Low-energy-consumption coal gangue suspended state activation calcination process and system

Abstract

The invention relates to the technical field of coal gangue suspended state activation and calcination, in particular to a low-energy-consumption coal gangue suspended state activation and calcination process and system.The low-energy-consumption coal gangue suspended state activation and calcination system comprises a calcination furnace system and a quartic air pipe, and one end of the quartic air pipe is connected with the bottom of a calcination furnace of the calcination furnace system; a local mixing area is formed at the bottom of the calcining furnace, the other end of the calcining furnace is connected with a kiln door cover of an existing sintering system, and a valve is arranged on the quartic air pipe. The invention provides a low-energy-consumption coal gangue suspended state activation calcination process and system.

Description

Technical Field

[0001] The invention relates to the technical field of suspended activated calcination of coal gangue, and in particular to a low-energy-consumption suspended activated calcination process and system for coal gangue. Background Art

[0002] A lot of exploration and practice have been carried out at home and abroad on the comprehensive utilization of coal gangue, forming a comprehensive processing and utilization system for power generation, road paving, production of building materials, production of chemical raw materials, agricultural applications and underground filling. However, the comprehensive utilization rate of coal gangue is less than 30%.

[0003] In the field of building materials, extensive research has been conducted on the use of coal gangue, such as making it into machine-made sand and gravel aggregate or calcining it with limestone as a cementitious material. However, the disposal volume and effectiveness of its use have been limited. Activated calcination technology, in which the heat released by fuel combustion is transferred to the gangue, decomposing the kaolinite (typically 40-60%) contained in it into metakaolinite, is a viable technology for large-scale resource utilization of coal gangue.

[0004] Kaolinite (Al2O3·2SiO2·2H2O, AS2H2) dehydrates at appropriate temperatures to form metakaolinite (Al2O3·2SiO2, AS2). Kaolinite has a layered silicate structure, with layers held together by van der Waals bonds, where OH- ions are firmly bound. When heated in air, kaolinite undergoes several structural changes. At approximately 300°C, dehydration destroys the layered structure, forming a transitional phase with poor crystallinity—metakaolinite. Due to its irregular molecular arrangement and thermodynamically metastable state, metakaolinite exhibits gelling properties when properly stimulated. It reacts with Ca(OH)2(CH4) and water to form a hydration product similar to cement. This characteristic can be exploited when used as a cement admixture, where it reacts with CH4 produced during cement hydration, improving certain cement properties. Since the preparation cost of metakaolin is lower than that of cement clinker, and CO2 emissions during its preparation are also lower than those during clinker preparation, the use of metakaolin as a substitute for clinker in these industries is particularly attractive given the ongoing efforts to reduce carbon emissions in the construction concrete and cement industries. Furthermore, metakaolin exhibits physical properties such as low density, large specific surface area, and high oil absorption. Besides being used as a concrete and cement additive, 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. This wide range of applications gives it high economic added value. Given this background, the preparation of metakaolin by calcining activated coal gangue offers promising application prospects and high economic added value.

[0005] Existing gangue calcination and activation technologies can be divided into two categories based on the dispersion state of the gangue material in the hot gas flow: bulk activation calcination and suspended activation calcination. Bulk activation calcination generally uses granular or lumpy gangue in a piled state in the calcination kiln. Due to the large particle size and low thermal conductivity of the gangue, the contact area between the material and the hot gas flow is small, resulting in low heat exchange efficiency. Furthermore, the large temperature difference between the inside and outside of the gangue block can lead to overburning on the outside and underburning on the inside, seriously affecting product quality and activity. Considering that kaolinite, the main active component in gangue, can produce highly active metakaolinite after dehydroxylation at appropriate temperatures, this reaction is endothermic. When the temperature rises to around 300°C, kaolinite begins to decompose into metakaolinite and generate water vapor. The decomposition rate accelerates as the temperature rises, and decomposition is essentially complete above 800°C. The decomposition reaction rate of gangue is primarily affected by factors such as calcination temperature and particle size. Studies have found that larger gangue particle size reduces the heat transfer efficiency between materials, resulting in a slower dehydroxylation reaction. Therefore, grinding gangue into a powder and calcining it in a suspended state can effectively increase the rate of the dehydroxylation reaction. This involves utilizing a suspended preheating decomposition technique to preheat and decompose the powdered gangue in a suspended state. Existing research indicates that grinding gangue into a powder and calcining it in a suspended state can effectively prevent the phenomenon of overburning the exterior and underburning the interior of the finished calcined gangue product.

[0006] Coal gangue contains a certain amount of kaolinite, which can be used as a raw material for the preparation of metakaolin. Theoretically, metakaolin can be prepared on a large scale through calcination and activation. However, coal gangue often contains more combustible substances, which will release a certain amount of heat at high temperatures. When coal gangue is used as a raw material for the preparation of metakaolin, the coal gangue will burn and release heat in the preheater system, which will cause problems such as crusting and blockage in the preheater system. Summary of the Invention

[0007] The purpose of this application is to provide a low-energy consumption coal gangue suspended activation calcination process and system in order to solve the technical problems in the prior art.

