Flue gas closed cycle sintering system and method

Abstract

The invention belongs to the field of iron and steel smelting, and particularly discloses a sintering system and method for flue gas closed cycle. According to the system, an ignition heat preservation furnace and a flue gas cover are sequentially arranged above a sintering machine, an air bellow is arranged below the sintering machine, flue gas generated by sintering can be fed into a high-temperature section of a circular cooler through the air bellow and an exhaust fan to exchange heat with high-temperature materials, and waste gas obtained after heat exchange is conveyed back to the ignition heat preservation furnace and / or the flue gas cover for waste heat utilization. And meanwhile, cold air is introduced into the low-temperature section of the circular cooler through an air blower for heat exchange and then introduced into the medium-temperature section for heat exchange, and finally waste gas of the medium-temperature section is conveyed to an ignition heat preservation furnace and / or a smoke hood for waste heat utilization. Furthermore, the waste gas for waste heat utilization can be introduced into different sintering positions according to the temperature gradient, so that the waste heat utilization is more efficient. According to the system and the method, the utilization rate of the waste heat of the sintering flue gas can be greatly increased, pollution caused by direct exhaust of the flue gas is reduced, and the system and the method have extremely high industrial application value.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, specifically to a sintering system and method with closed-loop flue gas circulation. Background Technology

[0002] As an indispensable pillar industry of the nation, the steel industry is directly related to the foundation of the national economy, national defense security, and modernization. At the same time, it is also a major area of ​​energy consumption and carbon emissions, accounting for approximately 15% of the nation's energy consumption. Analyzing the steel industry's technological process, sintering, as a major energy-consuming process, has significant disadvantages such as high energy consumption, high pollution, and low waste heat utilization. The sintering process, from raw material intake to finished sinter output, includes fuel receiving, fuel crushing, iron-containing material receiving, batching, mixing, granulation, sintering, cooling, screening and granulation, finished product sampling, and finished product output. Sintering refers to the sintering of the mixture on a sintering machine under the negative pressure of the main exhaust fan after ignition.

[0003] The existing sintering system's process flow is mainly as follows: The sintering raw materials are placed into the sintering machine, ignited, and then sintered under the negative pressure of the main exhaust fan. Cold air above the sintering machine is drawn into the material to participate in the sintering chemical reaction. The sintered material is then cooled by an annular cooler to obtain sintered ore. The high-temperature exhaust gas from the annular cooler is used for high-temperature power generation and then discharged externally. The medium-temperature and low-temperature exhaust gases from the annular cooler are discharged directly. The flue gas generated during sintering is purified by dust removal before being discharged.

[0004] Against the backdrop of increasingly stringent carbon emission and energy conservation requirements, the existing sintering main system suffers from the following problems: First, significant pollution from exhaust gas emissions. The existing sintering system has three main exhaust gas emission points: hot exhaust gas purified by the main exhaust fan, exhaust gas from high-temperature power generation, and cooling exhaust gas from the low-temperature section of the annular cooler, all of which are emitted independently, resulting in a cumulative environmental burden. Second, low waste heat utilization rate. The flue gas from the main chimney (waste heat 120-180℃) is directly emitted, resulting in waste heat. The exhaust gas from the high-temperature section of the annular cooler (waste heat 120-180℃) is also directly emitted, resulting in waste heat. Furthermore, heat energy from the low-temperature section (<200℃) of the annular cooler is not recovered. Therefore, the overall waste heat utilization rate is less than 50%. Third, the system suffers from energy redundancy. The pressure potential energy of the flue gas entering the main chimney is not utilized, thus requiring an additional blower system (consuming approximately 15%-20% of electricity) when the annular cooler cools the sinter. The cooling air from the annular cooler forces cold air in, resulting in low temperatures of the hot exhaust gas in the high-temperature section and consequently low high-temperature power generation efficiency. Fourth, there is redundant equipment configuration. Multiple blowers are needed for flue gas purification, annular cooling, and blower systems, leading to high equipment investment and maintenance costs. Furthermore, due to the limited amount of available hot gas for sintering, the fuel ratio must be increased, further increasing flue gas emissions, polluting the environment and wasting resources. Therefore, this invention proposes a closed-loop flue gas recirculation sintering system and method to solve the above problems. Summary of the Invention

[0005] The main objective of this invention is to provide a sintering system and method with closed-loop flue gas circulation, in order to solve the problems of large exhaust gas discharge, low waste heat utilization rate, serious environmental pollution and energy waste caused by existing sintering systems.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0007] A closed-loop flue gas recirculation sintering system includes a sintering machine, an ignition and holding furnace, a flue gas hood, wind boxes, a first flue, a first exhaust fan, a first dust removal and purification device, an annular cooler, and a blower. The sintering machine has an ignition section and a sintering section arranged sequentially along the trolley's running direction. The ignition and holding furnace is located above the ignition section. The flue gas hood covers the sintering section. A plurality of wind boxes are arranged at equal intervals below the ignition section and the sintering section. The outlet of each wind box is connected to the first flue gas hood. The annular cooler is located downstream of the sintering machine and includes a high-temperature section, a medium-temperature section, and a low-temperature section arranged sequentially along the material running direction. The outlet of the first flue gas hood is connected to the inlet of the high-temperature section. The first exhaust fan and the first dust removal and purification device are both located on the outlet pipe of the first flue gas hood, and the outlet of the high-temperature section is at least connected to the flue gas hood. The blower is located at the air inlet of the low-temperature section, the air outlet of the low-temperature section is connected to the air inlet of the medium-temperature section, and the air outlet of the medium-temperature section is at least connected to the flue hood.

