A system and method for indirect mineralization of CO2 using desulfurized gypsum

Abstract

The application discloses a system and method for capturing CO2 by indirect mineralization of desulfurization gypsum, and the system comprises a desulfurization gypsum leaching device for leaching Ca in desulfurization gypsum by an ammonium salt solution 2+ , obtaining a calcium-rich leaching solution; a calcium silicate generating device for generating calcium silicate by reacting the calcium-rich leaching solution with a silicate; a CO2 absorption device for absorbing CO2 by an alkali solution, generating a carbonate solution; and a calcium carbonate generating device for converting calcium silicate into calcium carbonate and regenerating the alkali solution by reacting the calcium silicate with the carbonate solution. The application can make the desulfurization gypsum be resourceized and utilized, and meanwhile, can mineralize and store CO2.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of solid waste treatment and resource utilization, and particularly relates to a system and method for indirectly mineralizing and capturing CO2 by using desulfurization gypsum. BACKGROUND

[0002] In recent years, in order to reduce the damage of harmful gases such as sulfur dioxide and carbon dioxide to the environment and reduce the adverse effects on social development, the production of flue gas desulfurization gypsum produced by the wet desulfurization process of power plants, large boilers and other enterprises continues to rise.

[0003] At present, in addition to the main component CaSO4·2H2O, desulfurization gypsum also contains a small amount of heavy metal elements, and has the characteristics of high decomposition temperature and complex composition; in view of the above situation, only a small part of desulfurization gypsum is recycled and utilized, and most of it is directly stored as solid waste. A large amount of idle desulfurization gypsum not only wastes Ca, S and other resources, but also occupies land resources; in addition, it will also flow into the natural environment under the action of rainwater, surface water and the like, causing a certain pollution to the environment.

[0004] If the calcium element in the desulfurization gypsum can be recovered and used to react with CO2 to generate stable carbonate, simulating the mineral carbonation process in nature, the problem of resource utilization of desulfurization gypsum can be effectively solved, and it is also a very beneficial CO2 capture and storage technology. However, the decomposition temperature of desulfurization gypsum is high, and it is completely decomposed at about 1400℃, which consumes a lot of energy and is not suitable for direct conversion into calcium oxide; and calcium oxide needs to react with CO2 in an aqueous solution, and the efficiency of mineralizing CO2 is also low. SUMMARY

[0005] The present application aims to provide a system and method for indirectly mineralizing and capturing CO2 by using desulfurization gypsum, to solve one or more of the above technical problems. The technical solution provided by the present application can make the desulfurization gypsum be resourcefully utilized, and at the same time, the CO2 can be mineralized and stored.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] The present application provides a system for indirectly mineralizing and capturing CO2 by using desulfurization gypsum, comprising:

[0008] A desulfurization gypsum leaching device is used to leach Ca 2+ in the desulfurization gypsum by using an ammonium salt solution, to obtain a calcium-rich leaching solution;

[0009] A calcium silicate generating device is used to generate calcium silicate by reacting the calcium-rich leaching solution with a silicate;

[0010] A CO2 absorption device is used to absorb CO2 by using an alkali solution to generate a carbonate solution;

[0011] A calcium carbonate generating device for converting calcium silicate into calcium carbonate and regenerating lye by reacting the calcium silicate with the carbonate solution.

[0012] Further improvements of the present application are that,

[0013] The desulfurization gypsum leaching device comprises a drying device, a crusher, a first stirring tank and an ammonium salt solution supply device;

[0014] The drying device is used for inputting desulfurization gypsum and performing drying treatment, and outputting dried desulfurization gypsum; the crusher is used for inputting the dried desulfurization gypsum and performing crushing treatment, and outputting desulfurization gypsum dry powder with a particle size meeting preset requirements; the first stirring tank is provided with a liquid inlet, a feed inlet, a liquid outlet and a discharge outlet; the feed inlet of the first stirring tank is used for inputting desulfurization gypsum dry powder; the liquid inlet of the first stirring tank is connected with the ammonium salt solution supply device and is used for inputting ammonium salt solution; the liquid outlet of the first stirring tank is used for outputting calcium-rich leaching liquid; and the discharge outlet of the first stirring tank is used for inputting residual material.

