Energy-saving efficient pellet material drying, preheating and roasting production line

Abstract

The energy-saving efficient pellet material drying, preheating and roasting production line comprises a chain grate machine, a rotary kiln and an annular cooler, a kiln head bin of the rotary kiln is connected with one end of an annular cooling bin of the annular cooler in a sealed mode, and an inclined sliding plate is arranged in the kiln head bin; high-temperature pellets in the rotary kiln fall onto the cooling conveying plate chain through the inclined sliding plate, a roundabout fresh air heat exchange channel is arranged in the inclined sliding plate, and fresh air enters the fresh air heat exchange channel through the fresh air guide-in pipe under the power of the fresh air conveying fan and then enters the cooling conveying plate chain through the fresh air guide-in pipe. Fresh air exchanges heat with the high-temperature pellets on the inclined sliding plate in the fresh air heat exchange channel, and after heat exchange, the fresh air is guided into the heat exchange fresh air drying section of the chain grate through the hot air conveying pipe to dry the green pellets. The inclined sliding plate is additionally arranged in the kiln head bin of the rotary kiln, has a material guiding function and can effectively prevent generation of hydrogen chloride gas in the chain grate; and more importantly, the drying efficiency of the chain grate machine is also improved.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to an energy-saving and high-efficiency pellet material drying, preheating and roasting production line. Background Art

[0002] Pellet material is a high-quality raw material for blast furnace ironmaking. Compared with sintered ore, the production of pellet material has the characteristics of low energy consumption, good strength, high grade and excellent metallurgical properties. The production of pellet material in my country is mainly based on the chain grate-rotary kiln process, and the pellet production of this process accounts for more than 60% of the total pellet production.

[0003] The process of producing pellets using the chain grate-rotary kiln equipment is as follows: the raw pellets are first dried and pre-baked by the chain grate, and then sent to the rotary kiln by the chain grate to bake the pre-baked pellets at a higher temperature. After baking, the high-temperature pellets enter the ring cooler for cooling to form pellets for steel smelting. The chain grate is divided into blast drying section, exhaust drying section, preheating section I, and preheating section II in sequence, and the cooling process of the ring cooler is divided into ring cooler section I, ring cooler section II, ring cooler section III, and ring cooler section IV in sequence. The chain grate preheating section II is connected to the tail of the rotary kiln, and the head of the rotary kiln is connected to the first section of the ring cooler. The hot air between the chain grate, rotary kiln and ring cooler is mutually utilized to achieve effective energy saving in the pellet production process. The chain grate-rotary kiln equipment has the characteristics of large single-machine production capacity, wide application of raw materials, and abundant fuel resources. However, the chain grate-rotary kiln equipment in the prior art has the following shortcomings: First, the green pellets contain chlorine-containing soluble salts such as sodium chloride and potassium chloride; the hot air used to dry the green pellets through the grate machine comes from the circulating hot air of the grate machine preheating stage II, which contains relatively high concentrations of sulfur dioxide and nitrogen oxide gases; the sulfur dioxide in the high-temperature flue gas in the exhaust drying stage reacts with the chlorine-containing salts in the undried green pellets to generate hydrogen chloride gas. The typical reaction equation is shown in formula (1). The hydrogen chloride gas finally generated enters the main flue and causes corrosion and blockage of the purification tower.

[0004] 2SO2+2H2O+O2+4NaCl=2Na2SO4+4HCl Formula (1) In order to reduce or inhibit the generation of hydrogen chloride gas, the contact between the undried water-containing raw balls and the flue gas rich in sulfur dioxide components should be reduced in the chain grate. Patent CN103335522A discloses a hot air system for the blast drying section of the chain grate, in which the hot air from the third section of the ring cooler is supplied to the blast drying section of the chain grate, the hot air from the second section of the ring cooler is supplied to the exhaust drying section, and the hot air from the second section of the ring cooler is partially supplemented to the blast drying section to increase the temperature of the blast drying section and improve the drying effect of the blast drying section. However, since the hot air from the third section of the ring cooler and the hot air from the second section of the ring cooler are in direct contact with the calcined pellets and dust, at this time, the hot air from the third section of the ring cooler and the hot air from the second section of the ring cooler have been contaminated, and a small amount of SO2 will still be contained in the hot air.

[0005] Second, in the prior art, the drying section of the chain grate machine has a low hot air temperature, so the drying efficiency still has room for improvement, and the drying efficiency needs to be further improved.

