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LNG Freeze-out and implications to electrical drive.

Number: 74

Author(s) : VOVARD S., GOURIOU J.

Summary

In LNG plants, cryogenic distillation is commonly used to separate heavy hydrocarbons. The lighter hydrocarbons, rich in methane, are liquefied in the Main Cryogenic Heat Exchanger (MCHE, usually a Coil Wound type Heat Exchanger) at around -161°C. With the current trend of LNG plant electrification, the lightest components such as nitrogen cannot be sent to the fuel gas network traditionally firing gas turbines and tend to accumulate in the LNG. Electrification thus requires the addition of Nitrogen Removal Unit (NRU), where temperature can drop to -192°C. At this extremely low temperature, the risk of crystallization of trace components in the LNG is amplified.
Unwanted carry-over of heavy hydrocarbons can cause impurities to freeze out in various parts of the plant, including Natural Gas Liquids (NGL) Recovery unit, MCHE, NRU, or LNG tanks. This can reduce heat transfer efficiency and increase operational costs or cause blockages leading to
production bottlenecks or even unplanned shutdowns.
Traditional industry specifications based on C5+ and BTX (Benzene Toluene Xylene) concentrations, based on experimental solidification temperature in pure methane (mostly acquired by the Gas Processor Association, GPA), have been used since the 70’s to prevent freezing, but recent studies conducted by Technip Energies (T.EN) suggest these specifications may be insufficient or overly conservative depending on the plant feed gas composition.
Current commercial process simulators are not able to model SFE (solid-fluid equilibria, fluid either gas or liquid) accurately and the behavior of solid formers (impurities) in the LNG is not well known.
Over the past decade, T.EN has gathered experimental data on freeze-out with methane-rich mixtures, studied the impact of lighter and heavier components on CO2 solidification in methane, and evaluated the solubility effects of various potential solid formers. In particular, the below multicomponent systems behaviors have been studied:
• Impact of the addition of lighter (hydrogen or nitrogen) or heavier (ethane, propane) components on the solidification of CO2 in methane.
• Effect (inhibition or enhancement) of a potential solid former (CO2, benzene, p-xylene and neopentane) on the solubility of a second one in methane.
This paper summarizes the experimental and modelling work since the 70’s, highlights Technip Energies' recent research projects, and evaluates existing thermodynamic tools used in LNG projects to predict freeze-out, focusing on NGL Recovery and NRU.

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Details

  • Original title: LNG Freeze-out and implications to electrical drive.
  • Record ID : 30034687
  • Languages: English
  • Subject: Technology
  • Source: 21st International Conference & Exhibition on Liquefied Natural Gas (LNG2026)
  • Publication date: 2026/02/05

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