Coal gangue suspension calcining system transformed by using cement clinker production line

Abstract

The invention belongs to the technical field of coal gangue suspension calcination, and particularly relates to a coal gangue suspension calcination system transformed by using a cement clinker production line, and a cement clinker production line transformation method comprises the following steps: disconnecting air inlet pipes from an existing penultimate cyclone preheater to an existing penultimate cyclone preheater; an air outlet pipeline of the existing decomposing furnace is connected with an air inlet pipe of the existing penultimate cyclone preheater; a blanking pipe of the existing penultimate cyclone preheater is connected with a feeding point of the decomposing furnace; and a blanking pipe of the existing penultimate cyclone preheater is connected to a feeding point of an air inlet pipe of the existing penultimate cyclone preheater. The invention provides a coal gangue suspension calcining system transformed by using a cement clinker production line.

Description

Technical Field

[0001] This invention belongs to the field of coal gangue suspension calcination technology, and particularly relates to a coal gangue suspension calcination system modified from a cement clinker production line. Background Technology

[0002] In 2021, my country's coal production reached 4 billion tons. Coal mining and coal preparation plant operations generate a large amount of coal gangue (approximately 15% of coal production). Coal gangue is typically discharged onto the ground as solid waste, occupying valuable land resources and causing underground seepage and spontaneous combustion, thus negatively impacting the environment. According to incomplete statistics, coal gangue accounts for about 20% of the country's industrial solid waste, and the cumulative amount of coal gangue stockpiled in my country currently exceeds 6 billion tons. Extensive exploration and practice have been conducted both domestically and internationally regarding the comprehensive utilization of coal gangue, forming a comprehensive treatment and utilization system encompassing power generation, road paving, building material production, chemical raw material production, agricultural applications, and underground backfilling. However, the comprehensive utilization rate of coal gangue is less than 30%.

[0003] In the field of building materials, there has been extensive research on the application of coal gangue, such as the production of manufactured sand and gravel aggregates or co-calcination with limestone as a cementing material. However, the disposal volume and application effect are both unsatisfactory. A feasible technological direction for the large-scale resource utilization of coal gangue is the calcination activation technology that transfers heat generated by fuel combustion to the coal gangue, decomposing the kaolinite (generally 40-60% content) into metakaolinite.

[0004] Kaolinite (Al₂O₃·2SiO₂·2H₂O, AS₂H₂) can be dehydrated at appropriate temperatures to form metakaolinite (Al₂O₃·2SiO₂, AS₂). Kaolinite has a layered silicate structure, with layers bonded by van der Waals bonds, where OH⁻ ions are firmly bound. When kaolinite is heated in air, it undergoes several structural changes. At approximately 300°C, the layered structure of kaolinite is destroyed due to dehydration, forming a poorly crystalline transition phase—metakaolinite. Because the molecular arrangement of metakaolinite is irregular, it exhibits a thermodynamically metastable state and, under appropriate stimulation, possesses cementitious properties. It can react with Ca(OH)₂(CH₂) and water to produce volcanic ash, generating hydration products similar to those in cement. Utilizing this characteristic, when used as a cement admixture, its reaction with the CH₂ produced during cement hydration can improve certain properties of the cement. Because the production cost of metakaolinite is lower than that of cement clinker, and the CO2 emissions during metakaolinite production are also lower than those during clinker production, its use as a substitute for clinker in the building concrete and cement industries is particularly attractive, especially given the active promotion of carbon reduction in these sectors. Furthermore, metakaolinite possesses physical properties such as low density, large specific surface area, and high oil absorption. Besides its applications in building concrete and cement additives, it can also replace pigments, plastic and rubber fillers, adsorbents, and 4A molecular sieves. It can be used as a raw material or filler in industries such as ceramics, papermaking, rubber, coatings, and petrochemicals, and its wide range of applications gives it higher economic value. Based on this background, the preparation of metakaolinite through calcination and activation of coal gangue has promising application prospects and high economic value.

