Apparatus and method for producing pellets using low calorific value gas

Abstract

The application discloses a device for producing pellets by using low-calorific-value gas, which comprises a blast drying section, an exhaust drying section, a preheating section, a baking section, a soaking section and a cooling section which are sequentially and separately arranged, the cooling section is divided into a first cooling section, a second cooling section and a third cooling section which are sequentially arranged, the first cooling section is arranged close to the soaking section, waste gas of the soaking section is communicated with a first air bellow of the first cooling section through a first pipeline, the first air bellow is communicated with a cooling pipeline, hot air of the first cooling section flows to the baking section and the soaking section, the baking section is provided with a first low-calorific-value fuel burner, and an air-fuel ratio of the first low-calorific-value fuel burner is 4-7. The device for producing pellets by using low-calorific-value gas can realize high-temperature baking and solidification of the pellets by using low-calorific-value fuel, and the processing cost of the pellets is reduced. The application further provides a method for producing pellets by using low-calorific-value gas.

Description

Technical Field

[0001] This invention relates to the field of pellet production technology, and in particular to an apparatus and method for producing pellets using low-calorific-value fuel gas. Background Technology

[0002] Iron ore pellets, as a high-quality iron-containing raw material, are mainly used in ironmaking production. Due to their low energy consumption and environmental friendliness, they are increasingly favored by steel companies. In pellet production, belt roasters are the mainstream equipment due to their high production capacity. Belt roasters can efficiently produce various green products such as acidic and flux-modified pellets with good technical and economic indicators. When pellets are produced in a belt roaster, they need to complete the drying, preheating, roasting, homogenization, and cooling processes sequentially. Therefore, belt roasters are divided into process sections according to their functions. Current technology typically divides belt roasters into seven process sections: forced-air drying section, exhaust drying section, preheating section, roasting section, homogenization section, cooling section one, and cooling section two.

[0003] In existing technologies, belt roasters for producing ore pellets require the combustion of high-calorific-value fuel gas for drying, preheating, heating, and roasting. Coke oven gas or natural gas is typically used. The cooling section of existing belt roasters is divided into two stages. In the first stage, ambient-temperature air is blown in to cool the pellets, and the resulting high-temperature flue gas mainly circulates to the preheating and roasting stages, typically at temperatures of 800℃ to 950℃. Combustion primarily uses high-calorific-value fuel gas, usually coke oven gas or natural gas. However, the excessive gas volume in the first stage leads to an excessively high air-fuel ratio in the coke oven gas or natural gas combustion reaction, generally in the range of 8 to 12. This results in excessive heat being used to heat too much flue gas, leading to energy waste. Simultaneously, common metallurgical gases such as blast furnace gas and converter gas, being low-calorific-value fuels, cannot achieve the required high-temperature roasting and solidification of the pellets due to their low calorific value, insufficient heat supply, and combustion temperature. Therefore, the reliance on high-calorific-value natural gas or coke oven gas leads to increased processing costs for iron ore pellets. Summary of the Invention

[0004] In view of this, the present invention provides an apparatus for producing pellets using low-calorific-value fuel gas. By using hot air cooling and reducing the air-fuel ratio, high-temperature roasting and solidification of pellets can be achieved using low-calorific-value fuel, thereby reducing the processing cost of pellets.

[0005] The present invention also provides a method for producing ore pellets using low-calorific-value fuel gas.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An apparatus for producing ore pellets using low-calorific-value fuel gas includes a blower drying section, an exhaust drying section, a preheating section, a roasting section, a homogenizing section, and a cooling section arranged sequentially and separately. The cooling section is characterized by being divided into a first cooling section, a second cooling section, and a third cooling section arranged sequentially. The first cooling section is located close to the homogenizing section. The exhaust gas from the homogenizing section is connected to a first air box in the first cooling section via a first pipeline. The first air box is connected to a cooling pipeline, which supplies a predetermined amount of ambient temperature air to the first cooling section. The hot air from the first cooling section flows to the roasting section and the homogenizing section. The roasting section is equipped with a first low-calorific-value fuel burner. The hot flue gas from the first cooling section provides oxygen for combustion in the first low-calorific-value fuel burner. The fuel for the first low-calorific-value fuel burner is low-calorific-value fuel gas, and the air-fuel ratio of the first low-calorific-value fuel burner is 4-7.

