Constraint Formulations for Optimisation of Dual Mixed Refrigerant LNG Processes

Abstract

Optimisation of a dual mixed refrigerant LNG process is challenging due to its rather complex structure. Therefore, appropriate constraint formulations are essential to solve the optimisation problem. In this paper, the AP-DMR process was optimised to minimize the power consumption with different constraints in order to find proper constraint formulations. The case studies indicate that refrigerant superheating does not always increase the power consumption. Instead, the best-known solutions required specific values of refrigerant superheating. Moreover, maximum heat exchanger area constraints for cryogenic heat exchangers delivered higher energy efficiency, compared to the constraints of minimum temperature difference, which is common practice for LNG processes.