LNG Applications for Turbomachinery

Abstract Global natural gas consumption has been rising over the past decades. While natural gas is usually transported over large distances via pipelines, liquefying the gas allows transport in tanker ships across oceans, making natural gas a fungible commodity. Thus it allows a worldwide gas trading market, and enhances supply security. Liquefying natural gas significantly increases the energy density, and allows transport at low, near atmospheric pressures. Liquefaction is accomplished by cooling the natural gas. Because the liquefaction process is very energy intensive, it has led to advanced refrigeration processes, using advances in process design and turbomachinery, both for the compressors needed for refrigeration, as well as their drivers, such as steam turbines drives, gas turbine or large synchronous electric motors. This paper discusses the current refrigeration processes which typically either involve vapor compression processes, often with several loops of integrated refrigeration cycles, and reverse Brayton cycles. The cycle complexity is often determined by balancing capital expenditures and operating expenses. The compressors need to be match to drivers. This impacts control methods, both for anti surge control and for capacity control and starting complexity, as some drivers offer the capability to vary the compressor speed. The paper specifically discusses features of the specific turbomachinery required to produce liquefied natural gas.