A belt roasting machine production line with graded cooling of pellets

Abstract

The present invention discloses a belt roasting machine production line for graded cooling of pellets, comprising: a belt roasting machine, a first cold air duct, a second cold air duct and a heat recovery mechanism; the belt roasting machine comprises: a blast drying section, an exhaust drying section, a preheating section, a roasting section, a first cooling section and a second cooling section arranged in sequence along the processing movement direction of the pellets; the outlet of the blast drying section is connected to the inlet of a first cold air duct, and the outlet of a first cold air duct is connected to the first cooling section; the outlet of the first cooling section is connected to the inlet of the roasting section, and the outlet of the roasting section is connected to the inlet of the exhaust drying section through the heat recovery mechanism, and the outlets of the exhaust drying section, the preheating section and the roasting section are used to connect to the inlet of the exhaust gas exhaust system; the inlet of the second cold air duct is used to connect to the outlet of the cooling fan, and the outlet of the second cold air duct is connected to the second cooling section. This solution can effectively reduce the amount of waste gas emissions, thereby effectively reducing dust, SO2 and NO in the pellet production process. X The total amount of pollutants emitted can be reduced to achieve the effect of energy conservation and emission reduction.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy, in particular to a belt roasting machine production line for pellet graded cooling. Background Art

[0002] The belt roaster process is currently a primary pellet production process for steel and metallurgical enterprises. Exhaust gas emissions from this process are primarily composed of a main exhaust system and a furnace hood exhaust system. The furnace hood exhaust system primarily processes the hot air after the green pellets are dried. This exhaust gas primarily originates from the pellets being cooled in the cooling air duct, where they are converted to approximately 300°C hot air. This air then passes through a drying fan and into the strand section, where it blasts the wet bulbs to dry them. After removing moisture from the wet bulbs, the temperature drops to approximately 100°C. The air then passes through the furnace hood dust collector, where it meets emission standards.

[0003] According to GB 21256-2013, "Energy Consumption Limits per Unit Product for Major Processes in Crude Steel Production," the energy consumption per unit product of the pelletizing process must be ≤ 24kgce / t for new construction, renovation, or expansion. Furthermore, "through energy-saving technology upgrades and strengthened energy-saving management, efforts should be made to achieve an advanced value of ≤ 15kgce / t for the pelletizing process." Through the joint efforts of industry experts and scholars and the promotion of advanced equipment, the energy consumption of the pelletizing process in steel mills has now reached ≤ 20kgce / t, but this is still far from the advanced value of ≤ 15kgce / t.

[0004] Therefore, how to optimize the existing process and achieve energy conservation and emission reduction has become an important technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a pellet graded cooling belt roasting machine production line, which can effectively reduce the exhaust gas emission, thereby effectively reducing the dust, SO2 and NO in the pellet production process. X The total amount of pollutants emitted can be reduced to achieve the effect of energy conservation and emission reduction.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A pellet graded cooling belt roasting machine production line, comprising: a belt roasting machine, a first cooling air duct, a second cooling air duct and a heat recovery mechanism;

[0008] The belt roasting machine comprises: a blast drying section, an exhaust drying section, a preheating section, a roasting section, a cooling section one and a cooling section two, which are arranged in sequence along the direction of pellet processing movement;

[0009] The outlet of the blast drying section is connected to the inlet of the cold air duct, and the outlet of the cold air duct is connected to the cooling section;

[0010] The outlet of the cooling section is connected to the inlet of the roasting section, and the outlet of the roasting section is connected to the inlet of the exhaust drying section through the heat recovery mechanism. The outlets of the exhaust drying section, the preheating section, and the roasting section are used to connect to the inlet of the exhaust gas exhaust system.

[0011] The inlet of the second cooling air duct is used to connect to the outlet of the cooling fan, and the outlet of the second cooling air duct is connected to the second cooling section.

[0012] Preferably, it also includes: the exhaust gas exhaust system.

[0013] Preferably, the exhaust gas exhaust system includes: a main electrostatic precipitator and a main exhaust fan connected in sequence.

[0014] Preferably, the exhaust gas exhaust system further includes: a main exhaust gas main pipe, a denitrification and desulfurization system and a chimney.

[0015] Preferably, the heat recovery mechanism includes: a heat recovery main air duct and a heat recovery fan.

