Hot exhaust gas recirculation system for the blower drying section based on the chain-loop production process

Abstract

This invention provides a hot waste gas recycling system for the blower drying section based on a chain-recycle-loop production process, relating to the field of iron ore pellet production technology in the steel industry. The system includes: waste gas generated in the blower drying section is introduced into a wet dust collector in the pelletizing chamber via a hot air duct. A cold air valve I is installed on the hot air duct, adjusting the waste gas temperature in the duct to 105℃-130℃. The outlet of the wet dust collector is connected to a gravity dehydrator via a pipe. The waste gas treated by the gravity dehydrator is supplied to cooling stages one, three, and four via a gas supply system. This system achieves the recycling and utilization of hot waste gas and waste heat from the blower drying section, which has practical significance for energy saving and emission reduction in pellet production.

Description

Technical Field

[0001] This invention relates to the field of pellet production technology in the steel industry, specifically to a hot waste gas circulation system for the blower drying section based on a chain-loop production process. Background Technology

[0002] Currently, the "chain grate-rotary kiln-annular cooler" pellet production process is one of the main production processes for iron ore pellets. In actual production, the chain grate is divided into four sections along the material flow direction: blower drying section, exhaust drying section, preheating section one, and preheating section two; the annular cooler is divided into four sections along the material flow direction: cooling section one, cooling section two, cooling section three, and cooling section four.

[0003] The traditional hot air process is as follows:

[0004] 1. High-temperature exhaust gas (approximately 1000℃) in the cooling stage: sourced from ambient ambient air;

[0005] A. The hot air enters the rotary kiln through the hot air duct and kiln head hood as primary air to increase the firing temperature inside the kiln;

[0006] B. The raw pellets are preheated from top to bottom in the second preheating stage of the chain grate machine through the kiln tail hood.

[0007] C. The green balls are dried from top to bottom in the exhaust drying section of the chain grate machine through a multi-tube dust collector and a regenerating air fan;

[0008] D. Finally, it is discharged into the atmosphere through the main electrostatic precipitator, main exhaust fan, and desulfurization and denitrification system.

[0009] 2. Cooling stage two hot exhaust gas (approximately 600℃): Sourced from cooling stage four hot exhaust gas;

[0010] A. The hot air enters the preheating section of the chain grate machine through the hot air duct to preheat the green balls from top to bottom;

[0011] B. It is discharged into the air through the main electrostatic precipitator, main exhaust fan, and desulfurization and denitrification system.

[0012] 3. Cooling the three-stage hot exhaust gas (approximately 250℃): sourced from ambient ambient air;

[0013] A. The green balls are dried from bottom to top in the drying section of the chain grate machine by passing through hot air ducts and a blower.

[0014] B. Finally, the air is discharged through the furnace hood dust collector and furnace hood fan.

[0015] 4. Cooling the four stages of hot exhaust gas (approximately 80℃): sourced from ambient ambient air;

[0016] A. The hot air enters the second cooling stage through a hot air duct to cool the high-temperature pellets.

[0017] According to the hot air flow process described above, the existing "chain grate-rotary kiln-annular cooler" pelletizing process involves returning the hot waste gas displaced by the annular cooler to each section of the rotary kiln and chain grate through hot air ducts for reuse, and finally discharging the waste gas through a dust collector and desulfurization / denitrification system. In the existing process, the hot waste gas flows in a unidirectional direction, making it impossible to achieve flue gas recycling. The hot waste gas from the blast drying section has a certain temperature; directly discharging it into the atmosphere is wasteful and also has a negative impact on environmental protection. Therefore, the rational recycling and utilization of the hot waste gas from the blast drying section is of great significance. Summary of the Invention

[0018] Technical problems to be solved

[0019] To address the shortcomings of existing technologies, this invention provides a hot waste gas circulation system for the blower drying section based on a chain-recycle-loop production process. This system enables the recycling of hot waste gas from the blower drying section in the existing "chain grate-rotary kiln-ring cooler" production process, thereby reducing the emission of waste gas into the environment during production and enabling the secondary utilization of heat from the hot waste gas in the blower drying section.

