A system and method for solidifying CO2 through a variable temperature and pressure process.
By combining a compressor in the dissolution and precipitation units through a variable temperature and pressure process, low-cost CO2 solidification is achieved, solving the problems of large equipment and high energy consumption in existing technologies, reducing CO2 emission reduction costs and improving economic efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAN TPRI BOILER ENVIRONMENTAL PROTECTION ENG CO LTD
- Filing Date
- 2023-07-14
- Publication Date
- 2026-05-29
AI Technical Summary
Existing CO2 emission reduction technologies and equipment are large, energy-intensive, and costly. Furthermore, the addition of media or reagents increases the cost of CO2 solidification and makes it less economical.
By using a variable temperature and pressure process, and in conjunction with a compressor, CO2 is dissolved under high pressure and carbonate solids are precipitated under low pressure and high temperature, thus avoiding the addition of additional chemical reagents and reducing energy consumption and costs.
It achieves low-cost and high-economic CO2 solidification, reduces equipment pressure resistance requirements and energy consumption, utilizes industrial waste heat to provide thermal energy, and reduces secondary pollution.
Smart Images
Figure CN116899375B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of carbon dioxide emission reduction and relates to a system and method for solidifying CO2 through a variable temperature and pressure process. Background Technology
[0002] The current mainstream CO2 emission reduction approach adopts a combination of capture and storage (CCS), but this method involves a large equipment system, high energy consumption, and high emission reduction costs.
[0003] Swiss scientist Seifritz first proposed the technology of CO2 sequestration through mineralization reactions in 1990 (Nature, 1990, 345(6275), 486-486). The solidification reaction simulates the weathering process in nature, which is thermodynamically favorable. This technology converts CO2 into stable carbonate products through the reaction of CO2 with active metal ions such as calcium and magnesium in ores or industrial solid waste, achieving permanent sequestration. It can directly utilize low-concentration CO2 generated from emission sources such as thermal power plants, reducing the cost of CO2 emission reduction. Solid waste from industrial production (such as steel slag, fly ash, and furnace slag) contains abundant active metals; using solid waste as a reaction raw material can simultaneously achieve carbon emission reduction in thermal power plants and the co-processing of solid waste.
[0004] Since CO2 mineralization in the natural environment requires slow processes under high pressure, current CO2 mineralization technologies mostly employ high pressure conditions and high-temperature heating to accelerate the reaction (CN201310343224, CN201711108761). While these methods can achieve CO2 solidification, pressurizing flue gas to high pressure (~30MPa) requires a large amount of electrical energy, and high-temperature heating is also an energy-intensive method that consumes high-grade heat sources. Another type of CO2 solidification technology assists the CO2 solidification reaction by adding media, such as ammonifying or amination solid waste to increase the reactivity of raw materials with CO2 (CN201310057123, CN202210338660); or by adding reagents such as ammonium sulfate, ammonium nitrate, and ammonia to activate active metals in solid waste, transforming the solidification reaction of CO2 with active metals into a reaction with NH3, thereby increasing the CO2 absorption and conversion rate (CN201610564463, CN201710085347, CN202111248674, CN202210280209). These methods require large amounts of ammonia-based media or other raw materials, resulting in high costs, while the resulting products are less economically viable, increasing the cost of CO2 solidification and emission reduction. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a system and method for solidifying CO2 through a variable temperature and pressure process. This system and method can achieve the purpose of solidifying CO2 and has the characteristics of low cost and high economic efficiency of the obtained product.
[0006] To achieve the above objectives, the CO2 solidification system of the present invention through a variable temperature and pressure process includes a dissolution unit, a precipitation unit, and a compressor;
[0007] The rich liquid outlet of the dissolving unit is connected to the rich liquid inlet of the sedimentation unit, the outlet of the compressor is connected to the gas inlet of the dissolving unit, the dissolving unit is equipped with a decarbonation flue gas outlet and a solid waste residue outlet, the sedimentation unit is equipped with a carbonate precipitation outlet, and the lean liquid outlet of the sedimentation unit is connected to the lean liquid inlet of the dissolving unit.
[0008] The temperature inside the precipitation unit is higher than that inside the dissolution unit, and the pressure inside the precipitation unit is lower than that inside the dissolution unit.
[0009] It also includes a CO2 flue gas inlet pipe, the outlet of which is connected to the gas inlet of the sedimentation unit or the compressor; wherein, when the CO2 flue gas inlet pipe is connected to the gas inlet of the sedimentation unit, the gas outlet of the sedimentation unit is connected to the inlet of the compressor.