[0008] In the technical solution of this invention, the sintering raw material first enters the sintering machine, and after ignition and sintering, a high-temperature material is obtained. Then, it enters the annular cooler for cooling. An ignition and heat preservation furnace and a flue gas hood are arranged sequentially above the sintering machine, and multiple air boxes are arranged below the sintering machine. The outlet of each air box is connected to the first flue. The negative pressure generated by the first exhaust fan can collect the high-temperature flue gas in the sintering process into the first flue. After dust removal and purification, the flue gas is then introduced into the high-temperature section of the annular cooler. Since the temperature of the flue gas is lower than that of the high-temperature material, the flue gas can exchange heat and cool the high-temperature material. The exhaust gas discharged from the high-temperature section has a higher temperature after heat exchange, so the exhaust gas here can be introduced into the flue gas hood for waste heat utilization, thereby improving the sintering efficiency. Meanwhile, the cold air blown in by the blower serves as the main cooling agent for the high-temperature materials in the annular cooler. A counter-current heat exchange method is used: the cold air is first introduced into the low-temperature section to cool the materials, and then the exhaust gas from the low-temperature section is introduced into the medium-temperature section to cool the materials again. This improves heat exchange efficiency and ensures effective cooling. Finally, the exhaust gas from the medium-temperature section is introduced into the flue gas hood, allowing for waste heat utilization and improving sintering efficiency. In this system, both the flue gas generated during sintering and the exhaust gas from the annular cooler (used as combustion air) are recycled, significantly improving waste heat utilization and reducing energy waste. This also greatly reduces exhaust gas emissions, contributing to environmental protection.

[0009] In this design, the ignition and holding furnace is equipped with an air inlet for supplying external gas and air. The front end of the sintering machine also features a bottom material silo, a mixing silo, and a material spreading device. The spreading device first lays the bottom material on the sintering trolley, and then lays the mixing material on top of the bottom material. After spreading, the sintering raw material enters the ignition section of the sintering machine, where it is ignited by the ignition and holding furnace. The material is then transported to the sintering section for sintering. The tail end of the sintering machine is equipped with a crushing device (such as a single-roll crusher). The high-temperature sintered material is crushed to a suitable size by the crushing device and then enters an annular cooler for cooling. The annular cooler's inlet is located in the high-temperature section, and its outlet is located in the low-temperature section. The material is cooled during its transfer from the high-temperature section to the low-temperature section. After cooling, the material is discharged from the annular cooler outlet, ultimately yielding the finished product. Furthermore, since the ignition and holding furnace also requires a high amount of heat for igniting the fuel layer, the outlets of the high-temperature section and the medium-temperature section can be connected to the ignition and holding furnace to provide waste heat from the ignition stage. Furthermore, the waste gas used for waste heat utilization can be introduced into different sintering positions according to the temperature gradient, thereby making waste heat utilization more efficient.

[0010] Preferably, the flue gas hood includes a first flue gas hood and a second flue gas hood arranged sequentially along the running direction of the sintering trolley. The system also includes a power generation device. The exhaust gas from the high-temperature section outlet is generated by the power generation device and then introduced into the second flue gas hood. The outlet of the medium-temperature section is connected to the ignition and heat preservation furnace and the first flue gas hood, respectively.

[0011] The ignition and holding furnace covers the ignition section, the first flue gas hood covers the front and middle sections of the sintering section, and the second flue gas hood covers the rear section of the sintering section. The ignition section requires igniting the fuel layer for sintering. The front and middle sections of the sintering section are the main reaction zone for the sintering reaction, requiring high temperatures to promote liquid phase formation and mineral particle bonding. The rear section of the sintering section is the sintering completion zone, where the combustion reaction is basically finished, and the main focus is on mineral phase crystallization and structural stabilization, requiring less heat. Since the exhaust gas from the high-temperature section is at a lower temperature after heat exchange with the power generation unit, this portion of the exhaust gas is introduced into the second flue gas hood. The cooling air blown in by the blower, which is the main cooling air for the annular cooler, has a higher temperature after heat exchange with the materials in the low-temperature and medium-temperature sections. Therefore, the exhaust gas from the medium-temperature section is introduced into the ignition and holding furnace and the first flue gas hood, respectively. This arrangement is to direct the exhaust gas to different sintering locations according to the temperature gradient, ensuring that the exhaust gas temperature matches the temperature required for the sintering process, thereby improving waste heat utilization efficiency and sintering effect.

[0012] Since the blower continuously pumps fresh air into the system, to prevent the air volume in the system from exceeding the limit, the power generation unit can discharge some of the waste gas after generating electricity using the waste heat of the exhaust gas, thus ensuring the air volume balance in the system.

[0013] Specifically, the length ratio of the first flue gas hood to the second flue gas hood is typically 2:1 to 3:1, preferably 2.5:1. The power generation unit includes a waste heat boiler and a steam generator set (steam turbine + generator). The power generation principle is as follows: the high-temperature exhaust gas discharged from the high-temperature section exchanges heat with the boiler to generate steam, which then drives the turbine blades to rotate, thereby driving the generator to generate electricity.

[0014] Preferably, a first valve is installed on the pipeline connecting the medium-temperature section outlet to the first flue gas hood, and a second valve is installed on the pipeline connecting the medium-temperature section outlet to the ignition and heat preservation furnace. The first flue gas hood has a plurality of air inlets spaced evenly along its length, and a third valve is installed at each air inlet.

[0015] Specifically, the outlet pipes of the intermediate temperature section are respectively equipped with a first branch pipe and a second branch pipe. The first branch pipe leads to the first flue gas hood, and the second branch pipe leads to the ignition and holding furnace. A first valve is installed on the first branch pipe, and a second valve is installed on the second branch pipe. The first valve and the second valve are used to control the flow rate of the intermediate temperature section exhaust gas leading to the ignition and holding furnace and the first flue gas hood, respectively. At the end of the first branch pipe, there are several secondary branch pipes corresponding one-to-one with the air inlets. A third valve is installed on the secondary branch pipes to control the air intake of each air inlet. Since the required heat decreases as sintering progresses, the opening degree of each third valve usually decreases along the length of the first flue gas hood.

