Cement production process with alternative fuel full oxycombustion coupled carbon capture

Abstract

The application belongs to the technical field of carbon emission reduction in cement industry, and particularly relates to a cement production method using alternative fuel full-oxygen combustion coupled with carbon capture, wherein a smoke chamber is connected with a bypass air release system, and a two-stage cooler is connected with a raw material grinding system; waste gas discharged from a preheater enters a cooling and condensing device as clean waste gas after waste heat power generation and treatment, the cooling and condensing device is connected with a reheating device, the reheating device is connected with a carbon capture and purification device through a fan E, the reheating device is connected with a one-stage two-stage cooler, a kiln head burner and a kiln tail burner, and a fan A and a fan C of the bypass air release system through a fan F; an oxygen production system is connected with the one-stage two-stage cooler, the kiln head burner, a kiln door cover or a tertiary air pipe, respectively. The application provides a cement production method using alternative fuel full-oxygen combustion coupled with carbon capture.

Description

Technical Field

[0001] This invention belongs to the field of carbon emission reduction technology in the cement industry, and particularly relates to a cement production method that utilizes alternative fuels for full oxy-fuel combustion coupled with carbon capture. Background Technology

[0002] Existing technology: During the 14th Five-Year Plan period, the cement industry, as a resource-dependent sector, will face new challenges in carbon emission reduction. These challenges include industrial restructuring, energy conservation and emission reduction, raw material optimization, and fuel substitution; carbon neutrality measures include collaborative disposal, waste utilization, staggered production, carbon trading mechanisms, and CCUS (carbon capture, transport, utilization, and storage).

[0003] Currently, cement production processes generally employ new dry process technology, and fuels such as coal, oil, and natural gas are commonly used. Utilizing alternative fuels is an important measure for carbon emission reduction.

[0004] Research on carbon emission reduction technologies, both domestically and internationally, mainly focuses on industries such as power, coal, and steel, with relatively few reports on carbon emission reduction technologies related to the cement industry. Currently, the carbon emission reduction technologies available for the cement industry are pre-combustion CO2 capture and post-combustion CO2 capture.

[0005] However, the inventors of this application have discovered that the aforementioned prior art has at least the following technical problems: When a large amount of alternative fuel is added to a cement kiln system, due to the large particle size, low calorific value, and high moisture content of the alternative fuel, it is prone to incomplete combustion in the decomposition furnace, resulting in a low burnout rate and the generation of large amounts of CO. The usual solution is to increase the airflow of the high-temperature fan during operation, increase the excess air coefficient, and increase the furnace volume of the decomposition furnace. This leads to excessively high airflow in the preheating and pre-decomposition system, reaching 1.7-1.8 Nm³. 3 The preheater system has a high outlet temperature and large air volume, resulting in a heat consumption 80-100 kcal / kg·cl higher than that of cement production using normal fossil fuel combustion, and a large CO2 emission. A significant drawback of pre-combustion CO2 capture is that it can only separate CO2 produced by fuel combustion, while approximately 60% of the CO2 produced by calcium carbonate decomposition is emitted with the flue gas without being treated. This makes the technology less feasible for carbon emission reduction in the cement industry. The cement industry typically uses air-assisted combustion, resulting in low CO2 concentrations (20-30%), high volumetric flow rates, and the presence of large amounts of dust and N2. Using alternative fuels may lead to the emission of various pollutants, such as chlorine, sulfur, NOx, TOC, and VOCs. Subsequent desulfurization, denitrification, and VOCs removal equipment is large, requires high investment, and is economically inefficient. This also makes post-combustion CO2 capture difficult to apply, with complex systems, high equipment investment, and high operating costs.

[0006] The difficulty and significance of solving the above technical problems: Therefore, based on these issues, a cement production method using alternative fuels in oxy-fuel combustion coupled with carbon capture is proposed. This method utilizes alternative fuels in oxy-fuel combustion coupled with carbon capture technology, achieving a heat substitution rate of over 90% in cement kilns. This results in a dry basis CO2 concentration of ≥80% and a CO concentration of 4000-9000ppm in the flue gas at the preheater outlet, reducing the amount of pure oxygen used and the cost of oxygen production. It also reduces the air volume of the entire kiln tail system, lowers the heat consumption of the cement production system, and significantly reduces the investment in subsequent waste gas treatment environmental protection equipment, as well as the CO2 capture, purification, and operating costs. Summary of the Invention The purpose of this application is to provide a cement production method that utilizes alternative fuels for full oxy-fuel combustion coupled with carbon capture to solve the technical problems in the prior art. By utilizing alternative fuels for full oxy-fuel combustion coupled with carbon capture technology, the heat substitution rate of cement kilns using alternative fuels can reach more than 90%, resulting in a dry basis CO2 concentration of ≥80% and a CO concentration of 4000-9000ppm in the flue gas at the preheater outlet. This reduces the amount of pure oxygen used and the cost of oxygen production, resulting in a smaller air volume in the entire kiln tail system, lower heat consumption in the cement production system, and a significant reduction in investment in subsequent waste gas treatment environmental protection equipment as well as CO2 capture, purification, and operating costs.

[0007] The technical solution adopted in this application embodiment to solve the technical problems existing in the prior art is as follows: A cement process system utilizing alternative fuel oxy-fuel combustion coupled with carbon capture, comprising a preheater, a decomposer, a flue, a rotary kiln, and a second-stage cooler connected in sequence, wherein the flue is connected to a bypass venting system and the second-stage cooler is connected to a raw material mill system. The exhaust gas from the preheater passes through the waste heat power generation and treatment system and enters the cooling and condensing device. The cooling and condensing device is connected to the reheating device. The reheating device is connected to the carbon capture and purification device through fan E. The reheating device is connected to the first stage of the second-stage cooler, the kiln head burner and the kiln tail burner, as well as the bypass ventilation system's fans A and C through fan F. The oxygen production system is connected to the first stage of the second-stage cooler, the kiln head burner, the kiln door cover, or the tertiary air duct.

[0008] The embodiments of this application may also employ the following technical solutions: In the above-mentioned cement process system that utilizes alternative fuels for full oxygen combustion coupled with carbon capture, the waste heat power generation and exhaust gas treatment system further includes a waste heat power generation A and a humidification tower connected in parallel, which are then connected in sequence to a high-temperature fan, a dust collector A and a regenerative thermal incinerator. Waste heat power generation B and a water spraying device are connected in parallel, with one end connected to the regenerative thermal incinerator and the other end connected to the desulfurization device. The bypass ventilation system includes a quench chamber A, a dust collector B, a fan B and a quench chamber B connected in sequence. The quench chamber A is connected to the fan A, and the quench chamber B is connected to the fan C. The fan A and the fan C blow in the low-temperature, high-concentration CO2 flue gas after the exhaust fan F. The bypass ventilation system's exhaust pipe is connected to the oxygen production system and to the first stage of the two-stage cooler. The raw material grinding system includes a raw material mill and an air cooler connected in parallel. After being connected in parallel, it is sequentially connected to a dust collector C and a fan D. Part of the air from the raw material mill system goes to the second stage of the second-stage cooler as cooling air, and part goes to the chimney and is discharged into the atmosphere.

