System and method for capturing CO2 by full oxygen combustion in cement kilns and co-producing high-activity auxiliary cementitious materials

Abstract

The present invention discloses a system and method for capturing CO2 through full oxygen combustion in a cement kiln and producing high-activity auxiliary cementitious materials in parallel. The system comprises a cement calcining main system, a full oxygen combustion carbon enrichment subsystem, and a flue gas CO2 carbonization system for producing high-activity auxiliary cementitious materials. The flue gas CO2 carbonization system comprises a low-pressure suspended carbonization bed system, a bag dust collector, and an induced draft fan. The full oxygen combustion carbon enrichment subsystem enriches CO2, and the CO2-rich flue gas and aqueous solution are sprayed into the low-pressure suspended carbonization bed system to form a liquid film on the surface of the material. The CO2 in the CO2-rich flue gas dissolves in the liquid film and reacts with the material to form a carbonization reaction. The powder collected by the bag dust collector can be returned to the low-pressure suspended carbonization bed system for cyclic carbonization, and high-activity auxiliary cementitious materials can also be directly obtained. The present invention achieves CO2 enrichment while improving the carbonization rate of auxiliary cementitious materials and reducing carbon emissions.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon emission reduction, and in particular to a system and method for capturing CO2 by full oxygen combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material. Background Art

[0002] As the world's primary energy source, fossil fuel consumption generates significant CO2 emissions, making it a significant contributor to the greenhouse effect. my country's abundance of coal, lack of oil, and limited natural gas make it difficult to change the proportion of coal in its primary energy mix. Cement production consumes vast quantities of natural resources and emits significant amounts of carbon dioxide. The cement industry is the third-largest source of carbon dioxide emissions in my country.

[0003] Oxyfuel combustion, based on existing industrial furnace systems, replaces combustion air with high-purity oxygen. Flue gas recirculation regulates the furnace's flow rate and heat transfer characteristics, resulting in flue gas with a CO2 concentration of up to 80% by volume. This allows for the permanent storage or resource utilization of CO2 at a relatively low cost after capture and purification, enabling large-scale industrial CO2 enrichment and emission reduction. Existing analysis shows that compared to other carbon capture methods, oxyfuel combustion technology offers advantages in terms of investment cost, operating cost, CO2 emission reduction costs, scalability, and compatibility with existing technologies.

[0004] To reduce carbon emissions from cement production, developing new carbonizable low-calcium, low-carbon cement varieties is a key approach. Ordinary Portland cement is primarily made from limestone. Producing one ton of ordinary Portland cement clinker consumes approximately 1.2 tons of limestone, generating approximately 500 kg of CO₂ emissions, accounting for approximately 60% of total carbon emissions from cement production. Developing new carbonizable cement varieties not only reduces calcium carbonate raw material consumption but also captures some CO₂ during the cement carbonation process. However, the primary application of carbonizable low-carbon cement in the concrete products industry severely restricts its widespread adoption. Therefore, if new carbonizable low-carbon clinker can be prepared into a highly active auxiliary cementing material and incorporated into cement and concrete, resulting in carbon-negative cement and concrete, the application scope of this new carbonizable low-carbon cement will be expanded, potentially becoming an effective path to reducing carbon emissions in the cement industry.

[0005] At present, most of the reports on carbonizable low-calcium and low-carbon cement are still in the laboratory research stage. In the Low-CO2 synthetic SCMs published in the International Cement Review magazine by Solida Technologies, USA, it is mentioned that low-carbon clinker mainly composed of carbonizable minerals is used to introduce industrial tail gas containing carbon dioxide into the slurry or semi-wet state to prepare SCM materials. The low-carbon clinker used is mainly CS and C3S2. These two minerals basically do not react with water for hydration, but can react with carbon dioxide to form calcite and amorphous silica. Solida's literature mentioned that the SCM it prepared contains a large amount of calcite products. However, the GB175-2021 "General Portland Cement" standard has clear requirements for cement loss on ignition. If the SCM content is 30%, sufficient carbonization can form about 15% calcite. Since PⅡ type silicate cement requires limestone content ≤5%, silicate cement (PI and PⅡ) requires loss on ignition less than 3.0% and 3.5% respectively, and ordinary silicate cement requires PO loss on ignition ≤5.0%, and the GB / T1596-2017 "Fly ash in cement and concrete" standard requires loss on ignition as an admixture ≤8.0%, this seriously limits the range of content of SCM materials prepared after full carbonization.

[0006] Low-carbon cement has broad application prospects in the field of carbon emission reduction. There are no reports on industrial-grade carbonization methods and carbonization systems for low-carbon cement. At present, relatively more research is on the carbonization of steel slag. Chinese Patent Publication No. CN113072311A discloses a steel slag auxiliary cementitious material and its preparation method and application. It mentions the use of industrial tail gas for carbonizing steel slag powder, and the introduction of industrial tail gas containing a carbon dioxide concentration of 20% during the grinding process. However, due to the limited volume of the grinding equipment, the residence time of the flue gas in the mill is relatively short. It is difficult to fully carbonize the steel slag by only carbonization reaction inside the mill, and the carbonization process is uncontrollable. Chinese Patent Publication No. CN214571715U discloses a heating and pressurizing device for carbonizing steel slag with tailings soil test blocks. By controlling the temperature and carbon dioxide gas pressure, the carbonization rate is significantly improved, which greatly accelerates the reaction process and improves the comprehensive utilization of steel slag and carbon dioxide. However, since the pressurization system is limited by the volume of the pressure vessel and the feeding method, this pressurized carbonization method is difficult to scale up industrially and is difficult to produce continuously.

[0007] In summary, the problems existing in the prior art are:

[0008] (1) Under air combustion, the CO2 concentration in the flue gas at the end of the cement kiln is relatively low (25% to 30%), which is not conducive to the resource utilization of CO2 in the flue gas.

[0009] (2) Low-calcium low-carbon cement can reduce the proportion of carbonates and reduce carbon emissions, but if it is not carbonized to increase its activity, its application range will be relatively narrow.

[0010] (3) The existing pressurized carbonization method is difficult to meet the needs of large-scale production and continuous operation of the production process.

[0011] (4) The existing in-mill carbonization method has a short reaction residence time, incomplete carbonization reaction, uncontrollable carbonization process, low activity of the carbonized material, and cannot fully capture flue gas CO2.

[0012] Therefore, under the global carbon emission reduction situation, there is an urgent need to develop a new process method that is suitable for industrial-scale continuous production, conducive to carbon capture, low raw material carbon emissions, high carbonization rate, and high activity of auxiliary cementitious materials after carbonization. Summary of the Invention

[0013] In order to solve the problems existing in the prior art, the present invention provides a system and method for capturing CO2 through full oxygen combustion in a cement kiln and co-producing highly active auxiliary cementitious materials, which achieves CO2 enrichment while improving the carbonization rate of the auxiliary cementitious materials, thereby reducing carbon emissions.

