A suspension calcining system with a function of reducing CO2 partial pressure and a method for preparing high-activity lime by using the same

Abstract

The application discloses a suspension calcining system with a CO2 partial pressure reduction function and a method for preparing high-activity lime, and belongs to the technical field of lime stone calcination. The system comprises a pretreatment unit, a calcining unit, a cooling unit, a dust removal unit, a CO2 treatment unit and a product bin. The steps for preparing high-activity lime are as follows: after crushing the lime stone raw ore, the lime stone powder is added into a lime stone powder feeding bin, is fed into a cyclone preheater for three-stage preheating, is added into a suspension calcining furnace for calcination, air is introduced into the bottom of the calcining furnace during the calcination process, and the powder is ensured to be in a suspension state at all times; the powder after the calcination is sent into a cyclone cooler for three-stage cooling, and high-activity lime is obtained. In the process of preparing high-activity lime, the powder is heated more uniformly, the heat transfer efficiency is higher, the flowing gas timely discharges the CO2 generated by the decomposition, the CO2 treatment equipment is used for separation, the lime stone decomposition is moved to a positive direction, the decomposition speed is accelerated, and the decomposition efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of limestone calcination technology, specifically relating to a suspension calcination system with CO2 partial pressure reduction function and a method for preparing highly active lime. Background Technology

[0002] Lime is an important chemical raw material, widely used in building materials, metal smelting, glass fiber, environmental protection, agriculture and other fields, playing an irreplaceable role in industrial production and daily life.

[0003] Industrially, lime is primarily produced by calcining limestone at high temperatures. At these high temperatures, calcium carbonate, the main component of limestone, undergoes a decomposition reaction: CaCO3(s) = CaO(s) + CO2(g). On one hand, the decomposition of limestone requires a large amount of heat, which in traditional processes typically comes from fossil fuels such as coal, leading to high carbon dioxide emissions. On the other hand, besides producing quicklime (CaO), the decomposition of limestone also releases CO2, a source of carbon emissions. Therefore, lime production is a high-energy-consuming and high-emission industry.

[0004] Currently, the main equipment used in industrial lime production includes vertical kilns, double-chamber kilns, and rotary kilns. The comparison information of various calcination equipment is shown in the table below. During the calcination process, these equipment or systems often require coal to maintain a stable calcination temperature, resulting in high energy consumption. Furthermore, the CO2 produced during calcination cannot be separated in time and remains inside the kiln, causing excessively high CO2 partial pressure inside the kiln. Numerous studies (Hong Zongxian, Tao Congxi, Li Wei, et al. Study on thermal decomposition characteristics of limestone under different CO2 concentrations [J]. China Cement, 2023, (10): 53-57. Cao Jing, Qiao Xiuchen, Liu Chengliang, et al. Decomposition kinetics of limestone in a mixed atmosphere of carbon dioxide and air [J]. Inorganic Salt Industry, 2016, 48(12): 32-36, etc.) have shown that, at the same calcination temperature, increasing the CO2 concentration will inhibit the decomposition reaction of limestone, resulting in a slower decomposition rate and a longer decomposition time. For example, at 925℃, when the CO2 concentration increases from 35% to 78%, the time to reach the same decomposition rate differs by more than double.

[0005]

[0006] In addition, calcining limestone in a high-concentration CO2 atmosphere not only prevents the forward decomposition reaction but also leads to severe "under-firing" of the lumpy limestone. Studies have shown (Feng Xiaoping, Zhou Xiaodong, Xie Junlin, et al. The effect of lime calcination process and its structure on activity [J]. Journal of Wuhan University of Technology, 2004, (07): 28-30.) that specific surface area, pore volume, and pore size are positively correlated with the activity of limestone. The larger the specific surface area, pore volume, and pore size, the higher the activity of limestone. In traditional processes, due to the large particle size of limestone, CO2 encounters greater resistance when it is transported from the inside of the particles to the outside during calcination, resulting in poor CO2 discharge and thus affecting the activity of the product. Especially for limestone particles larger than 40mm, the larger particle size will cause uneven heat transfer. The particle surface has already decomposed, but the heat cannot be transferred to the inside for a long time, resulting in over-firing and "porcelainization" of the surface and under-firing and "hard core" inside. On the other hand, the CO2 generated inside cannot be discharged into the environment in time, resulting in a slower decomposition rate. Therefore, in traditional processes, the lime produced by calcining large-particle-size limestone has low activity and is unstable.

[0007] Patents CN109467323B ("Lime Suspension Calcination Process Equipment") and CN117049800A ("A High-Stability Calcium Carbonate Suspension Calcination System and Method") use suspension calcination technology as their core, reducing the calcined particle size of limestone to below 1mm. Compared with traditional processes and equipment, this particle size reduction significantly improves decomposition efficiency. However, in actual production, as limestone decomposes continuously, the CO2 partial pressure in the calcination furnace increases, leading to unstable furnace temperature and decreased decomposition efficiency. Patent CN 117567053A ("A Suspension Calcination System to Improve Limestone Decomposition Rate") proposes that the CO2 generated during decomposition can be carried away by airflow, reducing the CO2 partial pressure in the calcination furnace and accelerating the decomposition reaction. However, it is worth noting that in this method, CO2 is simply carried away by the airflow and is not separated. During continuous production, the CO2 concentration in the airflow remains relatively high.

[0008] Therefore, there is still research value in how to effectively reduce the CO2 partial pressure in a suspension calcining furnace. Based on this, the present invention is proposed. Summary of the Invention

[0009] To address the shortcomings of existing technologies and solve the aforementioned problems, this invention first connects the high-temperature gas discharged from the calcining furnace to a CO2 treatment device after cyclone separation. This timely separation of CO2 from the high-temperature gas reduces the CO2 partial pressure within the calcining furnace, shifting the decomposition reaction in the forward direction and accelerating the decomposition of limestone fine powder. After CO2 separation, the high-temperature gas is fed into a preheater for heat energy recycling. Using the suspension calcination system proposed in this invention, calcination of limestone across all particle sizes can be achieved, and higher reaction efficiency and product activity are observed during limestone decomposition.