[0016] Preferably, the system further includes a second flue, a second exhaust fan, and a second dust removal and purification device. The outlet of at least a portion of the air box located below the sintering section is simultaneously connected to both the first flue and the second flue. The outlet of the second flue is connected to the air inlet of the high-temperature section, and both the second exhaust fan and the second dust removal and purification device are located on the outlet pipe of the second flue.

[0017] Because the sintering process is relatively long, a large amount of pollutants and harmful gases (such as SO2, NOx, and dioxins) are generated during sintering. If only the first flue is used for collection, it will place a heavy burden on the first exhaust fan and the first dust removal and purification device, which will easily cause insufficient negative pressure in the exhaust, incomplete collection of sintering flue gas, and failure to meet the dust removal and purification standards for sintering flue gas. Therefore, a second flue is set up to assist in the collection of sintering flue gas, and a second exhaust fan and a second dust removal and purification device are provided for exhaust and flue gas dust removal and purification.

[0018] Preferably, a fourth valve is provided on the pipe connecting the first flue and the second flue to the air box, and a fifth valve is provided on the pipe connecting the second flue to the air box.

[0019] Specifically, the outlet pipes of the air box that connects the first flue and the second flue are respectively provided with a third branch pipe and a fourth branch pipe. The third branch pipe leads to the first flue, and the fourth branch pipe leads to the second flue. A fourth valve is installed on the third branch pipe, and a fifth valve is installed on the fourth branch pipe. The fourth valve and the fifth valve are used to control the flow rate of sintering flue gas leading to the first flue and the second flue, respectively.

[0020] Furthermore, the first valve, the second valve, the third valve, the fourth valve, and the fifth valve are all electrically controlled butterfly valves that are matched with flow meters.

[0021] Preferably, the first dust removal and purification device includes a first dust collector and a first purifier. The first dust collector, the first exhaust fan, and the first purifier are arranged sequentially along the flue gas flow direction. The second dust removal and purification device includes a second dust collector and a second purifier. The second dust collector, the second exhaust fan, and the second purifier are arranged sequentially along the flue gas flow direction.

[0022] Specifically, the exhaust fan is positioned after the dust collector and before the purifier. The dust collector (such as a bag filter) is positioned at the front to first remove dust from the flue gas, thus protecting subsequent equipment from dust damage (such as wear and tear on the exhaust fan blades). The exhaust fan is positioned in the middle to provide power for drawing in the flue gas. The purifier (such as a desulfurization and denitrification tower) is positioned at the rear to provide final purification of the flue gas, ensuring the cleanliness of the flue gas leading to the high-temperature section of the annular cooler and preventing material contamination. Moreover, by using the power of the exhaust fan to drive the flow of exhaust gas in the high-temperature section, no additional blower is needed in the high-temperature section, which helps reduce energy consumption.

[0023] Preferably, each of the air boxes located below the ignition and heat preservation furnace and below the first flue gas hood is provided with a first gas detection device, which includes an oxygen detector and a carbon dioxide detector.

[0024] Preferably, the outlet of the high-temperature section is equipped with a second gas detection device, which includes an oxygen detector. Both the outlet of the high-temperature section and the outlet of the medium-temperature section are equipped with pressure sensors.

[0025] The first gas detection device detects the oxygen and carbon dioxide content inside the bellows to determine the degree of ignition and sintering of the material. The second gas detection device monitors the oxygen content at the high-temperature section outlet to determine if the oxygen content in the entire circulation system meets the requirements. A pressure sensor detects whether the pressure in the pipeline meets the requirements.

[0026] Preferably, the system further includes a central controller. The central controller is communicatively connected to the first valve, the second valve, the third valve, the fourth valve, the fifth valve, the first gas detection device, the second gas detection device, the pressure sensor, the first exhaust fan, the second exhaust fan, and the blower.

[0027] The central controller (usually an industrial computer) acts as the control hub of the entire system, regulating the flow and pressure in the system pipelines by controlling the aforementioned devices. The central controller is typically wirelessly connected to these devices (e.g., via an industrial wireless local area network).

[0028] The present invention also provides a sintering method with closed-loop flue gas recirculation, comprising the following steps:

[0029] Step S110: The sintering raw material is fed into the sintering machine for sintering to obtain high-temperature material, and then the high-temperature material is fed into the ring cooler for cooling.

[0030] Specifically, the entire sintering process involves sequential steps such as material preparation, ignition, sintering, crushing, and cooling, ultimately yielding the finished product.

[0031] Step S120: The flue gas generated by sintering is purified by dust removal and then transported to the high-temperature section of the annular cooler. The exhaust gas discharged from the high-temperature section is then transported to the power generation device for power generation. After power generation, the exhaust gas is then transported to the second flue gas hood.

[0032] This step allows the flue gas generated during sintering to be fully utilized after dust removal and purification. Not only is the heat energy of the flue gas used to generate electricity, but the waste heat after power generation is also returned to the sintering process. Compared with the direct discharge of flue gas, this method not only has a high energy utilization rate but also produces less pollution and is environmentally friendly.

[0033] Step S130: Cold air is delivered to the low-temperature section of the ring cooler, and the exhaust gas after heat exchange in the low-temperature section is passed into the medium-temperature section. Then, the exhaust gas after heat exchange in the medium-temperature section is delivered to the ignition and heat preservation furnace and the first flue gas hood respectively.

[0034] In this step, the blower blows external cold air into the annular cooler. The external cold air flows in a countercurrent to exchange heat, which not only removes a large amount of heat from the high-temperature material, allowing the material to be cooled to the required temperature, but also utilizes the waste heat carried by the exhaust gas after heat exchange to assist in ignition and sintering, greatly improving the efficiency of waste heat utilization.

