Cryogenic system for removing acid gases from a hydrocarbon gas stream, and method of removing acid gases

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

• providing a cryogenic distillation tower, the tower having a lower distillation zone and an intermediate controlled freezing zone that receives a cold liquid spray comprised primarily of methane;
• receiving the raw gas stream into the cryogenic distillation tower;
• separating the raw gas stream in the cryogenic distillation tower into an overhead methane stream and a bottom acid gas 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 first portion of the cooled overhead methane stream to the cryogenic distillation tower as liquid reflux to serve as the cold liquid spray;
• passing a second portion of the cooled overhead methane stream through a first solid adsorbent bed downstream of the cryogenic distillation tower so as to remove additional acid gases comprising a first contaminant and to generate a polished gas stream;
• producing, with the refrigeration system, the liquid reflux at a sufficient quantity as to remove acid gases from the raw gas stream within the cryogenic distillation tower down to a first selected composition, and delivering the overhead methane stream to the first solid adsorbent bed downstream of the cryogenic distillation tower to remove additional acid gases down to a second selected composition;
• at least partially dehydrating the raw gas stream by passing the raw gas stream through a second solid adsorbent bed upstream of the cryogenic distillation tower to remove a second contaminant, wherein the first solid adsorbent bed downstream of the cryogenic distillation tower and the second solid adsorbent bed upstream of the cryogenic distillation tower are each molecular sieve beds;
• and
• saturating the second solid adsorbent bed upstream of the cryogenic distillation tower with adsorbed water and replacing the second solid adsorbent bed upstream of the cryogenic distillation tower with the molecular sieve bed of the first solid adsorbent bed that has become saturated with acid gas through use as the second solid adsorbent bed downstream of the cryogenic distillation tower, wherein saturating the second solid adsorbent bed upstream of the cryogenic distillation tower with adsorbed water at least partially displaces acid gas components from the second solid adsorbent bed that were adsorbed while the second solid adsorbent bed was in service downstream of the cryogenic distillation tower.

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

• providing a cryogenic distillation tower, the tower having a lower distillation zone and an intermediate controlled freezing zone that receives a cold liquid spray comprised primarily of methane;
• receiving the raw gas stream into the cryogenic distillation tower;
• separating the raw gas stream in the cryogenic distillation tower into an overhead methane stream and a bottom acid gas 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 first portion of the cooled overhead methane stream to the cryogenic distillation tower as liquid reflux to serve as the cold liquid spray;
• passing a second portion of the cooled overhead methane stream through a first solid adsorbent bed downstream of the cryogenic distillation tower so as to remove additional acid gases and to generate a polished gas stream;
• producing, in the refrigeration system, liquid reflux at a sufficient quantity as to remove acid gases from the raw gas stream within the cryogenic distillation tower down to a first selected composition, and delivering the overhead methane stream to the first solid adsorbent bed downstream of the cryogenic distillation tower to remove additional acid gases down to a second selected composition, wherein;
• the acid gases comprises a first contaminant,
• the first contaminant is carbon dioxide,
• generating the quantity of the liquid reflux is sufficient to remove carbon dioxide from the raw gas stream down to a first composition of about 1 to 4 mol. percent, and
• removing additional carbon dioxide from the overhead methane stream down to a second composition of about 0.2 to 3.0 mol. percent in the first solid adsorbent bed downstream of the cryogenic distillation tower;
• at least partially dehydrating the raw gas stream by passing the raw gas stream through a second solid adsorbent bed upstream of the cryogenic distillation tower and removing a second contaminant, wherein the second contaminant is water;
• replacing the second solid adsorbent bed upstream of the cryogenic distillation tower with a molecular sieve bed that has become saturated with acid gas through use as the first solid adsorbent bed downstream of the cryogenic distillation tower;
• and
• at least partially displacing acid gas components from the first solid adsorbent bed upstream of the cryogenic distillation tower by saturating the first solid adsorbent bed upstream of the cryogenic distillation tower with adsorbed water.

A method for removing acid gases from a raw gas stream, further comprising:

• providing a cryogenic distillation tower, the tower having a lower distillation zone and an intermediate controlled freezing zone that receives a cold liquid spray comprised primarily of methane;
• receiving the raw gas stream into the cryogenic distillation tower;
• separating the raw gas stream in the cryogenic distillation tower into an overhead methane stream and a bottom acid gas 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 first portion of the cooled overhead methane stream to the cryogenic distillation tower as liquid reflux to serve as the cold liquid spray;
• passing a second portion of the cooled overhead methane stream through a first solid adsorbent bed downstream of the cryogenic distillation tower so as to remove additional acid gases and to generate a polished gas stream;
• producing, with the refrigeration system, liquid reflux at a sufficient quantity as to remove acid gases from the raw gas stream within the cryogenic distillation tower down to a first selected composition, and delivering the overhead methane stream to the first solid adsorbent bed downstream of the cryogenic distillation tower to remove additional acid gases down to a second selected composition, wherein
• the acid gases comprise a first contaminant;
• the first contaminant is carbon dioxide,
• generating the quantity of the liquid reflux is sufficient to remove carbon dioxide from the raw gas stream down to a first composition of about 1 to 4 mol. percent, and
• removing additional carbon dioxide from the overhead methane stream down to a second composition of about 0.2 to 3.0 mol. percent in the first solid adsorbent bed downstream of the cryogenic distillation tower;
• injecting at least a portion of the bottom acid gas stream into a subsurface formation through at least one acid gas injection well;
• at least partially dehydrating the raw gas stream by passing the raw gas stream through a second solid adsorbent bed upstream of the cryogenic distillation tower and removing a second contaminant, wherein the second contaminant is water, and wherein the first solid adsorbent bed downstream of the cryogenic distillation tower is a molecular sieve bend and the second solid adsorbent bed upstream of the cryogenic distillation tower is a molecular sieve bed;
• and
• saturating the molecular sieve bed upstream of the cryogenic distillation tower with adsorbed water and replacing the molecular sieve bed upstream of the cryogenic distillation tower with the molecular sieve bed downstream of the cryogenic distillation tower that has become saturated with acid gas through use as the first solid adsorbent bed downstream of the cryogenic distillation tower.