[0010] A suspension calcination system with CO2 partial pressure reduction function includes a pretreatment unit, a calcination unit, a cooling unit, a dust removal unit, a CO2 treatment unit, and a product bin. The discharge end of the pretreatment unit is connected to the feed end of the calcination unit, the discharge end of the calcination unit is connected to the feed end of the cooling unit, the discharge end of the cooling unit is connected to the feed end of the product bin, the discharge end of the dust removal unit is connected to the feed end of the pretreatment unit, the air inlet of the pretreatment unit is connected to the air outlet of the CO2 treatment unit, the air outlet of the pretreatment unit is connected to the air inlet of the dust removal unit, the air inlet of the calcination unit is connected to the air outlet of the cooling unit, and the air outlet of the calcination unit is connected to the air inlet of the CO2 treatment unit.

[0011] The pretreatment unit includes a limestone powder feed hopper, a first-stage cyclone preheater, a second-stage cyclone preheater, and a third-stage cyclone preheater. The outlet of the limestone powder feed hopper is connected to a feed inlet on one side of the first-stage cyclone preheater. The first-stage cyclone preheater has an air outlet at the top, a discharge outlet at the bottom, and an air inlet on the other side. The discharge outlet of the first-stage cyclone preheater is connected to a first feed inlet on one side of the second-stage cyclone preheater. The second-stage cyclone preheater has an air outlet at the top, an air inlet on one side, a second feed inlet on the other side, and a discharge outlet at the bottom. The air outlet of the second-stage cyclone preheater is connected to the air inlet of the first-stage cyclone preheater. The air inlet of the second-stage cyclone preheater is connected to the air outlet at the top of the third-stage cyclone preheater. The discharge outlet of the second-stage cyclone preheater is connected to a feed inlet on one side of the third-stage cyclone preheater. The third-stage cyclone preheater has an air inlet on one side and a discharge outlet at the bottom.

[0012] The calcination unit includes a first feeder, an air supply device, a suspension calcination furnace, and a cyclone separator. The feed port of the first feeder is connected to the discharge port of the third-stage cyclone preheater, and the discharge port of the first feeder is connected to the feed port on one side of the suspension calcination furnace. The suspension calcination furnace has air inlets on both sides, an air outlet and a first discharge port at the top, and a second discharge port at the bottom. The air inlets on both sides of the suspension calcination furnace are connected to the air supply device. The air outlet and the first discharge port of the suspension calcination furnace are respectively connected to the first air inlet and the feed port on one side of the cyclone separator. The cyclone separator has an air outlet at the top and a discharge port and a second air inlet at the bottom.

[0013] The cooling unit includes a first-stage cyclone cooler, a second-stage cyclone cooler, a third-stage cyclone cooler, and a fan. The first-stage cyclone cooler has a first feed inlet and an air outlet at the top, a second feed inlet and an air inlet on one side, and an outlet at the bottom. The first feed inlet of the first-stage cyclone cooler is connected to the outlet of the cyclone separator, the air outlet of the first-stage cyclone cooler is connected to the second air inlet of the cyclone separator, and the second feed inlet of the first-stage cyclone cooler is connected to the outlet of the suspension calcining furnace. The second-stage cyclone cooler has an air outlet at the top, a feed inlet and an air inlet on one side, and a fan at the bottom. The first-stage cyclone cooler has a discharge port, and its air outlet is connected to the air inlet of the first-stage cyclone cooler. Its feed inlet is connected to the discharge port of the first-stage cyclone cooler. The third-stage cyclone cooler has an air outlet at the top, a feed inlet on one side, an air inlet on the other side, and a discharge port at the bottom. Its air outlet is connected to the air inlet of the second-stage cyclone cooler, its feed inlet is connected to the discharge port of the second-stage cyclone cooler, its air inlet is connected to the fan, and its discharge port is connected to the product hopper.

[0014] The dust removal unit includes a dust collector, an ash storage silo, a second feeder, and a chimney. The dust collector has an air inlet on one side, an air outlet on the other side, and a discharge outlet at the bottom. The air inlet of the dust collector is connected to the air outlet of the first-stage cyclone preheater, and the air outlet of the dust collector is connected to the air inlet of the chimney. The ash storage silo has a feed inlet at the top and a discharge outlet at the bottom. The feed inlet of the ash storage silo is connected to the discharge outlet of the dust collector, and the discharge outlet of the ash storage silo is connected to the feed inlet of the second feeder. The discharge outlet of the second feeder is connected to the second feed inlet of the second-stage cyclone preheater.

[0015] The CO2 processing unit includes a CO2 processing device and a CO2 storage tank. The CO2 processing device has a first air outlet on one side, a second air outlet on the other side, and an air inlet at the bottom. The air inlet of the CO2 processing device is connected to the air outlet of the cyclone separator. The first air outlet of the CO2 processing device is connected to the air inlet of the third-stage cyclone preheater. The second air outlet of the CO2 processing device is connected to the air inlet of the CO2 storage tank.

[0016] The third-stage cyclone cooler is connected to the product warehouse via a transport device, which is either a conveyor belt or a unloader.

[0017] The CO2 processing equipment specifically employs a device capable of separating and capturing CO2 from gas under high temperature and high pressure conditions, and also capable of collecting, compressing, and storing the captured CO2 gas.

[0018] A method for preparing highly active lime using a suspension calcination system with CO2 partial pressure reduction function, comprising the following steps:

[0019] Step 1. Preparation and preheating of limestone fine powder: After crushing the raw limestone ore to -1mm, it is added to the limestone powder feed hopper and fed into the first-stage cyclone preheater through the conveying device for the first-stage preheating. Then, the powder is fed into the second-stage cyclone preheater and the third-stage cyclone preheater in sequence for the second-stage and third-stage preheating.

[0020] Step 2. Limestone fine powder suspension calcination and separation: After three-stage preheating, the limestone powder is added to the suspension calcination furnace through the first feeder for calcination. During the calcination process, air is introduced into the bottom of the suspension calcination furnace to ensure that the limestone powder added into the furnace is always in a suspended state. After calcination, part of the limestone powder is carried by the high-temperature gas and enters the cyclone separator through the first discharge port at the top of the suspension calcination furnace, while the other part enters the first-stage cyclone cooler through the second discharge port at the bottom of the calcination furnace. The high-temperature gas carrying part of the calcined product is separated by the cyclone separator, and the hot gas enters the CO2 treatment equipment through the gas outlet above the cyclone separator. After treatment, it enters the third-stage cyclone preheater to provide heat for heat circulation. The limestone powder separated by the cyclone separator is sent to the first-stage cyclone cooler through the discharge port at the bottom of the cyclone separator.

