A method and system for efficient mineralization of flue gas CO2 based on solid waste of coal-fired power plants

Abstract

This invention relates to the fields of solid waste resource utilization and carbon dioxide capture, utilization, and storage, and particularly to a method and system for efficient mineralization of CO2 from flue gas in coal-fired power plants. The system includes a dry powder feeding unit, a flue gas supply unit, a steam supply unit, and a fluidized bed reactor. The dry powder feeding unit is connected to the solid feed end of the fluidized bed reactor and is used to supply mixed dry powder materials to the fluidized bed reactor. The mixed dry powder materials include fly ash and desulfurized gypsum. The flue gas supply unit is connected to the gas inlet of the fluidized bed reactor and is used to feed CO2-containing flue gas from the desulfurized coal-fired power plant as fluidizing gas into the fluidized bed reactor. The steam supply unit is connected to the steam injection port of the fluidized bed reactor. It can directly utilize the low-concentration CO2-containing flue gas after desulfurization of coal-fired power plants, enhance gas-solid mass transfer through a dry powder fluidized bed, avoid high-energy-consuming links such as traditional CO2 capture and purification, simplify the process, and reduce the energy consumption of carbon mineralization treatment.

Description

Technical Field

[0001] This invention relates to the fields of solid waste resource utilization and carbon dioxide capture, utilization and storage technology, and in particular to a method and system for efficient mineralization of flue gas CO2 from solid waste in coal-fired power plants. Background Technology

[0002] Coal-fired power plants, while a crucial pillar of energy supply, are also major sources of concentrated emissions of bulk industrial solid wastes such as fly ash and desulfurization gypsum, as well as carbon dioxide. The large-scale stockpiling of solid wastes like fly ash and desulfurization gypsum not only occupies land but also poses environmental risks. Although some of these materials are used in building materials, their disposal capacity is unstable and their added value is low. As a major greenhouse gas, CO2 emission reduction is increasingly urgent. Traditional carbon capture and storage (CCS) technologies rely on complex amine absorption processes to purify low-concentration CO2 from flue gas, resulting in high energy consumption and costs in the capture and compression stages. In recent years, technologies for preparing building materials based on the mineralization of alkaline industrial solid wastes such as fly ash, desulfurization gypsum, and steel slag from flue gas CO2 have become a current research hotspot.

[0003] Patent CN120554037A discloses a method for preparing high-strength solid concrete bricks using mineralization curing of coal-based solid waste. This technology first prepares a gel material from pretreated coal-based solid waste, then adds water to the gel material to make a slurry, and molds the slurry into solid blocks. The solid blocks are then subjected to pre-curing and mineralization curing sequentially, finally yielding mineralized solid bricks. This patent exhibits good carbon sequestration and compressive strength, realizing the resource utilization of coal-based solid waste and the utilization and sequestration of captured CO2. However, during the carbonization curing process, the carbonated solid components generated by the reaction deposit on the surface of the molded test block, forming a coating layer that hinders internal mineralization, resulting in a long reaction time and low CO2 utilization rate. Furthermore, CO2 in the flue gas still requires chemical absorption for capture, which is costly. Patent CN120605603A discloses a system and method for deep mineralization and CO2 storage of coal-based solid waste throughout the entire process. This method uses physical methods such as ball milling, high-temperature calcination, and hydration, as well as chemical leaching reaction solution to send fly ash or a mixture of fly ash and desulfurized gypsum to a vortex mineralization reaction device. During the mineralization reaction, the ultrasonic cavitation effect is used to increase the gas-solid mass transfer efficiency, resulting in high CO2 storage and absorption efficiency. However, this method is complex, requires high-temperature calcination, which leads to high energy consumption, and requires ammonium salts and hydrochloric acid as reaction solutions, posing certain safety hazards. It is difficult to promote in coal-fired power plant scenarios.