[0009] In the aforementioned cement process system utilizing alternative fuels for full oxy-fuel combustion coupled with carbon capture, the blower F is further connected to the system's leak-prone equipment, which includes a kiln head sealing device, a kiln tail sealing device, a waste heat power generation dust removal device A, and dust collectors A and B.

[0010] A portion of the high-concentration CO2 flue gas from the fan F is sent to the system's leaky equipment, replacing the air entering the system.

[0011] A cement production method utilizing alternative fuel oxy-fuel combustion coupled with carbon capture, wherein the cement production method utilizing alternative fuel oxy-fuel combustion coupled with carbon capture employs the aforementioned cement process system utilizing alternative fuel oxy-fuel combustion coupled with carbon capture, and the cement production method utilizing alternative fuel oxy-fuel combustion coupled with carbon capture includes the following steps: Step 1: Alternative fuels are fed into the rotary kiln burner and the decomposition furnace, respectively. During operation, the O2 content in the flue gas at the decomposition furnace outlet is controlled to be less than 2.5%, the CO content to be 5000-10000 ppm, and the air volume at the decomposition furnace outlet to be 1.2-1.3 Nm³. 3 / kg.cl, CO2 concentration in flue gas (dry basis) ≥80%; Step 2: The exhaust gas from the preheater, after being cleaned by the waste heat power generation and treatment process, is condensed and dehydrated by a cooling and condensing device. Then, it is heated to 35-45℃ by a reheating device. A portion of the high-concentration CO2 flue gas is drawn to the carbon capture and purification device by fan E, while the other portion is sent to the first stage of the two-stage cooler, the kiln head burner and the kiln tail burner, as well as the bypass venting system quench chambers A and B by fan F. The O2 produced by the oxygen generation system is injected into the first stage of the two-stage cooler, the kiln head burner, the kiln door cover, or the tertiary air duct.

[0012] This invention achieves alternative fuel oxy-fuel combustion coupled with carbon capture technology through low-volume, high-concentration CO2 flue gas recirculation, thereby reducing CO2 capture, purification, and operating costs.

[0013] In the aforementioned cement production method utilizing alternative fuels in oxy-fuel combustion coupled with carbon capture, the waste heat power generation and treatment process in step two further includes the following steps: waste heat power generation A is performed on the exhaust gas exiting the preheater, or the gas is cooled via a humidification tower to below 200°C. The exhaust gas then passes through a high-temperature fan and enters dust collector A for dust collection. The high-temperature fan controls the airflow and CO concentration exiting the preheater, and the dust concentration at the outlet of dust collector A is controlled at 10 mg / Nm³. 3 The gas then enters a regenerative thermal oxidizer, where CO in the exhaust gas provides some of the fuel. The high-temperature combustion of harmful VOCs controls the VOC concentration to 20 mg / Nm³. 3 The waste gas, after VOCs removal and removal of CO, is then cooled to 100℃ via waste heat power generation or a water spray device, and then desulfurized by a desulfurization unit to control SO2 emissions in the waste gas to 35 mg / Nm³. 3 the following.

[0014] The CO in the exhaust gas provides some fuel for the regenerative thermal ignition system, reducing the use of fossil fuels, and the VOCs in the exhaust gas are treated at high temperatures.

[0015] In the above-mentioned cement production method using alternative fuels for full oxygen combustion coupled with carbon capture, further, after step two, there are the following steps: bypass ventilation process: 5-30% of the kiln exhaust gas by volume is drawn from the flue gas chamber, and the 35-45℃ high-concentration CO2 flue gas obtained in step two is blown in as cooling air into the quenching chamber A to quench the bypass ventilation system flue gas, which then enters the dust collector B for dust collection. The 35-45℃ high-concentration CO2 flue gas obtained in step two is blown in again as cooling air in the quenching chamber B to quench the bypass ventilation system flue gas. After secondary cooling, the temperature of the bypass ventilation high-concentration CO2 flue gas reaches 100-150℃. The low-temperature high-concentration CO2 flue gas exiting the bypass ventilation system is mixed with the O2 produced by the oxygen production system obtained in step two and used as cooling air, which enters the first stage of the two-stage cooler.

[0016] The high-concentration CO2 flue gas at 35-45℃ obtained in step two is used as cooling air in the quench chamber and is recycled into the bypass venting system. The heat of the flue gas in the bypass venting system is also utilized for heat recovery. The exhaust gas of the bypass venting system does not need to be treated separately for environmental protection.

[0017] In the above-mentioned cement production method using alternative fuels for full oxygen combustion coupled with carbon capture, further, after step two, there are the following steps: two-stage cooler process: a front-mounted roller crusher with a temperature resistance of about 850℃ is set up, and a partition wall is set at the crusher location to separate the first stage of the cooler and the second stage of the cooler. The blower of the first stage of the cooler is supplied with O2 generated by the oxygen production system in step one, cooling air from the bypass ventilation system, and high-concentration CO2 flue gas from the exhaust fan F; the blower of the second stage of the cooler is supplied with air or a portion of the exhaust gas from the raw material grinding system fan D.

[0018] The exhaust air temperature of the cooler is 250-300℃, and the air volume is 1.0-1.3 Nm³. 3 / kg.cl, after being dried in the raw material mill system or cooled by the air cooler, it passes through the dust collector C for dust removal. The temperature of the exhaust gas from the raw material mill is 100-150℃. Part of the exhaust gas enters the second stage of cooling air to cool the clinker, and the rest is discharged into the atmosphere.

[0019] In the above-mentioned cement production method using alternative fuels for all-oxygen combustion coupled with carbon capture, further, after step two, there is the following step: Cooler waste air heat recovery and utilization process: The waste air from the cooler goes to the raw material grinding system for raw material drying or is cooled by an air cooler, and then passes through a dust collector for dust removal. Part of the waste gas enters the second stage of the two-stage cooler, and the remainder is discharged into the atmosphere.

[0020] In the aforementioned cement production method utilizing alternative fuels in oxy-fuel combustion coupled with carbon capture, furthermore, the feeding point and discharge pipe of the alternative fuel in the decomposition furnace are equipped with airlock devices to ensure that the O2 content in the exhaust gas exiting the preheater is less than 2%, the CO content is 4000-9000 ppm, the dry basis CO2 concentration in the flue gas is ≥80%, and the air volume at the preheater outlet is 1.3-1.4 Nm³. 3 / kg.cl; Preheaters or decomposition furnaces are equipped with denitrification devices to prevent NO from entering the environment. x Emissions up to 100 mg / Nm 3 the following; Alternative fuels are fed from multiple layers into the decomposition furnace. Fuels with a particle size of 3D<50mm and 2D<200mm are arranged in the middle of the decomposition furnace, while fuels with a particle size of 3D<5mm and 2D<50mm are arranged in the lower part of the decomposition furnace.

