阅读说明：本技术 基于生物催化剂的co2汽提技术和相关系统 (Biocatalyst-based CO2Stripping techniques and related systems ) 是由 西尔维·弗拉德特 理查德·苏尔珀勒南 埃里克·马多尔 哈纳·布特贾 西尔万·勒费布尔 费雷 于 2020-02-27 设计创作，主要内容包括：本发明涉及一种用于从含生物催化剂的富CO-(2)吸收溶液中汽提CO-(2)而生成含生物催化剂的贫CO-(2)吸收溶液和富CO-(2)气体的CO-(2)汽提方法,该方法包括：-在汽提气体发生单元中由一部分含生物催化剂的贫CO-(2)吸收溶液生成汽提气体,和-使含生物催化剂的富CO-(2)吸收溶液与汽提气体在气液接触器中接触而生成贫CO-(2)吸收溶液和富CO-(2)气体。(The invention relates to a method for enriching CO from a biomass-containing material 2 Stripping CO from absorption solution 2 To produce CO lean with biocatalyst 2 Absorption solution and rich CO 2 CO of gas 2 A stripping process, the process comprising: -from a portion of the CO lean with biocatalyst in a stripping gas generation unit 2 Absorbing the solution to form a stripping gas, and enriching the biocatalyst-containing CO 2 The absorption solution is contacted with a stripping gas in a gas-liquid contactor to produce a lean CO 2 Absorption solution and rich CO 2 A gas.)

1. Method for enriching CO from biological catalyst₂Stripping CO from absorption solution₂To produce CO lean with biocatalyst₂Absorption solution and rich CO₂CO of gas₂A stripping process, the process comprising:

from a portion of the biocatalyst-containing lean CO in a stripping gas generation unit₂The absorption solution produces a stripping gas, and

subjecting the biocatalyst-containing CO-rich in a gas-liquid contactor₂Contacting the absorbing solution with the stripping gas to produce the CO lean₂An absorption solution and the CO-rich₂A gas.

2. The method of claim 1, wherein the stripping gas generation unit is a falling film evaporator.

3. The method of claim 1 or 2, wherein the gas-liquid contactor is a gas-liquid direct contactor.

4. The method of claim 3, wherein the gas-liquid contactor is a packed column, a tray column, a spray reactor, or a rotating packed bed.

5. Method for enriching CO from biological catalyst₂Stripping CO from absorption solution₂To produce CO lean with biocatalyst₂Absorption solution and rich CO₂CO of gas₂A stripping process, the process comprising:

CO enrichment from the biocatalyst₂Generating a stripping gas in the absorption solution, and

subjecting the biocatalyst-containing CO-rich in a gas-liquid contactor₂Contacting the absorbing solution with the stripping gas to produce the CO lean₂An absorption solution and the CO-rich₂A gas.

6. The method of claim 5, wherein generating the stripping gas comprises heating the biocatalyst-containing CO-rich in the gas-liquid contactor₂Absorbing the solution to thereby separate the CO rich from the biocatalyst-containing in the gas-liquid contactor₂Simultaneous production of the stripping gas and stripping of the CO in an absorption solution₂。

7. The process according to claim 5 or 6, wherein the gas-liquid contactor is a gas-liquid direct contactor, optionally a falling film evaporator.

8. The method of any one of claims 1-7, wherein the biocatalyst-containing CO-rich₂The absorbing solution is an aqueous solution and the stripping gas produced comprises water vapor.

9. Method for enriching CO from biological catalyst₂Stripping CO from absorption solution₂To produce CO lean with biocatalyst₂Absorption solution and rich CO₂CO of gas₂A stripping process, the process comprising:

condensing at least a portion of the CO-rich₂The gas generates a vapor-extracting liquid,

generating a stripping gas from said stripping solution, and

enriching the CO containing biocatalyst₂Contacting the absorption solution with the stripping gas to form the biocatalyst-containing lean CO₂An absorption solution and the CO-rich₂A gas.

10. The method of claim 9, wherein generating the stripping gas from the stripping solution is performed in a reboiler.

11. The method of claim 9 or 10, wherein the biocatalyst-containing CO-rich₂The contacting of the absorption solution with the stripping gas is carried out in a gas-liquid direct contactor.

12. The method of claim 11, wherein the gas-liquid direct contactor is a packed column, a tray column, a spray reactor, or a rotating packed bed.

13. The method of any one of claims 9-12, wherein the stripping solution is an aqueous liquid, i.e., water or an aqueous solution, and wherein the stripping solution optionally comprises a CO-lean extract derived from the CO-lean mixture₂Absorbing the water of the solution.

14. The method of claim 13, wherein the aqueous solution is a solution comprising NaCl, KCl, K₂CO₃、Na₂CO₃Or a combination thereof.

15. The method of any one of claims 9-12, wherein the vapor extract is an organic liquid compound.

16. The method of claim 15, wherein the vapor draw solution is immiscible with water and has a lower density than water.

17. The method of claim 15, wherein the vapor draw solution is immiscible with water and has a higher density than water.

18. The method of claim 15, wherein the organic liquid compound is hydrocarbon C_xH_yWherein x is 5 or 6; or halogenated hydrocarbon derivatives including hexane, cyclohexane, cyclopentane, cis-1, 2-dichloroethylene, 2-methylpentane, trichloroethylene, CHCl₃Perfluorohexane, tetramethylsilane, or combinations thereof.

19. Method for enriching CO from biological catalyst₂Stripping CO from absorption solution₂To produce CO lean with biocatalyst₂Absorption solution and rich CO₂CO of gas₂A stripping process, the process comprising:

enriching the CO containing biocatalyst₂The absorption solution is directly contacted with a stripping gas to form said biocatalyst-containing CO-lean₂An absorption solution and the CO-rich₂A gas, said stripping gas being a non-condensable gas.

20. The method of claim 19, wherein the biocatalyst-containing CO-rich is carried out in a packed column, a tray column, a spray reactor, or a rotating packed bed₂Direct contact of the absorbing solution with said stripping gas.

21. The method of claim 19 or 20, wherein the non-condensable gas is air or nitrogen.

22. The process of any of claims 1-20, wherein the stripping gas is fed to a plurality of spaced apart locations, preferably distributed along the height of the gas-liquid contactor.

23. The method of any one of claims 1-22, wherein the biocatalyst-containing CO-rich₂The absorption solution is withdrawn from a different portion of the gas-liquid contactor to be heated and re-injected into the gas-liquid contactor via a heating loop.

24. The method of any one of claims 1-23, comprising minimizing or avoiding the biocatalyst-containing CO-rich₂Absorption solution and the biocatalyst-containing CO-lean₂The absorbing solution is exposed to bubble forming conditions under which a new gas-liquid interface is created by bubble formation.

25. Method for enriching CO from biological catalyst₂Stripping CO from absorption solution₂CO of₂A stripping process, the process comprising:

enriching the CO containing biocatalyst₂Contacting the absorbing solution with a stripping gas to produce CO-rich from the biocatalyst-containing₂Absorption solution stripping of CO₂Thereby producing a CO lean product containing the biocatalyst₂Absorption solution and rich CO₂A gas; and

minimizing or avoiding the need to enrich the CO with biocatalyst₂Absorption solution and the biocatalyst-containing CO-lean₂The absorbing solution is exposed to bubble forming conditions under which a new gas-liquid interface is created by bubble formation.

26. The method of claim 25, further comprising stripping the CO lean with the biocatalyst from a portion of the CO lean with the biocatalyst in a stripping gas generation unit₂The absorption solution generates the stripping gas, which is optionally a falling film evaporator.

27. The method of claim 25, further comprising removing the CO-rich containing biocatalyst from the gas-liquid direct contactor in a gas-liquid direct contactor₂The absorption solution produces a stripping gas, and the gas-liquid direct contactor is optionally a falling film evaporator.

28. The method of claim 25, further comprising condensing at least a portion of the CO-rich stream₂A gas to produce a stripping solution and generating the stripping gas from the stripping solution in a stripping generating unit, which is optionally a reboiler or a vaporizer.

29. The method of claim 26 or 28, wherein the biocatalyst-containing CO-rich₂The contacting of the absorption solution with the stripping gas is carried out in a packed column, a tray column, a spray reactor or a rotating packed bed.

30. CO based on biocatalyst₂A capture process, comprising:

make CO contained₂Is contacted with an absorption solution containing a biocatalyst to produce a biocatalyst-containing CO-rich product₂The absorption solution is absorbed by the absorption solution,

use of a CO according to any of claims 1-29₂Stripping process from the biocatalyst-containing CO-rich₂Desorption of CO in absorption solution₂Thereby generating CO lean₂Absorption solution and rich CO₂A gas.

