Joule thermally driven CO2 rapid desorption method based on hollow fiber carbon membrane

Abstract

The invention provides a Joule thermally driven CO2 rapid desorption method based on a hollow fiber carbon film. The conductive hollow fiber carbon film is used as a reactor; the method comprises the following steps: pumping an absorption solution of saturated CO2 into a tube pass of a membrane reactor, simultaneously applying voltage to a component to generate Joule heat, vacuumizing a shell side of the component, separating desorbed carbon dioxide and barren liquor through a gas-liquid separation tank, and then collecting the desorbed carbon dioxide and barren liquor. The problems of high energy consumption and slow desorption of a traditional process are solved, the energy consumption-rate mutual exclusion dilemma in the amine solution regeneration process is overcome, the phenomena of amine degradation and equipment corrosion are relieved, and the dynamic response speed and comprehensive performance of a desorption system are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of CO2 capture and regeneration, and particularly relates to a method for rapidly desorbing CO2 driven by Joule heat based on a hollow fiber carbon membrane. BACKGROUND

[0002] Carbon capture and renewal refers to the process of separating and recovering carbon dioxide (CO2) from industrial emission sources or the atmosphere and regenerating and utilizing or storing it through technical means. This technology is of great significance for mitigating climate change and achieving the carbon neutralization goal. As a traditional combustion emission source such as a coal-fired power plant and a steel plant, flue gas contains a high content of CO2. The chemical absorption method based on amine solution has become the mainstream technology for post-combustion carbon capture due to its high capture efficiency, high CO2 product purity, mature industrial application foundation and large-scale processing capacity.

[0003] However, the amine solution regeneration process consumes a large amount of heat energy, accounting for about 70% of the overall capture system energy consumption, which seriously affects the economic efficiency of the system. At the same time, this process has an energy consumption-rate dilemma. Reducing the temperature can reduce energy consumption, but the desorption rate decreases exponentially (for example, the rate at 100°C is 5-10 times lower than that at 120°C). Increasing the desorption rate requires heating, which leads to a non-linear increase in energy consumption (energy consumption increases by 15-20% for every 10°C increase in temperature). High temperature also promotes the chemical degradation of amines, leading to amine loss and equipment corrosion, increasing operation and maintenance costs. At the same time, the thermal regeneration system starts and stops slowly, which is not suitable for flexible adjustment and distributed application requirements.

[0004] In recent years, membrane separation technology has shown good prospects in CO2 capture and regeneration due to its mild operation, strong continuity and large unit volume mass transfer area. Coupling membrane separation with amine solution desorption process forms a membrane desorption process, which can realize the rapid separation of CO2 and regeneration of amine solution at a lower temperature, thereby reducing energy consumption and amine degradation risk and improving the dynamic response speed of the system. SUMMARY

[0005] The present application proposes a method for rapidly desorbing CO2 driven by Joule heat based on a hollow fiber carbon membrane to effectively overcome the problems of high energy consumption and slow desorption of traditional processes, solve the energy consumption-rate dilemma in the regeneration process of amine solution, reduce amine degradation and equipment corrosion, and improve the dynamic response speed and comprehensive performance of the desorption system.

[0006] The present application proposes a new low-temperature desorption method combining membrane separation and electric heating, taking polymer hollow fiber membrane as raw material, and making hollow fiber carbon membrane through chemical pretreatment and high-temperature carbonization, and packaging into conductive membrane assembly; taking the membrane assembly as a reactor, pumping the saturated CO2 absorption solution (such as ethanolamine solution) into the reactor tube, generating Joule heat by applying voltage on the hollow fiber carbon membrane, realizing efficient heating of the absorption solution, rapid heating, and thus completing the rapid desorption of CO2 at a lower system temperature, while assisting the shell vacuum drive to promote the migration of desorption products. Desorption at a lower temperature is achieved because the high specific surface area of the membrane realizes rapid gas-liquid separation, reduces the mass transfer resistance of CO2 and promotes the desorption reaction.