[0008] The technical solutions adopted by the embodiments of the present application to solve the technical problems existing in the known technologies are: A low-energy-consumption coal gangue suspended activation calcination system, the low-energy-consumption coal gangue suspended activation calcination system comprising: a calcination furnace system and a quaternary air duct, one end of the quaternary air duct being connected to the bottom of the calcination furnace of the calcination furnace system to form a local mixing area at the bottom of the calcination furnace, and the other end being connected to the kiln door cover or tertiary air duct or cooler of the existing firing system, and the quaternary air duct being provided with a valve.

[0009] The embodiments of the present application may also adopt the following technical solutions: In the above-mentioned low-energy consumption coal gangue suspension activation calcination system, further, the low-energy consumption coal gangue suspension activation calcination system also includes a first cooling system and a second cooling system, the first cooling system is one to two levels, and the second cooling system is one to two levels.

[0010] In the above-mentioned low-energy consumption coal gangue suspended activation calcination system, further, the low-energy consumption coal gangue suspended activation calcination system also includes a suspended preheating system, the suspended preheating system is one to three levels, and a feeding point is provided at the air inlet pipe of the first cyclone preheater of the suspended preheating system, the discharge pipe of the penultimate cyclone preheater of the suspended preheating system is connected to the calcining furnace, and the discharge pipe of the lowest cyclone preheater of the suspended preheating system is connected to the air inlet pipe of the first cooling system.

[0011] In the above-mentioned low-energy consumption coal gangue suspension activation calcination system, further, the air outlet pipe of the first cyclone preheater of the suspension preheating system is connected to the suspension preheating system of the existing firing system.

[0012] In the above-mentioned low-energy consumption coal gangue suspended activation calcination system, further, the outlet pipe of the second cooling system is respectively connected to the waste heat utilization system of the firing system and the air inlet pipe of the first cooling system, and a valve is provided on the circulating air pipe between the second cooling system and the first cooling system.

[0013] In the above-mentioned low-energy consumption coal gangue suspended activated calcination system, further, the firing system includes a preheater, a decomposition furnace, a rotary kiln and a cooler connected in sequence, and the two ends of the tertiary air duct are respectively connected to the decomposition furnace and the cooler; the air outlet duct of the preheating system is connected to the waste heat utilization system through a waste heat boiler and a high-temperature fan, and the waste heat utilization system is a raw mill, and the waste heat utilization system, the dust collection system and the flue gas treatment system are connected in sequence.

[0014] A low-energy consumption coal gangue suspension activation calcination process, the low-energy consumption coal gangue suspension activation calcination process comprising the following steps: Step 1: Extract the high-temperature quaternary air from the existing firing system into the calcining furnace system.

[0015] In the above-mentioned low-energy consumption coal gangue suspension activation calcination process, further, the step 1 is: When the calorific value of coal gangue is 300~700kcal / kg, extract the high-temperature quaternary air of the existing firing system into the calcining furnace system, and reduce the extraction amount after the system stabilizes; When the calorific value of coal gangue is lower than 300kcal / kg, the high-temperature quaternary air of the existing firing system is extracted to enter the calcining furnace system; When the calorific value of coal gangue is higher than 700kcal / kg, the high-temperature fourth air of the existing firing system is extracted into the calciner system, and after the system stabilizes, the extraction amount is reduced and the air volume entering the first cooling system is increased or the output of the calciner system is reduced.

[0016] In the above-mentioned low-energy consumption coal gangue suspension activation calcination process, further, the calcination temperature of the calcination furnace is 650-1000° C., and the residence time of the gas in the calcination furnace system is 2-10 seconds.

[0017] In the above-mentioned low-energy consumption coal gangue suspended activation calcination process, further, the high-temperature fourth air temperature is 850~1050℃.

[0018] One or more technical solutions provided in the embodiments of this application have at least the following beneficial effects: 1. The present invention fully considers the characteristics of the existing cement clinker production process and the activated calcination of coal gangue. A quaternary air duct is newly added to the kiln door cover, tertiary air duct or cooler of the existing firing system. During the operation of the activated calcination system of coal gangue, part of the high-temperature quaternary air of the existing cement kiln system is extracted to enter the newly added calcination furnace system. This part of the high-temperature quaternary air has two functions: first, it serves as a heat source for the decomposition of kaolinite in the coal gangue and as combustion air for the combustion of combustibles in the coal gangue; second, it preheats the combustion air entering the calcination furnace system to a reasonable temperature of 600-800°C.

[0019] The fully preheated combustion air enters the calciner system, ensuring the complete decomposition of kaolinite in the gangue and the complete combustion of combustibles within the calciner system. The flue gas generated by the decomposition of kaolinite in the gangue and the combustion of fuel within the calciner system is separated into gas and solids by the cyclone separator at the calciner system outlet, fully preheating the gangue raw meal. The flue gas then enters the existing firing system, undergoing multiple preheating and gas-solid separations for the raw meal fed into the suspension preheating system, before ultimately exiting the air outlet of the top-stage cyclone preheater in the existing firing system's suspension preheating system.

