Calcium-based absorbent based on metal modification, preparation method of calcium-based absorbent and calcium circulation method carbon capture system

Abstract

The invention relates to the technical field of carbon capture, in particular to a calcium-based absorbent based on metal modification, a preparation method of the calcium-based absorbent and a calcium circulation method carbon capture system. The calcium circulation method carbon capture system comprises a capture device, a regeneration device, a cooling device and a steam turbine. The trapping device is used for carrying out carbon trapping on entering CO2 flue gas and separating a trapped product I to obtain decarbonized flue gas and a solid mixture I; the regeneration device is used for calcining the separated solid mixture I to obtain a product II containing the regenerated calcium-based absorbent, a gas mixture III and the deactivated calcium-based absorbent after carbon adsorption. And the product II is separated, so that the regenerated calcium-based absorbent can be recycled to the trapping device for reutilization. The cooling device is used for absorbing waste heat in the calcium circulation method carbon capture system and generating power through the steam turbine. By arranging the regeneration device, the calcium-based absorbent can be reused, and the utilization rate of the calcium-based absorbent is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon capture, and particularly relates to a metal-modified calcium-based absorbent and a preparation method thereof, and a calcium looping carbon capture system. Background Art

[0002] With the development of technology, the cement industry is also developing rapidly. The cement industry is a major emitter of carbon emissions. According to statistics, in 2020, the total cement output in China reached 2.38 billion tons, and the carbon emissions from the cement industry accounted for about 12% of the total national carbon emissions. The cement industry can reduce carbon emissions by adopting methods such as improving energy efficiency, increasing the proportion of alternative fuels, and reducing the clinker factor. However, a large amount of CO2 is generated during the firing process of cement clinker due to the decomposition of carbonates. This part of CO2 is generated by chemical reactions and accounts for about half of the total carbon emissions in the cement production process, and carbon emissions cannot be reduced by the above methods. Therefore, the deep decarbonization of the cement industry requires the assistance of carbon capture and utilization (CCUS) technology. At present, the carbon capture technology in industry generally adopts the organic amine absorption method and the oxy-fuel combustion technology. Among them, the organic amine absorption method is the most mature CCUS method currently applied. However, for the specific working conditions of the cement industry, the amine absorbent is easily deactivated by substances such as dust, SO2, NO x etc., and the cement industry currently does not have the experience of handling a large amount of liquid. Although the oxy-fuel combustion technology is a low-energy-consuming decarbonization method, if the oxy-fuel combustion technology is deployed, large-scale transformation of the existing cement kiln firing system is required.

[0003] Based on this, researchers have developed a new carbon capture method: calcium looping carbon capture. At the current stage, most of the research on calcium looping carbon capture is limited to the laboratory and pilot scale, and the research on the industrial application of calcium looping is rarely mentioned. And during the research process, researchers found that the main problems restricting the industrial application of calcium looping are that the existing calcium-based absorbents are prone to deactivation during carbon capture or sintering during use, resulting in the need to use a lot of calcium-based absorbents if calcium looping is used for carbon capture at the present stage. This leads to the consumption of a lot of raw materials in the whole calcium looping process, thus resulting in a high cost for the whole carbon capture process. In addition, the reaction temperature in the calcium looping carbon capture process is relatively high, so that more energy is consumed when carbon is captured by the existing calcium looping carbon capture device, resulting in more costs being invested in the whole carbon capture process. Summary of the Invention

[0004] In order to solve the technical problem that the calcium-based absorbent in the prior art is prone to deactivation or sintering during the capture of carbon in CO2 flue gas, resulting in a large consumption of calcium absorbent when capturing carbon through the existing calcium-looping carbon capture device, the present invention provides a metal-modified calcium-based absorbent and its preparation method, as well as a calcium-looping carbon capture system.

[0005] The present invention is implemented by the following technical solutions: A calcium-looping carbon capture system includes a capture device, a regeneration device, a cooling device, and a steam turbine. The capture device includes a carbonation furnace, a gas-solid separator, and a heat exchanger I; the CO2 flue gas to be treated enters the carbonation furnace after being heated by the heat exchanger I. The carbonation furnace is used to capture carbon from the incoming CO2 flue gas and transport the captured product I to the gas-solid separator for separation to obtain decarbonized flue gas and solid mixture I.

[0006] The regeneration device includes a bed material heater, a calcination furnace, a bed material cooler, and a cyclone I and a cyclone II with different wind speeds. The two ends of the bed material heater are respectively connected to the gas-solid separator and the calcination furnace, and the two ends of the cyclone I are respectively connected to the outlet of the calcination furnace and the inlet of the cyclone II. The separated solid mixture I enters the calcination furnace for calcination after being heated by the bed material heater, obtaining product II containing regenerated calcium-based absorbent, gas mixture III, and deactivated calcium-based absorbent after adsorbing carbon. The cyclone I is used to separate the incoming product II, so that the regenerated calcium-based absorbent and gas mixture III enter the cyclone II, and the deactivated calcium-based absorbent after adsorbing carbon precipitates to the bottom of the cyclone I. The cyclone II is used to perform gas-solid separation on the incoming regenerated calcium-based absorbent and gas mixture III, so that the gas mixture III enters the bed material heater and exchanges heat with the solid mixture I in the bed material heater. The regenerated calcium-based absorbent precipitates to the bottom of the cyclone II and is cooled by the bed material cooler and then recycled to the carbonation furnace for reuse.

[0007] The cooling device is respectively connected to the liquid inlet of the bed material cooler and the liquid inlet of the heat exchanger I. The condensed water generated by the cooling device exchanges heat with the solid mixture II passing through the bed material cooler and the CO2 flue gas passing through the heat exchanger I respectively and generates water vapor.

[0008] The steam turbine is respectively connected to the outlet of the bed material cooler and the outlet of the heat exchanger I. The steam turbine uses the water vapor generated by the heat exchange between the cooling device and the bed material cooler and between the cooling device and the heat exchanger I for power generation.

[0009] As a further improvement of the present invention, the wind speed of the cyclone I is greater than that of the cyclone II, and the wind force generated by the cyclone I on the product II is greater than the gravity of the regenerated calcium-based absorbent and less than the gravity of the deactivated calcium-based absorbent after adsorbing carbon, and the wind force generated by the cyclone II on the regenerated calcium-based absorbent is less than its own gravity.

[0010] As a further improvement of the present invention, the regeneration device further includes an oxygen generator connected to the calciner. The oxygen generator is used to separate oxygen from the air and transport the separated oxygen into the calciner.