31. CO enrichment from a biomass-containing liquid in a vaporizer₂Desorption of CO in absorption solution₂The process method of (2), the process method comprising:

the CO-rich gas containing the biocatalyst₂The absorption solution is fed to the evaporator, and

heating the biocatalyst-containing CO-rich₂Absorbing the solution from the CO-rich containing biocatalyst₂While absorbing in solutionGenerating stripping gas and generating desorbed CO₂The driving force of (2).

32. The process of claim 31, wherein the evaporator is a falling film evaporator.

33. Use of a vaporizer to generate a stripping gas for the removal of CO from a biocatalyst-rich stream₂Stripping CO from absorption solution₂And producing CO lean with biocatalyst₂Absorbing the solution.

34. Use according to claim 33, wherein the vaporizer is for use in removing CO from a biocatalyst-rich stream₂The absorption solution generates a stripping gas.

35. Use according to claim 33, wherein the vaporizer is for removing CO lean with the biocatalyst from the stream₂The absorption solution produces the stripping gas.

36. The use according to any one of claims 33-35, wherein the evaporator is a falling film evaporator.

37. The method according to any one of claims 1-29, the process according to any one of claims 30-32 and the use according to any one of claims 33-36, wherein the biocatalyst-containing CO-rich₂The absorption solution contains the biocatalyst in soluble form or in immobilized form and is capable of flowing in the stripping gas generation unit and/or the gas-liquid contactor.

38. The method, process or use of claim 37, wherein the biocatalyst is immobilized on particles or entrapped within a porous matrix.

39. The method, process or use according to claim 37 or 38, wherein the biocatalyst is carbonic anhydrase or an analogue thereof.

Technical Field

The present invention relates generally to biocatalyst-based CO₂Capture process and more particularly to CO using gas-liquid contactors₂A stripping technique.

Background

Some known CO₂The capture process is based on the use of the enzyme carbonic anhydrase to increase the CO of the absorption solution₂Trapping performance. These processes consist of two main units: from the content of CO₂Capture of CO in the gas₂And from rich CO₂Releasing the absorbed CO in an absorption solution₂And thereby regenerating the stripping unit of the absorption solution.

Simplified CO₂The configuration of the capture process is designed as shown in figure 1. The process comprises two zones: an absorption zone operating at a lower temperature and a stripping zone operating at a higher temperature. In this process, the CO is contained₂Is fed to an absorption unit (2) in which it flows upwards while being in contact with an absorbing aqueous solution (4). As the gas contacts the absorbing solution, CO₂Is absorbed by the solution. The treated gas (3) then leaves the absorption unit and is released into the atmosphere or sent to other units for further treatment or use. Then containing the absorbed CO₂Is pumped (pump 6) through two heat exchangers (7, 8) in which its temperature is raised and subsequently fed to a stripping unit (9), conditions being adjusted in the stripping unit (9) to bring about CO₂The solution is released from the solution and regenerated. The heat exchanger (8) is generally optional. The gas (19) leaving the stripping unit (9) is fed to a condenser (14) where water vapour is condensed. The gas-liquid stream (20d) is then sent to a separator (14a) where the high CO is present₂The concentrated gas (20b) leaves the separator (14a) and is sent (compressor/vacuum pump 36) for its use or further processing (stream 20). The condensed water vapour (20a) is returned to the process. Part of the CO lean leaving the stripping unit (10)₂The absorption solution is returned to the absorption unit using a pump (16), while another part is lean in CO₂The absorption solution (11) is pumped to the reboiler (12) by a pump (17). The solution is then boiled to produce water vapour and the resulting vapour/liquid mixture (13) is sent to a stripping unit (9). The water vapor moves upward and acts as a stripping gas to facilitate desorption of CO from the solution₂. The solution (15) is cooled by means of heat exchangers (7, 18) before being fed to the absorption column.

When used in combination with the above techniques, the absorption solution is usually an alkaline solution characterized by a pH above 9, the absorption unit is operated at a temperature in the range of 10-50 ℃, and the CO-rich solution₂The absorption solution is heated to a temperature of 50-90 c before being fed to a stripping unit that can be operated under vacuum conditions or near atmospheric pressure conditions. Thus, in this class of CO₂The enzymes used in the capture process may be exposed to alkaline pH values above 9 and temperatures in the range of 10-90 ℃, high pH and high temperature conditions are known to be detrimental to the enzymes.

Most reports of enzyme-based (carbonic anhydrase-based) CO₂References to capture processes will emphasize the enzyme pair enhancing CO₂Catalysis of the performance of the capture process. Enzyme lifetime in such processes is a key issue, mainly solved by improving enzyme thermostability in a number of ways.

In the first strategy, the enzyme is used in the absorption zone of the process, where the process temperature to which the enzyme is exposed is the lowest. This strategy is applied in different ways: when the gas-liquid contactor is a packed column, the enzyme may be immobilized on the packing, and in this configuration the enzyme is always in the absorption column and thus exposed to low temperature conditions. The enzyme may also be immobilized on particles suspended in the absorption solution. In this configuration design, once the absorption solution leaves the absorption column, the particles are separated from the CO-rich stream₂Separated from the absorption solutionAnd reinjected into the absorption solution before it is fed to the absorption unit. The enzyme may be used free or dissolved in an absorbing solution, and the enzyme may be leached from the solution like a microparticle. In this first strategy, the enzyme is only exposed to the pH and temperature conditions present in the absorption zone of the process.

In a second strategy, the increase in enzyme stability is performed by using carbonic anhydrase (carbonic anhydrase) selected from natural microorganisms that are robust to process conditions or by genetically modifying carbonic anhydrase using directed evolution to develop enzymes that are robust to specific process conditions. The ultimate goal of this second strategy is to develop an enzyme that is active and robust to the operating conditions of the absorption and stripping zones of the process.

A third strategy consists in combining the powerful new enzymes obtained from the second strategy with an immobilization technique and using such powerful immobilized enzymes in the absorption zone only or in both the absorption and stripping zones.

With CO based on biocatalysts₂There is still room for improvement in the performance of the capture process methods that will increase the half-life of the biocatalyst when submitted to the operating conditions.

Disclosure of Invention

Biocatalyst-based CO₂Implementation of the capture process method responds to the above need by providing process design options tailored to minimize or avoid exposure of the biocatalyst-containing solution to bubble forming conditions that create a new gas-liquid interface through bubble formation, thereby increasing the lifetime of the biocatalyst. For example, bubble formation conditions are met when a solution containing a biocatalyst is boiled.

The present technology relates to biocatalyst-based CO₂A capture process can include enriching a CO containing biocatalyst in a stripping system₂The absorption solution is contacted with a stripping gas to produce CO-rich gas from the biocatalyst-containing stream₂Desorption of CO in absorption solution₂Thereby producing a CO lean product containing the biocatalyst₂Absorption solution and rich CO₂A gas.

The stripping system includes a gas-liquid contactor, which can be a gas-liquid direct contactor. A gas-liquid direct contactor refers to a unit capable of achieving contact between a gas phase and a liquid phase without any physical barrier (e.g., a membrane). In some embodiments, the gas-liquid contactor can be selected from, for example, a packed column, a tray column, a spray reactor, a rotating packed bed, and a falling film evaporator.

The biocatalyst may be used in soluble form or in immobilized form, e.g. immobilized on particles or entrapped within a porous matrix. For both biocatalyst delivery formats, it is possible to use in the absorption unit (in rich CO)₂In absorption solution) and desorption units (in lean CO)₂In an absorbing solution) to flow with the absorbing solution.

In a first aspect, there is provided a CO₂A stripping process comprising: generating stripping gas, and enriching CO₂The absorption solution is contacted with a stripping gas to produce a CO lean product₂Absorption solution and rich CO₂A gas.

Optionally, at least a portion or all of the stripping gas is CO lean by a portion₂An absorption solution is produced. In the CO₂In some embodiments of the stripping process, generating the stripping gas comprises passing a portion of the CO-lean stream to the stripping gas outlet₂The absorption solution is fed to a stripping gas generation unit to generate a stripping gas, and the method further comprises feeding the stripping gas to a gas-liquid contactor. The stripping gas generation unit may be a falling film evaporator and the gas-liquid contactor may be a packed column, a tray column or a rotating packed bed.