[0020] By adopting the above-described process and method, a portion of the high-temperature quaternary air from the cement clinker production line is fully utilized to enter the calciner system during the charging period to assist combustion and stabilize combustion. The high-temperature flue gas generated by the calciner system can then preheat the coal gangue raw meal powder in the suspension calcination system and the low-temperature raw meal from the existing cement clinker production line, thereby fully recovering and utilizing heat while reducing the energy consumption of the existing firing system. Furthermore, the flue gas with fully recovered heat can also be used in the existing cement clinker production line exhaust gas treatment system.

[0021] 2. The present invention rationally designs the suspended calcining system so that it has good adaptability to coal gangue raw materials with different calorific value ranges. Specifically, the most suitable raw materials for the present invention are coal gangue with low and medium calorific values ​​(the calorific value of coal gangue itself is considered to be 300~700kcal / kg). The heat contained in the coal gangue itself can meet the heat demand for the decomposition of kaolinite in the coal gangue. The calcining furnace system of this application does not require additional fuel. The high-temperature quaternary air is continuously used during the charging of the calcining furnace system, and the extraction amount of the high-temperature quaternary air can be adjusted in real time through the valve according to the operation of the calcining furnace system. Specifically: in the initial stage of charging the calcining furnace system, the high-temperature quaternary air is used to act as combustion air and stabilize combustion; when the calcining furnace system is stably operating, the valve provided on the quaternary air duct can be used to reduce the supply of high-temperature quaternary air. At this time, the high-temperature quaternary air is only used to preheat the combustion air entering the calcining furnace system to 600~800℃. This design condition can realize the resource utilization of coal gangue and the calciner system does not need additional fuel supply.

[0022] When the calorific value of the gangue is lower than 300kcal / kg, the design of the present application maintains a continuous supply of high-temperature quaternary air. When the calorific value of the gangue is higher than 700kcal / kg, the design of the present application increases the air volume entering the first cooling system or reduces the output of the calcining furnace system.

[0023] 3. Existing technologies fail to consider the production reality of raw materials containing combustibles, resulting in the gangue material releasing a large amount of heat during the suspension preheating process, causing crusting and blockage in the preheater system, thus affecting the stable operation of the system. The present invention adopts reasonable process technology to produce highly active calcined gangue with low energy consumption and high efficiency, and avoids the problem of large-scale heat release of combustibles in the gangue in the preheater, which causes crusting and blockage in the system and thus prevents the stable operation of the production line. This enables the large-scale production and widespread application of calcined gangue and calcined gangue-limestone composite cement.

[0024] 4. By rationally designing the number of preheater stages and the flue gas temperature at the calciner system's outlet, this invention ensures that the preheated gangue material temperature is below the intense combustion temperature range. Furthermore, after sufficient preheating, the gangue material enters the calciner system as quickly as possible for combustion and decomposition reactions, reducing system heat consumption while avoiding heat release from combustion within the preheater. Furthermore, the preheated gangue temperature remains within an optimal range, enabling rapid and stable combustion of combustible materials and the complete decomposition of minerals such as kaolinite in a high-temperature, fourth-order air environment.

[0025] 5. The present invention sets up a first cooling system and a second cooling system in sequence from top to bottom, and the two systems have clear functional positioning. Among them: the first cooling system is used to preliminarily cool the calcined metakaolinite, and the preliminarily cooled metakaolinite enters the second cooling system and is air-cooled to the temperature required for subsequent production; the hot air after heat exchange is further preheated to 600~800℃ by high-temperature quaternary air and then enters the calcination furnace system to provide stable combustion of the combustibles carried by the gangue in the calcination furnace. If only the first cooling system or the second cooling system is set, there will be many unfavorable situations such as incomplete combustion of combustibles, insufficient decomposition of kaolinite, and the temperature of the finished metakaolinite product is too high to meet the needs of subsequent production. The first cooling system and the second cooling system adopted by the present invention can achieve full combustion of combustibles in the gangue, full decomposition of kaolinite, and full cooling of the finished metakaolinite product, which can effectively reduce the heat consumption and investment cost of the system.

[0026] 6. In this invention, a portion of the medium-temperature air (approximately 200-250°C) exiting the first cooling system is circulated through a circulating fan into the first cooling system to cool the high-temperature metakaolinite. This allows for efficient heat recovery and utilization. Furthermore, the air temperature after heat exchange is higher than that obtained by directly cooling the high-temperature metakaolinite with conventional air (approximately 20-30°C), promoting stable combustion and decomposition of the gangue within the calciner system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The following will further describe the technical solutions of the embodiments of the present application in conjunction with 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 the present application. In addition, unless otherwise specified, these drawings are intended only to conceptually illustrate the structures described herein and are not necessarily drawn to scale.

[0028] Figure 1 It is a process flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0029] This embodiment includes Figure 1 The process flow shown: In terms of material flow: Gangue raw material containing kaolinite and a certain calorific value first enters a drying and crushing machine, where it is dried and crushed to produce gangue powder particles that meet production requirements. These particles are then fed into a suspension preheating system via a feeding device and a feeding point. The suspension preheating system comprises a cyclone preheater, a high-efficiency spreading device, and connecting pipes. The gangue powder undergoes preheating and gas-solid separation in the cyclone preheater. After heat exchange and gas-solid separation, the raw meal enters the calcining furnace system through the discharge pipe of the cyclone preheater in the suspension preheating system.

