Organic amine-promoted phase separation solvent type carbon dioxide phase change absorbent and application thereof

Abstract

The invention discloses an organic amine-promoted phase separation solvent type carbon dioxide phase change absorbent and application thereof, and relates to the technical field of carbon dioxide capture and separation. The carbon dioxide phase change absorbent comprises a main absorbent, a phase-splitting accelerant and a solvent, the main absorbent is primary amine or secondary amine, the phase-splitting accelerant is tertiary amine or sterically hindered amine, the solvent is water, and a reaction product of the main absorbent and carbon dioxide is insoluble in the phase-splitting accelerant but soluble in the water. According to the organic amine-phase separation promoting solvent type carbon dioxide phase change absorbent, two kinds of organic amine are adopted as a main absorbent and a phase separation promoter respectively, the main absorbent has a main carbon dioxide loading function, and the phase separation promoter mainly plays a role in promoting liquid-liquid phase separation after the main absorbent absorbs carbon dioxide; the carbon dioxide absorption capacity is high, and meanwhile only a small amount of solution needs to be desorbed, so that sensible heat and latent heat of vaporization generated by water heating evaporation during desorption are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of carbon dioxide capture and separation, and in particular to an organic amine-promoting phase separation solvent type carbon dioxide phase change absorbent and application thereof. Background Art

[0002] At present, the flue gas produced by power plants and industrial boilers burning fossil fuels such as coal, oil, and natural gas contains a large amount of carbon dioxide, and effective treatment methods and prevention measures are needed to reduce its emissions. The methods of carbon dioxide capture include absorption, adsorption, membrane separation, and cryogenic methods. Since flue gas has the characteristics of large emissions and low carbon dioxide partial pressure, the use of chemical absorption to capture carbon dioxide is relatively efficient.

[0003] In the chemical absorption method, organic amine solvents have been widely used in industry due to their high absorption efficiency, renewability, and high purity of desorbed carbon dioxide. However, traditional organic amine solvents have the problem of high energy consumption for carbon dioxide capture.

[0004] In recent years, researchers have proposed using liquid-liquid phase change absorbents to capture carbon dioxide. Phase change absorbents refer to absorbents in which the solution undergoes a phase change during or after the absorption of carbon dioxide, in which carbon dioxide is enriched in one phase in the form of carbamate and bicarbonate. Only the rich phase needs to be desorbed, and the regeneration volume of the absorption liquid is greatly reduced, thereby significantly reducing energy consumption. However, current phase change absorbents still have the problem of low absorption capacity. Summary of the invention

[0005] The purpose of the present invention is to address the problems of high energy consumption and low absorption capacity of existing chemical absorbents for capturing low-concentration carbon dioxide in flue gas, and to propose an organic amine-promoted phase separation solvent type carbon dioxide phase change absorbent and its application, so as to achieve a higher carbon dioxide absorption capacity while requiring less solution to be desorbed, thereby reducing the sensible heat and latent heat of vaporization of water during desorption.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: The present invention provides an organic amine-promoting phase separation solvent type carbon dioxide phase change absorbent, comprising a main absorbent, a phase separation promoter and a solvent, wherein the main absorbent is a primary amine or a secondary amine, the phase separation promoter is a tertiary amine or a hindered amine, the solvent is water, and the product of the reaction between the main absorbent and carbon dioxide is insoluble in the phase separation promoter but soluble in water.

[0007] Furthermore, the main absorbent is at least one of monoethanolamine (MEA), ethylenediamine (EDA) and diethanolamine (DEA).

[0008] Furthermore, the phase separation accelerator is at least one of triethylamine (TEA) and N,N-dimethylethanolamine (DMEA).

[0009] Furthermore, the mass fraction of the main absorbent is 30-40%, the mass fraction of the phase separation accelerator is 30-40%, the mass fraction of water is 20-40%, and the sum of the mass fractions of the main absorbent, the phase separation accelerator and water is 100%.

[0010] The present invention also provides the use of the organic amine-promoting phase separation solvent type carbon dioxide phase change absorbent in the capture of low-concentration carbon dioxide in flue gas, which uses the organic amine-promoting phase separation solvent type carbon dioxide phase change absorbent to perform carbon dioxide phase change absorption-desorption on low-concentration carbon dioxide flue gas, including: (1) Carbon dioxide absorption: Flue gas containing low concentration of carbon dioxide is passed into the carbon dioxide phase change absorbent in the absorption tower. The reaction product of the main absorbent and carbon dioxide is insoluble in the phase separation promoter but soluble in the water phase, thereby achieving liquid-liquid phase separation. The upper liquid phase is a carbon dioxide-poor phase, and the lower liquid phase is a carbon dioxide-rich phase. (2) Carbon dioxide desorption: The lower liquid phase is introduced into the desorption tower, heated to release carbon dioxide, and the lower liquid phase that has released carbon dioxide flows back into the absorption tower and mixes with the upper liquid phase to absorb carbon dioxide again. The desorbed carbon dioxide is condensed and dried for recycling.

