Fundamentals of a Single Stage Liquid Expander for High Pressure Ratios

In the Industrial Gas industry liquid expanders have been successfully running for over a decade. They are operating with liquid nitrogen or liquid air in air separation plants and are installed in parallel to Joule-Thomson valves. These liquid expanders are based on the radial inflow turbine technology. They have a design temperature of -196°C and a design pressure of 80 barg. Surprisingly in the Oil&Gas and LNG industry the liquid expanders that are operating today are all based on the design of reverse running multistage pumps. This paper presents liquid expanders based on radial inflow turbine technology promoting their application also in the Oil&Gas and LNG industry and outlines their specific advantages and disadvantages. The paper shows that liquid expanders, contrary to reverse pumps, can deal with pressure ratios of 40:1 and more in a single stage. The paper argues that fundamentally a single stage machine is to be preferred over a multistage machine.