[0021] Strengthen the sealing of parts such as the feed pipe airlock, manhole, and ash removal hole by using airlock devices and fire-resistant clay to reduce air leakage points in the preheater system. Distribute alternative fuels in layers within the decomposition furnace and control their combustion in an orderly manner to prevent scale buildup in the furnace.

[0022] A cement production method that can switch between air combustion and oxy-fuel combustion, the switchable cement production method comprising the following steps: When alternative fuel air combustion method is adopted: air is sent by blower to the cooler cooling air, the kiln head and kiln tail fuel supply air, and the bypass venting system cooling air respectively; When the alternative fuel oxy-fuel combustion coupled with carbon capture method is adopted: the clean waste gas after waste heat power generation and environmental protection waste gas treatment is cooled and condensed to remove most of the moisture, resulting in high-concentration CO2 flue gas with a dry basis CO2 concentration of ≥80%. Then, it is heated to 35-45℃ by a reheater. Part of the high-concentration CO2 flue gas is blown to the carbon capture and purification device by a fan, and the other part of the high-concentration CO2 flue gas is sent to the cooling air of the cooler, the fuel supply air of the kiln head and kiln tail, the cooling air of the bypass venting system, and the air used by the system's easily leaking equipment by a fan.

[0023] When using alternative fuels in air combustion, the presence of CO reduces the airflow at the decomposer outlet, lowering the overall system's heat consumption and the investment and operating costs of waste gas treatment and environmental protection equipment. When using alternative fuels in oxy-fuel combustion coupled with carbon capture, high-concentration CO2 flue gas recirculation achieves both oxy-fuel combustion and carbon capture technology, reducing CO2 capture, purification, and operating costs; the presence of CO further reduces the airflow at the decomposer outlet, lowering the overall system's heat consumption and the investment and operating costs of waste gas treatment and environmental protection equipment. This invention allows for rapid switching between air combustion and oxy-fuel combustion. When CO2 utilization is low, air combustion mode is used; when CO2 utilization is high, oxy-fuel combustion coupled with carbon capture is employed.

[0024] One or more technical solutions provided in the embodiments of this application have at least the following beneficial effects: 1. This invention employs a full-oxygen combustion technology that combines pure oxygen and circulating flue gas to treat alternative fuels. The oxygen concentration of the mixed gas is 21% higher than that of air, which is beneficial for the combustion of low-calorific-value alternative fuels. This allows the heat substitution rate of alternative fuels in cement kilns to reach over 90%. Since there is no introduction of N2, the CO2 concentration in the flue gas can be significantly increased. The dry basis CO2 concentration of the flue gas at the preheater outlet is ≥80%, and the CO concentration is 4000-9000ppm. This reduces the amount of pure oxygen used and the cost of oxygen production, and significantly reduces the air volume at the preheater outlet, thereby reducing the system heat consumption by 80-100kcal / kg·cl. It can also significantly reduce the investment in subsequent waste gas treatment environmental protection equipment and the cost of CO2 capture, purification, and operation.

[0025] 2. The cooler adopts a two-stage pre-roller crusher cooler, which can withstand a temperature of 850℃ for a long time. The reasonable design of the sealing structure prevents the secondary and tertiary air and the residual air at the kiln head from mixing. In the all-oxygen combustion mode, the dry basis CO2 concentration of the flue gas at the kiln tail preheater outlet is guaranteed to be ≥80%. The cooler uses a mixed gas of pure oxygen and high-concentration CO2 flue gas, and high-concentration CO2 flue gas and air for zoned cooling, which are utilized separately. Even when the secondary and tertiary air volume is significantly reduced in all-oxygen combustion, the thermal efficiency of the grate cooler can still be guaranteed not to decrease.

[0026] 3. Bypass ventilation system flue gas recycling and heat recovery: After the bypass ventilation system is cooled by low-temperature high-concentration CO2 flue gas in two stages, it solves the problem of the system's harmful components circulating and causing the calcination system to form scale and blockage. The cooled high-concentration CO2 flue gas can then enter the cooler as cooling air, which saves the bypass ventilation system's desulfurization and denitrification environmental protection equipment, recovers some heat, and realizes the circulation of CO2 flue gas in the system.

[0027] 4. Equipment in the system prone to air leakage (kiln head sealing device 37, kiln tail sealing device 38, waste heat power generation A7 dust removal device, dust collector A10 and dust collector B17 dust removal device) uses high-concentration CO2 flue gas to prevent air leakage, ensuring that the dry basis CO2 concentration of the flue gas at the preheater outlet and before CO2 capture and purification is ≥80%.

[0028] 5. Reasonably control the airflow of the high-temperature fan, reduce the air volume at the outlet of the decomposition furnace by utilizing the presence of CO in the decomposition furnace, thereby reducing the heat consumption of the entire system and the investment and operating costs of the waste gas treatment environmental protection equipment.

[0029] 6. This invention can quickly switch between air combustion and full oxygen combustion modes. When the CO2 utilization is low, the air combustion mode is used, and when the CO2 utilization is high, the full oxygen combustion coupled with carbon capture is used. Attached Figure Description

[0030] The technical solutions of the embodiments of this application will be further described in detail below with reference to the accompanying drawings. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of this application. In addition, unless otherwise specified, these drawings are only intended to conceptually illustrate the structural construction described herein and are not necessarily drawn to scale.

[0031] Figure 1 A production process flow diagram provided for an embodiment of the present invention; Figure 2 Included with instruction manual Figure 1 A close-up view of the central bypass ventilation system; Figure 3 Included with instruction manual Figure 1 A magnified view of a portion of the waste heat power generation section; Figure 4 Included with instruction manual Figure 1 A magnified view of a section of the raw material mill.

[0032] Figure 5 Included with instruction manual Figure 1 A magnified view of a portion of the oxygen generation system.

[0033] Figure 6 Included with instruction manual Figure 1 A magnified view of a portion of the carbon capture section.

[0034] In the picture: In the diagram, the dashed lines with arrows indicate the airflow direction, and the solid lines with arrows indicate the material flow direction. 1. Preheater; 2. Decomposition furnace; 3. Smoke chamber; 4. Rotary kiln; 5. Kiln hood; 6. Cooler; 601. Cooler section 1; 602. Cooler section 2; 7. Waste heat power generation A; 8. Humidification tower; 9. High-temperature fan; 10. Dust collector A; 11. Regenerative thermal oxidizer; 12. Waste heat power generation B; 13. Water spray device; 14. Desulfurization device; 15. Quenching Chamber A; 16. Fan A; 17. Dust Collector B; 18. Fan B; 19. Quenching Chamber B; 20. Fan C; 21. Raw material mill; 22. Air cooler; 23. Dust collector C; 24. Fan D; 25. Chimney; 26: Denitrification device; 27: Airlock device; 28. Cooling and condensing device; 29. ​​Reheating device; 30. Fan E; 31. Carbon capture and purification device; 32. Fan F; 33. Oxygen production system; 34. Kiln head burner; 35. Tertiary air duct; 36. Kiln tail burner; 37. Kiln head sealing device; 38. Kiln tail sealing device; 39. Front roller crusher; 40. Partition wall. Detailed Implementation

[0035] Cement production methods that utilize alternative fuels in oxy-fuel combustion coupled with carbon capture include: Preheater 1, the number of preheater stages can be selected according to the requirements of raw material moisture drying. Preheater 1 is connected to decomposition furnace 2 for calcining alternative fuel. Decomposition furnace 2 is connected to smoke chamber 3. Smoke chamber 3 is connected to rotary kiln 4. Rotary kiln 4 is connected to kiln door hood 5 and two-stage cooler 6.