[0010] The dissolving unit includes several dissolving modules. The outlet of the compressor is connected to the gas inlet of the last dissolving module, the gas outlet of the next dissolving module is connected to the gas inlet of the previous dissolving module, the lean liquid outlet of the precipitation unit is connected to the lean liquid inlet of the last dissolving module, the rich liquid outlet of the next dissolving module is connected to the lean liquid inlet of the previous dissolving module, and the rich liquid outlet of the first dissolving module is connected to the rich liquid inlet of the precipitation unit.
[0011] The solid waste residue outlet of the previous dissolution module is connected to the solid raw material inlet of the next dissolution module.
[0012] The temperature in the previous dissolution module is lower than the temperature in the next dissolution module, and the pressure in the previous dissolution module is lower than the pressure in the next dissolution module.
[0013] The method for solidifying CO2 through a variable temperature and pressure process according to the present invention includes the following steps:
[0014] 1) Solid waste raw materials are fed into a dissolution unit at a temperature of T1 and a pressure of P1, where active metal ions in the solid waste raw materials leach into the solution; carbon-rich flue gas is pressurized by a compressor and then enters the dissolution unit, where CO2 in the flue gas dissolves in the solution under high pressure, which lowers the pH value of the solution in the dissolution unit and promotes the leaching of metal ions.
[0015] 2) The flue gas after decarbonization in the dissolution unit is discharged, and the solid waste residue after leaching of active metal is subjected to solid-liquid separation. The separated liquid rich in active metal and dissolved CO2 enters the precipitation unit at a temperature of T2 and a pressure of P2, where T2 is greater than T1 and P2 is less than P1.
[0016] 3) In the precipitation unit, CO2 in the rich solution containing active metals and dissolved CO2 is degassed, causing the pH value of the rich solution to increase. Simultaneously, the solubility of calcium and magnesium carbonates decreases with increasing temperature, resulting in the precipitation of carbonate solids and obtaining an active metal / CO2 lean solution.
[0017] 4) The carbonate solids precipitated in the precipitation unit are separated and discharged, and the active metal / CO2 lean solution discharged from the precipitation unit is pumped back into the dissolution unit.
[0018] The ratio of solid waste raw materials to solution in the dissolution unit is 1-30 wt%.
[0019] The ratio of flue gas flow rate to solution flow rate in the dissolution unit is (1-10):1.
[0020] The system for solidifying CO2 through a variable temperature and pressure process also includes a CO2 flue gas input pipe; the outlet of the CO2 flue gas input pipe is connected to the gas inlet of the precipitation unit or the compressor; wherein, when the CO2 flue gas input pipe is connected to the gas inlet of the precipitation unit, the gas outlet of the precipitation unit is connected to the inlet of the compressor.
[0021] The flue gas output from the CO2 flue gas input pipe enters the sedimentation unit, mixes with the CO2 gas obtained from degassing, and is then compressed by the compressor before being sent to the dissolution unit.
[0022] The dissolving unit includes several dissolving modules, which are connected in series. The outlet of the compressor is connected to the gas inlet of the last dissolving module, the gas inlet of the previous dissolving module is connected to the gas outlet of the next dissolving module, the lean liquid outlet of the precipitation unit is connected to the lean liquid inlet of the last dissolving module, the rich liquid outlet of the next dissolving module is connected to the lean liquid inlet of the previous dissolving module, and the rich liquid outlet of the first dissolving module is connected to the rich liquid inlet of the precipitation unit.
[0023] The solid waste residue outlet of the previous dissolution module is connected to the solid raw material inlet of the next dissolution module.
[0024] The temperature in the previous dissolution module is lower than the temperature in the next dissolution module, and the pressure in the previous dissolution module is lower than the pressure in the next dissolution module.
[0025] The present invention has the following beneficial effects:
[0026] In the specific operation of the system and method for solidifying CO2 through a variable temperature and pressure process described in this invention, active metal ions from the solid waste raw material are leached into a solution in the dissolution unit. Carbon-rich flue gas, after being pressurized by a compressor, enters the dissolution unit, where CO2 in the flue gas dissolves in the solution under high pressure, lowering the pH value of the solution in the dissolution unit and promoting the leaching of metal ions. Simultaneously, some CO2 reacts with water and metal ions to generate carbonates, thus achieving the purpose of CO2 solidification. The solid waste residue after active metal leaching undergoes solid-liquid separation. The resulting rich solution, rich in active metals and dissolved CO2, enters the precipitation unit. In the precipitation unit, the CO2 in the rich solution is degassed, increasing the pH value of the solution and precipitating carbonate solids. The entire process does not require the consumption of ammonia-based media or other raw materials, resulting in low cost and highly economical products. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention.