[0015] Further improvements of the present application are that,

[0016] The calcium silicate generating device comprises a second stirring tank and a silicate supply device;

[0017] The second stirring tank is provided with a liquid inlet, a feed inlet, a liquid outlet and a discharge outlet; the liquid inlet of the second stirring tank is used for inputting calcium-rich leaching liquid, the feed inlet of the second stirring tank is connected with the silicate supply device and is used for inputting silicate; the liquid outlet of the second stirring tank is used for outputting waste liquid; and the discharge outlet of the second stirring tank is used for outputting calcium silicate.

[0018] Further improvements of the present application are that,

[0019] The CO2 absorption device comprises a bubbling reactor;

[0020] The bottom of the bubbling reactor is provided with a liquid output end and a CO2 gas inlet end, and the upper portion is provided with a lye input end and a CO2 gas outlet end; the liquid output end is used for outputting carbonate solution, the CO2 gas inlet end is used for inputting CO2, the lye input end is used for inputting lye, and the CO2 gas outlet end is used for outputting residual CO2 after reaction.

[0021] Further improvements of the present application are that,

[0022] The calcium carbonate generating device comprises a stirring reactor;

[0023] The stirred reactor is provided with a feed inlet, a liquid inlet, a discharge outlet, and a liquid outlet. The liquid inlet of the stirred reactor is used to input carbonate solution, the feed inlet of the stirred reactor is used to input calcium silicate, the discharge outlet of the stirred reactor is used to output solid product, and the liquid outlet of the stirred reactor is used to output alkaline solution.

[0024] The solid products include calcium carbonate and silicon dioxide.

[0025] A further improvement of the present invention is that the first stirring tank or the second stirring tank is provided with an ammonia recovery and introduction device; the ammonia recovery and introduction device is used to prevent ammonia from escaping from the ammonium salt solution during gypsum leaching or conversion, and to avoid NH4 in the solution. + The solubility decreases.

[0026] This invention provides a method for indirectly mineralizing and capturing CO2 using desulfurized gypsum, comprising the following steps:

[0027] Ca was extracted from desulfurized gypsum by leaching with ammonium salt solution. 2+ , thus obtaining a calcium-rich leachate;

[0028] Calcium silicate is generated by reacting the calcium-rich leachate with silicates.

[0029] CO2 is absorbed by an alkaline solution to generate a carbonate solution;

[0030] The calcium silicate is converted into calcium carbonate and an alkaline solution is generated by reacting the calcium silicate with the carbonate solution.

[0031] A further improvement of the present invention is that the alkaline solution generated by the reaction of the calcium silicate with the carbonate solution is used to supply the reaction in which CO2 is absorbed by the alkaline solution.

[0032] A further improvement of the present invention is that,

[0033] The process of extracting Ca from desulfurized gypsum using ammonium salt solution 2+ The steps to obtain calcium-rich leachate include: mixing desulfurized gypsum powder with ammonium salt solution at a solid-liquid ratio of 10-50 g / L, stirring at 30-60°C to fully leach out the desulfurized gypsum, filtering, and obtaining calcium-rich leachate.

[0034] The step of generating calcium silicate by reacting the calcium-rich leachate with silicate includes adding silicate to the calcium-rich leachate at a molar ratio of Ca / Si = 0.5 to 1.5, stirring and mixing at room temperature to generate the solid product calcium silicate.

[0035] In the step of converting calcium silicate into calcium carbonate and generating an alkaline solution by reacting the calcium silicate with the carbonate solution, the solid-liquid ratio of calcium silicate to carbonate solution is 20-200 g / L; the reaction temperature is 20-60℃.

