Low-energy-consumption calcining system and process for preparing kaolin from coal gangue

Abstract

The low-energy-consumption calcining system comprises a preheater, a calcining furnace, a rotary kiln and a multi-stage cyclone cooler which are sequentially connected, the multi-stage cyclone cooler comprises a heat recovery unit and a cooling unit, clinker discharged from the rotary kiln directly enters the multi-stage cyclone cooler to be cooled, and the clinker discharged from the calcining furnace enters the multi-stage cyclone cooler to be cooled. Wherein a discharge port of the heat recovery unit is connected with an air inlet of the cooling unit, an air outlet of the cooling unit is connected with the air inlet of the heat recovery unit through a branch air pipe, a high-temperature fan is arranged between the cooling unit and the heat recovery unit, and clinker is fed into the air pipe between the high-temperature fan and the heat recovery unit. And an air outlet of the heat recovery unit is connected with the calcining furnace through a tertiary air pipe. The device has the functions of calcining, cooling and recovering heat of the kaolin, a high-whiteness kaolin product is obtained, and the energy consumption of the system is reduced at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of kaolin preparation, in particular to a low-energy consumption calcining system and process for preparing kaolin from coal gangue. Background Art

[0002] Calcined kaolin is a process in which kaolin is sintered in a furnace to a specific temperature and time, causing its physical and chemical properties to change to meet specific requirements. Due to its excellent plasticity and refractory properties, it is widely used in a variety of industries, including ceramics, papermaking, coatings, rubber, plastics, and building materials. However, with the continued mining of high-grade conventional kaolin, the raw ore required to produce refined kaolin that meets industrial requirements has become increasingly scarce.

[0003] Gangue is a solid waste emitted during the mining and washing processes. Its main components are Al2O3 and SiO2. It is produced in large quantities and is generally stored in stockpiles, which has a significant impact on the environment. It can cause spontaneous combustion, acid rain, underground seepage, river siltation, photochemical smog, and mudslides. Kaolinite is the most important mineral component of gangue. Using gangue to prepare calcined kaolin can significantly improve the utilization efficiency of gangue resources, reduce environmental pollution caused by gangue accumulation or discharge, increase its added value, and achieve significant economic benefits. However, gangue has a high carbon content and low natural whiteness. The associated carbon and organic matter are difficult to remove, and incomplete carbon removal can seriously affect the whiteness of the kaolin. Furthermore, the current process for preparing calcined kaolin from gangue has low thermal efficiency and high energy consumption.

[0004] In summary, the problems existing in the prior art are:

[0005] (1) The production process of calcined kaolin using coal gangue is prone to sintering, resulting in high system energy consumption and low heat utilization efficiency.

[0006] (2) It is difficult to prepare high-whiteness calcined kaolin using coal gangue. In order to further improve the whiteness of calcined kaolin, the production cost is high and the economic efficiency is poor. Summary of the Invention

[0007] In order to solve the problem of low whiteness and high energy consumption of kaolin produced by calcining coal gangue, the present invention provides a low-energy calcination system and process for producing kaolin from coal gangue. In order to fully decarbonize the material and increase its whiteness, a material circulation is set up in the calcining furnace to increase the calcination time and improve the decarbonization efficiency. A rotary kiln is set up, and the temperature and time in the kiln are reasonably designed to promote the complete removal of carbon in the coal gangue, further improving the whiteness of the coal gangue after calcination. At the same time, the heat of the high-temperature kaolin product from the rotary kiln is recovered by a multi-stage cyclone cooler. The hot air from the heat recovery unit is used as tertiary air for calcination in the calcining furnace, and a part of the hot air from the cooling unit enters the heat recovery unit. The present invention combines the functions of calcining, cooling and heat recovery of kaolin, obtains a high-whiteness kaolin product, and at the same time realizes full heat recovery and utilization, improves the thermal utilization efficiency of the system, reduces the system energy consumption, achieves energy saving and efficiency improvement, and has important practical significance.

[0008] The present invention is implemented as follows: a low-energy calcination system for preparing kaolin from coal gangue includes a preheater, a calcining furnace, a rotary kiln and a multi-stage cyclone cooler connected in sequence, the multi-stage cyclone cooler includes a heat recovery unit and a cooling unit, and the clinker exiting the rotary kiln directly enters the multi-stage cyclone cooler for cooling, wherein the discharge port of the heat recovery unit is connected to the air inlet of the cooling unit, and the air outlet of the cooling unit is connected to the air inlet of the heat recovery unit through a branch air duct, and a high-temperature fan is provided between the cooling unit and the heat recovery unit, and the clinker is fed into the air duct between the high-temperature fan and the heat recovery unit, and the air outlet of the heat recovery unit is connected to the calcining furnace through a tertiary air duct.