[0014] The present invention is achieved as follows: a system for capturing CO2 by full oxygen combustion in a cement kiln and producing high-activity auxiliary cementitious materials in parallel, comprising a cement calcining main system and a full oxygen combustion carbon enrichment subsystem, wherein the cement calcining main system comprises a main preheater, a main decomposition furnace, a kiln tail smoke chamber, a rotary kiln and a cooler connected in sequence; the full oxygen combustion carbon enrichment subsystem comprises a carbon enrichment furnace, a sub-preheater, a sub-high-temperature fan and a circulation fan, the penultimate sub-cyclone discharge pipe of the sub-preheater is connected to the raw material feeding pipe of the carbon enrichment furnace, the last sub-cyclone discharge pipe of the sub-preheater is connected to the kiln tail smoke chamber of the cement calcining main system, a fuel inlet, an industrial oxygen and a circulating flue gas inlet are provided at the bottom of the carbon enrichment furnace, the sub-high-temperature fan is provided on the top outlet air duct of the sub-preheater, the flue gas outlet of the sub-high-temperature fan is connected to the circulation fan, and the flue gas outlet of the circulation fan is connected to the industrial oxygen and circulating flue gas inlet of the carbon enrichment furnace;

[0015] It also includes a flue gas CO2 carbonization system for producing high-activity auxiliary gelling materials, the flue gas CO2 carbonization system for producing high-activity auxiliary gelling materials includes a low-pressure suspended carbonization bed system, a bag dust collector and an induced draft fan, the low-pressure suspended carbonization bed system includes an air duct, a suspended carbonization bed and a water spray system, the air duct is located below the suspended carbonization bed, the bottom of the air duct is the flue gas inlet, the flue gas outlet of the sub-high-temperature fan is connected to the flue gas inlet of the air duct through a dust collector, and the material inlet of the low-pressure suspended carbonization bed system is arranged on the air duct or the suspended carbonization bed , so that the powdered material moves upward under the drive of the flue gas, the top of the air duct is connected to the bottom of the suspended carbonization bed, and a spray pipe is provided at the connection part, so that the CO2-rich flue gas discharged from the high-temperature blower and after dust removal is sprayed upward into the suspended carbonization bed; a plurality of spray guns are provided at the lower part of the suspended carbonization bed and located above the spray pipe, and the outlet of the water spray system is connected to the inlet of the spray gun, so that the aqueous solution is sprayed into the suspended carbonization bed in the form of droplets, and the water vapor in the flue gas in the suspended carbonization bed forms a water vapor-water droplet critical saturation state, and a liquid film is formed on the surface of the material;

[0016] The outlet of the suspended carbonization bed is connected to the flue gas inlet of the bag dust collector; the material outlet of the bag dust collector is connected to the finished product of the high-activity auxiliary gelling material, or is respectively connected to the finished product of the high-activity auxiliary gelling material and the material inlet of the low-pressure suspended carbonization bed system, and the flue gas outlet of the bag dust collector is connected to the inlet of the induced draft fan.

[0017] In the above technical solution, preferably, the suspended carbonization bed includes a sparging pipe, a carbonization bed cone and a carbonization bed column connected in sequence from bottom to top; the sparging pipe is a vertical pipe, and a guide device for evenly distributing the flue gas is provided inside the sparging pipe.

[0018] In the above technical solution, it is further preferred that an ultrasonic generator is provided at the vertebral body of the carbonization bed.

[0019] In the above technical solution, preferably, a secondary temperature-controlled mixing chamber is provided between the suspended carbonization bed and the bag dust collector, and the secondary temperature-controlled mixing chamber is used to increase the temperature of the flue gas exiting the suspended carbonization bed and reduce the humidity of the flue gas; the secondary temperature-controlled mixing chamber has inlet one, inlet two and an outlet, the top outlet of the suspended carbonization bed is connected to inlet one of the secondary temperature-controlled mixing chamber, the flue gas outlet of the sub-high-temperature fan is connected to inlet two of the secondary temperature-controlled mixing chamber through the dust collector, and the outlet of the secondary temperature-controlled mixing chamber is connected to the flue gas inlet of the bag dust collector.

[0020] In the above technical solution, it is further preferred that a temperature measuring device is provided on the outlet pipe of the secondary temperature-controlled mixing chamber.

[0021] In the above technical solution, it is further preferred that a powder selection and separation device is arranged between the secondary temperature-controlled mixing chamber and the bag dust collector, the outlet of the secondary temperature-controlled mixing chamber is connected to the flue gas inlet of the powder selection and separation device, the bottom material outlet of the powder selection and separation device is connected to the material inlet of the low-pressure suspended carbonization bed system, and the top flue gas outlet of the powder selection and separation device is connected to the flue gas inlet of the bag dust collector.

[0022] In the above technical solution, preferably, the powder selection and separation device is a powder selector or a cyclone, which is used to separate coarse powder and fine powder in the material.

[0023] In the above technical solution, preferably, an air lock valve and a material distribution valve are sequentially provided on the material pipe of the bottom material outlet of the powder selection and separation device, and the bottom material outlet of the powder selection and separation device is also connected to the finished product of high-activity auxiliary cementitious material through the material distribution valve, so that the coarse powder exiting the powder selection and separation device can enter the suspended carbonization bed and the finished product of high-activity auxiliary cementitious material respectively.

[0024] In the above technical solution, preferably, a vertically placed filter bag is provided in the bag dust collector, and a compressed air blowing device for regularly cleaning powder cakes on the surface of the filter bag is also provided in the bag dust collector.

[0025] A method for capturing CO2 through oxyfuel combustion in a cement kiln and producing a high-activity auxiliary cementitious material in parallel, wherein the cement calcination main system and the oxyfuel combustion carbon enrichment subsystem are operated in parallel. During the preheating and pre-decomposition phase, the raw meal flow paths are parallel and non-intersecting. During the clinker calcination phase, the two streams of raw meal decomposed by the cement calcination main system and the oxyfuel combustion carbon enrichment subsystem are fed into a rotary kiln for calcination to produce cement clinker.

[0026] Among them, in the full oxygen combustion carbon enrichment subsystem, a part of the raw meal is fed into the sub-preheater, and after being preheated by the sub-preheater, it is fed into the carbon enrichment furnace for pre-decomposition, and then enters the rotary kiln for calcination; the flue gas from the carbon enrichment furnace is exhausted by the sub-high temperature fan and passes through the sub-preheater for heat exchange, and part of the flue gas is returned to the carbon enrichment furnace as medium-temperature circulating air; the remaining flue gas is then dust-removed and enters the flue gas CO2 carbonization system for producing high-activity auxiliary cementitious materials as CO2-rich flue gas to carbonize and prepare high-activity auxiliary cementitious materials;

[0027] Carbonization to prepare high-activity auxiliary gelling materials includes the following steps:

[0028] Suspension carbonization:

[0029] CO2-rich flue gas is introduced through the flue gas inlet of the air duct, with a temperature of 100-150°C and a CO2 concentration of ≥60%; the CO2-rich flue gas moves upward and is sprayed into the suspended carbonization bed through the spray pipe; at the same time, powdered materials with a temperature of ≤60°C and an average particle size of less than 200μm are dispersed and fed into the air duct or the suspended carbonization bed, so that the materials are suspended in the CO2-rich flue gas under the action of air flow drag; the pressure in the suspended carbonization bed is 0-3000Pa, and the average wind speed in the cross section of the suspended carbonization bed is 3-10m / s; at the same time, water or a carbonization aid aqueous solution is sprayed into the suspended carbonization bed in the form of droplets through a spray gun, so that the water vapor in the flue gas reaches a critical saturation state; the water vapor forms a liquid film on the surface of the material, and the CO2 in the flue gas dissolves in the liquid film to react with the material for carbonization;

[0030] Coarse powder circulation and finished product collection:

[0031] The flue gas from the suspended carbonization bed carries the material and enters the bag dust collector under the draft of the induced draft fan. After the material is collected, part of it returns to the low-pressure suspended carbonization bed system for cyclic carbonization, and part of it is led to the finished product of high-activity auxiliary gelling material; or, all of it is led to the finished product of high-activity auxiliary gelling material.

