Preparation method and application of calcium-magnesium-based carbon dioxide adsorbent from carbide slag

Abstract

The application discloses a preparation method and application of a calcium-magnesium-based carbon dioxide adsorbent of carbide slag, and the calcium-magnesium-based carbon dioxide adsorbent of carbide slag is prepared by taking carbide slag and a magnesium salt as raw materials. The magnesium salt is magnesium carbonate or magnesium nitrate. The calcium-magnesium-based carbon dioxide adsorbent of carbide slag is prepared by calcining the carbide slag-magnesium compound. The prepared calcium-magnesium-based carbon dioxide adsorbent of carbide slag is used for constant-temperature adsorption of carbon dioxide in a temperature range of 550-750 DEG C. The method provided in the application effectively increases the number of pores in the adsorbent, and the magnesium oxide generated by thermal decomposition of the magnesium carbonate and the magnesium nitrate serves as an inert framework, improves the stability of the pore structure in the adsorbent, and improves the adsorption performance of the adsorbent.

Description

Technical Field

[0001] This invention relates to the field of high-temperature carbon dioxide capture materials technology. Specifically, it relates to the preparation method and application of calcium magnesium-based carbon dioxide adsorbent derived from carbide slag. Background Technology

[0002] Coal-fired power plants generate large amounts of carbon dioxide during power generation. Carbon capture, utilization and storage (CCUS) of this carbon dioxide is of great significance for achieving the goal of carbon neutrality.

[0003] Using solid adsorbents to capture carbon dioxide from flue gas generated by coal-fired power plants is a relatively effective method, and these materials can be recycled, resulting in lower costs. However, because the flue gas generated by coal-fired power plants is at a high temperature and in large quantities, inexpensive and high-temperature resistant solid adsorbents should be considered when recovering carbon dioxide from it.

[0004] Currently, CaO-based adsorbents are considered the most promising high-temperature solid adsorbents for large-scale utilization. This adsorbent is commonly used in the calcium cycle process, which primarily utilizes the reaction of CaO with low-density CO2 in flue gas within a carbonation furnace to generate CaCO3. After gas-solid separation, the carbonation furnace removes the flue gas containing a small amount of CO2. The carbonated adsorbent then enters a calcination furnace, where it is calcined with pure oxygen to obtain CaO and a high-concentration CO2 gas stream, achieving CO2 enrichment. After gas-solid separation, the CO2 can be directly stored, while the CaO returns to the carbonation furnace to continue absorbing CO2 from the flue gas, thus achieving the recycling of the adsorbent.

[0005] Carbide slag can be used to prepare CaO adsorbents. Studies have shown that the specific surface area of ​​CaO prepared from carbide slag is 1.6 times that of limestone-derived CaO, and carbide slag contains more Al2O3 than most limestone. Therefore, under the same cycling conditions, the adsorption conversion rate and cycling stability of carbide slag-derived CaO are generally higher than those of limestone-derived CaO.

[0006] Improving the preparation process of CaO-based adsorbents can enhance their adsorption efficiency to some extent. Ma et al., in their paper "Metal oxide-stabilized calcium oxide CO2 sorbent for multi-cycle operation," reported the synthesis of a novel CO2 adsorbent via combustion using carbide slag, Mg(NO3)2·6H2O, and biodiesel byproducts as raw materials. They investigated the effects of preparation conditions and CO2 capture conditions (carbonization and calcination atmosphere) on the adsorbent's CO2 capture capacity. The results showed that adding biodiesel byproducts during adsorbent preparation resulted in a CaO adsorbent with a CaO to MgO mass ratio of 80:20 exhibiting higher CO2 capture capacity and greater cycle stability after combustion at 850℃ for 60 minutes.

[0007] MgO itself is an inert material, which can improve the sintering resistance of materials. Based on this, further efforts to improve the pore structure of CaO-based adsorbents are expected to further improve the adsorption efficiency of CaO-based adsorbents. Summary of the Invention

[0008] Therefore, the technical problem to be solved by the present invention is to provide a preparation method and application of a calcium magnesium-based carbon dioxide adsorbent with better adsorption capacity, which improves the adsorption performance of the adsorbent by improving the preparation process and improving the structure of the adsorbent.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0010] The preparation method of calcium-magnesium-based carbon dioxide adsorbent from carbide slag includes the following steps:

[0011] Step (1): Prepare carbide slag-magnesium composite material using carbide slag and magnesium salt as raw materials; the magnesium salt is magnesium carbonate or magnesium nitrate.

[0012] Step (2): The calcium carbide slag-magnesium composite is calcined. After calcination, the calcium carbide slag calcium-magnesium-based carbon dioxide adsorbent is obtained. The magnesium salt in this invention is a magnesium salt that can generate gas during calcination. The gas generated during calcination can increase the pore structure of the calcium carbide slag calcium-magnesium-based carbon dioxide adsorbent and improve the adsorption capacity of the adsorbent. Isothermal adsorption tests revealed that, under isothermal adsorption conditions at 750℃, the calcium-magnesium-based carbon dioxide adsorbent CX73, prepared using magnesium nitrate and carbide slag as raw materials with a calcium-to-magnesium ratio of 7:3 and employing a method of adding citric acid to form a dispersion, evaporating the liquid, and then calcining at high temperature, showed essentially the same carbon dioxide adsorption capacity compared to the calcium-magnesium-based carbon dioxide adsorbent CT73YS, prepared using magnesium carbonate and carbide slag as raw materials with a calcium-to-magnesium ratio of 7:3 and employing a method of adding acetic acid to form a dispersion, evaporating the liquid, and then calcining at high temperature. This indicates that the calcium-magnesium-based carbon dioxide adsorbent prepared using magnesium nitrate has better adsorption potential than that prepared using magnesium carbonate.

[0013] In the above-mentioned method for preparing calcium magnesium-based carbon dioxide adsorbent from carbide slag, in step (1), the method for preparing the carbide slag-magnesium composite is: directly mixing carbide slag powder and magnesium salt evenly to obtain the carbide slag-magnesium composite.

[0014] In step (2), during calcination, the carbide slag-magnesium composite is calcined by "entering the furnace at the designated temperature" and then cooled to room temperature with the furnace after calcination.

[0015] Alternatively, in step (2), the calcium carbide slag-magnesium composite is calcined using a "two-step calcination" method, i.e., firstly, a first-step calcination and holding is performed at a lower temperature, and then a second-step calcination and holding is performed at a higher temperature. The temperature at which the magnesium salt decomposes to produce gas during calcination is different from the decomposition temperature of calcium carbonate in the calcium carbide slag. The temperature of the two-step calcination is controlled within a specific range near the decomposition temperatures of the magnesium salt and calcium carbonate, which is conducive to the complete decomposition of magnesium salt and calcium carbonate.

