An energy-saving internal heating rare earth calcining kiln

Abstract

This invention relates to an energy-saving internally heated rare earth roasting kiln, comprising a rotary kiln body and a drive unit. The drive unit rotates the rotary kiln body. A fixed kiln head hood is located at the head of the rotary kiln body, with openings at both ends. A dynamic sealing device is installed at the end of the kiln head hood facing the rotary kiln body, and a flue gas furnace is installed at the other end. A discharge port is located at the lower end of the kiln head hood, and a feed port is located at the tail end of the rotary kiln body. The kiln head portion of the rotary kiln body includes an outer cylinder, inside which a kiln wall is cast. The working layer of the kiln wall is cast with high-alumina wear-resistant castable, and the outer layer of the kiln wall is covered with insulating castable. Several movable impact blocks are evenly distributed around the circumference of the inner ring of the middle part of the rotary kiln body. The kiln tail portion of the rotary kiln body includes an outer cylinder and an inner cylinder, with several sliding support components between the outer and inner cylinders. The inner wall of the inner cylinder is lined with refractory bricks, with different refractory bricks arranged in a staggered pattern. This invention offers good energy-saving performance, a long kiln body service life, improved material roasting quality, and increased acid-saving rate.

Description

Technical Field

[0001] This invention relates to the field of roasting kilns, specifically an energy-saving internal heating rare earth roasting kiln. Background Technology

[0002] Rare earth elements refer to the 17 elements in the periodic table: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y). my country is a globally recognized major rare earth resource country, accounting for 43% of the world's rare earth reserves. It is also a major producer and exporter of rare earth products, accounting for over 85% of global rare earth exports. The Baotou rare earth concentrate contains 50-60% REO and small amounts of fluorine and the radioactive element thorium. Baotou rare earth concentrate accounts for over 60% of my country's refined rare earth concentrate production.

[0003] The main smelting process for rare earth concentrates in Baotou involves high-temperature roasting with concentrated sulfuric acid. This is the primary process in rare earth smelting in the Baotou area, and its widespread application has made a significant contribution to the development of my country's rare earth industry, yielding substantial economic benefits. However, the high-temperature roasting process generates large quantities of sulfur- and fluorine-containing, highly acidic waste gases and radioactive slag. The slag obtained after high-temperature roasting is difficult to dissolve and recycle, and many manufacturers centrally stockpile it in slag storage facilities. Over time, coupled with rapid increases in production volume, the stockpiling of radioactive slag has become not only a serious environmental problem, but the cost of storing the slag in slag storage facilities is also a significant expense for rare earth plants. This not only pollutes the environment for rare earth producers but also wastes valuable thorium and fluorine resources, frequently forcing related rare earth companies to halt production due to environmental issues, severely hindering the sustainable development of the rare earth industry.

[0004] Traditional high-temperature roasting and smelting methods for concentrated sulfuric acid mainly consist of a heating burner, an internally heated rotary kiln, and a concentrated sulfuric acid mixing device. The main problems include: 1. Inaccurate temperature control of the rotary kiln's heating section, affecting production costs, energy consumption, and product quality; 2. Inability to monitor the segmented temperatures of the internally heated rotary kiln in real time; 3. Significantly reduced lifespan of the kiln's internal structure under high temperature and mixed acid conditions; 4. Ring formation within the kiln causing poor material flow and requiring periodic kiln shutdowns for maintenance; and insufficient reaction time and a short service life for the concentrated sulfuric acid mixing device. Summary of the Invention

[0005] The purpose of this invention is to solve the key problems of production efficiency and process control in the current high-temperature roasting and smelting method of rare earth concentrate with concentrated sulfuric acid. By solving these problems, the acid saving rate, REO leaching rate, and thorium residue in the waste residue are all optimized to achieve a balance, while the equipment structure is reasonable and durable.

