Feasibility analysis on the application of centrifugal BOG compressor at large LNG terminals

Abstract

[Objective] The development of new LNG terminals in China is currently oriented in the direction of large-scale construction while the existing LNG terminals are already undergoing expansion. Consequently, these terminals are generating an increasing volume of boil-off gas(BOG), with a substantial portion as stable sources, providing a promising opportunity for the application of centrifugal BOG compressors at these LNG terminals. [Methods] In this paper, an expanded LNG terminal in China was taken as the study subject.Its total generation and stable generation of BOG were calculated. A systematic study was performed to explore the feasibility of the widespread application of centrifugal BOG compressors at LNG terminals in China, from various perspectives, including the configuration principles of centrifugal compressors and reciprocating compressors, crucial factors in their parallel operation, and the advantages of centrifugal compressors. [Results] (1) Centrifugal compressors are suitable for application at new or expanded terminals furnished with either five LNG tanks of 16×104 m3 or four LNG tanks of 22×104 m3.(2) Implementing a configuration that combines a centrifugal compressor to handle the base load of BOG generation and a reciprocating compressor to handle the peak load of BOG generation ensures steady operation at the terminals.(3) When centrifugal and reciprocating compressors are in parallel operation, it is crucial to incorporate a buffer tank at the outlet of the reciprocating compressor, in order to mitigate the impact of pressure pulsations at its outlet on the centrifugal compressor.(4) In the same parallel operation mode, it is recommended to reduce the fluctuation range of discharge pressure at the reciprocating compressor's outlet, to reduce the influence of pressure pulsation on the downstream BOG recondenser. [Conclusion] These research findings serve as theoretical guidance and technical support for the application promotion of centrifugal compressors at LNG stations in China, their parallel operation with reciprocating compressors, and relevant engineering design.

Keywords

• lng terminal
• centrifugal bog compressor
• reciprocating bog compressor
• parallel operation
• base load
• peak load
• recondenser