[0016] In the above-mentioned method for preparing calcium-magnesium-based carbon dioxide adsorbent from carbide slag, in step (1), the molar ratio of calcium to magnesium in the carbide slag-magnesium composite is (7-9):(1-3); the particle size of the carbide slag powder is less than 74 μm; the particle size of the magnesium salt is less than 74 μm; in the calcium-based adsorbent, Ca is the main component participating in the main step of carbon dioxide capture, while Mg plays a skeletal role, improving its cycle stability by limiting the pore collapse caused by sintering of Ca during the adsorption cycle. The higher the proportion of Mg, the lower the proportion of Ca, leading to a decrease in the adsorption capacity of the composite adsorbent. Although a good skeletal structure is formed, the adsorption capacity is too low, which is not conducive to practical application. In addition, magnesium oxide in the calcium magnesium-based carbon dioxide adsorbent of carbide slag will adsorb some carbon dioxide in the low temperature range, but the specific surface area of ​​magnesium oxide is small and the adsorption capacity is small. Therefore, if the proportion of magnesium element in the carbide slag-magnesium composite obtained in step (1) is too high, it will limit the improvement of the adsorption capacity of the final adsorbent. The present invention controls the molar ratio of calcium to magnesium in the carbide slag-magnesium composite within the range of 7 to 9: 1 to 3, which not only ensures that the final carbide slag calcium magnesium-based carbon dioxide adsorbent has ideal adsorption performance, but also ensures that its pore structure is stable, so that it has ideal cycle stability.

[0017] In step (2), during calcination, the carbide slag-magnesium composite is directly placed into a calcination furnace at 830-850℃ and kept warm for calcination for 2-3 hours;

[0018] Alternatively, in step (2), during calcination, the carbide slag-magnesium composite is first placed directly into a calcining furnace at 330–360°C for a first-step calcination with holding time of 0.8–1.2 h, and then heated to 830–850°C at a heating rate of 8–10°C / min for a second-step calcination with holding time of 2–2.5 h. Excessive calcination temperature and time will reduce the adsorbent activity and the number of alkaline sites; excessively low calcination temperature and short time will result in incomplete decomposition of the dry mixture, leading to a decrease in its adsorption performance.

[0019] In the above-mentioned method for preparing calcium-magnesium-based carbon dioxide adsorbent from carbide slag, the magnesium salt is magnesium carbonate; in step (1), the molar ratio of calcium to magnesium in the carbide slag-magnesium composite is 7:3.

[0020] In step (2), during calcination, the calcium carbide slag-magnesium composite is first placed directly into a calcining furnace at 350℃ for a one-step calcination and holding for 1 hour, and then heated to 850℃ at a heating rate of 10℃ / min for a two-step calcination and holding for 2 hours. During calcination, MgCO3 undergoes dehydration at 25-300℃, and the temperature at which MgCO3 decomposes to produce MgO and CO2 is approximately 300-550℃; the calcium carbide slag undergoes dehydration at 25-380℃, and Ca(OH)2 in the calcium carbide slag decomposes to produce H2O and CaO at 380-470℃, while CaCO3 in the calcium carbide slag decomposes to produce CO2 and CaO at 470-700℃; the two-step calcination in step (2) is beneficial for the more complete decomposition of magnesium carbonate and calcium carbonate, and the carbon dioxide generated during the decomposition of magnesium carbonate is more significantly released, resulting in more carbon dioxide adsorption sites in the final adsorbent and enhanced adsorption capacity.

[0021] In the above-mentioned method for preparing calcium-magnesium-based carbon dioxide adsorbent from carbide slag, the magnesium salt is magnesium carbonate; in step (1), the preparation method of the carbide slag-magnesium composite is as follows:

[0022] First, acetic acid solution is added to a mixture of calcium carbide slag powder and magnesium salts to initiate a reaction. After the reaction is complete, a mixed dispersion A is obtained. Then, the water in mixed dispersion A is evaporated to obtain the calcium carbide slag-magnesium complex. Excess acetic acid is added to the calcium carbide slag-magnesium complex (mainly composed of magnesium carbonate, calcium hydroxide, and calcium carbonate) to dissolve the mixture into an ionic state. At this point, the Ca in the solution... 2+ Mg 2+ A more uniform mixture is beneficial for preparing a well-structured calcium carbide slag-based carbon dioxide adsorbent.

[0023] In step (2), the carbide slag-magnesium composite is calcined using the "heated furnace introduction" method, and then cooled to room temperature with the furnace after calcination. Compared with furnace heating, the heated furnace introduction method shortens the preparation time. Furthermore, the reaction between MgCO3 and Ca(OH)2 is uncontrollable during furnace heating, while the heated furnace introduction method makes the reaction controllable, ensuring that the final adsorbent composition is CaO and MgO.

[0024] In the above-mentioned method for preparing calcium-magnesium-based carbon dioxide adsorbent from carbide slag, in step (1), the reaction temperature is 75-85℃ and the reaction time is 0.5-1h; in the mixed dispersion A, the molar ratio of calcium to magnesium is 7-9:1-3; the concentration of acetic acid in the acetic acid solution is 95wt.%-99.7wt.%; the volume-to-mass ratio of acetic acid solution to magnesium salt is 10-12mL / g; and the water in the mixed dispersion A is evaporated at 115-125℃.

[0025] In step (2), the calcination temperature is 830–850℃ and the calcination time is 3–3.5 h. Acetic acid reacts with magnesium carbonate and carbide slag to generate gas, which improves their miscibility and allows the magnesium element in magnesium carbonate to be released as ions and dissolved in the solution. This is beneficial to the uniform dispersion of calcium and magnesium elements in the adsorbent. In addition, the acetic acid in step (1) is excess acetic acid. During the calcination process, the excess acetic acid will burn to generate a large amount of gas, which plays a role in "pore creation" and improves the adsorption capacity and cycle stability of the adsorbent.

[0026] In the above-mentioned method for preparing calcium-magnesium-based carbon dioxide adsorbent from carbide slag, the magnesium salt is magnesium nitrate; in step (1), the preparation method of the carbide slag-magnesium composite is as follows:

[0027] First, citric acid solution is added to the mixture of carbide slag powder and magnesium salt to carry out the reaction. After the reaction is completed, a mixed dispersion B is obtained. Then, the water in the mixed dispersion B is evaporated to obtain the carbide slag-magnesium composite.