[0006] The specific solution of the present invention is as follows: an energy-saving internal heating rare earth roasting kiln, comprising a rotary kiln body and a driving device, wherein the driving device drives the rotary kiln body to rotate, the head of the rotary kiln body is provided with a fixed kiln head cover, both ends of the kiln head cover are provided with openings, one end of the kiln head cover facing the rotary kiln body is equipped with a dynamic sealing device, the other end of the kiln head cover is equipped with a flue gas furnace, the lower end of the kiln head cover is provided with a discharge port, the tail end of the rotary kiln body is provided with a feed port, the kiln head part of the rotary kiln body includes an outer cylinder, the inner part of the outer cylinder is filled with a kiln wall, the working layer of the kiln wall is made of high alumina wear-resistant castable, the outer layer of the kiln wall is provided with heat-insulating castable, the middle inner ring of the rotary kiln body is evenly distributed with several movable impact blocks along the circumference, the kiln tail part of the rotary kiln body includes an outer cylinder and an inner cylinder, several sliding support components are provided between the outer cylinder and the inner cylinder, the inner wall of the inner cylinder is filled with refractory bricks, and different refractory bricks are arranged in a staggered manner.

[0007] Furthermore, the outer wall of the rotary kiln body is provided with several sets of temperature measuring mechanisms along its entire length. Each set of temperature measuring mechanisms includes a mounting base fixed to the outside of the outer cylinder. The mounting base is provided with a mounting hole. A protective sleeve extending into the inner wall of the rotary kiln body is installed in the mounting hole. A temperature sensor is installed in the protective sleeve. A clamping flange is installed at the outer end of the temperature sensor. The clamping flange is connected to the mounting base by bolts.

[0008] Furthermore, isolation plates are installed on the inner wall of the outer cylinder of the kiln head section and the middle section where the temperature measuring mechanism is installed, corresponding to the sheath tube. Isolation plates are also installed on the inner cylinder of the kiln tail section where the temperature measuring mechanism is installed, corresponding to the sheath tube. The isolation plates are used to prevent corrosive liquid materials from leaking out from the mounting holes of the temperature measuring mechanism.

[0009] Furthermore, the sliding support assembly includes an outer cylinder support and an inner cylinder support. The outer cylinder support is fixedly connected to the outer cylinder, and the inner cylinder support is fixedly connected to the inner cylinder. The contact portion between the outer cylinder support and the inner cylinder support is provided with an oblong hole. The oblong hole is arranged parallel to the axis of the rotary kiln body, and a connecting bolt for connecting the outer cylinder support and the inner cylinder support is installed in the oblong hole.

[0010] Furthermore, a corrosion-resistant, high-temperature-resistant, and high-strength adhesive is provided between the refractory bricks and the inner cylinder, and between the brick joints of the refractory bricks.

[0011] Furthermore, the kiln wall is evenly distributed with several prefabricated frames along the circumference, and each prefabricated frame is provided with a heat insulation pad on its outer layer, with the heat insulation pad being tightly installed with the outer cylinder.

[0012] Furthermore, the space between the outer cylinder and the inner cylinder is filled with a heat-insulating material, which is made of lightweight aluminum silicate.

[0013] Furthermore, the dynamic sealing device includes a connecting cylinder disposed at the end of the kiln head hood, the connecting cylinder being equipped with two layers of static sealing rings, a cooling ring being disposed on the outer wall of the rotary kiln body, a dynamic sealing ring being disposed on the outer wall of the cooling ring, the dynamic sealing ring being located between the two layers of static sealing rings, a conical cylinder being disposed on the outer static sealing ring, a graphite ring being disposed on the end of the conical cylinder close to the cooling ring, the graphite ring being in contact with the cooling ring.

[0014] Furthermore, the outer layer of the cone is provided with a rigid pressure plate, the inner layer is provided with a sealing sheet, a flexible plate is provided between the sealing sheet and the rigid pressure plate, the graphite ring is installed on the sealing sheet, and a flexible preload ring and a rigid pretension ring are installed on the outer side of the rigid pressure plate.

[0015] Furthermore, the flue gas furnace includes a furnace body, with a burner installed at one end of the furnace body. The burner has a gas inlet and a primary air inlet, and a flue gas outlet at the other end. The flue gas outlet is installed facing the rotary kiln for firing. The characteristic is that a baffle plate is provided at one end of the furnace body near the burner, forming a cavity between the baffle plate and the outer shell of the furnace body. A secondary air inlet is provided on one side of the cavity. Several external direct current air ducts are arranged circumferentially inside the furnace wall. The external direct current air ducts are arranged axially. The inlets of all external direct current air ducts are connected to the cavity, and the outlets extend to the flue gas outlet.