[0011] As a further improvement of the present invention, the capture device further includes a second heat exchanger and a third heat exchanger. The two ends of the third heat exchanger are respectively connected to the first heat exchanger and the carbonization furnace. The third heat exchanger is used to transport the CO2 flue gas to be processed after being heated by the first heat exchanger into the carbonization furnace. The two ends of the second heat exchanger are respectively connected to the gas outlet of the gas-solid separator and the gas inlet of the third heat exchanger. The second heat exchanger is also connected to the cooling device. The decarbonized flue gas separated by the gas-solid separator exchanges heat with the water entering the second heat exchanger. The decarbonized flue gas after heat exchange enters the third heat exchanger and exchanges heat again with the CO2 flue gas to be processed in the third heat exchanger. The water after heat exchange in the second heat exchanger enters the bed material cooler and heats the regenerated calcium-based absorbent in the bed material cooler.

[0012] As a further improvement of the present invention, the cooling device includes a cooling tower, a condenser and a feed water tank. The two ends of the condenser are respectively connected to the cooling tower and the feed water tank. The cooling tower is used to provide water. The condenser is used to cool the water in the cooling tower and transport the cooled water to the feed water tank. The feed water tank is respectively connected to the first heat exchanger and the second heat exchanger and transports the condensed water into the first heat exchanger and the second heat exchanger respectively. The gas outlet of the steam turbine is connected to the condenser so that the water vapor used for steam power generation in the steam turbine is re-condensed into condensed water through the condenser.

[0013] As a further improvement of the present invention, the regeneration device further includes a fourth heat exchanger and a condensation device. The two ends of the fourth heat exchanger are respectively connected to the bed material heater and the condensation device. The water outlet of the condensation device is connected to the water inlet of the cooling tower. The fourth heat exchanger is also connected to the cooling device. The fourth heat exchanger is used to exchange heat between the gas mixture three cooled by the bed material heater and the condensed water of the cooling device, and the gas mixture three after heat exchange is transported into the condensation device. The condensation device is used to condense the water vapor in the gas mixture three and transport it back to the cooling tower.

[0014] As a further improvement of the present invention, the calcium loop carbon capture system further includes a first wind speed detector for detecting the wind speed in the first cyclone, a second wind speed detector for detecting the wind speed in the second cyclone and a controller. A first wind speed regulator is provided in the first cyclone, and a second wind speed regulator is provided in the second cyclone. The controller is electrically connected to the first wind speed detector, the second wind speed detector, the first wind speed regulator and the second wind speed regulator respectively.

[0015] The controller obtains the wind speed data of Cyclone 1 through Wind Speed Detector 1 and makes the following comparison with the set threshold range 1: If the wind speed detected by Wind Speed Detector 1 is lower than the set threshold range 1, the controller controls Wind Speed Regulator 1 to increase the wind speed of Cyclone 1. If the wind speed detected by Wind Speed Detector 1 is greater than the set threshold range 1, the controller controls Wind Speed Regulator 1 to decrease the wind speed of Cyclone 1.

[0016] The controller obtains the wind speed data of Cyclone 2 through Wind Speed Detector 2 and makes the following comparison with the set threshold range 2: If the wind speed detected by Wind Speed Detector 2 is lower than the set threshold range 2, the controller controls Wind Speed Regulator 2 to increase the wind speed of Cyclone 2. If the wind speed detected by Wind Speed Detector 2 is greater than the set threshold range 2, the controller controls Wind Speed Regulator 2 to decrease the wind speed of Cyclone 2.

[0017] As a further improvement of the present invention, the calcium looping carbon capture system further includes Concentration Detector 1 for detecting the CO2 concentration in the carbonation furnace and Concentration Detector 2 for detecting the CO2 concentration in the calcination furnace. A valve 1 is provided between the carbonation furnace and the gas-solid separator, and a valve 2 is provided between the calcination furnace and Cyclone 1. The controller is electrically connected to Concentration Detector 1, Concentration Detector 2, valve 1, and valve 2 respectively.

[0018] If the CO2 concentration detected by Concentration Detector 1 is lower than the set threshold 1, the controller opens valve 1; otherwise, it does not open valve 1. If the CO2 concentration detected by Concentration Detector 1 is higher than the set threshold 2, the controller opens valve 2; otherwise, it does not open valve 2.

[0019] The present invention further includes a metal-modified calcium-based absorbent, which uses the calcium looping carbon capture system as described above to capture CO2 from flue gas; the calcium-based absorbent includes one or at least two mixtures of ZnCa(OH)2, TiCa(OH)2, and MgCa(OH)2.

[0020] The present invention further includes a preparation method of a metal-modified calcium-based absorbent, which includes the following steps: (1) Heat a certain amount of dolomite powder to 950 °C and calcine for 1 h to obtain a CaO precursor. (2) Weigh the CaO precursor and metal oxide in a mass ratio of 92:11 and mix them in an aqueous alcohol solution to obtain Mixture 4. The metal oxide includes one of titanium oxide, zinc oxide, and magnesium oxide. After ultrasonicating Mixture 4 for 30 min, heat it at 300 °C to obtain Solid Particle 1. (3) Dry Solid Particle 1 at 900 °C to obtain the metal-modified calcium-based absorbent.

[0021] The technical solution provided by the present invention has the following beneficial effects:

[0022] (1) The present invention provides a calcium looping carbon capture system. By setting up a regeneration device, it can regenerate the calcium-based absorbent after multiple absorption and desorption processes, enabling the regenerated calcium-based absorbent to be reused. Thus, the reuse of the calcium-based absorbent can be achieved, reducing the demand for calcium-based absorbent during the carbon capture process and thereby reducing the cost of carbon capture. Meanwhile, by setting up a cooling device and a steam turbine, the cooling device can recover the heat generated by the reaction of solid particles in the carbonation furnace and the calcination furnace, the heat of the industrial flue gas itself, and the heat contained in the gases discharged from the carbonation furnace and the calcination furnace through cooling water and use it for preheating power generation by the steam turbine. Thus, the waste heat in the calcium looping carbon capture system is utilized to the maximum extent, reducing the energy consumption of the calcium looping carbon capture system.

[0023] (2) The calcium looping carbon capture system provided by the present invention sets different types of heat exchangers at different positions in the system. Through the heat exchangers, the heat loss generated by the reaction temperature difference in the calcium looping carbon capture system can be absorbed, thereby achieving the maximum utilization of the waste heat in the calcium looping carbon capture system and reducing energy consumption.

[0024] (3) The present invention also provides a calcium-based absorbent modified with metal, which has the characteristics of high absorption rate, strong stability, low cost, etc. And the calcium-based absorbent modified with titanium metal has a mass fraction decrease of about 5% after multiple cycles of absorption and desorption. Brief Description of the Drawings

[0025] Figure 1 It is a flow chart of a calcium looping carbon capture system provided in Embodiment 1 of the present invention.

[0026] Figure 2 It is a flow chart when the capture device and the cooling device in the calcium looping carbon capture system provided in Embodiment 1 of the present invention are connected.

[0027] Figure 3 It is a flow chart when the regeneration device and the cooling device in the calcium looping carbon capture system provided in Embodiment 1 of the present invention are connected.