[0004] Therefore, there is an urgent need to develop a new method that can be directly operated in power plant scenarios, utilizing raw or simply pre-treated exhaust gas and power plant solid waste to achieve efficient and low-cost synergistic resource utilization, thereby forming an economically feasible and easily promoted carbon capture and storage technology.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the general background of this disclosure and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] This invention provides a method and system for efficient mineralization of CO2 from flue gas in coal-fired power plant solid waste. It can directly utilize the low-concentration CO2-containing flue gas after desulfurization in coal-fired power plants, enhance gas-solid mass transfer through a dry powder fluidized bed, avoid high-energy-consuming links such as traditional CO2 capture and purification, simplify the process and reduce the energy consumption of carbon mineralization treatment. At the same time, fly ash and desulfurization gypsum are co-mineralized, realizing the integrated treatment of resource utilization of solid waste in coal-fired power plants and CO2 mineralization and storage in flue gas. Furthermore, the overall utilization rate of raw materials and CO2 is further improved through solid waste recycling and tail gas recycling.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a system for the efficient mineralization of CO2 from flue gas of solid waste from coal-fired power plants. The system includes a dry powder feeding unit, a flue gas supply unit, a steam supply unit, and a fluidized bed reactor. The dry powder feeding unit is connected to the solid feed end of the fluidized bed reactor and is used to supply mixed dry powder materials to the fluidized bed reactor; the mixed dry powder materials include fly ash and desulfurized gypsum. The flue gas supply unit is connected to the gas inlet of the fluidized bed reactor and is used to feed the CO2-containing flue gas after desulfurization of the coal-fired power plant into the fluidized bed reactor as fluidizing gas. The steam supply unit is connected to the steam injection port of the fluidized bed reactor and is used to introduce steam into the fluidized bed reactor. Fluidized bed reactors are used to keep mixed dry powder materials fluidized and dispersed under the action of CO2-containing flue gas, and to enable the mixed dry powder materials to undergo mineralization reactions with CO2-containing flue gas.

[0008] Furthermore, the moisture content of fly ash is ≤3%; the specific surface area of ​​desulfurized gypsum is greater than 400 m². 2 / kg; The mass ratio of fly ash to desulfurized gypsum is (70~85):(15~30); The D50 particle size of the mixed dry powder material is 10~50μm, and the D90 particle size is <100μm.

[0009] Furthermore, a polycarboxylate dispersant is added to the mixed dry powder material, with the addition amount being 0.05~0.3% of the total mass of the mixed dry powder.

[0010] Furthermore, the fluidized bed reactor comprises a conical section, a cylindrical section, and an enlarged section connected sequentially from bottom to top, with a gas-solid outlet at the top of the enlarged section; The conical section is equipped with an airflow nozzle and an annular porous distribution plate surrounding the airflow nozzle. The annular porous distribution plate is located above the airflow nozzle, and the airflow nozzle is located at the center of the conical section. The conical section is equipped with a solid feed end located between the airflow nozzle and the annular porous distribution plate; The fluidized bed reactor has multiple steam injection ports in the lower and middle parts, which are located above the annular porous distribution plate.

[0011] Furthermore, the dry powder feeding unit includes a feeding hopper, a conveying pipe, a venturi tube feeder, and a dispersing nozzle connected in sequence. The outlet of the feeding hopper is equipped with a rotary valve, and the dispersing nozzle extends into the conical section from the solid feed end.

[0012] Furthermore, the flue gas supply unit includes a first gas supply branch and a second gas supply branch. The first gas supply branch is connected to the airflow nozzle, and the second gas supply branch is connected to the annular porous distribution plate. The material ejection direction of the dispersion nozzle is consistent with the airflow ejection direction of the airflow nozzle.

[0013] Furthermore, the fluidized bed reactor also includes a heat exchange unit, which includes heat exchangers disposed on the walls of the conical and cylindrical sections along the height direction of the fluidized bed reactor.

