Process for separating CO2 from CO2 containing gas stream

Patent metadata

Field	Value
Publication number	US-10201778-B2
Application number	US-201715470804-A
Country	US
Kind code	B2
Filing date	Mar 27, 2017
Priority date	Jan 23, 2017
Publication date	Feb 12, 2019
Grant date	Feb 12, 2019

Abstract

The invention relates to gas separation, particularly to a process for separating CO 2 from a CO 2 containing gas stream with varying CO 2 concentration using a membrane-based separation system. The process for separating CO 2 comprises: (i) feeding the CO 2 containing gas stream into a membrane-based separation system comprising one or more membrane stages in-line, each membrane stage producing a CO 2 -depleted retentate stream and a rich CO 2 permeate stream, and (ii) recycling a part of the CO 2 -rich permeate stream from at least one membrane stage as a recycled stream, into a preceding feed stream of one or more membrane stages in the membrane-based separation system to adjust the CO 2 concentration of the feed stream. The process could stabilize the CO 2 concentration in the feed steam by recirculation of a fraction of the high purity CO 2 permeate to the feed of the membrane system, which would result in a lower incremental auxiliary load than other options such as compression of the entire gas stream.

First claim

The invention claimed is:

1. A process for separating CO 2 from a CO 2 containing gas stream with varying CO 2 concentration in time comprising:
(i) feeding the CO 2 containing gas stream with varying CO 2 concentration into a membrane-based separation system comprising one or more membrane stages in-line, each membrane stage producing a CO 2 -depleted retentate stream and a CO 2 -rich permeate stream, and
(ii) recycling a part of the CO 2 -rich permeate stream of one or more membrane stages as a recycled stream, into a preceding feed stream of one or more membrane stages in the membrane-based separation system to adjust the CO 2 concentration of the feed stream to keep the CO 2 concentration in the feed stream to one or more of stages of the membrane-based separation system steady, the flow rate of the recycled stream is adjusted based on measurements of the CO 2 concentration of the feed stream, or the flow rate of the recycled stream is adjusted based on upstream parameters in accordance with which the CO 2 containing gas stream is generated including: operational parameters of the plant where the CO 2 containing gas stream is generated, or operational parameters related to upstream emissions controls of the CO 2 containing gas stream.

2. The process according to claim 1 wherein the CO 2 containing gas stream is a flue gas stream produced from power generation using fossil fuels.

3. The process according to claim 2 , wherein the fossil fuel is coal.

4. The process according to claim 1 further comprising using a part of the last CO 2 -rich permeate stream from the last membrane stage as the recycled stream.

5. The process according to claim 1 further comprising recycling at least a part of the recycled stream into the first feed stream of the first membrane stage.

6. The process according to claim 5 wherein the CO 2 concentration of the first feed stream is adjusted to 12 mol % or more by the recycled stream.

7. The process according to claim 6 wherein the CO 2 concentration of the first feed stream is adjusted to 12 mol % - 15 mol % by the recycled stream.

8. The process according to claim 1 wherein the flow rate of the recycled stream is 70 mol % or less based on total content of the last CO 2 -rich permeate stream.

9. The process according to claim 8 wherein the flow rate of the recycled stream is 25 mol % - 70 mol % based on total content of the last CO 2 -rich permeate stream.

10. The process according to claim 9 wherein the flow rate of the recycled stream is 30 mol % - 65 mol % based on total content of the last CO 2 -rich permeate stream.

11. The process according to claim 1 wherein the recycled stream enables the total content of the feed stream to be increased by 15 mol % or less.

12. The process according to claim 1 wherein overall CO 2 recovery rate is 50% or more.

13. The process according to claim 12 wherein the overall CO 2 recovery rate is 60% - 90%.

14. The process according to claim 1 wherein the concentration of CO 2 in the last permeate stream is 60 mol % or above.

15. The process according to claim 14 wherein the concentration of CO 2 in the last permeate stream is 90 mol % or above.

16. The process according to claim 14 wherein the concentration of CO 2 in the last permeate stream is 95 mol % or above.

Assignees

• China Energy Investment Corp Ltd
• Nat Inst Clean & Low Carbon Energy

Inventors

• Gu Youzong
• Xu Wenqiang

Classifications

• B01D53/1493

  Selection of liquid materials for use as absorbents · CPC title

• B01D53/62

  Carbon oxides · CPC title

• B01D53/1475 Primary

  Removing carbon dioxide · CPC title

• B01D53/1425

  Regeneration of liquid absorbents · CPC title

• B01D2257/504

  Carbon dioxide · CPC title