Further optionally, the stripping gas is enriched in CO₂An absorption solution is produced. In the CO₂In some embodiments of the stripping process, generating the stripping gas comprises heating the CO-rich gas in a gas-liquid contactor₂Absorbing the solution to produce a stripping gas and simultaneously stripping the CO-rich stream₂Absorbing the solution. The gas-liquid contactor can be a falling film evaporator.

In some embodiments, the absorption solution is a biocatalyst-based aqueous solution and the generated stripping gas can therefore comprise water vapour.

In a further aspect of the present invention,providing a CO₂A stripping process comprising: condensing at least a portion of the CO-rich₂Gas to produce stripping liquid, stripping gas from the stripping liquid, and enriching CO₂The absorption solution is contacted with a stripping gas to produce a CO lean product₂Absorption solution and rich CO₂A gas.

In some embodiments, generating stripping gas from the stripping liquid is performed in a reboiler, the stripping gas being fed to the gas-liquid direct contactor. For example, the gas-liquid direct contactor can be a packed column, a tray column, a spray reactor, or a rotating packed bed.

In some embodiments, the stripping liquid is an aqueous liquid, which can be an aqueous solution or an aqueous solution, such as a salt solution (e.g., NaCl, KCl, K)₂CO₃、Na₂CO₃)。

In other embodiments, the stripping solution is an organic liquid compound. Optionally, the stripping liquid can be immiscible with water and have a lower density than water. Further optionally, the stripping liquid can be immiscible with water and have a higher density than water. For example, the organic liquid compound may be a hydrocarbon C_xH_yWherein x is 5 or 6; or halogenated hydrocarbon derivatives including hexane, cyclohexane, cyclopentane, cis-1, 2-dichloroethylene, 2-methylpentane, trichloroethylene, CHCl₃Perfluorohexane or silicone such as tetramethylsilane.

In some embodiments, the stripping gas is fed to a plurality of spaced apart locations, preferably distributed along the height of the gas-liquid contactor. In other embodiments, the CO-rich stream is enriched in CO₂The absorption solution is withdrawn from different parts of the gas-liquid direct contactor, heated and re-injected into the gas-liquid contactor through a heating circuit.

In a further aspect, there is provided a CO₂A stripping process comprising: will be rich in CO₂The absorption solution is contacted directly with a stripping gas to produce a CO lean product₂Absorption solution and rich CO₂A gas, the stripping gas being a non-condensable gas. It should be noted that direct contact refers to the gas phase without any physical barrier (e.g., membrane)And a liquid phase.

In some embodiments, the rich CO₂The direct contact of the absorption solution with the stripping gas is carried out in a packed column, a tray column or a rotating packed bed (acting as a gas-liquid contactor).

In some embodiments, the non-condensable gas is air or nitrogen.

In a further aspect, there is provided a CO₂A stripping process comprising: minimizing or avoiding the enrichment of CO₂The absorption solution is exposed to bubble forming conditions generated via bubble formation at the fresh gas-liquid interface, and from the rich CO₂Stripping CO from absorption solution₂。

In a further aspect, biocatalyst-based CO is provided₂A capture process, comprising: make CO contained₂Gas is contacted with an absorption solution to produce CO-rich gas₂Absorption solution, and use of CO as defined above₂Stripping process from rich CO₂Desorption of CO from the absorption solution₂Thereby generating CO lean₂Absorption solution and rich CO₂A gas.

In another aspect, a method of enriching CO from a biocatalyst in a vaporizer is provided₂Desorption of CO in absorption solution₂The process method comprises the following steps: the CO-rich gas containing the biocatalyst₂The absorption solution is fed to the evaporator and the CO-rich containing biocatalyst is heated₂Absorbing the solution while producing a stripping gas and producing CO rich from the biocatalyst₂Desorption of CO from absorption solution₂The driving force of (2). In some embodiments, the evaporator can be a falling film evaporator or the like.

In another aspect, a vaporizer is provided for producing CO rich for use in removing CO from a biological catalyst containing stream₂Stripping CO from absorption solution₂Stripping the gas and producing CO-rich gas containing biocatalyst₂Use of an absorption solution. In some embodiments, the vaporizer is used to remove CO from a rich CO containing biocatalyst₂The absorption solution generates a stripping gas. In other embodiments, the vaporizer is used to remove moisture from a biomassCO-lean of the catalyst₂The absorption solution generates a stripping gas. In some embodiments, the evaporator can be a falling film evaporator.

While the invention will be described in conjunction with the exemplary embodiments, it will be understood that they are not intended to limit the scope of the invention to these embodiments. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included as defined by the specification. The objects, advantages and other features of the present invention will become more apparent and better understood upon reading of the following non-limiting description of the invention, given with reference to the accompanying drawings.

Drawings

Biocatalyst-based CO₂The implementation of the capture process and associated units is illustrated in and will be further understood with reference to the following figures.

FIG. 1 is a biocatalyst-based CO comprising an absorption zone and a stripping zone (prior art)₂Simplified diagram of the capture process.

FIG. 2 is a biocatalyst-based CO₂Simplified diagram of the capture process wherein the reboiler is replaced by a falling film evaporator.

Figure 2a is a schematic of a falling film evaporator.

Fig. 3 is a block diagram of a stripping unit configuration according to a first embodiment, wherein the stripping gas required for the stripping unit is provided via a stripping gas loop.

Fig. 3a is a block diagram of a stripping unit configuration design according to a second embodiment in which the stripping gas is injected through a plurality of injection ports distributed along the height of the stripping unit, wherein the stripping gas required for the stripping unit is provided through a stripping gas loop.

Figure 3b is a block diagram of a stripping unit configuration according to a third embodiment in which the absorption solution is taken from a different part of the stripping unit for heating and re-injection into the stripping unit via a heating loop, wherein the stripping gas required for the stripping unit is provided via a stripping gas loop.

FIG. 4 is a schematic diagram including stripping gas and evaporation back according to the first embodimentCO based biocatalysts for roadways₂Schematic of the capture process.

FIG. 4a is a biocatalyst-based CO comprising a stripping gas and a vaporization loop according to a second embodiment₂Schematic of the capture process.

FIG. 4b is a biocatalyst-based CO comprising a stripping gas and a vaporization loop according to an alternative embodiment wherein the gas used in the vaporization loop is used in a closed loop system₂Schematic of the capture process.

FIG. 5 is a biocatalyst-based CO₂An illustration of the capture process wherein the stripping gas required for the stripping unit is provided by a stripping gas loop and wherein the stripping liquid is immiscible with and has a lower density than water.

FIG. 5a is a biocatalyst-based CO₂An illustration of the capture process wherein the stripping gas required for the stripping unit is provided by a stripping gas loop and wherein the stripping liquid is immiscible with and has a higher density than water.

FIG. 6 is a biocatalyst-based CO₂Schematic of the capture process wherein the stripping gas required for the stripping unit is a gas provided from an external source.

FIG. 6a is a biocatalyst-based CO₂Schematic of the capture process wherein the stripping gas required for the stripping unit is a gas provided from an external source and wherein the gas is heated prior to being fed to the stripping unit.

FIG. 7 is a biocatalyst-based CO₂Schematic of the capture process wherein the stripping unit is a falling film evaporator and wherein the stripping gas is water vapor vaporized from the absorbing solution.

FIG. 7a is a biocatalyst-based CO₂Illustration of the course of the capture process, in which the stripping unit consists of two falling-film evaporators operating in parallel and in which the stripping gas is water vapor vaporized from the absorption solution.

FIG. 7b is a biocatalyst-based CO₂Schematic of the capture process wherein the stripping unit consists of two falling film steamers operating in seriesA generator, and wherein the stripping gas is water vapor vaporized from the absorbing solution.

FIG. 7c is a biocatalyst-based CO₂Illustration of a capture process wherein the stripping unit consists of two falling-film evaporators operating in series and wherein the stripping gas of the first falling-film evaporator is the heat source of the second falling-film evaporator.

While the invention will be described in conjunction with the exemplary embodiments, it will be understood that they are not intended to limit the scope of the invention to these embodiments. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included as defined by the appended claims.

Detailed Description

The present technology relates to biocatalyst-based CO₂The field of trapping. Containing CO₂The gas may be post-combustion flue gas, process gas, biogas or natural gas from different sources. In particular, the invention relates to carbonic anhydrase-based CO₂A capture process wherein a biocatalyst, carbonic anhydrase, is present in an absorption solution and flows with the solution through a gas-liquid contactor. More specifically, the present invention discloses methods/processes that can increase the life of the biocatalyst process and reduce the cost of the biocatalyst in this technology.

