Processes and apparatuses for recovery of ethylene from hydrocarbons

Patent metadata

Field	Value
Publication number	US-10227272-B2
Application number	US-201715798316-A
Country	US
Kind code	B2
Filing date	Oct 30, 2017
Priority date	Jun 15, 2015
Publication date	Mar 12, 2019
Grant date	Mar 12, 2019

Abstract

Embodiments of methods and apparatuses for recovery of ethylene from FCC absorber off-gas comprising a heavy cut comprising ethylene, ethane and heavier hydrocarbons and a light cut comprising hydrogen, nitrogen and methane. An exemplary method includes passing the FCC absorber off-gas to an adsorption zone containing an adsorbent selective for the adsorption of the light cut, the adsorption zone adsorbing at least a portion of the light cut and recovering an adsorption zone effluent stream comprising the heavy cut. The adsorption zone effluent is passed to a demethanizer column to provide an overhead stream comprising hydrogen, nitrogen, methane, ethylene and ethane and a net bottoms stream comprising ethylene, ethane and the heavier hydrocarbons.

First claim

The invention claimed is:

1. A process for the concentration and recovery of a heavy cut comprising ethylene, ethane and heavier hydrocarbons from a FCC absorber off-gas stream comprising a light cut and the heavy cut, the light cut comprising hydrogen, nitrogen and methane, the process comprising the following steps:
a) passing the hydrocarbon feed stream to an adsorption zone containing a silica gel adsorbent selective for the adsorption of at least about 80 wt. % each of nitrogen and hydrogen and at least about 70 wt. % of methane present in the light cut, and recovering an adsorption zone effluent stream comprising the heavy cut;
b) passing the adsorption zone effluent to a demethanizer column operated at a demethanizing temperature at least about −49° F. to provide an overhead stream comprising hydrogen, nitrogen, methane, ethylene and ethane and a net bottoms stream comprising ethylene, ethane and the heavier hydrocarbons; and
c) recycling the overhead stream to the adsorption zone.

2. The process of claim 1 further comprising sending the net bottoms stream to a C 2 splitter for recovery of ethylene.

3. The process of claim 1 , wherein the adsorption zone effluent stream is compressed prior to being passed to the demethanizer column.

4. The process of claim 3 , wherein the adsorption zone effluent stream is compressed to a pressure of at least about 28 bar (g).

5. The process of claim 3 , wherein the adsorption zone effluent stream is cooled subsequent to the compression and prior to being passed to the demethanizer column.

6. The process of claim 5 , wherein the adsorption zone effluent stream is cooled to a temperature of at least about −22° F. (−30° C.).

7. The process of claim 1 , wherein the net bottoms stream comprises less than about 1 wt % of the light cut present in the hydrocarbon feed stream.

8. The process of claim 1 , wherein the net bottoms stream comprises at least about 85 wt % of ethylene present in the hydrocarbon feed stream.

9. A process for the concentration and recovery of a heavy cut comprising ethylene, ethane and heavier hydrocarbons from a FCC absorber off-gas stream comprising a light cut and the heavy cut, the light cut comprising hydrogen, nitrogen and methane, the process comprising the following steps:
a) passing the hydrocarbon feed stream to an adsorption zone containing a silica gel adsorbent selective for the adsorption of at least about 80 wt. % each of nitrogen and hydrogen and at least about 70 wt. % of methane present in the light cut, and recovering an adsorption zone effluent stream comprising the heavy cut;
b) compressing the adsorption zone effluent stream to provide a compressed adsorption zone effluent stream;
c) cooling the compressed adsorption zone effluent stream to provide a cooled adsorption zone effluent stream;
d) passing the cooled adsorption zone effluent to a demethanizer column to provide an overhead stream comprising hydrogen, nitrogen, methane, ethylene and ethane and a net bottoms stream comprising ethylene, ethane and the heavier hydrocarbons; and
e) recycling the overhead stream to the adsorption zone.

10. The process of claim 9 further comprising sending the net bottoms stream to a C 2 splitter for recovery of ethylene.

11. The process of claim 9 , wherein the demethanizer column operates at a demethanizing temperature at least about −49° F. (−45° C.).

12. The process of claim 9 , wherein the net bottoms stream comprises less than about 1 wt % of the light cut present in the hydrocarbon feed stream.

13. The process of claim 9 , wherein the net bottoms stream comprises at least about 85 wt % of ethylene present in the hydrocarbon feed stream.

Assignees

• Uop Llc

Inventors

• Zhu Xin X
• Montalbano Joseph A

Classifications

• C07C7/04

  by distillation · CPC title

• C10G25/00

  Refining of hydrocarbon oils in the absence of hydrogen, with solid sorbents · CPC title

• C10G53/08

  including at least one sorption step · CPC title

• C07C7/12

  by adsorption, i.e. purification or separation of hydrocarbons with the aid of solids, e.g. with ion-exchangers · CPC title

• B01D53/047

  Pressure swing adsorption · CPC title