A boundary value design method for complex demethaniser distillation columns

Muneeb Nawaz, Megan Jobson

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Typically the number of design options for demethaniser flowsheets, that recover methane from a gas mixture, is large. Repetitive simulations, to evaluate the economic viability of alternatives, do not usually enable a thorough exploration of the variable space for the purposes of process synthesis. More comprehensive process optimisation is facilitated by shortcut design models and a suitable optimisation framework. These optimisation results, applying shortcut models, are useful at the initial design stage, when the range of flowsheet options and operating conditions to be explored is relatively wide.A demethaniser column has many degrees of freedom, including the operating pressure, the location and the order of feeds, the number and duty of side reboilers and the flow rate of the external reflux stream. The complexity of the demethaniser column precludes the use of the Fenske-Underwood-Gilliland shortcut design method. An appropriate design model for the demethaniser is presented for application within an optimisation framework for process synthesis and evaluation. The column design model is computationally relatively undemanding, yet accurate, so should allow evaluation of both energy demand and equipment requirements.The design model presented is a semi-rigorous boundary value method for the design of complex demethaniser columns separating multicomponent mixtures. The method has been implemented within MATLAB and linked to HYSYS for prediction of physical and thermodynamic properties. Industrially relevant examples demonstrate that the results of the proposed design methodology are in good agreement with those of rigorous simulation. © 2011.
    Original languageEnglish
    Pages (from-to)1333-1347
    Number of pages14
    JournalChemical Engineering Research and Design
    Volume89
    Issue number8
    DOIs
    Publication statusPublished - Aug 2011

    Keywords

    • Demethanizer
    • Shortcut model
    • Side reboilers
    • Simplified model
    • Simulation

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