[0005] Existing coal gangue calcination and activation technologies can be divided into two main categories based on the dispersion state of the coal gangue material in the hot gas flow: accumulated calcination and suspended calcination. Accumulated calcination typically uses granular or blocky coal gangue in a piled state within the calcination kiln. Due to the large particle size and the low thermal conductivity of the coal gangue, there are problems such as a small contact area between the material and the hot gas flow, resulting in low heat exchange efficiency. Furthermore, the large temperature difference between the inside and outside of the coal gangue block leads to over-burning on the outside and under-burning on the inside, severely affecting product quality and activity. Considering that kaolinite, the main active component in coal gangue, can generate highly active metakaolinite after dehydroxylation at appropriate temperatures, this reaction is endothermic. When the temperature rises to around 300℃, kaolinite begins to decompose endothermically to generate metakaolinite and water vapor. As the temperature further increases, the decomposition rate accelerates, and decomposition essentially ends above 800℃. The decomposition rate of coal gangue is mainly affected by factors such as calcination temperature and particle size. Studies have found that the larger the particle size of coal gangue, the lower the heat transfer efficiency between materials, thus slowing down the dehydroxylation reaction rate. Therefore, grinding coal gangue into powder for suspension calcination can effectively improve the rate of the dehydroxylation reaction, i.e., utilizing suspension preheating decomposition technology to complete the preheating and decomposition process of powdered coal gangue in a suspended state. Existing research shows that grinding coal gangue into powder for suspension calcination can effectively avoid the phenomenon of external over-burning and internal under-burning in the calcined coal gangue product.

[0006] Coal gangue contains a certain amount of kaolinite, which can be used as a raw material for the preparation of metakaolinite. Theoretically, metakaolinite can be prepared on a large scale through calcination and activation. However, coal gangue often contains a lot of combustible materials, which will release a certain amount of heat at high temperatures. When coal gangue is used as a raw material for the preparation of metakaolinite, the coal gangue will burn and release heat in the preheater system, which will lead to problems such as scaling and blockage in the preheater system.

[0007] Currently, suspension preheating and precalcination technology is widely used in my country's cement industry. Data shows that new dry-process cement clinker production equipment based on suspension preheating and precalcination accounts for over 95% of the market. However, due to the rapid development of the new dry-process cement industry and the increasingly saturated demand from large-scale infrastructure projects, overcapacity has gradually emerged in the domestic and international cement markets in recent years, leading to the shutdown or idlening of a considerable number of small-scale, energy-intensive new dry-process cement production lines.

[0008] The new dry-process cement clinker calcination system mainly includes a cyclone preheater, a decomposition furnace, a kiln tail flue, a rotary kiln, a kiln head burner, and a clinker cooler. For the specific production process flow, please refer to the attached instruction manual. Figure 1Raw meal powder, primarily composed of limestone powder, is fed into the preheater system from the top of a cyclone preheater. After gas-solid heat exchange in a multi-stage cyclone preheater, it enters the decomposition furnace for calcination via the feed pipe of the fourth-stage cyclone preheater in the suspension preheating system. Following gas-solid separation in the cyclone preheater, it enters the kiln tail flue chamber via the feed pipe of the fifth-stage cyclone preheater in the suspension preheating system. It then enters a rotary kiln for solid-phase reaction sintering to produce clinker. The high-temperature clinker is then cooled by a clinker cooler to obtain cement clinker. The high-temperature exhaust gas from the outlet of the first-stage cyclone preheater is partially heated by a waste heat recovery system before entering the raw meal grinding system to dry the raw meal. It then enters the flue gas treatment system and is finally discharged into the atmosphere through a chimney after further flue gas treatment.

[0009] It should be noted that raw meal powder with limestone as the main ingredient begins to decompose at 600℃. The decomposition rate accelerates with increasing temperature, reaching rapid decomposition at 800-850℃. Based on this, the decomposition temperature range of raw meal powder highly overlaps with that of kaolin powder.

[0010] However, the inventors of this application have discovered that the aforementioned prior art has at least the following technical problems: Due to the rapid development of the new dry process cement industry and the increasingly saturated demand from large-scale infrastructure projects, the overcapacity phenomenon in the domestic and international cement markets has gradually emerged in recent years, and a considerable number of small-scale, energy-intensive new dry process cement production lines have been shut down or left idle.