[0007] Preferably, the hollow fiber membrane adopts a polymer precursor hollow fiber membrane, and the material is selected from any one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polypropylene (PP) and polyethylene (PE).

[0008] Preferably, the purpose of chemical pretreatment of the hollow fiber membrane is to make the high molecular material membrane have thermal stability, and the specific treatment method is as follows: (1) immerse the commercial hollow fiber membrane in a mixed solution of ethanol and N,N-dimethylformamide with a volume ratio of 3:2, add DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) with a membrane volume:DBU of 4:1, water bath at 70℃ for 3h; (2) immerse the hollow fiber membrane obtained in step (1) in methanol for 12h; (3) hang the hollow fiber obtained in step (2) to dry for 24h, and drop a suitable weight to keep it straight.

[0009] Preferably, the high-temperature carbonization treatment method is as follows: place the chemically pretreated hollow fiber membrane in an inert atmosphere, first heat at a rate of 1℃ / min to 400℃, keep for 120min; then heat to 500℃ and keep for 120min; finally heat to 800℃ and keep for 120min.

[0010] Preferably, when the membrane assembly is packaged, the hollow fiber carbon membrane and the metal tee are in contact through conductive carbon felt, the shell side of the membrane assembly uses an insulating quartz tube to ensure that the current passes through the hollow fiber carbon membrane to generate Joule heat, and the bottom end of the membrane assembly is sealed by a head to ensure that the desorbed CO2 and the lean liquid all cross the membrane into the shell side.

[0011] Preferably, the reactor is connected in series, in parallel or in a combination of series and parallel connection of multiple membrane assemblies to meet different recovery amounts and recovery target requirements.

[0012] Preferably, the concentration of the absorption solution is 10wt%-40wt%, and the reaction temperature is 40-110°C (preferably 50-70°C). In the present application, the CO2 absorption solution can be selected from a variety of, such as ethanolamine, diethanolamine or CO2-absorbing ionic liquid, etc.

[0013] Preferably, the desorbed gas is separated from the lean liquid by a gas-liquid separation tank, and then passes through a serpentine cold trap and a drying tube to remove volatile ethanolamine and water vapor, and CO2 is separated.

[0014] The beneficial guarantees and effects of the present application are as follows:

[0015] 1. The overall system of the present application can realize low-temperature rapid desorption of CO2 at a lower temperature (such as 50-70°C) than the conventional tower regeneration temperature, thereby significantly reducing energy consumption.

[0016] 2. Based on the lower desorption temperature of the present application, the risk of thermal degradation of the amine solution can be significantly reduced, thereby reducing the process operation and equipment maintenance costs. The present application uses PVDF hollow fiber membrane as raw material, and prepares hollow fiber carbon membrane through pretreatment and high-temperature carbonization. By applying voltage to the hollow fiber membrane to generate Joule heat, the ethanolamine solution is efficiently heated and rapidly warmed, so that the rapid desorption of CO2 is completed at a lower system temperature, and the desorption product migration is promoted by the vacuum drive in the shell side. The CO2 flux of this method can reach 0.31594 mol / m 2 s, and the desorption rate is more than 20% in 1.2s residence time.

[0017] 3. Based on the efficient heat transfer process of Joule heat and the high specific surface area of the membrane, the response speed of the system can be accelerated, thereby enhancing its application in dynamic regeneration scenarios and supporting modular and small-sized deployment. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The carbonization program diagram of the hollow fiber membrane is shown;

[0019] Figure 2 The structure diagram of the hollow fiber Joule heat assembly is shown: (a) physical diagram; (b) structure diagram;

[0020] Figure 3 The flowchart of the method for rapid desorption of CO2 driven by Joule heat based on the hollow fiber carbon membrane is shown;

[0021] Figure 4 The desorption performance of the hollow fiber carbon membrane obtained in the example is shown: (a) CO2 flux performance diagram; (b) desorption rate performance diagram.