[0006] Third, during the higher temperature roasting process of the pre-roasted pellets in the rotary kiln, rings are easily formed on the inner wall of the rotary kiln. The widespread ringing problem has become the biggest problem of this equipment. Whether it is a chain grate machine-rotary kiln equipment that uses gas or coal as fuel, there is a ringing problem, especially when coal is used as fuel. In the production of rotary kilns, ringing is a common accident that hinders production, that is, a thick layer of material formed by the consolidation of pellet powder is attached to the inner wall of the rotary kiln refractory material.

[0007] Fourth, during the transportation of the pellets, a large amount of dust is generated due to the large height difference; especially, the hot air of the preheating section I of the chain grate machine comes from the preheating section II (pre-calcining section), and the hot air in the preheating section II (pre-calcining section) comes from the rotary kiln. The hot air in the rotary kiln has a lot of dust. The hot air in the rotary kiln heats or pre-calcines the preheating section II (pre-calcining section), which is closer to the temperature of the rotary kiln. There is no problem with this design, but it is not reasonable to transport the hot air of the preheating section II (pre-calcining section) to the preheating section I of the chain grate machine, because the amount of dust in the hot air of the preheating section II (pre-calcining section) is too large. Summary of the invention

[0008] The purpose of the present invention is to provide an energy-saving and high-efficiency pellet material drying, preheating and roasting production line.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is: An energy-saving and high-efficiency pellet drying, preheating and roasting production line, including a chain grate, a rotary kiln and an annular cooler. After being dried and pre-baked by a chain grate, the raw pellets enter a rotary kiln for high-temperature calcination. After high-temperature calcination, the high-temperature pellets enter an annular cooler for cooling. The chain grate is sequentially divided into a heat exchange fresh air drying section, a preheating section, and a pre-baking section. The kiln head bin of the rotary kiln is tightly connected to one end of the annular cooling bin of the annular cooler. The feeding end of the cooling conveyor plate chain in the annular cooling bin is located in the kiln head bin. An inclined slide plate is provided in the kiln head bin. The high-temperature pellets in the rotary kiln fall onto the cooling conveyor plate chain through the inclined slide plate. A circuitous fresh air heat exchange channel is provided in the inclined slide plate, a fresh air introduction pipe is connected to the air inlet of the fresh air heat exchange channel, and the air outlet of the fresh air heat exchange channel is connected to the air inlet of the heat exchange fresh air drying section through a hot air delivery pipe. Under the power of the fresh air delivery fan, the fresh air enters the fresh air heat exchange channel through the fresh air introduction pipe, and the fresh air exchanges heat with the high-temperature pellets on the inclined slide plate in the fresh air heat exchange channel. After the heat exchange, the fresh air is introduced into the heat exchange fresh air drying section through the hot air delivery pipe to dry the raw pellets.

[0010] Furthermore, the heat exchange fresh air drying section is divided into heat exchange fresh air drying section I, heat exchange fresh air drying section II and a drying conveying fan. The fresh air after heat exchange enters the heat exchange fresh air drying section II, and the drying conveying fan draws the heat exchange fresh air in the heat exchange fresh air drying section II into the heat exchange fresh air drying section I.

[0011] Furthermore, the chain grate machine also includes a plate chain conveyor belt and a dust removal device, the dust removal device is used to clean the dust on the surface of the plate chain conveyor belt, the dust removal device includes a primary dust removal bin, a secondary dust removal bin, a tertiary dust removal bin, a first exhaust fan, a second exhaust fan and a cyclone-type gas-dust separator, the plate chain conveyor belt sequentially passes through the primary dust removal bin, the secondary dust removal bin and the tertiary dust removal bin, under the power of the first exhaust fan, the dust removal airflow enters the primary dust removal bin and passes through the plate chain conveyor belt in the primary dust removal bin to enter the secondary dust removal bin, under the power of the second exhaust fan, the dust removal airflow sequentially passes through the plate chain conveyor belt in the secondary dust removal bin and the plate chain conveyor belt in the tertiary dust removal bin, the airflow discharged from the tertiary dust removal bin enters the cyclone-type gas-dust separator for gas-dust separation, the separated dust falls into the dust collection bin, and the separated exhaust gas is sent to the exhaust gas treatment tower.

[0012] Furthermore, the dust removal airflow is the air discharged from the air outlet of the heat exchange fresh air drying section I.