[0036] The further improvement of the present application is that,

[0037] The desulfurization gypsum is flue gas desulfurization gypsum generated by a wet desulfurization process.

[0038] The ammonium salt solution is one or more of an ammonium chloride solution, an ammonium sulfate solution, an ammonium acetate solution, an ammonium nitrate solution and an ammonium phosphate solution.

[0039] The silicate is one or more of lithium silicate, sodium silicate and potassium silicate. Compared with the prior art, the present application has the following beneficial effects:

[0040] At present, most of the desulfurization gypsum is piled up, occupies land and is easy to cause environmental pollution, and does not play the utilization value of the desulfurization gypsum; the present application can store CO2 by using the desulfurization gypsum, not only realizes the resource utilization of the desulfurization gypsum, but also reduces the emission of CO2, and the finally generated solid product can also be resource utilized, reducing resource waste.

[0041] In the method provided by the present application, the recovery of calcium elements from desulfurization gypsum is combined with CO2 mineralization, mainly including three parts of gypsum conversion, mineralization carbon sequestration and CO2 absorption; the desulfurization gypsum is leached by using an ammonium salt, the leaching of calcium is improved, and the calcium is converted into calcium silicate at normal temperature, the overall process requires low temperature and consumes less energy.

[0042] In the present application, the alkali liquor (for example, a sodium hydroxide solution or a potassium hydroxide solution, etc.) is used to absorb CO2, and the CO2 is mineralized by using a carbonate solution as a medium, and is converted into stable calcium carbonate, compared with using industrial residues or calcium oxide to capture CO2, the absorption rate is greatly improved, and the alkali liquor can be recycled, improving the economy of the technology. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following briefly introduces the drawings needed to be used in the embodiments or prior art description; obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0044] Figure 1 is a structure schematic diagram of a system for indirectly mineralizing and capturing CO2 by using desulfurization gypsum provided by an embodiment of the present application;

[0045] In the figure, 1, drying device; 2, crusher; 3, ammonium salt solution supply device; 4, first stirring tank; 5, silicate supply device; 6, second stirring tank; 7, stirring reactor; 8, bubbling reactor; 9, discharge port; 10, CO2 gas inlet end; 11, lye input end; 12, CO2 gas outlet end; 13, ammonia gas recovery introduction device. DETAILED DESCRIPTION

[0046] In order to make the person skilled in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the protection scope of the present application.

[0047] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0048] The present application will be described in further detail below in conjunction with the accompanying drawings:

[0049] The system for capturing CO2 by indirect mineralization of desulfurization gypsum provided by the embodiments of the present application comprises a gypsum leaching device, a calcium silicate generating device, a CO2 absorption device and a calcium carbonate generating device, wherein,

[0050] The gypsum leaching device adopts a first stirring tank 4, which is provided with a liquid inlet, a feed inlet, a liquid outlet and a discharge port; the feed inlet is communicated with the outlet of the crusher 2, and is used for inputting desulfurization gypsum after drying treatment; the liquid inlet is communicated with the ammonium salt solution supply device 3, and is used for inputting an ammonium salt solution; and the liquid outlet is communicated with the liquid inlet of the calcium silicate generating device.

[0051] The calcium silicate generating device adopts a second stirring tank 6, which is provided with a liquid inlet, a feed inlet, a liquid outlet and a discharge port; the feed inlet is communicated with the silicate supply device 5, and is used for inputting a silicate; and the discharge port is communicated with the feed inlet of the calcium carbonate generating device;

[0052] The calcium carbonate generating device adopts a stirring reactor 7, which is provided with a feeding port, a liquid inlet port, a discharging port 9 and a liquid outlet port; the liquid inlet port is communicated with the liquid output end of the CO2 absorption device; a filter screen is arranged at the liquid outlet port to achieve solid-liquid separation, and the liquid outlet port is communicated with the alkali liquid input end 11 of the CO2 absorption device.

