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Rapid multi-component phase-split calculations using volume functions and reduction methods
  • Mohamad Fathi,
  • Stefan HickelOrcid
Mohamad Fathi
Delft University of Technology
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Stefan Hickel
Delft University of Technology
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Peer review status:IN REVISION

13 Jan 2020Submitted to AIChE Journal
13 Jan 2020Assigned to Editor
13 Jan 2020Submission Checks Completed
23 Jan 2020Reviewer(s) Assigned
06 Aug 2020Editorial Decision: Revise Minor


We present a new family of fast and robust methods for the calculation of the vapor-liquid equilibrium at isobaric-isothermal (PT-flash), isochoric-isothermal (VT-flash), isenthalpic-isobaric (HP-flash), and isoenergetic-isochoric (UV-flash) conditions. The framework is provided by formulating phase-equilibrium conditions for multi-component mixtures in an effectively reduced space based on the molar specific value of the recently introduced volume function derived from the Helmholtz free energy. The proposed algorithmic implementation can fully exploit the optimum quadratic convergence of a Newton method with the analytical Jacobian matrix. This paper provides all required exact analytic expressions for the general cubic equation of state. Computational results demonstrate the effectivity and efficiency of the new methods. Compared to conventional methods, the proposed reduced-space iteration leads to a considerable speed-up as well as to improved robustness and better convergence behavior near the spinodal and coexistence curves of multi-component mixtures, where the preconditioning by the reduction method is most effective.