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Natural gas enrichment process

  • US 5,536,300 A
  • Filed: 10/21/1994
  • Issued: 07/16/1996
  • Est. Priority Date: 10/21/1994
  • Status: Expired due to Term
First Claim
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1. A method for purifying a gas stream containing primarily hydrocarbon gases and nitrogen by flowing said gas stream through a plurality of adsorbent beds each containing an adsorbent which selectively adsorbs said hydrocarbon gases with said nitrogen gas substantially passing therethrough, cycling each of said adsorbent beds sequentially through a series of phases comprising an adsorption phase, a recycle phase, a depressurization phase, an evacuation phase, a nitrogen pressurization phase and a recycle feed pressurization phase, said adsorption phase comprising passing said gas stream into a first adsorbent bed at an elevated pressure for a first part of a first period of time with said hydrocarbon gases being adsorbed therein and collecting a portion of said nitrogen gas substantially passing therethrough for use in pressurizing an adsorbent bed that is to enter said adsorption phase, while said first adsorbent bed is in said adsorption phase depressurizing a third adsorbent bed in said depressurization phase to a first lower pressure to produce a depressurization gas and passing said depressurization gas through a fourth adsorbent bed in said recycle phase and collecting a recycle feed gas therefrom for use at least in further pressurizing an adsorbent bed that is to enter said adsorption phase, and evacuating a second adsorbent bed in said evacuation phase to a lowest pressure and recovering a hydrocarbon gas product containing substantially hydrocarbon gases, said first adsorbent bed prior to undergoing said adsorption phase being repressurized with a portion of said nitrogen gas in said nitrogen pressurization phase and then with a portion of said recycle feed gas in said recycle feed pressurization phase.

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