[0014] Furthermore, the system also includes a cyclone separator and a return unit. The gas-solid outlet of the fluidized bed reactor is connected to the inlet of the cyclone separator, and the solid outlet of the cyclone separator is connected to the conical section of the fluidized bed reactor through the return unit. The return unit includes a return riser and valves installed on the return riser.

[0015] Furthermore, the system also includes a bag filter, with the gas outlet of the cyclone separator connected to the inlet of the bag filter. The bag filter is used to perform gas-solid separation on the dust-laden gas discharged from the cyclone separator. Part of the exhaust gas discharged from the bag filter is pressurized and returned to the fluidized bed reactor.

[0016] A second aspect of this invention provides a method for efficiently mineralizing CO2 from flue gas in coal-fired power plant solid waste. The method is based on the aforementioned system and includes the following steps: S1 mixes fly ash and desulfurized gypsum to obtain a mixed dry powder material; S2 introduces CO2-containing flue gas from desulfurized coal-fired power plants as fluidizing gas into the mineralization reaction zone, so that the mixed dry powder material remains fluidized and dispersed in the mineralization reaction zone; S3 introduces steam into the mineralization reaction zone, causing the mixed dry powder material to undergo a mineralization reaction with CO2-containing flue gas.

[0017] The technical solution of this invention can achieve the following technical effects: (1) The present invention can improve the single-pass utilization rate and overall utilization rate of CO2, eliminate the expensive and energy-intensive CO2 capture and purification process, reduce the cost of carbon sequestration, and have economic feasibility for large-scale engineering applications.

[0018] (2) This invention uses fly ash and desulfurized gypsum for co-mineralization, and the synergistic activation optimizes the product performance. The desulfurized gypsum not only provides a calcium source, but also its SO4 2- It can effectively disrupt the glassy network structure of fly ash and stimulate its potential hydraulic properties. The active SiO2 and Al2O3 in fly ash, together with hydration products and carbonates, form a composite cementing system, giving the final product performance far exceeding that of a single solid waste product.

[0019] (3) The dry powder fluidized bed direct mineralization process is adopted to avoid complex processes such as pulping, briquetting and mineralization. The desulfurized flue gas is creatively used as the fluidizing medium and mineralization reaction gas. The two independent processes of solid waste resource utilization and CO2 capture and storage are completed simultaneously in a single reaction device, thereby simplifying the process and reducing energy consumption.

[0020] (4) By utilizing the exothermic characteristics of the mineralization reaction, the heat of reaction is removed in time through a heat exchanger and used to preheat the steam required for intake and humidity control, so as to achieve the self-balance of the heat of the reaction system and the cascade utilization of low-grade heat energy, thereby reducing the external heating demand. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the system for efficiently mineralizing CO2 from solid waste in coal-fired power plants, according to the present invention. Figure 2 This is a cross-sectional view of a fluidized bed reactor; Attached reference numerals: 1. Moisture regulating device; 2. Grinding device; 3. Stirring device; 4. Compressed air device; 5. Feed hopper; 6. Venturi tube feeder; 7. Steam tank; 8. Fluidized bed reactor; 9. Cyclone separator; 10. Bag filter dust collector; 801. Airflow nozzle; 802. Dispersion nozzle; 803. Material circulation inlet; 804. Annular porous distribution plate; 805. Heat exchanger; 806. Steam injection port; 807. Conical section; 808. Cylindrical section; 809. Enlarged section. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] The above description is merely an overview of the technical solution of this application. In order to make the technical means of this application clearer and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below.

[0026] Example 1:

[0027] Reference Figure 1 This embodiment provides a system for the efficient mineralization of CO2 from solid waste in coal-fired power plants, including a raw material pretreatment unit, a dry powder feeding unit, a flue gas supply unit, a steam supply unit, a fluidized bed reactor 8, a cyclone separator 9, a bag filter 10, a return material unit, and a heat exchange unit.

