Calcium-based carbon capture-conversion integrated method based on NaAlO2 stable catalysis

Abstract

The invention discloses a calcium-based carbon capture-conversion integrated method based on NaAlO2 stable catalysis, and relates to the technical field of carbon dioxide capture and conversion, the specific method comprises the following steps: CaO and NaAlO2 are introduced into a carbonation reactor, CO2-containing flue gas is absorbed to generate CaCO3, NaAlO2 plays a role in inhibiting CaO sintering, so that the carbonation reaction is more stable; then the generated CaCO3 and NaAlO2 are transferred into a conversion reactor, charcoal is added for an in-situ conversion reaction, high-concentration CO gas and CaO are obtained, NaAlO2 serves as a catalyst, and charcoal serves as a reducing agent; and the generated CaO material enters the carbonation reactor again for cyclic utilization. According to the method, CO2 in the flue gas is converted into CO in situ, and emission reduction and utilization of CO2 are promoted.

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) because of their high CO2 capture efficiency, abundant reserves and low price. However, calcium oxide-based adsorbents are prone to sintering during the reaction, which reduces the reaction stability and affects their use effect. In the carbon dioxide conversion reaction, traditional methods often use hydrogen and methane as reducing agents, but they have high reaction temperatures, high energy consumption, and easy deactivation of catalysts. 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 solution of the present invention is as follows:

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

[0006] S1: adding sodium aluminate and calcium oxide into a carbonation reactor, and introducing flue gas containing carbon dioxide into the carbonation reactor, so that the calcium oxide reacts with the carbon dioxide to generate 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 the biochar undergo an in-situ conversion reaction to obtain carbon monoxide and calcium oxide;

[0008] S3: The calcium oxide obtained in step S2 is fed back into the carbonation reactor to cycle through the above 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 a smaller range formed thereby.

[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 beneficial effect of the present invention is that the present invention improves the efficiency of converting carbon dioxide into carbon monoxide by adding biochar and sodium aluminate. The presence of sodium aluminate inhibits the sintering of calcium oxide, thereby enhancing the stability of the cycle process and greatly improving the carbon dioxide conversion efficiency. In addition, sodium aluminate has the characteristics of being recyclable and having strong stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 The graph is a cyclic stability graph 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 The graphs of CO2 production and conversion rate at different mass ratios of NaAlO2 / C in Examples 3, 4 and 5 of the present invention are shown;

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

[0024] Figure 7 The graphs of CO2 production and conversion rate at different temperatures for Examples 9, 10, and 11 of the present invention are as follows;

[0025] Reference numerals:

[0026] The figure uses the naming method of biochar-catalyst. Different numbers are added in front of biochar to represent the mass of biochar, and no number is added to represent 1g; numbers are added in front of catalyst to represent the mass of catalyst, and no number is added to represent 1g. For example, 0.12BC-0.28ANa means that 0.12g bamboo charcoal and 0.28g NaAlO2 are used for the conversion experiment (abbreviated names are only used in the figure or when the expression is more complicated). DETAILED DESCRIPTION

[0027] The calcium-based carbon capture-conversion integrated method based on NaAlO2 stable catalysis of the present invention comprises the following steps:

[0028] S1: adding sodium aluminate and calcium oxide into a carbonation reactor, and introducing flue gas containing carbon dioxide into the carbonation reactor, so that the calcium oxide reacts with the carbon dioxide to generate 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 the biochar undergo an in-situ conversion reaction to obtain carbon monoxide and calcium oxide;

[0030] S3: The calcium oxide obtained in step S2 is fed back into the carbonation reactor to cycle through the above 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 the specific implementation, in step S1, the flue gas absorbed includes but is not limited to flue gas 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] During specific implementation, in step S2, the mass ratio of sodium aluminate to the biochar source is between 2.0 and 4.0, and specifically can 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, which can be flexibly adjusted according to actual needs.

[0035] In 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] During 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 greatly improve the carbon dioxide conversion rate.

[0038] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with specific embodiments and drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are 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=CaCO3Equation 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, equation 2 should be promoted and the stability of calcium oxide in the cycle process should be enhanced. Experimental verification shows that sodium aluminate can be used as a catalyst to promote 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 cycle process.

