Separating carbon dioxide and hydrogen from a multicomponent gaseous stream
A system and a method separating CO 2 from a gas mixture using hydrates are provided. An exemplary method includes injecting a feed gas into a gas hydrate column through a feed gas line and producing hydrogen from a hydrogen outlet line. The method includes determining that water on trays in the gas hydrate column is saturated with CO 2 gas hydrates, closing valves on the feed gas line and the hydrogen outlet line, opening a valve leading to a carbon dioxide outlet line, lowering pressure in the gas hydrate column, and producing carbon dioxide from the carbon dioxide outlet line.
1 . A gas hydrate column, comprising:
a column shell to be pressurized in a first stage of operation and depressurized in a second stage of operation;
bubble trays disposed vertically in the column shell, wherein the bubble trays are configured to hold a level of water on each of the bubble trays;
a feed gas inlet to feed a gas mixture into the column shell, where in the gas mixture is compressed and chilled to form CO 2 hydrates in the water on the bubble trays;
a gas outlet to release non-hydrate forming gases during the first stage of operation; and
a gas outlet to release hydrate-forming gases during the second stage of operation.
2 . The gas hydrate column of claim 1 , comprising:
a water inlet disposed at a top of the column shell; and
a water outlet disposed at a bottom of the column shell.
3 . The gas hydrate column of claim 2 , wherein water introduced into the water inlet comprises a CO 2 hydrate promoter.
4 . The gas hydrate column of claim 3 , wherein the CO 2 hydrate promoter comprises cyclopentane, tetrahydrofuran, or tetra-n-butylammonium bromide, or any combination thereof.
5 . The gas hydrate column of claim 3 , wherein the CO 2 hydrate promoter exits with water through the water outlet.
6 . The gas hydrate column of claim 5 , wherein the CO 2 hydrate promoter is recovered from the water exiting through the water outlet.
7 . The gas hydrate column of claim 1 , wherein the temperature of the column is between about 5° C. and about 10° C.
8 . The gas hydrate column of claim 1 , wherein, during the first stage of operation, the pressure of the gas hydrate column is between about 30 bar (3 megapascals, MPa) and about 42.5 bar (4.25 MPa).
9 . The gas hydrate column of claim 1 , wherein, during the second stage of operation, the pressure of the gas hydrate column is between about 0.1 bar and about 5 bar.
10 . The gas hydrate column of claim 1 , wherein a diameter to length ratio of the gas hydrate column is between about 2 and about 3.
11 . The gas hydrate column of claim 1 , wherein the gas mixture provided through the feed gas inlet is at a pressure of between about 30 bar and about 35 bar.
12 . The gas hydrate column of claim 1 , wherein the gas mixture provided through the feed gas inlet is at a temperature of between about 5° C. and about 8° C.
13 . The gas hydrate column of claim 1 , wherein the feed gas inlet is disposed below at least three bubble trays from the top of the gas hydrate column.
14 . A method for separating CO 2 from a gas mixture using hydrates, comprising:
injecting a feed gas into a gas hydrate column through a feed gas line;
producing hydrogen from a hydrogen outlet line;
determining that water on trays in the gas hydrate column is saturated with CO 2 gas hydrates;
closing valves on the feed gas line and the hydrogen outlet line;
opening a valve leading to a carbon dioxide outlet line;
lowering pressure in the gas hydrate column; and
producing carbon dioxide from the carbon dioxide outlet line.
15 . The method of claim 14 , comprising, after injecting the feed gas, injecting water into a water inlet line disposed proximate to the top of the gas hydrate column.
16 . The method of claim 15 , comprising mixing a hydrate formation promoter into the water prior to injection.
17 . The method of claim 14 , comprising recovering water from a water outlet line disposed proximate to the bottom of the gas hydrate column, wherein the water from the water outlet line is monitored to determine that the water on the trays in the gas hydrate column is saturated with CO 2 gas hydrates.
18 . The method of claim 16 , comprising recovering the hydrate formation promoter from the water recovered from the water outlet line.
19 . The method of claim 14 , comprising pressurizing the feed gas to between about 30 bar and about 35 bar.
20 . The method of claim 14 , comprising chilling the feed gas to between about 5° C. and about 15° C.
21 . The method of claim 14 , wherein the pressure in the gas hydrate column is lowered to between about 0.1 bar and 5 bar.
22 . The method of claim 14 , comprising:
determining that CO 2 has stopped flowing from the gas hydrate column;
closing the valve leading to the carbon dioxide outlet line;
opening the valves on the feed gas line at the hydrogen outlet line;
injecting the feed gas into the gas hydrate column through the feed gas line; and
producing hydrogen from the hydrogen outlet line.