[0028] Figure 4 It is a state diagram of the mass of the calcium-based absorbent prepared in the comparative example of the present invention changing with temperature.

[0029] Figure 5 It is a state diagram of the mass of the ZnCa(OH)2 calcium-based absorbent prepared in Embodiment 5 of the present invention changing with temperature.

[0030] Figure 6 It is a state diagram of the mass of the TiCa(OH)2 calcium-based absorbent prepared in Embodiment 6 of the present invention changing with temperature.

[0031] Figure 7 This is the state diagram showing the variation of the mass of the MgCa(OH)₂ calcium-based absorbent prepared in Example 4 of the present invention with temperature.

[0032] In the figure, the markings are as follows: 11, carbonization furnace; 12, gas-solid separator; 13, heat exchanger I; 14, heat exchanger II; 15, heat exchanger III; 16, compression system; 21, bed material heater; 22, calciner; 23, bed material cooler; 24, cyclone I; 25, cyclone II; 26, heat exchanger IV; 27, condensation device; 28, oxygen generator; 31, cooling tower; 32, condenser; 33, feed water tank; 4, steam turbine. Detailed implementation manners

[0033] Next, in combination with the detailed implementation manners, the present invention will be further described. It should be noted that on the premise of no conflict, the following-described embodiments or technical features can be arbitrarily combined with each other to form new embodiments.

[0034] In the description of the present invention, it should be noted that for the orientation terms, such as the terms "center", "transverse", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., the indicated orientation and position relationships are based on the orientation or position relationships shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and should not be construed as limiting the specific protection scope of the present invention. The terms "first", "second", etc. in the description and claims of the present invention are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. The terms "comprise" and "have" in the description and claims of the present invention and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0035] Example 1

[0036] This example provides a calcium looping carbon capture system. Please refer to Figures 1 to 3, which includes a capture device, a regeneration device, a cooling device, and a steam turbine 4. The capture device is used to capture carbon from the CO2 flue gas to be treated. The regeneration device is used to regenerate the metal-modified calcium-based absorbent used in the capture device and transport the regenerated calcium-based absorbent back to the capture device for reuse. The cooling device is used to provide condensed water to the parts that need to be cooled in the capture device and the regeneration device. The steam turbine 4 can generate electricity using the heat after the condensed water is cooled, thereby realizing the utilization of the energy consumption in the entire cyclic carbon capture system and improving the utilization rate of energy consumption.

[0037] Please refer to Figure 1 and Figure 2 , the capture device includes a carbonization furnace 11, a gas-solid separator 12, a first heat exchanger 13, a compression system 16, a second heat exchanger 14, and a third heat exchanger 15. The inlet of the first heat exchanger 13 is connected to the inlet of the CO2 flue gas. The outlet of the first heat exchanger 13 is connected to the compression system 16. The outlet of the compression system 16 is connected to the first inlet of the third heat exchanger 15. The first outlet of the third heat exchanger 15 is connected to the inlet of the carbonization furnace 11. The outlet of the carbonization furnace 11 is connected to the gas-solid separator 12. The outlet of the gas-solid separator 12 is connected to the second heat exchanger 14. The outlet of the second heat exchanger 14 is connected to the second inlet of the third heat exchanger 15. In this embodiment, the compression system 16 can be a compressor. During the capture process, the CO2 flue gas to be treated first passes through the first heat exchanger 13 for temperature reduction and then is compressed by the compressor and enters the third heat exchanger 15, and then enters the carbonization furnace 11. The calcium-based absorbent in the carbonization furnace 11 can capture carbon from the incoming CO2 flue gas and transport the first captured product to the gas-solid separator 12 for separation, thereby obtaining decarbonized flue gas and the first solid mixture. In this embodiment, the gas-solid separator 12 can be a gravity gas-solid separator 12. It can use the momentum and gravity of the gas flow to separate the solid particles in the gas. It can be understood that the main reaction occurring in the carbonization furnace 11 is CaO + CO2 = CaCO3. Therefore, the first solid mixture is the calcium-based absorbent deactivated after adsorbing carbon, so its main component is calcium carbonate. And the adsorption effect of calcium carbonate on CO2 in the carbonization furnace 11 can be ignored. Therefore, the calcium-based absorbent deactivated after adsorbing carbon needs to be transported to the regeneration device. Under the calcination of the regeneration device, calcium carbonate can be reconverted into CaO, and then the calcined calcium oxide is transported back to the carbonization furnace 11. Thus, the reuse of the calcium-based absorbent can be realized, thereby reducing the demand for the calcium-based absorbent in the carbon capture process and realizing the reduction of the carbon capture cost.

[0038] It is understandable that in this solution, the optimal temperature of the carbonization furnace 11 is also studied. By setting a series of different temperatures for the carbonization furnace 11 and keeping other parameters unchanged for carbon capture, the following results can be obtained: when the temperature in the carbonization furnace 11 is about 650 °C, the carbon capture efficiency of the calcium-based absorbent in the carbonization furnace 11 is the highest. Therefore, the temperature in the carbonization furnace 11 in this embodiment can be set to 650 °C. The wind speed in the carbonization furnace 11 can be 17-20 m / s.

[0039] The first heat exchanger 13 and the second heat exchanger 14 are respectively connected to the cooling device so that the cooling device can provide condensed water for the first heat exchanger 13 and the second heat exchanger 14. For the first heat exchanger 13, it can be a liquid-phase heat exchanger. Since the temperature in the cement industry is relatively high, the initial temperature of the CO2 flue gas to be treated is also relatively high. By exchanging heat between the CO2 flue gas to be treated and the first heat exchanger 13, the water temperature in the first heat exchanger 13 rises to become steam, and the outlet of the first heat exchanger 13 is connected to the steam turbine 4. The steam is used to drive the steam turbine 4 to generate electricity, so that in this solution, the heat in the CO2 flue gas to be treated can be utilized by setting the first heat exchanger 13 and the condensed water, and electricity can be generated through the steam turbine 4. Thus, the thermal energy in the calcium-looping carbon capture system is effectively utilized. For the second heat exchanger 14, it can be a liquid-phase heat exchanger. During its application, it is also connected to the cooling device, so that the condensed water in the cooling device can exchange heat with the decarbonized flue gas entering the second heat exchanger 14 in the second heat exchanger 14, causing the temperature of the condensed water in the second heat exchanger 14 to rise and become steam. The steam can be transported to the steam turbine 4, and the steam turbine 4 can use the steam in the second heat exchanger 14 to generate electricity. Through the above description, it can be seen that in this embodiment, by setting the first heat exchanger 13 and the second heat exchanger 14, the waste heat in the carbon capture stage can be effectively utilized, avoiding waste of energy.