[0016] Preferably, it also includes: a drying fan;

[0017] The outlet of the second cooling stage is connected to the inlet of the blast drying stage through the blast drying fan.

[0018] Preferably, it also includes: a furnace hood cooling air blower;

[0019] The outlet of the blast drying section is connected to the inlet of the cold air pipe through the furnace cover cold air exhaust fan.

[0020] Preferably, it further comprises: a regulating valve; the first cold air duct and the second cold air duct are connected via the regulating valve;

[0021] Alternatively, the first cooling air duct and the second cooling air duct are connected as one to form a cooling air main duct.

[0022] Preferably, it also includes: the cooling fan.

[0023] Preferably, the controllers of the cooling fan, the main exhaust fan of the exhaust gas exhaust system, the heat recovery fan of the heat recovery mechanism, the blower fan and the furnace hood exhaust fan are all variable frequency controllers.

[0024] It can be seen from the above technical solution that the pellet graded cooling belt roasting machine production line provided by the present invention optimizes the existing belt roasting machine production process, reduces the exhaust gas emission by about 35%, and allows the sensible heat of this part of the exhaust gas to remain in the system, reducing the investment, operation and maintenance costs of equipment such as the furnace hood dust collector and the furnace hood chimney, and also reduces the capacity of the cooling fan, which can greatly reduce the energy consumption of the process and make a small contribution to reducing carbon emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 A schematic structural diagram of a belt roaster for pellet graded cooling provided by an embodiment of the present invention;

[0027] Figure 2 A schematic structural diagram of a 4 million ton belt roaster pellet production line provided by an embodiment of the present invention;

[0028] Figure 3 A schematic structural diagram of a 2 million ton belt roaster pellet production line provided by an embodiment of the present invention;

[0029] Figure 4 This is a schematic structural diagram of another 2 million ton belt roaster pellet production line provided by an embodiment of the present invention.

[0030] Among them, 10 is a belt roasting machine, 11 is a forced air drying section, 12 is an exhaust drying section, 13 is a roasting section, 14 is a cooling section 1, and 15 is a cooling section 2;

[0031] 21 is a first cold air duct, 22 is a second cold air duct;

[0032] 31 is a drying fan, 32 is a furnace hood cooling fan;

[0033] 40 is the main exhaust gas main pipe, 41 is the main electrostatic precipitator, 42 is the main exhaust fan, 43 is the denitrification and desulfurization system, and 44 is the chimney;

[0034] 51 is the heat recovery main air duct, and 52 is the heat recovery fan. DETAILED DESCRIPTION

[0035] First, the technical terms involved in this solution are explained as follows:

[0036] Belt roaster: a process equipment for pellet production;

[0037] Furnace hood dust collector: furnace hood exhaust gas emission treatment and purification equipment.

[0038] Cooling fan: provides cooling air to reduce the pellet temperature to a low temperature.

[0039] Blower drying fan: blows hot air from partially cooled pellets to dry wet pellets.

[0040] Main exhaust system: exhaust system for waste gas generated by roasting machine production (including main electrostatic precipitator, main exhaust fan, desulfurization and denitrification equipment, etc.).

[0041] 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.

[0042] After multiple project tests, the exhaust gas from the furnace hood has a temperature of about 100°C, an oxygen content of about 21%, and a small amount of SO2 and NO X (All emissions are within the national emission limits.) This waste gas is actually air. Using waste heat recovery equipment has a low output ratio, and direct emissions waste significant energy. Therefore, we use high-temperature pellet graded cooling technology to provide cooling air for the high-temperature pellets. When the pellets are cooled below 600°C, they are cooled with room-temperature air, ensuring the same cooling effect as traditional processes.

