Refinery Process Modeling: Sample Problem 6 [HF Alkylation Unit]

The author uses the principles in his book, Refinery Process Modeling, to present a stepwise, simulator-independent model building procedure. This problem demonstrates the principles in modeling a hydrofluoric acid alkylation unit.

This process can deviate from steady-state operation because of the large isobutane inventory and the "as-needed" addition of makeup isobutane. Techniques are presented to assure a steady-state material balance for the model and convergence of the recycle isobutane stream.

Two methods for modeling the reactor(s) are presented that predict the alkylate yield and heat of reaction based on the feed olefins.

Special thermodynamic methods are discussed for modeling the non-ideal phase behavior of HF with the light hydrocarbons in the fractionators.