[0040] For the heat exchanger III 15 in this embodiment, it can be a gas-phase heat exchanger. During design, one end of it is connected to the compressor, and the other end is connected to the carbonization furnace 11. Moreover, the second air inlet in the heat exchanger III 15 is also connected to the outlet of the heat exchanger II 14, so that the decarbonized flue gas can also exchange heat with the continuously introduced CO2 flue gas to be treated in the heat exchanger III 15. The principle of its heat exchange is as follows: Since the temperature in the carbonization furnace 11 is set at 650 °C, the temperature of the decarbonized flue gas treated by the carbonization furnace 11 is relatively high. After decarbonization treatment, the decarbonized flue gas needs to be discharged. If it is directly discharged, this part of the heat will be directly released into the environment, thus exacerbating the greenhouse effect of the environment. In this embodiment, by setting the heat exchanger III 15, which exchanges heat between the decarbonized flue gas and the CO2 flue gas to be treated, it can not only cool down the decarbonized flue gas, but also use this part of the temperature to heat the CO2 flue gas to be treated, so that the temperature of the decarbonized flue gas discharged into the atmosphere is relatively low while the temperature of the CO2 flue gas to be treated entering the carbonization furnace 11 is relatively high. This operation can not only avoid the situation where the heat in the calcium-looping carbon capture system in this solution is directly discharged into the atmospheric environment, thus exacerbating the greenhouse effect, but also further increase the temperature of the CO2 flue gas to be treated entering the carbonization furnace 11, so that the temperature of the CO2 flue gas to be treated entering the carbonization furnace 11 is relatively high, which will also reduce the energy consumption in the carbonization furnace 11. In addition, in this embodiment, by respectively arranging the heat exchanger I 13, the compressor and the heat exchanger III 15 at the front end of the carbonization furnace 11, first, the heat exchanger I 13 can cool down the CO2 flue gas to be treated. This operation can not only utilize the heat carried by the CO2 flue gas to be treated itself, but also facilitate the subsequent compression of the CO2 flue gas to be treated by the compressor by cooling down the CO2 flue gas to be treated, reducing the energy consumption during the compression process. Furthermore, by setting the heat exchanger III 15, it can use the heat carried by the decarbonized flue gas to reheat the compressed CO2 flue gas to be treated, so that the temperature of the CO2 flue gas to be treated entering the carbonization furnace 11 is relatively high, thus achieving the purpose of reducing the energy consumption of the carbonization furnace 11. It can be seen that in this embodiment, through this series of settings, not only can some of the heat generated during the capture process of the CO2 flue gas to be treated be used to generate electricity by the steam turbine 4; the other part can be used to heat the CO2 flue gas to be treated, so that the temperature of the CO2 flue gas to be treated entering the carbonization furnace 11 is relatively high, thus achieving the purpose of reducing the energy consumption in the carbonization furnace 11. In addition, in this embodiment, by setting different types of heat exchangers at different positions in the calcium-looping carbon capture system, the heat exchangers can absorb the heat loss generated due to the reaction temperature difference, thereby achieving the maximum reduction of energy consumption.

[0041] Please refer to Figure 1 and Figure 3, the regeneration device includes a bed material heater 21, a calciner 22, a bed material cooler 23, a first cyclone 24, a second cyclone 25, an oxygen generator 28, a fourth heat exchanger 26, and a condensation device 27. Both ends of the bed material heater 21 are respectively connected to the gas-solid separator 12 and the calciner 22, and the separated solid mixture 1 in the gas-solid separator 12 can enter the bed material heater 21 from the gas-solid separator 12. The bed material heater 21 can heat the solid mixture 1 and send the heated solid mixture 1 to the calciner 22, and the calciner 22 can calcine the solid mixture 1. In this embodiment, the calcination temperature of the calciner 22 can be about 950 °C, and the calcination time can be 1 h, so that the calcium carbonate entering the calciner 22 can be decomposed into calcium oxide and carbon dioxide at high temperature. It can be understood that the fuel in the calciner 22 can be coal. And during calcination, the oxygen in the air can be separated by the oxygen generator 28 and the separated oxygen can be transported into the calciner 22. By adding oxygen into the calciner 22, the calcination effect of the calciner 22 can be improved, and the conversion rate of calcium carbonate in the calciner 22 into calcium oxide can be accelerated. In this embodiment, the concentration of the oxygen supplied to the calciner 22 needs to be maintained at about 95%. And in the actual application process, if the amount of the calcium-based absorbent needs to be added, calcium carbonate can be added into the calciner 22. The calcium carbonate entering the calciner 22 can be decomposed into calcium oxide under high-temperature calcination, and the obtained calcium oxide can be transported back to the carbonation furnace 11, thereby realizing the timely replenishment of the calcium-based absorbent in the carbonation furnace 11. In addition, a calcium carbonate addition port is also provided in the calciner 22 of this embodiment. By setting the calcium carbonate addition port, it can be timely added to the calcium loop carbon capture system when the calcium-based absorbent needs to be replenished in the calcium loop carbon capture system. In this embodiment, the amount of calcium carbonate added into the calciner 22 can be 7 kg per second.

[0042] Please refer to Figure 3, both ends of the first cyclone 24 are respectively connected to the discharge port of the calciner 22 and the feed port of the second cyclone 25. The separated first solid mixture enters the calciner 22 after being heated by the bed material heater 21 and is calcined to obtain a second product containing the regenerated calcium-based absorbent, the third gas mixture, and the calcium-based absorbent deactivated after adsorbing carbon. Among them, the main components of the third gas mixture are water vapor and carbon dioxide. The regenerated calcium-based absorbent can be calcium oxide, and the calcium-based absorbent deactivated after adsorbing carbon can be calcium carbonate. The first cyclone 24 is used to separate the incoming second product so that the regenerated calcium-based absorbent and the third gas mixture enter the second cyclone 25, and the deactivated calcium-based absorbent precipitates to the bottom of the first cyclone 24. The second cyclone 25 is used for gas-solid separation of the incoming regenerated calcium-based absorbent and the third gas mixture so that the third gas mixture enters the bed material heater 21 and exchanges heat with the first solid mixture in the bed material heater 21. The regenerated calcium-based absorbent precipitates to the bottom of the second cyclone 25 and is cooled by the bed cooler 23 and then recycled to the carbonization furnace 11 for reuse. Since there is a difference in the weights of calcium carbonate and calcium oxide, in actual application, the wind speeds of the first cyclone 24 and the second cyclone 25 can be adjusted to different values. During the adjustment process, it is necessary to satisfy that the wind speed of the first cyclone 24 is greater than the wind speed of the second cyclone 25, and the wind speed of the first cyclone 24 itself needs to satisfy that the wind force generated on the regenerated calcium-based absorbent is greater than the gravity of the regenerated calcium-based absorbent itself and less than the gravity of the calcium-based absorbent adsorbed with carbon. Through this setting, the third gas mixture and the regenerated calcium-based absorbent in the second product after entering the first cyclone 24 can be separated from the calcium-based absorbent deactivated after adsorbing carbon. Subsequently, the third gas mixture and the regenerated calcium-based absorbent can enter the second cyclone 25. The wind speed in the second cyclone 25 needs to satisfy that the wind force generated on the regenerated calcium-based absorbent is less than the gravity of the regenerated calcium-based absorbent itself, and the wind speed needs to enable the third gas mixture to enter the bed material heater 21 through the air outlet of the second cyclone 25. Through this setting, the regenerated calcium absorbent and the third gas mixture entering the second cyclone 25 can be separated. Among them, the regenerated calcium-based absorbent will sink to the bottom of the second cyclone 25 under the action of gravity, and the third gas mixture will enter the bed material heater 21 from the air outlet of the second cyclone 25. Since the third gas mixture is separated from the calciner 22, the temperature of the third gas mixture is relatively high. In this embodiment, under the cyclic use of the calcium loop carbon capture system, through the third gas mixture, heat exchange can be carried out with the first solid mixture separated from the gas-solid separator 12 of the carbonization furnace 11 in the bed material heater 21, so that the first solid mixture can utilize the heat generated in the calciner 22 and increase the temperature of the first solid mixture entering the calciner 22, thereby reducing the energy consumption of the calciner 22.