[0008] Optionally, a second air box is provided at the air inlet end of the second cooling section. The second air box is connected to the cooling pipeline. The cooling pipeline is used to supply room temperature air to the second cooling section. The hot air heated by the second cooling section is connected to the end of the preheating section near the calcination section through the second pipeline.

[0009] The hot exhaust gas generated in the roasting section is connected to one end of the preheating section near the exhaust drying section through a reheating pipeline.

[0010] A regenerative air fan is installed on the regenerative pipeline;

[0011] A cooling fan is installed on the cooling pipeline.

[0012] Optionally, the end of the regenerating pipeline away from the calcination section includes a first regenerating branch pipe and a second regenerating branch pipe, wherein the first regenerating branch pipe is connected to the preheating section and the second regenerating branch pipe is connected to the exhaust drying section.

[0013] Optionally, the exhaust gas from the exhaust drying section and the preheating section is connected to the desulfurization and denitrification equipment through a third pipeline, and the exhaust gas from the third pipeline is discharged after being treated by the desulfurization and denitrification equipment;

[0014] The third pipeline is equipped with a main exhaust fan.

[0015] Optionally, a fourth air box is provided at the exhaust gas end of the exhaust drying section and the preheating section, and the exhaust gas of both is discharged into the fourth air box, and the third pipeline is connected to the fourth air box;

[0016] The fourth air box is connected to the fifth air box at the exhaust end of the roasting section via a fourth pipeline, and a first valve is installed on the fourth pipeline.

[0017] Optionally, a second low-calorific-value fuel burner is provided at one end of the preheating section near the roasting section;

[0018] The hot air in the second cooling section provides the oxygen required for combustion to the second low-calorific-value fuel burner, which uses low-calorific-value fuel gas as fuel.

[0019] Optionally, the air outlet of the three cooling sections is connected to the air inlet of the blower drying section through a fifth pipeline, and the flue gas at the outlet of the blower drying section is discharged after dust removal.

[0020] A drying fan is installed on the fifth pipeline.

[0021] As can be seen from the above technical solution, the apparatus for producing pellets using low-calorific-value fuel gas provided by the present invention introduces hot air from the homogenization section into the first air box at the air inlet of the cooling section. Inside the first air box, the hot air flowing into the homogenization section mixes with the air flowing into the first air box from the cooling pipes. The cooling section is cooled by hot air after mixing the exhaust gas from the homogenization section with ambient temperature air, thus increasing the temperature of the flue gas discharged from the cooling section. Dividing the cooling section into three segments reduces the amount of cooling air entering the cooling section, thereby reducing the amount of air that needs to be heated and further increasing the temperature of the flue gas in the cooling section. Compared to the prior art that directly uses ambient temperature air for cooling, the cooling section of the apparatus for producing pellets using low-calorific-value fuel gas of the present invention uses high-temperature cooling, increasing the air temperature of the cooling section from 800℃~950℃ in the prior art to 950℃~1150℃. This reduces the amount of heat required to meet the temperature of the roasting section, thus allowing the use of low-calorific-value fuel gas to meet the requirements. Setting the air-fuel ratio of the first low-calorific-value fuel burner to 4-7 is sufficient.

[0022] The present invention also provides a method for producing pellets using low-calorific-value fuel gas, applied to the above-mentioned apparatus for producing pellets using low-calorific-value fuel gas. The method utilizes the waste gas from the homogenization section to mix with a set amount of ambient air to cool the cooling section with hot air, controlling the temperature of the hot flue gas in the cooling section to 950-1150°C. The hot flue gas in the cooling section provides the high-temperature air required for combustion for the first low-calorific-value fuel burner.

[0023] The amount of hot flue gas and low-calorific-value fuel gas entering the cooling section of the first low-calorific-value fuel burner is controlled according to the temperature requirements, so that the air-fuel ratio of the first low-calorific-value fuel burner is 4-7.

[0024] Optionally, the hot exhaust gas generated in the roasting section is used to heat the exhaust drying section and the preheating section, and the hot air from the cooling section is used to heat the preheating section.

[0025] The hot air from the three cooling sections is used to heat and dry the blower drying section.