[0011] Considering the similarity of production processes, it may be possible and necessary to modify the existing new dry process cement clinker calcination system to meet the actual needs of preparing metakaolin from coal gangue suspension calcination, thereby opening up new product areas for cement production enterprises and creating significant economic and social benefits for enterprises while realizing the resource-based disposal of coal gangue solid waste.

[0012] The difficulty and significance of solving the above technical problems: Therefore, based on the above problems, it is of great practical significance to provide a coal gangue suspension calcination system that can make full use of the existing equipment of the new dry process cement clinker calcination system, and can produce highly active metakaolin products with only minor modifications, while solving the problems of high energy consumption and difficulty in controlling product quality in the metakaolin preparation system. Summary of the Invention

[0013] The purpose of this application is to provide a coal gangue suspension calcination system that utilizes a modified cement clinker production line to solve the technical problems in the prior art.

[0014] The technical solution adopted in this application embodiment to solve the technical problems existing in the prior art is as follows: A method for upgrading a cement clinker production line, the method comprising the following steps: Disconnect the air inlet pipe from the existing penultimate cyclone preheater to the existing penultimate cyclone preheater; The exhaust pipe of the existing decomposition furnace is connected to the inlet pipe of the existing penultimate cyclone preheater; The feed pipe of the existing fourth-to-last cyclone preheater is connected to the feed point of the decomposition furnace; The feed pipe of the existing penultimate cyclone preheater is connected to the feed point of the air inlet pipe of the existing penultimate cyclone preheater.

[0015] The embodiments of this application may also employ the following technical solutions: In the above-mentioned method for modifying a cement clinker production line, the existing penultimate cyclone preheater and the existing penultimate cyclone preheater are further configured as a first cyclone cooling system. The first cyclone cooling system is followed by a second cyclone cooling system, and the number of stages of the cyclone coolers in the second cooling system is one to four.

[0016] In the above-mentioned method for modifying a cement clinker production line, the exhaust pipe of the first cyclone cooling system is further connected to the decomposition furnace.

[0017] In the above-mentioned method for modifying a cement clinker production line, the outlet pipe of the second cyclone cooling system is further connected to the inlet pipe of the first cyclone cooling system, and the outlet pipe of the second cyclone cooling system is connected to the inlet pipe of the existing penultimate third-to-last cyclone preheater.

[0018] In the above-mentioned method for modifying cement clinker production lines, a further step is to implement a sealing and isolation treatment between the existing rotary kiln and the flue, or between the flue and the decomposition furnace cone.

[0019] In the above-mentioned method for upgrading a cement clinker production line, further, when the existing suspension preheating system is a five-stage system, the method for upgrading the cement clinker production line includes the following steps: Disconnect the air inlet pipe from the existing fourth-stage cyclone preheater to the existing third-stage cyclone preheater; The exhaust pipe of the existing decomposition furnace is connected to the inlet pipe of the existing third-stage cyclone preheater; The feed pipe of the existing second-stage cyclone preheater is connected to the feed point of the decomposition furnace; The feed pipe of the existing fourth-stage cyclone preheater is connected to the feed point of the air inlet pipe of the existing fifth-stage cyclone preheater.

[0020] A coal gangue suspension calcination system modified from a cement clinker production line, wherein the coal gangue suspension calcination system modified from a cement clinker production line is modified by any of the above-mentioned cement clinker production line modification methods.

[0021] In the aforementioned coal gangue suspension calcination system modified from a cement clinker production line, the coal gangue suspension calcination system modified from a cement clinker production line further includes: a suspension preheating system, a decomposition furnace system, a first cooling system, and a second cooling system connected in sequence; the air outlet pipe of the first-stage cyclone preheater is connected to a waste heat boiler; and the waste heat boiler is connected to a raw material mill and a flue gas treatment system.