[0009] In the above technical solution, preferably, the temperature of the tertiary air at the air outlet of the heat recovery unit is 500-800°C.

[0010] In the above technical solution, preferably, the preheater is a multi-stage cyclone heat exchange structure, and the discharge pipe of the last stage cyclone is provided with a distribution valve, which is respectively connected to the calcining furnace and the rotary kiln tail smoke chamber.

[0011] In the above technical solution, preferably, the discharge pipe of the penultimate cyclone of the preheater is connected to the calcining furnace, and the outlet temperature of the calcining furnace is 700-1000°C.

[0012] In the above technical solution, preferably, the air outlet of the cooling unit is also connected to a dust collector, and a part of the air outlet of the cooling unit enters the heat recovery unit, and a part enters the dust collector.

[0013] In the above technical solution, it is further preferred that the air outlet of the dust collector is connected to the hot blast furnace, the air outlet of the hot blast furnace is connected to the rotary kiln, and the hot air generated by the combustion of fuel in the hot blast furnace enters the rotary kiln.

[0014] In the above technical solution, it is further preferred that the dust collector outlet is connected to the waste heat recovery air duct through a fan, the waste heat recovery air duct is provided with a primary air branch pipe and a secondary air branch pipe, the primary air branch pipe is connected to the hot blast furnace burner, and the secondary air branch pipe is connected to the hot blast furnace air inlet, and the air after dust collection enters the hot blast furnace for use as primary air and secondary air.

[0015] In the above technical solution, it is further preferred that the primary air branch pipe and the secondary air branch pipe are both provided with fans and valves to adjust the air volume of the secondary air and control the temperature of the hot air out of the hot air furnace.

[0016] In the above technical solution, it is further preferred that a cold air duct is provided on the inlet air duct of the dust collector, and a valve is provided on the cold air duct, so that the finished products collected by the dust collector enter the finished product transportation system.

[0017] In the above technical solution, it is further preferred that the bottom of the air duct at the air inlet of the heat recovery unit is connected to the emergency chamber to deal with the situation where the high-temperature fan stops and the material leaving the rotary kiln cannot be lifted up and enter the heat recovery unit.

[0018] In the above technical solution, preferably, cooling air is introduced into the air inlet of the cooling unit; and the discharge port of the cooling unit is connected to the finished product transportation system.

[0019] In the above technical solution, preferably, an emergency buffer hopper is provided at the bottom of the air duct at the air inlet of the cooling unit, and a discharge port of the emergency buffer hopper is connected to the finished product transportation system.

[0020] A low-energy calcination process for preparing kaolin from coal gangue comprises the following steps:

[0021] S1: The gangue raw material is fed into the preheater and undergoes multiple heat exchanges with the flue gas from the calciner to remove moisture, some hydroxyl groups and carbon. After the multi-stage gas-solid heat exchange, the material enters the calciner, where the hydroxyl groups and carbon are removed to obtain high-temperature kaolin products, and a large amount of flue gas is generated. The outlet temperature of the calciner is 700-1000℃.

[0022] S2: After decarbonization in the calcining furnace, the material passes through the final cyclone for gas-solid separation and then enters the rotary kiln to remove carbon from the coal gangue. The rotary kiln rotates at a speed of 0-5 rpm, the temperature inside the rotary kiln is 800-1100°C, and the material stays in the rotary kiln for 30-100 minutes. The hot material leaving the rotary kiln enters the heat recovery unit.

[0023] S3: The hot air after heat exchange in the cooling unit is partially led to the heat recovery unit under the action of the high-temperature fan according to the amount of oxygen required by the calciner, and exchanges heat with the hot material. The air leaving the heat recovery unit enters the calciner as tertiary air, and the tertiary air temperature is 500-800℃; the hot material separated by the heat recovery unit enters the cooling unit for cooling, and part of the air leaving the cooling unit is led to the heat recovery unit, and the outlet air temperature of the cooling unit is 100-300℃.