[0028] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the present invention.
[0029] Figure 3 This is a schematic diagram of the structure of Embodiment 3 of the present invention.
[0030] Among them, 1 is the dissolution unit, 2 is the precipitation unit, 3 is the compressor, and 4 is the dissolution module. Detailed Implementation
[0031] To enable those skilled in the art to better understand the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, not all embodiments, and are not intended to limit the scope of the present invention. Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion regarding the concepts disclosed in the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.
[0032] The accompanying drawings show structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not drawn to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.
[0033] The method for solidifying CO2 through a variable temperature and pressure process according to the present invention includes the following steps:
[0034] 1) Solid waste raw materials are fed into dissolution unit 1 at temperature T1 and pressure P1, where active metal ions such as calcium and magnesium in the solid waste raw materials leach into the solution; carbon-rich flue gas is pressurized by compressor 3 and then enters dissolution unit 1, where CO2 dissolves in water under high pressure, causing the pH value of the solution in dissolution unit 1 to decrease and promoting the leaching of metal ions. Let M be the active metal (Ca, Mg), and X be the anion corresponding to M in the solid waste. Then the following chemical reactions occur in dissolution unit 1:
[0035] CO2(g) + H2O(l) → H2CO3(aq)
[0036] MX(s)+H2CO3(aq)→MCO3(aq)+HX(aq / s)
[0037] Because the temperature in dissolution unit 1 is low, the generated carbonate has high solubility and can dissolve in water without precipitating, thus preventing the solidified product from depositing on the solid surface and hindering the leaching of active metal ions.
[0038] 2) The flue gas after decarbonization in dissolution unit 1 is discharged, and the solid waste residue after leaching of active metal is subjected to solid-liquid separation. The separated liquid rich in active metal and dissolved CO2 enters precipitation unit 2 at a temperature of T2 and a pressure of P2, where T2 is greater than T1 and P2 is less than P1.
[0039] 3) In precipitation unit 2, CO2 in the rich solution containing active metals and dissolved CO2 is degassed, causing the pH value of the rich solution to increase. At the same time, the solubility of calcium and magnesium carbonates decreases with increasing temperature, resulting in the precipitation of carbonate solids and obtaining an active metal / CO2 lean solution.
[0040] MCO3(aq)→MCO3(s)
[0041] The carbonate solids precipitated in precipitation unit 2 are separated and discharged. The active metal / CO2 lean solution discharged from precipitation unit 2 is pumped back into dissolution unit 1 to form a solution cycle.
[0042] In this embodiment, T1 is 20℃-90℃, P1 is 0.2-2MPa; T2 is 50-100℃, P2 is 0.1-1MPa.
[0043] In this embodiment, the ratio (solid-liquid ratio) of solid waste raw material to circulating solution in the dissolution unit 1 is 1-30 wt%.
[0044] In this embodiment, the ratio of flue gas flow rate to circulating solution flow rate in the dissolution unit 1 is (1-10):1.
[0045] In this embodiment, the flue gas containing CO2 first passes through the precipitation unit 2, then mixes with the CO2 obtained from degassing in step 3), and then enters the dissolution unit 1 through the compressor 3.
[0046] Preferably, the dissolving unit 1 is composed of several dissolving modules 4 connected in series. The solution flows sequentially from the first dissolving module 4 to the last dissolving module 4, while the flue gas flows sequentially from the last dissolving module 4 to the first dissolving module 4. That is, the flow directions of the flue gas and the solution are opposite. Let the temperatures from the first dissolving module 4 to the nth dissolving module 4 be T11…T1n, and the pressures from the first dissolving module 4 to the nth dissolving module 4 be P11…P1n, then T1…T1n ... <T11<…<T1n<T2,P1n> …>P11>P1>P2. It should be noted that while lower temperatures are beneficial for increasing carbonate solubility, raising the temperature can promote the leaching process of active metal ions such as calcium and magnesium. Therefore, gradually increasing the temperature during the solid leaching process is beneficial for metal ion leaching. Furthermore, as the solution flows counter-currently from the nth dissolution module 4 to the first dissolution module 4, the carbonate concentration in the solution gradually increases, thus the temperature in the first dissolution module 4 is lower, which is beneficial for carbonate dissolution.
