Process for purifying natural gas
First Claim
1. A process for separating water and carbon dioxide from a feedstream comprising hydrocarbons, water and carbon dioxide, said process comprising the steps of:
- (a) passing the feedstream to a first adsorption zone containing a solid adsorbent having selectivity for water at a first zone adsorption temperature effective to adsorb water and a first zone adsorption pressure and withdrawing a first zone adsorption effluent stream having a reduced concentration of water relative to the feedstream;
(b) passing at least a portion of the first zone adsorption effluent stream to a second adsorption zone containing a solid adsorbent having selectivity for carbon dioxide at a second zone adsorption temperature effective to adsorb carbon dioxide and a second zone adsorption pressure, said second zone adsorption temperature being lower than said first zone adsorption temperature, and withdrawing a second zone adsorption effluent stream having a reduced concentration of carbon dioxide relative to the first effluent stream;
(c) passing a first purge gas through the first adsorption zone at a first zone regeneration temperature effective to desorb water from the first adsorption zone and a first zone regeneration pressure and withdrawing a first zone desorption effluent stream comprising water; and
(d) passing a second purge gas through the second adsorption zone at a second zone regeneration temperature of at least 250°
F. and effective to desorb carbon dioxide from the second adsorption zone and a second zone regeneration pressure, said second zone regeneration pressure being not lower than about 50 psia, and withdrawing a second zone desorption effluent stream comprising carbon dioxide.
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Abstract
Processes are disclosed for separating water and carbon dioxide from hydrocarbon streams, e.g., natural gas, by adsorption prior to low temperature hydrocarbon processing operations, e.g., liquid natural gas recovery and nitrogen rejection. The processes employ separate adsorption zones for the water and carbon dioxide adsorption and both adsorption zones are operated with a thermal swing adsorption cycle. A product gas from the low temperature processing operation, e.g., methane, can be used as the purge gas for one or both adsorption zones and the desorbed water and carbon dioxide, along with the purge gas can be recovered and introduced into a natural gas pipeline, for example.
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Citations
26 Claims
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1. A process for separating water and carbon dioxide from a feedstream comprising hydrocarbons, water and carbon dioxide, said process comprising the steps of:
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(a) passing the feedstream to a first adsorption zone containing a solid adsorbent having selectivity for water at a first zone adsorption temperature effective to adsorb water and a first zone adsorption pressure and withdrawing a first zone adsorption effluent stream having a reduced concentration of water relative to the feedstream; (b) passing at least a portion of the first zone adsorption effluent stream to a second adsorption zone containing a solid adsorbent having selectivity for carbon dioxide at a second zone adsorption temperature effective to adsorb carbon dioxide and a second zone adsorption pressure, said second zone adsorption temperature being lower than said first zone adsorption temperature, and withdrawing a second zone adsorption effluent stream having a reduced concentration of carbon dioxide relative to the first effluent stream; (c) passing a first purge gas through the first adsorption zone at a first zone regeneration temperature effective to desorb water from the first adsorption zone and a first zone regeneration pressure and withdrawing a first zone desorption effluent stream comprising water; and (d) passing a second purge gas through the second adsorption zone at a second zone regeneration temperature of at least 250°
F. and effective to desorb carbon dioxide from the second adsorption zone and a second zone regeneration pressure, said second zone regeneration pressure being not lower than about 50 psia, and withdrawing a second zone desorption effluent stream comprising carbon dioxide. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A process for separating water and carbon dioxide from a natural gas feedstream comprising said water, said carbon dioxide, methane, at least one other hydrocarbon selected from ethane, propane, butanes, pentanes and hexanes, and at least one light gas selected from nitrogen, helium, argon, oxygen and hydrogen, said process comprising:
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(a) passing the feedstream to a first adsorption zone containing a solid adsorbent having selectivity for water at a first zone adsorption temperature effective to adsorb water and a first zone adsorption pressure and withdrawing a first zone adsorption effluent stream having a reduced concentration of water relative to the feedstream; (b) passing at least a portion of the first zone adsorption effluent stream to a second adsorption zone containing a solid adsorbent having selectivity for carbon dioxide at a second zone adsorption temperature effective to absorb carbon dioxide and a second zone adsorption pressure, said second zone adsorption temperature being lower than said first zone adsorption temperature, and withdrawing a second zone adsorption effluent stream having a reduced concentration of carbon dioxide relative to the first effluent stream; (c) separating at least a portion of the second effluent stream into a raw product gas stream comprising methane and a rejection stream comprising said at least one light gas; (d) passing a first purge gas comprising a portion of the raw product gas to the first adsorption zone at a first zone regeneration temperature effective to desorb water from the first adsorption zone and a first zone regeneration pressure and withdrawing a first zone desorption effluent stream comprising water; (e) passing a second purge gas comprising a portion of the raw product gas to the second adsorption zone at a second zone regeneration temperature of at least 250°
F. and effective to desorb carbon dioxide from the second adsorption zone and a second zone regeneration pressure, said second zone regeneration pressure being not lower than about 50 psia, and withdrawing a second zone desorption effluent stream comprising carbon dioxide; and(f) combining the first zone desorption effluent with the remaining portion of the raw product gas to provide a combined product gas rich in methane. - View Dependent Claims (23, 24, 25, 26)
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Specification