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Innovative nitrogen rejection solutions for LNG and gas infrastructure.

Numéro : 83

Auteurs : BUB A., SABATIER F., SCHIEWE T.

Résumé

Nitrogen is widely considered as ballast in natural gas and hydrocarbon rich fuel gas streams, necessitating precise management to adhere to operational and safety standards.
Natural gas pipeline specifications typically limit the nitrogen content to a maximum of 3 mol% to ensure product quality and proper functionality of end-user equipment, e.g. burners. Similarly, fuel gas used for gas turbines requires strict nitrogen management to stabilize the Wobbe index and maintain reliable turbine performance.
In LNG production, nitrogen concentrations exceeding 1 mol% in the product present significant risks of tank stratification due to varying liquid densities, which could trigger the dangerous "rollover" effect, resulting in large methane vapor releases and potentially compromising the structural integrity of flat-bottom tanks. For avoidance of this safety hazard an NRU can either be implemented upstream of the LNG plant in the feed gas pipeline or downstream of the liquefaction section. An example of such downstream NRU is shown in Fig. 1, illustrating the process module next to the tall cold box as the major components of the installation.
Furthermore, nitrogen rejection is seamlessly integrated with end-flash gas (EFG) and boil-off gas (BOG) re-liquefaction processes, essential for the electrification of LNG facilities. This approach not only enhances valuable LNG product output of an existing facility but also aligns with the global transition toward sustainable LNG production.
An additional capability of NRU systems is the integrated helium extraction from nitrogen-rich endflash gas streams in LNG plants. Helium, a highly valuable commodity, can be recovered with minimal energy input due to the optimized nitrogen rejection setup, providing a supplementary
revenue source for LNG operators. Fig. 2 displays the main components of a helium recovery unit at an LNG plant in Skikda, Algeria. In the background the NRU cold box and in front of it the PSA unit for helium purification.
Nitrogen Rejection Units (NRU) offer an efficient and robust solution for nitrogen removal across the diverse applications mentioned above. The poster presents the main technical concepts available with their characteristics as well as the pros and cons. While for low methane product purity requirements and small plant capacities below approx. 20 mmscfd membrane-based concepts are usually applied, high methane purity demand and/or large plant capacities are typically addressed by cryogenic gas separation processes, the latter being the focus of the poster.
 

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Détails

  • Titre original : Innovative nitrogen rejection solutions for LNG and gas infrastructure.
  • Identifiant de la fiche : 30034696
  • Langues : Anglais
  • Sujet : Technologie
  • Source : 21st International Conference & Exhibition on Liquefied Natural Gas (LNG2026)
  • Date d'édition : 05/02/2026

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