Ultrasonic degassing for carbon capture solvents
By using an ultrasonic degassing module in the carbon capture system to remove oxygen from the solvent, the problem of accelerated solvent degradation in the prior art is solved, and the service life of the solvent and the cost reduction are achieved.
Patent Information
- Application Number
- CN202380048053.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-07-07
- Filing Date
- 2023-07-06
- Publication Date
- 2025-02-07
AI Technical Summary
The prior art has problems of high cost and low efficiency when removing oxygen from amine-based solvents in carbon capture systems, resulting in accelerated solvent degradation and increased the cost of carbon capture projects.
Ultrasonic degassing module is adopted to remove oxygen from the loaded carbon capture solvent using ultrasonic technology, extending the service life of the solvent.
By removing oxygen from the solvent, the oxidative degradation of amine-based solvents is significantly reduced, the service life of the solvent is extended, and the cost of carbon capture projects is reduced.
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Figure CN119403611A_ABST
Abstract
Description
[0001] Related Applications
[0002] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 359,093, filed on July 7, 2022, and entitled “Ultrasonic Degasification Unit for Carbon Capture Solvents,” the disclosure of which is hereby incorporated by reference herein. Technical Field
[0003] The present invention relates generally to carbon capture systems and, more particularly but not in a limiting manner, to an improved system for preserving solvents or absorbents used in carbon capture applications. Background Art
[0004] Carbon dioxide is the primary greenhouse gas emitted by human activities. In 2020, carbon dioxide accounted for approximately 79% of all human-based greenhouse gas emissions in the United States. Although a variety of carbon dioxide reduction technologies exist, the use of liquid solvents and absorbents has been widely adopted. Amine-based solvents such as monoethanolamine (MEA) have been found to be particularly effective in capturing carbon dioxide.
[0005] Nonetheless, MEA and other amine-based solvents tend to degrade at elevated temperatures and in the presence of oxygen, which can limit their usefulness and increase the costs associated with these carbon capture technologies. For large-scale carbon capture projects, amine solvent degradation can cost hundreds of millions of dollars. Most amine degradation occurs in the regenerator, where the solvent is heated to release carbon dioxide from the solvent. Air dissolved in the carbon capture solvent accelerates the degradation of the solvent.
[0006] The oxygen content of the produced carbon dioxide stream is a tightly controlled parameter. The preferred range is generally less than 10 ppm (mmol / mol) of oxygen. Air dissolved in the carbon capture solvent may contaminate the carbon dioxide stream with about 300 ppm (mmol / mol) of oxygen. Current methods for removing oxygen include catalytic oxidation or cryogenic distillation. Current practice is to design carbon capture absorber towers with hold-up volumes and residence times large enough to facilitate solvent degassing. Structured packing or agitation can be used to accelerate coalescence of the bubbles.
[0007] While these efforts have achieved some success, oversizing absorber towers adds to the costs associated with many amine-based carbon capture projects.Therefore, there is a need for an improved process for removing oxygen from amine-based carbon capture solvents that overcomes the deficiencies of the prior art. Summary of the invention
[0008] In one aspect, the present disclosure relates to a post-combustion carbon capture system configured to remove carbon dioxide from a post-combustion feed stream. The post-combustion carbon capture system includes an absorption tower configured to produce a pure gas with a reduced carbon dioxide concentration and a loaded solvent from the post-combustion feed stream. The post-combustion carbon capture system also includes a stripping tower downstream of the absorption tower, and an ultrasonic degassing module configured to remove oxygen from the loaded solvent.
[0009] In another aspect, the present disclosure relates to a gas processing system configured to remove carbon dioxide from a biogas feed stream. The biogas processing system includes a contactor tower and a stripper. The contactor tower is configured to produce a "sweet" gas and a loaded solvent from the biogas feed stream. The stripper is located downstream of the contactor tower and is configured to receive the loaded solvent. The biogas processing system also includes an ultrasonic degassing probe configured to remove oxygen from the loaded solvent.
