(186a) Process Design of Acid Gas Removal Units Considering Liquid Mal-Distribution of Columns for LNG-FPSO Applications

Due to increase in the exploration of natural gas in remote areas, the design of gas processing plants on offshore FPSO (Floating Production Storage & Offloading) platforms is gaining attention. Natural gas extracted from these gas wells includes impurities, such as acid gases, water and mercury. Acid gases must be removed before liquefaction and other downstream processing, because of potential corrosion and freezing issues. AGRUs (Acid Gas Removal Units) using amine-based solvent are commonly used in industries to remove acid cases, which is the main focus of this presentation.

Although AGRUs are well established technologies for on-shore applications, there is still a lack of technical confidence when these technologies are applied for offshore plants which are influenced by ship motion and oceanic environment. Therefore, systematic design methodology is necessary to address ship and ocean effects during the process design of offshore AGRUs.

This study aims to provide cost-effective and reliable process design for AGRUs through the application of system-wide analysis and process optimization techniques, which allow systematic evaluation of key design variables and structural options. As operating absorber and regenerator columns in a tilted position results in a negative impact on their performance, the design of these systems should consider flow mal-distribution inside columns and reflect its impact through over-sizing of equipment. Also, opportunities for improving process performance and energy efficiency should be systematically identified.

Process modeling is carried out using commercial process simulators (e.g. AspenHYSYS^®, UniSim^® or ProMax^®), which are integrated with optimization algorithms such as GA (genetic algorithm) in MATLAB^®. A superstructure-based approach is used to identify the most appropriate configuration of AGRUs when introduction of semi-lean streams, multiple lean solvent feeds and pump-around options are screened, while operating conditions and design variables are simultaneously determined in a holistic manner.

A case study is presented to demonstrate how the ocean effects can be effectively and systematically considered for the design of AGRUs for LNG-FPSO applications.

Acknowledgement

This research was supported by a grant from the GAS Plant R&D Center funded by the Ministry of Land, Infrastructure and Transport (MOLIT) of the Korean government.