[0028] The raw material pretreatment unit includes a moisture adjustment device 1, a grinding device 2, and a mixing device 3. Fly ash from the coal-fired power plant is moisture-adjusted by the moisture adjustment device 1 to ensure its moisture content does not exceed 3%. Desulfurized gypsum is crushed and ground by the grinding device 2 to ensure its specific surface area is greater than 400 m². 2 / kg.

[0029] Pretreated fly ash and desulfurized gypsum are fed into mixing device 3 for dry mixing, with a mass ratio of fly ash to desulfurized gypsum of (70~85):(15~30). A polycarboxylate dispersant is added during the mixing process, at a concentration of 0.05~0.3% of the total mass of the mixed dry powder, to improve mixing uniformity and dry powder flowability. The resulting mixed dry powder has a D50 particle size of 10~50 μm and a D90 particle size of less than 100 μm.

[0030] Fly ash and desulfurized gypsum are used together as raw materials for the mineralization reaction. Desulfurized gypsum provides a calcium source, while its sulfate ions promote the destruction of the glassy network structure of fly ash and the release of active components. The active SiO2 and Al2O3 in fly ash, together with the hydration products and carbonates generated during the mineralization process, form a composite cementitious system, thereby achieving synergistic mineralization of fly ash and desulfurized gypsum. Preferably, the mass ratio of fly ash to desulfurized gypsum is 80:20.

[0031] The dry powder feeding unit includes a feeding hopper 5, a conveying pipeline, a venturi tube feeder 6, and a dispersing nozzle 802. A rotary valve is installed at the outlet of the feeding hopper 5. The compressed air device 4 is connected to the conveying pipeline. The compressed air is used as the conveying carrier air to make the mixed dry powder material discharged from the feeding hopper 5 form a gas-solid two-phase flow and convey it to the venturi tube feeder 6.

[0032] The Venturi tube feeder 6 utilizes the Venturi effect formed by airflow acceleration to further accelerate and homogenize the mixed dry powder material, which is then sprayed into the fluidized bed reactor 8 by the dispersing nozzle 802, which extends into the conical section 807 of the fluidized bed reactor 8; preferably, the conveying pipeline is a wear-resistant pipeline, and the dispersing nozzle 802 is a wear-resistant alloy dispersing nozzle.

[0033] Reference Figure 2 The fluidized bed reactor 8 includes a conical section 807, a cylindrical section 808 and an enlarged section 809 connected sequentially from bottom to top. A gas-solid outlet is provided at the top of the enlarged section 809. The cross-sectional area of ​​the conical section 807 gradually decreases from top to bottom.

[0034] An airflow nozzle 801 is provided at the center of the bottom of the conical section 807, and an annular porous distribution plate 804 is provided around the airflow nozzle 801. The feed position of the mixed dry powder material is located in the lower part of the conical section 807 and above the airflow nozzle 801. The material ejection direction of the dispersing nozzle 802 is consistent with the airflow ejection direction of the airflow nozzle 801.

[0035] The flue gas supply unit is used to send the CO2-containing flue gas after desulfurization from the coal-fired power plant into the fluidized bed reactor 8. The temperature of the CO2-containing flue gas after desulfurization is 50~60℃ and the CO2 concentration is 10~20%. After being pressurized to 0.2~0.6MPa, it is divided into two streams. The flue gas supply pressure is higher than the operating pressure inside the fluidized bed reactor so that the flue gas can overcome the resistance of the pipeline and gas distribution components and enter the fluidized bed reactor.

[0036] The first stream of flue gas is injected into the fluidized bed reactor 8 through the airflow nozzle 801 located at the center of the conical section 807, forming a high-speed jet at the bottom of the reactor; the second stream of flue gas enters the fluidized bed reactor 8 through the annular porous distribution plate 804 to form a uniform fluidized airflow.