[0022] Figure 5 The CO2 desorption performance of the comparative example 1 is shown: (a) CO2 flux performance diagram (70°C); (b) desorption rate performance diagram

[0023] Figure 6 shows the CO2 desorption rate of the product of Comparative Example 2 over time DETAILED DESCRIPTION

[0024] The following examples, experimental examples, further illustrate the application and are not to be construed as limiting it. The examples do not include detailed descriptions for conventional methods, which are well known to a person of ordinary skill in the art and are described in many publications.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Furthermore, any method and material similar or equivalent to those described herein can be used in the practice of the present application, the preferred methods and materials being described herein are intended to be illustrative only and not intended to be limiting.

[0026] Unless otherwise indicated, the experimental methods in the following examples were carried out according to conventional procedures or according to the procedures recommended by the manufacturer.

[0027] Example 1

[0028] I. Preparation of hollow fiber carbon membrane joule heat module

[0029] (1) Chemical pretreatment: immerse the commercial PVDF hollow fiber membrane in a mixed solution of ethanol and N,N-dimethylformamide (DMF) with a volume ratio of 3:2, add DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), and water bath at 70°C for 3h; wherein the volume ratio of PVDF to DBU is 4:1.

[0030] (2) Soak the hollow fiber obtained in step (1) in methanol for 12h.

[0031] (3) Hang the hollow fiber obtained in step (3) to dry for 24h, and hang an appropriate weight to keep it straight.

[0032] (4) Carbonize the hollow fiber obtained in step (3) under a nitrogen atmosphere, and the carbonization program is as follows: Figure 1 : first heat to 400°C at a heating rate of 1°C / min, keep for 120min; then heat to 500°C and keep for 120min; finally heat to 800°C and keep for 120min.

[0033] (5) Package the hollow fiber carbon membrane obtained in step (4), keep the contact between the hollow fiber carbon membrane and the metal tee joint through the conductive carbon felt, use an insulating quartz tube for the shell side of the membrane module to ensure that the current passes through the hollow fiber carbon membrane to generate joule heat, and seal the bottom end of the membrane module through a head to ensure that the desorbed CO2 and the lean liquid all cross the membrane into the shell side.

[0034] The structure of the membrane module prepared by the above method is shown in Figure 1. Figure 2 The tube side and shell side are respectively equipped with interfaces at the top, serving as the inlet and outlet.

[0035] II. Membrane-based rapid CO2 desorption

[0036] The CO2 flux calculation formula involved in this invention is as follows:

[0037]

[0038] In the formula, N is the CO2 flux per unit effective area (unit: mol / s). −1 m −2 G (ml / min) is the CO2 flow rate, and A (m³ / min) is the CO2 flow rate. 2 ) is the inner surface area of ​​the hollow fiber membrane.

[0039] The desorption rate calculation formula involved in this invention is as follows:

[0040]

[0041] In the formula, α is the CO2 desorption rate, and G (ml / min) is the CO2 flow rate. It is the flow rate (ml / min) of the ethanolamine-rich solution. It is the volume of CO2 contained in each milliliter of ethanolamine-rich solution (ml / ml).

[0042] Figure 3 The flowchart of the Joule-thermally driven rapid CO2 desorption method based on hollow fiber carbon membranes is shown below.

[0043] (1) Prepare 1L of 30wt% ethanolamine solution and introduce CO2 gas into it at a flow rate of 200ml / min for 5h to prepare saturated ethanolamine solution.

[0044] (2) Use a constant flow plunger pump to pump the saturated ethanolamine solution obtained in step (1) into the tubular side of the membrane contactor in step (5), with the flow rate set to 2 ml / min, 4 ml / min, 6 ml / min, 8 ml / min, and 10 ml / min.

