The High Pressure Expander Process Technology for LNG Applications

Abstract

Recent focus of the LNG industry has been on developing technologies to decrease capital investment and increase operational efficiency to reduce overall cost of supply. Pursuing this target, a novel, compact, and high efficiency expander-based liquefaction technology has been developed to monetize gas assets. The technology uses a single phase methane refrigerant stream operating at distinguishingly high pressures followed by a single phase nitrogen refrigerant stream. Such a configuration dramatically improves energy efficiency (by 10 - 25 %) and train production capacity (by 100 - 150%) compared to other expander-based technologies, while maintaining process simplicity, lower equipment count, and lighter weight relative to mixed-refrigerant based liquefaction processes. Furthermore, integrating with a front-end heavy hydrocarbon removal unit, the technology also enables standardized liquefaction train design for a wide range of gas composition around a nominal train capacity. The standard design is well suited for parallel train configurations and phased development philosophy to drive design and execution efficiency. In addition to CAPEX savings, the weight and footprint savings are beneficial in locations where space is at a premium. While the technology platform is broadly applicable for both offshore and onshore opportunities, this paper will focus on a recent offshore LNG project which showcased the technology's significant benefit in CAPEX, weight, footprint, personnel safety, insensitivity to ocean motion, refrigerant handling and many other operation advantages. It even enabled production capacity increase from 3.5 to 4.6 on the same circular hull floating facility, proving itself as a game changer to reduce cost of supply of this liquefaction project.