[0043] The pellet graded cooling belt roasting machine production line provided by the embodiment of the present invention includes: a belt roasting machine 10, a first cold air duct 21, a second cold air duct 22 and a heat recovery mechanism, the structure of which can refer to Figure 1 As shown;

[0044] The belt roasting machine 10 includes: a blast drying section 11, an exhaust drying section 12, a preheating section, a roasting section 13, a cooling section 14 and a cooling section 2 15, which are sequentially arranged along the pellet processing direction;

[0045] The outlet of the blast drying section 11 is connected to the inlet of a cold air duct 21, and the outlet of the cold air duct 21 is connected to the cooling section 15;

[0046] The outlet of the cooling section 13 is connected to the inlet of the roasting section 13, and the outlet of the roasting section 13 is connected to the inlet of the exhaust drying section 12 through a heat recovery mechanism. Part of the high-temperature exhaust gas from the roasting section 13 is sent to the exhaust drying section 12 through the heat recovery mechanism, and the outlet of the exhaust drying section 12 is used to connect to the inlet of the exhaust gas exhaust system. It should be noted that the flue gas from the roasting section is divided into two parts, one part is reheated and dried by the heat recovery mechanism, and the rest of the flue gas is directly discharged. The flue gas that needs to be discharged will be combined with the exhaust gas from the exhaust drying section and the preheating section and discharged together.

[0047] The inlet of the second cooling air duct 22 is used to connect to the outlet of the cooling fan 20 , and the outlet of the second cooling air duct 22 is connected to the second cooling section 15 .

[0048] Working process: After the green pellets enter the belt roaster and are produced as finished pellets, they pass through the blast drying section 11, exhaust drying section 12, preheating section, roasting section 13, soaking section, cooling section 14, and second cooling section 15. Finally, qualified pellets exit the roaster and enter the blast furnace. This patent divides the cooling duct into a primary cooling duct 21 and a secondary cooling duct 22. Cooling air from the cooling fan 20 enters the secondary cooling duct 22 and acts on the second cooling section 15. After cooling the pellets, the cooling air in the second cooling section 15 becomes hot air at approximately 300°C and enters the blast drying section 11 to remove moisture from the green pellets. The dried exhaust gas enters the primary cooling duct 21 and acts on the first cooling section 14 to cool the pellets, which are still at a high temperature of approximately 1000°C. The hot flue gas after cooling the pellets serves as secondary air for roasting. It mixes with the combustion gas to heat the pellets. After passing through the heat recovery mechanism, it enters the exhaust drying section 12 for cyclic drying and cooling, where its temperature drops to approximately 150°C. It is then treated by the exhaust gas exhaust system and discharged into the atmosphere. This solution reduces the emission of low-temperature exhaust gas by about 35% without affecting the main exhaust air emission requirements and the quality of pellet products. The corresponding dust, SO2 and NO X The total amount of emissions will be reduced, and the effect of energy conservation and emission reduction is self-evident.

[0049] It can be seen from the above technical solution that in the belt roasting machine production line with graded cooling of pellets provided by the embodiment of the present invention, the furnace hood exhaust gas that originally needed to be discharged does not need to be discharged externally, but is once again recycled into the roasting machine, thereby reducing the exhaust gas emission and making full use of the exhaust gas; thereby improving the heat utilization of the existing roasting machine and reducing energy consumption.

[0050] Specifically, one cold air duct 21 can be connected to 1-20 bellows, and the size of the bellows can be freely adjusted according to the process conditions.

[0051] The pellet graded cooling belt roasting machine production line provided by the embodiment of the present invention also includes: an exhaust gas exhaust system for treating the exhaust gas generated by the roasting machine production to reduce dust, SO2 and NO X emissions.

[0052] As a preferred embodiment, the exhaust gas exhaust system includes: a main electrostatic precipitator 41 and a main exhaust fan 42 connected in sequence, and the original furnace cover dust collector is cancelled. Figure 1 As shown, the outlet of the main electric precipitator 41 is connected to the inlet of the main exhaust fan 42. Specifically, the main electric precipitator 41 can be an electrostatic precipitator.

[0053] Furthermore, the exhaust gas exhaust system also includes: a main exhaust gas main pipe 40, a denitrification and desulfurization system 43, and a chimney 44. The outlet of the exhaust drying section 12 is connected to the inlet of the main exhaust gas main pipe 40, the outlet of the main exhaust gas main pipe 40 is connected to the inlet of the main electrostatic precipitator 41, the outlet of the main exhaust fan 42 is connected to the inlet of the denitrification and desulfurization system 43, the outlet of the denitrification and desulfurization system 43 is connected to the inlet of the chimney 44, and the outlet of the chimney 44 is discharged into the atmosphere.

