Separation of CO
Processes for separating carbon dioxide from a gas mixture that comprises CO 2 and N 2 that are based upon formation of gas hydrates, and systems useful for implementing such processes, are disclosed.
1. A process for purifying CO 2 from a gas comprising N 2 , the process comprising intimately contacting a feed gas stream comprising CO 2 and N 2 gases and an aqueous phase stream in a countercurrent flow to form a CO 2 -rich hydrate in the aqueous phase, a temperature T f being maintained at a gas feed stage f in the countercurrent flow, a temperature T 2 such that T 2 <T f being maintained at a stage n>f, and a temperature T 1 being maintained at a stage m≤f such that T 1 ≥T f ;
wherein:
T 2 is in a range from an incipient vapor temperature for CO 2 to an incipient hydrate temperature for CO 2 at an operating pressure of the process, and
T 1 is a temperature at or below a temperature of convergence of the incipient CO 2 hydrate formation and incipient CO 2 vapor formation curves at the operating pressure of the process.
2. The process of claim 1 , further comprising separating a gas phase from the aqueous phase stream and collecting a hydrate slurry formed in the aqueous phase and comprising hydrate particles enriched in CO 2 .
3. The process of claim 2 , further comprising concentrating the CO 2 -rich hydrate from the hydrate slurry and sequestering the hydrate.
4. The process of claim 3 , in which the hydrate is sequestered on deep ocean floor or buried in sea floor, or in which the hydrate is encapsulated.
5. The process of claim 1 , further comprising collecting a N 2 -rich gas from a gas stream after contact with the aqueous phase.
6. The process of claim 2 , further comprising collecting a N 2 -rich gas from the separated gas.
7. The process of claim 6 that is conducted at 2200 psia, T 2 is from 31 to 34° F. (−0.5 to 1.1° C.) and T 1 is about 54° F. (12.2° C.).
8. The process of claim 6 , in which there are 3 stages and T f is about 33° F. (0.5° C.), T 1 is about 35° F. (1.6° C.) and T 2 is about 31° F. (−0.5° C.).
9. The process of claim 1 , in which the feed gas stream comprises a hydrate promoter.
10. The process of claim 1 , in which the aqueous phase stream comprises a hydrate promoter.
11. The process of claim 9 , in which the aqueous phase stream comprises a hydrate promoter.