[0047] Example 1
[0048] refer to Figure 1 This embodiment includes a dissolution unit 1 and a precipitation unit 2. Solid waste raw materials are fed into the dissolution unit 1 at 30°C and 0.5 MPa, with a solid-liquid ratio of 5 wt%, where active metal ions such as calcium and magnesium leach into the solution. Carbon-rich flue gas is pressurized by compressor 3 and then enters the dissolution unit 1, with a flue gas to solution volume flow ratio of 5:1. CO2 dissolves in the water under high pressure, and the solution pH decreases to 6.15. After decarbonization, the flue gas is discharged from the dissolution unit 1, and the solid waste residue after active metal leaching is discharged after solid-liquid separation. The separated active metal / CO2-rich solution enters the precipitation unit 2 at 90°C and 0.1 MPa. A portion of the dissolved CO2 is degassed and enters the gas phase before being discharged, reducing the acidity of the solution and raising the pH to 7.88. The solubility of calcium and magnesium carbonates decreases with increasing temperature, forming carbonate precipitates. The carbonate solids are discharged after solid-liquid separation, and the separated active metal / CO2-poor solution is pumped back into the dissolution unit 1, forming a solution cycle.
[0049] By analyzing and comparing the active metal content in the solid waste residue and the solid waste raw materials after the reaction, the active metal leaching rate was found to be 87.2%; by comparing the active metal content in the carbonate precipitate and the solid waste raw materials, the solidification rate was found to be 75.9%.
[0050] Example 2
[0051] refer to Figure 2The difference between this embodiment and Embodiment 1 is that the flue gas containing CO2 is first sent into the precipitation unit 2 and mixed with the CO2 obtained from degassing in the precipitation unit 2, which further increases the CO2 concentration in the flue gas. Then, after being pressurized by the compressor 3, it enters the dissolution unit 1, where CO2 dissolves in water under high pressure, and the pH of the solution decreases to 6.07.
[0052] By analyzing and comparing the active metal content in the solid waste residue and the solid waste raw materials after the reaction, the active metal leaching rate was found to be 91.4%; by comparing the active metal content in the carbonate precipitate and the solid waste raw materials, the solidification rate was found to be 67.2%.
[0053] Example 3
[0054] refer to Figure 3 This embodiment includes a first dissolution module 4, a second dissolution module 4, and a precipitation unit 2 connected in series.
[0055] Solid waste raw materials sequentially pass through the first dissolution module 4 at 30℃ and 0.3MPa and the second dissolution module 4 at 60℃ and 0.5MPa, with a solid-liquid ratio of 5wt%. The active metal / CO2 lean solution from precipitation unit 2 flows counter-currently to the solid material, first entering the second dissolution module 4 and then the first dissolution module 4. Carbon-rich flue gas, after being pressurized by compressor 3, first enters the second dissolution module 4 and then the first dissolution module 4, with a flue gas to solution volume flow ratio of 5:1. CO2 dissolves in water under high pressure. The pH of the solution in the second dissolution module 4 decreases to 6.79, and the pH of the solution in the first dissolution module 4 decreases to 6.27. While lower temperatures are beneficial for increasing the solubility of carbonates, higher temperatures promote the leaching of active metal ions such as calcium and magnesium. Therefore, gradually increasing the temperature during the solid leaching process (first dissolution module 4 → second dissolution module 4) is beneficial for the leaching of metal ions. As the solution flows in reverse from the second dissolving module 4 to the first dissolving module 4, the carbonate concentration in the solution gradually increases. The temperature of the solution in the first dissolving module 4 is lower, which is conducive to the dissolution of carbonate.
[0056] After decarbonization, the flue gas is discharged from the first dissolution module 4, and the solid waste residue after active metal leaching is discharged from the second dissolution module 4 after solid-liquid separation. The separated active metal / CO2 rich solution is discharged from dissolution unit 1 and enters precipitation unit 2 at 90℃ and 0.1MPa. A portion of the dissolved CO2 is degassed and discharged into the gas phase, and the acidity of the solution decreases, with the pH value rising to 7.97. The solubility of calcium and magnesium carbonates decreases with increasing temperature, forming carbonate precipitates. The carbonate solids are discharged after solid-liquid separation, and the separated active metal / CO2 lean solution is pumped back into the second dissolution module 4, forming a solution cycle.