[0028] In step (2), the carbide slag-magnesium composite is calcined using a "warm-to-room" method, and then cooled to room temperature with the furnace after calcination. Direct dry calcination of magnesium nitrate carries a certain risk of explosion; therefore, dissolving magnesium nitrate in an organic solvent and preparing it using a combustion calcination method makes the preparation process safer. During combustion calcination, citric acid burns to produce a large amount of gas, and nitrate ions decompose into nitrogen oxides, which act as "pore-forming" agents, enhancing the adsorption capacity and cycle stability of the adsorbent.

[0029] In the above-mentioned method for preparing calcium-magnesium-based carbon dioxide adsorbent from carbide slag, in step (1), the reaction temperature is 75-85℃ and the reaction time is 0.5-1h; in the mixed dispersion B, the molar ratio of calcium to magnesium is 7-9:1-3; the concentration of citric acid in the citric acid solution is 40wt.%-45wt.%; the volume-to-mass ratio of citric acid solution to magnesium salt is 20-25mL / g; and the water in the mixed dispersion B is evaporated at 115-125℃.

[0030] In step (2), the calcination temperature is 830-850℃ and the calcination time is 3-3.5h.

[0031] In the above-mentioned method for preparing calcium-magnesium-based carbon dioxide adsorbent from carbide slag, when the magnesium salt is magnesium carbonate, in step (1), the preparation method of the carbide slag-magnesium composite is as follows: first, add acetic acid solution to the mixture of carbide slag powder and magnesium salt and stir for 1 hour under constant temperature water bath at 80℃ to carry out the reaction. After the reaction is completed, a mixed dispersion A is obtained; then, the water in the mixed dispersion A is evaporated at 120℃ to obtain the carbide slag-magnesium composite; in the mixed dispersion A, the molar ratio of calcium to magnesium is 7:3; the concentration of acetic acid in the acetic acid solution is 99.7wt.%; the volume mass ratio of acetic acid solution to magnesium salt is 10mL / g; in step (2), during calcination, the carbide slag-magnesium composite is calcined by the method of "entering the furnace at the specified temperature". After calcination, it is cooled to room temperature with the furnace. The calcination temperature is 850℃ and the calcination time is 3 hours.

[0032] When the magnesium salt is magnesium nitrate, the preparation method of the carbide slag-magnesium complex in step (1) is as follows:

[0033] First, citric acid solution was added to the mixture of carbide slag powder and magnesium salt and stirred for 1 hour under constant temperature water bath at 80℃ to carry out the reaction. After the reaction was completed, mixed dispersion B was obtained. Then, the water in mixed dispersion B was evaporated at 120℃ to obtain carbide slag-magnesium composite. In mixed dispersion B, the molar ratio of calcium to magnesium was 7:3. The concentration of citric acid in the citric acid solution was 40wt.%. The volume mass ratio of citric acid solution to magnesium salt was 20mL / g. In step (2), during calcination, the carbide slag-magnesium composite was calcined by "entering the furnace at the specified temperature". After calcination, it was cooled to room temperature with the furnace. The calcination temperature was 850℃ and the calcination time was 3 hours.

[0034] The calcium-magnesium-based carbon dioxide adsorbent prepared by the above-mentioned method is used for isothermal adsorption of carbon dioxide at a temperature of 550–750°C.

[0035] The technical solution of the present invention achieves the following beneficial technical effects:

[0036] 1. This invention selects magnesium carbonate or magnesium nitrate instead of magnesium oxide and uses it together with calcium carbide slag as raw materials to prepare a calcium carbide slag-based carbon dioxide adsorbent with strong adsorption capacity and good cycle stability. This is because: magnesium carbonate and magnesium nitrate can generate gas and magnesium oxide during calcination. The gas generated during calcination increases the number of pores in the calcium carbide slag-based carbon dioxide adsorbent, increasing the adsorption sites near CaO and thus significantly improving its adsorption capacity. Magnesium oxide, as an inert material, can serve as an inert framework for the adsorbent, improving the stability of the pore structure of the calcium carbide slag-based carbon dioxide adsorbent and enhancing its anti-sintering ability, thereby improving the cycle stability of the calcium carbide slag-based carbon dioxide adsorbent. By adjusting the ratio of calcium to magnesium elements to 7:3 and the calcination temperature to 850℃ during adsorbent preparation, a calcium carbide slag-based carbon dioxide adsorbent with good adsorption capacity was obtained. Compared with the traditional carbon dioxide adsorbent obtained by directly dry-mixing magnesium oxide and calcium carbide slag and then calcining, the adsorption capacity of the carbon dioxide adsorbent obtained by dry-mixing magnesium carbonate and calcium carbide slag and then calcining once in this invention can be increased by 11%. Improving the structure of adsorbents using magnesium carbonate or magnesium nitrate has advantages such as lower cost and simpler operation.

[0037] 2. The two-step calcination method used in this invention is beneficial for improving the performance of calcium-based carbon dioxide adsorbents prepared from magnesium carbonate and calcium carbide slag. This is because the decomposition temperatures of magnesium carbonate and calcium carbonate in calcium carbide slag are different. The calcination temperatures in the two steps of this invention are controlled within specific ranges near the decomposition temperatures of magnesium carbonate and calcium carbonate, respectively, and the calcination holding times are controlled within specific durations. This allows for more complete decomposition of both magnesium carbonate and calcium carbonate, and a more significant release of carbon dioxide generated during magnesium carbonate decomposition. This results in more carbon dioxide adsorption sites in the final adsorbent, enhancing its adsorption capacity. Compared to the traditional carbon dioxide adsorbent obtained by directly dry-mixing magnesium oxide and calcium carbide slag and then calcining them once, under the condition that the calcium-magnesium molar ratio is 7:3, the adsorption capacity of the carbon dioxide adsorbent obtained by the two-step calcination method using magnesium carbonate and calcium carbide slag dry-mixing in this invention can be increased by 23.2%.