[0045] (3) Apply voltage to the membrane contactor in step (2) using a DC power supply, and monitor the temperature of the membrane contactor with an infrared thermometer gun. The temperature is controlled at 50°C, 60°C and 70°C.

[0046] (4) Use a vacuum pump to evacuate the membrane contactor shell side in step (3). The desorbed gas and lean liquid are separated by a gas-liquid separator and then removed by a serpentine cold trap and a drying tube to remove volatile ethanolamine and water vapor. The remaining CO2 is then measured by a soap bubble flow meter.

[0047] Figure 4 The desorption performance of the hollow fiber carbon membrane obtained in this embodiment is shown: the CO2 flux increases with increasing absorbent flow rate and temperature. The CO2 desorption rate also increases with increasing temperature.

[0048] Comparative Example 1

[0049] This comparative example uses the same membrane module as the example, but does not use the Joule heating method generated by electricity during CO2 desorption.

[0050] (1) Immerse the commercial PVDF hollow fiber membrane in a mixed solution of ethanol and N,N-dimethylformamide in a volume ratio of 3:2, and add DBU (1,8-diazacyclo[5.4.0]undec-7-ene), and keep it in a water bath at 70°C for 3 hours.

[0051] (2) Immerse the hollow cellulose obtained in step (1) in methanol for 12 hours.

[0052] (3) The hollow fiber obtained in step (3) is hung to dry for 24 hours and then weighed with an appropriate weight to maintain its straightness.

[0053] (4) Carbonize the hollow fibers obtained in step (3) under an inert atmosphere. The carbonization procedure is as follows: Figure 1 .

[0054] (5) The hollow fiber carbon membrane obtained in step (4) is encapsulated and the bottom of the membrane contactor is sealed with a cap to ensure that all desorbed CO2 and lean liquid cross the membrane and enter the shell side.

[0055] (6) Prepare 1L of 30wt% ethanolamine solution and introduce CO2 gas into it at a flow rate of 200ml / min for 5h to prepare saturated ethanolamine solution.

[0056] (7) Use a constant flow plunger pump to pump the saturated ethanolamine solution obtained in step (6) into the tubular side of the membrane contactor in step (5), with the flow rate set to 2 ml / min, 4 ml / min, 6 ml / min, 8 ml / min, and 10 ml / min.

[0057] (8) Immerse the membrane contactor from step (7) in a constant temperature water bath, and keep the water bath temperature at 70°C.

[0058] (9) Use a vacuum pump to evacuate the membrane contactor shell side in step (8). The desorbed gas and lean liquid are separated by a gas-liquid separator and then removed by a serpentine cold trap and a drying tube to remove volatile ethanolamine and water vapor. The remaining CO2 is then measured by a soap bubble flow meter.

[0059] Figure 5 The comparison shows the desorption performance of the hollow fiber carbon membrane in this comparative example under external heating conditions, which is much lower than that of the example at the same temperature, with a maximum difference of 78%.

[0060] The CO2 desorption performance obtained in the examples and Comparative Example 1 is shown in Table 1:

[0061] Table 1. Comparison of flux and desorption rate between the examples and the comparative examples (70℃)

[0062]

[0063] Comparative Example 2

[0064] (1) Prepare 1L of 30wt% ethanolamine solution and introduce CO2 gas into it at a flow rate of 200ml / min for 5h to prepare saturated ethanolamine solution.

[0065] (2) Pour 100 ml of the ethanolamine solution obtained in step (1) into a 250 ml round-bottom flask and place a magnetic stir bar inside.

[0066] (3) Immerse the round-bottom flask from step (3) in a constant temperature oil bath and heat it at a stirring speed of 300 r / min and temperatures of 70℃, 90℃ and 110℃ respectively.

[0067] (4) The desorbed gas generated in step (3) is condensed by a spherical condenser and the data is recorded by a CO2 mass flow meter.