[0016] Furthermore, the furnace wall is provided with several internal swirling air ducts along the circumference. Each internal swirling air duct is composed of a straight air duct and an inclined air duct connected together. The straight air duct is arranged along the axial direction of the furnace body. The inlet of the straight air duct is connected to the cavity. The inclined air duct has an angle of 100°-150° with the axis and an angle of 100°-150° with the radial line. The outlet of the inclined air duct is located in the rear half of the inner wall of the furnace body.

[0017] Furthermore, the partition plate is provided with several internal DC air ducts, the length of which is equal to the thickness of the partition plate. The inlet of the internal DC air duct is connected to the cavity, and the outlet is connected to the furnace.

[0018] Furthermore, the outer wall of the furnace body has a sandwich structure, with an external swirling air duct inside the sandwich. The outer wall of the furnace body has an air inlet, which is connected to the inlet of the external swirling air duct. The end face of the furnace body has an outlet of the external swirling air duct, which is connected to the primary air inlet through a pipe.

[0019] Furthermore, the external swirling air duct is equipped with a spiral baffle.

[0020] Furthermore, the external swirling air duct first diffuses and then converges from the inlet to the outlet.

[0021] This invention offers the following advantages: 1. The thermal insulation performance of the outer layer of the kiln is significantly improved, with the temperature difference between the surface of the material and the contact layer between the material and the kiln shell being less than 3°C, resulting in improved material roasting quality and increased acid-saving rate; 2. Wireless direct measurement technology is employed for the most difficult-to-measure kiln interior temperature. Multiple temperature measuring devices measure the temperature along the entire length of the kiln to generate a temperature curve, which corresponds to the direct quality parameters of the product. The difference between the curve data and the actual values ​​is used as feedback data to adjust the flow rate of fuel and mixed concentrate, system pressure, and rotation speed of the internally heated rotary kiln in real time, achieving precise system control. This upgrades the traditional slow feedback control mode to a more advanced synchronous control mode; 3. Both the kiln head and tail hood are designed with a double-layer flexible sealing structure. The first layer adopts a closed-cell ring seal filled with flexible material to isolate acidic gases, liquids, dust, etc. generated during the production process; the second layer uses stainless steel sheets and flexible material to press and seal on the insulation ring; the insulation ring is equipped with a wear-resistant layer and an air-cooling jacket to improve the service life of the insulation ring and flexible material; 3. The flue gas furnace of this invention is a precision-controlled conditioning furnace. The combustion-supporting part and the conditioning part of the precision-controlled conditioning furnace are separately and independently regulated to ensure that the kiln inlet temperature can be stably and accurately adjusted according to production needs under stable system combustion load conditions, with temperature control of ±5℃, while ensuring that the working medium temperature and load are not affected by the working conditions inside the rotary kiln. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the present invention;

[0023] Figure 2 yes Figure 1 AA view;

[0024] Figure 3 yes Figure 1 BB view;

[0025] Figure 4 yes Figure 1 CC view;

[0026] Figure 5 yes Figure 1 DD view;

[0027] Figure 6 yes Figure 1 A magnified view at point V;

[0028] Figure 7 yes Figure 1 Enlarged view at point VI;

[0029] Figure 8 yes Figure 5 EE view;

[0030] Figure 9 This is a three-dimensional schematic diagram of the flue gas furnace of the present invention;

[0031] Figure 10 yes Figure 9 The main view;

[0032] Figure 11 yes Figure 10 Side view;

[0033] Figure 12 This is a simulation diagram of the temperature distribution of flue gas inside the kiln during the operation of this invention;

[0034] In the diagram: 1. Flue gas furnace; 101. Blower inlet; 102. Secondary air inlet; 103. Gas inlet; 104. Smoke nozzle; 105. Regulating valve; 106. Primary air inlet; 107. External swirl air outlet; 108. Outer shell; 109. Inner shell; 110. Refractory material; 111. Spiral baffle; 112. External swirl air duct; 113. Internal direct flow air duct; 114. External direct flow air duct; 115. Internal swirl air duct; 116. Burner; 117. External direct flow air; 118. Internal direct flow air; 119. Internal swirl air; 120. Secondary air; 121. Primary air; 122. Preheating air; 123. Flue gas; 2. Kiln head hood; 3. Rotary kiln body; 301 1. Outer cylinder; 2. Inner cylinder; 3. Thermal insulation material; 4. Drive device; 5. Discharge port; 6. Connecting cylinder; 7. Static sealing ring; 8. Dynamic sealing ring; 9. Sealing sheet; 10. Flexible plate; 11. Rigid pressure plate; 12. Flexible pre-pressure ring; 13. Rigid pre-tension ring; 14. Graphite block; 15. Cooling ring; 16. Thermal insulation pad; 17. Precast skeleton; 18. Thermal insulation castable; 19. High-alumina wear-resistant castable; 20. Movable impact block; 21. Outer cylinder support; 22. Thermal insulation sheet; 23. Inner cylinder support; 24. Refractory brick; 25. Connecting bolt; 26. Temperature sensor; 27. Compression flange; 28. Mounting seat; 29. ​​Isolation plate; 30. Sheath tube. Detailed Implementation

