Simulation based Heuristics Approach for Plantwide Control of Propane Precooled Mixed Refrigerant in Natural Gas Liquefaction Process

Abstract In this paper a simulation based heuristic approach is used to configure the control structure of propane precooled mixed refrigerant (MR) natural gas (NG) liquefaction process. The liquefaction of NG in cryogenic exchanger involves MR stream condensation and vaporization in different sections of cryogenic exchanger. This increases the interactions among MR streams as illustrated using dynamic simulation. To identify these interactions, first the sensitivity analysis of propane precooled MR was carried out and then several heuristic based on dynamic simulation were proposed for disturbance rejection and increased liquefied natural gas (LNG) production rate. Major findings from several case studies suggest that the maximization of available cold energy is possible by utilizing temperature difference between MR streams as set point for controlling LNG production rate.