[0021] Step 3. Cooling of Calcinated Product: The limestone powder in the suspension calciner and cyclone separator is fed into the first-stage cyclone cooler for first-stage cooling. Hot air enters the cyclone separator through the upper outlet for heat recovery and separation. The powder after first-stage cooling enters the second-stage cyclone cooler through the outlet of the first-stage cyclone cooler for second-stage cooling. The gas in the second-stage cyclone cooler enters the first-stage cyclone cooler through the flue gas channel for heat exchange, accelerating the cooling of the powder. After the second cooling, the powder continues to be fed into the third-stage cyclone cooler for a third cooling, resulting in highly active lime. The third-stage cyclone cooler is connected to a fan, which continuously supplies cooling air through pipes to accelerate the entire cooling process. The cooling air in the third-stage cyclone cooler enters the second-stage cyclone cooler through the upper outlet to participate in heat exchange and improve the cooling efficiency of the second cooling process.

[0022] Step 4. Storage of calcined products: The highly active lime obtained after three cooling cycles is fed into the product silo by a transport device through the outlet of the third-stage cyclone cooler for storage.

[0023] in:

[0024] In step 1, the CaO content in the raw limestone ore is ≥50%.

[0025] In step 1, the preheating temperature in the first-stage cyclone preheater is 100-200℃ and the preheating time is 5-10 min; the preheating temperature in the second-stage cyclone preheater is 300-500℃ and the preheating time is 8-10 min; and the preheating temperature in the third-stage cyclone preheater is 600-800℃ and the preheating time is 10-15 min.

[0026] In step 2, the air flow velocity introduced into the bottom of the suspension calcining furnace is 15-25 m / s; the temperature inside the suspension calcining furnace is set to 950-1050℃, and the calcination time is 3-15 min.

[0027] In step 3, the cooling time for the first stage of cooling is 3 to 10 minutes, and the temperature of the cooled powder is 750 to 850°C; the cooling time for the second stage of cooling is 5 to 10 minutes, and the temperature of the cooled powder is 300 to 400°C; the cooling time for the third stage of cooling is 5 to 15 minutes, and the temperature of the cooled powder is 80 to 100°C.

[0028] In step 3, the CaO content in the highly active lime is ≥92%; according to YB / T042-2014, the activity is ≥360mL.

[0029] Compared with the prior art, the beneficial effects and innovative points of the present invention are as follows:

[0030] 1. In the process of preparing highly active lime, the powder is in a high-temperature suspension flow dynamic, which results in more uniform heating and higher heat transfer efficiency. The flowing gas can promptly discharge the CO2 generated by decomposition, and the CO2 treatment equipment can promptly separate the CO2 generated by decomposition. On the one hand, this can make the limestone decomposition move in the positive direction, accelerate the decomposition speed, and improve the decomposition efficiency; on the other hand, it can separate, capture, and store CO2, reduce CO2 emissions, and reduce environmental pollution.

[0031] 2. The feed particle size of the suspension calcination furnace in this application is less than 1 mm. Whether it is medium-to-large-diameter (40-300 mm) limestone or small-diameter limestone (<20 mm), it can be crushed to less than 1 mm, realizing the calcination of limestone resources of all particle sizes and improving the utilization rate of resources. In addition, the limestone fine powder in suspension is heated more evenly, the decomposition efficiency is higher, and the product quality is better.

[0032] 3. The system of this application introduces a heat recovery system, which effectively recovers and utilizes the high-temperature waste heat generated during the calcination process, reduces energy consumption and production costs, and at the same time reduces the impact on the environment, which meets the requirements of sustainable development. Attached Figure Description

[0033] Figure 1A schematic diagram of a limestone fine powder suspension calcination system with CO2 partial pressure reduction function according to the present invention;

[0034] Among them, 1-limestone powder feeding silo, 2-first-stage cyclone preheater, 3-second-stage cyclone preheater, 4-third-stage cyclone preheater, 5-first feeder, 6-air supply equipment, 7-suspension calcining furnace, 8-cyclone separator, 9-first-stage cyclone cooler, 10-second-stage cyclone cooler, 11-third-stage cyclone cooler, 12-fan, 13-dust collector, 14-ash storage silo, 15-second feeder, 16-chimney, 17-product silo, 18-CO2 treatment equipment, 19-CO2 storage tank;

[0035] Figure 2 A process flow diagram of a method for preparing highly active lime using a suspension calcination system with CO2 partial pressure reduction function according to the present invention. Detailed Implementation

[0036] Example 1

[0037] A schematic diagram of a limestone fine powder suspension calcination system with CO2 partial pressure reduction function is shown below. Figure 1 As shown, the system includes a pretreatment unit, a calcination unit, a cooling unit, a dust removal unit, a CO2 treatment unit, and a product silo 17. The discharge end of the pretreatment unit is connected to the feed end of the calcination unit, the discharge end of the calcination unit is connected to the feed end of the cooling unit, the discharge end of the cooling unit is connected to the feed end of the product silo 17, and the discharge end of the dust removal unit is connected to the feed end of the pretreatment unit. The air inlet of the pretreatment unit is connected to the air outlet of the CO2 treatment unit, the air outlet of the pretreatment unit is connected to the air inlet of the dust removal unit, the air inlet of the calcination unit is connected to the air outlet of the cooling unit, and the air outlet of the calcination unit is connected to the air inlet of the CO2 treatment unit.