[0030] The calcining furnace system includes a high-efficiency material spreading device, a hot air inlet pipe, and a flue gas outlet pipe, etc. Multiple temperature measuring points are layered in the height direction of the calcining furnace to monitor the temperature distribution in the calcining furnace in real time. The temperature distribution in the calcining furnace is controlled within a reasonable range by adjusting the amount of material and flue gas fed into the calcining furnace system. Reasonable temperature distribution in the calcining furnace can ensure the complete combustion of combustible materials in the gangue and the complete decomposition of kaolinite, while ensuring that the gangue is not overburned and the activity of the finished kaolinite meets the requirements of subsequent production. The heat released by the combustion of the gangue in the calcining furnace system and the heat carried by the hot air entering the calcining furnace system are used to decompose the kaolinite in the gangue. The decomposed hot material leaves the calcining furnace system and then enters the first cooling system after gas-solid separation with the hot flue gas in the lowest-level cyclone preheater of the suspension preheating system.

[0031] The calciner system combines the gangue composition (mainly kaolinite content) and its own calorific value. Through the adoption of reasonable design, the system can achieve stable operation without the need for external fuel supply. The system heat demand can be met only by the inherent calorific value of the gangue and the high-temperature air entering the calciner system through the first cooling system.

[0032] The first cooling system includes one or more cyclone coolers, a high-efficiency material spreading device, and connecting pipes. The hot material is rapidly cooled and undergoes gas-solid separation in the cyclone coolers of the first cooling system. After rapid cooling in the first cooling system, the material undergoes gas-solid separation and enters the second cooling system from the lowest cyclone cooler of the first cooling system.

[0033] The secondary cooling system includes one or more cyclone coolers, a high-efficiency material spreading device, and connecting pipes. The material undergoes further cooling and gas-solid separation within the cyclone coolers of the secondary cooling system, ultimately exiting through the discharge pipe of the lowest cyclone cooler in the secondary cooling system and falling into the finished zipper machine, ultimately producing a finished product that meets the requirements.

[0034] In terms of gas flow direction: In this embodiment, there are two gas sources.

[0035] The first path of normal temperature air enters the second cooling system, and then cools the materials entering the second cooling system. The air that has completed heat exchange leaves from the outlet of the uppermost cyclone cooler of the second cooling system, and is divided into two paths after passing through the circulating fan: one path enters the lowermost cyclone cooler of the first cooling system, and then cools the hot materials entering the first cooling system. The air that has completed heat exchange enters the calcining furnace system through the bottom of the calcining furnace system; the other path enters the high-temperature fan outlet pipe of the existing firing system, and then enters the waste heat utilization system for waste heat recovery and utilization, and then is discharged into the atmosphere after being treated by the dust collection system and the flue gas treatment system.

[0036] The second route is high-temperature quaternary air entering the calciner system through a newly added quaternary air duct. This high-temperature quaternary air enters the bottom of the calciner system through a valve installed on the connecting pipe, and the valve opening is adjusted to control the quaternary air volume entering the calciner system. The high-temperature quaternary air from the existing firing system enters the calciner system through the quaternary air duct as combustion air and an external heat source during the initial charging of the calciner system. This promotes the complete combustion of combustibles such as fixed carbon contained in the gangue and the complete decomposition of minerals such as kaolinite contained in the gangue within the calciner system. Furthermore, the heat contained in the high-temperature quaternary air preheats the combustion air entering the calciner system to a suitable temperature of 600-800°C, which ensures the full decomposition of minerals and combustion of combustibles within the calciner system.

[0037] When the raw material is low- or medium-calorific gangue (the intrinsic calorific value of gangue is considered to be 300-700 kcal / kg), the gangue composition (primarily kaolinite content) and intrinsic calorific value meet the requirements. The gangue's inherent heat can meet the heat demand for kaolinite decomposition, eliminating the need for additional fuel and requiring only a small supply of high-temperature quaternary air. In this case, the valve on the quaternary air duct can be adjusted in real time based on the calciner's operating conditions. When the calciner system is operating stably (based on the calciner's operating conditions, generally 1-3 hours after adding materials), the valve opening on the quaternary air duct is reduced, thereby reducing the amount of high-temperature quaternary air supplied to the calciner system. When the calorific value of the gangue is below 300 kcal / kg, the high-temperature quaternary air supply can be maintained. When the calorific value of the gangue is above 700 kcal / kg, the air volume entering the primary cooling system or the calciner's output can be increased.

[0038] The flue gas generated by the combustion of fuel and the decomposition of coal gangue in the calciner system leaves the calciner system and enters the suspension preheating system. The coal gangue raw meal powder fed into the suspension preheating system is then preheated and subjected to gas-solid separation for multiple times. It finally leaves from the air outlet of the top-level cyclone preheater of the suspension preheating system, and then enters the existing firing system to preheat the raw meal and generate waste heat for power generation to realize waste heat recovery. It then enters the dust collection system and flue gas treatment system of the existing firing system for treatment and is discharged into the atmosphere.