[0035] See Figure 1-5This embodiment is an energy-saving internally heated rare earth roasting kiln, including a rotary kiln body 3 and a drive device 4. The drive device 4 drives the rotary kiln body 3 to rotate. The head of the rotary kiln body 3 is provided with a fixed kiln head cover 2. Both ends of the kiln head cover 2 are provided with openings. A dynamic sealing device is installed at one end of the kiln head cover 2 facing the rotary kiln body 3, and a flue gas furnace is installed at the other end of the kiln head cover 2. A discharge port 5 is provided at the lower end of the kiln head cover 2, and a feed port is provided at the tail end of the rotary kiln body 3. The kiln head part of the rotary kiln body 3 includes an outer cylinder 3. 01. The outer cylinder 301 is filled with a kiln wall. The working layer of the kiln wall is made of high-alumina wear-resistant castable 19. The outer layer of the kiln wall is provided with heat-insulating castable 18. Several movable impact blocks 20 are evenly distributed around the circumference of the inner ring of the middle part of the rotary kiln body 3. The kiln tail part of the rotary kiln body 3 includes an outer cylinder 301 and an inner cylinder 302. Several sliding support components are provided between the outer cylinder 301 and the inner cylinder 302. The inner wall of the inner cylinder 302 is covered with refractory bricks 24. Different refractory bricks 24 are arranged in a staggered manner.

