A calcium-based carbon capture-conversion integrated method based on NaAlO2 stable catalysis

Abstract

The present invention discloses a method for integrated calcium-based carbon capture and conversion based on NaAlO2 stable catalysis, relating to the field of carbon dioxide capture and conversion technology. The specific method includes introducing CaO and NaAlO2 into a carbonation reactor to absorb flue gas containing CO2 to generate CaCO3, wherein the NaAlO2 inhibits CaO sintering, making the carbonation reaction more stable; then the generated CaCO3 and NaAlO2 are transferred to a conversion reactor, and biochar is added to undergo an in-situ conversion reaction to obtain high-concentration CO gas and CaO, wherein the NaAlO2 serves as a catalyst and the biochar serves as a reducing agent; the resulting CaO material is then recycled into the carbonation reactor. This method converts CO2 in flue gas into CO in situ, promoting CO2 emission reduction and utilization.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide capture and conversion, and in particular to a calcium-based carbon capture-conversion integrated method based on NaAlO2 stable catalysis. Background Art

[0002] Calcium oxide-based adsorbents are widely used in carbon dioxide capture and storage (CCS) due to their high CO2 capture efficiency, abundant reserves, and low cost. However, calcium oxide-based adsorbents are prone to sintering during the reaction, which reduces reaction stability and affects their effectiveness. Traditional methods for carbon dioxide conversion reactions often use hydrogen or methane as reducing agents, but these methods have the disadvantages of high reaction temperatures, high energy consumption, and easy catalyst deactivation. Summary of the Invention

[0003] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a calcium-based carbon capture-conversion integrated method based on NaAlO2 stable catalysis.

[0004] The technical solutions of the present invention are as follows:

[0005] A method for integrated calcium-based carbon capture and conversion based on NaAlO2 stable catalysis, comprising the following steps:

[0006] S1: Sodium metaaluminate and calcium oxide are added to a carbonation reactor, and flue gas containing carbon dioxide is introduced into the carbonation reactor to allow the calcium oxide to react with the carbon dioxide to form calcium carbonate;

[0007] S2: The sodium aluminate and the generated calcium carbonate in step S1 enter a conversion reactor, biochar is added to the conversion reactor, and the calcium carbonate and biochar undergo an in-situ conversion reaction to produce carbon monoxide and calcium oxide;

[0008] S3: The calcium oxide obtained in step S2 is fed back into the carbonation reactor to cycle through steps S1 and S2.

[0009] As a preferred embodiment of the present invention, the calcium oxide is prepared by calcining limestone or dehydrating calcium hydroxide.

[0010] As a preferred embodiment of the present invention, in step S1, the flue gas includes at least one of coal-fired flue gas, cement plant flue gas, blast furnace gas and fermentation tail gas.

[0011] As a preferred embodiment of the present invention, in step S1, the volume concentration of carbon dioxide in the flue gas is 10-40%.

[0012] As a preferred embodiment of the present invention, in step S1, the temperature in the carbonation reactor is maintained at 600-800°C.

[0013] As a preferred embodiment of the present invention, in step S2, the biochar source includes bamboo charcoal and / or coconut shell charcoal.

[0014] As a preferred embodiment of the present invention, in step S2, the mass ratio of sodium aluminate to biochar is between 2.0 and 4.0, including specific values ​​such as 2.4 and 2.8 and smaller ranges thereof.

[0015] As a preferred embodiment of the present invention, in step S2, the temperature in the conversion reactor is maintained at 800-900°C.

[0016] The present invention has the beneficial effect of increasing the efficiency of converting carbon dioxide into carbon monoxide by adding biochar and sodium metaaluminate. The presence of sodium metaaluminate inhibits the sintering of calcium oxide, thereby enhancing the stability of the cycle process and significantly improving the carbon dioxide conversion efficiency. Furthermore, sodium metaaluminate is recyclable and highly stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 It is the overall flow chart of the present invention;

[0019] Figure 2 1 is a graph showing the cyclic stability of pure CaO and CaO after adding NaAlO2 in Example 1 of the present invention;

[0020] Figure 3 The SEM images of the original CaO and the CaO after ten cycles in Example 2 of the present invention are compared;

[0021] Figure 4 Comparison of CO2 content and conversion rate released by calcination of each reactant in Comparative Examples 1, 2, and 3 of the present invention;

[0022] Figure 5 Graphs showing CO2 production and conversion rates at different NaAlO2 / C mass ratios for Examples 3, 4, and 5 of the present invention;