[0035] Step S140: The material is passed through the high-temperature section, medium-temperature section and low-temperature section of the ring cooler in sequence and cooled to the preset temperature before being discharged.

[0036] Specifically, the preset temperature is usually below 150℃, preferably 100~120℃.

[0037] The sintering method with closed-loop flue gas recirculation provided by the present invention further includes the following steps in step S130:

[0038] Step S1311: The central controller determines whether the ignition and heat preservation furnace is qualified for ignition of sintering raw materials based on the oxygen content and carbon dioxide content information fed back by the first gas detection device located below the ignition and heat preservation furnace.

[0039] Step S1312: If the test is not qualified, the central controller controls the opening of the first valve to decrease and the opening of the second valve to increase.

[0040] Step S1313: If qualified, the central controller controls the first valve and the second valve to maintain their current opening degree.

[0041] The ignition and sintering process mainly involves the reaction of carbon and oxygen to produce carbon dioxide. High oxygen and low carbon dioxide content in the bellows indicates that the oxygen in the air passing through the material layer is not fully consumed, resulting in a weak combustion reaction and insufficient ignition energy, signifying incomplete ignition and substandard combustion. Specifically, the oxygen and carbon dioxide content used to determine whether combustion is satisfactory is set according to the actual operating conditions of the system. For example, in a certain system, when combustion is satisfactory, the oxygen content in the bellows is 10%–20%, and the carbon dioxide content is 1%–10%. Therefore, if the oxygen content exceeds 20% and the carbon dioxide content is below 1%, the combustion is substandard, requiring an increase in the opening of the second valve and a decrease in the opening of the first valve to increase the heat and oxygen available for ignition, thus ensuring proper combustion.

[0042] The sintering method with closed-loop flue gas recirculation provided by the present invention further includes the following steps in step S130:

[0043] Step S1321: The central controller determines whether the exhaust gas supply above the wind box meets the sintering requirements based on the oxygen content and carbon dioxide content information fed back by the first gas detection device located below the first flue gas hood.

[0044] Step S1322: If not, the central controller controls the opening of the third valve 22 above the air box 5 to increase.

[0045] Step S1323: If so, the central controller controls the third valve 22 above the air box 5 to maintain its current opening.

[0046] Each air inlet affects the exhaust gas supply to a specific section of the sintering section below. Changing the opening of the third valve at that inlet alters the airflow into the lower air box. As the trolley moves backward, sintering proceeds slowly from the top of the material layer downwards. The amount of fuel in the material gradually decreases, reducing the fuel demand and consequently the exhaust gas demand. Therefore, the degree of sintering can be determined based on the oxygen and carbon dioxide content in the air box, thus influencing the required exhaust gas volume. The central controller employs a "larger opening at the front, smaller opening at the back, dynamic adaptation" adjustment strategy to adjust the opening of the third valve at each air inlet. Generally, the valve opening decreases as the trolley moves further down the section, but local adjustments are possible due to fluctuations in raw material levels. When the oxygen and carbon dioxide content in the air box below the first flue gas hood stabilizes, the opening of the upper butterfly valve is no longer adjusted.

[0047] Specifically, the oxygen and carbon dioxide content required to determine whether sintering is met is set based on the actual operating conditions of the system. For example, in a certain system, when sintering requirements are met, the oxygen content in the air box is between 15% and 22%, and the carbon dioxide content is between 0.2% and 5%. If the oxygen content is below 15% and the carbon dioxide content is below 0.2%, it indicates that the exhaust gas supply above the air box is insufficient and cannot meet the sintering requirements. In this case, the opening of the third valve above the air box needs to be increased.

[0048] The oxygen and carbon dioxide contents mentioned in this invention are all volume fractions. Both oxygen and carbon dioxide contents were obtained under conditions of good equipment condition, without considering factors such as air leakage that could affect the oxygen and carbon dioxide contents.

[0049] The sintering method with closed-loop flue gas recirculation provided by the present invention further includes the following steps:

[0050] Step S210: The central controller determines whether the air pressure at the high-temperature section outlet is lower than the first preset air pressure value based on the air pressure information fed back by the pressure sensor located at the high-temperature section outlet.

[0051] Step S220: If so, the central controller controls the first exhaust fan and / or the second exhaust fan to increase power.

[0052] Step S230: If not, the central controller controls the first exhaust fan and / or the second exhaust fan to maintain the current power.

[0053] The preset value of the first air pressure should be set according to the system operating conditions, depending on the resistance of the material layer and the resistance of downstream equipment (such as pipelines) in the high-temperature section of the annular cooler. When the air pressure at the outlet of the high-temperature section is lower than the preset value of the first air pressure, the driving force of the exhaust gas in the high-temperature section is insufficient, and it cannot flow smoothly to the subsequent process. Therefore, it is necessary to increase the power of the exhaust fan (mainly by increasing the speed of the exhaust fan) to boost the pressure.

[0054] The sintering method with closed-loop flue gas recirculation provided by the present invention further includes the following steps:

[0055] Step S310: The central controller determines whether the air pressure at the air outlet of the medium temperature section is lower than the second preset air pressure value based on the air pressure information fed back by the pressure sensor located at the air outlet of the medium temperature section.

[0056] Step S320: If so, the central controller controls the blower to increase power.

[0057] Step S330: If not, the central controller controls the blower to maintain the current power.

[0058] The second preset pressure value should be set according to the system operating conditions, depending on the material layer resistance and the resistance of downstream equipment (such as pipelines) in the high-temperature section of the annular cooler. When the air pressure at the outlet of the intermediate temperature section is lower than the second preset pressure value, the driving force of the exhaust gas in the intermediate temperature section is insufficient, and it cannot flow smoothly to the subsequent process. Therefore, it is necessary to increase the power of the blower (mainly by increasing the blower speed) to boost the pressure.