[0043] In this embodiment, by providing a calciner 22, a first cyclone 24, a second cyclone 25, and a bed material heater 21, not only can the calcium-based absorbent deactivated after adsorbing carbon in the carbonization furnace 11 be calcined at a high temperature so that it can decompose into a regenerated calcium-based absorbent, and under the action of the first cyclone 24 and the second cyclone 25, it can be recycled back to the carbonization furnace 11, thereby realizing the recycling of the calcium-based absorbent to reduce the demand for the calcium-based absorbent in the calcium looping process, and ultimately reducing the cost of carbon capture by the calcium looping process. In the actual application process, the wind speed ranges of both the first cyclone 24 and the second cyclone 25 are between 3 m / s and 4 m / s, and the wind speed of the first cyclone 24 is always greater than that of the second cyclone 25. In this solution, by providing the first cyclone 24 and the second cyclone 25 and having different wind speed magnitudes for the first cyclone 24 and the second cyclone 25, when separating the product two in the calciner 22, it is possible to gradually separate various components in the product two. Using different wind speeds can effectively separate the regenerated calcium-based absorbent and the calcium-based absorbent after adsorbing carbon, so that the separated regenerated calcium-based absorbent can be recycled back to the carbonization furnace 11 for reuse, and at the same time, the calcium-based absorbent after carbon adsorption can be discharged from the bottom of the first cyclone 24 to prevent it from entering the carbonization furnace 11 again. Thus, the calcium-based absorbent (i.e., the regenerated calcium-based absorbent) that can absorb carbon again after calcination in the calciner 22 and the calcium-based absorbent deactivated due to calcination (i.e., the calcium-based absorbent that can no longer absorb carbon dioxide) are separated, thereby improving the carbon capture efficiency of the carbonization furnace 11. It can be understood that one end of the bed material cooler 23 is connected to the carbonization furnace 11, and the other end of the bed material cooler 23 is connected to the second cyclone 25. The bed material cooler 23 is also connected to a cooling device. Through this connection method, the condensed water in the bed material cooler 23 can cool the regenerated calcium-based absorbent entering the bed material cooler 23. This ensures that the temperature of the regenerated calcium-based absorbent entering the carbonization furnace 11 is not too high, so that the working temperature in the carbonization furnace 11 can be kept stable, thereby improving the carbon capture efficiency in the carbonization furnace 11.

[0044] One end of the fourth heat exchanger 26 is connected to the outlet of the bed material heater 21, and the other end of the fourth heat exchanger 26 is connected to the condensation device 27. The water outlet of the condensation device 27 is connected to the cooling device, and the gas outlet of the condensation device 27 is connected to the purification device. The fourth heat exchanger 26 is also connected to the cooling device so that the gas mixture III cooled by the bed material heater 21 can exchange heat with the condensed water in the fourth heat exchanger 26, thereby cooling the gas mixture III. The cooled gas mixture III can enter the condensation device 27, and the condensation device 27 can condense the water vapor in the gas mixture III and transport the condensed water back to the cooling device, thereby realizing the recycling of water. Moreover, the high-concentration CO2 entering the condensation device 27 can be transported to the purification device for purification.

[0045] It can be understood that when the calciner 22 is calcining, some water vapor can also be added into the calciner 22 through the cooling device. Adding water vapor can, on the one hand, increase the temperature of the calciner 22. The reason is that by adding water vapor into the calciner 22, the entering water vapor will mix with the fuel to form a mixture similar to gas fuel. This mixture can make the fuel in the calciner 22 burn more fully, thereby increasing the temperature in the calciner 22 and making the decomposition of calcium carbonate more complete. On the other hand, water vapor can also help control the pressure in the calciner 22. The reason is that during the calcination of calcium carbonate, a large amount of carbon dioxide is generated during the decomposition process of calcium carbonate, which increases the pressure in the calciner 22. If the pressure is too high, it will affect the decomposition rate of calcium carbonate. Adding water vapor can reduce the temperature in the calciner 22 by diluting the concentration of carbon dioxide, thereby increasing the decomposition rate of calcium carbonate in the calciner 22.

[0046] The temperature of the solid mixture I at the outlet of the bed material heater 21 is 700 °C, and the temperature of the gas at the gas outlet of the bed material heater 21 is 825 °C. Among them, the reaction temperature of the calciner 22 is 950 °C, and the reaction temperature of the carbonization furnace is 650 °C. The heat loss caused by this part of the temperature difference can be recovered by means of gas-solid heat exchange. That is, the temperature of the solid coming out of the calciner 22 is 950 °C, and after gas-solid heat exchange, its temperature can be reduced to about 700 °C, and then when it re-enters the carbonization furnace, the temperature of the solid entering the carbonization furnace can meet the requirement of 650 °C.