[0013] Furthermore, the ring cooler includes a first ring cooler section, a second ring cooler section, a third ring cooler section, a fourth ring cooler section, a first cooling air fan and a second cooling air fan. The first cooling air fan sends cooling air into the fourth ring cooler section and passes through the cooling conveying plate chain in the fourth ring cooler section, and then flows into the third ring cooler section. Under the power of the second cooling air fan, the cooling air passes through the cooling conveying plate chain in the third ring cooler section and the cooling conveying plate chain in the second ring cooler section in turn, and flows into the first ring cooler section.

[0014] Furthermore, the ring cooler also includes a heat flow conveying fan, which extracts the hot air flow in one section of the ring cooler and divides it into two paths: one path is sent to the kiln head bin, and after being heated by the rotary kiln, it enters the pre-baking section of the chain grate machine to pre-bake the green pellets; the other path is sent to the preheating section of the chain grate machine to preheat the green pellets.

[0015] Furthermore, the waste gas in the preheating section and pre-calcining section of the chain grate is sent to a cyclone dust collector for dust removal through a vacuum pump, and the gas discharged from the cyclone dust collector is sent to the waste gas treatment tower.

[0016] Furthermore, a multi-stage heat exchanger is provided in the exhaust gas treatment tower to recover waste heat in the exhaust gas.

[0017] Furthermore, the inner wall surface of the rotary kiln is paved with a refractory brick layer, and the surface of the refractory brick layer is paved with a nano-scale anti-ringing layer with a roughness of 0.2-0.4 μm.

[0018] Furthermore, the nano-scale anti-ringing layer is made of nano-scale zircon sand material, and the thickness of the nano-scale anti-ringing layer is 0.8-1.2 mm.

[0019] The beneficial effects of the present invention are: First, the present application adds an inclined slide plate in the kiln head bin of the rotary kiln. The inclined slide plate has a material guiding function, thereby avoiding the generation of large dust due to the large drop of the pellet material. In particular, the inclined slide plate also has the function of cooling and exchanging heat for the roasted pellet material. The inclined slide plate heats the external fresh air and directly transmits it to the drying section of the chain grate. The fresh air is clean air that is not polluted by the pellet material and dust. Therefore, it can effectively prevent the generation of hydrogen chloride gas in the chain grate; more importantly, it also improves the drying efficiency of the chain grate.

[0020] Second, the present application allows the cold air entering the ring cooler to pass through the fourth section, the third section, the second section, and the first section of the ring cooler in sequence, and the cold air forms a high-temperature airflow, which is then transported to the preheating section of the chain grate machine. The hot air discharged from the pre-baking section of the chain grate machine is input into the cyclone dust collector for dust removal, and then waste heat is recovered, thereby greatly reducing the amount of dust in the chain grate machine.

[0021] Third, the present application lays a nano-scale anti-ringing layer on the surface of the refractory brick layer in the rotary kiln. The nano-scale anti-ringing layer has the characteristics of low roughness and no adhesion to low-melting-point substances, thereby solving the ringing problem existing in the rotary kiln equipment, especially when coal is used as fuel, the serious ringing phenomenon is alleviated, and in the production of the rotary kiln, the production reduction, shutdown and safety accidents caused by ringing are avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is further described with the aid of the accompanying drawings, but the embodiments in the accompanying drawings do not constitute any limitation to the present invention. A person skilled in the art can obtain other accompanying drawings according to the following drawings without creative work: Figure 1 A schematic diagram of the structure of the invention; Figure 2 for Figure 1 Schematic diagram of the internal structure of the rotary kiln shown.

[0023] In the figure: 1. chain grate; 2. rotary kiln; 3. ring cooler; 4. exhaust gas treatment tower; 5. inclined slide plate; 6. fresh air inlet pipe; 7. hot air conveying pipe; 8. fresh air conveying fan; 9. dust removal device; 10. green pellets; 101. heat exchange fresh air drying section I; 102. heat exchange fresh air drying section II; 103. preheating section; 104. pre-calcining section; 105. drying conveying fan; 106. plate chain conveyor belt; 107. vacuum pump; 108. cyclone dust collector; 201. kiln head warehouse; 202. refractory brick layer; 2 03. Nano-scale anti-ringing layer; 301. Annular cooler section 1; 302. Annular cooler section 2; 303. Annular cooler section 3; 304. Annular cooler section 4; 305. First cooling air fan; 306. Second cooling air fan; 307. Heat transfer fan; 308. Cooling conveyor plate chain; 401. Multi-stage heat exchanger; 501. Fresh air heat exchange channel; 901. First dust removal bin; 902. Second dust removal bin; 903. Third dust removal bin; 904. First exhaust fan; 905. Second exhaust fan; 906. Cyclone gas-dust separator. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features therein can be combined with each other without conflict.