[0038] 3. This invention utilizes organic acids to improve the performance of the adsorbent. During the high-temperature calcination process to produce CaO, organic acids rapidly release a large amount of gas, providing the adsorbent with a rich pore structure and specific surface area, thereby enhancing its ability to cyclically adsorb CO2. Furthermore, by dissolving calcium carbide slag and magnesium salts in a 7:3 molar ratio using organic acids, calcium and magnesium ions become miscible in the organic acid solution. This results in magnesium oxide being uniformly dispersed around calcium oxide in the final adsorbent. Appropriate amounts of magnesium oxide can better serve as a framework, reducing pore collapse caused by calcium sintering during the adsorption cycle, while not significantly affecting the specific surface area, adsorption capacity, and adsorption ability of the adsorbent, thus contributing to improved adsorption performance. Compared with the traditional carbon dioxide adsorbent obtained by directly dry mixing magnesium oxide and calcium carbide slag and then calcining it once, the adsorption capacity of the carbon dioxide adsorbent prepared by acetic acid, magnesium carbonate and calcium carbide slag in this invention can be increased by 27.6% under the condition that the calcium-magnesium molar ratio is 7:3; the adsorption capacity of the carbon dioxide adsorbent prepared by citric acid, magnesium nitrate and calcium carbide slag can be increased by 26.8%. Attached Figure Description

[0039] Figure 1 Figure showing the test results of the temperature-dependent adsorption performance of CT91 in this embodiment of the invention;

[0040] Figure 2 Figure showing the test results of the temperature-dependent adsorption performance of CT82 in this embodiment of the invention;

[0041] Figure 3 Figure showing the test results of the temperature-dependent adsorption performance of CT73 in this embodiment of the invention;

[0042] Figure 4 The temperature-dependent adsorption performance test results of CaO-Car in the comparative example of this invention are shown in the figure.

[0043] Figure 5 A comparison of the adsorption amounts of CT91, CT82, CT73, CaO-Car, Ca(OH)2, and Car during temperature-dependent adsorption in this invention;

[0044] Figure 6 A comparison of adsorption rates of CT91, CT82, CT73, and CaO-Car during temperature-dependent adsorption in this invention;

[0045] Figure 7 Figure showing the test results of the isothermal adsorption performance of CT73 at 550℃ in an embodiment of the present invention;

[0046] Figure 8 Figure showing the test results of the isothermal adsorption performance of CT82 at 550℃ in an embodiment of the present invention;

[0047] Figure 9Figure showing the test results of the isothermal adsorption performance of CT91 at 550℃ in an embodiment of the present invention;

[0048] Figure 10 The graph shows the test results of the CaO-Car adsorption performance at 550℃ in the comparative example of this invention.

[0049] Figure 11 Figure showing the test results of the isothermal adsorption performance of CT73 at 650℃ in an embodiment of the present invention;

[0050] Figure 12 Figure showing the test results of the isothermal adsorption performance of CT82 at 650℃ in an embodiment of the present invention;

[0051] Figure 13 Figure showing the test results of the isothermal adsorption performance of CT91 at 650℃ in an embodiment of the present invention;

[0052] Figure 14 The graph shows the test results of the CaO-Car adsorption performance at 650℃ in the comparative example of this invention.

[0053] Figure 15 Figure showing the test results of the isothermal adsorption performance of CT73 at 750℃ in an embodiment of the present invention;

[0054] Figure 16 Figure showing the test results of the isothermal adsorption performance of CT82 at 750℃ in an embodiment of the present invention;

[0055] Figure 17 Figure showing the test results of CT91 at 750℃ isothermal adsorption performance in an embodiment of the present invention;

[0056] Figure 18 The graph shows the test results of the CaO-Car adsorption performance at 750℃ in the comparative example of this invention.

[0057] Figure 19a A comparison of the adsorption capacity of CaO-Car at different isothermal adsorption temperatures in the embodiments of the present invention;

[0058] Figure 19b Comparison of adsorption capacity of CT73 at different isothermal adsorption temperatures in this invention embodiment;

[0059] Figure 19c A comparison of the adsorption capacity of CT82 at different isothermal adsorption temperatures in the embodiments of the present invention;

[0060] Figure 19d A comparison of the adsorption capacity of CT91 at different isothermal adsorption temperatures in the embodiments of the present invention;

[0061] Figure 20aA schematic diagram comparing the adsorption capacities of CT91, CT82, CT73 and CaO-Car at a constant temperature of 550℃ in this embodiment of the invention.

[0062] Figure 20b A schematic diagram comparing the adsorption capacities of CT91, CT82, CT73 and CaO-Car at a constant temperature of 650℃ in this embodiment of the invention.

[0063] Figure 20c A schematic diagram comparing the adsorption capacities of CT91, CT82, CT73 and CaO-Car at a constant temperature of 750℃ in this embodiment of the invention.

[0064] Figure 21 Comparison of the 750℃ isothermal adsorption performance test results of CT73 and CO73 in the comparative examples of this invention;

[0065] Figure 22 Figure showing the test results of the isothermal adsorption performance of second-order CT73 at 750℃ in an embodiment of the present invention;

[0066] Figure 23 Figure showing the test results of the isothermal adsorption performance of CT73YS at 750℃ in an embodiment of the present invention;

[0067] Figure 24 Comparison of the isothermal adsorption performance of CT73YS, second-order CT73, CT73 and CO73 at 750℃ in this invention;

[0068] Figure 25a Figure showing the test results of the isothermal adsorption performance of CX73 at 550℃ in an embodiment of the present invention;

[0069] Figure 25b Figure showing the test results of the isothermal adsorption performance of CX73 at 650℃ in an embodiment of the present invention;

[0070] Figure 25c Figure showing the test results of the isothermal adsorption performance of CX73 at 750℃ in an embodiment of the present invention;

[0071] Figure 26a Figure showing the test results of the isothermal adsorption performance of CX82 at 550℃ in an embodiment of the present invention;

[0072] Figure 26b Figure showing the test results of the isothermal adsorption performance of CX82 at 650℃ in an embodiment of the present invention;

[0073] Figure 26c Figure showing the test results of the isothermal adsorption performance of CX82 at 750℃ in an embodiment of the present invention;

[0074] Figure 27a Figure showing the test results of the isothermal adsorption performance of CX91 at 550℃ in an embodiment of the present invention;

[0075] Figure 27b Figure showing the test results of the isothermal adsorption performance of CX91 at 650℃ in an embodiment of the present invention;

[0076] Figure 27c Figure showing the test results of the isothermal adsorption performance of CX91 at 750℃ in an embodiment of the present invention;

[0077] Figure 28a A comparison of the adsorption capacities of CX73, CX82, and CX91 at a constant temperature of 550℃ in the embodiments of the present invention;

[0078] Figure 28b A comparison of the adsorption capacities of CX73, CX82, and CX91 at a constant temperature of 650℃ in the embodiments of the present invention;

[0079] Figure 28c A comparison of the adsorption capacities of CX73, CX82, and CX91 at a constant temperature of 750℃ in the embodiments of the present invention;

[0080] Figure 29a Comparison of adsorption capacity of CX73 at different isothermal adsorption temperatures in the embodiments of the present invention;

[0081] Figure 29b Comparison of adsorption capacity of CX82 at different isothermal adsorption temperatures in the embodiments of the present invention;

[0082] Figure 29c A comparison of the adsorption capacity of CX91 at different isothermal adsorption temperatures in the embodiments of the present invention. Detailed Implementation

[0083] The following description is based on specific embodiments.