[0022] A coal gangue suspension calcination system modified from a cement clinker production line, characterized in that: the coal gangue suspension calcination system modified from the cement clinker production line is obtained by the cement clinker production line modification method described above. The coal gangue suspension calcination system, which utilizes a modified cement clinker production line, comprises: a suspension preheating system, a decomposition furnace system, a first cooling system, and a second cooling system connected in sequence. The suspension preheating system is a three-stage system. The feed pipe of the second-stage cyclone preheater is connected to the feed point of the decomposition furnace, and the air outlet pipe of the decomposition furnace is connected to the air inlet pipe of the third-stage cyclone preheater. The first cooling system is a two-stage system. The fourth cyclone cooler is an existing fourth-stage cyclone preheater, and the fifth cyclone cooler is an existing fifth-stage cyclone preheater. The outlet duct of the fourth cyclone cooler is connected to the decomposition furnace. The second cooling system consists of four stages. The air outlet duct of the top-level cyclone cooler in the second cooling system is connected to the air inlet duct of the third-level cyclone preheater and the air inlet duct of the fifth cyclone cooler. A dust collector is installed on the air outlet duct of the top-level cyclone cooler of the second cooling system.

[0023] A method for calcining coal gangue using a modified cement clinker production line, characterized in that: the method employs a modified coal gangue calcination system.

[0024] One or more technical solutions provided in the embodiments of this application have at least the following beneficial effects: 1. The coal gangue suspension calcination system provided by this invention makes full use of the existing raw material grinding system, waste gas treatment system, waste heat utilization system, cyclone preheater, and decomposition furnace of the cement clinker production line. By making small and easy-to-implement modifications to the existing cement clinker calcination system, the system realizes the resource-based disposal and utilization of coal gangue, opening up new production areas for enterprises, effectively improving asset utilization, and bringing significant economic benefits to enterprises.

[0025] The main modifications to the existing firing system include: disconnecting the air inlet pipe from the fourth-stage cyclone preheater to the third-stage cyclone preheater in the existing firing system; modifying the existing decomposition furnace outlet pipe to connect it to the air inlet pipe of the third-stage cyclone preheater; adding a second cyclone cooling system to cool the high-temperature material exiting the fifth-stage cyclone preheater's feed pipe to the finished product temperature; modifying the existing feed pipe from the fourth-stage cyclone preheater to the decomposition furnace, adjusting it to the feed point on the existing fifth-stage cyclone preheater's air inlet pipe; modifying the existing feed pipe from the second-stage cyclone preheater to connect it to the feed point of the decomposition furnace; and sealing the connection between the existing kiln tail flue and the rotary kiln.

[0026] 2. The coal gangue suspension calcination system provided by this invention fully considers that coal gangue contains fixed carbon and other combustibles, which are prone to premature combustion and heat release during the preheating process, causing system crusting and blockage. Taking into account the heat exchange of coal gangue powder in the preheater and reducing the workload of modifying the existing calcination system, the design allows the coal gangue powder to enter the decomposition furnace system from the feed pipe of the second-stage cyclone preheater of the existing suspension preheating system after heat exchange.

[0027] This invention introduces a portion of the air from the top-level cyclone separator of the second cooling system into the decomposition furnace outlet duct, which can form a local cooling zone in the decomposition furnace outlet duct, thereby enabling flexible adjustment of the flue gas temperature entering the suspension preheating system and preventing premature combustion and heat release of coal gangue powder in the suspension preheating system.

[0028] 3. The coal gangue suspension calcination system provided by this invention organically integrates the processes of coal gangue powder preheating, decomposition, primary cooling, and secondary cooling. The entire preparation process of metakaolin is completed in a suspension state, significantly improving the system's thermal efficiency and effectively reducing system heat consumption. The suspension preheating, calcination, and cooling states ensure sufficient contact between the material and the flue gas, guaranteeing rapid preheating and cooling reactions. The calcination process allows for uniform and controllable temperature, avoiding the possibility of localized high temperatures leading to system crusting. Through reasonable system design, highly active metakaolin products can be prepared, while simultaneously solving problems such as high energy consumption and difficulty in controlling product quality in metakaolin preparation systems.

[0029] 4. This invention sequentially sets up a first cooling system (comprising a fourth-stage cyclone preheater and a fifth-stage cyclone preheater of the existing calcination system, a high-efficiency material spreading device, and connecting pipes, etc.) and a second cooling system from top to bottom. The two systems have clearly defined functional roles. Specifically, the first cooling system is used for the initial cooling of the calcined metakaolin. The pre-cooled metakaolin then enters the second cooling system and is cooled by air to the temperature required for subsequent production. The hot air, after heat exchange, enters the decomposition furnace system as a combustion medium to ensure stable combustion of the combustibles carried by the coal gangue within the decomposition furnace. If only the first or second cooling system is set up, it will face many disadvantages, such as incomplete combustion of combustibles, insufficient decomposition of kaolin, and the finished metakaolin product having an excessively high temperature that cannot meet the needs of subsequent production.