[0047] The cooling device includes a cooling tower 31, a condenser 32, and a feed water tank 33. The two ends of the condenser 32 are respectively connected to the cooling tower 31 and the feed water tank 33. The cooling tower 31 is used to provide water, and the condenser 32 is used to cool the water in the cooling tower 31 and convey the cooled water to the feed water tank 33. The feed water tank 33 is respectively connected to the first heat exchanger 13 and the second heat exchanger 14, and conveys the condensed water into the first heat exchanger 13 and the second heat exchanger 14 respectively. The air outlet of the steam turbine 4 is connected to the condenser 32, so that the water vapor after steam power generation in the steam turbine 4 is re-condensed into condensed water through the condenser 32. In addition, the steam turbine 4 can also be respectively connected to the air outlet of the first heat exchanger 13 and the air outlet of the bed material cooler 23, so that the steam turbine 4 can generate electricity by using the water vapor generated after heat exchange between the cooling device and the bed material cooler 23 and between the cooling device and the first heat exchanger 13. The condensation device 27 is connected to the cooling tower 31, so that the condensed water in the condensation device 27 can be recycled to the cooling tower 31. Through the above description, it can be seen that in this embodiment, by setting the cooling device, the first heat exchanger 13, the second heat exchanger 14, the fourth heat exchanger 26, and the bed material cooler 23, the heat of the flue gas in the cement industry, the heat generated by the reaction of solid particles in the carbonization furnace 11 and the calcination furnace 22, the heat of the gas discharged from the carbonization furnace 11, and the heat of the gas discharged from the calcination furnace 22 can be recovered by the condensed water and used for preheating power generation by the steam turbine 4, thereby realizing the maximum utilization of the waste heat in the calcium looping carbon capture system. In addition, by setting the cooling device, this circulating water path can also inject superheated steam into the calcination furnace 22. By injecting superheated steam into the calcination furnace 22, the inactivation probability of the calcium-based absorbent for cyclic absorption and desorption can be reduced.

[0048] It can be understood that by setting the steam turbine 4, the present invention can recover the waste energy in the calcium looping carbon capture system based on the cooling device, convert the recovered heat energy into electric energy, realize the recovery and reuse of the waste energy, and thus achieve the purpose of reducing energy consumption.

[0049] The steam turbine 4 can be a high-pressure steam turbine 4, with an operating pressure of 130 kPa and a temperature of 550 °C.

[0050] In this embodiment, the calcium looping carbon capture system may further include a first wind speed detector for detecting the wind speed in the first cyclone 24, a second wind speed detector for detecting the wind speed in the second cyclone 25, a first concentration detector for detecting the CO2 concentration in the carbonation furnace 11, a second concentration detector for detecting the CO2 concentration in the calcination furnace 22, and a controller. A first wind speed regulator is provided in the first cyclone 24, and a second wind speed regulator is provided in the second cyclone 25. A first valve is provided between the carbonation furnace 11 and the gas-solid separator 12, and a second valve is provided between the calcination furnace 22 and the first cyclone 24. The controller is electrically connected to the first wind speed detector, the second wind speed detector, the first wind speed regulator, the second wind speed regulator, the first valve, and the second valve respectively.

[0051] Among them, the controller obtains the wind speed data of the first cyclone 24 through the first wind speed detector and makes the following comparison with the set first threshold range: (1.1) If the wind speed detected by the first wind speed detector is lower than the set first threshold range, the controller controls the first wind speed regulator to increase the wind speed in the first cyclone 24. (1.2) If the wind speed detected by the first wind speed detector is greater than the set first threshold range, the controller controls the first wind speed regulator to decrease the wind speed in the first cyclone 24.

[0052] The controller obtains the wind speed data of the second cyclone 25 through the second wind speed detector and makes the following comparison with the set second threshold range: (2.1) If the wind speed detected by the second wind speed detector is lower than the set second threshold range, the controller controls the second wind speed regulator to increase the wind speed in the second cyclone 25. (2.2) If the wind speed detected by the second wind speed detector is greater than the set second threshold range, the controller controls the second wind speed regulator to decrease the wind speed in the second cyclone 25.

[0053] Through the above operations, the wind speeds in the first cyclone 24 and the second cyclone 25 can be effectively and reasonably controlled, so that the first cyclone 24 and the second cyclone 25 can effectively separate the calcium-based absorbent deactivated after adsorbing carbon, the regenerated calcium-based absorbent, and the gas mixture three. Through this setting, it can effectively ensure that the regenerated calcium-based absorbent can be recycled back to the carbonation furnace 11 for re-adsorption. At the same time, the high-concentration carbon dioxide generated in the calcination furnace 22 can enter the purification device for purification and then utilization, and the water vapor can also be condensed in the condensation device 27 and then refluxed back to the cooling tower 31 for re-utilization, thereby realizing the full utilization of various substances in the calcium looping method.

[0054] In this embodiment, the controller can also control the opening or closing of Valve 1 and Valve 2. The specific operations are as follows: (3.1) If the CO2 concentration detected by Concentration Detector 1 is lower than the first set threshold, the controller opens Valve 1; otherwise, it does not open Valve 1. (3.2) If the CO2 concentration detected by Concentration Detector 1 is higher than the second set threshold, the controller opens Valve 2; otherwise, it does not open Valve 2.

[0055] Embodiment 2

[0056] This embodiment also provides a metal-modified calcium-based absorbent, which can use the calcium looping carbon capture system shown in Embodiment 1 to capture CO2 from flue gas. The calcium-based absorbent includes one or at least two mixtures of ZnCa(OH)2, TiCa(OH)2, and MgCa(OH)2.

[0057] Embodiment 3

[0058] This embodiment provides a preparation method of the metal-modified calcium-based absorbent in Embodiment 2 on the basis of Embodiment 2, which includes the following steps: heating a certain amount of dolomite powder to 950 °C and calcining for 1 h to obtain a CaO precursor.

[0059] S2: Weigh the CaO precursor and metal oxide with a mass ratio of 92:11 and mix them in an alcohol aqueous solution to obtain Mixture 4; the metal oxide includes one of titanium oxide, zinc oxide, and magnesium oxide; ultrasonicate Mixture 4 for 30 min and then heat it at 300 °C to obtain Solid Particle 1.

[0060] S3: Dry Solid Particle 1 at 900 °C to obtain the metal-modified calcium-based absorbent.

[0061] Among them, the volume ratio of alcohol to water in the alcohol aqueous solution in step S1 is 4:1.

[0062] Embodiment 4

[0063] This embodiment provides a preparation method of the specific metal-modified calcium-based absorbent MgCa(OH)2 in Embodiment 2 on the basis of Embodiments 2 and 3, which includes the following steps:

[0064] (4.1) First, take an appropriate amount of dolomite powder and place it in a crucible, calcine it at 950 °C for 1 h, and the heating rate is 10 °C / min to obtain a precursor with the main component of CaO.

[0065] (4.2) Weigh 1.84 g of calcined CaO, and another 0.22 g of MgO (the molar ratio of CaO to MgO is about 6). Mix them in an alcohol solution with a volume ratio of alcohol to water of 1:4, that is, 10 mL of water and 40 mL of alcohol. After ultrasonic treatment for 30 min until the solid particles are dissolved, put them into a muffle furnace and heat at 300 °C for 30 min to remove water.

[0066] (4.3) Put the dried solid particles into a muffle furnace and react at 900 °C for 30 min to obtain the metal-modified calcium-based absorbent MgCa(OH)2.

[0067] Example 5

[0068] This example provides a preparation method of a metal-modified calcium-based absorbent ZnCa(OH)2, which includes the following steps:

[0069] (5.1) First, take an appropriate amount of dolomite powder and place it in a crucible. Calcinate it at 950 °C for 1 h with a heating rate of 10 °C / min to obtain a precursor mainly composed of CaO.