Recent studies clearly show that, in addition to pH and temperature, the third parameter has a very important influence on the biocatalyst process stability: rate of formation of new gas-liquid interface. This occurs in the absorption unit, the stripping unit, and more importantly in the reboiler associated with the stripping unit which provides a stripping gas, typically steam, by boiling the absorption solution. This clearly shows that the rate of biocatalyst activity loss is directly related to the steam flow rate generated in the reboiler. In fact, in CO₂During the capture process, what mainly causes the loss of biocatalyst activity is a high boiling rate that provides a high rate of gas-liquid interface formation.

In the following description, the term "about" means within an acceptable error range for the particular value determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, i.e., the limitations of the measurement system. It is generally accepted that measurements with 10% accuracy are acceptable and the term "about" is included.

In the above description, the implementation is one embodiment or implementation example of the present invention. The various appearances of "one embodiment," "an embodiment," "some embodiments," or "certain embodiments" are not necessarily all referring to the same embodiments. While various features of the invention may be described in the context of a single embodiment, these features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment.

It is worth mentioning that throughout the following description, when the article "a" is used to introduce an element, it does not have the meaning of "only one" but may mean "one or more". It will be further understood that where the specification states a component, feature, structure, or characteristic "may", "might", "can", or "could" be included, that particular component, feature, structure, or characteristic is not required to be included.

Biocatalyst-based CO as described herein₂Trapping techniques include controlling the rate of gas-liquid interface formation that affects the life of the biocatalyst. More specifically, a process is provided that minimizes the creation of a fresh gas-liquid interface and increases the life of the biocatalyst during the process.

This description should be read in light of the following definitions:

absorption tower or absorption unit

The absorption column (also referred to herein as an absorption unit) is a gas-liquid contactor, which can be, for example, a packed column, a tray column, or a rotating packed bed.

Steam stripping device

The stripper (also referred to herein as a stripping unit or stripper) is a gas-liquid contactor, which can be a packed column, a tray column, a spray reactor, a rotating packed bed, or a falling film evaporator.

Absorbing solution

The absorption solution is an aqueous solution which may comprise at least one of the following compounds: k₂CO₃、KHCO₃、Na₂CO₃、NaHCO₃Tertiary amines, tertiary alkanolamines, tertiary amino acids. The absorbing solution includes a non-urethane forming solution.

Rich in CO₂Gas (es)

Rich in CO₂The gas is the gas phase that exits the stripper prior to any subsequent treatment or process steps.

Biocatalysts

The biocatalysts that can be used in the present technology are selected from the group consisting of enzymes, liposomes, microorganisms, animal cells, plant cells, and any combination thereof. The biocatalyst may be used in soluble form or in immobilized form, i.e. immobilized on particles or entrapped within a porous matrix. For both forms of biocatalyst delivery, the biocatalyst will flow with the absorption solution in the absorption and desorption unit. It should be noted that the biocatalyst may preferably be an enzyme, e.g. carbonic anhydrase. The enzyme may be present in the absorption solution at an enzyme concentration of about 0-2g/L, alternatively about 0.05-1g/L, further alternatively about 0.1-0.3 g/L.

The relatively low molecular weight enzyme carbonic anhydrase can be made part of the complex to increase its size. Different types of enzyme complexes may be formed. Including those using whole cells such as red blood cells. However, for red blood cells, the enzyme leaks and is lost rapidly. The carbonic anhydrase can be immobilized on the surface of the particulate support material, embedded within the particulate support material, or a combination thereof. In another alternative aspect, the carbonic anhydrase may also be provided as cross-linked enzyme aggregates (CLEAs), and the support material comprises a portion of the carbonic anhydrase and the cross-linking agent. In yet another alternative aspect, the carbonic anhydrase is provided as cross-linked enzyme crystals (CLECs), and the support material comprises a portion of the carbonic anhydrase. The materials and methods selected must be capable of stabilizing the enzyme to make it more stable to the process conditions, so that the enzyme remains immobilized, i.e., immobilized or entrapped, within the carrier material when used during the process. In other words, the material and chemical bonds (if chemical methods are used) must remain stable for a long period of time to provide long term stability of the enzyme during the process.

The present invention provides for CO reduction by proposing an alternative process configuration in which there is little boiling and in which the biocatalyst in the absorption solution flows through the absorption and desorption units₂A process for capturing the rate of loss of activity of a biocatalyst in a process. Three options are discussed below.

In a first option, the water vapor is passed through to lean CO₂The absorption solution is sent to the evaporator instead of the reboiler. Reboilers are commonly used for CO₂Capture process to recover CO lean₂Water vapor is generated in the absorption solution. When the absorption solution boils, i.e. bubbles of water vapour are formed in the solution, water vapour is generated. The generation of these water vapor bubbles can lead to the generation of new gas/liquid interfaces (water vapor bubbles from the absorption solution), which are found to be detrimental to the biocatalyst. To minimize bubble formation, the reboiler (12) (fig. 1) may be replaced by an evaporator in which the operating conditions are adjusted to produce water vapor via evaporation, i.e., vaporization of water at the surface of the aqueous solution. Under such operating conditions, the creation of a new gas/liquid interface is minimal and entirely due to the flow of absorption solution in the evaporator. This device almost eliminates the formation of bubbles and thus the minimal exposure of the carbonic anhydrase to the fresh gas/liquid interface.

In a second option, the stripping gas is not provided after evaporation or boiling of the absorbing solution, but rather from an external stripping gas loop where the stripping gas is condensable (e.g. water). The absorption solution is not fed to the reboiler and is therefore not exposed to any boiling conditions. The reboiler (12) (fig. 1) is removed from the process configuration set up.

In a third option, the reboiler (12) (fig. 1) is removed from the process and the stripping gas required for the stripping unit is a non-condensable gas. The absorption solution is not exposed to any boiling conditions. The stripping gas is a non-condensable gas, such as air or nitrogen.

The operating conditions in the absorption unit may include an absorption temperature of about 10-60 ℃ and an absorption pressure of about 1-40 bar. Operating conditions in the stripping unit: a stripping temperature of about 50-80 ℃ and a stripping pressure of about 0.1-1atm may be included.

Selecting 1: falling film evaporator

In a first alternative, it is recommended to replace the reboiler with an evaporator. Evaporators are used in many industries, such as the food, chemical, pharmaceutical and dairy industries, for concentrating solutions or slurries. In these applications, water must be removed from these solutions or slurries to obtain a product of the desired quality. In these applications, water vapor is removed and the concentrated solution is the final product. For example, to prepare condensed milk, more than 45% of the water is evaporated from natural milk.

Different types of evaporators can be used, these being: forced circulation, natural circulation, film scraping, film lifting pipes, film lowering pipes, film lifting/lowering pipes, film lifting plate evaporators, falling film plate evaporators and rising/falling film plate evaporators. Of these, falling film evaporators (tubular or plate type) are preferred because of their very short residence time in the apparatus, good heat transfer coefficient, and their ability to operate under vacuum conditions where water evaporates at lower temperatures than atmospheric or higher pressures. It has gained wide acceptance in the food industry for the concentration of heat sensitive products.

A schematic of a tubular falling film evaporator is provided in figure 2 a. The tubular falling-film evaporators (2a-7) consist of a shell and a tube. The liquid to be concentrated (2a-3) is fed to the distributor at the top of the evaporator. The distributor is intended to be designed to distribute the liquid evenly into each tube. This is important to avoid any dry areas on the surface of the pipe that could lead to reduced performance. Liquid is fed into the wall where a film is formed. The liquid film descends with gravity. The downward flow is enhanced by the parallel downward flow of the vapor formed. This results in thinner, faster moving films and enables shorter liquid contact times and improved heat transfer coefficients. A heating fluid (2a-1), which may be steam, hot water or any hot fluid with energy to evaporate water from the liquid, is fed to the shell and provides the heat energy needed to heat the liquid to be concentrated and evaporate water from the liquid. The liquid/vapor mixture exits the system (2 a-4). The heated fluid, now in condensed form and/or at a lower temperature, leaves the housing at the bottom (2 a-2). The remaining liquid film and vapor are separated in the lower part of the shell and downstream droplet separators (2 a-8). The concentrated liquid (2a-5) is discharged at the bottom of the separator, while the vapor (2a-6) is collected at the top of the separator. Part of the concentrated liquid may be recycled back to the inlet of the evaporator to ensure that sufficient wetting of the tubes is maintained. The falling-film evaporator is characterized in that mild evaporation is mainly carried out under the vacuum condition, the retention time of liquid in the evaporator is extremely short, the pressure drop is low, the energy efficiency is high, the operation is allowed under the low temperature difference between the process and the heating fluid, the process control is simple, the automation is realized, and the operation is flexible. This type of evaporator is particularly suitable for use with temperature sensitive products.