[0010] In yet another aspect, embodiments of the invention include a method for removing carbon dioxide from a feed stream comprising carbon dioxide. The method includes the steps of contacting the feed stream with a carbon capture solvent to produce a loaded carbon capture solvent, and degassing the loaded carbon capture solvent stream with an ultrasonic degassing probe to remove oxygen from the loaded carbon capture solvent stream, thereby producing a degassing stream of carbon capture solvent. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 A flow diagram of a carbon capture process for removing carbon dioxide from a post-combustion gas feed stream.
[0012] Figure 2 A flow chart of a carbon capture process for removing carbon dioxide from a biogas feed stream. DETAILED DESCRIPTION
[0013] Figure 1 1 is a process flow diagram of a carbon capture system 100 designed to remove carbon dioxide (CO2) from a post-combustion feed stream 102. The feed stream 102 is typically a flue gas stream that is sent to an absorber 104 where it is mixed with a solvent injected from a solvent stream 106. The purified gas with a reduced CO2 concentration is discharged in a gas exhaust stream 108.
[0014] In some embodiments, the solvent is an amine-based solvent. Suitable solvents include a mixture of water and monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA) or potassium carbonate. In the present disclosure, the terms solvent, carbon capture solvent, absorbent and carbon capture absorbent are used interchangeably. The loaded solvent is discharged from the absorber 104 through the absorbent discharge stream 110. The absorbent discharge stream 110 is fed into a degassing module 118.
[0015] The degassing module 118 is configured to separate oxygen from the absorbent effluent stream 110. The separated oxygen is discharged through the oxygen removal stream 120, and the remaining solvent mixture is removed from the degassing module through the degassing gas stream 122. In an exemplary embodiment, the degassing module 118 includes an ultrasonic degassing probe 124. The ultrasonic degassing probe 124 is configured to vibrate at one or more selected frequencies that facilitate and promote the formation and coalescence of oxygen bubbles from the absorbent effluent stream 110.
[0016] The ultrasonic degassing probe 124 is available from a number of commercial sources, including Hielscher Corporation. For a pilot plant with a design throughput of about 20 tons per day (TPD) and an estimated carbon capture solvent flow rate of about 350 liters per minute (LPM), an appropriately sized degassing module 118 may include three Hielscher UIP4000 ultrasonic processor units connected in a parallel flow configuration. The number and capacity of the degassing probes 124 within the degassing module 118 are scalable to accommodate carbon capture systems 100 covering a wide range of throughputs and operating parameters.
[0017] The degassed "rich" stream 122 is directed by pump 126 to heat exchanger 128 where it is preheated and then enters stripper 130 as a hot rich stream. Stripper 130 heats the loaded solvent to release carbon dioxide from the solvent. The stripped "lean" solvent is carried from the bottom of stripper 130 in the form of lean liquid stream 132 to heat exchanger 128 where it transfers heat to the incoming rich stream 122.
[0018] The released carbon dioxide gas is carried from the top of the stripper 130 in the form of hot gas stream 134 to a condenser 136. The condenser 136 produces a condensed solvent stream 138, which is fed to a recovery solvent mixer 140 where it is mixed with the lean liquid stream 132 to form a recycle solvent stream 142. The recycle solvent stream 142 may be directed to the main solvent stream 106 for use within the absorber 104. The remaining carbon dioxide gas is removed from the condenser 136 for downstream processing or disposal.
[0019] Thus, incorporating the ultrasonic degassing module 118 within the post-combustion carbon capture system 100 extends the life of the carbon capture solvent by removing oxygen that would otherwise cause oxidative degradation. Figure 1 104, it should be understood that in other embodiments, the degassing module 118 can be included in the absorber 104. In other embodiments, the degassing module 118 can be connected between the pump 126 and the heat exchanger 128. In other embodiments, the degassing module 118 can be placed between the heat exchanger 128 and the stripper 130.