[0037] The high-speed airflow at the center shears and entrains the mixed dry powder material ejected from the dispersing nozzle 802, causing the mixed dry powder material to disperse rapidly after entering the reactor. The flue gas fed in by the annular porous distribution plate 804 is used to maintain a stable fluidized state within the reactor. Through the combined action of the high-speed jet and the uniformly distributed airflow, the fly ash and desulfurized gypsum fine particles remain in a dispersed state, increasing the contact area between CO2-containing flue gas and solid particles, enhancing gas-solid mass transfer, and reducing the adverse effects of fine powder agglomeration on the mineralization reaction.

[0038] Multiple steam injection ports 806 are provided in the lower and middle parts of the fluidized bed reactor 8. The steam injection ports 806 are connected to the steam tank 7. The steam tank 7 supplies saturated steam with a pressure of 0.1~0.3MPa into the fluidized bed reactor 8. The steam supply pressure is higher than the pressure inside the reactor at the location of the steam injection port, so that the saturated steam can enter the mineralization reaction zone through the steam injection port. The water vapor partial pressure in the reactor is controlled by adjusting the steam flow rate, preferably keeping the relative humidity of the reaction zone at about 75%.

[0039] The introduced water vapor forms a thin liquid film on the surface of fly ash and desulfurized gypsum particles, providing a reaction medium for CO2 dissolution, dissociation, and the dissolution of active components in the solid. After the active calcium, magnesium and other cations in the solid waste enter the liquid phase on the particle surface, they react with carbonate ions formed by CO2 to generate carbonate minerals. Using water vapor to regulate the reaction humidity, compared with directly adding liquid water to the fine powder material, can provide the water required for the mineralization reaction while reducing the agglomeration of particles caused by excessive local water content.

[0040] Heat exchange units are installed on the walls of the conical section 807 and cylindrical section 808 of the fluidized bed reactor 8. Each heat exchange unit includes a heat exchanger 805 arranged along the height of the fluidized bed reactor 8. In this embodiment, the heat exchanger 805 is a multi-layer annular shell-and-tube heat exchanger. The multi-layer annular shell-and-tube heat exchanger uses circulating water as the heat exchange medium to remove the reaction heat generated during the mineralization reaction, maintaining the reactor bed temperature within a suitable mineralization reaction range. The recovered reaction heat can also be used to preheat the flue gas entering the fluidized bed reactor 8 and / or for steam supply.

[0041] The gas-solid outlet at the top of the fluidized bed reactor 8 is connected to the inlet of the cyclone separator 9. The solid outlet of the cyclone separator 9 is connected to the material circulation inlet 803 of the conical section 807 of the fluidized bed reactor 8 through a return riser. A valve is installed on the return riser, preferably a mechanical seal valve.

[0042] After the gas-solid mixture discharged from the fluidized bed reactor 8 enters the cyclone separator 9, the coarser solid particles are separated and returned to the lower part of the fluidized bed reactor 8 through the return riser, so that the incompletely mineralized solid particles can participate in the mineralization reaction again. Through the continuous circulation of solid particles, the average residence time of solid materials in the mineralization system is extended, and the degree of mineralization of solid raw materials is improved.

[0043] The gas outlet of the cyclone separator 9 is connected to the inlet of the bag filter 10. The dust-laden gas discharged from the cyclone separator 9 enters the bag filter 10 for further gas-solid separation. The fine powder captured by the bag filter 10 is collected as a mineralization product.

[0044] Part of the exhaust gas discharged from the bag filter 10 is pressurized and returned to the flue gas supply unit, where it mixes with the CO2-containing flue gas from the desulfurized coal-fired power plant and is then fed back into the fluidized bed reactor 8. Preferably, the recycled exhaust gas accounts for 60-80% of the total exhaust gas discharged from the bag filter 10. Through exhaust gas recycling, CO2 that did not complete the mineralization reaction once in the fluidized bed reactor 8 is re-entered into the mineralization reaction process, thereby improving the overall utilization rate of CO2.