[0070] (4.2) Weigh 1.84 g of calcined CaO, and another 0.6 g of ZnO (the molar ratio of CaO to ZnO is about 6). Mix them in an alcohol solution with a volume ratio of alcohol to water of 1:4, that is, 10 mL of water and 40 mL of alcohol. After ultrasonic treatment for 30 min until the solid particles are dissolved, put them into a muffle furnace and heat at 300 °C for 30 min to remove water.

[0071] (4.3) Put the dried solid particles into a muffle furnace and react at 900 °C for 30 min to obtain the metal-modified calcium-based absorbent ZnCa(OH)2.

[0072] Example 6

[0073] This example provides a preparation method of a metal-modified calcium-based absorbent TiCa(OH)2, which includes the following steps:

[0074] (5.1) First, take an appropriate amount of dolomite powder and place it in a crucible. Calcinate it at 950 °C for 1 h with a heating rate of 10 °C / min to obtain a precursor mainly composed of CaO.

[0075] (4.2) Weigh 1.84 g of calcined CaO, and another 0.4 g of TiO (the molar ratio of CaO to TiO is about 6). Mix them in an alcohol solution with a volume ratio of alcohol to water of 1:4, that is, 10 mL of water and 40 mL of alcohol. After ultrasonic treatment for 30 min until the solid particles are dissolved, put them into a muffle furnace and heat at 300 °C for 30 min to remove water.

[0076] (4.3) Put the dried solid particles into a muffle furnace and react at 900 °C for 30 min to obtain the metal-modified calcium-based absorbent TiCa(OH)2.

[0077] Control example

[0078] This example is a control group. The control group prepares Ca(OH)2 by a common method in the prior art, and uses the prepared Ca(OH)2 as the calcium-based absorbent in the control example.

[0079] Performance test

[0080] Weigh 30 mg of ZnCa(OH)2 prepared in Example 3, 30 mg of ZnCa(OH)2 prepared in Example 4, 30 mg of TiCa(OH)2 prepared in Example 5, and 30 mg of Ca(OH)2 prepared in the control example respectively. Place the four different calcium-based absorbents in four different crucibles. Then place the 4 crucibles into a thermogravimetric analyzer respectively, and react under the atmosphere of CO2 and N2, and record the change of the weight of the four different calcium-based absorbents with temperature, and the results are as Figures 4 to 7 shown.

[0081] Among them, Figure 4 is the state diagram of the mass change of the calcium-based absorbent prepared in the comparative example with temperature. Through Figure 4 it can be known that the mass fraction of the calcium-based absorbent prepared in the comparative example after re-absorbing CO2 after the initial regeneration can reach 140%, and after multiple cycles of absorption and desorption, its mass fraction decays to 110%, indicating that the calcium-based absorbent prepared in the comparative example is deactivated to varying degrees after multiple cycles of absorption and desorption. Figure 5 is the state diagram of the mass change of the ZnCa(OH)2 calcium-based absorbent prepared in Example 3 with temperature. Through the analysis of Figure 5 it can be known that the mass fraction of ZnCa(OH)2 prepared in Example 3 decays from 120% in the first regeneration to 105% after multiple cycles of absorption and desorption, indicating that the anti-sintering performance of the calcium-based absorbent modified by Zn has been improved, and the stability has also been improved, but the absorption efficiency and absorption rate of CO2 have both decreased. Figure 6 is the state diagram of the mass change of the TiCa(OH)2 calcium-based absorbent prepared in Example 5 with temperature. Through the analysis of Figure 6 it can be known that the mass fraction of the TiCa(OH)2 calcium-based absorbent can reach 130% after re-absorbing CO2 after the initial regeneration, and decays to 125% after multiple cycles of absorption and desorption, proving that the stability of the calcium-based absorbent modified by Ti has been improved, and the decrease in the absorption amount may be due to the reduction of the absorption component caused by the doping of Ti. Figure 7State diagram showing the variation of the mass of the MgCa(OH)2 calcium-based absorbent prepared in Example 4 with temperature. By analyzing Figure 7 it can be seen that after the MgCa(OH)2 calcium-based absorbent absorbs CO2 again after the initial regeneration, the mass fraction can reach 145%, and after multiple cycles of absorption and desorption, the mass fraction decays to 125%, proving that the absorption rate and stability of the calcium-based absorbent modified with Mg have both increased, and Mg also has a certain absorption effect on CO2. Thus, it is realized that the magnesium ions in the calcium-based catalyst modified with magnesium can absorb carbon through synergy with calcium ions.

[0082] By analyzing the above experimental data, it can be seen that the present invention designs a method for synthesizing a metal-modified calcium-based absorbent by a simple hydration calcination method. The synthesized metal-modified calcium-based absorbent has the characteristics of high absorption rate, strong stability, and low cost. And for the specific titanium-modified calcium-based absorbent TiCa(OH)2, the mass fraction decrease after multiple cycles of absorption and desorption is about 5%, thus greatly proving that the calcium-based absorbent modified with titanium metal has good stability.

[0083] The above describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A calcium looping carbon capture system, characterized in that, It includes: A capture device, which includes a carbonization furnace (11), a gas-solid separator (12), and a first heat exchanger (13); the CO2 flue gas to be processed enters the carbonization furnace (11) after being heated by the first heat exchanger (13); the carbonization furnace (11) is used to capture carbon from the incoming CO2 flue gas, and the first product after capture is transported to the gas-solid separator (12) for separation to obtain decarbonized flue gas and a first solid mixture; A regeneration device, which includes a bed material heater (21), a calcination furnace (22), a bed material cooler (23), a first cyclone (24) and a second cyclone (25) with different wind speeds; both ends of the bed material heater (21) are respectively connected to the gas-solid separator (12) and the calcination furnace (22), and both ends of the first cyclone (24) are respectively connected to the discharge port of the calcination furnace (22) and the feed port of the second cyclone (25); the separated first solid mixture enters the calcination furnace (22) for calcination after being heated by the bed material heater (21) to obtain a second product containing regenerated calcium-based absorbent, a third gas mixture, and calcium-based absorbent deactivated after carbon adsorption; the first cyclone (24) is used to separate the incoming second product so that the regenerated calcium-based absorbent and the third gas mixture enter the second cyclone (25), and the calcium-based absorbent deactivated after carbon adsorption precipitates to the bottom of the first cyclone (24); the second cyclone (25) is used to perform gas-solid separation on the incoming regenerated calcium-based absorbent and the third gas mixture so that the third gas mixture enters the bed material heater (21) and exchanges heat with the first solid mixture in the bed material heater (21), and the regenerated calcium-based absorbent precipitates to the bottom of the second cyclone (25) and is cooled by the bed material cooler (23) and then recycled to the carbonization furnace (11) for reuse; A cooling device, which is respectively connected to the liquid inlet of the bed material cooler (23) and the liquid inlet of the first heat exchanger (13); the condensed water generated by the cooling device exchanges heat with the second solid mixture passing through the bed material cooler (23) and the CO2 flue gas passing through the first heat exchanger (13) respectively to generate water vapor; A steam turbine (4), which is respectively connected to the gas outlet of the bed material cooler (23) and the gas outlet of the first heat exchanger (13); the steam turbine (4) generates electricity by using the water vapor generated after heat exchange between the cooling device and the bed material cooler (23) and between the cooling device and the first heat exchanger (13).