[0036] When the material reaches the middle of the rotary kiln body 3, it is impacted by the movable impact block 20, breaking up any agglomerated or lumpy material and preventing material clumping that could cause blockages in the flow. (See also...) Figure 6Furthermore, the outer wall of the rotary kiln body 3 is provided with several sets of temperature measuring mechanisms along its entire length. Each set of temperature measuring mechanisms includes a mounting base 28 fixed to the outside of the outer cylinder 301. The mounting base 28 has a mounting hole, and a sheath tube 30 extending into the inner wall of the rotary kiln body 3 is installed in the mounting hole. A temperature sensor 26 is installed in the sheath tube 30, and a clamping flange 27 is installed at the outer end of the temperature sensor 26. The clamping flange 27 is connected to the mounting base 28 by bolts. Traditional rotary kiln control models are all feedback control modes. However, due to the long smelting process, the final data feedback is slow, and there is no accurate mathematical model as a theoretical reference, which makes production control a low-end mode relying on experience. This embodiment aims to shorten the feedback time under traditional conditions and use a more effective theoretical data model to replace the original low-end production mode relying on experience, making quality control more stable and the degree of automation higher. The most important control parameters for roasting control are flow rate, temperature, pressure, time, and proportion, and each parameter has a corresponding mathematical model. This embodiment employs a wireless direct measurement technology for the most difficult-to-measure kiln internal temperature. Wireless temperature measurement generates a temperature curve within the kiln, which corresponds to the direct quality parameters of the product. The difference between the real-time comparisons of the curve data is used as feedback data to adjust the flow rates of fuel and mixed concentrate, system pressure, and the rotational speed of the internally heated rotary kiln in real time, achieving precise system control. This upgrades the traditional slow feedback control mode to a more advanced synchronous control mode. Furthermore, isolation plates 29 are installed on the inner walls of the outer cylinder 301 in the kiln head section and middle section, corresponding to the sheath tube 30. Isolation plates 29 are also installed on the inner cylinder 302 in the kiln tail section, corresponding to the sheath tube 30. The isolation plates 29 prevent corrosive liquid materials from leaking out from the mounting holes of the temperature measuring mechanism. Further details can be found in the documentation. Figure 5 , Figure 8The sliding support assembly includes an outer cylinder support 21 and an inner cylinder support 23. The outer cylinder support 21 is fixedly connected to the outer cylinder 301, and the inner cylinder support 23 is fixedly connected to the inner cylinder 302. A waist-shaped hole is provided at the contact portion between the outer cylinder support 21 and the inner cylinder support 23. The waist-shaped hole is arranged parallel to the axis of the rotary kiln body 3. A connecting bolt 25 for connecting the outer cylinder support 21 and the inner cylinder support 23 is installed in the waist-shaped hole. A heat insulation sheet 22 is also provided between the outer cylinder support 21 and the inner cylinder support 23. When the kiln is working, the temperature of the inner cylinder 302 is much higher than that of the outer cylinder 301, resulting in a large temperature difference. Therefore, the inner cylinder 302 expands and elongates due to heat, causing a certain amount of sliding along the axial direction. When the inner cylinder 302 expands and elongates, the sliding between the inner cylinder support 23 and the outer cylinder support 21 meets production requirements. Furthermore, a corrosion-resistant, high-temperature-resistant, and high-strength adhesive is provided between the refractory bricks 24 and the inner cylinder 302, and between the brick joints of the refractory bricks 24. Furthermore, a plurality of prefabricated frames 17 are evenly distributed along the circumference of the kiln wall, and each prefabricated frame 17 has an outer layer with a heat insulation pad 16, which is tightly installed against the outer cylinder 301. Furthermore, a heat insulation material 303, made of lightweight aluminosilicate, is filled between the outer cylinder 301 and the inner cylinder 302. Further details can be found in the following section. Figure 7 The dynamic sealing device includes a connecting cylinder 6 located at the end of the kiln head hood 2. Two static sealing rings 7 are mounted on the connecting cylinder 6. A cooling ring 15 is mounted on the outer wall of the rotary kiln body 3. A dynamic sealing ring 8 is mounted on the outer wall of the cooling ring 15, located between the two static sealing rings 7. A conical cylinder is mounted on the outer static sealing ring 7. A graphite ring is mounted on the end of the conical cylinder closest to the cooling ring 15, and the graphite ring is in contact with the cooling ring 15. Further, a rigid pressure plate 11 is provided on the outer layer of the conical cylinder, and a sealing sheet 9 is provided on the inner layer. A flexible plate 10 is provided between the sealing sheet 9 and the rigid pressure plate 11. The graphite ring is mounted on the sealing sheet 9. A flexible pre-pressure ring 12 and a rigid pre-tension ring 13 are mounted on the outer side of the rigid pressure plate 11. Because the kiln head operates under a slight positive pressure, the high-temperature material after roasting is fed into the leaching tank through the feeding trough. This generates some expanding water vapor, which, carrying dust and acidic gases, is ejected from the kiln head orifices, resulting in a poor overall working environment. At the kiln tail end, acidic gases carrying overflowing acid liquid spill out from the kiln tail feed pipe, causing significant environmental impact and posing a safety hazard to personnel passing through. In this embodiment, both the kiln head hood 2 and the kiln tail are designed with a double-layer flexible sealing structure. The first layer uses a closed-cell annular seal filled with flexible material to isolate acidic gases, liquids, and dust generated during production. The second layer uses stainless steel sheets and flexible material pressed tightly against an insulating ring for sealing. The insulating ring is equipped with a wear-resistant layer and an air-cooling jacket to improve the service life of the insulating ring and the flexible material.