[0057] By analyzing and comparing the active metal content in the solid waste residue and the solid waste raw materials after the reaction, the active metal leaching rate was found to be 96.0%; by comparing the active metal content in the carbonate precipitate and the solid waste raw materials, the solidification rate was found to be 89.2%.
[0058] Example 4
[0059] The difference between this embodiment and Embodiment 1 is that the solid-liquid ratio of the solid waste raw material entering the dissolution unit 1 is 20wt%.
[0060] By analyzing and comparing the active metal content in the solid waste residue and the solid waste raw materials after the reaction, the active metal leaching rate was found to be 82.3%; by comparing the active metal content in the carbonate precipitate and the solid waste raw materials, the solidification rate was found to be 79.4%.
[0061] Example 5
[0062] The difference between this embodiment and Embodiment 1 is that the temperature of the dissolution unit 1 is 60°C.
[0063] By analyzing and comparing the active metal content in the solid waste residue and the solid waste raw materials after the reaction, the active metal leaching rate was found to be 76.3%; by comparing the active metal content in the carbonate precipitate and the solid waste raw materials, the solidification rate was found to be 68.5%.
[0064] Example 6
[0065] The difference between this embodiment and Embodiment 1 is that the pressure of the dissolution unit 1 is 1.0 MPa.
[0066] By analyzing and comparing the active metal content in the solid waste residue and the solid waste raw materials after the reaction, the active metal leaching rate was found to be 92.3%; by comparing the active metal content in the carbonate precipitate and the solid waste raw materials, the solidification rate was found to be 81.7%.
[0067] It should be noted that the present invention has the following characteristics:
[0068] Using bulk industrial solid waste ash and slag generated during coal combustion, steelmaking, and mining as carbon sequestration raw materials is a low-cost and widely available approach that achieves resource utilization of solid waste while reducing carbon emissions.
[0069] High CO2 solidification conversion rate: Separating dissolution unit 1 from precipitation unit 2 avoids the deposition of solidified products on the solid surface, which hinders further reaction; the low temperature and high CO2 pressure of dissolution unit 1 are conducive to CO2 mass transfer and reduce the pH value of the solution, promoting the leaching of active metals and increasing the solubility of carbonates; the high temperature and low CO2 pressure of precipitation unit 2 reduce proton activity (acidity) and the solubility of calcium and magnesium carbonates, causing carbonates to precipitate.
[0070] No additional chemical reagents or other auxiliary reactions are required, thus avoiding secondary pollution.
[0071] The lower reaction pressure reduces the compression work required to raise the carbon-rich flue gas to high pressure, thereby reducing the power consumption of compressor 3 and lowering the pressure resistance requirements of equipment and instruments.
[0072] The reaction temperature is low, and low-grade waste heat from industries such as thermal power plants can be used to provide heat energy for the CO2 solidification process, realizing waste heat utilization and low energy consumption cost.
[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.
Claims
1. A system for solidifying CO2 through a variable temperature and pressure process, characterized in that, It includes a dissolving unit (1), a precipitation unit (2), and a compressor (3); The rich liquid outlet of the dissolving unit (1) is connected to the rich liquid inlet of the sedimentation unit (2), the outlet of the compressor (3) is connected to the gas inlet of the dissolving unit (1), the dissolving unit (1) is provided with a decarbonation flue gas outlet and a solid waste residue outlet, the sedimentation unit (2) is provided with a carbonate precipitation outlet, and the lean liquid outlet of the sedimentation unit (2) is connected to the lean liquid inlet of the dissolving unit (1). The temperature inside the precipitation unit (2) is higher than the temperature inside the dissolution unit (1), and the pressure inside the precipitation unit (2) is lower than the pressure inside the dissolution unit (1). The dissolving unit (1) includes several dissolving modules (4). The outlet of the compressor (3) is connected to the gas inlet of the last dissolving module (4). The gas outlet of the next dissolving module (4) is connected to the gas inlet of the previous dissolving module (4). The lean liquid outlet of the precipitation unit (2) is connected to the lean liquid inlet of the last dissolving module (4). The rich liquid outlet of the next dissolving module (4) is connected to the lean liquid inlet of the previous dissolving module (4). The rich liquid outlet of the first dissolving module (4) is connected to the rich liquid inlet of the precipitation unit (2). The solid waste residue outlet of the previous dissolution module (4) is connected to the solid raw material inlet of the next dissolution module (4).