2. The calcium looping carbon capture system according to claim 1, wherein, The wind speed of the first cyclone (24) is greater than that of the second cyclone (25), and the wind force generated by the first cyclone (24) on the second product is greater than the gravity of the regenerated calcium-based absorbent and less than the gravity of the calcium-based absorbent deactivated after carbon adsorption, and the wind force generated by the second cyclone (25) on the regenerated calcium-based absorbent is less than its own gravity.

3. The calcium looping carbon capture system according to claim 1, characterized in that, The regeneration device further includes an oxygen generator (28) connected to the calciner (22). The oxygen generator (28) is configured to separate oxygen from the air and supply the separated oxygen into the calciner (22).

4. The calcium looping carbon capture system according to claim 1, characterized in that, The capture device further includes a second heat exchanger (14) and a third heat exchanger (15). The two ends of the third heat exchanger (15) are respectively connected to the first heat exchanger (13) and the carbonization furnace (11). The third heat exchanger (15) is configured to convey the CO2 flue gas to be processed after being heated by the first heat exchanger (13) into the carbonization furnace (11). The two ends of the second heat exchanger (14) are respectively connected to the outlet of the gas-solid separator (12) and the inlet of the third heat exchanger (15). The second heat exchanger (14) is further connected to the cooling device. The decarbonized flue gas separated by the gas-solid separator (12) exchanges heat with the water entering the second heat exchanger (14). The decarbonized flue gas after heat exchange enters the third heat exchanger (15) and exchanges heat again with the CO2 flue gas to be processed in the third heat exchanger (15). The water after heat exchange in the second heat exchanger (14) enters the bed material cooler (23) and heats the regenerated calcium-based absorbent in the bed material cooler (23).

5. The calcium looping carbon capture system according to claim 4, characterized in that, The cooling device includes a cooling tower (31), a condenser (32), and a feed water tank (33). The two ends of the condenser (32) are respectively connected to the cooling tower (31) and the feed water tank (33). The cooling tower (31) is configured to supply water. The condenser (32) is configured to cool the water in the cooling tower (31) and convey the cooled water to the feed water tank (33). The feed water tank (33) is respectively connected to the first heat exchanger (13) and the second heat exchanger (14), and conveys the condensed water into the first heat exchanger (13) and the second heat exchanger (14) respectively. The outlet of the steam turbine (4) is connected to the condenser (32), so that the water vapor after steam power generation in the steam turbine (4) is re-condensed into condensed water through the condenser (32).

6. The calcium looping carbon capture system according to claim 5, wherein, The regeneration device further includes a fourth heat exchanger (26) and a condensation device (27). The two ends of the fourth heat exchanger (26) are respectively connected to the bed material heater (21) and the condensation device (27). The water outlet of the condensation device (27) is connected to the water inlet of the cooling tower (31). The fourth heat exchanger (26) is further connected to the cooling device. The fourth heat exchanger (26) is configured to exchange heat between the gas mixture three after being cooled by the bed material heater (21) and the condensed water of the cooling device, and the gas mixture three after heat exchange is conveyed into the condensation device (27). The condensation device (27) is configured to condense the water vapor in the gas mixture three and convey it back to the cooling tower (31).

7. The calcium looping carbon capture system according to claim 1, characterized in that, The calcium loop carbon capture system further includes a first wind speed detector for detecting the wind speed in the first cyclone (24), a second wind speed detector for detecting the wind speed in the second cyclone (25), and a controller; a first wind speed regulator is provided in the first cyclone (24), and a second wind speed regulator is provided in the second cyclone (25); the controller is electrically connected to the first wind speed detector, the second wind speed detector, the first wind speed regulator, and the second wind speed regulator respectively; The controller obtains the wind speed data of the first cyclone (24) through the first wind speed detector and makes the following comparison with the set first threshold range: If the wind speed detected by the first wind speed detector is lower than the set first threshold range, the controller controls the first wind speed regulator to increase the wind speed in the first cyclone (24); If the wind speed detected by the first wind speed detector is greater than the set first threshold range, the controller controls the first wind speed regulator to decrease the wind speed in the first cyclone (24); The controller obtains the wind speed data of the second cyclone (25) through the second wind speed detector and makes the following comparison with the set second threshold range: If the wind speed detected by the second wind speed detector is lower than the set second threshold range, the controller controls the second wind speed regulator to increase the wind speed in the second cyclone (25); If the wind speed detected by the second wind speed detector is greater than the set second threshold range, the controller controls the second wind speed regulator to decrease the wind speed in the second cyclone (25).

8. The calcium looping carbon capture system according to claim 7, characterized in that, The calcium loop carbon capture system further includes a first concentration detector for detecting the CO2 concentration in the carbonation furnace (11) and a second concentration detector for detecting the CO2 concentration in the calcination furnace (22); a first valve is provided between the carbonation furnace (11) and the gas-solid separator (12), a second valve is provided between the calcination furnace (22) and the first cyclone (24), and the controller is electrically connected to the first concentration detector, the second concentration detector, the first valve, and the second valve respectively; If the CO2 concentration detected by the first concentration detector is lower than the set first threshold, the controller opens the first valve, otherwise it does not open the first valve; If the CO2 concentration detected by the first concentration detector is higher than the set second threshold, the controller opens the second valve, otherwise it does not open the second valve.

9. A metal-modified calcium-based absorbent, which uses the calcium loop carbon capture system according to any one of claims 1-7 to capture carbon from CO2 flue gas; the calcium-based absorbent includes one or a mixture of at least two of ZnCa(OH)2, TiCa(OH)2, and MgCa(OH)2.

10. A preparation method of the metal-modified calcium-based absorbent according to claim 9, which includes the following steps: S1: Heat a certain amount of dolomite powder to 950 °C and calcine for 1 h to obtain a CaO precursor; S2: Weigh the CaO precursor and the metal oxide with a mass ratio of 92:11 and mix them in an aqueous alcohol solution to obtain mixture four; the metal oxide includes one of titanium oxide, zinc oxide, and magnesium oxide; after ultrasonicating mixture four for 30 min, heat it at 300 °C to obtain solid particles one; S3: Dry the solid particles one at 900 °C to prepare the metal-modified calcium-based absorbent.

Images