[0053] The CO2 absorption device adopts a bubbling reactor 8, which is provided with a liquid output end and a CO2 gas inlet end 10 at the bottom, and an alkali liquid input end 11 and a CO2 gas outlet end 12 at the upper portion; preferably, the CO2 gas outlet end 12 is communicated with the CO2 gas inlet channel to output the unabsorbed CO2.

[0054] The method for capturing CO2 by indirect mineralization of desulfurization gypsum provided by the embodiment of the application comprises the following steps:

[0055] (1) Desulfurization gypsum leaching: After the desulfurization gypsum is treated by a drying device 1 and a crusher 2, desulfurization gypsum powder with a particle size less than 0.2 mm is obtained, which is sent into a first stirring tank to be mixed with an ammonium salt solution at a solid-liquid ratio of 10-50 g / L; after being stirred at a temperature of 30-60 DEG C for 30-90 min, the desulfurization gypsum is fully leached, and then filtered to obtain a Ca-rich leaching solution which is sent into a second stirring tank;

[0056] (2) Calcium silicate generation: a silicate is added into the second stirring tank at a molar ratio of Ca / Si=0.5-1.5, and is fully stirred and mixed with the Ca-rich leaching solution obtained in step (1) to generate a solid product calcium silicate (CaSiO3) after reaction for 10-60 min;

[0057] (3) CO2 absorption: sodium hydroxide solution or potassium hydroxide solution is added into the bubbling reactor 8 from the alkali liquid input end 11, and CO2 flue gas is introduced into the bubbling reactor 8 from the bottom gas inlet end, so that the CO2 is absorbed by the alkali liquid in the bubbling reactor 8 to obtain a carbonate solution; a small amount of unabsorbed CO2 flue gas is sent back to the CO2 gas inlet channel through the upper gas outlet end, or directly discharged into the atmosphere.

[0058] (4) Mineralization and carbon sequestration: the calcium silicate generated in step (2) is sent into the stirring reactor 7 through the discharging port of the calcium silicate generating device, and the carbonate solution is transported into the stirring reactor 7 through the liquid output end of the bubbling reactor 8; after being stirred in the stirring reactor 7 for 10-60 min, the discharging port 9 of the stirring reactor 7 outputs the generated calcium carbonate and silicon dioxide, and the liquid outlet port of the stirring reactor 7 outputs the generated alkali liquid to realize the recycling and regeneration of the alkali liquid; first, the alkali liquid is transported into the bubbling reactor 8 through the liquid outlet port to continue absorbing CO2 flue gas; then, the mixed solid of calcium carbonate and silicon dioxide is discharged from the discharging port.

[0059] The embodiment of the present application is specifically exemplified, in step (1), the ammonium salt solution can adopt at least one of the following: ammonium chloride solution, or ammonium sulfate solution, or ammonium acetate solution, or ammonium nitrate solution, or ammonium phosphate solution; in step (2), the silicate can adopt at least one of the following: Li2SiO3, or Na2SiO3, or K2SiO3; in step (3), the CO2 flue gas can be pure CO2 gas, or flue gas discharged by oxygen-enriched combustion and traditional air atmosphere combustion in a factory, or air, and the CO2 volume concentration is 0% to 100%. In step (4), the solid-liquid ratio of calcium silicate (CaSiO3) and carbonate solution is 20 to 200 g / L, the stirring rate of the stirring reactor is 100 to 300 r / min, and the reaction temperature is 20 to 60℃.

[0060] In the embodiment of the present application, in step (4), the mixing ratio (molar ratio) of calcium carbonate and silicon dioxide is 1:1 to 4:1, and after drying, the calcium carbonate can be used for preparing cement.