2. The system for solidifying CO2 via a variable temperature and pressure process according to claim 1, characterized in that, It also includes a CO2 flue gas input pipe, the outlet of which is connected to the gas inlet of the sedimentation unit (2) or the compressor (3); wherein, when the CO2 flue gas input pipe is connected to the gas inlet of the sedimentation unit (2), the gas outlet of the sedimentation unit (2) is connected to the inlet of the compressor (3).
3. The system for solidifying CO2 via a variable temperature and pressure process according to claim 1, characterized in that, The temperature in the previous dissolution module (4) is lower than the temperature in the next dissolution module (4), and the pressure in the previous dissolution module (4) is lower than the pressure in the next dissolution module (4).
4. A method for solidifying CO2 through a variable temperature and pressure process, characterized in that, The system for solidifying CO2 via a variable temperature and pressure process as described in claim 1 includes the following steps: 1) The solid waste material is fed into the dissolution unit (1) at a temperature of T1 and a pressure of P1, and the active metal ions in the solid waste material are leached into the solution; the carbon-rich flue gas is pressurized by the compressor (3) and then enters the dissolution unit (1). The CO2 in the flue gas dissolves in the solution under high pressure, which lowers the pH value of the solution in the dissolution unit (1) and promotes the leaching of metal ions. 2) The flue gas after decarbonization in the dissolution unit (1) is discharged, and the solid waste residue after leaching of active metal is subjected to solid-liquid separation. The liquid rich in active metal and dissolved CO2 obtained after separation enters the precipitation unit (2) at a temperature of T2 and a pressure of P2, where T2 is greater than T1 and P2 is less than P1. 3) In the precipitation unit (2), CO2 in the rich solution containing active metal and dissolved CO2 is degassed, which increases the pH value of the rich solution. At the same time, the solubility of calcium and magnesium carbonate decreases with increasing temperature, so as to precipitate carbonate solids and obtain active metal / CO2 lean solution. 4) The carbonate solid precipitated in the precipitation unit (2) is separated and discharged, and the active metal / CO2 lean solution discharged from the precipitation unit (2) is pumped back into the dissolution unit (1).
5. The method for solidifying CO2 through a variable temperature and pressure process according to claim 4, characterized in that, The ratio of solid waste raw material to solution in the dissolution unit (1) is 1-30 wt%.
6. The method for solidifying CO2 through a variable temperature and pressure process according to claim 4, characterized in that, The ratio of flue gas flow rate to solution flow rate in the dissolution unit (1) is (1-10):
1.
7. The method for solidifying CO2 through a variable temperature and pressure process according to claim 4, characterized in that, The system for solidifying CO2 through a variable temperature and pressure process also includes a CO2 flue gas input pipe; the outlet of the CO2 flue gas input pipe is connected to the gas inlet of the sedimentation unit (2) or the compressor (3), wherein when the CO2 flue gas input pipe is connected to the gas inlet of the sedimentation unit (2), the gas outlet of the sedimentation unit (2) is connected to the inlet of the compressor (3). The flue gas output from the CO2 flue gas input pipe enters the sedimentation unit (2), mixes with the CO2 gas obtained from degassing, and is then compressed by the compressor (3) and sent to the dissolution unit (1).
8. The method for solidifying CO2 through a variable temperature and pressure process according to claim 4, characterized in that, The dissolving unit (1) includes several dissolving modules (4), which are connected in series. The outlet of the compressor (3) is connected to the gas inlet of the last dissolving module (4), the gas inlet of the previous dissolving module (4) is connected to the gas outlet of the next dissolving module (4), the lean liquid outlet of the precipitation unit (2) is connected to the lean liquid inlet of the last dissolving module (4), the rich liquid outlet of the next dissolving module (4) is connected to the lean liquid inlet of the previous dissolving module (4), and the rich liquid outlet of the first dissolving module (4) is connected to the rich liquid inlet of the precipitation unit (2). The solid waste residue outlet of the previous dissolution module (4) is connected to the solid raw material inlet of the next dissolution module (4).
9. The method for solidifying CO2 through a variable temperature and pressure process according to claim 8, characterized in that, The temperature in the previous dissolution module (4) is lower than the temperature in the next dissolution module (4), and the pressure in the previous dissolution module (4) is lower than the pressure in the next dissolution module (4).