[0011] Furthermore, the volume percentage of carbon dioxide contained in the low-concentration flue gas is 9.7% to 29%.

[0012] Furthermore, in step (1), the conditions for carbon dioxide absorption are: absorption temperature is 25-50° C., and absorption pressure is 1-1.1 atmospheres.

[0013] Furthermore, in step (2), the conditions for carbon dioxide desorption are: desorption temperature is 80-120° C., and desorption time is 20-45 min.

[0014] Compared with the prior art, the beneficial technical effects of the present invention are: The organic amine-promoting phase separation solvent type carbon dioxide phase change absorbent of the present invention uses two organic amines as the main absorbent and the phase separation promoter respectively. The reaction product of the main absorbent and carbon dioxide is insoluble in the phase separation promoter but soluble in the water phase, thereby realizing liquid-liquid phase separation. The main absorbent bears the main carbon dioxide load function, and the phase separation promoter mainly plays the function of promoting liquid-liquid phase separation after the main absorbent absorbs carbon dioxide. The upper liquid phase is a carbon dioxide-poor phase, and the lower liquid phase is a carbon dioxide-rich phase. Since both the main absorbent and the phase separation promoter use organic amines, it is achieved that a smaller amount of solution needs to be desorbed while having a higher carbon dioxide absorption capacity, thereby reducing the sensible heat and latent heat of vaporization of water temperature rise during desorption. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is further described below through specific embodiments, but the implementation mode of the present invention is not limited thereto.

[0016] Example 1 An organic amine-phase separation solvent-promoting carbon dioxide phase change absorbent consists of a main absorbent, a phase separation accelerator and a solvent. The main absorbent is monoethanolamine, the phase separation accelerator is triethylamine, and the solvent is water. The mass fraction of monoethanolamine is 30%, the mass fraction of triethylamine is 30%, and the mass fraction of water is 40%.

[0017] Example 2 An organic amine-promoting phase separation solvent type carbon dioxide phase change absorbent consists of a main absorbent, a phase separation accelerator and a solvent, wherein the main absorbent is ethylenediamine, the phase separation accelerator is N,N-dimethylethanolamine, and the solvent is water, wherein the mass fraction of ethylenediamine is 35%, the mass fraction of N,N-dimethylethanolamine is 35%, and the mass fraction of water is 30%.

[0018] Example 3 An organic amine-promoting phase separation solvent type carbon dioxide phase change absorbent consists of a main absorbent, a phase separation accelerator and a solvent, wherein the main absorbent is diethanolamine, the phase separation accelerator is N,N-dimethylethanolamine, and the solvent is water, wherein the mass fraction of diethanolamine is 35%, the mass fraction of N,N-dimethylethanolamine is 35%, and the mass fraction of water is 30%.

[0019] Example 4 An organic amine-phase separation solvent-promoting carbon dioxide phase change absorbent consists of a main absorbent, a phase separation accelerator and a solvent, wherein the main absorbent is monoethanolamine, the phase separation accelerator is N,N-dimethylethanolamine, and the solvent is water, wherein the mass fraction of monoethanolamine is 40%, the mass fraction of N,N-dimethylethanolamine is 40%, and the mass fraction of water is 20%.

[0020] Example 5 This example uses the organic amine-promoting phase separation solvent type carbon dioxide phase change absorbent of Example 1 to capture carbon dioxide from the exhaust gas of a thermal power plant. The carbon dioxide concentration in the exhaust gas of a thermal power plant is 12.7%.

[0021] The flue gas is passed into the carbon dioxide phase-change absorbent in the absorption tower. Under the conditions of absorption temperature of 30°C and absorption pressure of 1.1 atmospheres, the main absorbent reacts with carbon dioxide. The reaction product is insoluble in the phase separation promoter but soluble in the water phase, thereby realizing liquid-liquid phase separation. The upper liquid phase is a carbon dioxide-lean phase, and the lower liquid phase is a carbon dioxide-rich phase. The lower liquid phase is introduced into the desorption tower. Under the condition of desorption temperature of 120°C, the lower liquid phase is heated to release carbon dioxide. The desorption time is 30 minutes. The lower liquid phase that releases carbon dioxide refluxes into the absorption tower and mixes with the upper liquid phase to absorb carbon dioxide again. The desorbed carbon dioxide is recycled after condensation and drying.