[0084] Example 1

[0085] The method for preparing calcium magnesium-based carbon dioxide adsorbent using magnesium carbonate and calcium carbide slag in this embodiment is as follows:

[0086] Step (1) Mix calcium slag powder and magnesium carbonate directly and evenly according to the ratio of calcium to magnesium elements of 9:1 to obtain calcium slag-magnesium complex; calcium slag powder and magnesium salt are both passed through a 200-mesh sieve and the particle size is less than 74μm.

[0087] Step (2) The calcium carbide slag-magnesium composite was placed in a muffle furnace heated to 850°C for calcination. The calcination was carried out at 850°C for 3 hours to obtain calcium carbide slag calcium magnesium-based carbon dioxide adsorbent (denoted as CT91).

[0088] Example 2

[0089] The method for preparing the calcium-magnesium-based carbon dioxide adsorbent from carbide slag in this embodiment differs from that in Example 1 only in that: in step (1), the carbide slag powder and magnesium carbonate are directly mixed evenly according to a calcium-to-magnesium molar ratio of 8:2 to obtain the carbide slag-magnesium composite. The calcium-magnesium-based carbon dioxide adsorbent prepared in this embodiment is designated as CT82.

[0090] Example 3

[0091] The method for preparing calcium-magnesium-based carbon dioxide adsorbent from carbide slag in this embodiment differs from that in Example 1 only in that: in step (1), the carbide slag powder and magnesium carbonate are directly mixed evenly according to a molar ratio of calcium to magnesium of 7:3 to obtain a carbide slag-magnesium composite. The calcium-magnesium-based carbon dioxide adsorbent prepared in this embodiment is designated as CT73.

[0092] Comparative Example 1

[0093] This comparative example does not add magnesium salts; calcium-based carbon dioxide adsorbent (denoted as CaO-Car) is prepared using only carbide slag (Car) as raw material. During preparation, carbide slag powder is directly placed into a muffle furnace at 850℃ and calcined for 3 hours to obtain the calcium-based carbon adsorbent CaO-Car.

[0094] Isothermal adsorption tests were conducted on CT91, CT82, CT73 and CaO-Car prepared in Examples 1 to 3 and Comparative Example 1 under different temperature conditions.

[0095] To ensure that the amount of calcium in each adsorbent tested was the same, 10.78 mg of CT91, 11.785 mg of CT82, 13.06 mg of CT73 and 10 mg of CaO-Car were taken respectively, and the above adsorbents were placed in a mixed atmosphere of CO2 and N2 and the CO2 adsorption performance was tested at a constant temperature.

[0096] To test the adsorption performance of adsorbents, a Netzsch STA449 thermogravimetric analyzer was used to measure the adsorption temperature, adsorption capacity, and adsorption rate of various adsorbents. The test results were characterized using TG / DTG curves. In the thermogravimetric curve (TG curve), the ordinate (Weight wt.%) represents the mass fraction, and the abscissa represents temperature or time. The derivative dm / dt of the TG curve, representing the rate of mass change, is plotted on the ordinate, with the abscissa representing temperature or time, thus yielding the derivative thermogravimetric (DTG) curve.

[0097] The temperature and time conditions for the isothermal adsorption tests of CT91, CT82, CT73 and CaO-Car were as follows: isothermal adsorption at 550℃ for 120 min, isothermal adsorption at 650℃ for 170 min, and isothermal adsorption at 750℃ for 240 min.

[0098] The above isothermal adsorption test results are as follows: Figures 7 to 10 The figures show the adsorption capacity test results of CT73, CT82, CT91, and CaO-Car in a 550℃ isothermal adsorption test. In the figure, the increase in CO2Uptake (wt.%) after 0 min represents the mass of carbon dioxide adsorbed by the tested adsorbents, and Der i v. Wei ght (% / min) represents the derivative of the adsorbent mass of carbon dioxide adsorbed with respect to time. As shown in the figure, within 120 minutes, CT73 adsorbed 23.05 wt.% of carbon dioxide, CT82 adsorbed 22.09 wt.%, CT91 adsorbed 21.48 wt.%, and CaO-Car adsorbed 20.3 wt.%.

[0099] Figures 11 to 14 The figures show the carbon dioxide adsorption results of CT73, CT82, CT91, and CaO-Car in a 650℃ isothermal adsorption test. As shown in the figure, within 170 minutes, CT73 adsorbed 36.16 wt.% carbon dioxide, CT82 adsorbed 33.86 wt.% carbon dioxide, CT91 adsorbed 33.47 wt.% carbon dioxide, and CaO-Car adsorbed 24.89 wt.% carbon dioxide.

[0100] Figures 15 to 18 The figures show the carbon dioxide adsorption results of CT73, CT82, CT91, and CaO-Car in a 750℃ isothermal adsorption test. As shown in the figure, within 240 minutes, CT73 adsorbed 48.66 wt.% carbon dioxide, CT82 adsorbed 47.57 wt.% carbon dioxide, CT91 adsorbed 45.61 wt.% carbon dioxide, and CaO-Car adsorbed 43.8 wt.% carbon dioxide.

[0101] The results of the above isothermal adsorption tests were grouped to compare the effect of adsorption temperature on the adsorption capacity of different adsorbents. The results are as follows: Figures 19a-19d As shown in Figure 19~ Figure 19d It can be seen that for the four adsorbents (CT91, CT82, CT73, and CaO-Car), the higher the adsorption temperature, the better the adsorption effect. Comparing the adsorption effects of the four adsorbents with different molar ratios of calcium to magnesium, the results are as follows... Figures 20a-20c As shown. By Figures 20a-20cIt can be seen that the dry mixing of calcium carbide slag and magnesium carbonate has a positive effect on the adsorption capacity of calcium carbide slag-based adsorbents. Among them, at 750℃, the adsorption capacity (adsorption amount) of adsorbent (CT73) reaches its maximum when the molar ratio of calcium to magnesium is 7:3. The presence of magnesium oxide will promote the increase of adsorbent adsorption capacity.