[0059] The sintering method with closed-loop flue gas recirculation provided by the present invention further includes the following steps:

[0060] Step S410: The central controller determines whether the oxygen content at the high-temperature section outlet is lower than the preset oxygen content based on the oxygen content information fed back by the second gas detection device.

[0061] Specifically, the preset oxygen content is usually set to 18%.

[0062] Step S420: If so, the central controller controls the blower to increase the damper opening, so that the oxygen content at the high-temperature section outlet increases to 18%~21%.

[0063] Step S430: If not, the central controller controls the blower to maintain the current damper opening.

[0064] Because the high-temperature section's outlet is located near the end of the entire circulation system, and its oxygen content is lower than the preset oxygen content, this indicates that the overall oxygen content in the circulation system is too low, which is detrimental to sintering. Therefore, it is necessary to blow in more cold air through the blower to increase the oxygen content in the circulation system. Furthermore, increasing the blower damper opening can increase the blower's power (mainly by increasing the blower speed). Even further, oxygen-enriched cold air can be introduced through the blower's inlet.

[0065] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0066] 1. The closed-loop flue gas recirculation sintering system of the present invention introduces sintering flue gas into the high-temperature section of the annular cooler for heat exchange, then uses the high-temperature waste gas for power generation, and the waste gas after power generation is introduced into the flue gas hood and / or ignition and holding furnace to assist sintering. Simultaneously, external cold air is introduced into the low-temperature section of the annular cooler for heat exchange, and then into the medium-temperature section. The waste gas from the medium-temperature section is then introduced into the flue gas hood and / or ignition and holding furnace to assist sintering. Compared with the existing sintering system schemes that directly discharge waste gas, this scheme has no waste gas discharge, which avoids the environmental pollution caused by direct waste gas discharge and allows the waste gas to be fully utilized. Furthermore, this scheme introduces waste gas into different sintering positions according to the temperature gradient: the waste gas from the high-temperature section of the annular cooler is introduced into the second flue gas hood, and the waste gas from the medium-temperature section of the annular cooler is introduced into the ignition and holding furnace and the first flue gas hood respectively, so that the waste gas temperature can be well matched with the temperature required for sintering, which greatly improves the waste heat utilization efficiency and the sintering effect.

[0067] 2. The closed-loop flue gas recirculation sintering system of the present invention has a simple and efficient configuration. Compared with the traditional scheme where blowers are required for the high-temperature, medium-temperature and low-temperature sections of the annular cooler, this scheme sets up two flue ducts to extract flue gas. This can not only share the pressure of exhaust and purification of flue gas, but also make reasonable use of the pressure potential energy of the first and second exhaust fans to drive the flow of exhaust gas in the high-temperature section. Therefore, only a blower needs to be set in the low-temperature section, avoiding the duplication of blowers and reducing system energy consumption.

[0068] 3. The closed-loop flue gas recirculation sintering method of the present invention can use waste gas for different sintering stages according to the temperature gradient, thereby improving the waste heat utilization rate and reducing environmental pressure. At the same time, it can adjust the opening degree of each valve in the system, as well as the power of the exhaust fan and blower, according to the information fed back by the first gas monitoring device, the second gas monitoring device and the pressure sensor. This allows for reasonable control of the amount of waste gas required at each sintering location and the pressure in the circulation system, greatly improving the automation level of the system and helping to improve the efficiency and effect of sintering. Attached Figure Description

[0069] Figure 1 This is a schematic diagram of the sintering system with closed-loop flue gas circulation according to the present invention.

[0070] Reference numerals in the attached figures: 1: Sintering machine; 2: Ignition and holding furnace; 3: First flue hood; 4: Second flue hood; 5: Wind box; 6: First gas detection device; 7: First flue; 8: First dust collector; 9: First exhaust fan; 10: First purifier; 11: Second flue; 12: Second dust collector; 13: Second exhaust fan; 14: Second purifier; 15: Circular cooler; 1501: High temperature section; 1502: Medium temperature section; 1503: Low temperature section; 16: Second gas detection device; 17: Pressure sensor; 18: Power generation device; 19: Blower; 20: First valve; 21: Second valve; 22: Third valve; 23: Fourth valve; 24: Fifth valve. Detailed Implementation

[0071] The technical solution of the present invention will be illustrated below with examples. The scope of protection sought by the present invention includes, but is not limited to, the following embodiments.

[0072] Please refer to Figure 1A closed-loop flue gas recirculation sintering system includes a sintering machine 1, an ignition and holding furnace 2, a flue hood, wind boxes 5, a first flue 7, a first exhaust fan 9, a first dust removal and purification device, an annular cooler 15, and a blower 19. The sintering machine 1 is sequentially arranged with an ignition section and a sintering section along the trolley's running direction. The ignition and holding furnace 2 is located above the ignition section. The flue hood covers the sintering section. A plurality of wind boxes 5 are sequentially and equally spaced below the ignition section and the sintering section. The outlet of each wind box 5 is connected to the first flue 7. The annular cooler 15 is located downstream of the sintering machine 1, and the annular cooler 15 includes a high-temperature section 1501, a medium-temperature section 1502, and a low-temperature section 1503 sequentially arranged along the material running direction. The outlet of the first flue 7 is connected to the air inlet of the high-temperature section 1501. The first exhaust fan 9 and the first dust removal and purification device are both installed on the outlet pipe of the first flue 7. The air outlet of the high-temperature section 1501 is connected to at least the fume hood. The blower 19 is installed at the air inlet of the low-temperature section 1503. The air outlet of the low-temperature section 1503 is connected to the air inlet of the medium-temperature section 1502. The air outlet of the medium-temperature section 1502 is connected to at least the fume hood.