[0039] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0040] Example 1 As the instruction manual Figure 1 As shown, the material flow is: Gangue raw material containing kaolinite and a certain calorific value first enters a drying and crushing machine, where it is dried and crushed to produce gangue powder particles that meet production needs. These particles are then fed through a feeding device and into the air inlet pipe of the first cyclone preheater of the suspension preheating system. Within the cyclone preheater, the gangue powder undergoes preheating and gas-solid separation. After heat exchange and gas-solid separation, the raw meal powder enters the calcining furnace system through the discharge pipe of the second cyclone preheater of the suspension preheating system.

[0041] The calcining furnace system includes a high-efficiency material spreading device, a hot air inlet duct, and a flue gas outlet duct, etc. Multiple temperature measuring points are layered in the height direction of the calcining furnace to monitor the temperature distribution in the calcining furnace in real time. The temperature distribution in the calcining furnace is controlled within a reasonable range by adjusting the amount of material and flue gas fed into the calcining furnace system. Reasonable temperature distribution in the calcining furnace can ensure the complete combustion of combustibles in the gangue and the complete decomposition of kaolinite, while ensuring that the gangue is not overburned and the activity of the finished kaolinite meets the requirements of subsequent production. The heat released by the combustion of the gangue in the calcining furnace system and the heat carried by the hot air entering the calcining furnace system are used to decompose the kaolinite in the gangue. The decomposed hot material leaves the calcining furnace system and then enters the first cooling system after gas-solid separation with the hot flue gas in the second cyclone preheater of the suspension preheating system.

[0042] The hot material undergoes rapid cooling and gas-solid separation in the cyclone cooler of the first cooling system. After rapid cooling in the first cooling system, the material enters the second cooling system through the third cyclone cooler CC3 of the first cooling system after gas-solid separation. The material undergoes further cooling and gas-solid separation in the cyclone cooler of the second cooling system before exiting the discharge pipe of the fourth cyclone cooler CC4 of the second cooling system and entering the finished zipper machine, ultimately producing a finished product that meets the requirements.

[0043] Combined with the composition of coal gangue (mainly kaolinite content) and its own calorific value, the calciner system of this application adopts a reasonable design, which can achieve stable operation of the system without the need for external fuel supply. The system heat demand can be met only by relying on the calorific value of the coal gangue and the high-temperature air entering the calciner system from the first cooling system.

[0044] As the instruction manual Figure 1 As shown, the gas flow direction is: The first route is room temperature air, which enters the fourth cyclone cooler CC4 of the second cooling system, and then cools the materials entering the second cooling system. The air that has completed heat exchange leaves from the outlet of the fifth cyclone cooler CC5 of the second cooling system, and is divided into two routes after passing through the circulating fan: one route enters the air inlet pipe of the third cyclone cooler CC3 of the first cooling system, and then cools the hot materials entering the first cooling system. The air that has completed heat exchange is fully preheated by the high-temperature fourth air (the air temperature is preheated to 600~800℃) and enters the calcining furnace system through the bottom of the calcining furnace system; the other route enters the high-temperature fan outlet pipe of the existing firing system, and then enters the waste heat utilization system for waste heat recovery and utilization, and then is discharged into the atmosphere after being treated by the dust collection system and the flue gas treatment system.

[0045] The second route is high-temperature quaternary air. The high-temperature quaternary air from the existing cement kiln system is connected to the bottom of the calciner system via a quaternary air duct. A valve is installed on the connecting pipe, and the amount of high-temperature quaternary air entering the calciner system is controlled by adjusting the valve opening. The high-temperature quaternary air from the existing firing system enters the calciner system through the quaternary air duct as combustion air and an external heat source for the initial charging of the calciner system. This promotes the complete combustion of combustibles such as fixed carbon contained in the gangue and the complete decomposition of minerals such as kaolinite contained in the gangue within the calciner system. At the same time, this part of the high-temperature quaternary air can preheat the combustion air entering the calciner system to a reasonable temperature range of 600-800℃. The fully preheated combustion air enters the calciner system, ensuring the complete decomposition of minerals and combustion reactions of combustibles within the calciner system. The flue gas generated by the combustion of fuel and the decomposition of coal gangue in the calcining furnace system leaves the calcining furnace system and enters the suspension preheating system. The coal gangue raw meal powder fed into the suspension preheating system is then preheated and subjected to gas-solid separation multiple times. Finally, it leaves from the air outlet of the first cyclone preheater of the suspension preheating system, and then enters the air inlet pipe of the second cyclone preheater C2 of the existing firing system to preheat the raw meal and generate waste heat for power generation to realize waste heat recovery. The flue gas then enters the dust collection system and flue gas treatment system of the existing firing system for treatment and is discharged into the atmosphere.