[0026] Optionally, the air temperature of the exhaust drying section and the preheating section can be controlled by controlling the amount of hot exhaust gas generated in the calcination section entering the exhaust drying section and the preheating section.

[0027] The method of producing pellets using low-calorific-value fuel gas of the present invention is applied to the above-mentioned apparatus for producing pellets using low-calorific-value fuel gas, and therefore has the advantages of the above-mentioned structure, which will not be repeated here. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A schematic diagram of the structure of an apparatus for producing pellets using low-calorific-value fuel gas, provided in an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the structure of the calcination section, the homogenization section, and the cooling section provided in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the structure of the calcination section, the homogenization section, and the cooling section provided in another embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of the structure of the exhaust drying section, preheating section and calcination section provided in an embodiment of the present invention;

[0033] Figure 5 A schematic diagram of an apparatus for producing pellets using low-calorific-value fuel gas, provided in another embodiment of the present invention;

[0034] Figure 6 for Figure 5 The diagram shows the structure of the exhaust drying section, preheating section and calcination section.

[0035] in:

[0036] 1. Blow-air drying section; 2. Exhaust-air drying section; 3. Preheating section; 4. Calcination section; 5. Cooling section 1; 6. Cooling section 2; 7. Cooling section 3; 8. Third air box; 9. Second air box; 10. First air box; 11. First pipeline; 12. Heat equalization section; 13. Cooling pipeline; 14. Second regeneration branch pipe; 15. First regeneration branch pipe; 16. Regeneration pipeline; 17. Secondary air main pipe; 18. Second pipeline; 19. Fifth pipeline; 20. Regeneration fan; 21. Main exhaust fan; 22. Third pipeline; 23. Blow-air drying fan; 24. Fabric distribution device; 25. Chimney; 26. Second valve; 27. Fourth pipeline; 28. First valve; 29. ​​Cooling fan. Detailed Implementation

[0037] This invention discloses an apparatus for producing pellets using low-calorific-value fuel gas. By employing hot air cooling and reducing the air-fuel ratio, high-temperature roasting and solidification of pellets can be achieved using low-calorific-value fuel, thereby reducing the processing cost of pellets.

[0038] The present invention also discloses a method for producing pellets using low-calorific-value fuel gas.

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] See Figures 1 to 6 The apparatus for producing pellets using low-calorific-value fuel gas of the present invention includes a forced-air drying section 1, a forced-air drying section 2, a preheating section 3, a roasting section 4, a homogenizing section 12, and a cooling section arranged sequentially along the conveying direction. The cooling section is further divided into a first cooling section 5, a second cooling section 6, and a third cooling section 7 arranged sequentially. The first cooling section 5 is located close to the homogenizing section 12. The exhaust gas from the homogenizing section 12 is connected to the first air box 10 of the first cooling section 5 through a first pipeline 11. The first air box 10 is connected to a cooling pipeline 13, which supplies a set amount of ambient temperature air to the first cooling section 5. The hot air from the first cooling section 5 flows to the roasting section 4 and the homogenizing section 12. The roasting section 4 is equipped with a first low-calorific-value fuel burner. The hot flue gas from the first cooling section 5 provides the oxygen required for combustion of the first low-calorific-value fuel burner. The fuel for the first low-calorific-value fuel burner is low-calorific-value fuel gas, and the air-fuel ratio of the first low-calorific-value fuel burner is 4-7.

[0041] The air-fuel ratio refers to the ratio of the actual amount of combustion air to the amount of air required for complete combustion of the fuel gas. The chambers of the forced-air drying section 1, the exhaust drying section 2, the preheating section 3, the roasting section 4, the homogenizing section 12, and the cooling section are separated by partition walls. The total length of the cooling section is the same as that of the cooling section in a conventional belt roaster. The total length of the first cooling section 5 and the second cooling section 6 of this invention is the same as that of the first cooling section in a conventional belt roaster, while the total amount of cooling air supplied to the cooling section by the cooling pipe 13 remains unchanged, thereby reducing the amount of cooling air entering the first air box 10 of the first cooling section 5. The first air box 10 is connected to the air inlet side of the first cooling section 5, the second air box 9 is connected to the air inlet side of the second cooling section 6, and the third air box 8 is connected to the air inlet side of the third cooling section 7. The first air box 10, the second air box 9, and the third air box 8 are all connected to the cooling pipe 13. The feeding device 24 conveys the pellets to the conveying device of the belt roaster. To adjust the flame size of the first low-calorific-value fuel burner, a combustion air inlet is also provided on the first low-calorific-value fuel burner, which is used to supplement a small amount of combustion air. The solid arrows in the figure represent the gas flow direction, and the dashed arrows represent the rotation direction of the conveying device.

