Dynamic Modelling and Optimisation of Large-Scale Cryogenic Separation Processes

MARIELA RODRIGUEZ; J. ALBERTO BANDONI; M. SOLEDAD DIAZ

Chemical Engineering Transactions , Vol. 6

AIDIC

Lugar: Milan; Año: 2005; p. 179 - 184

In this work, the open loop dynamic optimisation of a large-scale natural gas processing plant is performed. A rigorous differential-algebraic equation (DAE) model has been formulated to represent main plant units, such as shell and tube heat exchangers, high-pressure separator and demethanizing column. In the shell and tube heat exchangers, the hot stream partially condenses and equations to consider the partial condensation of the fluids have been included. A rigorous index one model for the demethanizing column has been developed. The DAE optimisation problem is solved with a simultaneous approach, in which both state and control variables are discretised and the original DAE optimisation model is transformed into a large-scale nonlinear problem (NLP), which is solved using Sequential Quadratic Programming (SQP) methods. Optimal profiles have been obtained for main operating variables to achieve an enhanced product recovery