[0061] In summary, the technical scheme of the embodiment of the present application takes the power plant wet desulfurization by-product gypsum as a calcium source, and in a gypsum leaching device, the ammonium salt solution is used to leach Ca2+ in the gypsum, so that a calcium-rich leaching solution is obtained. 2+ The calcium-rich leaching solution is reacted with silicate in a calcium silicate generating device to generate calcium silicate; the alkali solution (sodium hydroxide or potassium hydroxide solution) in the bubbling reactor is used to absorb CO2 to generate a carbonate solution, the carbonate solution is sent into a stirring reactor, calcium silicate is converted into calcium carbonate by reacting calcium silicate with the carbonate solution, and the alkali solution is regenerated, and the regenerated alkali solution is sent back to the bubbling reactor to continue absorbing CO2; the present application can realize cyclic absorption and mineralization of CO2, and the desulfurization gypsum can be resourceized.

[0062] Please refer to Figure 1 The embodiment of the present application specifically provides a system for indirectly mineralizing and capturing CO2 by using desulfurization gypsum, which comprises: a first stirring tank 4, a second stirring tank 6, a stirring reactor 7, and a bubbling reactor 8.

[0063] The first stirring tank 4 and the second stirring tank 6 are both provided with a liquid inlet, a feed inlet, a liquid outlet, and a feed outlet, the feed inlet of the first stirring tank 4 is communicated with the outlet of a crusher 2, the liquid inlet is communicated with an ammonium salt solution supply device 3, and the liquid outlet is communicated with the liquid inlet of the second stirring tank 6; the feed inlet of the second stirring tank 6 is communicated with a silicate supply device 5, and the feed outlet is communicated with the feed inlet of the stirring reactor 7; wherein, the first stirring tank 4 and the second stirring tank 6 are both provided with an ammonia gas recovery and introduction device 13, so as to prevent ammonia gas from escaping in the process of leaching and converting the ammonium salt solution, and to prevent safety hazards and cause the NH4+ solubility in the solution to decrease. In addition, a desulfurization gypsum supply device, a drying device 1, and the crusher 2 are sequentially connected along the flow direction of the desulfurization gypsum, so as to provide the first stirring tank 4 with desulfurization gypsum powder. + ​

[0064] The bottom of the bubbling reactor 8 is provided with a liquid output end and a CO2 gas inlet end 10, and the upper part is provided with a sodium hydroxide solution input end and a CO2 gas outlet end 12, which is communicated with the CO2 gas inlet channel. The stirring reactor 7 is provided with a feeding port, a liquid inlet and a discharging port, and a liquid outlet, the liquid inlet is communicated with the liquid output end of the bubbling reactor 8; a filter screen is arranged at the liquid outlet, and the sodium hydroxide solution input end of the bubbling reactor 8 is communicated with the liquid outlet.

[0065] The present application provides a specific embodiment for testing the effect of desulfurization gypsum mineralization CO2 under laboratory conditions, which specifically comprises the following steps:

[0066] (1) Desulfurization gypsum leaching: In the embodiment, the by-product desulfurization gypsum generated by a power plant is selected, treated by an oven and a crusher 2, and 100g of desulfurization gypsum powder with a particle size of less than 100μm is obtained, which is sent into the first stirring tank 4, mixed with 1mol / L NH4Cl solution at a solid-liquid ratio of 20g / L, stirred at 30℃ for 60min, and the leaching efficiency is 75.8%; the obtained Ca-rich leaching solution is separated by filtration and sent into the second stirring tank 6;

[0067] (2) Calcium silicate generation: sodium silicate is added to the second stirring tank 6 at a molar ratio of Ca / Si=1, and the Ca-rich leaching solution obtained in step (1) is fully stirred and mixed, reacted for 30min, and 61.42g of solid product calcium silicate is generated;

[0068] (3) CO2 absorption: 1L of 1mol / L sodium hydroxide solution is added to the bubbling reactor 8, and pure CO2 gas is introduced into the bubbling reactor 8 from the bottom gas inlet end, the CO2 gas flow is 500ml / min, and the introduction time is 30min;