[0042] The apparatus for producing pellets using low-calorific-value fuel gas of the present invention introduces hot air from the homogenization section 12 into the first air box 10 at the air inlet of the cooling section 5. Within the first air box 10, the hot air flowing into the homogenization section 12 mixes with the air flowing into the first air box 10 from the cooling pipe 13. The cooling section 5 is cooled by a mixture of exhaust gas from the homogenization section 12 and ambient temperature air, thereby increasing the temperature of the flue gas discharged from the cooling section 5. Dividing the cooling section into three segments reduces the amount of cooling air entering the cooling section 5, thus reducing the amount of air requiring heating and further increasing the temperature of the flue gas in the cooling section 5. Compared to the existing technology that directly uses ambient air for cooling, the cooling stage 5 of the device for producing pellets using low-calorific-value fuel gas in this invention uses high-temperature cooling, raising the air temperature of the cooling stage 5 from 800℃~950℃ in the existing technology to 950℃~1150℃. As a result, the amount of calorific value that needs to be added to meet the temperature of the roasting stage 4 is reduced. Therefore, low-calorific-value fuel gas can be used as fuel to meet the requirements. The air-fuel ratio of the first low-calorific-value fuel burner is set to 4-7 to meet the requirements.

[0043] To supply cooling air to the cooling section, a cooling fan 29 is installed on the cooling pipe 13. The cooling fan 29 supplies ambient temperature cooling air to the cooling section as needed. The air inlet of the second cooling section 6 is connected to the cooling pipe 13 via the second air box 9. The cooling pipe 13 supplies ambient temperature air to the second cooling section 6. The hot air heated by the second cooling section 6 is connected to the end of the preheating section 3 near the calcination section 4 via the second pipe 18. The hot exhaust gas generated in the calcination section 4 is connected to the end of the preheating section 3 near the exhaust drying section 2 via the reheat pipe 16. The flue gas temperature of the second cooling section 6 is between 500 and 850°C. It is introduced into the rear of the preheating section 3, and part of it mixes with the hot exhaust gas generated in the calcination section 4 before being introduced into the front of the preheating section 3. Here, "rear" refers to the area reached after the conveyor belt of the calciner, and "front" refers to the area reached first according to the conveyor belt of the calciner. In order to smoothly transport the hot exhaust gas generated in the roasting section 4 to the preheating section 3, a reheating fan 20 is installed on the reheating pipeline 16.

[0044] In one embodiment, the end of the regenerating pipe 16 away from the calcination section 4 includes a first regenerating branch pipe 15 and a second regenerating branch pipe 14. The first regenerating branch pipe 15 is connected to the preheating section 3, and the second regenerating branch pipe 14 is connected to the exhaust drying section 2. This allows a portion of the hot exhaust gas generated in the calcination section 4 to flow through the first regenerating branch pipe 15 into the inner cavity of the preheating section 3, while the other portion of the exhaust gas flows through the second regenerating branch pipe 14 into the inner cavity of the exhaust drying section 2, serving as the medium for exhaust drying of the pellets in the exhaust drying section 2.

[0045] To prevent air pollution from exhaust gases, the exhaust gases from the exhaust drying section 2 and the preheating section 3 are collected in the fourth air box and then connected to the desulfurization and denitrification equipment and the dust removal equipment through the third pipeline 22. The exhaust gases from the third pipeline 22 are discharged after being treated by the desulfurization and denitrification equipment. It is understood that the desulfurization and denitrification equipment and the dust removal equipment are installed inside the chimney 25. To facilitate the discharge of exhaust gases from the exhaust drying section 2 and the preheating section 3, a main exhaust fan 21 is installed on the third pipeline 22.