[0102] Temperature-dependent adsorption tests were performed on CT91, CT82, CT73 and CaO-Car prepared in Examples 1 to 3 and Comparative Example 1, respectively.

[0103] The mass of each adsorbent used in the temperature-switching adsorption test is the same as that used in the isothermal adsorption test described above. The test method for the temperature-switching adsorption test is as follows: the adsorbent is placed in a mixed atmosphere of CO2 and N2, and the temperature is increased from 90°C at a rate of 10 K / min. The changes in the adsorption performance of each adsorbent during the temperature change process are recorded.

[0104] Figures 1 to 4 The figures show the temperature-dependent adsorption performance test results for CT91, CT82, CT73, and CaO-Car, respectively. Weight (wt.%) represents the mass of the adsorbent, and the increase in adsorbent mass is the mass of carbon dioxide adsorbed. Der iv.Weight (% / ℃) represents the derivative of the adsorbent mass with respect to temperature. As shown in the figures, CT91 can adsorb carbon dioxide in the temperature range of 300–800℃, with the highest adsorption rate in the temperature range of 550–770℃, reaching a maximum adsorption rate at 770℃, and a total carbon dioxide adsorption capacity of 33.68 wt.%. CT82 can also adsorb carbon dioxide in the temperature range of 300–800℃, with the highest adsorption rate in the temperature range of 550–770℃, reaching a maximum adsorption rate at 770℃, and a total carbon dioxide adsorption capacity of 30.5 wt.%. CT73 can adsorb carbon dioxide in the temperature range of 300–800℃, with the highest adsorption rate in the temperature range of 550–770℃, reaching a maximum adsorption rate at 770℃, and the total adsorbed carbon dioxide amount is 29.56 wt.%. CaO-Car can also adsorb carbon dioxide in the temperature range of 300–770℃, with the highest adsorption rate in the temperature range of 550–760℃, reaching a maximum adsorption rate at 760℃, and the total adsorbed carbon dioxide amount is 40.54 wt.%.

[0105] By comparing the carbon dioxide adsorption capacity of CT91, CT82, CT73, CaO-Car, Ca(OH)2, and Car (pure carbide slag) with the same amount of calcium element content during temperature-dependent adsorption, the following results were obtained: Figure 5The results are shown. CaO-Car has the largest carbon dioxide adsorption capacity (total adsorption capacity of 40.54%), CT73 has a smaller capacity (total adsorption capacity of 29.56%), and CT82 and CT91 have similar carbon dioxide adsorption capacities (CT82 has a total adsorption capacity of 30.5% and CT91 has a total adsorption capacity of 33.68%).

[0106] Comparing the carbon dioxide adsorption rates of CT91, CT82, CT73, and CaO-Car for temperature-dependent adsorption, the following results were obtained: Figure 6 The results are shown in the figure. As can be seen from the figure, the maximum adsorption rate of the four sets of curves is distributed between 750 and 770℃. Among them, CT73, CT82, and CT91 have an absorption rate peak at around 420℃. It is speculated that MgO adsorbs CO2 to form MgCO3 at a temperature of around 420℃.

[0107] Based on the above isothermal and temperature-switching adsorption experiments, it can be seen that the calcium-magnesium-based carbon dioxide adsorbents prepared in Examples 1-3 exhibit inferior adsorption performance compared to magnesium-free CaO-Car adsorbents when used for temperature-switching adsorption. However, when used for isothermal adsorption, the adsorption performance of CT73, CT82, and CT91 is significantly better than that of CaO-Car. During isothermal adsorption, CT73 showed the best adsorption performance, especially under the experimental conditions of 750℃ isothermal adsorption for 240 min, where the total carbon dioxide adsorption capacity of CT73 reached 48.66 wt.%.

[0108] Example 4

[0109] The method for preparing calcium magnesium-based carbon dioxide adsorbent using magnesium carbonate and calcium carbide slag in this embodiment is as follows:

[0110] Step (1): The calcium slag and MgCO3 were directly mixed evenly according to the molar ratio of calcium to magnesium of 7:3 to obtain calcium slag-magnesium complex; the calcium slag powder and magnesium salt were both passed through a 200-mesh sieve and the particle size was less than 74μm.

[0111] Step (2): First, place the calcium carbide slag-magnesium composite directly into a muffle furnace that has been heated to 350°C and calcine at 350°C for 1 hour. Then, raise the temperature to 850°C at a heating rate of 10°C / min and calcine at 850°C for 2 hours to obtain calcium carbide slag calcium magnesium-based carbon dioxide adsorbent (denoted as second-order CT73).

[0112] Example 5

[0113] The preparation method of the calcium magnesium-based carbon dioxide adsorbent based on calcium carbide slag in this embodiment is as follows:

[0114] Step (1): Mix calcium carbide slag and magnesium carbonate evenly according to the molar ratio of calcium to magnesium of 7:3, add acetic acid solution to the mixture, and magnetically stir for 1 hour under constant temperature water bath at 80℃ to allow the reaction to proceed. After the reaction is completed, mixed dispersion A is obtained. The concentration of acetic acid in the acetic acid solution used is 99.7wt.%; the volume mass ratio of acetic acid solution to magnesium carbonate is 10mL / g. Place mixed dispersion A in an oven at 120℃ and heat for more than 10 hours to foam and dry mixed dispersion A (during the drying process, mixed dispersion A will produce foaming phenomenon), thus obtaining calcium carbide slag-magnesium composite.

[0115] Step (2): The calcium carbide slag-magnesium composite obtained in step (1) is loaded into a muffle furnace heated to 850°C and calcined at 850°C for 3 hours to obtain calcium carbide slag calcium magnesium-based carbon dioxide adsorbent (denoted as CT73YS). The main components of CT73YS are calcium oxide and magnesium oxide.

[0116] Comparative Example 2

[0117] Preparation of calcium-magnesium-based carbon dioxide adsorbent from carbide slag in this comparative example: The carbide slag and magnesium oxide were dry-mixed and shaken according to the molar ratio of calcium to magnesium of 7:3, and then placed in a muffle furnace heated to 850℃ and calcined at 850℃ for 3 hours to obtain the calcium-magnesium-based carbon dioxide adsorbent from carbide slag (denoted as CO73).