[0038] The pretreatment unit includes a limestone powder feeding silo 1, a first-stage cyclone preheater 2, a second-stage cyclone preheater 3, and a third-stage cyclone preheater 4. The limestone powder in the limestone powder feeding silo 1 is connected to the feed port on one side of the first-stage cyclone preheater 2 via its discharge port, and the powder enters the first-stage cyclone preheater 2 through its discharge port. The first-stage cyclone preheater 2 has an air outlet at the top, a discharge port at the bottom, a feed port on one side, and an air inlet on the other side. The discharge port of the first-stage cyclone preheater 2 is connected to the first feed port on one side of the second-stage cyclone preheater 3. After the powder undergoes the first preheating, it is fed into the second-stage cyclone preheater 3. The second-stage cyclone preheater 3 has an air outlet at the top, an air inlet on one side, and a second feed port on the other side. The feed inlet is located at the bottom, and the discharge outlet is located at the bottom. The outlet of the second-stage cyclone preheater 3 is connected to the inlet of the first-stage cyclone preheater 2 through a flue gas passage. After heat exchange, the hot air in the second-stage cyclone preheater 3 enters the first-stage cyclone preheater 2 through the flue gas passage to participate in the first preheating. The inlet of the second-stage cyclone preheater 3 is connected to the outlet of the third-stage cyclone preheater 4 through a flue gas passage. The hot air in the third-stage cyclone preheater 4 enters the second-stage cyclone preheater 3 through the flue gas passage. The discharge outlet of the second-stage cyclone preheater 3 is connected to the feed inlet of the third-stage cyclone preheater 4. After the powder is preheated for the second time, it is fed into the third-stage cyclone preheater 4. The third-stage cyclone preheater 4 has an inlet on one side and a discharge outlet at the bottom.

[0039] The calcination unit includes a first feeder 5, an air supply device 6, a suspension calcination furnace 7, and a cyclone separator 8. The feed port of the first feeder 5 is connected to the discharge port of the third-stage cyclone preheater 4, and the discharge port of the first feeder 5 is connected to a feed port on one side of the suspension calcination furnace 7. After the third preheating, the powder is fed into the suspension calcination furnace 7 for calcination by controlling the feeding speed through the first feeder 5. The suspension calcination furnace 7 has air inlets on both sides, an air outlet and a first discharge port at the top, and a second discharge port at the bottom. The air inlets on both sides of the suspension calcination furnace 7 are connected to the air supply device 6. During the calcination process, air enters the suspension calcining furnace 7 through the air inlet via the air supply device 6. The air outlet of the suspension calcining furnace 7 is connected to the first air inlet on one side of the cyclone separator 8 through the flue gas channel. The hot gas in the furnace enters the cyclone separator 8 through the upper flue gas channel. The first discharge port of the suspension calcining furnace 7 is connected to the feed port on one side of the cyclone separator 8 through the discharge channel. A portion of the calcined product in the suspension calcining furnace 7 enters the cyclone separator 8 under the action of the airflow. The cyclone separator 8 is provided with an air outlet at the top and a discharge port and a second air inlet at the bottom.

[0040] The cooling unit includes a first-stage cyclone cooler 9, a second-stage cyclone cooler 10, a third-stage cyclone cooler 11, and a fan 12. The first-stage cyclone cooler 9 has a first feed inlet and an outlet at its top, a second feed inlet and an inlet on one side, and an outlet at its bottom. The first feed inlet of the first-stage cyclone cooler 9 is connected to the outlet of the cyclone separator 8. The outlet of the first-stage cyclone cooler 9 is connected to the second inlet of the cyclone separator 8 through a flue gas passage. The rising flue gas in the first-stage cyclone cooler 9 enters the cyclone separator 8 after heat exchange, where it interacts with the high-temperature flue gas from the suspension calcining furnace 7. Under the combined action of the airflow, the temperature inside the cyclone separator 8 is between 800 and 900℃. The second feed port of the first-stage cyclone cooler 9 is connected to the discharge port of the suspension calcining furnace 7. Another portion of the calcined product from the suspension calcining furnace 7 is fed into the first-stage cyclone cooler 9 through the bottom unloading device, and the two portions of calcined product undergo the first cooling. The second-stage cyclone cooler 10 has an air outlet at the top, a feed port and an air inlet on one side, and an air outlet at the bottom. The air outlet of the second-stage cyclone cooler 10 is connected to the air inlet of the first-stage cyclone cooler 9 through a flue gas passage. The gas in the flue gas enters the first-stage cyclone cooler 9 through the flue gas passage; the inlet of the second-stage cyclone cooler 10 is connected to the outlet of the first-stage cyclone cooler 9, and the calcined product after the first cooling undergoes secondary cooling in the second-stage cyclone cooler 10; the third-stage cyclone cooler 11 has an outlet at the top, a feed inlet on one side, an inlet on the other side, and an outlet at the bottom. The outlet of the third-stage cyclone cooler 11 is connected to the inlet of the second-stage cyclone cooler 10 through the flue gas passage, and the air in the third-stage cyclone cooler 11 enters the second-stage cyclone cooler 10 to participate in the heating process. The feed inlet of the third-stage cyclone cooler 11 is connected to the discharge outlet of the second-stage cyclone cooler 10. The calcined product, after the second cooling, undergoes three cooling processes in the third-stage cyclone cooler 11, with the temperature dropping below 100℃. The product is then transferred into the product silo 17 via a transport device. The air inlet of the third-stage cyclone cooler 11 is connected to the fan 12, and cooling air is sent into the third-stage cyclone cooler 11 through the fan 12 to achieve rapid cooling of the powder in the third-stage cyclone cooler 11. The discharge outlet of the third-stage cyclone cooler 11 is connected to the product silo 17 via a conveyor belt or unloader.

[0041] The dust removal unit includes a dust collector 13, an ash storage bin 14, a second feeder 15, and a chimney 16. The dust collector 13 has an air inlet on one side, an air outlet on the other side, and a discharge outlet at the bottom. The air inlet of the dust collector 13 is connected to the air outlet of the first-stage cyclone preheater 2 through a flue gas channel, and the air outlet of the dust collector 13 is connected to the air inlet of the chimney 16 through a pipe. After the flue gas is separated by the dust collector 13, the qualified waste gas is discharged from the chimney 16 through a gas channel. The ash storage bin 14 has an inlet at the top and a discharge outlet at the bottom. The inlet of the ash storage bin 14 is connected to the discharge outlet of the dust collector 13, and the discharge outlet of the ash storage bin 14 is connected to the inlet of the second feeder 15. The discharge outlet of the second feeder 15 is connected to the second feed outlet of the second-stage cyclone preheater 3.