[0046] The exhaust gas ends of the exhaust drying section 2 and the preheating section 3 are equipped with fourth air boxes, and the exhaust gas from both is discharged into the fourth air box. A third pipe 22 is connected to the fourth air box. To control the air temperature of the exhaust drying section 2 and the preheating section 3 within a reasonable range, the fourth air box is connected to the fifth air box at the exhaust gas end of the calcination section 4 via a fourth pipe 27. A first valve 28 is installed on the fourth pipe 27. By controlling the opening of the first valve 28, the amount of hot flue gas entering the fourth air box through the fourth pipe 27 is controlled. Figure 5 and Figure 6 As shown.

[0047] To increase the temperature at the rear of the preheating section 3, a second low-calorific-value fuel burner is installed at one end of the preheating section 3 near the calcination section 4. The hot air of the cooling section 6 is connected to the air inlet of the second low-calorific-value fuel burner. This hot air provides the oxygen needed for combustion in the second low-calorific-value fuel burner, reducing the need for a wider temperature range. Low-calorific-value fuel gas is sufficient to meet the temperature requirements. The fuel used in the second low-calorific-value fuel burner is low-calorific-value fuel gas. By using the second low-calorific-value fuel burner to burn low-calorific-value fuel gas, the temperature at the rear of the preheating section 3 is increased.

[0048] Furthermore, the outlet of the cooling section 7 is connected to the inlet of the drying section 1 via the fifth pipe 19. The flue gas at the outlet of the drying section 1 is discharged after being cleaned by the dust removal equipment inside the chimney 25. To ensure that the hot exhaust gas in the cooling section 7 can smoothly enter the drying section 1 to dry the pellets, a drying fan 23 is installed on the fifth pipe 19. The cooling fan 23 blows ambient air into the belt roaster, passing through the material layer from bottom to top to cool the pellets.

[0049] To facilitate adjustment of the cooling air volume entering the first air box 10, a second valve 26 is installed on the pipe connecting the first air box 10 and the cooling pipe 13, such as... Figure 3 As shown.

[0050] The apparatus of this invention for producing iron ore pellets using low-calorific-value fuel gas has a cooling section divided into three sections, each separated by a partition wall. Hot air from the first cooling section 5 flows into the roasting section 4 and the homogenizing section 12 via a secondary air main duct 17 and a downcomer. Hot air from the second cooling section 6 is fed into the preheating section 3, and hot air from the third cooling section 7 is fed into the forced-air drying section 2. The exhaust gas from the roasting section 4 is used as reheat air and fed into the front of the forced-air drying section 2 and the preheating section 3 via a reheat fan 20. The first cooling section 5 is cooled by mixing exhaust gas from the homogenizing section 12 with ambient air, raising the flue gas temperature of the first cooling section 5 to 950–1150°C, while simultaneously controlling the amount of ambient air to maintain an air-fuel ratio between 4 and 7. The hot flue gas temperature of the second cooling section 6 is between 500 and 850°C.

[0051] The hot air at the front of the preheating section 3 has two sources: the main source is the regenerated air discharged from the regenerated air fan 20, and the second source is a portion of the hot air from the cooling section 6, which adjusts the front zone of the preheating section 3 to form a suitable temperature gradient. The hot air at the rear of the preheating section 3 mainly comes from the cooling section 6, and is supplied by the second low-calorific-value fuel burner according to production needs.

[0052] A connecting hole is provided in the partition wall between the soaking section 12 and the cooling section 5, allowing the soaking section 12 and the cooling section 5 to be connected. The hot air for both the roasting section 4 and the soaking section 12 originates from the cooling section 5. After entering the secondary air main duct 17, the hot air enters the roasting section 4 through a downcomer. The downcomers are symmetrically distributed on both sides of the secondary air main duct 17, and the first low-calorific-value fuel burner is mounted on the downcomer. The hot exhaust gas from the soaking section 12 is re-blown into the cooling section 5 for hot air cooling. The cold air for the cooling section 5, the cooling section 6, and the cooling section 7 all originates from ambient air blown in by the cooling fan 29.

[0053] In one embodiment, the low-calorific-value fuel gas is converter gas. The cooling section 5 is cooled by hot air after the hot exhaust gas from the homogenizing section 12 is mixed with ambient air, raising the flue gas temperature of the cooling section to 1050°C. The flue gas volume is calculated and controlled according to the composition of the converter gas to achieve an air-fuel ratio of 5. Under these operating conditions, the flue gas temperature of the roasting section 4 can reach 1250°C, meeting the requirements for magnetite production.

