation. You use this thermodynamic library to add the HF hexamer component and thermodynamic data to your Fluid Types. See Configure the HF hexamer Fluid Type in AVEVA Process Simulation and Customize the HF thermodynamic library for more information.