[0054] Specifically, the heat recovery mechanism includes: a heat recovery main air duct 51 and a heat recovery fan 52. Its structure can be referred to Figure 1 As shown, the outlet of the roasting section 13 is connected to the inlet of the heat recovery main air duct 51 , and the outlet of the heat recovery main air duct 51 is connected to the inlet of the exhaust drying section 12 .

[0055] The pellet graded cooling belt roasting machine production line provided by the embodiment of the present invention further includes: a drying fan 31, the structure of which can refer to Figure 1 As shown;

[0056] The outlet of the second cooling section 15 is connected to the inlet of the blast drying section 11 through the blast drying fan 31. After the pellets are cooled in the second cooling section 15 of the cooling air duct and turned into about 300°C hot air, it passes through the blast drying fan 31 and enters the strand drying section blast drying 11 to dry the wet pellets.

[0057] The pellet graded cooling belt roasting machine production line provided by the embodiment of the present invention further includes: a furnace cover cooling air blower 32, the structure of which can refer to Figure 1 As shown;

[0058] The outlet of the blast drying section 11 is connected to the inlet of a cold air duct 21 through a furnace cover cooling air blower 32. The dried waste gas passes through the furnace cover cooling air blower 32 into the cold air duct 21 and enters the cooling section 14 to cool the high-temperature pellets at about 1000°C.

[0059] The pellet graded cooling belt roasting machine production line provided by the embodiment of the present invention further includes: a regulating valve 23, the structure of which can refer to Figure 1 As shown;

[0060] The first cooling air duct 21 and the second cooling air duct 22 are connected by a regulating valve 23. With this arrangement, the first cooling air duct 21 and the second cooling air duct 22 are connected by the regulating valve 23, and the air volume and air temperature of the first cooling section 14 and the second cooling section 15 can be adjusted according to production needs. Alternatively, the first cooling air duct 21 and the second cooling air duct 22 can be connected without the regulating valve 23 and can be integrated into a cooling air main duct, such as Figure 3 and Figure 4 shown.

[0061] The pellet graded cooling belt roasting machine production line provided by the embodiment of the present invention further includes a cooling fan 20. The cooling air from the cooling fan 20 enters the secondary cooling air duct 22 and acts on the secondary cooling section 15. After the cooling air in the secondary cooling section 15 cools the pellets, it becomes hot air at approximately 300°C.

[0062] Preferably, the controllers for the cooling fan 20, the main exhaust fan 42 of the exhaust system, the reheat fan 52 of the heat recovery mechanism, the blower fan 31, and the furnace hood exhaust fan 32 are all variable frequency controllers. To ensure production safety, the cooling fan capacity can be maintained without reducing it. Frequency conversion control is used. During normal production, the cooling fan load operates at approximately 20%, and in emergency situations, it operates at full load to prevent the finished pellets from overheating.

[0063] The present invention will be further described below with reference to specific embodiments:

[0064] Example 1, as Figure 2 As shown, take the 4 million tons belt roaster pellet production line as an example:

[0065] After 504t / h of green pellets enter the belt roaster, they pass through the blast drying section, exhaust drying section, preheating section, roasting section, soaking section cooling section one, and cooling section two, becoming qualified pellets that exit the roaster and enter the blast furnace. This patent divides the cooling air duct into the first cooling air duct and the second cooling air duct, which are connected by a regulating valve in the middle. The cooling fan (shown in the figure as the second cooling fan) is increased from the original 4000Kw, 1.5 million m 3 / h is adjusted to 2240Kw, 960,000m 3 / h. The cooling air enters the second cooling air duct and is distributed by the wind box. A small part enters the cooling stage 1 and a large part enters the cooling stage 2. After cooling the pellets, the cooling air in the cooling stage 2 becomes hot air at about 300℃ and passes through the drying fan 2240Kw, 960,000m 3 / h, enters the blast drying section to dry the moisture in the raw pellets. The dried exhaust gas passes through the furnace cover exhaust fan, and the wind pressure is adjusted from the original 5Kp to 8Kp. It then enters a cold air duct, and after being distributed by the wind box, all enters the cooling section to cool the high-temperature pellets at about 1000℃. The high-temperature flue gas after cooling the pellets is used as the secondary air for roasting the pellets. It is mixed with the gas and burned to heat the pellets. Part of it passes through the heat recovery fan and enters the exhaust drying section for circulation drying and cooling. After cooling, the temperature drops to about 150℃. 1.5 million m 3 / h of exhaust gas passes through the main electrostatic precipitator and the main exhaust fan into the desulfurization and denitrification system for treatment and then discharged into the atmosphere. The first cooling air duct and the second cooling air duct are connected by a regulating valve, which can adjust the air volume and air temperature of the first and second cooling sections according to production needs. 3 / h furnace hood exhaust gas does not need to be discharged, and the sensible heat of about 100℃ carried by the exhaust gas is returned to the roasting machine system to participate in the pellet roasting. Without affecting the main exhaust emission requirements and the quality of the pellet products, the low-temperature exhaust gas emissions are reduced by about 40%, and the corresponding dust, SO2 and NO X The total amount of emissions will be reduced, and the effect of energy conservation and emission reduction is self-evident.