[0030] The first and second cooling systems employed in this invention enable complete combustion of combustibles in coal gangue, complete decomposition of kaolinite, and thorough cooling of the metakaolin product, effectively reducing system heat consumption and operating costs. Furthermore, a portion of the medium-temperature air (approximately 200-250°C) exiting the first cooling system is circulated back into the first cooling system via a circulating fan to cool the high-temperature metakaolin. This achieves full heat recovery and utilization; moreover, the air temperature after heat exchange is higher than that after directly cooling the high-temperature metakaolin with conventional air (approximately 20-30°C), which helps promote stable combustion and decomposition of coal gangue materials within the decomposition furnace system.

[0031] 5. This invention provides a sealed isolation between the existing rotary kiln and the smoke chamber, or between the smoke chamber and the decomposition furnace cone. The existing rotary kiln and cooler in the firing system will no longer be used. By sealing the rotary kiln and the smoke chamber or the smoke chamber and the decomposition furnace cone, the influence of the external environment on the system can be effectively avoided, ensuring the continuous and stable operation of the production system. Attached Figure Description

[0032] 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.

[0033] Figure 1 This is a schematic diagram of the structure of a novel dry-process cement clinker calcination system based on existing technology.

[0034] Figure 2 These are schematic diagrams of the structure of Embodiment 2 and process flow diagrams of Embodiment 3 of the present invention.

[0035] Figure 3 This is a structural schematic diagram of Embodiment 4 of the present invention. Detailed Implementation

[0036] This embodiment includes the following steps: disconnecting the inlet pipes from the existing penultimate cyclone preheater to the existing penultimate cyclone preheater; connecting the outlet pipe of the existing decomposition furnace to the inlet pipe of the existing penultimate cyclone preheater; connecting the discharge pipe of the existing penultimate cyclone preheater to the feed point of the decomposition furnace; and connecting the discharge pipe of the existing penultimate cyclone preheater to the feed point of the inlet pipe of the existing penultimate cyclone preheater. The existing penultimate cyclone preheater and the existing penultimate cyclone preheater form a first cyclone cooling system, followed by a second cyclone cooling system. The second cooling system has one to four stages of cyclone coolers. The outlet pipe of the first cyclone cooling system is connected to the decomposition furnace. The outlet pipe of the second cyclone cooling system is connected to the inlet pipe of the first cyclone cooling system, and the outlet pipe of the second cyclone cooling system is also connected to the inlet pipe of the existing penultimate cyclone preheater. A sealing partition is installed between the existing rotary kiln and the smoke chamber, or between the smoke chamber and the cone section of the decomposition furnace.

[0037] 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.

[0038] Example 1: This embodiment considers the high similarity between the production process of metakaolin from coal gangue suspension calcination and the production process of cement clinker from raw meal suspension calcination. It modifies the existing new dry-process cement clinker calcination system, making full use of the existing cement clinker production line's waste gas treatment system, raw meal grinding system, waste heat utilization system, cyclone preheater, and decomposition furnace. This is to meet the actual needs of metakaolin production from coal gangue suspension calcination, thereby opening up new product areas for cement production enterprises, creating significant economic benefits for enterprises, and simultaneously contributing to the achievement of carbon peaking and carbon neutrality goals.

[0039] The modification method for the existing calcination system of the cement clinker production line in this embodiment includes the following steps: First, disconnect the air inlet pipe from the fourth-stage cyclone preheater to the third-stage cyclone preheater in the existing calcination system, and modify the existing decomposition furnace outlet pipe to connect it to the air inlet pipe of the third-stage cyclone preheater; Second, add a second cyclone cooling system to cool the high-temperature material exiting the fifth-stage cyclone preheater discharge pipe to the finished product temperature; Third, modify the existing discharge pipe from the fourth-stage cyclone preheater to the decomposition furnace, adjusting it to the feed point on the existing fifth-stage cyclone preheater inlet pipe; Finally, modify the existing discharge pipe of the second-stage cyclone preheater to connect it to the feed point of the decomposition furnace.