[0032] In the above technical solution, preferably, during the suspension carbonization process, ultrasonic vibration is added to the bottom of the suspension carbonization bed.

[0033] In the above technical solution, preferably, in the carbonization aid aqueous solution, the carbonization aid is one or a combination of any two of lignin sulfonates, polycyclic aromatic salts, water-soluble resin sulfonates, and alcohol-ammonia organic compounds.

[0034] In the above technical solution, preferably, the flue gas carrying materials out of the suspended carbonization bed first enters the secondary temperature-controlled mixing chamber to mix with part of the CO2-rich flue gas, and then enters the bag dust collector; the flue gas temperature out of the secondary temperature-controlled mixing chamber is controlled at ≥90°C.

[0035] In the above technical solution, it is further preferred that the flue gas carrying the material out of the secondary temperature-controlled mixing chamber first enters the powder selection and separation device, and the coarse powder in the material is collected and discharged from the bottom of the powder selection and separation device, part of which returns to the low-pressure suspended carbonization bed system for circulating carbonization, and part is led to the finished product of high-activity auxiliary gelling material; the fine powder is discharged from the top of the powder selection and separation device with the flue gas and enters the bag dust collector, and the flue gas passes through the filter bag with a filtration wind speed of 0.5 to 1.5 m / min, so that the fine powder forms a powder cake on the surface of the filter bag, and the CO2 in the flue gas continues to carbonize with the material during the process of passing through the powder cake, and the compressed air is regularly blown to clean the powder cake. The powder collected from the bag dust collector is carbonized micropowder material, which is led to the finished product of high-activity auxiliary gelling material.

[0036] In the above technical solution, preferably, the powdery material is one or a combination of cement clinker, alumina clinker, magnesium oxide clinker, spodumene sintered material, steel slag, slag, and recycled concrete aggregate.

[0037] The advantages and positive effects of the present invention are:

[0038] (1) The present invention sets up a low-pressure suspended carbonization bed system, realizes the fluidized mixing of gas and solid in the suspended carbonization bed, and improves the carbonization reaction rate. The low-pressure working environment in the suspended carbonization bed creates conditions for continuous production. The carbonization aid aqueous solution is sprayed into the suspended carbonization bed and then dispersed and attached to the particle surface in the form of droplets to form a liquid film. The liquid film serves as a gas-solid mass transfer bridge for the carbonization reaction, which can accelerate the carbonization rate. At the same time, water or a carbonization aid aqueous solution with a crystal form control agent is sprayed into the suspended carbonization bed, which promotes the full coverage of the particle surface by the crystal form control agent, reduces the formation of calcite, increases amorphous calcium carbonate, and improves the activity of the auxiliary cementitious material.

[0039] (2) The present invention solves the problem of condensation caused by water spraying or carbonization aid aqueous solution in the carbonization process causing the dew point of the flue gas in the suspended carbonization bed to drop by introducing the secondary temperature control of the CO2-rich flue gas from the full oxygen combustion carbon enrichment subsystem, thereby increasing the amount of water sprayed in the suspended carbonization bed, which is beneficial to further carbonization; while introducing the secondary temperature control of the CO2-rich flue gas from the full oxygen combustion carbon enrichment subsystem, the CO2 concentration is increased, which is beneficial to carbonization along the subsequent pipeline and bag dust collector; and when the bag dust collector collects dust, the fine powder is attached to the surface of the filter bag, and the fine powder can continue to be carbonized during the process of CO2 gas penetrating the filter bag.

[0040] (3) The present invention uses full oxygen combustion to enrich CO2, thereby increasing the CO2 concentration in the flue gas, accelerating the subsequent carbonization reaction, increasing the carbonization rate of the auxiliary cementitious material, and reducing the carbon emissions of the firing system.

[0041] (4) An ultrasonic generator is provided at the bottom of the suspended carbonization bed of the present invention, which reduces particle agglomeration through high-frequency acoustic vibration, thus facilitating a series of subsequent operations.

[0042] (5) The present invention returns the coarse powder to the low-pressure suspended carbonization bed system through the powder selection and separation process, thereby avoiding the problems of small specific surface area and low carbonization degree of the coarse powder, realizing cyclic carbonization, improving the carbonization rate, and reducing the CO2 emission of the calcination system. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of a system for capturing CO2 through full oxygen combustion in a cement kiln and co-producing a highly active auxiliary cementitious material, as provided in Example 1 of the present invention;

[0044] Figure 2 Schematic diagram of the positional relationship of the three phases of powdered material, liquid film and flue gas in the suspended carbonization bed of the present invention;

[0045] Figure 3 This is a schematic diagram of a system for capturing CO2 through full oxygen combustion in a cement kiln and co-producing highly active auxiliary cementitious materials, as provided in Example 2 of the present invention.

[0046] In the figure: g1 - industrial oxygen; F - fuel; R1 - raw meal entering the cement calcination main system; R2 - raw meal entering the oxyfuel combustion carbon enrichment subsystem; K - cement clinker; Q1 - CO2-rich flue gas from the air inlet duct; Q2 - low-CO2 flue gas; Q3 - CO2-rich flue gas entering the secondary temperature-controlled mixing chamber; M1 - powdered material; M2 - first-stage finished product; M3 - recycled material from the bag filter; M4 - recycled material from the powder separation device; M5 - second-stage finished product; M6 - combined finished product; A - material particles; B - liquid film; C - flue gas;

[0047] 1-Cement calcining main system; 101-First-stage main cyclone; 102-Second-stage main cyclone; 103-Third-stage main cyclone; 104-Fourth-stage main cyclone; 105-Fifth-stage main cyclone; 106-Main calciner; 107-Kiln tail smoke chamber; 108-Rotary kiln; 109-Cooler; 110-Kiln head burner; 111-Tertiary air duct; 112-Main high-temperature fan; 113-Main dust collector; 114-Main exhaust fan; 115-Chimney;

[0048] 2-Full oxygen combustion carbon enrichment subsystem; 201-First stage sub-cyclone; 202-Second stage sub-cyclone; 203-Third stage sub-cyclone; 204-Fourth stage sub-cyclone; 205-Fifth stage sub-cyclone; 206-Carbon enrichment furnace; 207-Circulating fan; 208-Sub-high temperature fan; 209-Dust collector;

[0049] 3- low-pressure suspended carbonization bed system; 301- spray pipe; 302- carbonization bed cone; 303- carbonization bed column; 304- ultrasonic generator; 305- water spray system; 306- spray gun; 307- air duct;

[0050] 4-bag dust collector; 401-filter bag;

[0051] 5- induced draft fan;

[0052] 6-secondary temperature-controlled mixing chamber; 601-temperature measuring device;

[0053] 7-powder selection and separation device; 701-air lock valve; 702-material distribution valve;

[0054] The dashed line with arrows is the direction of air flow; the solid line with arrows is the direction of material flow. DETAILED DESCRIPTION

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0056] In the description of the present invention, it should be understood that the terms "up", "down", "front", "back", "left", "right", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0057] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0058] Example 1

[0059] See also Figure 1 An embodiment of the present invention provides a system for capturing CO2 through oxyfuel combustion in a cement kiln and simultaneously producing a highly active auxiliary cementitious material. The system comprises a main cement calcination system 1, a oxyfuel combustion carbon enrichment subsystem 2, and a flue gas CO2 carbonization system for producing a highly active auxiliary cementitious material. The preheaters for the main cement calcination system 1 and the oxyfuel combustion carbon enrichment subsystem 2 can employ two to seven stages. This embodiment uses a five-stage preheater as an example.