[0042] The CO2 processing unit includes a CO2 processing device 18 and a CO2 storage tank 19. The CO2 processing device 18 has a first outlet on one side, a second outlet on the other side, and an inlet at the bottom. The inlet of the CO2 processing device 18 is connected to the outlet of a cyclone separator 8 via a flue gas channel. Hot air from the cyclone separator 8 enters the CO2 processing device 18 through a flue gas duct. The first outlet of the CO2 processing device 18 is connected to the inlet of a third-stage cyclone preheater 4 via a pipe. The high-temperature gas after CO2 separation enters the third-stage cyclone preheater 4 through a pipe. The temperature of the third-stage cyclone preheater 4 is between 600 and 800°C. The second outlet of the CO2 processing device 18 is connected to the CO2 storage tank 19.

[0043] After CO2 in the high-temperature gas is separated and captured by the CO2 treatment device 18, the CO2 concentration in the hot gas decreases significantly from 50%–80% before separation to 8%–20%. The partial pressure of CO2 in the calcining furnace is further reduced, which is conducive to the decomposition reaction. The separated hot gas is discharged into the third-stage cyclone preheater 4 through the exhaust port above the CO2 treatment device 18 via a pipeline, providing heat energy for the third-stage cyclone preheater 4 and realizing heat energy circulation. The captured CO2 is collected, compressed, and stored in the CO2 storage tank 19. The CO2 in the CO2 storage tank 19 can be reused as a high-concentration CO2 resource or used for geological storage.

[0044] The CO2 processing device 18 is a device that can separate and capture CO2 in gas under high temperature and high pressure environment. It also has the function of collecting, compressing and storing the captured CO2 gas. In this embodiment, the CO2 processing device adopts the technical solution published in Chinese patent application with announcement number CN201304322Y. The separated CO2 gas is collected and stored in CO2 storage tank 19.

[0045] Example 2

[0046] The limestone ore used in this embodiment has a CaO content of 54.22% and contains a small amount of impurities such as quartz.

[0047] A method for preparing highly active lime using a suspension calcination system with CO2 partial pressure reduction function, the process flow diagram is as follows: Figure 2 As shown, the specific steps include:

[0048] Step 1. Preparation and preheating of limestone fine powder: After crushing the raw limestone ore to -1mm, it is added to the limestone powder feed hopper 1 and fed into the first-stage cyclone preheater 2 through a conveying device for first-stage preheating at a temperature of 120℃ for 5 minutes to remove moisture from the powder and keep it dry. Subsequently, the powder is fed into the second-stage cyclone preheater 3 and the third-stage cyclone preheater 4 for second-stage and third-stage preheating, respectively. At this time, some limestone powder has begun to decompose. The preheating temperature for the second stage is 400℃ for 8 minutes, and the preheating temperature for the third stage is 700℃ for 10 minutes.

[0049] In the suspension calcination process, controlling the limestone particle size is crucial to ensuring the limestone powder remains in a suspended state. Crushing and sieving the raw limestone ore to -1mm ensures uniform particle size, which enhances the suspension motion of the limestone powder within the suspension calcination furnace 7, improving the reaction efficiency during the calcination stage. Before being fed into the preheater, the limestone powder is first dried in a dryer to prevent agglomeration and ensure even dispersion in the preheater and suspension calcination furnace 7. This invention incorporates a three-stage preheating process. This utilizes the waste heat from the suspension calcination furnace 7 for heat energy circulation, reducing energy consumption. More importantly, it allows the limestone powder to reach its decomposition temperature earlier, shortening its residence time in the suspension calcination furnace 7, thus reducing energy consumption, improving decomposition efficiency, and maintaining the smoothness of the entire calcination process.

[0050] Step 2. Limestone Powder Suspension Calcination and Separation: After three-stage preheating, the limestone powder is added to the suspension calcination furnace 7 through the first feeder 5 for calcination. The temperature inside the calcination furnace is set to 950℃, and the calcination time is 12 minutes. During the calcination process, air is introduced into the bottom of the suspension calcination furnace 7 at a flow rate of 15 m / s to ensure that the limestone powder added to the furnace remains in suspension. After calcination, a portion of the limestone powder is carried by the high-temperature gas through the first discharge outlet at the top of the suspension calcination furnace 7. One part enters the cyclone separator 8, and the other part enters the first-stage cyclone cooler 9 through the second discharge port at the bottom of the suspension calcining furnace 7. The high-temperature gas carrying part of the calcined product is separated by the cyclone separator 8, and the hot gas enters the CO2 treatment equipment 18 through the gas outlet above the cyclone separator 8. After treatment, it enters the third-stage cyclone preheater 4 to provide heat for heat circulation. The limestone powder separated by the cyclone separator 8 is sent to the first-stage cyclone cooler 9 through the discharge port at the bottom of the cyclone separator 8.

[0051] The suspension calcining furnace 7 is the core of the entire process. This equipment is a cylindrical container with heating devices on the inner wall and a gas supply device at the bottom. The design of the suspension calcining furnace 7 ensures that the limestone fine powder reacts in a high-temperature gas flow environment, while maintaining the uniform distribution and suspension flow of the particles.

[0052] In the suspension calcination furnace 7, controlling the temperature and airflow within the reaction chamber is crucial. The temperature range within the reaction chamber is 950℃ to 1050℃. Under these high-temperature conditions, the reaction of calcium carbonate in the limestone powder proceeds as follows:

[0053] CaCO3(s)=CaO(s)+CO2(g)

[0054] Although this reaction is thermodynamically reversible, under high temperature conditions, the reaction will shift towards the formation of calcium oxide.

[0055] The flow of high-temperature gas causes the fine limestone particles to be in a suspended spiral flow state. This shortens the time it takes for heat to reach the particle surface from the environment and for heat to transfer from the particle surface to the interior of the particle. The limestone particles are heated evenly and thoroughly, significantly accelerating the limestone decomposition rate. In traditional processes, calcination at 900–1100℃ often requires 2–4 hours to achieve the desired activity, while suspension calcination technology can achieve it in just 5–20 minutes.