Based on the above advantages of the falling film evaporator, the reboiler can be replaced with a falling film evaporator. The corresponding process configuration design structure is shown in fig. 2. First, containing CO₂The gas (1) is fed to an absorption unit (2). Gaseous CO₂Is absorbed by the absorption solution (4) flowing in a countercurrent manner. The treated gas (3) being depleted of CO₂Will be derived from CO₂The capture process is vented to the atmosphere or sent for use or other treatment. Rich in CO₂The absorption solution (5) is pumped (6) and flows through two heat exchangers (7) and (8), raising its temperature before it enters the stripping unit (9). The heat exchanger (8) is optional. In case a heat exchanger (8) is used and part of the water can be vaporised from the solution, the water vapour produced can be recovered and injected into the packing of the stripping unit (9) at a lower level for use as stripping gas (not shown). Lean in CO₂The absorption solution (10) is discharged from the stripping unit (9). A portion of stream (10), stream (11), is pumped (17) to an evaporator (21) where the solution is heated and water is evaporated, creating a stream (22). Stream (22) comprises water vapor, a concentrated lean absorption solution, and may also comprise gaseous CO₂. The steam of stream (22) is collected and sent to the stripping unit (9). Leaves the stripping unit(9) Is rich in CO₂The gas (19) may be fed to a condenser (14) where water vapour is condensed. The gas-liquid stream (20d) is then passed to a separator (14a) in which the high CO is present₂The concentrated gas (20b) exits separator (14a) and is sent through compressor/vacuum pump 36 for further use or treatment as stream (20). The condensed water vapour (20a) is returned to the process to be mixed with the regenerated absorption solution (4). Stream (20c) is the process water make-up.

In an alternative configuration design, not shown, stream (22) can be fed to a separator where the gas and liquid phases will be separated and collected separately. The liquid phase (concentrated solution) can be sent back to a reservoir at the bottom of the stripping unit (9) or mixed with stream (10) or (15) to the absorption unit (2). The gaseous phase can then be returned to the stripper (9). In contrast to the food, dairy, pharmaceutical and chemical industries, where both the gas and liquid phases are re-injected in the same process unit (stripping unit (9)), the concentrated solutions and vapors have different fates. Another difference from the conventional use is that less than 20% by weight of the solution needs to be evaporated.

Selecting 2: stripping gas circuit

In a second option, the reboiler is removed from the process and replaced by an external stripping gas loop (fig. 3). The stripping gas loop includes a process for producing stripping gas using a stripping liquid. The stripping liquid in the reservoir (25) is fed (27) to the reboiler (24) and boiled to produce a vapour which is used as stripping gas (28) which is injected into the bottom of the stripping column (9). The stripping gas flows upward through the stripper where it will react with the rich CO₂The absorption solution (stream 5') is contacted so that it can desorb CO₂And evaporates the water. Stripping steam/CO₂The mixture (19) leaves the stripper and is sent to the condenser (14). The stripping gas and water vapour are condensed (26) and transferred to a reservoir (25). The reservoir contains a vapor extract and liquid water. Depending on the nature of the stripping solution, different process configuration designs may be used, as described below. High concentration of CO₂The gas (20b) is compressed (36) and leaves the process (stream 20) for further use or storage. Lean in CO₂Absorption solution leaving vaporThe unit (stream 10) is withdrawn and pumped (pump 16) to the absorption unit (stream 15). Stream (27a) is a makeup stream of vapor extract.

It should also be noted that before stream (27) enters the reboiler (not shown in fig. 3), it may be heated using a heat exchanger to have a temperature closer to the reboiler temperature.

In a first embodiment, stripping vapor (28) may be injected at different heights (28a-28g) along the stripping column, as shown in FIG. 3 a. This configuration design minimizes the temperature gradient across the stripper and improves stripping performance. Steam as stripping gas moves upward through the stripper and contacts the rich CO₂Absorbing the solution. As the absorption solution flows down and due to CO between the stripping gas and the absorption solution₂Concentration gradient, CO₂Is desorbed. Water vapor may also condense into solution. CO-rich leaving the stripper (9)₂The gas (19) contains stripping gas, water vapor and CO₂(ii) a And sent to a condenser (14) where water is condensed and high CO is produced₂A concentration gas (20 b). High CO content₂The strength gas (20b) is then compressed in a compressor (36) and sent as stream (20) to other units for use, treatment and/or storage.

In another embodiment shown in fig. 3b, stripping vapor (28) is injected at the bottom of the stripper. However, in a different part of the stripper, the absorption solution is pumped off, then heated using a heat exchanger, and then returned to the stripping unit. There may be several heating loops, such as 29, 30 and 31, along the height of the stripper. The absorption solution may be withdrawn at the bottom of the packed bed and re-injected at the top of the same packed bed. Alternatively, the absorption solution may be withdrawn at the top of the packed bed and re-injected at the bottom of the same packed bed.

For both embodiments, the number of heating loops or injection ports depends on the column height, the energy required for injection, and the process economics.

The first two embodiments, i.e., different injection locations and heating loops, may also be applied in the process configuration design shown in fig. 2.

With respect to the nature of the stripping solution, the key characteristics of a sufficient stripping solution are as follows:

under stripping operating conditions, it must be in the vapor or gas phase.

The vapor or gas phase must be readily condensable at a temperature slightly below the stripping temperature.

The stripping solution may be selected from water, aqueous solutions and liquid organic compounds having sufficient properties. Liquids or solutions can be divided into two categories: water miscible and water immiscible. Depending on the properties of the liquid or solution, different process configuration designs are possible, as described below.

Steam extraction: aqueous liquid

In a first embodiment, the stripping liquid comprises water. It may be pure water or an aqueous solution, e.g. a salt solution (NaCl, KCl, K)₂CO₃、Na₂CO₃). The salt concentration can be adjusted to achieve the desired boiling temperature. When an aqueous solution is used as the stripping solution, its composition or salt concentration is adjusted so that the boiling temperature of the solution is slightly above the operating temperature of the stripping unit.

The stripping vapor leaving the reboiler has a temperature equal to or slightly higher than the stripping temperature to produce superheated vapor. Preferably, the temperature of the stripping vapor leaving the reboiler is at most 15 ℃ higher than the stripping temperature, more preferably at most 10 ℃ higher than the stripping unit, and most preferably at most 5 ℃ higher than the stripping temperature. The process will be described in figures 3, 3a and 3 b. Since the stripping process is endothermic, it is possible for the stripping vapors to condense in the stripping unit. Thus, water will mix with the aqueous-based absorption solution, diluting the absorption solution and thus changing the process performance. To mitigate the effects of water condensation and absorption solution dilution, different process configuration designs are disclosed and shown in fig. 4, 4a and 4 b.

Referring to fig. 4, 4a and 4b, steam is generated in the stripping gas loop, wherein the stripping liquid is water or a salt solution. The process also includes an evaporation loop to maintain the quality of the absorption solution prior to being fed to the absorption column.

The first process configuration design is shown in fig. 4. The description being focused on condensing in the stripping gas circuit and in the evaporation circuitManagement of stripping vapors. At the bottom of the stripper, the reservoir is divided into two compartments 9a and 9 b. Compartment 9a contains a lean CO₂Absorbing the solution, compartment 9b contains a vapour extract which may be water or an aqueous solution. The liquid in compartment 9b is pumped (pump 44) to the reboiler (24). The liquid is boiled to produce steam (47) and injected as stripping vapor at the bottom of the stripper column (9). The temperature of the steam depends on the solution composition and the operating temperature of the reboiler. The stripping vapor flows upward and contacts the downward flowing CO-containing gas₂Absorbing the solution. When the two streams are contacted, CO₂The water may evaporate from the absorbing solution, the stripping vapor may cool, and a portion of the stripping vapor may condense and join the absorbing solution. Stripping steam with liberated CO₂The gas leaves the stripper (19) together with steam. The gaseous mixture (19) is sent to a condenser (14) where water vapour and stripping vapours are condensed. The gas/liquid mixture (34) is sent to a reservoir (32) where the liquid and gas phases are separated. High CO leaving the accumulator (32)₂The concentrated gas phase (35) is compressed (36) and sent (stream 20) to other processing units, processes or storage units. The liquid phase (40) leaving the accumulator is then mixed with stream (45) before it enters reboiler (24). Lean in CO₂The absorption solution (10), which may have an increased water content due to condensing stripping vapors, is pumped (pump 16) and sent to heat exchangers (7) and (18) before being fed to the absorption unit (2). A portion of stream (15), stream (42), is sent to the evaporation circuit.