[0054] The apparatus of the present invention for producing pellets using low-calorific-value fuel gas enables production using low-calorific-value fuel by employing hot air cooling and reducing the air-fuel ratio, while further reducing process energy consumption.

[0055] This invention also provides a method for producing pellets using low-calorific-value fuel gas, applied to the aforementioned apparatus for producing pellets using low-calorific-value fuel gas. The method utilizes hot exhaust gas from the homogenizing section 12 mixed with a predetermined amount of ambient air to cool the cooling section 5 with hot air, controlling the temperature of the hot flue gas in the cooling section 5 to 950-1150°C. This hot flue gas from the cooling section 5 provides the high-temperature air required for combustion in the first low-calorific-value fuel burner. The amounts of hot flue gas and low-calorific-value fuel gas entering the first low-calorific-value fuel burner are controlled according to temperature requirements, ensuring the air-fuel ratio of the first low-calorific-value fuel burner is 4-7. Based on the required process temperature, the amounts of hot flue gas and low-calorific-value fuel gas entering the first low-calorific-value fuel burner are finely adjusted via valve control, maintaining the air-fuel ratio of the first low-calorific-value fuel burner at 4-7.

[0056] To fully utilize the heat generated during the production process, the hot exhaust gas from the roasting section 4 heats the exhaust drying section 2 and the preheating section 3. Hot air from the second cooling section 6 heats the preheating section 3, and hot air from the third cooling section 7 heats and dries the forced-air drying section 1. To meet the heat demands of the exhaust drying section 2 and the preheating section 3, the amount of hot exhaust gas from the roasting section 4 entering these sections is controlled, thereby controlling the air temperature of the exhaust drying section 2 and the preheating section 3.

[0057] This invention also provides a method for producing iron ore pellets using low-calorific-value fuel gas. The hot exhaust gas from the homogenization section 12 flows into the cooling section 5 for hot air cooling, raising the flue gas temperature in the cooling section 5 to 950–1150°C. Simultaneously, the existing cooling section is subdivided into three sections, compared to the existing two-section division. Since the total length of the cooling section remains the same, the length of the cooling section 5 is shorter than that of the existing cooling section, thus reducing the amount of air entering the cooling section 5 and decreasing the amount of air requiring heating. Because the flue gas temperature in the cooling section 5 has already been overheated by the hot exhaust gas from the homogenization section 12, the temperature of the flue gas exiting the cooling section 5 is increased, bringing the temperature of the hot flue gas exiting the cooling section 5 closer to the required temperature of the roasting section 4. In other words, to reach the required temperature (1250°C) of the roasting section 4, the required temperature increase is reduced, and the demand can be met using low-calorific-value fuel. The air-fuel ratio is reduced from 8-12 to 4-7, which meets the requirements for the application of low-calorific-value fuels such as converter gas in the pelletizing process of belt roasters. The second cooling section 6 generates hot air at 500-850°C, which is then directed to the preheating section 3. While achieving the appropriate temperature, low-calorific-value fuels can be used for heating. The exhaust drying section 2 and the preheating section 3 achieve ideal temperatures through a mixture of main exhaust hot air and reheat air. Simultaneously, the circulation of main exhaust hot air and reheat air reduces the volume and oxygen content of the discharged flue gas, thus lowering the pollutant emission load.

[0058] In the description of this solution, it should be understood that the terms "upper", "lower", "vertical", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this solution.

[0059] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this solution, "multiple" means two or more, unless otherwise explicitly specified.