[0036] The decomposition furnace 2 uses alternative combustion fuel. The tertiary air entering the decomposition furnace is a mixture of high-concentration CO2 flue gas and pure oxygen, reducing the O2 content exiting the decomposition furnace. The exhaust gas at the decomposition furnace outlet contains 5000-10000 ppm CO, thereby reducing the amount of pure oxygen used and the cost of oxygen production, and reducing the exhaust gas volume at the preheater outlet to 1.3-1.4 Nm³. 3 / kg.cl, to achieve the goal of reducing system heat consumption.

[0037] The exhaust gas outlet of the preheater 1 is connected to the waste heat power generation 7. When the waste heat power generation 7 is not working, it is connected to the humidification tower 8. The cooled exhaust gas is drawn to the dust collector A10 by the high-temperature fan 9 for dust collection, and then treated by the regenerative thermal oxidizer 11 to remove harmful gases such as CO and VOCs. CO can help the regenerative thermal oxidizer 11 save fossil fuel consumption. The treated exhaust gas is then cooled again by the waste heat power generation B12 or the water spray device 13 (when the waste heat power generation 12 is not working, it enters the water spray device 13), and then enters the desulfurization device 14 for desulfurization treatment, so that the exhaust gas meets the environmental emission standards.

[0038] The desulfurization device 14 is connected to a cooling and condensing device 28 to remove most of the moisture, resulting in a flue gas dry basis CO2 concentration ≥80%. The flue gas is then heated to 35-45℃ by a reheating device 29. A portion of the high-concentration CO2 flue gas is drawn to the carbon capture and purification device 31 by a blower E30, while another portion of the high-concentration CO2 flue gas is sent to the first stage of the second-stage cooler 6, the kiln head burner 34 and the kiln tail burner 36, the bypass venting system quench chambers A15 and B19, and the equipment in the system that is prone to air leakage (kiln head sealing device 37, kiln tail sealing device 38, waste heat power generation A7 dust removal device, dust collector A10 and dust collector B17 dust removal device).

[0039] The O2 produced by the oxygen generation system 33 is injected into the kiln head burner 34, the kiln door cover 5 or the first stage of the second stage cooler 6, or the tertiary air duct 35 for use as alternative fuel combustion at the kiln head and kiln tail; one end of the tertiary air duct 35 is connected to the decomposition furnace 2, and the other end is connected to the kiln door cover 5 or the second stage cooler 6.

[0040] The smoke chamber 3 is connected to a bypass ventilation system to treat harmful components such as sulfur, chlorine, and alkali. The exhaust gas from the kiln passes through the quench chamber 15. Fan A16 blows in high-concentration CO2 flue gas at 35-45℃ into the quench chamber 15 for cooling. After dust collection by dust collector 17, the gas is drawn in by fan 18. Fan C20 blows in high-concentration CO2 flue gas at 35-45℃ into the quench chamber B19, further cooling the exhaust gas to 100-150℃. Then, the high-concentration CO2 flue gas is used as cooling air to enter the second-stage cooler 6 to cool the clinker.

[0041] The second-stage cooler 6 is supplied with O2 generated by the oxygen production system 33, low-temperature high-concentration CO2 flue gas and pure oxygen mixture discharged from the bypass venting system, and high-concentration CO2 flue gas from the reheater 29. After heat exchange with the clinker, these gases become high-temperature secondary and tertiary air for recycling. The second-stage cooler blower also supplies air or a portion of the exhaust gas from the raw material mill system blower D24.

[0042] The exhaust gas outlet of the cooler is connected to the raw material mill 21 for raw material drying. When the raw material mill 21 is not working, it is connected to the air cooler 22. The cooled exhaust gas is collected by the dust collector 23 and then passes through the fan D24. Part of it is used as cooling air to enter the second-stage cooler 6 to cool the clinker, and part of it enters the chimney 25 for discharge.

[0043] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0044] Example 1 The cement production method utilizing alternative fuel oxy-fuel combustion coupled with carbon capture includes: Alternative fuel oxy-fuel combustion technology: Alternative fuels are fed into the rotary kiln burner and the decomposer, respectively. O2 produced by the oxygen generation system 33 is injected into the kiln head burner 34 and the first stage of the secondary cooler 6. One end of the tertiary air duct 35 is connected to the decomposer 2, and the other end is connected to the upper shell of the first stage of the secondary cooler 6 for use in the combustion of alternative fuels at the kiln head and kiln tail. A portion of the high-concentration CO2 circulating flue gas enters the first stage of the secondary cooler 6, the kiln head burner 34 and the kiln tail burner 36, and the bypass venting system quench chambers A15 and B19. During operation, the O2 content in the flue gas at the outlet of the decomposer 2 is controlled to be less than 2.5%, the CO content to be 5000-10000 ppm, the dry basis CO2 concentration in the flue gas ≥80%, and the air volume at the outlet of the decomposer 2 is 1.2-1.3 Nm³. 3 / kg.cl, by using full oxygen combustion technology and the presence of CO, the amount of pure oxygen required for the combustion of alternative fuels and the air volume at the decomposition furnace outlet are reduced, while ensuring that the dry basis CO2 concentration in the flue gas is ≥80%.

[0045] Waste heat power generation and environmental exhaust gas treatment: The exhaust gas from the preheater is either used for waste heat power generation or cooled by humidification tower 8. After passing through high-temperature fan 9, the exhaust gas enters dust collector A10 for dust collection, and then enters regenerative thermal oxidizer 11. CO in the exhaust gas provides some fuel for combustion of harmful VOCs at high temperature, controlling the VOCs concentration at 20mg / Nm³. 3 Next, the waste gas, after VOCs removal and free of CO, is cooled to 100℃ again via waste heat power generation device B12 or water spray device 13, and then desulfurized by desulfurization device 14 to control SO2 emissions in the waste gas to 35mg / Nm³. 3 the following.

[0046] Carbon capture system: The desulfurization unit 14 is connected to a cooling and condensing unit 28 to remove most of the moisture, resulting in a dry basis CO2 concentration of ≥80% in the flue gas. Then, it is heated to 35-45℃ by a reheating unit 29. A portion of the high-concentration CO2 flue gas is drawn to the carbon capture and purification unit 31 by a blower E30, while another portion of the high-concentration CO2 flue gas is sent to the cooling air of the cooler, the fuel supply air at the kiln head and kiln tail, the cooling air of the bypass venting system, and the air used by the equipment in the system that is prone to air leakage by a blower F32.