[0040] Example 2: In this embodiment, as per the appendix to the specification... Figure 2As shown, the suspension preheating system of the coal gangue suspension calcination system transformed from a cement clinker production line includes first, second, and third cyclone preheaters, a high-efficiency material spreading device, and connecting pipes.

[0041] The decomposition furnace system includes a high-efficiency feeding device, hot air inlet pipes, burners arranged in the cone and column sections of the decomposition furnace (the burners may or may not be used depending on the calorific value of the coal gangue raw material), and flue gas outlet pipes, etc.

[0042] The first cooling system includes the fourth and fifth cyclone preheaters (used as cyclone coolers in this embodiment), a high-efficiency material spreading device, and connecting pipes, etc.

[0043] The second cooling system includes the sixth and seventh cyclone coolers, a high-efficiency material spreading device, and connecting pipes.

[0044] The connection between the existing kiln tail smoke chamber and the decomposition furnace is sealed by installing a partition wall.

[0045] This embodiment utilizes a coal gangue suspension calcination system modified from a cement clinker production line. It makes full use of the existing equipment in the new dry-process cement clinker calcination system and only requires minor modifications to produce highly active metakaolin products. At the same time, it solves the problems of high energy consumption and difficulty in controlling product quality in the metakaolin preparation system.

[0046] Example 3: In this embodiment, as per the appendix to the specification... Figure 2 As shown, the coal gangue suspension calcination method modified from a cement clinker production line includes the following process flow: In terms of material flow, after the raw material pretreatment process, the coal gangue raw material enters the grinding system to obtain coal gangue powder that meets production needs. The coal gangue powder is then fed into the suspension preheating system via a feeding device using an elevator.

[0047] The suspension preheating system includes a three-stage cyclone preheater, a high-efficiency material spreading device, and connecting pipes. Coal gangue powder undergoes preheating and gas-solid separation within the cyclone preheater. After heat exchange and gas-solid separation, the coal gangue powder enters the decomposition furnace system through the discharge pipe of the second-stage cyclone preheater in the suspension preheating system. (Existing idle new dry-process cement clinker production lines mostly use single-series five-stage preheaters. Considering that coal gangue contains fixed carbon and other combustibles, which are prone to premature combustion and heat release during preheating, causing system scaling and blockage, and taking into account the heat exchange of coal gangue powder in the preheater and reducing the workload of modifying the existing calcination system, the preferred design is to have the material enter the decomposition furnace system through the discharge pipe of the existing second-stage cyclone preheater in the suspension preheating system.)

[0048] Multiple temperature measuring points are set up in layers along the height of the decomposition furnace to monitor the temperature distribution inside the furnace in real time. By adjusting the amount of material fed into the decomposition furnace and the system air supply, the temperature distribution inside the decomposition furnace is controlled within a reasonable range. A reasonable temperature distribution inside the decomposition furnace can promote the complete combustion of combustibles such as fixed carbon contained in the coal gangue and the complete decomposition of minerals such as kaolinite contained in the coal gangue, while ensuring that minerals such as kaolinite are not overburned. The activity of the finished kaolinite meets the requirements of subsequent production. The combustion of combustibles in the decomposition furnace system releases a large amount of heat for the decomposition of minerals such as kaolinite. The decomposed hot material leaves the decomposition furnace system and then enters the first cooling system after gas-solid separation with the hot flue gas in the lowest stage cyclone preheater of the suspension preheating system (which is the third stage cyclone preheater of the existing calcination system).

[0049] The preferred calcination temperature in the decomposition furnace system is 650~1000℃. The preferred residence time of the gas in the decomposition furnace system is 2~10 seconds.

[0050] The first cooling system consists of the existing fourth-stage cyclone preheater, fifth-stage cyclone preheater, high-efficiency material spreading device, and connecting pipes. Hot material undergoes rapid cooling and gas-solid separation within the cyclone cooler of the first cooling system. After rapid cooling in the first cooling system, the material, after gas-solid separation, enters the newly added second cooling system through the discharge pipe of the cyclone cooler in the first cooling system.

