Gas Processors Association Europe

Presented at GPA Europe Annual Conference, Prague, 21 - 23 September 2011

K. Hald and M. Langsholt, Institute for Energy Technology (IFE)

Conventional methods for producing LNG require a high degree of processing and thus infrastructure investments. To increase the viability of small and remote gas fields, a new process called LUWS, Liquefaction of Unprocessed Well-Stream, has been investigated theoretically and experimentally. The long-term vision of this process is to liquefy the well-stream “as is” in its entirety with only minimal pre-processing and pressure loss. The inherent pressure energy will be utilized for the cooling and liquefaction.  

The paper describes the results produced in a uniquely designed test-rig for expansion of natural gas, built to investigate the thermo-physical properties in a single-stage expander. The experiments consist in reproducing a non-equilibrium expansion process under realistic conditions, and to measure and quantify the phase change, particularly solid freeze-out, during the expansion. The calculated phase diagrams for the experiments gave very good concordance with the observations in the experiments. Freeze-out occurred in the cases where the phase envelope was penetrated. The amount of deposition on a cold surface depends on the gas composition, equipment type and distance to the surface in the expander. In a methane-carbon-dioxide mixture, the freeze-out deposition rate and thickness were successfully measured for different settings.