[0060] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0061] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those 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 invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An apparatus for producing iron ore pellets using low-calorific-value fuel gas, comprising a forced-air drying section, a forced-air drying section, a preheating section, a roasting section, a homogenizing section, and a cooling section arranged sequentially and spaced apart, characterized in that, The cooling section is divided into three sequentially arranged cooling sections: a first cooling section, a second cooling section, and a third cooling section. The first cooling section is located close to the heat exchange section. The exhaust gas from the heat exchange section is connected to the first air box of the first cooling section via a first pipeline. The first air box is connected to the cooling pipeline, which is used to supply a set amount of ambient temperature air to the first cooling section. The hot air from the first cooling section flows to the calcination section and the heat exchange section. The calcination section is equipped with a first low-calorific-value fuel burner. The hot flue gas from the first cooling section provides the first low-calorific-value fuel burner with the oxygen required for combustion. The fuel for the first low-calorific-value fuel burner is low-calorific-value gas. The first low-calorific-value fuel burner is also equipped with a combustion air inlet, which is used to supplement combustion air. The air-fuel ratio of the first low-calorific-value fuel burner is 4-7. The first air box is connected to the air inlet side of the first cooling section, the air inlet side of the second cooling section is connected to the second air box, and the air inlet side of the third cooling section is connected to the third air box. The first air box, the second air box, and the third air box are all connected to the cooling pipeline. A cooling fan is installed on the cooling pipeline.

2. The apparatus for producing pellets using low-calorific-value fuel gas according to claim 1, characterized in that, The cooling pipe is used to supply ambient temperature air to the second cooling section, and the hot air heated by the second cooling section is connected to the end of the preheating section near the calcination section through the second pipe; The hot exhaust gas generated in the roasting section is connected to one end of the preheating section near the exhaust drying section through a reheating pipeline. A regenerative fan is installed on the regenerative pipeline.

3. The apparatus for producing pellets using low-calorific-value fuel gas according to claim 2, characterized in that, The end of the regenerating pipeline away from the calcination section includes a first regenerating branch pipe and a second regenerating branch pipe. The first regenerating branch pipe is connected to the preheating section, and the second regenerating branch pipe is connected to the exhaust drying section.

4. The apparatus for producing pellets using low-calorific-value fuel gas according to claim 3, characterized in that, The exhaust gas from the exhaust drying section and the preheating section is connected to the desulfurization and denitrification equipment through a third pipeline. The exhaust gas from the third pipeline is discharged after being treated by the desulfurization and denitrification equipment. The third pipeline is equipped with a main exhaust fan.

5. The apparatus for producing pellets using low-calorific-value fuel gas according to claim 4, characterized in that, The exhaust drying section and the preheating section are equipped with a fourth air box at their exhaust gas ends. The exhaust gas from both sections is discharged into the fourth air box. The third pipeline is connected to the fourth air box. The fourth air box is connected to the fifth air box at the exhaust end of the roasting section via a fourth pipeline, and a first valve is installed on the fourth pipeline.

6. The apparatus for producing pellets using low-calorific-value fuel gas according to claim 2, characterized in that, A second low-calorific-value fuel burner is provided at one end of the preheating section near the roasting section; The hot air in the second cooling section provides the oxygen required for combustion to the second low-calorific-value fuel burner, which uses low-calorific-value fuel gas as fuel.

7. The apparatus for producing pellets using low-calorific-value fuel gas according to claim 1, characterized in that, The air outlet of the three cooling sections is connected to the air inlet of the blower drying section through the fifth pipeline, and the flue gas at the outlet of the blower drying section is discharged after dust removal. A drying fan is installed on the fifth pipeline.

8. A method for producing iron ore pellets using low-calorific-value fuel gas, applied to the apparatus for producing iron ore pellets using low-calorific-value fuel gas as described in any one of claims 1-7, characterized in that, The exhaust gas from the heat equalization section is mixed with a set amount of ambient air to cool the cooling section with hot air, and the temperature of the hot flue gas in the cooling section is controlled to 950-1150°C. The hot flue gas in the cooling section provides the high-temperature air required for combustion of the first low-calorific-value fuel burner. The amount of hot flue gas and low-calorific-value fuel gas entering the cooling section of the first low-calorific-value fuel burner is controlled according to the temperature requirements, so that the air-fuel ratio of the first low-calorific-value fuel burner is 4-7.

9. The method for producing pellets using low-calorific-value fuel gas according to claim 8, characterized in that, The hot exhaust gas generated in the roasting section is used to heat the exhaust drying section and the preheating section, and the hot air from the cooling section is used to heat the preheating section. The hot air from the three cooling sections is used to heat and dry the blower drying section.

10. The method for producing pellets using low-calorific-value fuel gas according to claim 8, characterized in that, The air temperature of the exhaust drying section and the preheating section is controlled by controlling the amount of hot exhaust gas generated in the calcination section that enters the exhaust drying section and the preheating section.

Images