[0025] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper surface", "lower surface", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "forward", "reverse", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0026] like Figure 1As shown, an energy-saving and high-efficiency pellet material drying, preheating and roasting production line includes a chain grate 1, a rotary kiln 2 and an annular cooler 3. After being dried and pre-roasted by the chain grate 1, the green pellets 10 enter the rotary kiln 2 for high-temperature roasting. After high-temperature roasting, the high-temperature pellets enter the annular cooler 3 for cooling. The chain grate 1 is sequentially divided into a heat exchange fresh air drying section, a preheating section 103, and a pre-roasting section 104. The heat exchange fresh air drying section is divided into a heat exchange fresh air drying section I 101, a heat exchange fresh air drying section II 102 and a drying and conveying fan 105. The kiln head bin 201 of the rotary kiln 2 is tightly connected to one end of the ring cooling bin of the ring cooling machine 3. The feeding end of the cooling conveyor plate chain 308 in the ring cooling bin 3 is located in the kiln head bin 201. An inclined slide plate 5 is provided in the kiln head bin 201. The high-temperature pellets in the rotary kiln 2 fall onto the cooling conveyor plate chain 308 through the inclined slide plate 5. A circuitous fresh air heat exchange channel 501 is provided in the inclined slide plate 5. The fresh air introduction pipe 6 is connected to the air inlet of the fresh air heat exchange channel 501. The air outlet of the fresh air heat exchange channel 501 is connected to the fresh air inlet. The superheated air conveying pipe 7 is connected to the air inlet of the heat exchange fresh air drying II section 102. Under the power of the fresh air conveying fan 8, the fresh air enters the fresh air heat exchange channel 501 through the fresh air inlet pipe 6. The fresh air exchanges heat with the high-temperature pellets on the inclined slide 5 in the fresh air heat exchange channel 501. After the heat exchange, the fresh air enters the heat exchange fresh air drying II section 102 to dry the raw pellets. The drying conveying fan 105 draws the heat exchange fresh air in the heat exchange fresh air drying II section 102 into the heat exchange fresh air drying I section 101 to pre-dry the raw pellets. The present application adds an inclined slide plate 5 in the kiln head bin of the rotary kiln. The inclined slide plate 5 has a material guiding function, thereby avoiding the generation of large dust due to the large drop of the pellet material. In particular, the inclined slide plate 5 also has the function of cooling and exchanging heat for the roasted pellet material. The inclined slide plate 5 heats the external fresh air and directly transmits it to the drying section of the chain grate. The fresh air is clean air that is not polluted by the pellet material and dust. Therefore, it can effectively prevent the generation of hydrogen chloride gas in the chain grate; more importantly, it also improves the drying efficiency of the chain grate.

[0027] The chain grate 1 also includes a plate chain conveyor belt 106 and a dust removal device 9, the dust removal device is used to clean the dust on the surface of the plate chain conveyor belt 106, the dust removal device 9 includes a primary dust removal bin 901, a secondary dust removal bin 902, a tertiary dust removal bin 903, a first exhaust fan 904, a second exhaust fan 905 and a cyclone dust separator 906, the plate chain conveyor belt 106 passes through the primary dust removal bin 901, the secondary dust removal bin 902, and the tertiary dust removal bin 903 in sequence, and the first exhaust fan 904 is used to move the first exhaust fan 904. Under the power of the second exhaust fan 905, the dust removal airflow enters the primary dust removal bin 901 and passes through the plate chain conveyor belt in the primary dust removal bin 901 to enter the secondary dust removal bin 902. Under the power of the second exhaust fan 905, the dust removal airflow passes through the plate chain conveyor belt in the secondary dust removal bin 902 and the plate chain conveyor belt in the tertiary dust removal bin 903 in sequence. The airflow discharged from the tertiary dust removal bin 903 enters the cyclone type air-dust separator 906 for air-dust separation. The separated dust falls into the dust collection bin, and the separated waste gas is sent to the waste gas treatment tower 4. The dust removal airflow is the air discharged from the air outlet of the heat exchange fresh air drying section I 101.

