Freezing-Based Acid Gas Removal and Its Integration with the Cold Section in an LNG Plant

Abstract

Natural gas (NG) feed undergoes a series of liquefaction and upgradation processes to produce the final liquefied natural gas (LNG) product that meets customer specifications. LNG processes have a significant capital investment and a high energy requirement, and hence many researchers have focused on process improvement and optimization. While much of the previous research has concentrated on the development of more energy-efficient processes (such as acid gas removal unit (AGRU), liquefaction, natural gas liquid (NGL) recovery, and nitrogen removal), reducing the energy consumption of the whole LNG plant has received little attention. Moreover, the power needs of the LNG plant and LNG product and fuel gas quality constraints remain briefly addressed. The present work proposes an integration between the acid gas freezing unit (FAGRU) with the cold section and suggests multiple structural changes to the cold section. The results showcase that the proposed integration and structural design changes lower the total energy requirement by 16.6% and increase the production rate by 60 kt/a (1.76%). Both these reduce specific energy consumption (SEC) by 17.98%. The feed-to-fuel (FFF) ratio decreases from 6.94% for the base process to 5.7% for the integrated process.