[0047] Bypass venting flue gas circulation system and heat recovery: 5-30% (volume percentage) of the kiln flue gas is drawn from the flue chamber and rapidly cooled by blowing in 35-45℃ high-concentration CO2 as cooling air. After that, it enters the dust collector B17 for dust collection. Then, 35-45℃ high-concentration CO2 is blown in again to cool the flue gas to a secondary temperature of 100-150℃. It then enters the first stage of the second-stage cooler 6 as cooling air to cool the clinker. This saves on the desulfurization and denitrification environmental protection equipment of the bypass venting system, recovers some heat, and realizes the circulation of CO2 flue gas in the system.

[0048] Two-stage cooler technology: The first-stage blower of the second-stage cooler 6 introduces O2 produced by the oxygen generation system 33, a mixture of low-temperature, high-concentration CO2 flue gas and pure oxygen discharged from the bypass venting system, and high-concentration CO2 flue gas from the reheater 29. These gases exchange heat with the clinker, becoming high-temperature secondary and tertiary air for recycling. The second-stage blower of the cooler introduces air or a portion of the exhaust gas from the raw material mill system blower D24. The exhaust air outlet of the cooler is connected to the raw material mill 21 for raw material drying. When the raw material mill 21 is not working, it is connected to the air cooler 22. The cooled exhaust gas is collected by the dust collector 23 and then passes through the blower D24. Part of the exhaust gas is used as cooling air to enter the second-stage cooler 6 to cool the clinker, and the other part is discharged into the chimney 25.

[0049] The system is prone to air leakage. High-concentration CO2 circulating flue gas is blown into the equipment (kiln head sealing device 37, kiln tail sealing device 38, waste heat power generation A7 dust removal device, dust collector A10 and dust collector B17 dust removal device), so that the dry basis CO2 concentration of the flue gas at the preheater outlet and before CO2 capture and purification is ≥80%.

[0050] Example 2 The cement production method utilizing alternative fuel oxy-fuel combustion coupled with carbon capture includes: Alternative fuel oxy-fuel combustion technology: Alternative fuels are fed into the rotary kiln burner and the decomposer, respectively. O2 produced by the oxygen generation system 33 is injected into the kiln head burner 34 and the kiln hood 5. One end of the tertiary air duct 35 is connected to the decomposer 2, and the other end is connected to the kiln hood 5 for use in the combustion of alternative fuels at the kiln head and kiln tail. A portion of the high-concentration CO2 circulating flue gas enters the first stage of the secondary cooler 6, the kiln head burner 34 and the kiln tail burner 36, and the bypass venting system quench chambers A15 and B19. During operation, the O2 content in the flue gas at the outlet of the decomposer 2 is controlled to be less than 2.5%, the CO content is 5000-10000 ppm, the dry basis CO2 concentration of the flue gas is ≥80%, and the air volume at the outlet of the decomposer 2 is 1.2-1.3 Nm³. 3 / kg.cl, by using full oxygen combustion technology and the presence of CO, the amount of pure oxygen required for the combustion of alternative fuels and the air volume at the decomposition furnace outlet are reduced, while ensuring that the dry basis CO2 concentration in the flue gas is ≥80%.

[0051] Waste heat power generation and environmental exhaust gas treatment: The exhaust gas from the preheater is either used for waste heat power generation or cooled by humidification tower 8. After passing through high-temperature fan 9, the exhaust gas enters dust collector A10 for dust collection, and then enters regenerative thermal oxidizer 11. CO in the exhaust gas provides some fuel for combustion of harmful VOCs at high temperature, controlling the VOCs concentration at 20mg / Nm³. 3 The waste gas, after VOCs removal and CO removal, is cooled to 100°C again by waste heat power generation B12 or water spray device 13, and then desulfurized by desulfurization device 14 to control SO2 emissions in the waste gas to below 35mg / Nm3.

[0052] Carbon capture system: The desulfurization unit 14 is connected to a cooling and condensing unit 28 to remove most of the moisture, resulting in a dry basis CO2 concentration of ≥80% in the flue gas. Then, it is heated to 35-45℃ by a reheating unit 29. A portion of the high-concentration CO2 flue gas is drawn to the carbon capture and purification unit 31 by a blower E30, while another portion of the high-concentration CO2 flue gas is sent to the cooling air of the cooler, the fuel supply air at the kiln head and kiln tail, the cooling air of the bypass venting system, and the air used by the equipment in the system that is prone to air leakage by a blower F32.

[0053] Bypass venting flue gas circulation system and heat recovery: 5-30% (volume percentage) of the kiln flue gas is drawn from the flue chamber and rapidly cooled by blowing in 35-45℃ high-concentration CO2 as cooling air. After that, it enters the dust collector B17 for dust collection. Then, 35-45℃ high-concentration CO2 is blown in again to cool the flue gas to a secondary temperature of 100-150℃. It then enters the first stage of the second-stage cooler 6 as cooling air to cool the clinker. This saves on the desulfurization and denitrification environmental protection equipment of the bypass venting system, recovers some heat, and realizes the circulation of CO2 flue gas in the system.

[0054] Two-stage cooler technology: The low-temperature, high-concentration CO2 flue gas discharged from the bypass venting system by the first-stage blower of the two-stage cooler, as well as the high-concentration CO2 flue gas from the reheater 29, exchange heat with the clinker, thus becoming high-temperature secondary and tertiary air for recycling. The second-stage blower of the cooler also introduces air or a portion of the exhaust gas from the raw material mill system blower D24.

[0055] The exhaust gas outlet of the cooler is connected to the raw material mill 21 for raw material drying. When the raw material mill 21 is not working, it is connected to the air cooler 22. The cooled exhaust gas is collected by the dust collector 23 and then passes through the fan D24. Part of it is used as cooling air to enter the second-stage cooler 6 to cool the clinker, and part of it enters the chimney 25 for discharge.

[0056] The system is prone to air leakage. High-concentration CO2 circulating flue gas is blown into the equipment (kiln head sealing device 37, kiln tail sealing device 38, waste heat power generation A7 dust removal device, dust collector A10 and dust collector B17 dust removal device), so that the dry basis CO2 concentration of the flue gas at the preheater outlet and before CO2 capture and purification is ≥80%.

[0057] Example 3 The cement production method utilizing alternative fuel oxy-fuel combustion coupled with carbon capture includes: Alternative fuel oxy-fuel combustion technology: Alternative fuels are fed into the rotary kiln burner and the decomposition furnace respectively. O2 produced by the oxygen production system 33 is injected into the kiln head burner 34 and the kiln door hood 5 for combustion of alternative fuels at the kiln head. O2 produced by the oxygen production system 33 is injected into the tertiary air duct for combustion of alternative fuels at the kiln tail. One end of the tertiary air duct 35 is connected to the decomposition furnace 2, and the other end is connected to the upper shell of the first stage of the second-stage cooler 6. A portion of the high-concentration CO2 circulating flue gas enters the first stage of the second-stage cooler 6, the kiln head burner 34 and the kiln tail burner 36, and the bypass venting system quench chambers A15 and B19. During operation, the O2 content in the flue gas at the outlet of the decomposition furnace 2 is controlled to be less than 2.5%, the CO content to be 5000-10000 ppm, the dry basis CO2 concentration in the flue gas ≥80%, and the air volume at the outlet of the decomposition furnace 2 is 1.2-1.3 Nm³. 3 / kg.cl, by using full oxygen combustion technology and the presence of CO, the amount of pure oxygen required for the combustion of alternative fuels and the air volume at the decomposition furnace outlet are reduced, while ensuring that the dry basis CO2 concentration in the flue gas is ≥80%.