[0056] Step 3. Cooling of Calcinated Product: The limestone powder in the suspension calciner 7 and cyclone separator 8 is fed into the first-stage cyclone cooler 9 for first-stage cooling. The cooling time for the first stage is 5 minutes, and the temperature of the cooled powder is 750℃. The hot air enters the cyclone separator 8 through the upper outlet for heat recovery and separation. The powder after the first stage cooling enters the second-stage cyclone cooler 10 through the outlet of the first-stage cyclone cooler 9 for second-stage cooling. The cooling time for the second stage cooling is 8 minutes, and the temperature of the cooled powder is 350±20℃. The hot air in the second-stage cyclone cooler 10... The gas enters the first-stage cyclone cooler 9 through the flue gas passage for heat exchange, accelerating the cooling of the powder. After the second cooling, the powder continues to be fed into the third-stage cyclone cooler 11 for a third cooling. The cooling time of the third stage is 10 minutes, and the temperature of the cooled powder is 80℃. The third-stage cyclone cooler 11 is connected to a fan 12, which continuously supplies cooling air through pipes to accelerate the entire cooling process. The cooling air in the third-stage cyclone cooler 11 enters the second-stage cyclone cooler 10 through the upper air outlet to participate in heat exchange and improve the cooling efficiency of the second cooling process.

[0057] In the suspension calcination furnace 7, when the CO2 produced by the decomposition of limestone fine powder overflows from the inside of the particles into the external environment, it forms CO2 channels inside the particles. These channels greatly increase the specific surface area of ​​the product and also increase its pore volume and pore size. Completely different from traditional processes, in the high-temperature suspension calcination process, the flow of high-temperature gas promptly carries away the CO2 produced by decomposition. The CO2 is then separated from the hot gas by a CO2 separator, reducing the partial pressure of CO2 in the reaction chamber. This not only shifts the reaction forward and further accelerates the reaction rate, but more importantly, the timely removal of CO2 leaves irregular and dense channels inside the particles. These channels increase the specific surface area, pore volume, and pore size of the product, significantly improving its activity.

[0058] Step 4. Storage of calcined products: After three cooling cycles, the lime powder is fed into the product silo 17 by a transport device through the outlet of the third-stage cyclone cooler 11 for storage.

[0059] The CaO content in the highly active lime obtained in this example is 92.42%, and the activity is 427.34 mL (according to YB / T105-2014).

[0060] Example 3

[0061] The apparatus is the same as in Embodiment 1, and the method is the same as in Embodiment 2, except that:

[0062] 1. The limestone ore used has a CaO content of 54.02% and contains a small amount of impurities such as dolomite and quartz.

[0063] 2. The preheating temperature for the first stage is 150℃ and the preheating time is 5 minutes; the preheating temperature for the second stage is 450℃ and the preheating time is 10 minutes; the preheating temperature for the third stage is 800℃ and the preheating time is 10 minutes.

[0064] 3. The temperature inside the suspension calcining furnace 7 is set to 1000℃, the calcination time is 12min, and the air flow velocity at the bottom of the suspension calcining furnace 7 is 20m / s.

[0065] 4. The cooling time for the first stage of cooling is 5 minutes, and the temperature of the powder after cooling is 800±20℃; the cooling time for the second stage of cooling is 8 minutes, and the temperature of the powder after cooling is 350℃; the cooling time for the third stage of cooling is 10 minutes, and the temperature of the powder after cooling is 80℃.

[0066] The CaO content in the highly active lime obtained in this example is 93.27%, and the activity is 420.56 mL (according to YB / T105-2014).

[0067] Example 4

[0068] The apparatus is the same as in Embodiment 1, and the method is the same as in Embodiment 2, except that:

[0069] 1. The limestone ore used has a CaO content of 52.73% and contains a small amount of impurities such as dolomite and quartz.

[0070] 2. The preheating temperature for the first stage is 200℃ and the preheating time is 7 min; the preheating temperature for the second stage is 500℃ and the preheating time is 8 min; the preheating temperature for the third stage is 750℃ and the preheating time is 15 min.

[0071] 3. The temperature inside the suspension calcining furnace 7 is set to 1050℃, the calcination time is 8min, and the air flow velocity at the bottom of the suspension calcining furnace 7 is 18m / s.

[0072] 4. The cooling time for the first stage of cooling is 5 minutes, and the temperature of the powder after cooling is 800℃; the cooling time for the second stage of cooling is 10 minutes, and the temperature of the powder after cooling is 350℃; the cooling time for the third stage of cooling is 10 minutes, and the temperature of the powder after cooling is 90℃.

[0073] The CaO content in the highly active lime obtained in this example is 92.02%, and the activity is 420.74 mL (according to YB / T105-2014).

[0074] Example 5

[0075] The apparatus is the same as in Embodiment 1, and the method is the same as in Embodiment 2, except that:

[0076] 1. The limestone ore used has a CaO content of 52.73% and contains a small amount of impurities such as dolomite and quartz.

[0077] 2. The preheating temperature for the first stage is 180℃ and the preheating time is 7 min; the preheating temperature for the second stage is 450℃ and the preheating time is 10 min; the preheating temperature for the third stage is 700℃ and the preheating time is 12 min.

[0078] 3. The temperature inside the suspension calcining furnace 7 is set to 1000℃, the calcination time is 10min, and the air flow velocity at the bottom of the suspension calcining furnace 7 is 15m / s.

[0079] 4. The cooling time for the first stage of cooling is 3 minutes, and the temperature of the powder after cooling is 800℃; the cooling time for the second stage of cooling is 8 minutes, and the temperature of the powder after cooling is 330℃; the cooling time for the third stage of cooling is 10 minutes, and the temperature of the powder after cooling is 90℃.

[0080] The CaO content in the highly active lime obtained in this example is 92.24%, and the activity is 406.72 mL (according to YB / T105-2014).

[0081] Example 6

[0082] The apparatus is the same as in Embodiment 1, and the method is the same as in Embodiment 2, except that:

[0083] 1. The limestone ore used has a CaO content of 53.05% and contains a small amount of impurities such as dolomite and quartz.

[0084] 2. The preheating temperature for the first stage is 150℃ and the preheating time is 5 min; the preheating temperature for the second stage is 500℃ and the preheating time is 8 min; the preheating temperature for the third stage is 750℃ and the preheating time is 10 min.

[0085] 3. The temperature inside the suspension calcining furnace 7 is set to 1050℃, the calcination time is 12min, and the air flow velocity at the bottom of the suspension calcining furnace 7 is 18m / s.