[0045] Example 2:

[0046] This embodiment provides a method for efficiently mineralizing CO2 in flue gas from a coal-fired power plant using the system of Embodiment 1, including the following steps.

[0047] S1. Raw material pretreatment and mixing.

[0048] The moisture content of fly ash produced by coal-fired power plants is adjusted to no more than 3%; desulfurized gypsum is crushed and ground to achieve a specific surface area greater than 400 m². 2 / kg.

[0049] The pretreated fly ash and desulfurized gypsum are dry-mixed at a mass ratio of (70~85):(15~30), preferably at a mass ratio of 80:20.

[0050] During the mixing process, 0.05-0.3% of a polycarboxylate dispersant is added to the total mass of the mixed dry powder material, so that the D50 particle size of the resulting mixed dry powder material is 10-50 μm and the D90 particle size is less than 100 μm.

[0051] S2, Conveying mixed dry powder materials.

[0052] The mixed dry powder material obtained in step S1 is stored in the feeding hopper 5 and continuously discharged through a rotary valve. Compressed air is used as the conveying air to form a gas-solid two-phase flow of the mixed dry powder material.

[0053] The gas-solid two-phase flow enters the Venturi tube feeder 6 through the conveying pipeline. After being further accelerated and homogenized under the action of the Venturi effect, it is continuously sprayed into the conical section 807 of the fluidized bed reactor 8 by the dispersing nozzle 802.

[0054] S3, flue gas supply and rapid fluidization.

[0055] The CO2-containing flue gas after desulfurization of the coal-fired power plant is used as the fluidizing gas and mineralization reaction gas. The temperature of the CO2-containing flue gas is 50~60℃ and the CO2 concentration is 10~20%. After the CO2-containing flue gas is pressurized to 0.2~0.6MPa, it is divided into the first flue gas and the second flue gas.

[0056] The first stream of flue gas is injected as primary air through the airflow nozzle 801 located at the center of the bottom of the fluidized bed reactor 8. Primary air accounts for 30-50% of the total flue gas flow, and the outlet gas velocity of the airflow nozzle 801 is 20-35 m / s.

[0057] The second flue gas, as secondary air, is sent into the fluidized bed reactor 8 through the annular porous distribution plate 804. The secondary air accounts for 50-70% of the total flue gas flow, and the total amount of primary and secondary air is 100%. The apparent gas velocity at the annular porous distribution plate 804 is 1.0-1.8 m / s.

[0058] By adjusting the flow rates of the primary and secondary air, the overall apparent gas velocity of the fluidized bed reactor 8 based on the empty tower section is made to be 2~8 m / s, so that the mixed dry powder material is kept in a rapid fluidized state.

[0059] The material ejection direction of the dispersing nozzle 802 is consistent with the airflow direction of the primary air. After the mixed dry powder material is ejected from the dispersing nozzle 802, it is rapidly dispersed by the shearing, entrainment and turbulence of the high-speed jet of the primary air. The secondary air enters the reactor uniformly through the annular porous distribution plate 804 to maintain the overall fluidization of the bed, thereby enabling the mixed dry powder material to be fully dispersed in the CO2-containing flue gas, improving the contact frequency between solid particles and CO2 and the gas-solid mass transfer efficiency.

[0060] S4, steam conditioning and mineralization reaction.

[0061] Saturated steam at a pressure of 0.1~0.3MPa is introduced into the mineralization reaction zone through multiple steam injection ports 806 located at the bottom and middle of the fluidized bed reactor 8. The relative humidity of the reaction zone is maintained at about 75% by adjusting the amount of steam.

[0062] The heat generated by the mineralization reaction is removed by the heat exchange unit, so that the mineralization reaction temperature is controlled at 70~90℃; the reactor is operated under micro-positive pressure, and the reaction pressure is gauge pressure 0~0.2MPa.