[0060] The cement calcining main system 1 includes a main preheater, a main decomposition furnace 106, a kiln tail smoke chamber 107, a rotary kiln 108, a cooler 109, a kiln head burner 110, a tertiary air duct 111, a main high-temperature fan 112, a main dust collector 113, a main exhaust fan 114, and a chimney 115. The main preheater is a five-stage cyclone preheater. Raw material R1 entering the cement calcining main system is fed through a pipeline into the outlet duct of the second-stage main cyclone 102 for gas-solid heat exchange. Driven by the airflow, it enters the first-stage main cyclone 101. After gas-solid separation in the first-stage main cyclone 101, the material is fed from the discharge pipe of the first-stage main cyclone 101 into the outlet duct of the third-stage main cyclone 103. In this manner, it enters the second-stage main cyclone 102, the third-stage main cyclone 103, and the fourth-stage main cyclone 104 in sequence. The raw meal after gas-solid separation in the fourth-stage main cyclone 104 enters the main calciner 106, where the raw meal decomposition is completed (calcium carbonate in the raw meal is decomposed into calcium oxide). The decomposed raw meal enters the fifth-stage main cyclone 105 with the air flow, and after gas-solid separation, the raw meal is fed into the kiln tail smoke chamber 107.

[0061] The oxyfuel combustion carbon enrichment subsystem 2 includes a carbon enrichment furnace 206, a sub-preheater, a sub-high-temperature fan 208, and a circulating fan 207. The sub-preheater is also a five-stage cyclone preheater. The discharge pipe of the fourth-stage sub-cyclone 204 of the sub-preheater is connected to the raw meal feeding pipe of the carbon enrichment furnace 206. The top outlet of the carbon enrichment furnace 206 is connected to the inlet of the fifth-stage sub-cyclone 205. The discharge pipe of the fifth-stage sub-cyclone 205 is connected to the kiln tail smoke chamber 107 of the cement calcination main system 1. The bottom of the carbon enrichment furnace 206 is equipped with a fuel inlet, industrial oxygen inlet, and circulating flue gas inlet. Raw meal R2 entering the oxy-fuel combustion carbon enrichment subsystem is fed through a pipeline into the outlet duct of the second-stage sub-cyclone 202 for gas-solid heat exchange. Driven by the airflow, it then enters the first-stage sub-cyclone 201. After undergoing gas-solid separation in the first-stage sub-cyclone 201, the raw meal is fed from the discharge pipe of the first-stage sub-cyclone 201 into the outlet duct of the third-stage sub-cyclone 203. In this manner, it sequentially enters the second-stage sub-cyclone 202, the third-stage sub-cyclone 203, and the fourth-stage sub-cyclone 204. After gas-solid separation in the fourth-stage sub-cyclone 204, the raw meal enters the carbon enrichment furnace 206, where it undergoes decomposition. The decomposed raw meal then follows the airflow into the fifth-stage sub-cyclone 205. After gas-solid separation, the raw meal is fed into the kiln tail smoke chamber 107.

[0062] The raw materials from the cement calcining main system 1 and the oxy-fuel combustion carbon enrichment subsystem 2 enter the kiln tail smoke chamber 107 together, and are calcined into cement clinker in the rotary kiln 108. The high-temperature clinker is cooled in the cooler 109 and then discharged from the cement burning system.

[0063] Fuel F fed into the kiln head burner 110 burns in the rotary kiln 108, releasing heat to provide heat for clinker calcination. Fuel F fed into the main calciner 106 provides heat for raw meal decomposition. Fuel F fed into the bottom of the carbon enrichment furnace 206 burns in the presence of industrial oxygen and recycled flue gas, providing heat for raw meal decomposition in the oxyfuel carbon enrichment subsystem.

[0064] The sub-high-temperature fan 208 is installed on the top outlet air duct of the sub-preheater, and the flue gas outlet of the sub-high-temperature fan 208 is connected to the circulation fan 207, and the flue gas outlet of the circulation fan 207 is connected to the industrial oxygen g1 of the carbon enrichment furnace 206 and the circulating flue gas inlet.

[0065] The flue gas CO2 carbonization system for producing high-activity auxiliary cementitious materials includes a low-pressure suspended carbonization bed system 3, a bag dust collector 4 and an induced draft fan 5. The low-pressure suspended carbonization bed system 3 includes an air duct 307, a suspended carbonization bed and a water spraying system 305. The air duct 307 is located below the suspended carbonization bed. The bottom of the air duct 307 is a flue gas inlet. The flue gas outlet of the sub-high-temperature fan 208 is connected to the flue gas inlet of the air duct 307 through the dust collector 209. The material inlet of the low-pressure suspended carbonization bed system 3 is set in the air duct 307 or the suspended carbonization bed. In this embodiment, a material inlet is provided on the air duct 307 to allow the powdered material to move upward under the influence of the flue gas. The top of the air duct 307 is connected to the bottom of the suspended carbonization bed. The connection part is provided with a spraying pipe 301 to allow the CO2-rich flue gas that exits the sub-high-temperature fan 208 and undergoes dust removal to be sprayed upward into the suspended carbonization bed.

[0066] A plurality of spray guns 306 are provided at the lower part of the suspended carbonization bed and are located above the spray pipe 301. The outlet of the water spray system 305 is connected to the inlet of the spray gun 306, so that the aqueous solution is sprayed into the suspended carbonization bed in the form of droplets. The water vapor in the flue gas in the suspended carbonization bed forms a water vapor-water droplet critical saturation state, and a liquid film B is formed on the surface of the material particles A. Figure 2 shown.

[0067] The outlet of the suspended carbonization bed is connected to the flue gas inlet of the bag filter 4. The material outlet of the bag filter 4 is divided into two channels: one channel is connected to the finished product of the high-activity auxiliary cementitious material, and the other channel is connected to the air duct 307 or the material inlet of the suspended carbonization bed, returning the collected material to the air duct 307 or the suspended carbonization bed. In this embodiment, the material outlet of the bag filter 4 is also connected to the material inlet of the air duct 307, returning some of the material collected by the bag filter 4 to the air duct 307 for recycling and carbonization. The flue gas outlet of the bag filter 4 is connected to the inlet of the induced draft fan 5, which discharges the low-CO2 flue gas.

[0068] As a preferred embodiment, the suspended carbonization bed 3 includes a sparging pipe 301, a carbonization bed cone 302 and a carbonization bed column 303 connected in sequence from bottom to top; the sparging pipe 301 is a vertical pipe, and a guide device for evenly distributing the flue gas is provided inside the sparging pipe 301, and the guide device is a structure such as a guide plate, a grille or a guide ring.

[0069] The bag dust collector 4 is provided with a vertically placed filter bag 401 and a compressed air blowing device for regularly cleaning the powder cake on the surface of the filter bag. The flue gas passes through the filter bag 401, causing the fine powder to form a powder cake on the surface of the filter bag 401. The CO2 in the flue gas continues to carbonize with the material during the process of passing through the powder cake, and the compressed air is blown regularly to clean the powder cake.

[0070] A method for capturing CO2 through oxyfuel combustion in a cement kiln and producing a high-activity auxiliary cementitious material in parallel, wherein the cement calcination main system 1 and the oxyfuel combustion carbon enrichment subsystem 2 operate in parallel. During the preheating and pre-decomposition phase, the raw meal flow paths are parallel and non-intersecting. During the clinker calcination phase, the two streams of raw meal decomposed by the cement calcination main system 1 and the oxyfuel combustion carbon enrichment subsystem 2 are fed together into a rotary kiln 108 for calcination to produce cement clinker K.