[0046] The principle of this embodiment is: This embodiment makes full use of the high-temperature quaternary air of the existing cement clinker production line firing system as a heat source for the decomposition of kaolinite in the coal gangue and as combustion-supporting air for the combustion of combustibles in the coal gangue (after the calciner system is running stably, the supply of high-temperature quaternary air can be reduced. At this time, the high-temperature quaternary air is only used to preheat the combustion-supporting air of the calciner system to a reasonable temperature range of 600~800℃). The high-temperature flue gas generated by the calciner system enters the existing firing system after preheating the coal gangue material to realize heat recovery and utilization.

[0047] This is because the high-temperature quaternary air of the firing system of the existing cement clinker production line (the quaternary air temperature is designed to be 850~1050℃) carries a large amount of thermal enthalpy, and the O2 contained in the quaternary air can be used by the combustion of combustibles in the coal gangue; in addition, the decomposition of minerals such as kaolinite in the coal gangue is a strong endothermic reaction. Since the temperature of the combustion air entering the calcining furnace system is relatively low (generally 300~500℃), after the combustion air with a lower temperature enters the calcining furnace system, in a strong endothermic environment, it is difficult for the mineral decomposition and combustible combustion reactions in the coal gangue to proceed continuously and stably. This application adds a quaternary air duct to the existing firing system, and independently extracts part of the high-temperature quaternary air into the bottom of the calcining furnace system. This part of the high-temperature quaternary air can fully preheat the combustion air entering the calcining furnace system to 600~800℃. After the fully preheated combustion air enters the calcining furnace system, it can ensure that the mineral decomposition reaction and the combustible combustion reaction in the calcining furnace system are fully carried out.

[0048] In addition, the high-temperature flue gas generated by 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 in the calciner system carries a large amount of heat and can be used to preheat the raw materials of the existing firing system and to generate waste heat in the kiln tail waste heat power generation system of the existing firing system, thereby reducing the energy consumption of the existing firing system while increasing the waste heat power generation capacity of the existing firing system.

[0049] Considering that gangue often contains a large amount of combustible materials and releases a certain amount of heat at high temperatures, when gangue is used as a raw material for the preparation of metakaolinite, the gangue will burn and release heat in the preheater system, which will lead to problems such as crusting and blockage in the preheater system. In order to ensure the stable operation of the suspension calcination system and controllable product quality, it is necessary to control the combustion and heat release process of the combustible materials in the gangue to occur within the calciner system. According to experimental research, the combustion temperature range of the combustible materials in gangue is generally 350~600℃, and the intense combustion temperature range is generally 450~550℃. Therefore, it is necessary to reasonably design the number of preheater stages, feeding points and flue gas temperature of the suspension preheating system so that all the gangue in the above combustion temperature range, especially the intense combustion temperature range, is located in the calciner.

[0050] In this embodiment, the flue gas temperature at the calciner system outlet is rationally designed. By controlling the flue gas temperature at the calciner outlet and the number of preheater stages, the location where the coal gangue burns and releases a large amount of heat is inside the calciner, rather than in the preheater, thereby avoiding the blockage of the preheater due to crusting. According to theoretical calculations, when the number of preheater stages is three, if the flue gas temperature at the calciner outlet is 850-900°C, the flue gas temperature at the first-stage preheater outlet is about 550-600°C or even higher, and the discharge pipe of the first-stage cyclone of the preheater is prone to crusting and blockage; however, if the flue gas temperature at the calciner outlet is controlled at 800-850°C, the flue gas temperature at the first-stage preheater outlet is about 500-550°C, and the discharge pipe of the first-stage cyclone of the preheater will not be blocked by crusting.

[0051] In summary, this embodiment not only rationally controls the flue gas temperature during preheating of gangue, but also rationally designs the number of preheater stages and raw meal feed points, allowing the preheated gangue to enter the calciner in a relatively short time. This reduces system heat consumption while avoiding heat release from combustion within the preheater. This maintains the preheated gangue temperature within an appropriate range, enabling rapid and stable combustion of combustibles and the complete decomposition of minerals such as kaolinite in a high-temperature, fourth-order air environment.

[0052] This embodiment has a first cooling system and a second cooling system arranged in sequence from top to bottom, and the two systems have clear functional positioning. Among them: the first cooling system is used to preliminarily cool the calcined metakaolinite. After the preliminarily cooled metakaolinite enters the second cooling system and is air-cooled to the temperature required for subsequent production. The hot air after heat exchange is fully preheated by high-temperature quaternary air and then enters the calcination furnace system as a combustion-supporting medium to provide stable combustion of the combustibles carried by the coal gangue in the calcination furnace. If only the first cooling system or the second cooling system is set, there will be many unfavorable situations such as incomplete combustion of combustibles, insufficient decomposition of kaolinite, and the temperature of the finished metakaolinite being too high to meet the needs of subsequent production.

[0053] In summary, the first cooling system and the second cooling system can achieve full combustion of combustibles in the gangue, full decomposition of kaolinite, and full cooling of the metakaolinite product, which can effectively reduce the system heat consumption and investment cost.

[0054] Furthermore, part of the medium-temperature air (temperature of about 200-250°C) exiting the second cooling system is circulated into the first cooling system via the circulating fan to cool the high-temperature metakaolinite. On the one hand, the heat can be fully recovered and utilized; on the other hand, the temperature of the air after heat exchange is higher than that after directly cooling the high-temperature metakaolinite with conventional air (temperature of about 20-30°C), which helps promote the stable combustion and decomposition of the coal gangue material in the calciner system.