[0024] In the above technical solution, preferably, after the gas-solid separation of the material in the final cyclone, a part of it is recycled back to the calciner for further decarbonization and whitening, and the other part enters the rotary kiln to remove the carbon in the coal gangue;

[0025] The cooling air is introduced into the cooling unit to exchange heat with the material inside, and part of the air leaving the cooling unit enters the dust collector;

[0026] The hot air temperature at the dust collector outlet is less than 250℃. Part of the air leaving the dust collector enters the hot blast furnace burner as primary air to transport fuel, and part of it enters the hot blast furnace as secondary air. The hot air generated by the combustion of fuel in the hot blast furnace enters the rotary kiln.

[0027] The advantages and positive effects of the present invention are:

[0028] 1. The present invention combines the functions of calcining, cooling and heat recovery of kaolin, thereby obtaining a kaolin product with high whiteness. At the same time, it realizes full heat recovery and utilization, improves the thermal utilization efficiency of the system, reduces the energy consumption of the system, and achieves energy saving and efficiency improvement.

[0029] 2. To fully decarbonize the material and increase its whiteness, the present invention incorporates a material recirculation system in the calciner. A portion of the discharge from the final cyclone is recirculated back into the calciner, increasing calcination time and decarbonization efficiency, further enhancing kaolin whiteness. Furthermore, multi-point feeding within the calciner allows for temperature adjustment to tailor the decarbonization effect to different gangue types, ensuring system stability and product whiteness.

[0030] 3. Based on the decarbonization mechanism, the present invention designs a rotary kiln and rationally designs the temperature and time in the kiln to promote the complete removal of carbon from the coal gangue, further improving the whiteness of the coal gangue after calcination; the hot flue gas in the rotary kiln comes from the hot blast furnace, and the temperature of the flue gas out of the hot blast furnace is controlled by regulating the secondary air volume, thereby ensuring the temperature stability in the rotary kiln and avoiding direct contact with the high-temperature flame, which would significantly reduce the activity of the kaolin product.

[0031] 4. The present invention is provided with a multi-stage cyclone cooler, which includes a heat recovery unit and a cooling unit. The cooling air volume is reasonably designed so that the hot air leaving the heat recovery unit is used as tertiary air for calcination in the calcining furnace. Part of the hot air leaving the cooling unit enters the heat recovery unit, and the other part enters the hot blast furnace as primary air and secondary air after dust collection. This can achieve full combustion of fuel, full decarbonization of coal gangue, full cooling of finished products, and full recovery of waste heat, which can effectively reduce the system heat consumption and investment costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of a low-energy calcination system for preparing kaolin from coal gangue provided in Example 1 of the present invention.

[0033] In the picture:

[0034] 1-preheater, 101-first stage cyclone, 102-second to last stage cyclone, 103-final stage cyclone, 104-dispensing valve;

[0035] 2-Calcining furnace, 3-Hot blast furnace, 4-Hot blast furnace burner, 5-Calcining furnace burner, 6-Rotary kiln, 7-Smoke chamber, 8-Kiln door cover, 9-Heat recovery unit, 10-Cooling unit, 11-Dust collector, 12-Fan, 13-Branch air duct, 14-High-temperature fan, 15-Waste heat recovery air duct, 16-Primary air branch pipe, 17-Secondary air branch pipe, 18-Emergency buffer hopper, 19 Finished product zipper machine, 20-Cold air duct, 21-Emergency bin, 22-Discharge valve, 23-Kiln tail high-temperature fan, 24-Tertiary air duct.

[0036] a-coal gangue, b-finished kaolin, A-cooling air, B-preheater flue gas, C-excess air.

[0037] The dotted line with an arrow is the direction of airflow, and the solid line with an arrow is the direction of material flow. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] In the description of the present invention, it should be understood that the terms "up", "down", "front", "back", "left", "right", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0040] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0041] Example 1

[0042] See also Figure 1 An embodiment of the present invention provides a low-energy calcination system for preparing kaolin from coal gangue, comprising a preheater 1, a calcining furnace 2, a hot blast furnace 3, a rotary kiln 6, a smoke chamber 7 connected to the rotary kiln, a multi-stage cyclone cooler, a dust collector 11, and a waste heat recovery duct 15. The preheater 1, calcining furnace 2, and rotary kiln 6 are connected in sequence. The rotary kiln 6 includes a kiln tail smoke chamber 7 and a kiln door cover 8. The rotary kiln 6 is not provided with a burner (i.e., no fuel inlet). Burners are respectively provided at the bottom of the calcining furnace 2 and at the top of the hot blast furnace 3. The calcining furnace burner 5 is located at the bottom of the calcining furnace 2, and the hot blast furnace burner 4 is located at the top of the hot blast furnace 3.