[0071] In the oxyfuel combustion carbon enrichment subsystem 2, a portion of the raw meal is fed into the sub-preheater, preheated in the sub-preheater, and then fed into the carbon enrichment furnace 206 for pre-decomposition, and then enters the rotary kiln 108 for calcination; the flue gas from the carbon enrichment furnace 206 is exhausted by the sub-high-temperature fan 208 and passes through the sub-preheater for heat exchange, and part of the flue gas is returned to the carbon enrichment furnace 206 as medium-temperature circulating air; the remaining flue gas is then dusted by the dust collector 209 and enters the flue gas CO2 carbonization system for producing high-activity auxiliary cementitious materials as CO2-rich flue gas to carbonize and prepare high-activity auxiliary cementitious materials;

[0072] Carbonization to prepare high-activity auxiliary gelling materials includes the following steps:

[0073] Suspension carbonization:

[0074] The CO2-rich flue gas is introduced through the flue gas inlet of the air duct. The temperature of the CO2-rich flue gas Q1 entering the air duct is 100-150°C and the CO2 concentration is ≥60%. At the same time, the powder material M1 with a temperature of ≤60°C and an average particle size of less than 80μm is dispersed and fed into the air duct 307 through the spreading device. Under the action of the air flow drag, the material is suspended in the CO2-rich flue gas. The CO2-rich flue gas carries the powder material upward and is sprayed into the suspended carbonization bed through the spraying pipe 301. The pressure in the suspended carbonization bed is 0-3 000Pa, the average wind speed in the cross section of the suspended carbonization bed is 3 to 10 m / s; at the same time, water or an aqueous solution of a carbonization aid is sprayed into the suspended carbonization bed in the form of droplets through a spray gun 306, so that the water vapor in the flue gas reaches a critical saturation state (relative humidity ≥ 90%); since the surface temperature of the material is lower than the dew point temperature of the water vapor, the water vapor forms a liquid film on the surface of the material, and the liquid film provides a transmission medium in the gas-solid carbonization reaction. The CO2 in the flue gas dissolves in the liquid film to react with the material to undergo a carbonization reaction, thereby accelerating the carbonization process.

[0075] In the carbonization aid aqueous solution, the carbonization aid is one or a combination of any two of lignin sulfonates, polycyclic aromatic salts, water-soluble resin sulfonates, and alcohol-ammonia organic compounds.

[0076] Coarse powder circulation and finished product collection:

[0077] The flue gas leaving the suspended carbonization bed carries the material and enters the bag dust collector 4 under the suction of the induced draft fan 5. After the material is collected, a portion of the material is returned to the air duct 307 of the low-pressure suspended carbonization bed system 3 as the circulating material M3 exiting the bag dust collector for circulating carbonization, and a portion is led to the high-activity auxiliary cementitious material finished product as the first-stage finished product M2. The flue gas discharged from the bag dust collector 4 is low-CO2 flue gas Q2.

[0078] Example 2

[0079] See also Figure 3 An embodiment of the present invention provides a system for capturing CO2 through full oxygen combustion in a cement kiln and producing high-activity auxiliary cementitious materials in parallel, comprising a cement calcining main system 1, a full oxygen combustion carbon enrichment subsystem 2, and a flue gas CO2 carbonization system for producing high-activity auxiliary cementitious materials.

[0080] The structure of the cement calcining main system 1 and the structure of the oxyfuel combustion carbon enrichment subsystem 2 are the same as those of Example 1.

[0081] The flue gas CO2 carbonization system for producing highly active auxiliary cementitious materials includes a low-pressure suspended carbonization bed system 3, a secondary temperature-controlled mixing chamber 6, a powder selection and separation device 7, a bag dust collector 4, and an induced draft fan 5. The structure of the low-pressure suspended carbonization bed system 3 is the same as that of Example 1. Unlike Example 1, an ultrasonic generator 304 is also provided at the carbonization bed cone 302, located below the inlet of the spray gun 306.

[0082] The secondary temperature-controlled mixing chamber 6 is located between the suspended carbonization bed and the powder selection and separation device 7. The secondary temperature-controlled mixing chamber 6 is used to increase the temperature of the flue gas leaving the suspended carbonization bed and reduce the humidity of the flue gas. The secondary temperature-controlled mixing chamber 6 has an inlet 1, an inlet 2, and an outlet. The top outlet of the suspended carbonization bed is connected to the inlet 1 of the secondary temperature-controlled mixing chamber 6. The flue gas outlet of the sub-high-temperature blower 208 is connected to the inlet 2 of the secondary temperature-controlled mixing chamber 6 through the dust collector 209. The outlet of the secondary temperature-controlled mixing chamber 6 is connected to the flue gas inlet of the powder selection and separation device 7. A temperature measuring device 601 is provided on the outlet pipe of the secondary temperature-controlled mixing chamber 6. The temperature measuring device 601 is a thermocouple.

[0083] The powder selection and separation device 7 is a powder selector or cyclone used to separate coarse and fine powder from the material. A lock valve 701 and a feed valve 702 are sequentially installed on the material outlet pipe at the bottom of the powder selection and separation device 7. The feed valve 702 connects the feed inlet of the air duct 307 and the finished product of the high-activity auxiliary cementitious material, respectively, so that the coarse powder exiting the powder selection and separation device 7 can enter the suspended carbonization bed and the finished product of the high-activity auxiliary cementitious material, respectively. The top flue gas outlet of the powder selection and separation device 7 is connected to the flue gas inlet of the bag filter 4. The bag filter 4 is equipped with a vertically positioned filter bag 401 and a compressed air purge device for regularly removing powder cake from the surface of the filter bag 401. The feed outlet of the bag filter 4 is connected to the finished product of the high-activity auxiliary cementitious material, and the flue gas outlet of the bag filter 4 is connected to the inlet of the induced draft fan 5.

[0084] A method for capturing CO2 through full oxygen combustion in a cement kiln and producing high-activity auxiliary cementitious materials in parallel, wherein the cement calcination main system 1 and the full oxygen combustion carbon enrichment subsystem 2 operate in parallel. In the preheating and pre-decomposition stage, the raw meal flow paths are parallel and non-crossing. In the clinker calcination stage, the two streams of raw meal decomposed by the cement calcination main system 1 and the full oxygen combustion carbon enrichment subsystem 2 enter the rotary kiln 108 together for calcination to prepare cement clinker K.

[0085] In the oxyfuel combustion carbon enrichment subsystem 2, a portion of the raw meal is fed into the sub-preheater, preheated in the sub-preheater, and then fed into the carbon enrichment furnace 206 for pre-decomposition, and then enters the rotary kiln 108 for calcination; the flue gas from the carbon enrichment furnace 206 is exhausted by the sub-high-temperature fan 208 and passes through the sub-preheater for heat exchange, and part of the flue gas is returned to the carbon enrichment furnace 206 as medium-temperature circulating air; the remaining flue gas is then dusted by the dust collector 209 and enters the flue gas CO2 carbonization system for producing high-activity auxiliary cementitious materials as CO2-rich flue gas to carbonize and prepare high-activity auxiliary cementitious materials;

[0086] Carbonization to prepare high-activity auxiliary gelling materials includes the following steps:

[0087] Suspension carbonization:

[0088] CO2-rich flue gas is introduced through the flue gas inlet of the air duct 307. The temperature of the CO2-rich flue gas Q1 entering the air duct is 100-150°C and the CO2 concentration is ≥60%. At the same time, a powdered material M1 with a temperature of ≤60°C and an average particle size of less than 200 μm is dispersed and fed into the air duct 307 through a spreading device. The material is suspended in the CO2-rich flue gas under the drag of the air flow. The CO2-rich flue gas carries the powdered material upward and is sprayed into the suspended carbonization bed through the spraying pipe 301. The pressure in the suspended carbonization bed is 0- 3000Pa, the average wind speed in the cross section of the suspended carbonization bed is 3 to 10 m / s; at the same time, water or an aqueous solution of a carbonization aid is sprayed into the suspended carbonization bed in the form of droplets through a spray gun 306, so that the water vapor in the flue gas reaches a critical saturation state (relative humidity ≥ 90%); since the surface temperature of the material is lower than the dew point temperature of the water vapor, the water vapor condenses on the surface of the material to form a liquid film, which provides a transmission medium in the gas-solid carbonization reaction, and the CO2 in the flue gas dissolves in the liquid film to react with the material to undergo a carbonization reaction, thereby accelerating the carbonization reaction.