[0023] Figure 6 Graph showing the CO2 production and conversion rate for different amounts of bamboo charcoal added in Examples 6, 7, and 8 of the present invention;

[0024] Figure 7 Graphs showing the CO2 production and conversion rates at different temperatures for Examples 9, 10, and 11 of the present invention;

[0025] Reference numerals:

[0026] The figures use the biochar-catalyst nomenclature. Numbers prefixed to biochar represent the mass of the biochar, with no number representing 1 g. Numbers prefixed to catalyst represent the mass of the catalyst, with no number representing 1 g. For example, 0.12BC-0.28ANa represents a conversion experiment using 0.12 g of bamboo charcoal and 0.28 g of NaAlO₂. (Abbreviated names are only used in figures or when the description is complex.) DETAILED DESCRIPTION

[0027] The present invention provides a method for integrated calcium-based carbon capture and conversion based on NaAlO2 stable catalysis, comprising the following steps:

[0028] S1: Sodium metaaluminate and calcium oxide are added to a carbonation reactor, and flue gas containing carbon dioxide is introduced into the carbonation reactor to allow the calcium oxide to react with the carbon dioxide to form calcium carbonate;

[0029] S2: The sodium aluminate and the generated calcium carbonate in step S1 enter a conversion reactor, biochar is added to the conversion reactor, and the calcium carbonate and biochar undergo an in-situ conversion reaction to produce carbon monoxide and calcium oxide;

[0030] S3: The calcium oxide obtained in step S2 is fed back into the carbonation reactor to cycle through steps S1 and S2.

[0031] In specific implementation, in step S1, the preparation method of calcium oxide includes but is not limited to limestone calcination, calcium hydroxide dehydration and other preparation methods.

[0032] In specific implementation, in step S1, the flue gas absorbed includes but is not limited to flue gases containing carbon dioxide such as coal-fired flue gas, cement plant flue gas, blast furnace gas and fermentation tail gas. More specifically, the volume concentration of carbon dioxide can be 10%, 20%, 30% or 40%.

[0033] In specific implementation, in step S2, the mass ratio of sodium aluminate to biochar source is between 2.0 and 4.0, and can specifically be 2.0, 2.4, 2.8, 3.0, 3.5 or 4.0.

[0034] In specific implementation, in step S2, the amount of biochar added is between 0.1g and 1.2g, including specific values ​​of 0.1g, 0.5g, 1g or 1.2g, and can be flexibly adjusted to meet specific needs.

[0035] In a specific implementation, in step S1, the temperature in the carbonation reactor is maintained at 600-800°C, specifically 600°C, 650°C or 800°C;

[0036] In specific implementation, in step S2, the temperature in the conversion reactor is maintained at 800-900°C, specifically 800°C, 850°C or 900°C.

[0037] The present invention adds sodium aluminate to the overall reaction, which has two major advantages over other catalysts: (1) it inhibits the sintering of calcium oxide during the reaction of calcium oxide adsorbing carbon dioxide, thereby improving the stability of the reaction; and (2) it has an excellent catalytic effect on the carbon dioxide conversion reaction, which can significantly increase the carbon dioxide conversion rate.

[0038] To facilitate understanding by those skilled in the art, the present invention is further described below with reference to specific embodiments and accompanying drawings. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, rather than all of them. All other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0039] To facilitate understanding by relevant technical personnel, the carbonation and conversion reactor of the present invention undergoes the following reactions.

[0040] Reactions occurring in the carbonation reactor:

[0041] CO2+CaO=CaCO3 Equation 1

[0042] In-situ conversion reactions occurring in the calcination reactor:

[0043] CaCO3+C=2CO+CaO Equation 2

[0044] According to the above equation, if the carbon dioxide conversion rate is to be improved, the progress of equation 2 should be promoted and the stability of calcium oxide in the circulation process should be enhanced. Experimental verification shows that sodium aluminate can be used as a catalyst to promote the progress of equation 2 without reacting with biochar. At the same time, sodium aluminate can inhibit the sintering of calcium oxide and improve the stability of the circulation process.

[0045] Figure 1 This is the overall flow chart of the present invention, specifically, calcium oxide and sodium aluminate are introduced into the carbonation reactor, where they absorb carbon dioxide from flue gas to generate calcium carbonate, and then calcium carbonate and sodium aluminate are introduced into the conversion reactor, where biochar is introduced to undergo in-situ conversion reactions to generate high concentrations of carbon monoxide and calcium oxide, and the generated calcium oxide material is then re-entered into the conversion reactor for recycling. Figure 1 The method and device of the present invention are further explained below.