[0073] Preferably, the flue gas hood includes a first flue gas hood 3 and a second flue gas hood 4 arranged sequentially along the running direction of the sintering trolley. The system also includes a power generation device 18. The exhaust gas from the outlet of the high-temperature section 1501 is generated by the power generation device 18 and then introduced into the second flue gas hood 4. The outlet of the medium-temperature section 1502 is connected to the ignition and heat preservation furnace 2 and the first flue gas hood 3, respectively.

[0074] Preferably, a first valve 20 is installed on the pipeline connecting the outlet of the medium-temperature section 1502 to the first flue gas hood 3, and a second valve 21 is installed on the pipeline connecting the outlet of the medium-temperature section 1502 to the ignition and heat preservation furnace 2. The first flue gas hood 3 has a plurality of air inlets evenly spaced along its length, and a third valve 22 is installed at each air inlet.

[0075] Preferably, the system further includes a second flue 11, a second exhaust fan 13, and a second dust removal and purification device. At least a portion of the outlet of the air box 5 located below the sintering section is simultaneously connected to both the first flue 7 and the second flue 11. The outlet of the second flue 11 is connected to the air inlet of the high-temperature section 1501, and both the second exhaust fan 13 and the second dust removal and purification device are located on the outlet pipe of the second flue 11.

[0076] Preferably, a fourth valve 23 is provided on the pipe connecting the first flue 7 to the air box 5, which connects the first flue 7 and the second flue 11, and a fifth valve 24 is provided on the pipe connecting the air box 5 to the second flue 11, which connects the first flue 7 and the second flue 11.

[0077] Preferably, the first dust removal and purification device includes a first dust collector 8 and a first purifier 10. The first dust collector 8, the first exhaust fan 9, and the first purifier 10 are arranged sequentially along the flue gas flow direction. The second dust removal and purification device includes a second dust collector 12 and a second purifier 14. The second dust collector 12, the second exhaust fan 13, and the second purifier 14 are arranged sequentially along the flue gas flow direction.

[0078] Preferably, each of the air boxes 5 located below the ignition and heat preservation furnace 2 and below the first flue gas hood 3 is provided with a first gas detection device 6, which includes an oxygen detector and a carbon dioxide detector.

[0079] Preferably, the outlet of the high-temperature section 1502 is equipped with a second gas detection device 16, which includes an oxygen detector. Both the outlet of the high-temperature section 1501 and the outlet of the medium-temperature section 1502 are equipped with pressure sensors 17.

[0080] Preferably, the system further includes a central controller. The central controller is communicatively connected to the first valve 20, the second valve 21, the third valve 22, the fourth valve 23, the fifth valve 24, the first gas detection device 6, the second gas detection device 16, the pressure sensor 17, the first exhaust fan 9, the second exhaust fan 13, and the blower 19.

[0081] The present invention also provides a control method for a sintering system with closed-loop flue gas recirculation, comprising the following steps:

[0082] Step S110: The sintering raw material is fed into the sintering machine 1 for sintering to obtain high-temperature material, and then the high-temperature material is fed into the ring cooler 15 for cooling.

[0083] Step S120: The flue gas generated by sintering is purified by dust removal and then transported to the high-temperature section 1501 of the annular cooler 15. The exhaust gas discharged from the high-temperature section 1501 is then transported to the power generation device for power generation. After power generation, the exhaust gas is then transported to the second flue gas hood 4.

[0084] Step S130: Cold air is delivered to the low-temperature section 1503 of the ring cooler 15, and the exhaust gas after heat exchange in the low-temperature section 1503 is passed into the medium-temperature section 1502. Then, the exhaust gas after heat exchange in the medium-temperature section 1502 is delivered to the ignition and heat preservation furnace 2 and the first flue gas hood 3 respectively.

[0085] Step S140: The material is passed through the high temperature section 1501, medium temperature section 1502 and low temperature section 1503 of the ring cooler 15 in sequence and cooled to the preset temperature before being discharged.

[0086] The sintering method with closed-loop flue gas recirculation provided by the present invention further includes the following steps in step S130:

[0087] Step S1311: The central controller determines whether the ignition effect of the ignition and heat preservation furnace 2 on the sintering raw materials is qualified based on the oxygen content information and carbon dioxide content information fed back by the first gas detection device 6 located below the ignition and heat preservation furnace 2.

[0088] Step S1312: If the test is not qualified, the central controller controls the opening of the first valve 20 to decrease and the opening of the second valve 21 to increase.

[0089] Step S1313: If qualified, the central controller controls the first valve 20 and the second valve 21 to maintain their current opening.

[0090] The sintering method with closed-loop flue gas recirculation provided by the present invention further includes the following steps in step S130:

[0091] Step S1321: The central controller determines whether the exhaust gas supply above the wind box 5 meets the sintering requirements based on the oxygen content information and carbon dioxide content information fed back by the first gas detection device 6 located below the first flue gas hood 3.

[0092] Step S1322: If not, the central controller controls the opening of the third valve 22 above the air box 5 to increase.

[0093] Step S1323: If so, the central controller controls the third valve 22 above the air box 5 to maintain its current opening.

[0094] The sintering method with closed-loop flue gas recirculation provided by the present invention further includes the following steps:

[0095] Step S210: The central controller determines whether the air pressure at the air outlet of the high-temperature section 1501 is lower than the first preset air pressure value based on the air pressure information fed back by the pressure sensor 17 located at the air outlet of the high-temperature section 1501.

[0096] Step S220: If so, the central controller controls the first exhaust fan 9 and / or the second exhaust fan 13 to increase power.

[0097] Step S230: If not, the central controller controls the first exhaust fan 9 and / or the second exhaust fan 13 to maintain the current power.