[0028] The present invention adds a dust removal device 9 to the chain grate 1, which can effectively remove dust on the plate chain conveyor belt 106.

[0029] The annular cooler 3 comprises annular cooler section 1 301, annular cooler section 2 302, annular cooler section 303, annular cooler section 4 304, a first cooling air fan 305 and a second cooling air fan 306. The first cooling air fan 305 delivers cooling air into the annular cooler section 4 304 and passes through the cooling conveying plate chain in the annular cooler section 4 before flowing into the annular cooler section 303. Under the power of the second cooling air fan 306, the cooling air passes through the cooling conveying plate chain in the annular cooler section 303 and the cooling conveying plate chain in the annular cooler section 2 302 in sequence and flows into the annular cooler section 1 301.

[0030] The ring cooler 3 also includes a heat flow conveying fan 307, which extracts the hot air flow in the first section 301 of the ring cooler and divides it into two paths: one path is sent to the kiln head bin 201, and after being heated by the rotary kiln 2, it enters the pre-baking section 104 of the chain grate machine 1 to pre-bake the green pellets; the other path is sent to the preheating section 103 of the chain grate machine 1 to preheat the green pellets. The waste gas in the preheating section 103 and the pre-baking section 104 of the chain grate machine 1 is sent to the cyclone dust collector 108 for dust removal through the exhaust pump 107, and the gas discharged from the cyclone dust collector 108 is sent to the waste gas treatment tower 4.

[0031] The exhaust gas treatment tower 4 is provided with a multi-stage heat exchanger 401 for recovering waste heat in the exhaust gas.

[0032] In the present application, the cold air entering the ring cooler passes through the fourth section, the third section, the second section and the first section of the ring cooler in sequence, and the cold air forms a high-temperature airflow, and the high-temperature airflow is transported to the preheating section of the chain grate machine. The hot air discharged from the pre-baking section of the chain grate machine is input into the cyclone dust collector for dust removal, and then the waste heat is recovered, thereby greatly reducing the amount of dust in the chain grate machine.

[0033] like Figure 2 As shown, the inner wall of the rotary kiln 2 is paved with a refractory brick layer 202, and the surface of the refractory brick layer 202 is paved with a nano-scale anti-ringing layer 203 with a roughness of 0.2-0.4μm. The nano-scale anti-ringing layer 203 is made of nano-scale zircon sand material, and the thickness of the nano-scale anti-ringing layer 203 is 0.8-1.2mm. The present application utilizes a short-pulse laser processing system to lay a nano-scale anti-ringing layer on the surface of the refractory brick layer in the rotary kiln. The nano-scale anti-ringing layer has the characteristics of low roughness and no adhesion to low-melting-point substances, thereby solving the ringing problem existing in the rotary kiln equipment, especially when coal is used as fuel, the serious ringing phenomenon is alleviated, and in the production of the rotary kiln, the reduction of production, suspension of production and safety accidents caused by ringing are avoided.

[0034] In addition, those skilled in the art may combine and combine the different embodiments or examples and the features of the different embodiments or examples described in this specification without contradiction. Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. An energy-saving and high-efficiency pellet drying, preheating and roasting production line, including a chain grate, a rotary kiln and an annular cooler. After being dried and pre-baked by a chain grate, the green pellets enter a rotary kiln for high-temperature calcination. After high-temperature calcination, the high-temperature pellets enter an annular cooler for cooling. The characteristics are: The chain grate machine is divided into a heat exchange fresh air drying section, a preheating section, and a pre-baking section in sequence. The kiln head bin of the rotary kiln is tightly connected to one end of the ring cooling bin of the ring cooling machine. The feeding end of the cooling conveying plate chain in the ring cooling bin is located in the kiln head bin. An inclined slide plate is provided in the kiln head bin. The high-temperature pellets in the rotary kiln fall onto the cooling conveying plate chain through the inclined slide plate. A circuitous fresh air heat exchange channel is provided in the inclined slide plate. A fresh air introduction pipe is connected to the air inlet of the fresh air heat exchange channel. The air outlet of the fresh air heat exchange channel is connected to the air inlet of the heat exchange fresh air drying section through a hot air conveying pipe. Under the power of the fresh air conveying fan, fresh air enters the fresh air heat exchange channel through the fresh air introduction pipe. The fresh air exchanges heat with the high-temperature pellets on the inclined slide plate in the fresh air heat exchange channel. After heat exchange, the fresh air is introduced into the heat exchange fresh air drying section through the hot air conveying pipe to dry the raw pellets.