[0089] During the suspension carbonization process, ultrasonic vibration is added to the bottom of the suspension carbonization bed. High-frequency ultrasound can accelerate the disturbance of the material and flue gas flow at the bottom of the suspension carbonization bed, speed up the reaction, reduce particle agglomeration, promote the formation of a liquid film on the material surface, and fully cover the particle surface.

[0090] In the carbonization aid aqueous solution, the carbonization aid is one or a combination of any two of lignin sulfonates, polycyclic aromatic salts, water-soluble resin sulfonates, and alcohol-ammonia organic compounds.

[0091] Coarse powder circulation:

[0092] The water vapor in the flue gas leaving the suspended carbonization bed is close to the critical saturation state (relative humidity ≥ 90%). In order to avoid condensation in the subsequent powder selection and separation device 7 and the bag dust collector 4, a secondary temperature-controlled mixing chamber 6 is set before the powder selection and separation device 7. A part of the CO2-rich flue gas leaving the high-temperature blower and after dust removal is introduced into the secondary temperature-controlled mixing chamber 6 to increase the temperature of the flue gas leaving the suspended carbonization bed and reduce the humidity of the flue gas.

[0093] Flue gas exiting the suspended carbonization bed, at a temperature of 70-90°C, carries the material and first enters the secondary temperature-controlled mixing chamber 6, where it mixes with the CO2-rich flue gas Q3 entering the secondary temperature-controlled mixing chamber. The flue gas temperature exiting the secondary temperature-controlled mixing chamber 6 is controlled at ≥90°C before entering the powder selection and separation device 7. Coarse powder in the material is collected and discharged from the bottom of the powder selection and separation device 7, while fine powder is discharged from the top of the device along with the flue gas. The coarse powder exiting the powder selection and separation device 7 is divided into two paths by a distributor valve 702. One portion, as the circulating material M4 exiting the powder selection and separation device, is transported back through the material pipe to the air duct 307 before entering the suspended carbonization bed for recirculation and carbonization. The other portion, as the second-stage finished product M5, is directed to the finished product of the high-activity auxiliary cementitious material. The opening of the distributor valve 702 controls the circulation rate of the coarse powder in the suspended carbonization bed to prevent fully carbonized coarse powder from circulating endlessly in the suspended carbonization bed, which could cause excessive circulation load and lead to bed pressure.

[0094] Finished product collection:

[0095] The flue gas and fine powder discharged from the top of the powder selection and separation device 7 enter the bag dust collector 4 under the suction of the induced draft fan 5. The flue gas passes through the filter bag 401 with a filtration wind speed of 0.5-1.5 m / min, so that the fine powder forms a powder cake on the surface of the filter bag. The CO2 in the flue gas continues to carbonize with the material during the process of passing through the powder cake, and the compressed air is blown regularly to clean the powder cake. The powder collected from the bag dust collector is used as the first-level finished product M2, and the first-level finished product M2 and the second-level finished product M5 are used as the combined finished product M6 and are led to the high-activity auxiliary cementitious material finished product. The flue gas discharged from the bag dust collector is low-CO2 flue gas Q2.

[0096] In order to better understand the above embodiments of the present invention, they are further described below with reference to specific examples.

[0097] Example 1

[0098] This example uses low-carbon cement clinker as an example to explain in detail the process of capturing CO2 through oxy-fuel combustion in a cement kiln and co-producing highly active auxiliary cementitious materials. The details are as follows:

[0099] A portion of the cement raw meal is fed to the oxy-fuel combustion carbon enrichment subsystem for preheating and decomposition. The decomposed raw meal is then returned to the rotary kiln of the main cement calcination system for calcination to produce cement clinker. The oxy-fuel combustion carbon enrichment subsystem features a carbon enrichment furnace, fueled by pulverized coal and supported by industrial oxygen. The flue gas from the fuel combustion and the CO2 produced by the decomposition of the raw meal form a CO2-rich flue gas. This CO2-rich flue gas then passes through the flue gas CO2 carbonization system to produce a highly active auxiliary cementitious material. This carbonization reaction then occurs with low-carbon cement clinker, consuming the CO2 and carbonizing the low-carbon cement clinker to produce a highly active auxiliary cementitious material.

[0100] Cement raw meal is divided into two streams. The first stream is fed into the main preheater of the main cement calcining system, where it is preheated before entering the main calciner for decomposition and then into the rotary kiln for calcination. The second stream is fed into the sub-preheater of the oxyfuel combustion carbon enrichment subsystem, where it is preheated before entering the carbon enrichment furnace for decomposition and then into the rotary kiln for calcination. During the preheating and pre-calcining stages, the raw meal flows in parallel without crossing. During the clinker calcination stage, the two streams of decomposed raw meal are fed together into the rotary kiln for calcination to produce cement clinker.

[0101] The pulverized coal is divided into three parts. The first part is fed into the rotary kiln for calcining cement clinker; the second part is fed into the main calciner for raw meal decomposition; the third part is fed into the carbon enrichment furnace for raw meal decomposition.

[0102] In the oxyfuel combustion carbon enrichment subsystem, air is drawn from the outlet duct of the high-temperature fan, introducing circulating flue gas at 100-400°C into the carbon enrichment furnace. Pulverized coal and industrial oxygen (oxygen concentration not less than 80%) are injected into the carbon enrichment furnace, where they ignite and burn. Raw meal is fed into the carbon enrichment furnace, where it decomposes and releases CO2. The CO2 concentration of the flue gas exiting the carbon enrichment furnace is maintained at above 60% on a dry basis.

[0103] The flue gas exiting the carbon enrichment furnace is drawn by a high-temperature fan and then heat-exchanged in a preheater. A portion of the flue gas then returns to the carbon enrichment furnace as medium-temperature circulating air. The remaining flue gas, after dust removal, enters the flue gas CO2 carbonization system for producing high-activity auxiliary cementitious materials as CO2-rich flue gas, where it is carbonized to produce high-activity auxiliary cementitious materials. The CO2-rich flue gas has a temperature of 100-150°C and a CO2 concentration of ≥60%. The CO2-rich flue gas then enters the low-pressure suspended carbonization bed system 3 and the secondary temperature-controlled mixing chamber 6.

[0104] The mineral composition of low-carbon cement clinker includes α′-C2S, C4A3$, C5S2$, CS, and β-C2S. The combined content of α′-C2S and β-C2S accounts for 45% of the total mass of the low-carbon cement clinker, the combined content of C4A3$ and C5S2$ accounts for 25%, and CS accounts for 23% of the total mass. The remainder is a glassy phase. Low-carbon cement clinker is powdery, with particles ranging in size from 5 to 200 μm accounting for over 90%.