[0118] The adsorption performance of the adsorbents prepared in Examples 4 to 5 and Comparative Example 2 was tested using a Netzsch STA449 thermogravimetric analyzer, and compared with the adsorption performance of CT73 prepared in Example 3. The mass of CT73 used in the test was 13.06 mg, and the masses of CO73, second-order CT73, and CT73YS were determined according to the principle that the amount of calcium-containing substances was the same as that of CT73. The test conditions were as follows: the four adsorbents were placed in a mixed atmosphere of CO2 and N2, and isothermal adsorption tests were conducted at 750°C for 160 min.

[0119] like Figure 21 This study compares the total carbon dioxide adsorption capacity of CT73 and CO73 after 160 min of adsorption at 750℃. During the 160 min adsorption period, CO73 adsorbed 41.35 wt.%, while CT73 adsorbed 46.02 wt.%. Compared to CT73, CO73's total carbon dioxide adsorption capacity was 4.67 wt.%. This is because CT73 undergoes calcination during preparation to generate CO2 gas, which increases the number of micropores and mesopores in the adsorbent, creating more adsorption sites near CaO and thus enhancing the adsorbent's carbon dioxide adsorption capacity.

[0120] Figure 22 and Figure 23 The total carbon dioxide adsorption capacity of the second-stage CT73 and CT73YS after 160 min at 750℃ is measured. Within 160 minutes, the carbon dioxide adsorption capacity of the second-stage CT73 was 50.94 wt.%, and that of CT73YS was 52.76 wt.%.

[0121] The comparison of the isothermal adsorption capacities of CT73YS, second-order CT73, CT73, and CO73 at 750℃ for 160 min is shown in the figure below. Figure 24 As shown, the carbon dioxide adsorption capacities of the four adsorbents under isothermal conditions at 750℃, from largest to smallest, are: CT73YS (52.76 wt.%), second-order CT73 (50.94 wt.%), CT73 (46.02 wt.%), and CO73 (41.35 wt.%). This result indicates that the addition of acetic acid significantly improves the isothermal adsorption capacity of the adsorbents. This is because the addition of acetic acid makes calcium and magnesium ions miscible in the acetic acid solution, and the combustion of acetic acid during the high-temperature preparation process further develops the pore structure of the adsorbent, greatly improving its adsorption capacity. Furthermore, when directly mixing calcium carbide slag and magnesium carbonate to prepare the calcium carbide slag-magnesium composite, the two-step calcination method also contributes to improving the isothermal adsorption capacity of the adsorbent. This is because calcining twice, at the decomposition temperatures of magnesium carbonate and calcium carbonate respectively, results in more complete sample decomposition, and the carbon dioxide released from the decomposition of magnesium carbonate is more pronounced, generating more carbon adsorption sites and enhancing the ability of the calcium-based adsorbent to adsorb carbon dioxide.

[0122] Example 6

[0123] In this embodiment, the method for preparing calcium magnesium carbon dioxide adsorbent based on calcium carbide slag and magnesium nitrate as raw materials is as follows:

[0124] Step (1): After drying the carbide slag and magnesium nitrate separately, disperse them together in deionized water according to the molar ratio of calcium to magnesium of 7:3. Add citric acid to the dispersion and then magnetically stir in an 80°C constant temperature water bath for 1 hour to allow the reaction to proceed. After the reaction is complete, a mixed dispersion B is obtained. The concentration of citric acid in the citric acid solution used is 40 wt.%, and the volume-to-mass ratio of citric acid solution to magnesium salt is 20 mL / g. Place the mixed dispersion B in a 120°C oven and heat for more than 10 hours to allow the mixed dispersion B to foam and dry (foaming will occur during the drying process), thus obtaining the carbide slag-magnesium composite.

[0125] Step (2): Grind the dried carbide slag-magnesium composite into powder, put it into a tube furnace heated to 850°C and calcine it in an air atmosphere at 850°C for 3 hours to obtain carbide slag calcium magnesium-based carbon dioxide adsorbent (denoted as CX73).

[0126] Example 7

[0127] The method for preparing calcium-magnesium-based carbon dioxide adsorbent from calcium carbide slag and magnesium nitrate in this embodiment differs from that in Example 6 only in that: in step (1), calcium carbide slag and magnesium nitrate are dissolved together in deionized water according to a molar ratio of calcium to magnesium of 8:2. The calcium-magnesium-based carbon dioxide adsorbent prepared in this embodiment is designated as CX82.

[0128] Example 8

[0129] The method for preparing calcium-magnesium carbon dioxide adsorbent based on calcium carbide slag and magnesium nitrate in this embodiment differs from that in Example 6 only in that: in step (1), calcium carbide slag and magnesium nitrate are dissolved together in deionized water according to a molar ratio of calcium to magnesium of 9:1. The calcium-magnesium carbon dioxide adsorbent prepared in this embodiment is designated as CX91.

[0130] The isothermal adsorption performance of the calcium magnesium-based carbon dioxide adsorbents prepared in Examples 6 to 8 were tested. During the test, CX73, CX82 and CX91 were placed in a mixed atmosphere of CO2 and N2, and isothermal adsorption was performed once each at temperatures of 550℃, 650℃ and 750℃, with an isothermal adsorption time of 120 min.

[0131] like Figures 25a-25c The results show the isothermal adsorption performance of CX73 under different temperature conditions. Figure 25a , Figure 25b , Figure 25c The test results are shown at 550℃, 650℃, and 750℃, respectively. As can be seen from the figure, at 550℃, the adsorption capacity of CX73 for carbon dioxide is 44.76 wt.%; at 650℃, it is 48.78 wt.%; and at 750℃, it is 52.46 wt.%.

[0132] like Figures 26a-26c The results show the isothermal adsorption performance of CX82 under different temperature conditions. Figure 26a , Figure 26b , Figure 26cThe test results are shown at 550℃, 650℃, and 750℃, respectively. As can be seen from the figure, at 550℃, the adsorption capacity of CX82 for carbon dioxide is 37.56 wt.%; at 650℃, it is 47.69 wt.%; and at 750℃, it is 49.66 wt.%.

[0133] like Figures 27a-27c The results show the isothermal adsorption performance of CX91 under different temperature conditions. Figure 27a , Figure 27b , Figure 27c The test results are shown at 550℃, 650℃, and 750℃, respectively. As can be seen from the figure, at 550℃, the adsorption capacity of CX91 for carbon dioxide is 25.37 wt.%; at 650℃, it is 43.94 wt.%; and at 750℃, it is 47.43 wt.%.