[0063] The residence time of CO2-containing flue gas in the fluidized bed reactor 8 is controlled to be 5-10 seconds, and the average residence time of the mixed dry powder material in the mineralization system is 10-30 minutes.

[0064] During the mineralization process, water vapor forms a thin liquid film on the surface of the fluidized fly ash and desulfurized gypsum particles. CO2 in the flue gas enters the thin liquid film and forms a carbonic acid system. At the same time, active calcium, magnesium and other components in fly ash and desulfurized gypsum dissolve under the action of the thin liquid film and further react with carbonate ions to form carbonate minerals.

[0065] During the mineralization reaction, desulfurized gypsum and fly ash work together. Desulfurized gypsum can provide a calcium source and promote the release of potential active components in fly ash. The active components, hydration products and carbonates in fly ash together form a complex reaction product.

[0066] Under the continuous disturbance generated by high-speed fluidization, the solid particles are in a state of motion and dispersion, which can reduce the phenomenon of mineralization products continuously depositing on the surface of unreacted particles to form a dense coating layer, and at the same time reduce the continuous agglomeration between fine powder particles, so that CO2 can continuously contact the active components in the solid particles, thereby improving the mineralization reaction rate and reaction degree.

[0067] S5, Solid Circulation.

[0068] The gas-solid mixture discharged from the top of the fluidized bed reactor 8 enters the cyclone separator 9 for gas-solid separation.

[0069] The coarser and incompletely reacted solid particles separated by the cyclone separator 9 are continuously returned to the lower part of the fluidized bed reactor 8 via the return riser and mechanical seal valve, and participate in the mineralization reaction again.

[0070] By adjusting the solid particle circulation ratio, the average residence time of the mixed dry powder material in the system is controlled, allowing unreacted solid particles to undergo multiple cycles of mineralization, thereby improving the utilization rate of active components in the solid material.

[0071] S6, Exhaust gas treatment and recirculation.

[0072] The dust-laden exhaust gas discharged from the cyclone separator 9 enters the bag filter 10, where the bag filter 10 further captures the fine powder of mineralized products in the exhaust gas.

[0073] 60-80% of the exhaust gas treated by the bag filter 10 is pressurized and returned to the flue gas supply end of the fluidized bed reactor 8. It is then mixed with the CO2-containing flue gas from the desulfurized coal-fired power plant and re-enters the fluidized bed reactor 8.

[0074] Through the synergistic effect of solid particle recycling and CO2-containing tail gas recycling, on the one hand, the incompletely reacted solid particles are reintroduced into the mineralization reaction zone, and on the other hand, the CO2 that has not been mineralized and utilized is reintroduced into the mineralization reaction, thereby improving the utilization rate of solid raw materials and the overall utilization rate of CO2 respectively.

[0075] The mineralized products collected by the bag filter 10 are dry, fine powders with a D50 particle size of 5-20 μm and a specific surface area greater than 500 m². 2 / kg, it can be used as a mineral admixture without further drying.

[0076] Although this application has been described in conjunction with specific features and embodiments, it is apparent that various modifications and combinations can be made thereto without departing from the spirit and scope of this application. Accordingly, this specification and accompanying drawings are merely exemplary illustrations of the application as defined herein, and are to be considered as covering any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from its scope. Thus, if such modifications and modifications fall within the scope of this application and its equivalents, this application intends to include such modifications and modifications.