2. The energy-saving and high-efficiency pellet drying, preheating and roasting production line according to claim 1 is characterized in that: The heat exchange fresh air drying section is divided into heat exchange fresh air drying section I, heat exchange fresh air drying section II and a drying conveying fan. The fresh air after heat exchange enters the heat exchange fresh air drying section II, and the drying conveying fan draws the heat exchange fresh air in the heat exchange fresh air drying section II into the heat exchange fresh air drying section I.

3. The energy-saving and high-efficiency pellet drying, preheating and roasting production line according to claim 2 is characterized in that: The chain grate machine also includes a plate chain conveyor belt and a dust removal device, the dust removal device is used to clean the dust on the surface of the plate chain conveyor belt, the dust removal device includes a primary dust removal bin, a secondary dust removal bin, a tertiary dust removal bin, a first exhaust fan, a second exhaust fan and a cyclone-type gas-dust separator, the plate chain conveyor belt sequentially passes through the primary dust removal bin, the secondary dust removal bin and the tertiary dust removal bin, under the power of the first exhaust fan, the dust removal airflow enters the primary dust removal bin and passes through the plate chain conveyor belt in the primary dust removal bin to enter the secondary dust removal bin, under the power of the second exhaust fan, the dust removal airflow sequentially passes through the plate chain conveyor belt in the secondary dust removal bin and the plate chain conveyor belt in the tertiary dust removal bin, the airflow discharged from the tertiary dust removal bin enters the cyclone-type gas-dust separator for gas-dust separation, the separated dust falls into the dust collection bin, and the separated waste gas is sent to the waste gas treatment tower.

4. The energy-saving and high-efficiency pellet drying, preheating and roasting production line according to claim 3 is characterized in that: The dust removal airflow is the air discharged from the air outlet of the heat exchange fresh air drying section I.

5. The energy-saving and high-efficiency pellet drying, preheating and roasting production line according to claim 4 is characterized in that: The ring cooler includes a first ring cooler section, a second ring cooler section, a third ring cooler section, a fourth ring cooler section, a first cooling air fan and a second cooling air fan. The first cooling air fan sends cooling air into the fourth ring cooler section and passes through the cooling conveying plate chain in the fourth ring cooler section, and then flows into the third ring cooler section. Under the power of the second cooling air fan, the cooling air passes through the cooling conveying plate chain in the third ring cooler section and the cooling conveying plate chain in the second ring cooler section in turn, and flows into the first ring cooler section.

6. The energy-saving and high-efficiency pellet drying, preheating and roasting production line according to claim 5 is characterized in that: The ring cooler also includes a heat flow conveying fan, which extracts the hot air flow in one section of the ring cooler and divides it into two paths: one path is sent to the kiln head bin, and after being heated by the rotary kiln, it enters the pre-baking section of the chain grate machine to pre-bake the green pellets; the other path is sent to the preheating section of the chain grate machine to preheat the green pellets.

7. The energy-saving and high-efficiency pellet drying, preheating and roasting production line according to claim 6 is characterized in that: The waste gas in the preheating section and the pre-baking section of the chain grate is sent to the cyclone dust collector for dust removal through a vacuum pump, and the gas discharged from the cyclone dust collector is sent to the waste gas treatment tower.

8. The energy-saving and high-efficiency pellet drying, preheating and roasting production line according to claim 7 is characterized in that: The exhaust gas treatment tower is provided with a multi-stage heat exchanger for recovering the waste heat in the exhaust gas.

9. The energy-saving and high-efficiency pellet drying, preheating and roasting production line according to claim 1 is characterized in that: The inner wall surface of the rotary kiln is paved with a refractory brick layer, and the surface of the refractory brick layer is paved with a nano-scale anti-ringing layer with a roughness of 0.2-0.4 μm.

10. The energy-saving and high-efficiency pellet drying, preheating and roasting production line according to claim 9 is characterized in that: The nano-scale anti-ringing layer is made of nano-scale zircon sand material, and the thickness of the nano-scale anti-ringing layer is 0.8-1.2 mm.

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