[0055] This embodiment rationally designs the suspension cooling system and the suspension preheating system so that the temperature of the gangue after suspension preheating is lower than the intense combustion temperature range, thereby preventing the gangue raw materials from burning and releasing heat in the cyclone separator, causing system crusting and blockage.

[0056] Example 2 As the instruction manual Figure 1 As shown, the preferred number of stages for the cyclone preheater in the suspension preheating system is one to three; in this embodiment, it is two. The preferred number of stages for the cyclone cooler in the first cooling system is one to two; in this embodiment, it is one. The preferred number of stages for the cyclone cooler in the second cooling system is one to two; in this embodiment, it is two. The calcination temperature in the calcining furnace system is preferably 650-1000°C; the residence time of the gas in the calcining furnace system is preferably 2-10 seconds; and the calorific value of the coal gangue is preferably 300-700 kcal / kg.

[0057] In this embodiment, the suspension preheating system includes a first cyclone preheater CC1, a second cyclone preheater CC2, a high-efficiency material spreading device and connecting pipes, etc.; the calcining furnace system includes a high-efficiency material spreading device, a hot air inlet pipe and a flue gas outlet pipe, etc.; the first cooling system includes a third cyclone cooler CC3, a high-efficiency material spreading device and connecting pipes, etc.; the second cooling system includes a fourth cyclone cooler CC4, a fifth cyclone cooler CC5, a high-efficiency material spreading device and connecting pipes, etc.

[0058] Working process: The heat released by the combustion of the gangue and the heat carried by the hot air entering the calcining furnace system are used to decompose the kaolinite in the gangue. The decomposed hot material leaves the calcining furnace system and then enters the first cooling system after gas-solid separation with the hot flue gas in the lowest cyclone preheater of the suspension preheating system. The first cooling system includes one or more stages of cyclone coolers, a high-efficiency material spreading device, and connecting pipes. The hot material is rapidly cooled and gas-solid separated in the cyclone cooler of the first cooling system. After gas-solid separation, the material rapidly cooled in the first cooling system enters the second cooling system from the lowest cyclone cooler of the first cooling system. The second cooling system includes one or more stages of cyclone coolers, a high-efficiency material spreading device, and connecting pipes. The material is further cooled and gas-solid separated in the cyclone cooler of the second cooling system, and finally leaves the discharge pipe of the lowest cyclone cooler of the second cooling system and falls into the finished zipper machine, ultimately obtaining a finished product that meets the requirements.

[0059] The first path of normal temperature air enters the second cooling system, and then cools the materials entering the second cooling system. The air that has completed heat exchange leaves from the outlet of the uppermost cyclone cooler of the second cooling system, and is divided into two paths after passing through the circulating fan: one path enters the air inlet pipe of the lowermost cyclone cooler of the first cooling system, and then cools the hot materials entering the first cooling system. The air that has completed heat exchange enters the calcining furnace system through the bottom of the calcining furnace system after being fully preheated by the high-temperature quaternary air; the other path enters the outlet pipe of the high-temperature fan of the existing firing system, and then enters the waste heat utilization system for waste heat recovery and utilization, and then is discharged into the atmosphere after being treated by the dust collection system and the flue gas treatment system.

[0060] The second route is high-temperature quaternary air. The quaternary air from the existing cement kiln system is connected to the bottom of the calciner system through a quaternary air duct. A valve is installed on the connecting pipe, and the amount of quaternary air entering the calciner system is controlled by adjusting the valve opening. The high-temperature quaternary air from the existing firing system enters the calciner system through the quaternary air duct as combustion air and an external heat source for the initial charging of the calciner system. It promotes 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 within the calciner system. At the same time, this part of the high-temperature quaternary air can preheat the combustion air entering the calciner system to a reasonable temperature range of 600-800℃. The fully preheated combustion air enters the calciner system, ensuring the complete decomposition of minerals and combustion reactions of combustibles in the calciner system.

[0061] The valve opening on the quaternary air duct can be adjusted in real time based on the calciner system's operating conditions. When the calciner system is operating stably (determined based on the system's operating conditions, generally 1-3 hours after charging), the supply of high-temperature quaternary air can be reduced. At this point, the high-temperature quaternary air is only used to preheat the calciner system's combustion air to a reasonable temperature range of 600-800°C. In summary, by combining the gangue's composition (primarily kaolinite content) and its inherent calorific value, the calciner system of this embodiment, through its rational design, can achieve stable system operation without the need for external fuel supply, relying solely on the gangue's inherent calorific value to meet the system's heat requirements.

[0062] The flue gas generated by the combustion of fuel and the decomposition of coal gangue in the calciner system leaves the calciner system and enters the suspension preheating system. The coal gangue raw meal powder fed into the suspension preheating system is then preheated and subjected to gas-solid separation for multiple times. It finally leaves from the air outlet of the top-level cyclone preheater of the suspension preheating system, and then enters the existing firing system to preheat the raw meal and generate waste heat for power generation to realize waste heat recovery. It then enters the dust collection system and flue gas treatment system of the existing firing system for treatment and is discharged into the atmosphere.