[0046] Example 1

[0047] The cycling performance of the samples and the sintering inhibition effect after adding NaAlO2 in the same molar ratio as CaO were studied using a thermogravimetric analyzer in a 15% by volume CO2 / N2 atmosphere. Figure 2 The graph below shows the cyclic stability of pure CaO and CaO with the addition of NaAlO2. It is clear that the adsorption capacity of CaO decreases by 37% when no NaAlO2 is added, while it decreases by 32.2% when NaAlO2 is added. This indicates that NaAlO2 can inhibit the sintering of CaO.

[0048] Example 2

[0049] The CaO sample after ten cycles of Example 2 was scanned by electron microscope, and the results are shown in Figure 2. Figure 3 , Figure 3 (a) is the original CaO. It can be seen that its surface is rough and porous with more pores. However, after 10 cycles of conversion, the CaO surface becomes dense and the pore structure gradually decreases, showing a sintered state. Figure 3 (b) shows that there are some fine structures in the pores on the CaO surface. These substances can play the role of inert support skeleton in the pores on the CaO surface, which can protect the spatial structure of CaO during the cycle and reduce the sintering of CaO to a certain extent.

[0050] Comparative Example 1

[0051] Experimental raw materials: 1g calcium carbonate was fully calcined under normal pressure, 800℃, and 100% N2 to completely release CO2 and obtain CaO.

[0052] from Figure 4 It can be seen that the calcination of pure calcium carbonate releases 171.28 mL of CO2, and no CO is produced at this time.

[0053] Comparative Example 2

[0054] Compared with Comparative Example 1, the only difference is that 0.12 g of bamboo charcoal is added to the pure calcium carbonate to carry out the calcination and decomposition process.

[0055] like Figure 4 As shown, compared to the calcination and decomposition of pure calcium carbonate, the addition of bamboo charcoal reduced CO2 production by 30.56 mL, but produced 70.98 mL of carbon monoxide. Adding bamboo charcoal at the same molar ratio to CO2 accelerated CO2 release and converted some CO2 to CO, but the conversion rate was only 20.14%. This demonstrates that bamboo charcoal can indeed convert CO2 into CO simultaneously with its release, but the conversion rate is low.

[0056] Comparative Example 3

[0057] Compared with Comparative Examples 1 and 2, the only difference is that 0.28 g of sodium metaaluminate is added to the pure calcium carbonate and bamboo charcoal to carry out the calcination decomposition process.

[0058] from Figure 4 It can be clearly seen that the conversion rate of carbon dioxide to carbon monoxide increased significantly after the addition of NaAlO2, reaching 47.44%, which is 27% higher than the conversion rate without adding catalyst.

[0059] Conclusion: Comparisons of Examples 1-3 show that pure calcium carbonate released 171.28 mL of carbon dioxide. After adding bamboo charcoal, the conversion rate of carbon dioxide to carbon monoxide was 20.14%. Adding sodium metaaluminate catalyst significantly increased the conversion rate to 47.44%. Therefore, converting captured CO2 to CO using bamboo charcoal is feasible, and the addition of a catalyst can reduce CO2 release and increase CO2 conversion.

[0060] Example 3

[0061] During the experiment, only the content of NaAlO2 was changed, and the other conditions remained unchanged, so that the mass ratio of NaAlO2 / BC reached 2.4. Figure 5 It can be seen that the CO2 and CO production and CO2 conversion rate are 95.60 mL, 161.83 mL and 45.84%, respectively.

[0062] Example 4

[0063] The same as Experimental Example 3, the only difference is that when the NaAlO2 / BC mass ratio increases to 2.8, the CO2 and CO production and the CO2 conversion rate are 92.92 mL, 167.79 mL and 47.45%, respectively.

[0064] Example 5

[0065] The same as Example 4, except that when the NaAlO2 / BC mass ratio is increased to 3.2, the CO2 content is reduced, the CO production is slightly increased, and the CO2 conversion rate is increased to 48.23%.

[0066] Conclusion: It can be seen from Examples 3-5 that increasing the mass ratio of NaAlO2 / BC to 2.8 has reached saturation in promoting the improvement of CO2 conversion rate, and increasing it to 3.2 has little effect. Therefore, the subsequent experiments selected a mass ratio of NaAlO2 / C=2.8 for research.