[0058] Waste heat power generation and environmental exhaust gas treatment: The exhaust gas from the preheater is either used for waste heat power generation or cooled by humidification tower 8. After passing through high-temperature fan 9, the exhaust gas enters dust collector A10 for dust collection, and then enters regenerative thermal oxidizer 11. CO in the exhaust gas provides some fuel for combustion of harmful VOCs at high temperature, controlling the VOCs concentration at 20mg / Nm³. 3Next, the waste gas, after VOCs removal and free of CO, is cooled to 100℃ again via waste heat power generation device B12 or water spray device 13, and then desulfurized by desulfurization device 14 to control SO2 emissions in the waste gas to 35mg / Nm³. 3 the following.

[0059] Carbon capture system: The desulfurization unit 14 is connected to a cooling and condensing unit 28 to remove most of the moisture, resulting in a dry basis CO2 concentration of ≥80% in the flue gas. Then, it is heated to 35-45℃ by a reheating unit 29. A portion of the high-concentration CO2 flue gas is drawn to the carbon capture and purification unit 31 by a blower E30, while another portion of the high-concentration CO2 flue gas is sent to the cooling air of the cooler, the fuel supply air at the kiln head and kiln tail, the cooling air of the bypass venting system, and the air used by the equipment in the system that is prone to air leakage by a blower F32.

[0060] Bypass venting flue gas circulation system and heat recovery: 5-30% (volume percentage) of the kiln flue gas is drawn from the flue chamber and rapidly cooled by blowing in 35-45℃ high-concentration CO2 as cooling air. After that, it enters the dust collector B17 for dust collection. Then, 35-45℃ high-concentration CO2 is blown in again to cool the flue gas to a secondary temperature of 100-150℃. It then enters the first stage of the second-stage cooler 6 as cooling air to cool the clinker. This saves on the desulfurization and denitrification environmental protection equipment of the bypass venting system, recovers some heat, and realizes the circulation of CO2 flue gas in the system.

[0061] Two-stage cooler technology: The two-stage cooler 6 uses the low-temperature, high-concentration CO2 flue gas discharged from the bypass venting system and the high-concentration CO2 flue gas from the reheater 29, which are then exchanged with the clinker to become high-temperature secondary and tertiary air for recycling. The second-stage cooler blower also introduces air or a portion of the exhaust gas from the raw material mill system blower D24.

[0062] The exhaust gas outlet of the cooler is connected to the raw material mill 21 for raw material drying. When the raw material mill 21 is not working, it is connected to the air cooler 22. The cooled exhaust gas is collected by the dust collector 23 and then passes through the fan D24. Part of it is used as cooling air to enter the second-stage cooler 6 to cool the clinker, and part of it enters the chimney 25 for discharge.

[0063] The system is prone to air leakage. High-concentration CO2 circulating flue gas is blown into the equipment (kiln head sealing device 37, kiln tail sealing device 38, waste heat power generation A7 dust removal device, dust collector A10 and dust collector B17 dust removal device), so that the dry basis CO2 concentration of the flue gas at the preheater outlet and before CO2 capture and purification is ≥80%.

[0064] Example 4 When using alternative fuel air combustion methods: Alternative fuels with a 35-55% calorific value are fed from the rotary kiln burner, while those with a 45-65% calorific value are fed from the decomposition furnace. Larger particle sizes (3D<50mm, 2D<200mm) are arranged in the middle of the decomposition furnace, while smaller particle sizes (3D<5mm, 2D<50mm) and more easily combustible fuels are arranged at the bottom. This stratified distribution of alternative fuels within the decomposition furnace allows for controlled combustion and prevents scale buildup. The high-temperature fan 9 controls the O2 content at the outlet flue gas of decomposition furnace 2 to be less than 2.5%, the CO content to be 5000-10000ppm, and the airflow at the outlet of decomposition furnace 2 to be 1.3-1.4 Nm³. 3 / kg.cl, by using the presence of CO, the air volume at the decomposition furnace outlet and NOx emissions are reduced to 300-500mg / Nm³. 3 .

[0065] Three airlock devices are installed at the feeding point of the solid alternative fuel feed into the decomposition furnace. The sealing of the feed pipe airlock device, manhole, and ash removal hole is strengthened to reduce air leakage points in the preheater system, ensuring that the O2 content in the exhaust gas from the preheater is less than 2%, the CO content is 4000-9000 ppm, and the air volume at the preheater outlet is 1.35-1.55 Nm³. 3 / kg.cl, preheaters or denitrification furnaces are equipped with denitrification devices to reduce NOx emissions to 100mg / Nm³. 3 the following.

[0066] Waste heat power generation and environmental exhaust gas treatment: The exhaust gas from the preheater is used for waste heat power generation or cooled by humidification tower 8 to below 200℃. After passing through a high-temperature fan, the exhaust gas enters dust collector A10 for dust collection. The dust concentration at the outlet of the dust collector is controlled at 10mg / Nm³. 3 The gas then enters the regenerative thermal oxidizer 11, where CO in the exhaust gas provides some of the fuel. The high-temperature combustion of harmful VOCs controls the VOC concentration to 20 mg / Nm³. 3 Next, the waste gas, after VOCs removal and free of CO, is cooled to 100℃ again by waste heat power generation or water spray device 13, and then desulfurized by desulfurization device 14 to control SO2 emissions in the waste gas to 35mg / Nm³. 3 The CO in the exhaust gas provides some fuel for the regenerative thermal ignition (RTO) incinerator 11, reducing the amount of fossil fuel used, and treating the VOCs in the exhaust gas at high temperatures.

[0067] Bypass ventilation system and heat recovery: 5-30% (by volume) of the kiln flue gas is extracted from the flue chamber and rapidly cooled by blowing in air as cooling air. The flue gas then enters a dust collector for dust collection, and is cooled a second time to 100-150℃ by blowing in air again. This cooled flue gas then enters the cooler to cool the clinker. This system utilizes the heat from the bypass ventilation system's flue gas, achieving heat recovery, and the exhaust gas from the bypass ventilation system does not require environmental exhaust gas treatment.

[0068] Waste air heat recovery and utilization from the cooler: The waste air temperature of the cooler is 250-300℃, and the air volume is 1.0-1.3 Nm³. 3 / kg.cl, after being dried in the raw material grinding system or cooled by the air cooler, and then removed by the dust collector, the temperature of the exhaust gas from the raw material grinding is 100-150℃. Part of the exhaust gas is used as cooling air to cool the clinker, and the rest is discharged into the atmosphere.

