FEASIBLE OPERATING REGION OF NATURAL-GAS PLANTS UNDER FEED PERTURBATIONS

The main objective of this work is to find the set of scenarios for va riable feed conditions which the plant can accommodate operating in th e feasible region. A rigorous simulation of the natural gas plant has been implemented. The solubility of carbon dioxide in mixtures of ligh t hydrocarbons is predicted Carbon dioxide solidification in the colde st sectors of the plant is not desired. Therefore a constraint for eac h of the top plates of the demethanizer column is added, in such a way that the operating conditions are chosen to avoid freezing conditions . The nominal point that represents the normal feed conditions is know n. The maximum displacements from the nominal point, in different dire ctions of the uncertain space, are found solving a nonlinear programmi ng problem. The main operating conditions of the plant are the optimiz ation variables. In the numerical example presented, the carbon dioxid e and methane feed flowrate are assumed as uncertain parameters. The m inimum of the maximum displacement from the nominal point is found The corresponding direction and active constraints which limit the flexib ility are reported The feasible region in the two dimensional space is found. (C) 1998 Elsevier Science Ltd. All rights reserved.