[0069] (4) Mineralization and carbon sequestration: the sodium carbonate solution generated by absorbing CO2 is transported to the stirring reactor 7, the solid-liquid ratio of calcium silicate and sodium carbonate solution is 60g / L, and the two are stirred and reacted in the stirring reactor 7 for 30min, the stirring speed of the stirring reactor 7 is 100r / min, and the reaction temperature is 30℃; after the reaction is completed, the calcium carbonate and silicon dioxide mixed solid is obtained by filtration and separation, and the filtrate is transported to the bubbling reactor 8 for continuous CO2 absorption; wherein,

[0070] The reaction equation is as follows:

[0071] Ca 2+ +SiO3 2- →CaSiO3(s);

[0072] CO2(g)+2NaOH(aq)→Na2CO3(aq)+H2O;

[0073] CaSi03(s) + Na2C03(aq) + H20 → CaC03(s) + Si02(s) + 2NaOH(aq);

[0074] The mixed solid was analyzed and the mass of calcium carbonate was 47.12 g. The CO2 mineralization rate was calculated to be 94.2%. The CO2 mineralization rate calculation formula is as follows:

[0075] n represents the amount of substance;

[0076] The sodium hydroxide solution used in the above experiment was cycled 5 times. The experimental results showed that after 5 cycles, the solution could still absorb about 11.2 L of CO2, and the CO2 mineralization rate was greater than 90%.

[0077] Finally, it should be noted that the above examples are used to illustrate the technical solutions of the present application, but not to limit it. Although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application. Any modification or equivalent replacement without departing from the spirit and scope of the present application should be covered within the protection scope of the claims of the present application.

Claims

1. A method for indirectly mineralizing and capturing CO2 using desulfurized gypsum, characterized in that, Includes the following steps: Ca was extracted from desulfurized gypsum by leaching with ammonium salt solution. 2+ , thus obtaining a calcium-rich leachate; Calcium silicate is generated by reacting the calcium-rich leachate with silicates. CO2 is absorbed by an alkaline solution to generate a carbonate solution; The calcium silicate is converted into calcium carbonate and an alkaline solution is generated by reacting the calcium silicate with the carbonate solution. in, The process of extracting Ca from desulfurized gypsum using ammonium salt solution 2+ The steps to obtain calcium-rich leachate include: mixing desulfurized gypsum powder with ammonium salt solution at a solid-liquid ratio of 10~50g / L, stirring at 30~60℃ to fully leach out the desulfurized gypsum, filtering, and obtaining calcium-rich leachate; The step of generating calcium silicate by reacting the calcium-rich leachate with silicate includes adding silicate to the calcium-rich leachate at a molar ratio of Ca / Si = 0.5~1.5, stirring and mixing at room temperature to generate the solid product calcium silicate. In the step of converting calcium silicate into calcium carbonate and generating an alkaline solution by reacting the calcium silicate with the carbonate solution, the solid-liquid ratio of calcium silicate to carbonate solution is 20~200g / L; the reaction temperature is 20~60℃. The desulfurized gypsum is flue gas desulfurization gypsum produced by a wet desulfurization process. The ammonium salt solution is one or more of the following: ammonium chloride solution, ammonium sulfate solution, ammonium acetate solution, ammonium nitrate solution, and ammonium phosphate solution; The silicate is one or more of lithium silicate, sodium silicate, and potassium silicate.

2. The method for indirectly mineralizing and capturing CO2 using desulfurized gypsum according to claim 1, characterized in that, The alkaline solution generated by the reaction of the calcium silicate with the carbonate solution is used to supply the reaction in which CO2 is absorbed by the alkaline solution.