Claims

1. A system for efficiently mineralizing CO2 from flue gas of solid waste from coal-fired power plants, characterized in that, The system includes a dry powder feeding unit, a flue gas supply unit, a steam supply unit, and a fluidized bed reactor; The dry powder feeding unit is connected to the solid feed end of the fluidized bed reactor and is used to supply mixed dry powder material to the fluidized bed reactor; the mixed dry powder material includes fly ash and desulfurized gypsum. The flue gas supply unit is connected to the gas inlet of the fluidized bed reactor and is used to feed CO2-containing flue gas from the desulfurized coal-fired power plant into the fluidized bed reactor as fluidizing gas. The steam supply unit is connected to the steam injection port of the fluidized bed reactor and is used to introduce steam into the fluidized bed reactor. The fluidized bed reactor is used to keep the mixed dry powder material fluidized and dispersed under the action of the CO2-containing flue gas, and to allow the mixed dry powder material to undergo a mineralization reaction with the CO2-containing flue gas.

2. The system according to claim 1, characterized in that, The moisture content of the fly ash is ≤3%; the specific surface area of ​​the desulfurized gypsum is greater than 400 m². 2 / kg; The mass ratio of fly ash to desulfurized gypsum is (70~85):(15~30); The D50 particle size of the mixed dry powder material is 10~50μm, and the D90 particle size is <100μm.

3. The system according to claim 2, characterized in that, The mixed dry powder material is mixed with a polycarboxylate dispersant at a concentration of 0.05-0.3% of the total mass of the mixed dry powder.

4. The system according to claim 1, characterized in that, The fluidized bed reactor comprises a conical section, a cylindrical section, and an enlarged section connected sequentially from bottom to top, with a gas-solid outlet at the top of the enlarged section; The conical section is provided with an airflow nozzle and an annular porous distribution plate surrounding the airflow nozzle. The annular porous distribution plate is located above the airflow nozzle, and the airflow nozzle is located at the center of the conical section. The conical section is provided with a solid feed end located between the airflow nozzle and the annular porous distribution plate; The fluidized bed reactor is provided with multiple steam injection ports at the bottom and middle, and the steam injection ports are located above the annular porous distribution plate.

5. The system according to claim 4, characterized in that, The dry powder feeding unit includes a feeding hopper, a conveying pipe, a Venturi tube feeder and a dispersing nozzle connected in sequence. The outlet of the feeding hopper is equipped with a rotary valve, and the dispersing nozzle extends into the conical section from the solid feed end.

6. The system according to claim 5, characterized in that, The flue gas supply unit includes a first gas supply branch and a second gas supply branch. The first gas supply branch is connected to the airflow nozzle, and the second gas supply branch is connected to the annular porous distribution plate. The material ejection direction of the dispersion nozzle is consistent with the airflow ejection direction of the airflow nozzle.

7. The system according to claim 4, characterized in that, The fluidized bed reactor further includes a heat exchange unit, which comprises heat exchangers disposed along the height direction of the fluidized bed reactor on the walls of the conical section and the cylindrical section.

8. The system according to claim 4, characterized in that, The system also includes a cyclone separator and a return unit. The gas-solid outlet of the fluidized bed reactor is connected to the inlet of the cyclone separator, and the solid outlet of the cyclone separator is connected to the conical section of the fluidized bed reactor through the return unit. The return material unit includes a return material riser and a valve installed on the return material riser.

9. The system according to claim 8, characterized in that, The system also includes a bag filter, the gas outlet of the cyclone separator is connected to the inlet of the bag filter, and the bag filter is used to perform gas-solid separation on the dust-laden gas discharged from the cyclone separator. Part of the exhaust gas discharged from the bag filter is pressurized and returned to the fluidized bed reactor.

10. A method for efficiently mineralizing CO2 from flue gas of solid waste from coal-fired power plants, characterized in that, The method, based on the system according to any one of claims 1 to 9, includes the following steps: S1 mixes fly ash and desulfurized gypsum to obtain a mixed dry powder material; S2 introduces CO2-containing flue gas from the desulfurization process of a coal-fired power plant as a fluidizing gas into the mineralization reaction zone, so that the mixed dry powder material remains fluidized and dispersed within the mineralization reaction zone; S3 introduces steam into the mineralization reaction zone, causing the mixed dry powder material to undergo a mineralization reaction with the CO2-containing flue gas.

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