[0051] The newly added second cooling system includes one or more cyclone coolers, a high-efficiency material spreading device, and connecting pipes. The material is further cooled and separated into gas and solid states within the cyclone coolers of the second cooling system, and finally exits from the discharge pipe of the lowest-level cyclone cooler (the seventh cyclone cooler) of the second cooling system, falling into the finished product zipper machine to obtain the desired finished product.

[0052] The preferred number of stages for the cyclone cooler in the second cooling system is one to four.

[0053] To avoid the risk of material collapse caused by sudden power outages or other malfunctions during production, emergency buffer chambers are installed at the bottom of the air inlets of the first and second cooling systems. When the system suddenly loses power or other malfunctions, the valves on the emergency buffer chambers open, and the finished kaolin is unloaded into the finished product zipper machine through the emergency buffer chambers, ensuring system safety.

[0054] In terms of gas flow direction Ambient temperature air enters the second cooling system, subsequently cooling the material entering the system. The air, having completed heat exchange, exits from the outlet of the top-level cyclone cooler (sixth cyclone cooler) in the second cooling system, and then enters a dust collector for dust removal. The dust-treated air is divided into two paths: one path connects to the outlet duct of the decomposition furnace, creating a localized cooling zone within the duct to flexibly adjust the temperature of the flue gas entering the suspension preheating system, preventing premature combustion and heat release from the coal gangue powder in the suspension preheating system. The second path enters the inlet duct of the cyclone cooler in the first cooling system, subsequently cooling the hot material entering the first cooling system.

[0055] The air that has undergone heat exchange enters the decomposition furnace system. The flue gas formed by fuel combustion and decomposition of minerals such as kaolinite leaves the decomposition furnace system and enters the suspension preheating system. Subsequently, the coal gangue powder fed into the suspension preheating system undergoes multiple preheating and gas-solid separation processes. Finally, it exits from the outlet of the uppermost cyclone preheater (first cyclone preheater) of the suspension preheating system. The high-temperature waste gas discharged from the outlet of the first cyclone preheater recovers part of its heat through the waste heat recovery system and then enters the raw material grinding system to dry the raw material. After that, it enters the flue gas treatment system and is finally discharged into the atmosphere through the chimney after flue gas treatment.

[0056] The principle of this invention is as follows: Within the optimal calcination temperature range of the decomposition furnace system, minerals such as kaolinite can be fully decomposed to form metakaolin, while avoiding the crystallization and loss of activity of metakaolin. Considering the similarity of the production process, this system makes full use of the existing waste gas treatment system, waste heat utilization system, raw material grinding system, cyclone preheater, and decomposition furnace of the cement clinker production line.

[0057] Meanwhile, considering that the air temperature at the top cyclone separator of the second cooling system is relatively high and the air volume is relatively large, in order to reduce the overall heat consumption of the system, this invention circulates a portion of the air (the amount of air is sufficient to ensure normal combustion of combustibles in the decomposition furnace system) from the top cyclone separator of the second cooling system into the cyclone cooler of the first cooling system, thereby realizing the utilization of the waste heat of this portion of air.

[0058] Finally, considering that coal gangue contains fixed carbon and other combustibles, which are prone to premature combustion and heat release during the preheating process, causing system crusting and blockage, this invention introduces a portion of the air from the top-level cyclone separator of the second cooling system into the decomposition furnace outlet duct. This creates a localized cooling zone in the decomposition furnace outlet duct, enabling flexible adjustment of the flue gas temperature entering the suspension preheating system and preventing premature combustion and heat release of coal gangue powder in the suspension preheating system.

[0059] Example 4: Since metakaolin prepared by suspension calcination does not need to be sintered in a rotary kiln, the connection between the existing kiln tail smoke chamber and the rotary kiln or decomposition furnace needs to be sealed. The sealing treatment scheme includes, but is not limited to, steel plate welding sealing, partition wall sealing, etc.

[0060] In this embodiment, as per the appendix to the specification... Figure 3 As shown, a partition is provided between the kiln tail flue and the rotary kiln. The original tertiary air duct, rotary kiln, kiln head burner and cooler can be dismantled and resold or moved to other suitable clinker production lines as needed.

