Cryogenic system for removing acid gases from a hydrocarbon gas stream

1. A method for removing acid gases from a dehydrated raw gas stream, comprising:

providing a cryogenic distillation tower, the tower having a controlled freezing zone that receives a cold liquid spray comprised primarily of methane, and a collector tray below the controlled freezing zone;

injecting the raw gas stream into the cryogenic distillation tower;

chilling the raw gas stream so as to cause carbon dioxide within the raw gas stream to precipitate upon the collector tray as a slurry, while allowing methane to vaporize and exit the cryogenic distillation tower as an overhead methane stream;

passing the overhead methane stream through a refrigeration system downstream of the cryogenic distillation tower, the refrigeration system cooling the overhead methane stream;

returning a portion of the cooled overhead methane stream to the cryogenic distillation tower as liquid reflux to serve as the cold liquid spray;

removing the slurry from the cryogenic distillation tower;

separating the slurry into a solid material comprised primarily of carbon dioxide, and a liquid material comprising methane, said separating step comprising passing the slurry through a first filter, thereby producing a first filter cake comprising the solid material, and a first filtrate comprising the liquid material, and wherein the first filtrate further comprises methane and carbon dioxide, in liquid phase;

warming solid material taken primarily from the first filter cake to produce a carbon dioxide stream, in liquid phase, wherein the liquid carbon dioxide stream comprises a portion of the carbon dioxide stream; and

returning at least a portion of the liquid material to the cryogenic distillation tower.

2. The method of claim 1 , wherein:

the collector tray comprises a downcomer into which the precipitated slurry falls; and

the collector tray directs the slurry out of the cryogenic distillation tower (i) by gravitational flow, (ii) by operation of a mechanical translation device, (iii) by aid of spraying a portion of the cold liquid spray into the collector tray and against the slurry, or (iv) by combinations thereof.

3. The method of claim 1 , wherein:

the cryogenic distillation tower further comprises an upper rectification zone above the controlled freezing zone, and a lower distillation zone below the controlled freezing zone; and

the raw gas stream is injected into the lower distillation zone;

and further comprising releasing a bottoms stream from the lower distillation zone, the bottoms stream comprising acid gases in liquid phase; and

wherein returning at least a portion of the liquid material to the cryogenic distillation tower comprises delivering the liquid material to the lower distillation zone.

4. The method of claim 1 , wherein said separating step further comprises:

rinsing the first filter cake using a liquid carbon dioxide stream;

mixing the first filter cake with the liquid carbon dioxide stream to produce a first solid-liquid slurry; and

delivering the first solid-liquid slurry to a second filter, thereby producing a second filter cake comprised primarily of solid carbon dioxide, and a second filtrate comprising methane, in liquid phase.

5. The method of claim 4 ,

further comprising combining the first filtrate and the second filtrate; and

wherein the liquid material that is returned to the lower distillation zone comprises the combined first filtrate and second filtrate.

6. The method of claim 5 , further comprising:

rinsing the second filter cake using the liquid carbon dioxide stream;

mixing the second filter cake to produce a solid-liquid slurry; and

delivering the solid-liquid slurry to a third filter, thereby producing a third filter cake comprised primarily of solid carbon dioxide, and a third filtrate comprising methane, in liquid phase.

7. The method of claim 1 , wherein the warming comprises passing slurry taken from the first filter cake through a heat exchanger such that heat is exchanged with the raw gas stream.

8. The method of claim 1 , wherein the first filter comprises a porous medium or a centrifuge.

9. The method of claim 1 , wherein the step of returning at least a portion of the liquid material to the cryogenic distillation tower comprises injecting the first filtrate directly back into the controlled freezing zone.

10. The method of claim 6 , further comprising:

combining the second filtrate and the third filtrate;

injecting the second filtrate and the third filtrate into a distillation separator, thereby producing a bottoms liquid stream comprised primarily of carbon dioxide, in liquid phase, and a recovery methane stream; and

combining the overhead methane stream from the cryogenic distillation tower with the recovery methane stream.

11. The method of claim 2 , wherein the collector tray is inclined towards the downcomer to direct the slurry into the downcomer.