[0037] Further, see Figure 9-11The flue gas furnace described in this embodiment is a precision-controlled conditioning furnace, including a furnace body. A burner 116 is installed at one end of the furnace body. The burner 116 has a gas inlet and a primary air inlet 106. A regulating valve 105 is installed at the primary air inlet 106 to control the flow rate of the primary air 121. A flue gas nozzle 104 is installed at the other end of the furnace body, facing the calcining rotary kiln. A baffle plate is installed inside the furnace body near the burner 116, forming a gap between the baffle plate and the outer shell 108 of the furnace body. A cavity is provided, with a secondary air inlet 102 on one side of the cavity. Several external direct air ducts 114 are arranged circumferentially inside the furnace wall. The external direct air ducts 114 are arranged axially within the refractory material 110. The inlets of all external direct air ducts 114 are connected to the cavity, and the outlets extend to the flue gas nozzle 104. The secondary air 120 enters the cavity from the secondary air inlet 102 and flows through the external direct air ducts 114 to the flue gas nozzle 104, where it mixes with the high-temperature flue gas 123 to cool the high-temperature flue gas 123. Furthermore, the furnace wall is provided with several internal swirling air ducts 115 along its circumference. Each internal swirling air duct 115 is composed of a straight air duct and an inclined air duct connected together. The straight air duct is arranged along the axial direction of the furnace body, and its inlet is connected to the cavity. The inclined air duct has a 100° angle with the axis and a 100° angle with the radial line. The outlet of the inclined air duct is located in the rear half of the inner wall of the furnace body. After entering the furnace, each stream of internal swirling air 119 flows in the same direction. The beneficial effects of this design are that after the internal swirling air 119 enters the furnace, it cools the inner wall of the furnace on the one hand, and strengthens the combustion intensity of the flame on the other hand, improving the combustion rate of the fuel gas, enhancing the combustion effect, and reducing the generation of carbon monoxide. Furthermore, the baffle is provided with several internal direct-flow air ducts 113. The length of the internal direct-flow air duct 113 is equal to the thickness of the baffle. The inlet of the internal direct-flow air duct 113 is connected to the cavity, and the outlet is connected to the furnace chamber. Its beneficial effects are as follows: After the secondary air 120 enters the cavity, part of it passes through each inner direct current air duct 113 and directly enters the front end of the furnace to perform primary conditioning of the flue gas 123; part of it passes through each inner swirl air duct 115 and enters the rear end of the furnace to perform secondary conditioning of the flue gas 123; and part of it passes through each outer direct current air duct 114 and reaches the flue gas outlet 104 to perform tertiary conditioning of the flue gas 123 exiting the furnace. Through tertiary conditioning, the temperature of the flue gas 123 can be precisely controlled. Furthermore, the outer wall of the furnace body is composed of an outer shell 108 and an inner shell 109. The outer shell 108 and the inner shell 109 are hollow sandwich structures. An outer swirl air duct 112 is provided in the sandwich structure. An air inlet 101 is provided on the outer wall of the furnace body. The air inlet 101 is connected to the inlet of the outer swirl air duct 112. An outlet of the outer swirl air duct 112 is provided on the end face of the furnace body. The outlet of the outer swirl air duct 112 is connected to the primary air inlet 106 through a pipe. Furthermore, the external swirling air duct 112 is provided with a spiral baffle 111. Furthermore, the external swirling air duct 112 first diffuses and then converges from the inlet to the outlet.Its beneficial effects are as follows: When the primary air 121 passes through the outer swirl air duct 112, it absorbs the heat of the furnace body, which cools the furnace body on the one hand and preheats it on the other. The preheated primary air 121 enters the primary air inlet 106 through the pipe from the outer swirl air outlet 107, thereby improving the combustion effect.

[0038] See Figure 12 The flue gas temperature distribution map simulated by computer simulation software shows that the flue gas temperature distribution in the entire calcining rotary kiln is uniform and the temperature gradient change is small.

Claims

1. An energy-saving internally heated rare earth roasting kiln, comprising a rotary kiln body and a drive device, the drive device driving the rotary kiln body to rotate, a fixed kiln head hood being provided at the head of the rotary kiln body, openings at both ends of the kiln head hood, a dynamic sealing device being installed at one end of the kiln head hood facing the rotary kiln body, a flue gas furnace being installed at the other end of the kiln head hood, a discharge port being provided at the lower end of the kiln head hood, and a feed port being provided at the tail end of the rotary kiln body, characterized in that: The kiln head section of the rotary kiln includes an outer cylinder, inside which a kiln wall is cast. The working layer of the kiln wall is cast with high-alumina wear-resistant castable. The outer layer of the kiln wall is provided with heat-insulating castable. Several movable impact blocks are evenly distributed around the circumference of the inner ring of the middle part of the rotary kiln. The kiln tail section of the rotary kiln includes an outer cylinder and an inner cylinder. Several sliding support components are provided between the outer cylinder and the inner cylinder. The inner wall of the inner cylinder is covered with refractory bricks, and different refractory bricks are arranged in a staggered manner. The flue gas furnace includes a furnace body, a burner is installed at one end of the furnace body, the burner is provided with a gas inlet and a primary air inlet, and a flue gas outlet is provided at the other end, which is installed facing the calcining rotary kiln. A baffle is provided at one end of the furnace body near the burner, and a cavity is formed between the baffle and the outer shell of the furnace body. A secondary air inlet is provided on one side of the cavity. Several external direct current air ducts are provided along the circumference inside the furnace wall. The external direct current air ducts are arranged along the axial direction. The inlets of all external direct current air ducts are connected to the cavity, and the outlets extend to the flue gas outlet. The furnace wall is provided with several internal swirling air ducts along the circumference. Each internal swirling air duct is composed of a straight air duct and an inclined air duct connected together. The straight air duct is arranged along the axial direction of the furnace body. The inlet of the straight air duct is connected to the cavity. The inclined air duct has an angle of 100°-150° with the axis and an angle of 100°-150° with the radial line. The outlet of the inclined air duct is located in the rear half of the inner wall of the furnace body.