[0098] The sintering method with closed-loop flue gas recirculation provided by the present invention further includes the following steps:

[0099] Step S310: The central controller determines whether the air pressure at the air outlet of the medium temperature section 1502 is lower than the second preset air pressure value based on the air pressure information fed back by the pressure sensor 17 located at the air outlet of the medium temperature section 1502.

[0100] Step S320: If so, the central controller controls the blower 19 to increase power.

[0101] Step S330: If not, the central controller controls the blower 19 to maintain its current power.

[0102] The sintering method with closed-loop flue gas recirculation provided by the present invention further includes the following steps:

[0103] Step S410: The central controller determines whether the oxygen content at the outlet of the high-temperature section 1501 is lower than the preset oxygen content based on the oxygen content information fed back by the second gas detection device 16.

[0104] Step S420: If so, the central controller controls the blower 19 to increase the damper opening, so that the oxygen content at the outlet of the high-temperature section 1501 increases to 18%~21%.

[0105] Step S430: If not, the central controller controls the blower 19 to maintain the current damper opening.

[0106] Example 1

[0107] like Figure 1As shown, a closed-loop flue gas recirculation sintering system includes a sintering machine 1, an ignition and holding furnace 2, a flue hood, wind boxes 5, a first flue 7, a first exhaust fan 9, a first dust removal and purification device, an annular cooler 15, and a blower 19. The sintering machine 1 is sequentially arranged with an ignition section and a sintering section along the trolley's running direction. The ignition and holding furnace 2 is located above the ignition section. The flue hood covers the sintering section. Several wind boxes 5 are sequentially and equally spaced below the ignition section and the sintering section. The outlet of each wind box 5 is connected to the first flue 7. The annular cooler 15 is located downstream of the sintering machine 1, and the annular cooler 15 includes a high-temperature section 1501, a medium-temperature section 1502, and a low-temperature section 1503 sequentially arranged along the material running direction. The outlet of the first flue 7 is connected to the air inlet of the high-temperature section 1501. The first exhaust fan 9 and the first dust removal and purification device are both installed on the outlet pipe of the first flue 7. The air outlet of the high-temperature section 1501 is connected to at least the fume hood. The blower 19 is installed at the air inlet of the low-temperature section 1503. The air outlet of the low-temperature section 1503 is connected to the air inlet of the medium-temperature section 1502. The air outlet of the medium-temperature section 1502 is connected to at least the fume hood.

[0108] Example 2

[0109] The system repeats Embodiment 1, except that the flue gas hood includes a first flue gas hood 3 and a second flue gas hood 4 arranged sequentially along the running direction of the sintering trolley. The system also includes a power generation device 18. The exhaust gas from the outlet of the high-temperature section 1501 is generated by the power generation device 18 and then introduced into the second flue gas hood 4. The outlet of the medium-temperature section 1502 is connected to the ignition and heat preservation furnace 2 and the first flue gas hood 3, respectively.

[0110] Among them, the power generation unit 18 includes a waste heat boiler and a steam generator set (steam turbine + generator).

[0111] Example 3

[0112] The embodiment 2 is repeated, except that a first valve 20 is installed on the pipeline connecting the outlet of the medium-temperature section 1502 to the first flue gas hood 3, and a second valve 21 is installed on the pipeline connecting the outlet of the medium-temperature section 1502 to the ignition and heat preservation furnace 2. The first flue gas hood 3 has a plurality of air inlets evenly spaced along its length, and a third valve 22 is installed at each air inlet.

[0113] Among them, the first valve 20, the second valve 21 and the third valve 22 are all electrically controlled butterfly valves that are matched with flow meters.

[0114] Example 4

[0115] The system is a repeat of Embodiment 3, except that it further includes a second flue 11, a second exhaust fan 13, and a second dust removal and purification device. At least a portion of the outlet of the air box 5 located below the sintering section is simultaneously connected to both the first flue 7 and the second flue 11. The outlet of the second flue 11 is connected to the air inlet of the high-temperature section 1501, and both the second exhaust fan 13 and the second dust removal and purification device are located on the outlet pipe of the second flue 11.

[0116] Example 5

[0117] Example 4 is repeated, except that a fourth valve 23 is provided on the pipe connecting the first flue 7 to the wind box 5, which connects the first flue 7 and the second flue 11, and a fifth valve 24 is provided on the pipe connecting the second flue 11 to the wind box 5, which connects the first flue 7 and the second flue 11.

[0118] Among them, the fourth valve 23 and the fifth valve 24 are both electrically controlled butterfly valves that are matched with flow meters.

[0119] Example 6

[0120] The embodiment 5 is repeated, except that the first dust removal and purification device includes a first dust collector 8 and a first purifier 10. The first dust collector 8, the first exhaust fan 9, and the first purifier 10 are arranged sequentially along the flue gas flow direction. The second dust removal and purification device includes a second dust collector 12 and a second purifier 14. The second dust collector 12, the second exhaust fan 13, and the second purifier 14 are arranged sequentially along the flue gas flow direction.

[0121] Among them, the first dust collector 8 and the second dust collector 12 are both bag dust collectors, and the first purifier 10 and the second purifier 14 are both desulfurization and denitrification towers.

[0122] Example 7

[0123] The embodiment 6 is repeated, except that each of the air boxes 5 located below the ignition and heat preservation furnace 2 and below the first flue gas hood 3 is provided with a first gas detection device 6, which includes an oxygen detector and a carbon dioxide detector.

[0124] Example 8

[0125] Repeat Example 7, except that a second gas detection device 16, including an oxygen detector, is provided at the outlet of the high-temperature section 1502. Pressure sensors 17 are provided at both the outlets of the high-temperature section 1501 and the medium-temperature section 1502.

