Integration of pressure swing adsorption with hydrocracking for improved hydrogen and liquids recovery

Patent metadata

Field	Value
Publication number	US-11091704-B2
Application number	US-201916256702-A
Country	US
Kind code	B2
Filing date	Jan 24, 2019
Priority date	Jan 25, 2018
Publication date	Aug 17, 2021
Grant date	Aug 17, 2021

Abstract

The invention provides a process for producing hydrogen for a hydrogen consuming process comprising obtaining a net gas stream containing hydrogen, compressing the gas stream to a pressure of 20.7 to 68.9 bar (300 to 1000 psig) to produce a compressed gas stream; sending the compressed gas stream to a pressure swing adsorption unit to be separated into a hydrogen stream and a fuel gas stream; purging the pressure swing adsorption unit with an external purge gas stream from a hydroprocessing unit off gas; treating the off gas with a thermal swing adsorption unit to remove water and other impurities prior to purging the pressure swing adsorption unit, and using a protective adsorbent layer in the pressure swing adsorption unit to adsorb impurities from the external purge gas.

First claim

The invention claimed is:

1. A process for producing hydrogen for a hydrogen consuming process comprising:
(a) obtaining a net gas stream containing hydrogen;
(b) compressing said gas stream to a pressure of about 20.7 to 68.9 bar (300 to 1000 psig) to produce a compressed gas stream;
(c) sending the compressed gas stream to a pressure swing adsorption unit to be separated into a hydrogen stream and a fuel gas stream;
(d) purging said pressure swing adsorption unit with an external purge gas stream, wherein said external purge gas stream is mixed with an internal purge gas stream obtained from de-pressurizing a bed in the pressure swing adsorption unit, wherein the flow rate of said external purge gas stream is measured and said internal purge gas stream is adjusted to obtain a desired total purge gas flow;
(e) treating said off gas with a thermal swing adsorption unit to remove water and other impurities prior to purging said pressure swing adsorption unit; and
(f) using a protective adsorbent layer in said pressure swing adsorption unit at the product-hydrogen end (top) of the bed to adsorb impurities from said external purge gas, and
wherein the ratio of external to internal purge flows is from about 40:60 to 100:0.

2. The process of claim 1 wherein said external purge gas stream is a flash gas stream from a hydrocracking reactor.

3. The process of claim 1 wherein said external purge gas stream is a flash gas stream from a hydrotreating reactor.

4. The process of claim 1 wherein said net gas stream is from a catalytic reforming reactor.

5. The process of claim 1 wherein said external purge gas stream is at a pressure of about 35 to 276 kPa (5 psig to 40 psig) when entering said pressure swing adsorption unit.

6. The process of claim 1 wherein the ratio of external to internal purge flows is about 60:40 to 90:10.

7. The process of claim 1 wherein said hydrogen is sent to one or more reactors selected from the group consisting of a hydrocracking reactor, a hydrotreating reactor an aromatics conversion reactor, and an isomerization reactor.

8. The process of claim 1 wherein said treated purge gas stream is sent through a membrane unit to produce a non-permeate stream depleted in hydrogen and a permeate hydrogen stream to be sent as said external purge gas stream through said pressure swing adsorption unit.

9. The process of claim 1 wherein said treated purge gas stream is at a pressure of about 13.8 to 41.4 bar (200 to 600 psig).

10. The process of claim 1 wherein said temperature swing adsorption unit is regenerated with a gas stream from said non-permeate stream.

11. The process of claim 1 wherein said protective adsorbent layer comprises from about 5% to 25% of said pressure swing adsorption unit bed volume.

12. The process of claim 1 wherein said protective adsorbent layer is comprised of silica gel.

13. The process of claim 1 wherein said protective adsorbent layer is comprised of activated alumina.

14. The process of claim 7 wherein said non-permeate stream is chilled to about 0° to 20° C. to produce a liquid hydrocarbon stream.

15. The process of claim 14 wherein said liquid stream is sent to fractionation section of a hydroprocessing unit to recover liquefied petroleum gas and light naphtha.

16. The process of claim 14 wherein said liquid stream is sent to fractionation section of a catalytic reforming unit to recovery liquefied petroleum gas and light naphtha.

Assignees

• Uop Llc

Inventors

• Wegerer David A
• Russell Bradley P
• Pandey Gautam
• Elseviers Wim F

Classifications

• C01B3/56

  by contacting with solids; Regeneration of used solids · CPC title

• B01D2253/104

  Alumina · CPC title

• B01D2257/406

  Ammonia · CPC title

• B01D53/75

  Multi-step processes · CPC title

• B01D2257/304

  Hydrogen sulfide · CPC title