[0134] Comparing the adsorption capacities of CX73, CX82, and CX91 under the same isothermal adsorption temperature conditions, such as... Figures 28a-28c As shown, Figure 28a , Figure 28b , Figure 28c The results are compared at 550℃, 650℃, and 750℃. As shown in the figure, the adsorbent prepared by combustion synthesis of carbide slag, magnesium nitrate, and citric acid has a strong adsorption capacity. The adsorption capacity reaches its maximum when the molar ratio of calcium to magnesium is 7:3. This may be because the presence of MgO in the adsorbent promotes the increase in adsorption capacity.

[0135] like Figures 29a to 29c The figures show the adsorption capacity test results of CX73, CX82, and CX91 under different temperature conditions. As can be seen from the figures, the adsorbent prepared by combustion synthesis of magnesium nitrate from carbide slag follows the operating temperature range of calcium-based adsorbents: 550–750℃, with the optimal operating temperature being 750℃.

[0136] Based on the above results, it can be seen that using magnesium nitrate as the magnesium source and uniformly mixing calcium and magnesium ions in the carbide slag by adding citric acid increases the activity of the adsorbent. The optimal operating conditions for the adsorbent prepared by combustion synthesis of magnesium nitrate from carbide slag are 750℃ and a calcium to magnesium molar ratio of 7:3.

[0137] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for preparing calcium-magnesium-based carbon dioxide adsorbent from carbide slag, characterized in that, The steps include the following: Step (1): Prepare carbide slag-magnesium composite material using carbide slag and magnesium salt as raw materials; the magnesium salt is magnesium carbonate or magnesium nitrate. When the magnesium salt is magnesium carbonate, the preparation method of the carbide slag-magnesium composite is as follows: First, acetic acid solution is added to a mixture of carbide slag powder and magnesium carbonate to carry out the reaction. After the reaction is completed, a mixed dispersion A is obtained. Then, the water in the mixed dispersion A is evaporated to obtain the carbide slag-magnesium composite. When the magnesium salt is magnesium nitrate, the preparation method of the carbide slag-magnesium composite is as follows: First, citric acid solution is added to a mixture of carbide slag powder and magnesium nitrate to carry out the reaction. After the reaction is completed, a mixed dispersion B is obtained. Then, the water in the mixed dispersion B is evaporated to obtain the carbide slag-magnesium composite. Step (2): Calcine the calcium carbide slag-magnesium composite. After calcination, calcium carbide slag calcium magnesium-based carbon dioxide adsorbent is prepared. During calcination, the calcium carbide slag-magnesium composite is calcined by "entering the furnace at the specified temperature". After calcination, it is cooled to room temperature with the furnace.

2. The method for preparing calcium-magnesium-based carbon dioxide adsorbent from carbide slag according to claim 1, characterized in that, In step (1), the molar ratio of calcium to magnesium in the carbide slag-magnesium composite is 7-9:1-3; the particle size of the carbide slag powder is less than 74 μm; and the particle size of the magnesium salt is less than 74 μm. In step (2), during calcination, the carbide slag-magnesium composite is directly placed into a calcination furnace at 830-850℃ and kept warm for calcination for 2-3 hours.

3. The method for preparing calcium-magnesium-based carbon dioxide adsorbent from carbide slag according to claim 1, characterized in that, In step (1), when the magnesium salt is magnesium carbonate, the reaction temperature is 75-85℃ and the reaction time is 0.5-1h; in the mixed dispersion A, the molar ratio of calcium to magnesium is 7-9:1-3; the concentration of acetic acid in the acetic acid solution is 95wt.%-99.7wt.%; the volume-to-mass ratio of acetic acid solution to magnesium salt is 10-12 mL / g; the water in the mixed dispersion A is evaporated at 115-125℃. In step (2), the calcination temperature is 830-850℃ and the calcination time is 2-3h.

4. The method for preparing calcium-magnesium-based carbon dioxide adsorbent from carbide slag according to claim 1, characterized in that, In step (1), the magnesium salt is magnesium nitrate, the reaction temperature is 75-85℃, and the reaction time is 0.5-1h; in the mixed dispersion B, the molar ratio of calcium to magnesium is 7-9:1-3; the concentration of citric acid in the citric acid solution is 40wt.%-45wt.%; the volume-to-mass ratio of citric acid solution to magnesium salt is 20-25mL / g; the water in the mixed dispersion B is evaporated at 115-125℃. In step (2), the calcination temperature is 830-850℃ and the calcination time is 2-3h.

5. The method for preparing calcium-magnesium-based carbon dioxide adsorbent from carbide slag according to any one of claims 1-4, characterized in that, When the magnesium salt is magnesium carbonate, in step (1), the preparation method of the carbide slag-magnesium complex is as follows: first, add acetic acid solution to the mixture of carbide slag powder and magnesium salt and stir for 1 hour under constant temperature water bath at 80℃ to carry out the reaction. After the reaction is completed, a mixed dispersion A is obtained; then, the water in the mixed dispersion A is evaporated at 120℃ to obtain the carbide slag-magnesium complex; in the mixed dispersion A, the molar ratio of calcium to magnesium is 7:3; the concentration of acetic acid in the acetic acid solution is 99.7wt.%; the volume mass ratio of acetic acid solution to magnesium salt is 10mL / g; in step (2), during calcination, the carbide slag-magnesium complex is calcined by "entering the furnace at the specified temperature". After calcination, it is cooled to room temperature with the furnace. The calcination temperature is 850℃ and the calcination time is 3h. When the magnesium salt is magnesium nitrate, the preparation method of the carbide slag-magnesium complex in step (1) is as follows: First, citric acid solution was added to the mixture of carbide slag powder and magnesium salt and stirred for 1 hour under constant temperature water bath at 80℃ to carry out the reaction. After the reaction was completed, mixed dispersion B was obtained. Then, the water in mixed dispersion B was evaporated at 120℃ to obtain carbide slag-magnesium composite. In mixed dispersion B, the molar ratio of calcium to magnesium was 7:

3. The concentration of citric acid in the citric acid solution was 40 wt.%; the volume mass ratio of citric acid solution to magnesium salt was 20 mL / g. In step (2), during calcination, the carbide slag-magnesium composite was calcined by "entering the furnace at the specified temperature". After calcination, it was cooled to room temperature with the furnace. The calcination temperature was 850℃ and the calcination time was 3 hours.

6. The application of calcium-magnesium-based carbon dioxide adsorbent based on carbide slag, characterized in that, The calcium-magnesium-based carbon dioxide adsorbent prepared by the method of preparing calcium carbide slag calcium-magnesium-based carbon dioxide adsorbent as described in any one of claims 1 to 5 is used for isothermal adsorption of carbon dioxide, and the isothermal adsorption temperature is 550 to 750°C.

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