[0020] Technical solution

[0021] To achieve the above objectives, the present invention is implemented through the following technical solution: a hot waste gas circulation system for the blower drying section based on the chain-return-loop production process, including a chain grate machine, a ring cooler, and a wet scrubber for treating the waste gas inside the pelletizing chamber. The chain grate machine has a blower drying section, an exhaust drying section, a preheating section 1, and a preheating section 2. The ring cooler has a cooling section 1, a cooling section 2, a cooling section 3, and a cooling section 4. The waste gas generated in the blower drying section is introduced into the wet scrubber through a hot air duct, and a cold air valve I is installed on the hot air duct. The cold air valve I adjusts the waste gas in the hot air duct to 105℃-130℃. The outlet of the wet scrubber is connected to a gravity dewatering device through a pipe. The waste gas treated by the gravity dewatering device is supplied to the cooling sections 1, 3, and 4 through an air supply system.

[0022] Preferably, a cooling air valve II is installed between the wet dust collector and the gravity dewatering device.

[0023] The gas supply system includes: a main gas path, a first-ring cold return duct and a second-ring cold return duct branching from the outlet of the main gas path, and a first-branch gas path and a second-branch gas path branching from the outlet of the second-ring cold return duct. The inlet end of the main gas path is connected to the outlet end of the gravity water separator, and a dust removal fan is installed on the main gas path. A pipeline regulating valve I and a cooling stage 1 fan are installed on the first-ring cold return duct, and the outlet end of the cooling stage 1 fan supplies cooling stage 1. A pipeline regulating valve II and a cooling air exchange valve III are installed on the second-ring cold return duct. A cooling stage 3 fan is installed on the first-branch gas path, and the outlet end of the cooling stage 3 fan supplies cooling stage 3. A cooling stage 4 fan is installed on the second-branch gas path, and the outlet end of the cooling stage 4 fan supplies cooling stage 4.

[0024] Preferably, the first annular return air duct is provided with an insulation layer.

[0025] Preferably, the pipeline regulating valve II is located behind the cooling air valve III.

[0026] Preferably, the dust removal exhaust gas inside the pelletizing chamber and the hot exhaust gas from the chain grate drying section are mixed in the hot air duct before entering the wet dust collector.

[0027] Preferably, temperature monitoring modules are installed at both the air inlet and air outlet of the wet dust collector.

[0028] Preferably, the temperature of the exhaust gas treated by the wet scrubber is below 100°C.

[0029] Preferably, the gas source for the second cooling stage is the hot exhaust gas from the fourth cooling stage.

[0030] Beneficial effects

[0031] This invention provides a hot waste gas recirculation system for the blower drying section based on a chain-loop production process. It offers the following advantages:

[0032] 1. This invention utilizes hot air ducts to introduce the waste gas generated in the blower drying section into a wet scrubber in the pelletizing chamber for treatment along with the waste gas inside the pelletizing chamber. The gas treated by the wet scrubber is then introduced into a gravity dehydrator for water removal. Finally, the gas is supplied to the first, third, and fourth cooling sections via a gas supply system. This process has at least the following advantages: 1) It forms a circulating waste gas treatment system, reducing the discharge of dust-laden waste gas from the pelletizing chamber and hot waste gas from the blower drying section of the chain grate machine, thus reducing air pollution during the chain-recycle-loop production process; 2) The wet scrubber in the pelletizing chamber effectively removes dust from the blower drying section and heat from the chain grate machine, reducing air pollution during the chain-recycle-loop production process; When treating the hot waste gas generated in the air drying section, the internal circulating water absorbs heat from the waste gas, thus heating the circulating water itself. In northern winters, as temperatures drop, this better ensures the smooth operation of the wet dust removal system in the pelletizing chamber during winter operation, realizing the utilization of waste heat from the hot waste gas in the air drying section. 3) The treated hot waste gas from the air drying section is then returned to the ring cooler for further cooling, replacing the original ambient air. This increases the outlet air temperature of the ring cooler, indirectly providing more heat to the rotary kiln and saving fuel consumption in the main burner of the rotary kiln. In summary, this process flow has practical significance for energy saving and emission reduction in pellet production.

[0033] 2. The present invention, by employing a flue gas recirculation treatment system consisting of a wet dust collector and a gravity dewatering device, eliminates the need to consider the condensation problem caused by the decrease in temperature of the hot exhaust gas compared to the currently used dry dust collector, thereby increasing the reliability of equipment operation. Attached Figure Description

[0034] Figure 1 This is a process flow diagram of the hot waste gas circulation system of the blower drying section based on the chain-loop production process proposed in this invention.