[0068] Figure 6 The results show the change in the desorption rate of the ethanolamine solution in this comparative example over time at different temperatures. At temperatures of 70°C and 90°C, the desorption rate of this comparative example was lower than that of the example within 1 hour. At 110°C, this comparative example required 54 minutes of desorption to reach the desorption rate of the example, while the example temperature was 70°C and the residence time was only 1.2 seconds.

[0069] The undescribed parts of this invention are the same as or implemented using existing technology. The applicant declares that this invention is illustrated through the above embodiments, but the invention is not limited to the above detailed methods, i.e., it does not mean that the invention must rely on the above detailed methods to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A Joule-thermally driven rapid CO2 desorption method based on hollow fiber carbon membrane, characterized in that, A conductive hollow fiber carbon membrane is used as the reactor. The CO2 absorption solution is pumped into the reactor tube side, and a voltage is applied to the module to generate Joule heat. The desorbed carbon dioxide and lean liquid are separated and collected by a gas-liquid separator by evacuating the module shell side.

2. The Joule-thermally driven rapid CO2 desorption method based on hollow fiber carbon membrane according to claim 1, characterized in that, The hollow fiber membrane is made of any one of PVDF, PTFE, PP, or PE. The carbonized hollow fiber membrane module contains conductive carbon felt. The absorption solution is selected from ethanolamine, diethanolamine, or ionic liquids that absorb CO2.

3. The Joule-thermally driven rapid CO2 desorption method based on hollow fiber carbon membrane according to claim 2, characterized in that, The conductive hollow fiber carbon membrane undergoes chemical pretreatment and high-temperature carbonization.

4. The Joule-thermally driven rapid CO2 desorption method based on hollow fiber carbon membrane according to claim 3, characterized in that, The chemical pretreatment method is as follows: (1) Immerse the commercial polymer hollow fiber membrane in a mixed solution of ethanol and N,N-dimethylformamide, add DBU, and keep it in a water bath at 70°C for 3 hours; (2) Immerse the hollow cellulose obtained in step (1) in methanol for 12 hours; (3) The hollow fiber obtained in step (2) is hung to dry for 24 hours and then weighed with an appropriate weight to maintain its straightness.

5. The Joule-thermally driven rapid CO2 desorption method based on hollow fiber carbon membrane according to claim 4, characterized in that, The volume ratio of ethanol to N,N-dimethylformamide was 3:2, and the volume ratio of DBU to membrane was 1:

4.

6. The Joule-driven rapid CO2 desorption method based on hollow fiber carbon membrane according to claim 1, characterized in that, The high-temperature carbonization process is as follows: The hollow fiber membrane after chemical pretreatment is placed in an inert atmosphere, and first heated to 400℃ at a certain heating rate and held for 120 min; then heated to 500℃ and held for 120 min; finally heated to 800℃ and held for 120 min.

7. The Joule-thermally driven rapid CO2 desorption method based on hollow fiber carbon membrane according to claim 6, characterized in that, The heating rate for each heating step is 1℃ / min.

8. The Joule-thermally driven rapid CO2 desorption method based on hollow fiber carbon membrane according to claim 1, characterized in that, During membrane module encapsulation, the hollow fiber carbon membrane and the metal tee are kept in contact by conductive carbon felt. The shell side of the membrane module uses an insulating quartz tube, and the bottom of the membrane module is sealed with an end cap. The reactor is composed of multiple membrane modules connected in series, in parallel, or in a combination of series and parallel.

9. The Joule-thermally driven rapid CO2 desorption method based on hollow fiber carbon membrane according to claim 1, characterized in that, The concentration of the absorption solution is 10wt% ~ 40wt%, and the reaction temperature is 40~110℃.

10. The Joule-driven rapid CO2 desorption method based on hollow fiber carbon membrane according to claim 1, characterized in that, The desorbed gas and lean liquid are separated by a gas-liquid separator and then passed through a serpentine cold trap and a drying tube to remove volatile ethanolamine and water vapor, and CO2 is separated out.

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