[0105] The pressure within the suspended carbonization bed is 0 to -3000 Pa. CO2-rich flue gas Q1 from the air inlet pipe passes sequentially through the air duct 307 and the spray pipe 301 at the bottom of the suspended carbonization bed before being sprayed upward into the suspended carbonization bed. The average wind speed within the suspended carbonization bed cross section is 3 to 10 m / s. The spray pipe 301 is a vertical pipe with internal guide plates to promote uniform distribution of the flue gas. At the carbonization bed cone 302, water or a carbonization aid aqueous solution from the water spray system 305 is sprayed into the suspended carbonization bed in the form of droplets via a spray gun 306. The amount of aqueous solution sprayed is adjusted to keep the water vapor content in the flue gas close to the critical saturation concentration.

[0106] The ultrasonic generator 304 at the bottom of the suspended carbonization bed is turned on. Room-temperature low-carbon cement clinker powder (≤60°C) is dispersed and fed into the air duct 307 through the spreading device and sprayed into the suspended carbonization bed driven by the CO2-rich flue gas. Under the action of the airflow drag, the material is suspended in the flue gas. Because the surface temperature of the material is lower than the water vapor dew point, water vapor condenses on the surface of the material particles A to form a liquid film B. The liquid film provides a transmission medium in the gas-solid carbonization reaction. The CO2 in the flue gas C dissolves in the liquid film B and reacts with the material to form a carbonization reaction, thereby accelerating the carbonization reaction.

[0107] The main carbonization reactions are as follows:

[0108]

[0109] In order to improve the activity, the carbonization degree is appropriate, and the carbonization rate of low-carbon cement clinker powder is 10% to 20%.

[0110] Flue gas exiting the suspended carbonization bed, with a temperature of 70-90°C, carries the material into the secondary temperature-controlled mixing chamber 6 and mixes with the CO₂-rich flue gas Q₂ entering the secondary temperature-controlled mixing chamber, maintaining the flue gas temperature at ≥90°C. The water vapor in the flue gas exiting the suspended carbonization bed approaches critical saturation (relative humidity ≥90%). To prevent condensation in the subsequent powder selection and separation device 7 and bag filter 4, a secondary temperature-controlled mixing chamber 6 is provided before the powder selection and separation device 7. A portion of the CO₂-rich flue gas is introduced into the secondary temperature-controlled mixing chamber 6, which raises the flue gas temperature and reduces its humidity.

[0111] The flue gas exiting the secondary temperature-controlled mixing chamber 6 carries the material into the powder selection and separation device 7. The coarse powder in the material is collected and discharged from the bottom of the powder selection and separation device 7. The coarse powder exiting the powder selection and separation device 7 is divided into two paths by a distribution valve 702. One part is transported back through the material pipe to the air duct 307 and then enters the suspended carbonization bed for cyclic carbonization. The other part is divided and directed to the finished product of the high-activity auxiliary cementitious material. The circulation rate of the coarse powder in the suspended carbonization bed is controlled by the opening of the distribution valve 702 to prevent the fully carbonized coarse powder from circulating in the suspended carbonization bed indefinitely, which would cause excessive circulation load and lead to bed pressure. Fine powder is discharged from the air duct at the top of the powder selection and separation device along with the flue gas.

[0112] The flue gas and fine powder discharged from the top of the powder selection and separation device 7 enter the bag dust collector 4 under the suction of the induced draft fan 5. A vertically placed filter bag 401 is set inside the bag dust collector 4. The flue gas passes through the filter bag with a filtration wind speed of 0.5 to 1.5 m / min, so that the fine powder forms a powder cake on the surface of the filter bag. The CO2 in the flue gas continues to carbonize with the material during the process of passing through the powder cake, and the compressed air is regularly blown to clean the powder cake regularly. The powder collected from the bag dust collector is a highly active auxiliary gelling material after carbonization, and the flue gas discharged from the bag dust collector is a low-CO2 flue gas Q2.

[0113] Example 2

[0114] Different from Example 1, this example uses steel slag powder as the carbonization raw material.

[0115] The mineral composition of steel slag primarily includes C2S, C4AF, f-CaO, and a ferrous magnesium solid solution, with small amounts of C3S and f-MgO. Particles with a particle size distribution of 5 to 200 μm account for over 90% of the steel slag powder.

[0116] The main carbonization reactions are as follows:

[0117]

[0118] For steel slag, the carbonization rate of f-CaO needs to be increased to address the poor stability of steel slag due to its high f-CaO content when used as an auxiliary cementitious material. By adjusting the opening of the distribution valve 702, the proportion of recycled carbonized steel slag fine powder reaches over 80%. This increases the circulation rate of the coarse powder in the low-pressure suspended carbonization bed system 3, prolongs the carbonization time, and promotes the full carbonization of f-CaO in the steel slag to CaCO3.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for capturing CO2 by full oxygen combustion in a cement kiln and producing high-activity auxiliary cementitious materials in parallel, comprising a cement calcining main system and a full oxygen combustion carbon enrichment subsystem, wherein the cement calcining main system comprises a main preheater, a main decomposition furnace, a kiln tail smoke chamber, a rotary kiln and a cooler connected in sequence; the full oxygen combustion carbon enrichment subsystem comprises a carbon enrichment furnace, a sub-preheater, a sub-high-temperature fan and a circulation fan, the penultimate sub-cyclone discharge pipe of the sub-preheater is connected to the raw meal feeding pipe of the carbon enrichment furnace, the last sub-cyclone discharge pipe of the sub-preheater is connected to the kiln tail smoke chamber of the cement calcining main system, a fuel inlet, an industrial oxygen and a circulating flue gas inlet are provided at the bottom of the carbon enrichment furnace, the sub-high-temperature fan is provided on the top outlet air duct of the sub-preheater, the flue gas outlet of the sub-high-temperature fan is connected to the circulation fan, and the flue gas outlet of the circulation fan is connected to the industrial oxygen and circulating flue gas inlet of the carbon enrichment furnace; and it is characterized in that: It also includes a flue gas CO2 carbonization system for producing high-activity auxiliary gelling materials, the flue gas CO2 carbonization system for producing high-activity auxiliary gelling materials includes a low-pressure suspended carbonization bed system, a bag dust collector and an induced draft fan, the low-pressure suspended carbonization bed system includes an air duct, a suspended carbonization bed and a water spray system, the air duct is located below the suspended carbonization bed, the bottom of the air duct is the flue gas inlet, the flue gas outlet of the sub-high-temperature fan is connected to the flue gas inlet of the air duct through a dust collector, and the material inlet of the low-pressure suspended carbonization bed system is arranged on the air duct or the suspended carbonization bed , so that the powdered material moves upward under the drive of the flue gas, the top of the air duct is connected to the bottom of the suspended carbonization bed, and a spray pipe is provided at the connection part, so that the CO2-rich flue gas discharged from the high-temperature blower and after dust removal is sprayed upward into the suspended carbonization bed; a plurality of spray guns are provided at the lower part of the suspended carbonization bed and located above the spray pipe, and the outlet of the water spray system is connected to the inlet of the spray gun, so that the aqueous solution is sprayed into the suspended carbonization bed in the form of droplets, and the water vapor in the flue gas in the suspended carbonization bed forms a water vapor-water droplet critical saturation state, and a liquid film is formed on the surface of the material; The outlet of the suspended carbonization bed is connected to the flue gas inlet of the bag dust collector; the material outlet of the bag dust collector is connected to the finished product of the high-activity auxiliary gelling material, or is respectively connected to the finished product of the high-activity auxiliary gelling material and the material inlet of the low-pressure suspended carbonization bed system, and the flue gas outlet of the bag dust collector is connected to the inlet of the induced draft fan.