The purpose of the evaporation loop is to remove the water added to the absorption solution in the stripper and to recover the original absorption solution composition. The vaporization loop includes a flash tank (48) operating at a pressure less than the pressure of the stripping unit. On entering the flash tank (48), a portion of the water present in the solution will be vaporized. The liquid phase (58) with reduced water content leaving the flash tank (48) is pumped out (pump 59) while stream (60) is mixed with stream (15'). The water vapour produced in the flash tank (57) is sent to a compressor (49) and then to a cooling unit (50) where the water is partially condensed. The gas/liquid mixture (51) is sent to a reservoir (52) where the two phases are separated. Gas phase(53) Is released into the atmosphere. The stream (53) comprises CO₂And water vapor. The liquid phase (54), consisting mainly of water, is recovered, pumped (stream 56) and finally mixed with streams (45) and (40) in the stripping gas loop. Alternatively, stream (54) may be mixed with stream (15').

In an alternative configuration design, the flash tank can be replaced with a falling film evaporator.

A second process configuration design is shown in fig. 4 a. With respect to the stripping gas loop, this second embodiment is similar to the embodiment of fig. 4. In this second embodiment, the additional water present in the absorption solution is removed after it has circulated through the heat exchanger (7) but before it enters the cooler (18). A portion of the stream (15') is sent to a packed column (65). Stream (61) is fed at the top of the column and flows downward through the packing. As it flows, it contacts the dry gas or gas (63) below its water saturation level. A portion of the water present in the absorption solution is vaporized and leaves the packed column with the gas stream (64). Stream (64) may be released to the atmosphere or recycled for other processing. The absorption solution leaving the packed column (62) has a reduced water content and is associated with a lean CO₂The absorption streams (15') are mixed. The mixture (15 ") is then cooled and fed to the absorption column (2).

Fig. 4b shows a third process configuration design. This third embodiment is similar to the embodiment of fig. 4 a. For the previous embodiment, lean in CO₂The extra water present in the absorption solution (15) is removed after it has circulated through the heat exchanger (7) before it enters the cooler (18). A portion (61) of the stream (15') is sent to a packed column (65). Stream (61) is fed at the top of the column and flows downward through the packing. As it flows through it will contact the dry gas or gas below its water saturation level (63 c). A portion of the water present in the absorption solution is vaporized and leaves the packed column with the gas stream (64). Stream (64) may be recovered and sent to heat exchanger (14a) where the gas is cooled and water vapour is condensed. The gas/liquid mixture (34a) is sent to a gas/liquid separator (32 a). The gas stream (35a) leaving the separator (32a) is fed to a fan (36 a). Part of which can then be discharged into the atmosphere (63a) and/or returned (63b) toThe inlet of the packed column (65). The water stream (40a) leaving the separator (32a) is sent back to the stripping gas loop in the reservoir (32). Optionally, and not shown, a portion of stream (40a) may be combined with stream (62) or (15 "). The lean absorption solution (62) leaving the packed tower (65) has a reduced water content and is associated with a lean CO₂The absorbent streams (15 ') are mixed to form a mixture (15'). The mixture (15 ") is then cooled in a cooler (18) and fed to the absorption column (2). Stream (63) is the gaseous make-up stream.

Steam extraction: liquid organic compounds

To be considered a suitable vapor extract, the liquid organic compounds must meet the following criteria:

-to be in the vapour or gaseous state at the operating conditions of the stripping unit.

-in liquid state at a temperature slightly lower than the operating temperature of the stripper.

Immiscible with aqueous solutions. This property will aid in the separation of the organic compound from the aqueous solution and prevent the compound from dissolving in the aqueous solution.

Based on previous criteria, the organic compounds may be:

-hydrocarbons C_xH_yWherein x is 5 or 6

-halogenated hydrocarbon derivatives

Any other compound meeting the above criteria

Some candidate compounds are hexane, cyclohexane, cyclopentane, cis-1, 2-dichloroethylene, 2-methylpentane, trichloroethylene, CHCl₃Perfluorohexane and tetramethylsilane.

An implementation of this strategy is shown in fig. 5. The description focuses on the management of the stripping unit and the stripping gas loop and the condensed stripping vapor. The vapor extract is stored in a reservoir (25). It is transferred (stream 66) to the reboiler (24). The stripping solution is boiled and evaporated, or stripping vapor is generated (47) and injected at the bottom of the stripping column (9). The stripping vapour temperature is higher than the operating temperature in the stripping column (9). The stripping vapor flows upward and contacts the downward flowing CO-containing gas₂Absorbing the solution (5'). As the two streams contact, CO₂From absorption solutionsThe water is released, evaporated from the aqueous absorption solution, and the stripping vapors are cooled, but remain gaseous in the system. The stripping vapor does not condense because its boiling temperature is lower than the temperature in the stripper. Stripping steam with liberated CO₂The gas leaves the stripper together with steam (19). Rich in CO₂The gas (19) is sent to a condenser where the water vapour and stripping vapour are condensed into water and stripping liquid. The water and the stripping solution (26) are transferred to a reservoir (25). Since the two liquid phases are immiscible, they can be separated and then used separately. In the case of a stripping liquid having a lower density than water, the stripping liquid (66) is collected in the upper part of the reservoir and then fed to the boiler (24). The water is recovered (67) and brought into contact with the CO lean water between the heat exchangers (7) and (18)₂The absorption solutions were combined. High CO content₂The concentration gas (20b) is compressed (36) and then leaves the process (20) for further use, treatment or storage. In case the stripping liquid density is larger than water, the process is as shown in fig. 5 a. For both cases, stream (66a) provides stripping solution make-up.

For both configurations, a heat exchanger (8) (as shown in fig. 1 and 2) may be added to heat the rich absorption solution fed at stripping column (9). Similar to the heating loop shown in fig. 3b, may be added at the bottom of the stripper to heat the lean absorption solution present in the reservoir below the packing material. These additions may be required to maintain sufficient temperature conditions in the stripping unit. These additional steps and associated equipment may be combined with the various process embodiments disclosed herein, wherein the stripping column is a packed column.

Selecting 3: external stripping gas

In a third option, the reboiler (12) (fig. 1) is removed from the process. The stripping gas is provided using an external non-condensable (under process conditions) gas. Examples of suitable non-condensable gases are air and nitrogen. The process configuration corresponding to this selection is designed as shown in fig. 6. First, containing CO₂The gas (1) is fed to an absorption unit (2). Gaseous CO₂Is absorbed by the absorption solution (4) flowing in a countercurrent manner. The treated gas (3) is CO-free₂From CO₂Venting to atmosphere during the capture processOr sent for use or additional processing. Rich in CO₂The absorption solution (5) is pumped (pump 6) out and sent to the first heat exchanger (7). Heated CO-rich containing biocatalyst₂The solution (5') is heated in a heat exchanger (8) and then fed to a stripping column (9). The heat exchanger (8) is optional. The solution flows downwards, contacts the stripping gas, leaves the stripper (10) and is pumped (pump 16) to the heat exchanger (7) and then to the heat exchanger (18), while the subsequent stream (4) is fed to the absorption column (2). Stripping gas (68) is injected at the bottom of the stripper packing. The gas flows upwards and contacts the absorption solution, and CO is generated due to the concentration gradient between the gas phase and the liquid phase₂Desorb from solution and water is evaporated. The gas (19) leaving the stripping column (9) is made of CO₂Water and stripping gas. Stream (19) is then fed to condenser (14) where water vapour is condensed and sent back to process (70). Containing CO₂And the stripping gas (69) is vented to atmosphere for storage or for use in different processes.

Referring to FIG. 6a, in another embodiment, the stripping gas (68) may have its temperature increased to increase the concentration gradient between the liquid and gas phases in the stripper and favor CO₂Desorption (fig. 6 a). In this case, the stripping gas (68) is fed to a heat exchanger (72) to heat it, and then stream (71) is fed to the stripper (9). In a second embodiment, the stripping unit may be operated under vacuum conditions. Steam (70a) provides process water make-up. In further embodiments, the stripping gas may be fed at different locations along the stripping unit, as shown in fig. 3 a.