[0045] Figure 1 The overall flow chart of the present invention is as follows, specifically, calcium oxide and sodium aluminate are introduced into a carbonation reactor, carbon dioxide in flue gas is absorbed in the carbonation reactor to generate calcium carbonate, and then calcium carbonate and sodium aluminate are introduced into a conversion reactor, and biochar is introduced to undergo an in-situ conversion reaction to generate high concentrations of carbon monoxide and calcium oxide, and then the generated calcium oxide material is 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 is a cyclic stability graph of pure CaO and CaO after adding NaAlO2. It is obvious that the adsorption capacity of CaO decreased by 37% when no NaAlO2 was added, and decreased by 32.2% after adding NaAlO2. It can be concluded 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 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 pores gradually decrease, showing a sintered state. Figure 3 (b) shows that there are some fine structures in the pores on the CaO surface. These substances can act as an inert support skeleton in the pores on the CaO surface, protecting the spatial structure of CaO during the cycle and reducing 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 in the figure, compared with the calcination and decomposition of pure calcium carbonate, the production of CO2 decreased by 30.56 mL after adding bamboo charcoal, but 70.98 mL of carbon monoxide was produced. Adding bamboo charcoal at the same molar ratio as CO2 made the release time of CO2 earlier and converted part of CO2 into CO, but the conversion rate was only 20.14%. This proves that bamboo charcoal can indeed convert CO2 into CO while releasing it, but its 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 aluminate is added to the pure calcium carbonate and bamboo charcoal to carry out the calcination and decomposition process.

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

[0059] Conclusion: By comparing Comparative Examples 1-3, we can see that the yield of carbon dioxide released by pure calcium carbonate is 171.28 mL. After adding bamboo charcoal, the conversion rate of carbon dioxide to carbon monoxide is 20.14%, and by adding sodium aluminate catalyst, the conversion rate of carbon dioxide to carbon monoxide is greatly increased to 47.44%. Therefore, it is feasible to convert captured CO2 into CO by bamboo charcoal, and adding catalyst can also reduce CO2 release and improve CO2 conversion rate.

[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, the only difference is that when the NaAlO2 / BC mass ratio is increased to 3.2, the CO2 content is reduced, and 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 the embodiment 5, the optimal mass ratio of NaAlO2 / BC for calcination is 2.8;

[0069] Figure 6The CO2, CO production and CO2 conversion rate under different bamboo charcoal addition amounts are shown in Figure 1. The bamboo charcoal addition amount increases from 0.1 to 1, and the NaAlO2 / BC=2.8 is kept constant while increasing the charcoal amount. When the bamboo charcoal addition amount is 0.1g, the CO2 conversion rate is 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, the only difference is that when the amount of bamboo charcoal added is increased from 0.5 to 1g, the CO2 conversion rate increases to 84.91%, that is, most of the CO2 gas released from CaCO3 has been converted into CO. This shows that increasing the amount of charcoal increases the contact area between CO2 and bamboo charcoal, so that CO2 can be fully converted.

[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°C, the carbon monoxide production and carbon dioxide conversion rate are 330.43 mL 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 360.41 mL and 91.34%, respectively.

[0079] Embodiment 11

[0080] Compared with Example 10, the only difference is that the gasification temperature is increased to 900°C. Figure 7 However, there was almost no significant change in the CO peak, 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 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 description is only a preferred implementation mode of the present invention. Any technical solution that achieves the purpose of the present invention by substantially the same means belongs to the protection scope 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: adding sodium aluminate and calcium oxide into a carbonation reactor, and introducing flue gas containing carbon dioxide into the carbonation reactor, so that the calcium oxide reacts with the carbon dioxide to generate 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 the biochar undergo an in-situ conversion reaction to obtain carbon monoxide and calcium oxide; S3: The calcium oxide obtained in step S2 is fed back into the carbonation reactor to cycle through the above steps S1 and S2.

2. The method of calcium-based carbon capture-conversion integrated 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 based on 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 based on 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 based on 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 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 based on 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 based on 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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