[0061] In summary, this invention provides a coal gangue suspension calcination system that utilizes a modified cement clinker production line.

[0062] 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 method of revamping a cement clinker production line, characterized in that: The cement clinker production line modification method comprises the following steps: disconnecting the air inlet pipe of the existing fourth stage cyclone preheater to the existing third stage cyclone preheater; connecting the air outlet pipe of the existing decomposing furnace to the air inlet pipe of the existing third stage cyclone preheater; connecting the air outlet pipe of the existing decomposing furnace to the air inlet pipe of the existing third stage cyclone preheater; connecting the air outlet pipe of the existing decomposing furnace to the air inlet pipe of the existing third stage cyclone preheater; 2. The cement clinker production line revamping method according to claim 1, characterized in that: The existing second stage cyclone preheater and the existing first stage cyclone preheater serve as a first cyclone cooling system, which is followed by a second cyclone cooling system, and the number of stages of the cyclone coolers of the second cooling system is one to four.

3. The cement clinker production line revamping method according to claim 2, characterized in that: The air outlet pipe of the first cyclone cooling system is connected to the decomposing furnace.

4. The cement clinker production line revamping method according to claim 2, characterized in that: The air outlet pipe of the second cyclone cooling system is connected to the air inlet pipe of the first cyclone cooling system and the air inlet pipe of the existing third stage cyclone preheater.

5. The cement clinker production line revamping method according to claim 1, characterized in that: A sealing and partitioning treatment is performed between the existing rotary kiln and the flue chamber, or between the flue chamber and the conical part of the decomposing furnace.

6. The cement clinker production line revamping method according to claim 1, characterized in that: When the existing suspension preheating system has five stages, the cement clinker production line modification method comprises the following steps: disconnecting the air inlet pipe of the existing fourth stage cyclone preheater to the existing third stage cyclone preheater; connecting the air outlet pipe of the existing decomposing furnace to the air inlet pipe of the existing third stage cyclone preheater; connecting the air outlet pipe of the existing decomposing furnace to the air inlet pipe of the existing third stage cyclone preheater; connecting the air outlet pipe of the existing decomposing furnace to the air inlet pipe of the existing third stage cyclone preheater; 7. A coal gangue suspension calcining system using cement clinker production line reconstruction, characterized in that: The coal gangue suspension calcining system modified by using the cement clinker production line is modified by the cement clinker production line modification method of any one of claims 1-5.

8. The coal gangue suspension calcining system modified by cement clinker production line according to claim 7, characterized in that: The coal gangue suspension calcining system modified by using the cement clinker production line comprises a suspension preheating system, a decomposing furnace system, a first cooling system and a second cooling system connected in sequence, the air outlet pipe of the first stage cyclone preheater is connected to a waste heat boiler, and the waste heat boiler is connected to a raw material mill and a flue gas treatment system.

9. A coal gangue suspension calcining system using cement clinker production line reconstruction, characterized in that: The coal gangue suspension calcining system modified by using the cement clinker production line is modified by the cement clinker production line modification method of claim 6: The coal gangue suspension calcining system modified by using the cement clinker production line comprises a suspension preheating system, a decomposing furnace system, a first cooling system and a second cooling system connected in sequence, the suspension preheating system has three stages, the air outlet pipe of the second stage cyclone preheater is connected to the air inlet pipe of the third stage cyclone preheater, the first cooling system has two stages, the fourth cyclone cooler is the existing fourth stage cyclone preheater, the fifth cyclone cooler is the existing fifth stage cyclone preheater, the air outlet pipe of the fourth cyclone cooler is connected to the decomposing furnace, the second cooling system has one to four stages, the air outlet pipe of the uppermost stage cyclone cooler of the second cooling system is connected to the air inlet pipe of the third stage cyclone preheater and the air inlet pipe of the fifth cyclone cooler, and a dust collector is arranged on the air outlet pipe of the uppermost stage cyclone cooler of the second cooling system.

10. A coal gangue suspension calcining method using cement clinker production line modification, characterized in that: The coal gangue suspension calcining method using the cement clinker production line transformation adopts the coal gangue suspension calcining system using the cement clinker production line transformation according to claim 7.

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