2. The system for capturing CO2 by full oxygen combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material according to claim 1 is characterized by: The suspended carbonization bed includes a spray pipe, a carbonization bed cone and a carbonization bed column connected in sequence from bottom to top; the spray pipe is a vertical pipe, and a guide device for evenly distributing the flue gas is provided inside the spray pipe.

3. The system for capturing CO2 by oxyfuel combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material according to claim 2 is characterized by: An ultrasonic generator is provided at the vertebral body of the carbonization bed.

4. The system for capturing CO2 by oxyfuel combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material according to claim 1 is characterized by: A secondary temperature-controlled mixing chamber is provided between the suspended carbonization bed and the bag dust collector, and the secondary temperature-controlled mixing chamber is used to increase the temperature of the flue gas exiting the suspended carbonization bed and reduce the humidity of the flue gas; the secondary temperature-controlled mixing chamber has an inlet one, an inlet two and an outlet, the top outlet of the suspended carbonization bed is connected to the inlet one of the secondary temperature-controlled mixing chamber, the flue gas outlet of the sub-high-temperature fan is connected to the inlet two of the secondary temperature-controlled mixing chamber through the dust collector, and the outlet of the secondary temperature-controlled mixing chamber is connected to the flue gas inlet of the bag dust collector.

5. The system for capturing CO2 by oxyfuel combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material according to claim 4 is characterized by: A temperature measuring device is provided on the outlet pipe of the secondary temperature-controlled mixing chamber.

6. The system for capturing CO2 by oxyfuel combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material according to claim 4 is characterized by: A powder selection and separation device is arranged between the secondary temperature-controlled mixing chamber and the bag dust collector. The outlet of the secondary temperature-controlled mixing chamber is connected to the flue gas inlet of the powder selection and separation device. The bottom material outlet of the powder selection and separation device is connected to the material inlet of the low-pressure suspended carbonization bed system. The top flue gas outlet of the powder selection and separation device is connected to the flue gas inlet of the bag dust collector.

7. The system for capturing CO2 by oxyfuel combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material according to claim 6 is characterized by: The powder selection and separation device is a powder selector or a cyclone, which is used to separate coarse powder and fine powder in the material.

8. The system for capturing CO2 by oxyfuel combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material according to claim 6 is characterized by: An air lock valve and a material distribution valve are sequentially arranged on the material pipe at the bottom material outlet of the powder selection and separation device. The bottom material outlet of the powder selection and separation device is also connected to the finished product of the high-activity auxiliary gelling material through the material distribution valve, so that the coarse powder leaving the powder selection and separation device can enter the suspended carbonization bed and the finished product of the high-activity auxiliary gelling material respectively.

9. The system for capturing CO2 by oxyfuel combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material according to claim 1 is characterized by: The bag dust collector is provided with a vertically placed filter bag, and is also provided with a compressed air blowing device for regularly cleaning powder cakes on the surface of the filter bag.

10. A method for capturing CO2 by oxyfuel combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material using the system according to any one of claims 1 to 9, characterized in that: The cement calcination main system and the oxyfuel combustion carbon enrichment subsystem are operated in parallel. In the preheating and pre-decomposition stage, the raw meal flow paths are parallel and non-intersecting. In the clinker calcination stage, the two streams of raw meal decomposed by the cement calcination main system and the oxyfuel combustion carbon enrichment subsystem are fed into the rotary kiln for calcination to produce cement clinker. In the oxyfuel combustion carbon enrichment subsystem, a portion of the raw meal is fed into the sub-preheater, preheated in the sub-preheater, and then fed into the carbon enrichment furnace for pre-decomposition, and then enters the rotary kiln for calcination; the flue gas from the carbon enrichment furnace is exhausted by the sub-high-temperature fan, passes through the sub-preheater for heat exchange, and a portion of the flue gas returns to the carbon enrichment furnace as medium-temperature circulating air; After dust removal, the remaining flue gas enters the flue gas CO2 carbonization system for preparing high-activity auxiliary cementitious materials as CO2-rich flue gas to be carbonized to prepare high-activity auxiliary cementitious materials; Carbonization to prepare high-activity auxiliary gelling materials includes the following steps: Suspension carbonization: CO2-rich flue gas is introduced through the flue gas inlet of the air duct. The CO2-rich flue gas has a temperature of 100-150°C and a CO2 concentration of ≥60%. The CO2-rich flue gas moves upward and is sprayed into the suspended carbonization bed through the spray pipe. At the same time, powdered materials with a temperature of ≤60°C and an average particle size of less than 200μm are dispersed and fed into the air duct or the suspended carbonization bed, so that the materials are suspended in the CO2-rich flue gas under the action of airflow drag. The pressure in the suspended carbonization bed is 0 to -3000Pa, and the average wind speed in the cross section of the suspended carbonization bed is 3 to 10m / s. At the same time, water or a carbonization aid aqueous solution is sprayed into the suspended carbonization bed in the form of droplets through a spray gun, so that the water vapor in the flue gas reaches a critical saturation state. The water vapor forms a liquid film on the surface of the material, and the CO2 in the flue gas dissolves in the liquid film to react with the material to form a carbonization reaction. Coarse powder circulation and finished product collection: The flue gas from the suspended carbonization bed carries the material and enters the bag dust collector under the draft of the induced draft fan. After the material is collected, part of it returns to the low-pressure suspended carbonization bed system for cyclic carbonization, and part of it is led to the finished product of high-activity auxiliary gelling material; or, all of it is led to the finished product of high-activity auxiliary gelling material.

11. The method for capturing CO2 by full oxygen combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material according to claim 10, characterized in that: During the suspension carbonization process, ultrasonic vibration is added to the bottom of the suspension carbonization bed.

12. The method for capturing CO2 by full oxygen combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material according to claim 10, characterized in that: In the carbonization aid aqueous solution, the carbonization aid is one or a combination of any two of lignin sulfonates, polycyclic aromatic salts, water-soluble resin sulfonates, and alcohol-ammonia organic compounds.

13. The method for capturing CO2 by full oxygen combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material according to claim 10, characterized in that: The flue gas carrying the material out of the suspended carbonization bed first enters the secondary temperature-controlled mixing chamber to mix with part of the CO2-rich flue gas, and then enters the bag dust collector; the flue gas temperature out of the secondary temperature-controlled mixing chamber is controlled at ≥90℃.

14. The method for capturing CO2 by full oxygen combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material according to claim 13, characterized in that: The flue gas carrying the material out of the secondary temperature-controlled mixing chamber first enters the powder selection and separation device. The coarse powder in the material is collected and discharged from the bottom of the powder selection and separation device. Part of it returns to the low-pressure suspended carbonization bed system for circulating carbonization, and part is led to the finished product of high-activity auxiliary gelling material; the fine powder is discharged from the top of the powder selection and separation device with the flue gas and enters the bag dust collector. The flue gas passes through the filter bag with a filtration wind speed of 0.5 to 1.5 m / min, so that the fine powder forms a powder cake on the surface of the filter bag. The CO2 in the flue gas continues to carbonize with the material during the process of passing through the powder cake, and the compressed air is blown regularly to clean the powder cake. The powder collected from the bag dust collector is carbonized micropowder material, which is led to the finished product of high-activity auxiliary gelling material.

15. The method for capturing CO2 by full oxygen combustion in a cement kiln and co-producing a high-activity auxiliary cementitious material according to claim 10, characterized in that: The powdery material is one or a combination of cement clinker, alumina clinker, magnesium oxide clinker, spodumene sintered material, steel slag, slag, and recycled concrete aggregate.

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