[0020] In some applications, it may be desirable to incorporate multiple ultrasonic degassing modules 118 within the post-combustion carbon capture system 100. For example, a first degassing module 118 may be placed within the absorber 104 and a second degassing module 118 may be placed between the absorber 104 and the stripper 130 to advantageously remove oxygen from the solvent. In each case, passing the loaded solvent through the degassing modules 118 removes a significant portion of the dissolved oxygen. Ultrasonic treatment removes suspended bubbles to reduce the content of dissolved oxygen in the amine-based solvent, which reduces oxidative degradation of the amine-based solvent.
[0021] Go to Figure 2 , in which a biogas processing system 200 is shown. The term "biogas" generally refers to a gas mixture consisting primarily of methane, carbon dioxide, and hydrogen sulfide. As used in the present disclosure, the term "biogas" refers to any gas produced from agricultural waste, livestock, municipal waste (e.g., landfill gas), plant material, sewage, green waste, and food waste. The biogas processing system 200 is generally configured to remove a portion of the carbon dioxide from a biogas feed stream 202 by using a suitable solvent in a contactor tower 204. The biogas feed stream 202 can originate from an open source (e.g., a feedlot) or a closed source (e.g., an anaerobic digester system).
[0022] like Figure 2 As shown, biogas feed stream 202 enters the lower part of contactor tower 204. Carbon capture solvent is injected into the upper part of contactor tower 204 through solvent injection stream 206. In some embodiments, the solvent is an amine-based solvent, such as monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA) or potassium carbonate. The solvent is mixed with biogas in contactor tower 204, where it absorbs carbon dioxide and other impurities. The loaded solvent is discharged through loaded solvent stream 208, while the "sweet" gas is discharged through sweet gas stream 210 for further processing or sale.
[0023] The loaded solvent stream 208 may be directed to a flash vessel 212, where a rapid reduction in pressure promotes separation of the liquid and gas components. In an exemplary embodiment, the flash vessel 212 includes an ultrasonic degassing probe 214, which further promotes separation of dissolved gases from the liquid fraction of the loaded solvent stream 208. The released gases are exhausted through an exhaust gas stream 216, while the rich loaded solvent is passed to a heat exchanger 218 through a rich solvent stream 220.
[0024] Heat exchanger 218 increases the temperature of rich solvent stream 220, which is then injected into stripper 222. Stripper 222 increases the temperature of loaded solvent to release absorbed carbon dioxide and other impurities (e.g., hydrogen sulfide). The separated carbon dioxide is discharged through gas outlet 224 on the top of stripper 222, while solvent is discharged through lean solvent stream 226 on the bottom of stripper 222. Carbon dioxide (or "acid gas") can be directed to additional downstream processing equipment.
[0025] The solvent in the lean solvent stream 226 passes through the heat exchanger 218 where it transfers heat to the incoming rich solvent stream 220. The lean solvent stream 226 may pass through a cooler 228 before reaching a solvent tank 230. The lean solvent may be reinjected into the contactor tower 204 from the solvent tank 230 via the injection stream 206.
[0026] In this way, the biogas processing system 200 incorporates an ultrasonic degassing probe 214 to remove dissolved oxygen from the loaded solvent stream 208. This extends the useful life of the carbon capture solvent. Although the biogas processing system 200 has been described as having an ultrasonic degassing probe 214 located within the flash vessel 214, between the contactor tower 204 and the stripper tower 222, in other embodiments, the ultrasonic degassing probe 214 is incorporated into a separate ultrasonic degassing module 232. The separate ultrasonic degassing module 232 may be located upstream or downstream of the flash vessel 212, or elsewhere in the biogas processing system 200. In some applications, it may be desirable to incorporate multiple ultrasonic degassing probes 214 or ultrasonic degassing modules 232 within the biogas processing system 200. For example, a first degassing module 232 may be placed upstream of the flash vessel 212, and a second degassing module 232 may be placed downstream of the flash vessel 212.