[0069] When alternative fuel oxy-fuel combustion coupled with carbon capture: Alternative fuels with a 35-55% calorific value are fed into the kiln head burner 34, while alternative fuels with a 45-65% calorific value are fed into the decomposition furnace 2. Fuels with larger particle sizes (3D<50mm, 2D<200mm) are arranged in the middle of the decomposition furnace, while easily combustible fuels with smaller particle sizes (3D<5mm, 2D<50mm) are arranged in the lower part. The alternative fuels are layered and distributed within the decomposition furnace 2, allowing for orderly combustion control and preventing scale buildup. O2 produced by the oxygen generation system 33 is injected into the kiln head burner 34, the kiln hood 5, or the first or third stage air duct 35 of the second-stage cooler 6 for use in the combustion of alternative fuels at the kiln head and tail. The high-temperature fan 9 controls the O2 content in the flue gas exiting the decomposition furnace 2 to be less than 2.5%, the CO content to be 5000-10000ppm, and the dry basis CO2 concentration to be ≥80%. The air volume at the outlet of the decomposition furnace 2 is 1.2-1.3 Nm³. 3 / kg.cl, by using the presence of CO, the air volume at the decomposition furnace outlet and NOx emissions are reduced to 300-500mg / Nm³. 3 .

[0070] Three airlock devices are installed at the feeding point of the solid alternative fuel feed into the decomposition furnace. The sealing of the airlock devices on the feed pipe, manholes, and ash removal holes is strengthened to reduce air leakage points in the preheater system, ensuring that the O2 content in the exhaust gas from the preheater is less than 2%, the CO content is 4000-9000 ppm, and the air volume at the preheater outlet is 1.3-1.4 Nm³. 3 / kg.cl, preheaters or denitrification furnaces are equipped with denitrification devices to reduce NOx emissions to 100mg / Nm³. 3 the following.

[0071] Waste heat power generation and environmental exhaust gas treatment: The exhaust gas from the preheater is used for waste heat power generation or cooled by humidification tower 8 to below 200℃. After passing through high-temperature fan 9, the exhaust gas enters dust collector A10 for dust collection. The dust concentration at the outlet of the dust collector is controlled at 10mg / Nm³. 3 The gas then enters the regenerative thermal oxidizer 11, where CO in the exhaust gas provides some of the fuel. The high-temperature combustion of harmful VOCs controls the VOC concentration to 20 mg / Nm³. 3Next, the waste gas, after VOCs removal and free of CO, is cooled to 100℃ again via waste heat power generation device B12 or water spray device 13, and then desulfurized by desulfurization device 14 to control SO2 emissions in the waste gas to 35mg / Nm³. 3 The CO in the exhaust gas provides some fuel for the regenerative thermal ignition (RTO) incinerator 11, reducing the amount of fossil fuel used, and treating the VOCs in the exhaust gas at high temperatures.

[0072] All-oxygen combustion and carbon capture system: The desulfurization unit 14 is connected to a cooling and condensing unit 28 to remove most of the moisture, resulting in a dry basis CO2 concentration of ≥80% in the flue gas. Then, it is heated to 35-45℃ by a reheating unit 29. A portion of the high-concentration CO2 flue gas is drawn to the carbon capture and purification unit 31 by a blower E30, while another portion of the high-concentration CO2 flue gas is sent to the cooling air of the cooler, the fuel supply air at the kiln head and kiln tail, the cooling air of the bypass venting system, and the air used by the equipment in the system that is prone to air leakage by a blower F32.

[0073] Bypass ventilation system and heat recovery: 5-30% (by volume) of the kiln flue gas is drawn from the flue chamber and rapidly cooled by blowing in high-concentration CO2 at 35-45℃ as cooling air. The flue gas then enters dust collector B17 for dust collection. A second round of high-concentration CO2 at 35-45℃ is then blown in to further cool the flue gas to 100-150℃, which is then used as cooling air in the second-stage cooler 6 to cool the clinker. This system utilizes the heat from the bypass ventilation system's flue gas for heat recovery, and the exhaust gas from the bypass ventilation system does not require environmental exhaust gas treatment.

[0074] Waste air heat recovery and utilization from the cooler: The waste air temperature of the second-stage cooler 6 is 250-300℃, and the air volume is 1.0-1.3 Nm³. 3 / kg.cl, after being dried in the raw material grinding system or cooled by the air cooler, it passes through the dust collector C23 for dust removal. The temperature of the exhaust gas from the raw material grinding is 100-150℃. Part of the exhaust gas is used as cooling air to cool the clinker, and the rest is discharged into the atmosphere.

[0075] This embodiment allows for rapid switching between air combustion and oxy-fuel combustion modes within 3-4 hours. The heat substitution rate of alternative fuels in cement kilns can reach over 90%. Although the decomposition furnace produces CO, the overall kiln tail system has a small air volume, and CO in the exhaust gas is used as fuel, helping the regenerative thermal oxidizer reduce fossil fuel consumption while simultaneously removing harmful gases such as CO and VOCs. The system also utilizes bypass venting and raw material mill heat recovery. The exhaust gas from the bypass venting system does not require separate environmental treatment, resulting in low heat consumption for the entire cement production system and significantly reducing investment in exhaust gas treatment equipment. Furthermore, in the oxy-fuel combustion mode of this invention, coupled with carbon capture technology, the dry-basis CO2 concentration of the preheater outlet flue gas is ≥80%, which can significantly reduce subsequent CO2 capture, purification, and operating costs.

[0076] The above embodiments have provided a detailed description of the present invention, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent variations and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A cement production method utilizing alternative fuel oxy-fuel combustion coupled with carbon capture, characterized in that: The cement production method using alternative fuel full oxy-fuel combustion coupled with carbon capture adopts a cement process system using alternative fuel full oxy-fuel combustion coupled with carbon capture. The cement process system using alternative fuel full oxy-fuel combustion coupled with carbon capture includes a preheater, a decomposition furnace, a flue, a rotary kiln and a second-stage cooler connected in sequence. The flue is connected to a bypass venting system and the second-stage cooler is connected to a raw material mill system. The cement production method utilizing alternative fuel oxy-fuel combustion coupled with carbon capture includes the following steps: Step 1: Alternative fuels are fed into the rotary kiln burner and the decomposition furnace, respectively. During operation, the O2 content in the flue gas at the decomposition furnace outlet is controlled to be less than 2.5%, the CO content to be 5000-10000 ppm, and the air volume at the decomposition furnace outlet to be 1.2-1.3 Nm³. 3 / kg.cl, CO2 concentration in flue gas (dry basis) ≥80%; Step 2: The exhaust gas from the preheater, after being cleaned by the waste heat power generation and treatment process, is condensed and dehydrated by a cooling and condensing device. Then, it is heated to 35-45℃ by a reheating device. A portion of the high-concentration CO2 flue gas is drawn to the carbon capture and purification device by fan E, while the other portion is sent to the first stage of the two-stage cooler, the kiln head burner and the kiln tail burner, as well as the bypass venting system quench chambers A and B by fan F. The O2 produced by the oxygen generation system is injected into the first stage of the two-stage cooler, the kiln head burner, the kiln door cover, or the tertiary air duct. The waste heat power generation and treatment process in step two includes the following steps: The exhaust gas exiting the preheater is either used for waste heat power generation A or cooled via a humidification tower to below 200°C. After passing through a high-temperature fan, the exhaust gas enters dust collector A for dust collection. The high-temperature fan controls the airflow and CO concentration exiting the preheater, and the dust concentration at the outlet of dust collector A is controlled at 10 mg / Nm³. 3 The gas then enters a regenerative thermal oxidizer, where CO in the exhaust gas provides some of the fuel. The high-temperature combustion of harmful VOCs keeps the VOC concentration below 20 mg / Nm³. 3 The waste gas, after VOCs removal and removal of CO, is then cooled to 100℃ via waste heat power generation or a water spray device, and then desulfurized by a desulfurization unit to control SO2 emissions in the waste gas to 35 mg / Nm³. 3 the following.