[0086] 4. The cooling time for the first stage of cooling is 5 minutes, and the temperature of the powder after cooling is 750℃; the cooling time for the second stage of cooling is 10 minutes, and the temperature of the powder after cooling is 300℃; the cooling time for the third stage of cooling is 12 minutes, and the temperature of the powder after cooling is 80℃.

[0087] The CaO content in the highly active lime obtained in this example is 92.86%, and the activity is 408.35 mL (according to YB / T105-2014).

[0088] Example 7

[0089] The apparatus is the same as in Embodiment 1, and the method is the same as in Embodiment 2, except that:

[0090] 1. The limestone ore used has a CaO content of 53.19% and contains a small amount of impurities such as dolomite and quartz.

[0091] 2. The preheating temperature for the first stage is 150℃ and the preheating time is 8 min; the preheating temperature for the second stage is 500℃ and the preheating time is 10 min; the preheating temperature for the third stage is 800℃ and the preheating time is 12 min.

[0092] 3. The temperature inside the suspension calcining furnace 7 is set to 1050℃, the calcination time is 10min, and the air flow velocity at the bottom of the suspension calcining furnace 7 is 20m / s.

[0093] 4. The cooling time for the first stage of cooling is 3 minutes, and the temperature of the powder after cooling is 850℃; the cooling time for the second stage of cooling is 10 minutes, and the temperature of the powder after cooling is 300℃; the cooling time for the third stage of cooling is 15 minutes, and the temperature of the powder after cooling is 80℃.

[0094] The CaO content in the highly active lime obtained in this example is 93.73%, and the activity is 423.35 mL (according to YB / T105-2014).

[0095] Example 8

[0096] The apparatus is the same as in Embodiment 1, and the method is the same as in Embodiment 2, except that:

[0097] 1. The limestone ore used has a CaO content of 52.56% and contains a small amount of impurities such as dolomite and quartz.

[0098] 2. The preheating temperature for the first stage is 200℃ and the preheating time is 5 min; the preheating temperature for the second stage is 470℃ and the preheating time is 8 min; the preheating temperature for the third stage is 780℃ and the preheating time is 12 min.

[0099] 3. The temperature inside the suspension calcining furnace 7 is set to 1050℃, the calcination time is 15min, and the air flow velocity at the bottom of the suspension calcining furnace 7 is 22m / s.

[0100] 4. The first stage of cooling takes 10 minutes, and the temperature of the powder after cooling is 750℃; the second stage of cooling takes 8 minutes, and the temperature of the powder after cooling is 350℃; the third stage of cooling takes 15 minutes, and the temperature of the powder after cooling is 80℃.

[0101] The CaO content in the highly active lime obtained in this example is 93.86%, and the activity is 426.52 mL (according to YB / T105-2014).

Claims

1. A method for preparing highly active lime using a suspension calcination system with CO2 partial pressure reduction function, comprising a pretreatment unit, a calcination unit, a cooling unit, a dust removal unit, a CO2 treatment unit, and a product silo; wherein the discharge end of the pretreatment unit is connected to the feed end of the calcination unit, the discharge end of the calcination unit is connected to the feed end of the cooling unit, the discharge end of the cooling unit is connected to the feed end of the product silo, the discharge end of the dust removal unit is connected to the feed end of the pretreatment unit, the air inlet of the pretreatment unit is connected to the air outlet of the CO2 treatment unit, the air outlet of the pretreatment unit is connected to the air inlet of the dust removal unit, the air inlet of the calcination unit is connected to the air outlet of the cooling unit, and the air outlet of the calcination unit is connected to the air inlet of the CO2 treatment unit; Its features are, Specifically, the following steps are included: Step 1. Preparation and preheating of limestone fine powder: After crushing the raw limestone ore to -1 mm, it is added to the limestone powder feed hopper and fed into the first-stage cyclone preheater through the conveying device for first-stage preheating. Then, the powder is fed into the second-stage cyclone preheater and the third-stage cyclone preheater in sequence for second-stage and third-stage preheating. Step 2. Limestone fine powder suspension calcination and separation: After three-stage preheating, the limestone powder is added to the suspension calcination furnace through the first feeder for calcination. The calcination time is 3-15 minutes. During the calcination process, air is introduced into the bottom of the suspension calcination furnace to ensure that the limestone powder added into the furnace is always in a suspended state. After calcination, part of the limestone powder is carried by the high-temperature gas and enters the cyclone separator through the first discharge port at the top of the suspension calcination furnace, while the other part enters the first-stage cyclone cooler through the second discharge port at the bottom of the calcination furnace. The high-temperature gas carrying part of the calcined product is separated by the cyclone separator. The hot gas enters the CO2 treatment equipment through the gas outlet above the cyclone separator. After treatment, it enters the third-stage cyclone preheater to provide heat for heat circulation. The limestone powder separated by the cyclone separator is sent to the first-stage cyclone cooler through the discharge port at the bottom of the cyclone separator. Step 3. Cooling of Calcinated Product: The limestone powder in the suspension calciner and cyclone separator is fed into the first-stage cyclone cooler for first-stage cooling. Hot air enters the cyclone separator through the upper outlet for heat recovery and separation. The powder after first-stage cooling enters the second-stage cyclone cooler through the outlet of the first-stage cyclone cooler for second-stage cooling. The gas in the second-stage cyclone cooler enters the first-stage cyclone cooler through the flue gas channel for heat exchange, accelerating the cooling of the powder. After the second cooling, the powder continues to be fed into the third-stage cyclone cooler for a third cooling, resulting in highly active lime. The third-stage cyclone cooler is connected to a fan, which continuously supplies cooling air through pipes to accelerate the entire cooling process. The cooling air in the third-stage cyclone cooler enters the second-stage cyclone cooler through the upper outlet to participate in heat exchange and improve the cooling efficiency of the second cooling process. Step 4. Storage of calcined products: The highly active lime obtained after three cooling cycles is fed into the product silo by a conveyor through the outlet of the third-stage cyclone cooler for storage. The CaO content in the highly active lime is ≥92%; according to YB / T042-2014, the activity is ≥360 mL. The CO2 processing unit of the system includes a CO2 processing device and a CO2 storage tank. The CO2 processing device has a first outlet on one side, a second outlet on the other side, and an inlet at the bottom. The inlet of the CO2 processing device is connected to the outlet of the cyclone separator of the calcination unit. The first outlet of the CO2 processing device is connected to the inlet of the third-stage cyclone preheater of the pretreatment unit. The second outlet of the CO2 processing device is connected to the inlet of the CO2 storage tank. The CO2 processing equipment specifically employs a device capable of separating and capturing CO2 from gas under high temperature and high pressure conditions, and also capable of collecting, compressing, and storing the captured CO2 gas.