[0043] A raw material inlet is provided on the connecting air duct between the first-stage cyclone 101 and the second-stage cyclone of the preheater 1. The air inlet of the final cyclone 103 of the preheater 1 is connected to the air outlet duct of the calciner 2. A dispensing valve 104 is provided on the discharge pipe of the final cyclone 103 of the preheater 1, connecting the calciner 2 and the rotary kiln tail flue chamber 7, respectively. Part of the material collected by the final cyclone 103 enters the rotary kiln tail flue chamber 7, and part enters the calciner 2. This allows the material to be circulated to the calciner 2 for multiple calcination and carbon removal, thereby increasing the whiteness of the product. The discharge pipe of the penultimate cyclone 102 of the preheater 1 is connected to the calciner 2, and the outlet temperature of the calciner 2 is 700-1000°C. The clinker exiting the rotary kiln 6 is directly cooled in a multi-stage cyclone cooler. The multi-stage cyclone cooler includes a heat recovery unit 9 and a cooling unit 10. The rotary kiln discharge end is connected to the air inlet of the heat recovery unit 9, which is connected to the lower portion of the calciner 2 via a tertiary air duct 24. The heat recovery unit 9 discharge port is connected to the air inlet of the cooling unit 10, which is connected to the air inlet of the heat recovery unit 9 via a branch air duct 13. A high-temperature fan 14 is provided between the cooling unit 10 and the heat recovery unit 9. The high-temperature fan 14 can be located on the branch air duct 13 or on the air duct between the cooling unit outlet and the branch air duct 13. The clinker is fed into the air duct between the high-temperature fan 14 and the heat recovery unit 9; a valve is provided on the branch air duct 13. By installing high-temperature blower 14, the pressures of heat recovery unit 9 and calciner 2 are matched. The high-temperature blower 23 at the kiln tail can draw the hot air from heat recovery unit 9 to calciner 2 for fuel combustion, reducing system energy consumption. Without high-temperature blower 14, the negative pressure at the outlet of the multi-stage cyclone cooler may be higher than the negative pressure at the bottom of calciner 2. Consequently, the tertiary air cannot be drawn into calciner 2, and heat recovery cannot be achieved.

[0044] After being ground to the appropriate particle size, gangue A is fed into preheater 1. Within preheater 1, the material undergoes multi-stage gas-solid heat exchange with flue gas exiting calciner 2 before entering calciner 2. Flue gas B exiting the preheater enters a grinding system or flue gas treatment system. After decarburization in the calciner, the material undergoes gas-solid separation in the final cyclone 103. A portion of the material is recycled back to calciner 2 for further decarburization and whitening, while a portion is fed into rotary kiln 6 for further decarburization. This removes carbon from the gangue and further improves its whiteness after calcination. The hot material leaving the rotary kiln enters the multi-stage cyclone cooler and is cyclone-cooled in turn through the heat recovery unit 9 and the cooling unit 10. A portion of the air leaving the cooling unit 10 enters the heat recovery unit 9. The amount of air introduced from the cooling unit 10 to the heat recovery unit 9 is adjusted according to the amount of oxygen required for the combustion of the fuel in the calcining furnace 2. The air leaving the heat recovery unit 9 is drawn into the calcining furnace 2 through the tertiary air duct 24 as tertiary air. The temperature of the tertiary air is 500-800°C, which reduces the energy consumption of the system.

[0045] As a preferred embodiment, the air outlet of the cooling unit 10 is also connected to the dust collector 11, and the air outlet of the dust collector 11 is connected to the waste heat recovery air duct 15 through the fan 12. The waste heat recovery air duct 15 is provided with a primary air branch pipe 16 and a secondary air branch pipe 17. The primary air branch pipe 16 is connected to the hot air furnace burner 4, and the secondary air branch pipe 17 is connected to the air inlet of the hot air furnace 3.

[0046] A portion of the air exiting cooling unit 10 enters dust collector 11. Finished products collected by cooling unit 10 and dust collector 11 are transported to a finished product transport system. In this embodiment, the finished product transport system employs a finished product zipper machine 19. One stream of hot air exiting dust collector 11 enters hot blast furnace burner 4 as primary air, and another stream enters hot blast furnace 2 as secondary air, thereby achieving efficient heat recovery and reducing system energy consumption.