[0035] The components include: 1. Chain grate machine; 2. Circular cooler; 3. Hot air duct; 4. Cooling air valve I; 5. Wet dust collector; 6. Cooling air valve II; 7. Gravity water separator; 8. Dust collector fan; 9. First ring cooler return duct; 10. Second ring cooler return duct; 11. Pipeline regulating valve I; 12. Pipeline regulating valve II; 13. Cooling air valve III; 14. Cooling stage 1 fan; 15. Cooling stage 3 fan; 16. Cooling stage 4 fan. Detailed Implementation

[0036] 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.

[0037] Example 1:

[0038] like Figure 1 As shown, this embodiment of the invention provides a hot waste gas circulation system for the blower drying section based on a chain-return-loop production process, including a chain grate 1, an annular cooler 2, and a wet dust collector 5 for treating the waste gas inside the pelletizing chamber. The chain grate 1 has a blower drying section, an exhaust drying section, a preheating section 1, and a preheating section 2. The annular cooler 2 has a cooling section 1, a cooling section 2, a cooling section 3, and a cooling section 4. A rotary kiln is set between the chain grate 1 and the annular cooler 2, forming a "chain grate-rotary kiln-annular cooler" production system. The pelletizing chamber is used for the "pelletizing" process and is the front-end pelletizing process equipment of the "chain grate-rotary kiln-annular cooler" production system. All of these are processes in the production of iron ore pellets.

[0039] The exhaust gas generated in the blower drying section is introduced into the wet scrubber 5 through the hot air duct 3. A cold air valve I 4 is installed on the hot air duct 3. The cold air valve I 4 controls the external air intake. The external natural airflow mixes with the hot exhaust gas inside the hot air duct 3 to adjust the exhaust gas temperature. The cold air valve I 4 adjusts the exhaust gas temperature in the hot air duct 3 to the range of 105℃-130℃. It is necessary to ensure that the exhaust gas temperature is below 100℃ after passing through the wet scrubber 5 as much as possible. The outlet of the wet scrubber 5 is connected to a gravity dewatering device 7 through a pipe. The exhaust gas treated by the gravity dewatering device 7 is supplied to the cooling stages 1, 3, and 4 through the air supply system.

[0040] After the hot exhaust gas from the chain grate drying section is generated on the chain grate 1, it passes through the hood of the chain grate drying section and then through the hot air duct 3 to the wet scrubber 5. Before entering the wet scrubber 5 from the end of the hot air duct 3, a cooling air valve I 4 is installed to adjust the gas temperature within the range of 105℃-130℃. The wet scrubber 5 removes dust from the hot exhaust gas. The hot exhaust gas exchanges heat with the circulating water in the wet scrubber, lowering the gas temperature to below 100℃, causing water vapor to begin converting into liquid water. Before entering the gravity dewatering unit 7, a cooling air valve II is installed. 6. Further reduce the temperature of the hot exhaust gas after wet dust removal to ensure the working effect of gravity water separator 7; the hot exhaust gas after passing through the dust removal and water removal system will be supplied by the air supply system to the first cooling stage, the third cooling stage, and the fourth cooling stage according to the usage requirements.

[0041] In one embodiment, the gas supply system includes: a main gas path, a first ring cold return duct 9 and a second ring cold return duct 10 branching from the outlet of the main gas path, a first branch gas path and a second branch gas path branching from the outlet of the second ring cold return duct 10, the inlet end of the main gas path being connected to the outlet end of the gravity water separator 7, and a dust removal fan 8 installed on the main gas path, the dust removal fan 8 being used to provide power to the gas in the main gas path, a pipeline regulating valve I 11 and a cooling section fan 14 installed on the first ring cold return duct 9, the outlet end of the cooling section fan 14 supplying cooling section 1, a pipeline regulating valve II 12 and a cooling air valve III 13 installed on the second ring cold return duct 10, a cooling section fan 15 installed on the first branch gas path, the outlet end of the cooling section fan 15 supplying cooling section 3, and a cooling section fan 16 installed on the second branch gas path, the outlet end of the cooling section fan 16 supplying cooling section 4.