[0066] Example 2, as Figure 3 As shown, take the 2 million tons belt roaster pellet production line as an example:

[0067] After 280t / h of green pellets enter the belt roaster, they pass through the blast drying section, exhaust drying section, preheating section, roasting section, soaking section cooling section one, and cooling section two, and then become qualified pellets that leave the roaster and enter the blast furnace. This patent uses only one cooling air main pipe, and the air from the furnace cover exhaust fan and the cold air from the second cooling fan are combined and enter the cooling air main pipe together to cool the pellets. The air volume of the cooling fan (shown as the second cooling fan in the figure) is increased from the original 810,000m 3 / h is adjusted to 600,000 m 3 / h. The cooling air and the exhaust gas from the furnace hood exhaust fan are combined and enter the cooling air main pipe. Before entering the cooling air main pipe, it passes through a check valve to prevent the exhaust gas from flowing back. After being distributed by the wind box, part of it enters the cooling stage 1 and part of it enters the cooling stage 2. After the cooling air enters the cooling stage 2 to cool the pellets, it becomes hot air at about 300℃ and passes through the drying fan 600,000m 3 / h, enters the blast drying section to dry the moisture in the raw balls. After the dried exhaust gas passes through the furnace hood exhaust fan, the wind pressure is adjusted from the original 5Kp to 8Kp, and then passes through the check valve to prevent it from mixing with the cooling air and enters the cooling air main pipe. After being distributed through the wind box, part of it enters the cooling section and part of it enters the cooling section. After entering the cooling section to cool the high-temperature pellets at about 1000℃, the high-temperature flue gas is used as the secondary air for roasting the pellets, and is mixed with the gas to burn and heat the pellets. Part of it passes through the heat recovery fan and enters the exhaust drying section for circulation drying and cooling, and the temperature drops to about 150℃. 990,000m 3 / h of exhaust gas passes through the main electrostatic precipitator and the main exhaust fan into the desulfurization and denitrification system for treatment and then discharged into the atmosphere. 3 / h furnace hood exhaust gas does not need to be discharged, and the sensible heat of about 100℃ carried by the exhaust gas is returned to the roasting machine system to participate in the pellet roasting. Without affecting the main exhaust emission requirements and the quality of the pellet products, the low-temperature exhaust gas emissions are reduced by about 40%, and the corresponding dust, SO2 and NO X The total amount of emissions will be reduced, and the effect of energy conservation and emission reduction is self-evident.

[0068] Example 3, as Figure 4 As shown, take the 2 million tons belt roaster pellet production line as an example:

[0069] After the 280t / h green pellets enter the belt roaster, they go through the blast drying section, exhaust drying section, preheating section, roasting section, soaking section, cooling section 1, cooling section 2, and then become qualified pellets that leave the roaster and enter the blast furnace. The air volume of this patented cooling fan is 810,000m 3 / h. The difference from Example 2 is that the fan outlet of the furnace hood exhaust fan is connected to the cold air inlet of the cooling fan, and after mixing, the cold air enters the cooling air main pipe to cool the pellets; after the cooling air enters the cooling air main pipe, part of it enters the first cooling section of the roasting chamber, and part of it enters the second cooling section of the roasting chamber. After cooling the pellets in the second cooling section, the cooling air becomes hot air at about 300℃ and passes through the 600,000m3 drying fan. 3 / h, entering the forced air drying section to dry out the moisture in the raw pellets. The dried exhaust gas passes through the furnace hood exhaust cooling fan, where the pressure is adjusted from 5kp to 8kp. It then mixes with air and enters the cooling fan, where the hot air circulates. After being distributed through the bellows, some enter the first cooling section and some enter the second cooling section. After cooling the high-temperature pellets at approximately 1000°C in the first cooling section, the high-temperature flue gas is used as secondary air for roasting the pellets, mixing with the fuel gas and burning to heat the pellets. A portion of the high-temperature flue gas passes through the reheat fan and enters the exhaust drying section, where it is circulated, dried, and cooled to approximately 150°C. The 990,000 m³ / h exhaust gas passes through the main electrostatic precipitator and main exhaust fan, enters the desulfurization and denitrification system for treatment, and is discharged into the atmosphere. In this scheme, the original 520,000 m3 / h of furnace hood exhaust gas does not need to be discharged. The sensible heat of about 100℃ carried by the exhaust gas is returned to the roaster system to participate in the pellet roasting. Without affecting the main exhaust emission requirements and the quality of the pellet products, the low-temperature exhaust gas emissions are reduced by about 40%, and the corresponding dust, SO2 and NO X The total amount of emissions will be reduced, and the effect of energy conservation and emission reduction is self-evident.

[0070] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0071] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A pellet graded cooling belt roasting machine production line, characterized in that: include: A belt roasting machine (10), a first cold air duct (21), a second cold air duct (22) and a heat recovery mechanism; The belt roasting machine (10) comprises: a blast drying section (11), an exhaust drying section (12), a preheating section, a roasting section (13), a first cooling section (14) and a second cooling section (15) which are sequentially arranged along the pellet processing movement direction; The outlet of the blast drying section (11) is connected to the inlet of the cold air pipe (21), and the outlet of the cold air pipe (21) is connected to the cooling section (14); The outlet of the cooling section (14) is connected to the inlet of the roasting section (13), and the outlet of the roasting section (13) is connected to the inlet of the exhaust drying section (12) through the heat recovery mechanism. The outlets of the exhaust drying section (12), the preheating section, and the roasting section (13) are used to connect to the inlet of the exhaust gas exhaust system. The inlet of the second cooling air duct (22) is used to connect to the outlet of the cooling fan (20), and the outlet of the second cooling air duct (22) is connected to the second cooling section (15); The system further comprises: a drying fan (31); the outlet of the cooling second section (15) is connected to the inlet of the drying section (11) through the drying fan (31); It also includes: a furnace cover cooling air blower (32); the outlet of the blast drying section (11) is connected to the inlet of the cold air pipe (21) through the furnace cover cooling air blower (32).

2. The pellet graded cooling belt roaster according to claim 1, characterized in that: The cold air pipe (21) is connected to 1-20 air boxes.

3. The pellet graded cooling belt roaster according to claim 1, characterized in that: Also includes: The exhaust gas exhaust system; The exhaust gas exhaust system comprises a main electrostatic precipitator (41) and a main exhaust fan (42) connected in sequence.

4. The pellet graded cooling belt roaster according to claim 3, characterized in that: The exhaust gas discharge system further comprises: a main exhaust gas main pipe (40), a denitrification and desulfurization system (43) and a chimney (44).

5. The pellet graded cooling belt roaster according to claim 1, characterized in that: The heat recovery mechanism comprises a heat recovery main air duct (51) and a heat recovery fan (52).

6. The pellet graded cooling belt roaster according to claim 1, characterized in that: Also includes: Regulating valve (23); the first cold air pipe (21) and the second cold air pipe (22) are connected via the regulating valve (23); Alternatively, the first cooling air duct (21) and the second cooling air duct (22) are connected as a whole to form a cooling air main duct.

7. The pellet graded cooling belt roaster according to claim 1, characterized in that: Also includes: The cooling fan (20).

8. The pellet graded cooling belt roaster according to claim 7, characterized in that: The controllers of the cooling fan (20), the main exhaust fan (42) of the exhaust gas exhaust system, the heat recovery fan (52) of the heat recovery mechanism, the blower fan (31) and the furnace hood exhaust fan (32) are all variable frequency controllers.

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