[0047] As a preferred embodiment, the air outlet of the dust collector 11 is also connected to the waste heat utilization system or the exhaust gas treatment system through the fan 12, so that the residual air C leaving the dust collector 11 enters other waste heat utilization systems or exhaust gas treatment systems.

[0048] As a preferred embodiment, the air outlet of the hot blast furnace 3 is connected to the kiln door cover 8 of the rotary kiln head, and the hot air generated by the combustion of fuel in the hot blast furnace 3 enters the rotary kiln 6. In order to reduce the influence of residual carbon in the solid fuel on the whiteness of the calcined kaolin, the fuel fed into the hot blast furnace burner 4 is preferably gas fuel, which can be natural gas, coal gas, etc.

[0049] As a preferred embodiment, both the primary air branch pipe 16 and the secondary air branch pipe 17 are equipped with fans and valves. The temperature of the hot air exiting the hot blast furnace 3 is controlled by adjusting the volume of the secondary air. Since the central flame temperature generated by fuel combustion is relatively high, if it directly contacts coal gangue, the kaolin product will be mainly mullite, and the product activity will be greatly reduced. Therefore, in order to ensure the activity of calcined kaolin, the fuel is fed into the hot blast furnace 3 through the hot blast furnace burner 4 along with the primary air. Under the combustion assistance and regulation of the secondary air, hot air with appropriate heat and air volume is generated and enters the rotary kiln 6 for kaolin insulation and decarbonization. The rotary kiln 6 rotates at a low speed of 0 to 5 rpm, so that the material slowly moves from the smoke chamber 7 to the discharge port of the kiln door cover 8. The temperature inside the rotary kiln 6 is 800-1100°C, and the material stays in the rotary kiln 6 for 30 to 100 minutes.

[0050] As a preferred embodiment, the inlet air duct of the dust collector 11 is further provided with a cold air duct 20, which is equipped with a valve. When the air volume and temperature in the outlet air duct of the cooling unit 10 are high, especially higher than the temperature that the dust collector equipment can withstand, the valve can be used to adjust the volume of cooling air A entering the dust collector 11, further cooling the hot air and finished products exiting the cooling unit 10, thereby ensuring the safe and stable operation of the dust collector 11 and the finished product transportation system and other equipment.

[0051] As a preferred embodiment, the bottom of the air duct at the air inlet of the heat recovery unit 9 is connected to the emergency bin 21, and a discharge valve 22 is also provided at the bottom of the air duct at the air inlet, which can cope with the situation when the high-temperature fan 14 stops or other emergency situations occur, and the material leaving the rotary kiln cannot be lifted up and enter the heat recovery unit, resulting in material collapse.

[0052] As a preferred embodiment, to fully cool the hot material, cooling air A is introduced into the air inlet of cooling unit 10, further cooling the hot material from heat recovery unit 9 to the desired product temperature. The outlet of cooling unit 10 is connected to the finished product transport system, which in this embodiment uses a finished product zipper machine 19.

[0053] As a preferred embodiment, an emergency buffer hopper 18 is provided at the bottom of the air duct at the air inlet of the cooling unit 10, and the discharge port of the emergency buffer hopper 18 is connected to the finished product transportation system.

[0054] As a preferred embodiment, the preheater 1 is a two- to six-stage cyclone separation preheater. In this embodiment, a four-stage cyclone separation preheater is preferably used. Air lock valves are installed on the discharge pipes of each cyclone. Multiple feed valves 104 are installed on the discharge pipe of the penultimate cyclone, allowing materials to enter the calciner at multiple points, thereby controlling the temperature in the calciner by zone. In this embodiment, two feed valves are installed on the discharge pipe of the penultimate cyclone 102. The three feed valves control the temperature in the calciner 2 to 700-1100°C, and the calciner outlet temperature to 700-1000°C. The calciner burner 5 and the tertiary air inlet are located at the bottom of the calciner 2.