[0042] The first ring cold return air duct 9 is equipped with an insulation layer to keep the gas inside the first ring cold return air duct 9 warm, so that the air temperature entering the cooling section is suitable and no additional heating is required, thereby improving energy utilization. The second ring cold return air duct 10 does not need to be equipped with an insulation layer. The pipeline regulating valve II 12 is located behind the cooling air valve III 13. The pipeline regulating valve II 12 is used to control the gas flow rate, and the cooling air valve III 13 is used to adjust the exhaust gas temperature in the pipeline to meet the cooling air temperature requirements of the cooling section three and the cooling section four.

[0043] In one embodiment, the waste gas inside the pelletizing chamber and the waste gas inside the hot air duct 3 are mixed and then enter the cold air valve I4. The outlet of the cold air valve I4 is connected to the inlet of the wet dust collector 5. This method can also utilize the waste gas generated in the pelletizing chamber at the same time, which can also reduce the discharge of waste gas and is conducive to comprehensive environmental protection requirements.

[0044] In one embodiment, temperature monitoring modules are installed at both the inlet and outlet of the wet dust collector 5 to monitor the temperature of the air flowing through it, so as to make adjustments to the cooling air valve II 6 and cooling air valve III 13 according to the actual situation.

[0045] In one embodiment, the gas source for the second cooling stage is the hot exhaust gas from the fourth cooling stage, which is beneficial to achieve a full supply of gas inside the annular cooler 2 and realize the circulation of gas.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A hot exhaust gas recirculation system for the blower drying section based on a chain-recycle-loop production process, comprising a chain grate machine, a ring cooler, and a wet dust collector for treating exhaust gas inside the pelletizing chamber, wherein the chain grate machine has a blower drying section, an exhaust drying section, a preheating section 1, and a preheating section 2, and the ring cooler has a cooling section 1, a cooling section 2, a cooling section 3, and a cooling section 4, characterized in that: The exhaust gas generated in the blower drying section is introduced into the wet dust collector through a hot air duct. A cold air valve I is installed on the hot air duct, which adjusts the exhaust gas in the hot air duct to 105℃-130℃. The outlet of the wet dust collector is connected to a gravity dewatering device through a pipe. The exhaust gas treated by the gravity dewatering device is supplied to the first cooling section, the third cooling section, and the fourth cooling section through the air supply system. A cooling air valve II is installed between the wet dust collector and the gravity water separator. The gas supply system includes: a main gas path, a first ring cold return duct and a second ring cold return duct branching from the outlet of the main gas path, a first branch gas path and a second branch gas path branching from the outlet of the second ring cold return duct, the inlet end of the main gas path being connected to the outlet end of the gravity water separator, and a dust removal fan being installed on the main gas path, a pipeline regulating valve I and a cooling stage 1 fan being installed on the first ring cold return duct, the outlet end of the cooling stage 1 fan supplying cooling stage 1, a pipeline regulating valve II and a cooling air exchange valve III being installed on the second ring cold return duct, a cooling stage 3 fan being installed on the first branch gas path, the outlet end of the cooling stage 3 fan supplying cooling stage 3, and a cooling stage 4 fan being installed on the second branch gas path, the outlet end of the cooling stage 4 fan supplying cooling stage 4. The first ring cold return duct is equipped with an insulation layer; the second ring cold return duct is not equipped with an insulation layer.

2. The hot waste gas circulation system for the blower drying section based on the chain-loop production process according to claim 1, characterized in that: The pipeline regulating valve II is located behind the cooling air valve III.

3. The hot waste gas circulation system for the blower drying section based on the chain-loop production process according to claim 1, characterized in that: The dust-collecting exhaust gas inside the pelletizing chamber and the hot exhaust gas from the chain grate drying section are mixed inside the hot air duct before entering the wet dust collector.

4. The hot waste gas circulation system for the blower drying section based on the chain-loop production process according to claim 1, characterized in that: Temperature monitoring modules are installed at both the inlet and outlet of the wet dust collector.

5. The hot waste gas circulation system for the blower drying section based on the chain-loop production process according to claim 1, characterized in that: The temperature of the exhaust gas treated by the wet scrubber is below 100℃.

6. The hot waste gas circulation system for the blower drying section based on the chain-loop production process according to claim 1, characterized in that: The gas source for the second cooling stage of the annular cooler is the hot exhaust gas from the fourth cooling stage.

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