[0067] Example 6

[0068] In Example 5, the optimal mass ratio of NaAlO2 / BC for calcination is 2.8;

[0069] Figure 6The CO2 and CO production and CO2 conversion rates were calculated for different bamboo charcoal addition levels. The bamboo charcoal addition level was increased from 0.1 to 1, while maintaining the NaAlO2 / BC ratio at 2.8. When the bamboo charcoal addition level was 0.1 g, the CO2 conversion rate was 47.44%.

[0070] Example 7

[0071] The same as Example 6, except that when the amount of bamboo charcoal added was increased from 0.1 to 0.5 g, the CO2 conversion rate increased to 74.66%.

[0072] Example 8

[0073] The same as Example 7, except that when the amount of bamboo charcoal added was increased from 0.5 to 1 g, the CO2 conversion rate increased to 84.91%, meaning that most of the CO2 gas released from the CaCO3 was converted to CO. This indicates that increasing the amount of charcoal increases the contact area between CO2 and bamboo charcoal, thereby enabling sufficient CO2 conversion.

[0074] Example 9

[0075] Through the above examples, the present invention determines the reaction conditions as follows: the mass ratio of NaAlO2 to bamboo charcoal is 2.8, the amount of bamboo charcoal added is 1g, and is recorded as BC-2.8A Na -CaCO3, keep it unchanged and only change the conversion temperature.

[0076] refer to Figure 7 When the conversion temperature is set to 800℃, the carbon monoxide production and carbon dioxide conversion rate are 330.43mL and 89.71%, respectively.

[0077] Example 10

[0078] Compared with Example 9, the only difference is that the gasification temperature is increased to 850°C. Figure 7 , the carbon monoxide production and carbon dioxide conversion rate increased to 360.41mL and 91.34%, respectively.

[0079] Example 11

[0080] Compared with Example 10, the only difference is that the gasification temperature is raised to 900°C. Figure 7 However, the CO peak value had almost no significant change, and the CO production only increased by 2.77 mL to 363.18 mL. The CO2 conversion rate was 91.22%, which was basically the same as that at 850 °C, or even slightly lower than 850 °C.

[0081] Conclusion: Considering the gasification rate and sintering conditions comprehensively, 800℃ and 850℃ are better than 900℃.

[0082] The above descriptions are only preferred embodiments of the present invention. Any technical solution that achieves the purpose of the present invention by substantially the same means shall fall within the scope of protection of the present invention.

Claims

1. A calcium-based carbon capture-conversion integrated method based on NaAlO2 stable catalysis, characterized in that: The following steps are involved: S1: Sodium metaaluminate and calcium oxide are added to a carbonation reactor, and flue gas containing carbon dioxide is introduced into the carbonation reactor to allow the calcium oxide to react with the carbon dioxide to form calcium carbonate; S2: The sodium aluminate and the generated calcium carbonate in step S1 enter a conversion reactor, biochar is added to the conversion reactor, and the calcium carbonate and biochar undergo an in-situ conversion reaction to produce carbon monoxide and calcium oxide; S3: The calcium oxide obtained in step S2 is fed back into the carbonation reactor to cycle through steps S1 and S2.

2. The method of calcium-based carbon capture-conversion integrated method based on NaAlO2 stable catalysis according to claim 1, characterized in that: In step S1, the calcium oxide is prepared by calcining limestone or dehydrating calcium hydroxide.

3. The method of calcium-based carbon capture-conversion integrated with NaAlO2 stable catalysis according to claim 1, characterized in that: In step S1, the flue gas includes at least one of coal combustion flue gas, cement plant flue gas, blast furnace gas and fermentation tail gas.

4. The method of calcium-based carbon capture-conversion integrated with NaAlO2 stable catalysis according to claim 1, characterized in that: In step S1, the volume concentration of carbon dioxide in the flue gas is 10-40%.

5. The method of calcium-based carbon capture-conversion integrated with NaAlO2 stable catalysis according to claim 1, characterized in that: In step S1, the temperature in the carbonation reactor is maintained at 600-800°C.

6. The method of calcium-based carbon capture-conversion integrated method based on NaAlO2 stable catalysis according to claim 1, characterized in that: In step S2, the biochar source includes bamboo charcoal and / or coconut shell charcoal.

7. The method of calcium-based carbon capture-conversion integrated with NaAlO2 stable catalysis according to claim 1, characterized in that: In step S2, the mass ratio of sodium aluminate to biochar is between 2.0 and 4.

0.

8. The method of calcium-based carbon capture-conversion integrated with NaAlO2 stable catalysis according to claim 1, characterized in that: In step S2, the temperature in the conversion reactor is maintained at 800-900°C.

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