[0055] Example 2

[0056] See also Figure 1 The present invention provides a low-energy calcination process for preparing kaolin from coal gangue, comprising the following steps:

[0057] S1: The coal gangue a raw material that has been ground to a suitable particle size is fed into the preheater 1. The raw material undergoes multiple heat exchanges with the flue gas from the calcining furnace 2 in the preheater 1 to remove moisture, part of the hydroxyl groups and carbon. The outlet temperature of the calcining furnace is 700-1000°C; the material after multi-stage gas-solid heat exchange enters the calcining furnace 2, and a calcining furnace burner 5 is arranged at the lower part of the calcining furnace 2. Fuel is sprayed into the calcining furnace burner 5. The heat released by the combustion of the fuel is used to remove hydroxyl groups and decarbonize the material in the calcining furnace 2 to obtain high-temperature kaolin products and generate a large amount of flue gas; the flue gas generated in the calcining furnace 2 enters the preheater 1 to exchange heat with the raw material to become low-temperature flue gas, and the low-temperature flue gas is discharged through the air outlet of the first-level cyclone 101 of the preheater 1.

[0058] S2: After the decarbonized material in the calciner 2 undergoes gas-solid separation in the final cyclone 103 of the preheater 1, a portion is circulated back to the calciner 2 for further decarbonization and whitening, while the remaining portion enters the rotary kiln 6 for extended residence time, thereby promoting the removal of carbon from the gangue and further improving the whiteness of the kaolin after calcining the gangue. The hot air generated by the combustion of fuel in the hot blast furnace 2 enters the rotary kiln 6 to provide heat for decarbonization of the material. The rotation speed of the rotary kiln 6 is 0-5 rpm, causing the material to slowly move from the smoke chamber 7 to the discharge port of the kiln door cover 8. The temperature in the rotary kiln 6 is 800-1100°C, and the material resides in the rotary kiln 6 for 30-100 minutes. The hot material leaving the rotary kiln 6 enters the heat recovery unit 9 in the multi-stage cyclone cooler.

[0059] S3: The hot air after heat exchange in the cooling unit 10 is partially led to the heat recovery unit 9 under the action of the high-temperature fan 14 according to the amount of oxygen required by the calcining furnace 2. After heat exchange with the hot material, the temperature is further increased. The air leaving the heat recovery unit 9 is used as tertiary air to enter the calcining furnace 2 for fuel calcination, reducing system energy consumption. The tertiary air temperature is 500-800°C. The hot material separated by the heat recovery unit 9 enters the cooling unit 10 and exchanges heat with the cooling air A entering the cooling unit 10, and is further cooled to the temperature required by the product. The finished kaolin b collected by the cooling unit 10 enters the finished zipper machine 19. The outlet air temperature of the cooling unit 10 is 100-300°C. Part of the air leaving the cooling unit 10 is circulated to the heat recovery unit 9, and part enters the dust collector 11. The finished kaolin b collected by the dust collector 11 enters the finished zipper machine 19.

[0060] S4: The hot air temperature at the outlet of dust collector 11 is less than 250°C. Part of the air exiting dust collector 11 is used as primary air to transport fuel to hot blast furnace burner 4, and part is used as secondary air to enter hot blast furnace 3. In addition to supporting combustion, the secondary air also regulates air temperature and protects the hot blast furnace walls, thereby achieving efficient heat recovery and utilization. The residual air C enters other waste heat utilization systems or exhaust gas treatment systems.

[0061] When the heat brought by the raw material coal gangue can meet the heat required for calcining kaolin, no additional fuel needs to be added to the burner 5 of the calcining furnace.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-energy calcination system for preparing kaolin from coal gangue, characterized by: It includes a preheater, a calcining furnace, a rotary kiln and a multi-stage cyclone cooler connected in sequence. The multi-stage cyclone cooler includes a heat recovery unit and a cooling unit. The clinker leaving the rotary kiln directly enters the multi-stage cyclone cooler for cooling. The discharge port of the heat recovery unit is connected to the air inlet of the cooling unit, and the air outlet of the cooling unit is connected to the air inlet of the heat recovery unit. A high-temperature fan is provided between the cooling unit and the heat recovery unit. The clinker is fed into the air duct between the high-temperature fan and the heat recovery unit. The air outlet of the heat recovery unit is connected to the calcining furnace through a tertiary air duct.

2. The low-energy calcination system for preparing kaolin from coal gangue according to claim 1, characterized in that: The temperature of the tertiary air at the air outlet of the heat recovery unit is 500-800°C.

3. The low-energy calcination system for preparing kaolin from coal gangue according to claim 1, characterized in that: The preheater is a multi-stage cyclone heat exchange structure, and the discharge pipe of the last stage cyclone is provided with a distribution valve, which is respectively connected to the calcining furnace and the rotary kiln tail smoke chamber.