[0063] This embodiment has strong adaptability to the calorific value of the gangue raw material. Furthermore, to prevent heat release from gangue combustion within the preheater system, this embodiment utilizes a rationally designed suspension cooling system and suspension preheating system. The flue gas generated by the calciner system in this embodiment undergoes gas-solid separation in a cyclone separator before entering the existing firing system, enabling full recovery and utilization of the heat carried by the flue gas. Based on the actual site conditions of existing firing systems, the flue gas generated by the calciner system in this application can also enter the flue gas outlet ducts of cyclone separators at other stages of the existing firing system.

[0064] This embodiment addresses the practical needs of processing combustible gangue and controlling the activity of gangue activated calcination products. It also fully considers the specific characteristics of combustible materials in gangue to produce a highly active metakaolinite product. It also addresses issues such as preheater system blockage caused by heat release during gangue preheating, complex production processes, high system energy consumption, and product overburning in the gangue suspension calcination production system. Furthermore, through the rational design of the gangue activated calcination process and system, when the gangue calorific value is within the recommended range (300-700 kcal / kg), the newly added suspension calcination system can be added without the need for additional fuel, effectively reducing the energy consumption of the existing cement kiln system.

[0065] In summary, the present invention provides a low-energy consumption coal gangue suspended activation calcination process and system.

[0066] The above embodiments describe the present invention in detail, but the contents described are only preferred embodiments of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A low-energy consumption coal gangue suspension activation calcination system, characterized by: The low-energy coal gangue suspended activation calcination system includes: a calcination furnace system and a quaternary air duct, one end of the quaternary air duct is connected to the bottom of the calcination furnace of the calcination furnace system to form a local mixing area at the bottom of the calcination furnace, and the other end is connected to the kiln door cover or tertiary air duct or cooler of the existing firing system, and a valve is provided on the quaternary air duct.

2. The low-energy consumption coal gangue suspension activation calcination system according to claim 1 is characterized in that: The low-energy consumption coal gangue suspension activation calcination system also includes a first cooling system and a second cooling system. The first cooling system is one to two levels, and the second cooling system is one to two levels.

3. The low-energy consumption coal gangue suspension activation calcination system according to claim 2, characterized in that: The low-energy coal gangue suspended activation calcination system also includes a suspended preheating system, which has one to three stages. A feeding point is provided at the air inlet pipe of the first cyclone preheater of the suspended preheating system, the discharge pipe of the penultimate cyclone preheater of the suspended preheating system is connected to the calcining furnace, and the discharge pipe of the lowest cyclone preheater of the suspended preheating system is connected to the air inlet pipe of the first cooling system.

4. The low-energy consumption coal gangue suspension activation calcination system according to claim 3 is characterized in that: The air outlet pipe of the first cyclone preheater of the suspension preheating system is connected to the suspension preheating system of the existing firing system.

5. The low-energy consumption coal gangue suspension activation calcination system according to claim 2, characterized in that: The air outlet pipe of the second cooling system is connected to the air inlet pipe of the waste heat utilization system and the first cooling system respectively, and a valve is provided on the circulation air pipe between the second cooling system and the first cooling system.

6. The low-energy consumption coal gangue suspension activation calcination system according to claim 4, characterized in that: The firing system includes a preheater, a decomposition furnace, a rotary kiln and a cooler connected in sequence, and the two ends of the tertiary air duct are respectively connected to the decomposition furnace and the cooler; the outlet duct of the preheating system is connected to the waste heat utilization system through a waste heat boiler and a high-temperature fan, and the waste heat utilization system is a raw material mill. The waste heat utilization system, the dust collection system and the flue gas treatment system are connected in sequence.

7. A low-energy consumption coal gangue suspension activation calcination process, characterized by: The low-energy consumption coal gangue suspension activation calcination process comprises the following steps: Step 1: Extract the high-temperature quaternary air from the existing firing system into the calcining furnace system.

8. The low-energy consumption coal gangue suspension activation calcination process according to claim 1, characterized in that: The step 1 is: When the calorific value of coal gangue is 300~700kcal / kg, extract the high-temperature quaternary air of the existing firing system into the calcining furnace system, and reduce the extraction amount after the system stabilizes; When the calorific value of coal gangue is lower than 300kcal / kg, the high-temperature quaternary air of the existing firing system is extracted to enter the calcining furnace system; When the calorific value of coal gangue is higher than 700kcal / kg, the high-temperature fourth air of the existing firing system is extracted into the calciner system, and the extraction amount is reduced after the system is stable, and the air volume entering the first cooling system is increased or the output of the calciner system is reduced.

9. The low-energy consumption coal gangue suspension activation calcination process according to claim 1, characterized in that: The calcination temperature of the calcination furnace is 650-1000° C., and the residence time of the gas in the calcination furnace system is 2-10 seconds.

10. The low-energy consumption coal gangue suspension activation calcination process according to claim 1, characterized in that: The high-temperature fourth air temperature is 850~1050℃.

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