Hydrocarbon recovery from fuel gas
AssigneeAir Products and Chemicals, Inc.
InventorsDavid M. Nicholas, Thomas M. Roden, Gerry N. Gottier
Life of this patent
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Abstract
High purity methane is recovered from a fuel gas stream containing the same in admixture with mainly nitrogen and carbon dioxide, by first removing the carbon dioxide by selective adsorption in a PSA system and separating the remaining nitrogen from the methane by cryogenic distillation, the rejected nitrogen being employed for purging the CO.sub.2 -laden adsorbent beds of the PSA system. Cyclic regeneration of the sorbent-laden bed may entail nitrogen purge with or without including a carbon dioxide rinse, or the nitrogen purge of the sorbent-laden bed may be used in combination with pressure let-down by gas withdrawal into one or more companion beds.
Claims8
The method of recovering methane from a fuel gas mixture containing also nitrogen and carbon dioxide, which comprises the steps of:
- (a) passing said fuel gas mixture at superatmospheric pressure through a bed of adsorbent wherein carbon dioxide is selectively adsorbed while withdrawing from said bed a stream comprised of unadsorbed components including methane and nitrogen;
- (b) subjecting said stream to cryogenic distillation to separate substantially all of the nitrogen therefrom and recovering as product methane of high purity;
- (c) rinsing said bed of step (a) with a stream of carbon dioxide passed through the bed in a direction co-current to that employed in initial introduction of said fuel gas mixture in step (a);
- (d) recycling at least a part of the effluent obtained during said rinse of step (c) as a component of the feed gas mixture subjected to step (a);
- (e) reducing the pressure in the bed of step (a);
- (f) utilizing at least part of the nitrogen separated in step (b) above to purge from the bed carbon dioxide retained therein during step (a);
- and
- (g) repressurizing said bed of step (a) with a stream of unadsorbed components having the composition of that withdrawn during step (a).
Dependencies are inferred from the claim text.