4. The low-energy calcination system for preparing kaolin from coal gangue according to claim 1, characterized in that: The discharge pipe of the penultimate cyclone of the preheater is connected to the calcining furnace, and the outlet temperature of the calcining furnace is 700-1000°C.

5. The low-energy calcination system for preparing kaolin from coal gangue according to claim 1, characterized in that: The air outlet of the cooling unit is also connected to a dust collector.

6. The low-energy calcination system for preparing kaolin from coal gangue according to claim 5, characterized in that: The air outlet of the dust collector is connected to the hot blast furnace, the air outlet of the hot blast furnace is connected to the rotary kiln, and the hot air generated by the combustion of fuel in the hot blast furnace enters the rotary kiln.

7. The low-energy calcination system for preparing kaolin from coal gangue according to claim 6, characterized in that: The dust collector outlet is connected to the waste heat recovery air duct through a fan. The waste heat recovery air duct is provided with a primary air branch pipe and a secondary air branch pipe. The primary air branch pipe is connected to the hot blast furnace burner, and the secondary air branch pipe is connected to the hot blast furnace air inlet.

8. The low-energy calcination system for preparing kaolin from coal gangue according to claim 7, characterized in that: The primary air branch pipe and the secondary air branch pipe are both provided with fans and valves to adjust the air volume of the secondary air and control the temperature of the hot air leaving the hot air furnace.

9. The low-energy calcination system for preparing kaolin from coal gangue according to claim 5, characterized in that: A cold air duct is provided on the inlet air duct of the dust collector, and a valve is provided on the cold air duct. The finished products collected by the dust collector enter the finished product transportation system.

10. The low-energy calcination system for preparing kaolin from coal gangue according to claim 1, characterized in that: The bottom of the air duct at the air inlet of the heat recovery unit is connected to the emergency chamber.

11. The low-energy calcination system for preparing kaolin from coal gangue according to claim 1, characterized in that: The cooling unit air inlet is fed with cooling air; the cooling unit discharge port is connected to the finished product transportation system.

12. The low-energy calcination system for preparing kaolin from coal gangue according to claim 1, characterized in that: An emergency buffer hopper is provided at the bottom of the air duct at the air inlet of the cooling unit, and a discharge port of the emergency buffer hopper is connected to the finished product transportation system.

13. A low-energy calcination process for producing kaolin from coal gangue, the process being implemented based on the low-energy calcination system for producing kaolin from coal gangue according to any one of claims 1 to 12, characterized in that: The following steps are involved: S1: The gangue raw material is fed into the preheater and undergoes multiple heat exchanges with the flue gas from the calciner to remove moisture, some hydroxyl groups and carbon. After the multi-stage gas-solid heat exchange, the material enters the calciner, where the hydroxyl groups and carbon are removed to obtain high-temperature kaolin products, and a large amount of flue gas is generated. The outlet temperature of the calciner is 700-1000℃. S2: After decarbonization in the calcining furnace, the material passes through the final cyclone for gas-solid separation and then enters the rotary kiln to remove carbon from the coal gangue. The rotary kiln rotates at a speed of 0-5 rpm, the temperature inside the rotary kiln is 800-1100°C, and the material stays in the rotary kiln for 30-100 minutes. The hot material leaving the rotary kiln enters the heat recovery unit. S3: The hot air after heat exchange in the cooling unit enters the heat recovery unit under the action of the high-temperature fan according to the amount of oxygen required by the calciner, exchanges heat with the hot material, and the air leaving the heat recovery unit enters the calciner as tertiary air. The tertiary air temperature is 500-800℃; the hot material separated by the heat recovery unit enters the cooling unit for cooling, and part of the air leaving the cooling unit enters the heat recovery unit. The outlet air temperature of the cooling unit is 100-300℃.

14. The low-energy calcination process for preparing kaolin from coal gangue according to claim 1, characterized in that: After the gas-solid separation of the materials in the final cyclone, part of the materials is recycled back to the calciner for further decarbonization and whitening, and the other part enters the rotary kiln to remove the carbon in the gangue. Cooling air is introduced into the cooling unit to exchange heat with the material inside, and part of the air leaving the cooling unit enters the dust collector; the hot air temperature at the dust collector outlet is less than 250℃, and part of the air leaving the dust collector enters the hot blast furnace burner as primary air to transport fuel, and part of the air enters the hot blast furnace as secondary air. The hot air generated by the combustion of fuel in the hot blast furnace enters the rotary kiln.

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