2. The method for preparing highly active lime using a suspension calcination system with CO2 partial pressure reduction function according to claim 1, characterized in that, The pretreatment unit further includes a limestone powder feeding silo, a first-stage cyclone preheater, and a second-stage cyclone preheater. The outlet of the limestone powder feeding silo is connected to a feed port on one side of the first-stage cyclone preheater. The first-stage cyclone preheater has an air outlet at the top, a discharge port at the bottom, and an air inlet on the other side. The discharge port of the first-stage cyclone preheater is connected to a first feed port on one side of the second-stage cyclone preheater. The second-stage cyclone preheater has an air outlet at the top, an air inlet on one side, a second feed port on the other side, and a discharge port at the bottom. The air outlet of the second-stage cyclone preheater is connected to the air inlet of the first-stage cyclone preheater. The air inlet of the second-stage cyclone preheater is connected to the air outlet at the top of the third-stage cyclone preheater. The discharge port of the second-stage cyclone preheater is connected to a feed port on one side of the third-stage cyclone preheater. The third-stage cyclone preheater has an air inlet on one side and a discharge port at the bottom.

3. The method for preparing highly active lime using a suspension calcination system with CO2 partial pressure reduction function according to claim 2, characterized in that, The calcination unit includes a first feeder, an air supply device, and a suspension calcination furnace. The feed port of the first feeder is connected to the discharge port of the third-stage cyclone preheater, and the discharge port of the first feeder is connected to the feed port on one side of the suspension calcination furnace. The suspension calcination furnace has air inlets on both sides, an air outlet and a first discharge port at the top, and a second discharge port at the bottom. The air inlets on both sides of the suspension calcination furnace are connected to the air supply device. The air outlet and the first discharge port of the suspension calcination furnace are respectively connected to the first air inlet and the feed port on one side of the cyclone separator. The cyclone separator has an air outlet at the top and a discharge port and a second air inlet at the bottom.

4. The method for preparing highly active lime using a suspension calcination system with CO2 partial pressure reduction function according to claim 3, characterized in that, The cooling unit includes a first-stage cyclone cooler, a second-stage cyclone cooler, a third-stage cyclone cooler, and a fan; The first-stage cyclone cooler is provided with a first feed port and an air outlet at the top, a second feed port and an air inlet on one side, and an outlet at the bottom. The first feed port of the first-stage cyclone cooler is connected to the outlet of the cyclone separator, the air outlet of the first-stage cyclone cooler is connected to the second air inlet of the cyclone separator, and the second feed port of the first-stage cyclone cooler is connected to the outlet of the suspension calcining furnace. The second-stage cyclone cooler has an air outlet at the top, a feed inlet and an air inlet on one side, and a discharge outlet at the bottom. The air outlet of the second-stage cyclone cooler is connected to the air inlet of the first-stage cyclone cooler, and the feed inlet of the second-stage cyclone cooler is connected to the discharge outlet of the first-stage cyclone cooler. The third-stage cyclone cooler has an air outlet at the top, a feed inlet on one side, an air inlet on the other side, and a discharge outlet at the bottom. The air outlet of the third-stage cyclone cooler is connected to the air inlet of the second-stage cyclone cooler, the feed inlet of the third-stage cyclone cooler is connected to the discharge outlet of the second-stage cyclone cooler, the air inlet of the third-stage cyclone cooler is connected to the fan, and the discharge outlet of the third-stage cyclone cooler is connected to the product hopper. The third-stage cyclone cooler is connected to the product warehouse via a transport device, which is either a conveyor belt or a unloader.

5. The method for preparing highly active lime using a suspension calcination system with CO2 partial pressure reduction function according to claim 4, characterized in that, The dust removal unit includes a dust collector, an ash storage silo, a second feeder, and a chimney. The dust collector has an air inlet on one side, an air outlet on the other side, and a discharge outlet at the bottom. The air inlet of the dust collector is connected to the air outlet of the first-stage cyclone preheater, and the air outlet of the dust collector is connected to the air inlet of the chimney. The ash storage silo has a feed inlet at the top and a discharge outlet at the bottom. The feed inlet of the ash storage silo is connected to the discharge outlet of the dust collector, and the discharge outlet of the ash storage silo is connected to the feed inlet of the second feeder. The discharge outlet of the second feeder is connected to the second feed inlet of the second-stage cyclone preheater.

6. The method for preparing highly active lime using a suspension calcination system with CO2 partial pressure reduction function according to claim 1, characterized in that, In step 1, the CaO content in the limestone ore is ≥50%; the preheating temperature in the first-stage cyclone preheater is 100~200℃, and the preheating time is 5~10 min; the preheating temperature in the second-stage cyclone preheater is 300~500℃, and the preheating time is 8~10 min; the preheating temperature in the third-stage cyclone preheater is 600~800℃, and the preheating time is 10~15 min.

7. The method for preparing highly active lime using a suspension calcination system with CO2 partial pressure reduction function according to claim 1, characterized in that, In step 2, the air velocity introduced into the bottom of the suspension calcining furnace is 15~25 m / s; the temperature inside the suspension calcining furnace is set to 950~1050℃.

8. The method for preparing highly active lime using a suspension calcination system with CO2 partial pressure reduction function according to claim 1, characterized in that, In step 3, the cooling time for the first stage of cooling is 3 to 10 minutes, and the temperature of the cooled powder is 750 to 850°C; the cooling time for the second stage of cooling is 5 to 10 minutes, and the temperature of the cooled powder is 300 to 400°C; the cooling time for the third stage of cooling is 5 to 15 minutes, and the temperature of the cooled powder is 80 to 100°C.

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