PSA process for recovery or ethylene
AssigneeUop LLC
InventorMichael J. Mitariten
Life of this patent
Estimating the term…
Abstract
A process is provided for the concentration and recovery of ethylene and heavier components from a hydrocarbon feedstream. A pressure swing adsorption (PSA) process is used to remove from hydrocarbon feedstream light cut comprising hydrogen, carbon monoxide, and methane and subsequently concentrate a heavy cut comprising the ethylene and heavy components in the PSA tail gas. In one aspect of the invention, an FCC off gas is separated into a light cut and a heavy cut and the heavy cut is routed to an ethylene plant. In another aspect of the invention, a C.sub.2 -rich stream is withdrawn from an ethylene plant and used to enhance the recovery of the ethylene and heavier stream in the PSA process and an ethylene-rich stream is returned to the ethylene plant.
Claims25
A pressure swing adsorption process for the concentration and recovery of a heavy cut comprising ethylene and heavier components from a hydrocarbon feedstream comprising a light cut and said heavy cut, said light cut comprising hydrogen and methane, said process comprising the following steps:
- (a) passing said hydrocarbon feedstream to an adsorption zone containing a solid adsorbent selective for the adsorption of said heavy cut, said adsorption zone having an adsorption zone pressure and an adsorption zone temperature in which at least a portion of the heavy cut is adsorbed and recovering a first adsorption zone effluent stream comprising said light cut;
- (b) cocurrently displacing said light cut contained within said adsorption zone with a displacement gas having a concentration of said heavy cut which is higher than that of said hydrocarbon feedstream and recovering a second adsorption zone effluent stream comprising said light cut;
- (c) cocurrently depressurizing said adsorption zone to an equalization pressure to provide an equalization gas to another adsorption zone undergoing repressurization;
- (d) further cocurrently depressurizing said adsorption zone to a start of blow-down pressure to provide a purge gas comprising said light cut;
- (e) countercurrently depressurizing said adsorption zone to a desorption pressure that is at or above atmospheric pressure and recovering a desorption effluent stream comprising said heavy cut;
- (f) countercurrently purging said adsorption zone with a purge gas comprising said light cut and recovering a purge effluent stream comprising said heavy cut.
- (g) partially repressurizing said adsorption zone by introducing an equalization gas therein;
- and
- (h) further repressurizing the adsorption zone to the adsorption pressure.
A pressure swing adsorption process for the concentration and recovery of a heavy cut comprising ethylene and heavier components from a fluid catalytic cracking (FCC) off gas feedstream to provide a feed to an ethylene plant, said FCC off gas feedstream comprising a light cut and said heavy cut, said light cut comprising hydrogen and methane said process comprising the following steps:
- (a) passing said feedstream to an adsorption zone at an adsorption zone pressure and an adsorption zone temperature in which at least a portion of the heavy cut is adsorbed and recovering an adsorption zone effluent stream comprising said light cut;
- (b) cocurrently displacing said light cut contained within said adsorption zone with a displacement gas comprising ethylene and heavier components, said displacement gas having a concentration of ethylene and heavier components which is higher than that of the feedstream and recovering a displacement effluent stream comprising said light cut;
- (c) cocurrently depressurizing said adsorption zone to an equalization pressure to provide an equalization gas;
- (d) further cocurrently depressurizing said adsorption zone to a start of blow-down pressure to provide a provide-purge gas comprising said light cut;
- (e) countercurrently depressurizing said adsorption zone to a desorption pressure that is at or above atmospheric pressure and recovering a desorption effluent stream comprising said heavy cut;
- (f) countercurrently purging said adsorption zone with a purge gas comprising said light cut and recovering a purge effluent stream comprising said heavy cut;
- (g) combining said desorption effluent stream and said purge effluent stream and passing said combination to an ethylene plant;
- (h) partially repressurizing said adsorption zone by introducing an equalization gas therein;
- and
- (i) further repressurizing the adsorption zone to the adsorption pressure.
A process for the production of ethylene comprising:
- (a) admixing an ethylene plant feed with an ethylene enriched stream to provide a feed mixture and passing said feed mixture to a cracking zone in an ethylene plant at a low pressure, said cracking zone maintained at cracking zone plant conditions effective to produce a cracking zone effluent comprising hydrogen, carbon monoxide, carbon dioxide, water, nitrogen, ethylene, propylene, ethane, propane and benzene;
- (b) passing said cracking zone effluent to a cracked gas compressor to raise the low pressure of the cracking zone effluent to a higher pressure to provide a high pressure cracked gas stream;
- (c) removing a C.sub.2 stream from the high pressure cracked gas stream and passing said C.sub.2 stream to a C.sub.2 splitter to provide an ethylene product and an ethane-rich stream, and recovering the ethylene product and returning a portion of said ethane-rich stream to the cracking zone;
- (d) passing a fluid catalytic cracking (FCC) off gas stream comprising a light cut comprising hydrogen and methane and a heavy cut comprising ethylene and heavier components to an adsorption zone said adsorption zone maintained at an adsorption pressure and an adsorption temperature in which the heavy cut is adsorbed, and recovering an adsorption effluent stream comprising said light cut;
- (e) cocurrently displacing the light cut contained within said adsorption zone with a portion of said ethane-rich stream having a concentration of ethane and recovering a displacement effluent stream comprising said light cut;
- (f) cocurrently depressurizing the adsorption zone to an equalization pressure to provide an equalization gas;
- (g) further cocurrently depressurizing the adsorption zone to a start of blow-down pressure to provide a purge gas comprising said light cut;
- (h) countercurrently depressurizing the adsorption zone to a desorption pressure that is at or above atmospheric pressure and recovering a desorption effluent stream comprising said heavy cut;
- (i) countercurrently purging the adsorption zone with a first purge gas comprising said light cut and recovering an ethylene-rich stream comprising said heavy cut and passing said ethylene-rich stream to said ethylene plant;
- (j) partially repressurizing the adsorption zone by introducing the equalization gas therein;
- and
- (k) further repressurizing the adsorption zone to the adsorption pressure.
Dependencies are inferred from the claim text.