Selecting 4: falling film evaporator as stripping tower (gas-liquid contactor)

The gas-liquid contactor in the stripping unit may also be a falling film evaporator having a plate or tube configuration design. The stripping unit can also consist of several falling-film evaporators connected in series or in parallel. In this case, the packed column, tray column or rotating packed bed would be removed. The corresponding process configuration design is shown in fig. 7, 7a (for parallel evaporators) and 7b (for series evaporators). A description of these embodiments is provided below.

A first process configuration design is provided in fig. 7 and described as follows: first, containing CO₂The gas (1) is fed to an absorption unit (2). Gaseous CO₂Is absorbed by the absorption solution (4) flowing in a countercurrent manner. The treated gas (3) is CO-free₂Will be derived from CO₂The capture process is vented to the atmosphere or sent for use or other treatment. Rich in CO₂The absorbing solution (5) is pumped (6) and flows through a first heat exchanger (7), and the heated stream (5') is fed to a second heat exchanger (8) to raise its temperature before it enters a stripping unit, which is a falling film evaporator (73). The heat exchanger (8) is optional. The heat source will provide the energy needed to evaporate part of the water present in the absorbing aqueous solution. As steam (water vapor) is generated, it acts as a stripping gas and generates a driving force that drives CO in₂Desorption from the absorbing solution. The liquid/vapor mixture (74) is sent to a reservoir (75) where the gas and liquid phases are separated. Liquid phase, i.e. lean in CO₂The absorption solution (15), is pumped (pump 16) to the heat exchanger (7) and then to the cooler (18). The gas phase leaving the accumulator (75), stream (76), is then sent to a condenser where the water vapour is condensed and then sent back to the process (67). High CO leaving the condenser₂The enriched gas (20b) is compressed (36) as stream (20) and sent to other processing, processing or storage units. Stream (67a) provides water make-up for the process.

A process configuration design in which the stripping unit consists of two falling-film evaporators operating in parallel is provided in fig. 7 a. The process comprises the following steps: containing CO₂The gas (1) is fed to an absorption unit (2). Gaseous CO₂Is absorbed by the counter-current flowing absorption solution (4). The treated gas (3) is CO-free₂Will be derived from CO₂The capture process is vented to the atmosphere or sent for use or other treatment. Rich in CO₂The absorption solution (5) is pumped (6) and flows through a first heat exchanger (7), then the heated solution (5') is fed to a second heat exchanger (8) to raise its temperature before it enters a stripping unit designed with two falling-film evaporators in a parallel configuration(73a and 73 b). The heat exchanger (8) is optional. The heat source provides the energy required to evaporate a portion of the water present in the absorbing aqueous solution. When steam (water vapor) is generated, it acts as a stripping gas and generates a driving force for the CO₂Desorption from the absorbing solution. The liquid/vapor mixture leaving units (73a) and (73b), streams (74a and 74b), is sent to reservoir (75) where the gas and liquid phases are separated. In an alternative configuration, streams (74a) and (74b) may be supplied to two separate reservoirs. Liquid phase, i.e. lean in CO₂The absorption solution (15) is pumped (pump 16) towards the heat exchanger (7) and then to the cooler (18). The gas phase leaving the accumulator (75), stream (76) is then sent to a condenser where the water vapour is condensed and then sent back to the process (67). High CO leaving the condenser (14)₂The concentration gas (20b) is compressed (36) and the stream (20) is then sent to other processing, processing or storage units. Stream (67a) provides water make-up for the process.

A process configuration design in which the stripping unit consists of two falling-film evaporators operating in series is provided in figure 7 b. The process comprises the following steps: containing CO₂The gas (1) is fed to an absorption unit (2). Gaseous CO₂Is absorbed by the absorption solution (4) flowing in a countercurrent manner. The treated gas (3) is CO-free₂Will be derived from CO₂The capture process is vented to the atmosphere or sent for use or other treatment. Rich in CO₂The absorption solution (5) is pumped (6) out and flows through the first heat exchanger (7), then the stream (5') is sent to the second heat exchanger (8) to raise its temperature before it enters the first falling-film evaporator (73 a). The heat source will provide the energy needed to evaporate part of the water present in the absorbing aqueous solution. As steam (water vapor) is generated, it acts as a stripping gas and generates a driving force that drives CO in₂Desorption from the absorbing solution. The leaving liquid/vapor mixture (73a) is sent to a reservoir (75a) where the gas and liquid phases are separated. The liquid phase (77) is fed to a second falling-film evaporator, the heat source providing the energy required to evaporate part of the water present in the absorbing aqueous solution. As steam (water vapor) is generated, it acts as a stripping gas and generates a driving force that drives CO in₂From an absorption solutionAnd (4) carrying out medium desorption. The leaving liquid/vapor mixture (73b) is sent to a reservoir (75b) where the gas and liquid phases are separated, i.e. a pump (16) is used to lean the CO₂The absorption solution (15) is pumped to the heat exchanger (7) and then to the cooler (18). The gas streams leaving the accumulator, streams (76a and 76b), are then combined (stream 76) and sent to a condenser (14) where the water vapour is condensed and then sent back to the process (67). High CO leaving the condenser₂The concentration gas (20b) is compressed (36) and the gas stream (20) is then sent to other processing, processing or storage units. Stream (67a) provides water make-up for the process.

An alternative construction design to that shown in fig. 7b is found in fig. 7 c. Differences between the two construction designs were found around the two falling-film evaporators (73a) and (73 b). The process comprises the following steps: containing CO₂The gas (1) is fed to an absorption unit (2). Gaseous CO₂Is absorbed by the absorption solution (4) flowing in a countercurrent manner. The treated gas (3) is CO-free₂Will be derived from CO₂The capture process is vented to the atmosphere or sent for use or other treatment. Rich in CO₂The absorption solution (5) is pumped (6) out and flows through a first heat exchanger (7), then the stream (5') is sent to a second heat exchanger (8) to raise its temperature before it enters the first falling-film evaporator (73 a). The heat source will provide the energy needed to evaporate part of the water present in the absorbing aqueous solution. As steam (water vapor) is generated, it acts as a stripping gas and generates a driving force that drives CO in₂Desorption from the absorbing solution. The liquid/vapor mixture (74a) leaving the evaporator (73a) is sent to a reservoir (75a) where the gas and liquid phases are separated. The liquid phase (77) is fed to a second falling-film evaporator and the gas phase (78) is fed to a second falling-film evaporator operating at a lower pressure than the first evaporator, wherein it is used as a heat source to provide the energy required to evaporate part of the water present in the absorbing aqueous solution. As its heat is transferred to stream (77) in the falling film evaporator, the vapor is condensed, recovered and sent back to the process (stream 80). Residual steam and CO₂(stream 79) is combined with stream (76). As steam (water vapor) is generated, it acts as a stripping gas and generates a driving force that encouragesCO₂Desorption from the absorbing solution. The liquid/vapor mixture leaving evaporator (73b), stream (74b), is sent to a reservoir (75b) where the gas and liquid phases are separated, i.e., lean in CO₂The absorption solution (15) is pumped to the heat exchanger (7) and then to the cooler (18). The gas stream (76) leaving the accumulator 75b is then sent to a condenser (14) where the water vapour is condensed and then sent back to the process (67). High concentration CO leaving the condenser₂The gas (20b) is compressed (36) and the stream (20) is then sent to other processing, processing or storage units. Stream (67a) provides water make-up for the process.

It should be understood that any of the above-described optional aspects of each process, method, system, and unit may be combined with any other aspect thereof, unless the two aspects are clearly not combinable due to their mutual exclusivity.

Results of the experiment

The following examples are intended to demonstrate the effect of boiling a carbonic anhydrase-containing absorption solution on the enzyme half-life in the process and how process configuration design changes, such as the use of air as a stripping gas, affect the enzyme half-life in the process. These examples describe experimental laboratory tests. Of Optimized Gas Treating IncThe software is used where process simulation is required.

Example 1: CO at laboratory Scale₂Determination of 1T1 Carbonic anhydrase half-life in a Capture Unit comprising a reboiler to remove CO from the enzyme-containing 1T1₂Water vapor is generated in the absorption solution (reference process).