3. The method for indirectly mineralizing and capturing CO2 using desulfurized gypsum according to claim 1, characterized in that, A desulfurized gypsum leaching device is used to leach Ca from the desulfurized gypsum using an ammonium salt solution. 2+ A calcium-rich leachate is obtained; a calcium silicate generating device is used to react the calcium-rich leachate with silicates to generate calcium silicate; a CO2 absorption device is used to absorb CO2 through alkaline solution to generate a carbonate solution; a calcium carbonate generating device is used to react the calcium silicate with the carbonate solution to convert calcium silicate into calcium carbonate and regenerate the alkaline solution.

4. The method for indirectly mineralizing and capturing CO2 using desulfurized gypsum according to claim 3, characterized in that, The desulfurized gypsum leaching device includes a drying device (1), a crusher (2), a first stirring tank (4), and an ammonium salt solution supply device (3). The drying device (1) is used to input desulfurized gypsum and perform drying treatment, and output the dried desulfurized gypsum; the crusher (2) is used to input the dried desulfurized gypsum and perform crushing treatment, and output desulfurized gypsum dry powder with a particle size that meets the preset requirements; the first mixing tank (4) is provided with a liquid inlet, a feed inlet, a liquid outlet and a discharge outlet; the feed inlet of the first mixing tank (4) is used to input the desulfurized gypsum dry powder; the liquid inlet of the first mixing tank (4) is connected to the ammonium salt solution supply device (3) and is used to input the ammonium salt solution; the liquid outlet of the first mixing tank (4) is used to output the calcium-rich leachate; the discharge outlet of the first mixing tank (4) is used to output the residual material.

5. The method for indirectly mineralizing and capturing CO2 using desulfurized gypsum according to claim 3, characterized in that, The calcium silicate generating device includes a second stirring tank (6) and a silicate supply device (5). The second stirring tank (6) is provided with a liquid inlet, a feed inlet, a liquid outlet, and a discharge outlet; the liquid inlet of the second stirring tank (6) is used to input calcium-rich leachate, the feed inlet of the second stirring tank (6) is connected to the silicate supply device (5) and is used to input silicate; the liquid outlet of the second stirring tank (6) is used to output waste liquid; the discharge outlet of the second stirring tank (6) is used to output calcium silicate.

6. The method for indirectly mineralizing and capturing CO2 using desulfurized gypsum according to claim 3, characterized in that, The CO2 absorption device includes a bubbling reactor (8); The bottom of the bubbling reactor (8) is provided with a liquid output end and a CO2 inlet end, and the top is provided with an alkali input end and a CO2 outlet end. The liquid output end is used to output carbonate solution, the CO2 inlet end is used to input CO2, the alkali input end is used to input alkali solution, and the CO2 outlet end is used to output the remaining CO2 after the reaction.

7. A method for indirectly mineralizing and capturing CO2 using desulfurized gypsum according to claim 3, characterized in that, The calcium carbonate generating device includes a stirred reactor (7). The stirred reactor (7) is provided with a feed inlet, a liquid inlet, a discharge outlet and a liquid outlet; the liquid inlet of the stirred reactor (7) is used to input carbonate solution, the feed inlet of the stirred reactor (7) is used to input calcium silicate, the discharge outlet of the stirred reactor (7) is used to output solid product, and the liquid outlet of the stirred reactor (7) is used to output alkaline solution. The solid products include calcium carbonate and silicon dioxide.

8. A method for indirectly mineralizing and capturing CO2 using desulfurized gypsum according to claim 4, characterized in that, The first mixing tank (4) is equipped with an ammonia recovery and introduction device (13); The ammonia recovery and introduction device (13) is used to prevent ammonia from escaping from the ammonium salt solution during gypsum leaching or conversion, and to avoid NH4 in the solution. + The solubility decreases.

9. A method for indirectly mineralizing and capturing CO2 using desulfurized gypsum according to claim 5, characterized in that, The second mixing tank (6) is equipped with an ammonia recovery and introduction device (13); The ammonia recovery and introduction device (13) is used to prevent ammonia from escaping from the ammonium salt solution during gypsum leaching or conversion, and to avoid NH4 in the solution. + The solubility decreases.

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