[0022] Test Case The organic amine-promoted phase separation solvent type carbon dioxide phase change absorbent of Example 1 was used to conduct a carbon dioxide capture test on a gas with a carbon dioxide concentration of 10%. 100 g of the organic amine-promoted phase separation solvent type carbon dioxide phase change absorbent of Example 1 was prepared.

[0023] A gas with a carbon dioxide concentration of 15% is passed into the carbon dioxide phase-change absorbent, and carbon dioxide is absorbed at an absorption temperature of 50°C and an absorption pressure of 1 atmosphere; at a desorption temperature of 120°C, the lower liquid phase is heated to release carbon dioxide, and the desorption time is 30 minutes.

[0024] 100g of organic amine-promoted phase separation solvent type carbon dioxide phase change absorbent absorbs 12.2g of carbon dioxide to form a liquid-liquid two-phase. The carbon dioxide loading in the lower liquid phase is 11.07g, accounting for 93.4% of the total carbon dioxide absorption. The regeneration efficiency of the organic amine-promoted phase separation solvent type carbon dioxide phase change absorbent is 72%, and the desorption load is 0.89mol·mol -1 .

[0025] Comparative Example A 30 wt% monoethanolamine aqueous solution was used to perform a carbon dioxide capture test on a gas with a carbon dioxide concentration of 10%. 100 g of a 30 wt% monoethanolamine aqueous solution was prepared.

[0026] A gas with a carbon dioxide concentration of 15% is introduced into a 30wt% monoethanolamine aqueous solution, and carbon dioxide is absorbed at an absorption temperature of 50°C and an absorption pressure of 1 atmosphere. At a desorption temperature of 120°C, the lower liquid phase is heated to release carbon dioxide, and the desorption time is 30 minutes.

[0027] 100g of 30wt% monoethanolamine aqueous solution has a carbon dioxide capture rate of 86%, a regeneration efficiency of 58%, and an analytical load of 0.32mol·mol -1 .

[0028] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the technical solution and conceptual invention of the present invention should be included in the protection scope of the present invention.

Claims

1. An organic amine-promoting phase separation solvent type carbon dioxide phase change absorbent, comprising a main absorbent, a phase separation promoter and a solvent, characterized in that: The main absorbent is a primary amine or a secondary amine, the phase separation accelerator is a tertiary amine or a hindered amine, the solvent is water, and the product of the reaction between the main absorbent and carbon dioxide is insoluble in the phase separation accelerator but soluble in water.

2. The organic amine-promoted phase separation solvent type carbon dioxide phase change absorbent according to claim 1, characterized in that: The main absorbent is at least one of monoethanolamine, ethylenediamine and diethanolamine.

3. The organic amine-promoted phase separation solvent type carbon dioxide phase change absorbent according to claim 1, characterized in that: The phase separation accelerator is at least one of triethylamine and N,N-dimethylethanolamine.

4. The organic amine-promoted phase separation solvent type carbon dioxide phase change absorbent according to claim 1, characterized in that: The mass fraction of the main absorbent is 30-40%, the mass fraction of the phase separation accelerator is 30-40%, the mass fraction of water is 20-40%, and the sum of the mass fractions of the main absorbent, the phase separation accelerator and water is 100%.

5. Application of an organic amine-promoted phase separation solvent type carbon dioxide phase change absorbent in capturing low-concentration carbon dioxide in flue gas, characterized in that: The method uses the organic amine-promoting phase separation solvent type carbon dioxide phase change absorbent as described in any one of claims 1 to 4 to perform carbon dioxide phase change absorption and desorption on low-concentration carbon dioxide flue gas, comprising: (1) Carbon dioxide absorption: Flue gas containing low concentration of carbon dioxide is passed into the carbon dioxide phase change absorbent in the absorption tower. The reaction product of the main absorbent and carbon dioxide is insoluble in the phase separation promoter but soluble in the water phase, thereby achieving liquid-liquid phase separation. The upper liquid phase is a carbon dioxide-poor phase, and the lower liquid phase is a carbon dioxide-rich phase. (2) Carbon dioxide desorption: The lower liquid phase is introduced into the desorption tower, heated to release carbon dioxide, and the lower liquid phase that has released carbon dioxide flows back into the absorption tower and mixes with the upper liquid phase to absorb carbon dioxide again. The desorbed carbon dioxide is condensed and dried for recycling.

6. The use according to claim 5, characterized in that: The volume percentage of carbon dioxide contained in the low-concentration flue gas is 9.7% to 29%.

7. The use according to claim 5, characterized in that: In step (1), the conditions for carbon dioxide absorption are: absorption temperature is 25-50° C., and absorption pressure is 1-1.1 atmospheres.

8. The use according to claim 5, characterized in that: In step (2), the conditions for carbon dioxide desorption are: desorption temperature is 80-120° C., and desorption time is 20-45 min.