2. The cement production method according to claim 1, which utilizes alternative fuel oxy-fuel combustion coupled with carbon capture, is characterized in that: Following step two, the following steps are performed: Bypass ventilation process: 5-30% of the kiln exhaust gas by volume is drawn from the smoke chamber and blown in the 35-45℃ high-concentration CO2 flue gas obtained in step two as cooling air into the quenching chamber A to quench the bypass ventilation system flue gas. After that, it enters the dust collector B for dust collection. The 35-45℃ high-concentration CO2 flue gas obtained in step two is blown in again as cooling air in the quenching chamber B to quench the bypass ventilation system flue gas. After the second cooling, the temperature of the bypass ventilation high-concentration CO2 flue gas reaches 100-150℃. The low-temperature high-concentration CO2 flue gas exiting the bypass ventilation system is mixed with the O2 produced by the oxygen production system obtained in step two and used as cooling air to enter the first stage of the two-stage cooler.

3. The cement production method according to claim 1, which utilizes alternative fuel oxy-fuel combustion coupled with carbon capture, is characterized in that: Following step two, the following steps are added: Two-stage cooling machine process: A front-mounted roller crusher with a temperature resistance of about 850℃ is set up. A partition wall is set up at the crusher location to separate the first stage of the cooling machine from the second stage of the cooling machine. The blower of the first stage of the cooling machine is supplied with O2 generated by the oxygen production system in step one, cooling air from the bypass ventilation system, and high-concentration CO2 flue gas from the exhaust fan F. The blower of the second stage of the cooling machine is supplied with air or a portion of the exhaust gas from the raw material grinding system fan D.

4. The cement production method according to claim 1, which utilizes alternative fuel oxy-fuel combustion coupled with carbon capture, is characterized in that: After step two, there are the following steps: Cooler exhaust heat recovery process: The exhaust air from the cooler is sent to the raw material grinding system for raw material drying or cooled by an air cooler, and then passes through a dust collector for dust removal. Part of the exhaust gas enters the second stage of the two-stage cooler, and the remainder is discharged into the atmosphere.

5. The cement production method according to claim 1, which utilizes alternative fuel oxy-fuel combustion coupled with carbon capture, is characterized in that: The feed point and discharge pipe of the alternative fuel in the decomposition furnace are equipped with airlock devices to ensure that the O2 content in the exhaust gas from the preheater is less than 2%, the CO content is 4000-9000 ppm, the dry basis CO2 concentration in the flue gas is ≥80%, and the air volume at the preheater outlet is 1.3-1.4 Nm³. 3 / kg.cl; Preheaters or decomposition furnaces are equipped with denitrification devices to prevent NO from entering the environment. x Emissions up to 100 mg / Nm 3 the following; Alternative fuels are fed from multiple layers into the decomposition furnace. Fuels with a particle size of 3D<50mm and 2D<200mm are arranged in the middle of the decomposition furnace, while fuels with a particle size of 3D<5mm and 2D<50mm are arranged in the lower part of the decomposition furnace.

6. A cement process system utilizing alternative fuel oxy-fuel combustion coupled with carbon capture, characterized in that: A cement process system utilizing alternative fuel oxy-fuel combustion coupled with carbon capture is used in the cement production method according to any one of claims 1-5. The exhaust gas from the preheater passes through the waste heat power generation and treatment system and enters the cooling and condensing device. The cooling and condensing device is connected to the reheating device. The reheating device is connected to the carbon capture and purification device through fan E. The reheating device is connected to the first stage of the second-stage cooler, the kiln head burner and the kiln tail burner, as well as the bypass ventilation system's fans A and C through fan F. The oxygen production system is connected to the first stage of the second-stage cooler, the kiln head burner, the kiln door cover, or the tertiary air duct.

7. The cement process system utilizing alternative fuel oxy-fuel combustion coupled with carbon capture according to claim 6, characterized in that: The waste heat power generation and exhaust gas treatment system includes a waste heat power generation unit A and a humidification tower connected in parallel. After being connected in parallel, they are sequentially connected to a high-temperature fan, a dust collector A, and a regenerative thermal incinerator. The waste heat power generation unit B and a water spraying device are connected in parallel. After being connected in parallel, one end is connected to the regenerative thermal incinerator, and the other end is connected to the desulfurization device. The bypass ventilation system includes a quench chamber A, a dust collector B, a fan B and a quench chamber B connected in sequence. The quench chamber A is connected to the fan A, and the quench chamber B is connected to the fan C. The fan A and the fan C blow in the low-temperature, high-concentration CO2 flue gas after the exhaust fan F. The bypass ventilation system's exhaust pipe is connected to the oxygen production system and to the first stage of the two-stage cooler. The raw material grinding system includes a raw material mill and an air cooler connected in parallel. After being connected in parallel, it is sequentially connected to a dust collector C and a fan D. Part of the air from the raw material mill system goes to the second stage of the second-stage cooler as cooling air, and part goes to the chimney and is discharged into the atmosphere.

8. The cement process system utilizing alternative fuel oxy-fuel combustion coupled with carbon capture according to claim 6, characterized in that: The fan F is connected to the system's leak-prone equipment, which includes the kiln head sealing device, the kiln tail sealing device, the waste heat power generation dust removal device A, and the dust collectors A and B.

9. A method for producing cement that can switch between air combustion and oxy-fuel combustion, the method comprising the following steps: When alternative fuel air combustion method is adopted: air is sent by blower to the cooler cooling air, the kiln head and kiln tail fuel supply air, and the bypass venting system cooling air respectively; When adopting the cement production method of all-oxygen combustion coupled with carbon capture using alternative fuels as described in any one of claims 1-5: the clean waste gas after waste heat power generation and environmental protection waste gas treatment is cooled and condensed to remove most of the moisture, resulting in high-concentration CO2 flue gas with a dry basis CO2 concentration of ≥80%, and then heated to 35-45°C by a reheater. A portion of the high-concentration CO2 flue gas is blown to the carbon capture and purification device by a fan, and another portion of the high-concentration CO2 flue gas is sent by a fan to the cooling air of the cooler, the fuel supply air at the kiln head and kiln tail, the cooling air of the bypass venting system, and the air used by the system's easily leaking equipment.

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