2. The energy-saving internal heating rare earth roasting kiln according to claim 1, characterized in that: The outer wall of the rotary kiln is provided with several sets of temperature measuring mechanisms along its entire length. Each set of temperature measuring mechanisms includes a mounting base fixed to the outside of the outer cylinder. The mounting base has a mounting hole, and a protective sleeve extending into the inner wall of the rotary kiln is installed in the mounting hole. A temperature sensor is installed in the protective sleeve, and a clamping flange is installed at the outer end of the temperature sensor. The clamping flange is connected to the mounting base by bolts.

3. The energy-saving internal heating rare earth roasting kiln according to claim 2, characterized in that: Isolation plates are installed on the inner wall of the outer cylinder at the kiln head section and the middle section where the temperature measuring mechanism is installed, corresponding to the sheath tube. Isolation plates are also installed on the inner cylinder at the kiln tail section where the temperature measuring mechanism is installed, corresponding to the sheath tube. The isolation plates are used to prevent corrosive liquid materials from leaking out from the mounting holes of the temperature measuring mechanism.

4. The energy-saving internal heating rare earth roasting kiln according to claim 1, characterized in that: The sliding support assembly includes an outer cylinder support and an inner cylinder support. The outer cylinder support is fixedly connected to the outer cylinder, and the inner cylinder support is fixedly connected to the inner cylinder. The contact portion between the outer cylinder support and the inner cylinder support is provided with an oblong hole. The oblong hole is arranged parallel to the axis of the rotary kiln body, and the oblong hole is filled with connecting bolts for connecting the outer cylinder support and the inner cylinder support.

5. The energy-saving internal heating rare earth roasting kiln according to claim 1, characterized in that: A corrosion-resistant, high-temperature-resistant, and high-strength adhesive is provided between the refractory bricks and the inner cylinder, and between the brick joints of the refractory bricks.

6. The energy-saving internal heating rare earth roasting kiln according to claim 1, characterized in that: The kiln wall is evenly distributed with several prefabricated frames along the circumference. Each prefabricated frame is provided with a heat insulation pad on its outer layer, and the heat insulation pad is installed in close contact with the outer cylinder.

7. The energy-saving internal heating rare earth roasting kiln according to claim 1, characterized in that: The space between the outer cylinder and the inner cylinder is filled with heat insulation material, which is made of lightweight aluminum silicate.

8. The energy-saving internal heating rare earth roasting kiln according to claim 1, characterized in that: The dynamic sealing device includes a connecting cylinder at the end of the kiln head hood, with two layers of static sealing rings mounted on the connecting cylinder. A cooling ring is mounted on the outer wall of the rotary kiln body, and a dynamic sealing ring is mounted on the outer wall of the cooling ring. The dynamic sealing ring is located between the two layers of static sealing rings. A conical cylinder is mounted on the outer static sealing ring, and a graphite ring is mounted on the end of the conical cylinder close to the cooling ring, with the graphite ring in contact with the cooling ring.

9. The energy-saving internal heating rare earth roasting kiln according to claim 8, characterized in that: The outer layer of the cone is provided with a rigid pressure plate, the inner layer is provided with a sealing sheet, and a flexible plate is provided between the sealing sheet and the rigid pressure plate. The graphite ring is installed on the sealing sheet, and a flexible preload ring and a rigid pretension ring are installed on the outer side of the rigid pressure plate.

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