The test was conducted to determine the carbonic anhydrase half-life in a laboratory scale capture unit. The process configuration design is shown in fig. 1. The absorption solution was 1.45M K₂CO₃Solution of CO₂The loading is 0.7mol C/mol K⁺. Carbonic anhydrase 1T1 was used at a concentration of 0.5 g/L. CO at the inlet of the absorption column₂The concentration was 12% (v/v) on a dry basis and the gas temperature was 30 ℃.The liquid flow rate was 0.34L/min. The absorption column was operated at an L/G of 15G/G. The temperature of the solution in the absorption column was 30 ℃. The rich absorption solution was heated to 60 ℃ before entering the stripper. The stripper was operated at an absolute pressure of 30 kPa. The lean absorption solution leaving the stripper is at a temperature of 65 ℃ and is split into two streams: the first stream was sent to the absorber column at a flow rate of 0.34L/min. The second stream was fed to the reboiler at a flow rate of 0.76L/min. The reboiler is a plate heat exchanger. Heating and boiling the CO lean stream with a hot water stream at a temperature of 80 ℃ and a flow rate of 5L/min₂The energy required to absorb the solution and produce water vapor. The test was run for several days. During this test, samples were taken at different times for enzyme activity determination. The enzyme half-life was then determined.

For the present process conditions, the water vapor generation rate was 4.5kg/h, while the half-life of the enzyme 1T1 was evaluated as 12 hours.

Example 2: effect of reboiler operating conditions on steam generation Rate and half-life of enzyme 1T1 under the same process configuration design as in example 1

To determine the effect of steam generation rate on half-life of the enzyme 1T1, additional tests were performed. The test conditions were varied around the reboiler and the other conditions were the same as described in example 1. They are looked up in table 1. For each condition, the water vapor generation flow rate was provided as the corresponding half-life of enzyme 1T 1.

TABLE 1 steam Generation Rate as a function of reboiler operating conditions

As can be observed in table 1, the enzyme half-life is affected by the steam generation flow rate. The highest is the steam generation flow rate and the lowest is the half-life of 1T 1.

Example 3: laboratory scale CO with stripping gas being air₂1T1 half-life in the capture unit. The unit was operated in the process configuration design shown in fig. 6a, where a heating loop was present to heat the lean present in the stripper bottoms reservoirAbsorb the solution and maintain sufficient temperature conditions.

The test was conducted to determine the half-life of the carbonic anhydrase in a laboratory scale capture unit in which the stripping gas was air. The absorption solution was 1.45M K₂CO₃Solution of CO₂The loading is 0.7mol C/mol K⁺. Carbonic anhydrase 1T1 was used at a concentration of 0.5 g/L. The schematic of this unit is the same as that shown in figure 6a, where there is an additional heat exchanger to heat the liquid present in the stripper bottom reservoir. CO at the inlet of the absorption column₂The concentration was 13.5% (v/v) and the gas temperature was 30 ℃. The liquid flow rate was 0.35L/min. The absorption column was operated at an L/G of 15G/G. The temperature of the solution in the absorber column was 30 ℃ while the rich absorption solution was heated to 60 ℃ before entering the stripper column. The stripper was operated at an absolute pressure of 45 kPa. The temperature of the solution leaving the stripper was 65 ℃ and was then cooled and fed to the absorber. Air at a temperature of 60 ℃ was fed at the bottom of the stripper at a flow rate of 30 g/min. Initial CO₂The trapping performance was 75%. Under the same conditions, but without the use of enzymes, CO₂The trapping performance was 15%. This confirms that the enzyme 1T1 is towards CO₂The effect of trapping performance. The test was run for several days. During the test, the enzyme activity measurements were performed at different sampling times. The enzyme half-life was then determined.

Under these process conditions, the half-life of 1T1 was 13 days (312 hours). This represents a 2500% increase compared to the basic case presented in example 1. This showed a 225% -1735% increase compared to the other cases in example 2 (table 1). This clearly shows that minimizing digestive enzyme exposure at the high gas/liquid interface is an increase in CO₂The key process parameter of the enzyme half-life in the process is captured.

Example 4: CO 2₂Simulation of a stripping unit comprising a stripping gas loop, wherein the stripping liquid is water, and wherein the generated water vapour is injected at different heights of the stripping packed column-the effect of the number of injection points (fig. 3 a).

1.45M K of enzyme 1T1 containing concentration of 0.5g/L₂CO₃The rich absorption solution is at 6.46X 10⁴Flow rate of kg/h toCO constituted by packed columns₂A stripping unit. The packed column had a height of 25m and a diameter of 1.11 m. The stripping unit was operated at a temperature of 66 ℃ and a pressure of 30 kPa. The stripping gas is steam provided through a stripping gas loop. The rich absorption solution fed to the stripping unit had a temperature of 65 ℃ and a pressure of 150 kPa. Steam was supplied at a pressure of 30kPa and a temperature of 71 ℃.

For the same CO₂Desorption efficiency (47%), simulations were run to determine the effect of the number of water vapor injection points on two parameters: the rate of condensation of water vapor into the absorption solution, the desired total water vapor flow rate. The simulation results are reported in table 2. The location of the injection port is designated as height (m). The position of 0m corresponds to the top of the stripping unit.

TABLE 2

Simulation results show that increasing the number of steam injection points can reduce the steam condensation rate in the stripping unit under this process condition. Another benefit is that the required steam flow is significantly reduced.

In processes where the water vapor condensate in the absorption solution leaves the stripper, process configurations such as those shown in fig. 4, 4a and 4b should be used to design the evaporation of the condensed water vapor and restore the absorption solution composition to its specified value.

Example 5: CO 2₂Simulation of a stripping unit comprising a stripping gas loop, wherein the stripping liquid is water, and wherein the generated water vapor is injected at 9 different injection points — the effect of the rich absorption solution temperature fed to the stripping column unit.

Additional simulations were run to determine the feasibility of injecting water vapor without managing the vapor condensation problem. One contemplated strategy is to heat the rich absorption solution of the stripping unit feed at a higher temperature. The situation considered is to illustrate the effect of higher solution temperature, as described in example 4, where water vapor is injected at 9 different injection ports. The simulation results are shown in table 3.

TABLE 3

The simulation results shown in table 3 clearly show that by increasing the temperature of the rich absorption solution entering the stripping unit, the water vapor condensation rate decreases with the desired steam flow rate. More specifically, the simulation results show that the process conditions can be adjusted to avoid vapor condensation, and therefore, there is no need for an evaporation loop to manage the solution composition.

Example 6: steam injection via stripping gas loop at the bottom of the stripping unit and addition of two heating loops (process configuration design FIG. 3b)

Simulations were run to determine the effect of adding two heating loops to the stripping unit, with steam injected at the bottom of the packed column. The process conditions were as described in example 4. With respect to the two heating circuits, into which the 15% absorption solution is pumped, they comprise a pump and a heat exchanger. The first loop drained the absorption solution at 5m and returned at 5.5 m. The temperature of the solution increased from 60 ℃ to 70 ℃. The second heating loop drained the liquid at 10m and returned at 10.5 m. The temperature of the solution was heated from 63 ℃ to 70 ℃.

The simulation results show that under these process conditions the steam condensation rate is reduced from 740kg/h to 294kg/h, while the required steam flow rate is reduced from 2100kg/h to 1850 kg/h. However, an additional heat load of 0.85GJ/h would be required. Additional simulations by adjusting the solvent flow ratio through the 2 circuits to 25% and 35% show that the steam condensation rate can be reduced to 86kg/h and the steam flow rate reduced to 1700kg/h while an additional heat load of 1.24GJ/h will be required.

Example 7: simulated air stripping

Containing 15% CO₂(v/v) the flue gas will be treated to capture 90% of its CO₂. The flue gas had a temperature of 30 ℃ and a pressure of 111kPa and was fed to 15 t/day CO at a flow rate of 3250kg/h₂A trap unit. The absorption solution fed at the absorption unit was 1.45M K₂CO₃，CO₂The loading is 0.7mol C/mol K⁺. The absorption unit was operated at an L/G of 10 kg/kg. Use ofThe software (process configuration as shown in figure 6a) performs the design of a stripper unit using air as stripping gas. With the stripping unit operating at 30kPa and 70 ℃, an air flow rate of 75kg/h was able to achieve sufficient solvent regeneration while achieving 90% capture unit performance. For the case of a stripping unit operating at 101kPa and a temperature of 70 ℃, an air flow rate of 700kg/h is required. For both cases, the stripper would be 1.15m in diameter and 10m in height, the size and CO run using the reboiler₂The same is true for the capture and wherein the stripping conditions will be a pressure of 30kPa and a temperature of 70 ℃.

These results indicate that air stripping is technically feasible and an interesting alternative to using a reboiler to generate the stripping gas. Furthermore, the fact that the enzyme is not exposed to the reboiler in this process configuration design will result in an increased enzyme half-life, thereby reducing operating costs.