[0027] It should be understood that although many features and advantages of various embodiments of the present invention, as well as details of the structure and function of various embodiments of the present invention have been set forth in the foregoing description, the present disclosure is illustrative only, and to the maximum extent indicated by the broad general meaning of the terms expressed in the appended claims, detailed changes may be made, especially in the structure and arrangement of parts within the principles of the present invention. It should be understood by those skilled in the art that the teachings of the present invention may be applied to other systems without departing from the scope and spirit of the present invention.
Claims
1. A post-combustion carbon capture system (100), the post-combustion carbon capture system being configured to remove carbon dioxide from a post-combustion feed stream (102), the post-combustion carbon capture system (100) comprising: an absorber (104), wherein the absorber (104) is configured to produce a clean gas (108) having a reduced carbon dioxide concentration and a loaded solvent (110) from the post-combustion feed stream (102); a stripping tower (130), the stripping tower being located downstream of the absorption tower (104); and An ultrasonic degassing module (118) is configured to remove oxygen from the loaded solvent (110).
2. The post-combustion carbon capture system (100) of claim 1, wherein the ultrasonic degassing module (118) comprises an ultrasonic degassing probe (124).
3. The post-combustion carbon capture system (100) of claim 2, wherein the ultrasonic degassing probe (124) is located inside the absorption tower (104).
4. The post-combustion carbon capture system (100) of claim 2, wherein the ultrasonic degassing module (118) is located between the absorption tower (104) and the stripping tower (130).
5. The post-combustion carbon capture system (100) of claim 1, wherein the post-combustion carbon capture system (100) comprises a plurality of ultrasonic degassing modules (118).
6. A biogas processing system (200), the biogas processing system being configured to remove carbon dioxide from a biogas feed stream (202), the biogas processing system (200) comprising: a contactor tower (204), wherein the contactor tower (204) is configured to produce a sweetened gas (210) and a loaded solvent (208) from the biogas feed stream (202); a stripping column (222) located downstream of the contactor column (204), wherein the stripping column (222) receives the loaded solvent (208); and An ultrasonic degassing probe (214) is configured to remove oxygen from the loaded solvent (208).
7. The biogas processing system (200) of claim 6, further comprising a flash vessel (212), and wherein the ultrasonic degassing probe (214) is incorporated inside the flash vessel (212).
8. The biogas processing system (200) of claim 6, wherein the ultrasonic degassing probe (214) is integrated into a separate ultrasonic degassing module (232).
9. The biogas processing system (200) according to claim 8, wherein the biogas processing system (200) comprises a plurality of ultrasonic degassing modules (232).
10. A method for removing carbon dioxide from a feed stream comprising carbon dioxide, the method comprising the steps of: contacting the feed stream with a carbon capture solvent to produce a loaded carbon capture solvent; as well as The loaded carbon capture solvent stream is degassed using an ultrasonic degassing probe to remove oxygen from the loaded carbon capture solvent stream, thereby producing a degassed stream of carbon capture solvent.
11. The method of claim 10, wherein the feed stream is a post-combustion feed stream comprising carbon dioxide.
12. The method of claim 11, wherein the step of contacting the feed stream further comprises contacting the post-combustion feed stream with a carbon capture solvent, further comprising contacting the post-combustion feed stream with the carbon capture solvent in an absorption tower.
13. The method of claim 10, wherein the feed stream is a biogas feed stream comprising carbon dioxide.
14. The method of claim 13, wherein the step of contacting the feed stream further comprises contacting the biogas feed stream with a carbon capture solvent, further comprising contacting the biogas feed stream with the carbon capture solvent in a contactor tower.
15. The method of claim 14, wherein the step of degassing the loaded carbon capture solvent stream further comprises passing the loaded carbon capture stream through a degassing module including the ultrasonic degassing probe.