[0126] Example 9

[0127] The system is repeated in Embodiment 8, except that it also includes a central controller. The central controller is communicatively connected to the first valve 20, the second valve 21, the third valve 22, the fourth valve 23, the fifth valve 24, the first gas detection device 6, the second gas detection device 16, the pressure sensor 17, the first exhaust fan 9, the second exhaust fan 13, and the blower 19.

[0128] The central controller is an industrial computer. Communication is achieved via an industrial wireless local area network.

[0129] Application Example 1

[0130] The sintering raw materials are sintered in sintering machine 1 to obtain high-temperature materials. These materials then enter an annular cooler 15 for cooling. The materials sequentially pass through the high-temperature section 1501, the medium-temperature section 1502, and the low-temperature section 1503 of the annular cooler 15, where they are cooled to 110°C before being discharged. The flue gas generated during sintering is purified by dust removal and then transported to the high-temperature section 1501 of the annular cooler 15. The exhaust gas discharged from the high-temperature section 1501 is then transported to a power generation unit for power generation. The exhaust gas after power generation is then transported to the second flue gas hood 4 for waste heat utilization. In the annular cooler 15, cold air is transported to the low-temperature section 1503, and after heat exchange in the low-temperature section 1503, it enters the medium-temperature section 1502. The exhaust gas after heat exchange in the medium-temperature section 1502 is then transported to the ignition and heat preservation furnace 2 and the first flue gas hood 3, respectively.

[0131] During the sintering process, the oxygen and carbon dioxide detectors in the bellows 5 below the ignition and holding furnace 2 can detect the composition of the flue gas at the ignition and holding furnace 2 and transmit the detection data to the central controller for data analysis. When the oxygen content is between 18.5% and 19.5% and the carbon dioxide content is between 2% and 5%, the ignition and holding furnace 2 achieves optimal ignition effect on the sintering raw materials, and the opening of the first valve 20 and the second valve 21 remains unchanged. When the oxygen content is >19.5% and the carbon dioxide content is <2%, it indicates that the ignition and holding furnace is not effectively igniting the sintering raw materials. In this case, the central controller increases the opening of the second valve 21 and decreases the opening of the first valve 20. When the oxygen content is <18.5% and the carbon dioxide content is >5%, it indicates that the ignition and holding furnace has excess heat. In this case, the central controller appropriately decreases the opening of the second valve 21 and appropriately increases the opening of the first valve 20.

[0132] Meanwhile, the oxygen and carbon dioxide detectors in the bellows 5 below the first flue gas hood 3 can detect the composition of the flue gas at the first flue gas hood 3 and transmit the detection data to the central controller for data analysis. As sintering proceeds slowly from the top to the bottom of the material layer, the amount of fuel in the material gradually decreases, and the fuel demand during sintering also gradually decreases. Based on the oxygen and carbon dioxide data, the central controller appropriately adjusts the opening of the third valve 22 at each air inlet of the first flue gas hood 3. Generally, the opening decreases as it moves further down, but local adjustments can be made due to fluctuations in raw materials. When the oxygen content in the bellows below the hot air sintering flue gas hood is between 18% and 20%, and the carbon dioxide content is between 0.3% and 2%, it indicates that the exhaust gas supply meets the sintering requirements, and the opening of the third valve 22 should be kept constant. When the oxygen content in the bellows below the hot air sintering flue gas hood is <18%, and the carbon dioxide content is <0.3%, it indicates that the exhaust gas supply is insufficient and cannot meet the sintering requirements. In this case, the opening of the third valve 22 should be increased to increase the exhaust gas supply. When the oxygen content in the two or three air boxes below the end of the hot air sintering flue gas hood is greater than 20% and the carbon dioxide content is greater than 2%, it indicates that the exhaust gas supply is excessive. At this time, the opening of the third valve 22 should be reduced to decrease the exhaust gas supply.

[0133] During the sintering process, pressure sensors 17 at the exhaust gas outlets of the high-temperature and medium-temperature sections of the annular cooler transmit gas pressure data to the central controller, which then analyzes the data. When the pressure at the exhaust gas outlet of the high-temperature section of the annular cooler 15 is <100Pa (i.e., the first preset pressure value), the central controller increases the power of the first exhaust fan 9 and / or the second exhaust fan 13, thereby increasing the rotation speed for pressurization (the increased pressure subsequently needs to overcome the resistance of the material layer; after passing through the material layer, the air pressure decreases; the high-temperature exhaust gas will be further pressurized by the power generation booster fan when it is used for high-temperature power generation to meet the power generation requirements). When the pressure at the exhaust gas outlet of the medium-temperature section of the annular cooler is <200Pa (i.e., the second preset pressure value), the central controller increases the power of the blower 19, thereby increasing the rotation speed for pressurization (the increased pressure subsequently needs to overcome the resistance of the material layer; after passing through the material layer, the air pressure decreases; the medium-temperature exhaust gas only needs to overcome the pipe resistance during its journey to the first flue gas hood 3 and the ignition and holding furnace 2).

[0134] During the sintering process, flue gas containing carbon dioxide, SOx, and NOx is generated. These substances are collected and treated in the first purifier 10 and the second purifier 14. The oxygen detector at the outlet of the high-temperature section of the annular cooler transmits the detected data to the central controller, which then analyzes the data. When the oxygen content is below 18% (i.e., the preset oxygen content), the central controller controls the blower 19 to increase the damper opening, replenishing fresh air and ultimately increasing the oxygen content in the high-temperature section of the annular cooler to 18%~21%.

Claims

1. A sintering system with closed-loop flue gas circulation, characterized in that: The system includes a sintering machine (1), an ignition and heat preservation furnace (2), a flue hood, wind boxes (5), a first flue (7), a first exhaust fan (9), a first dust removal and purification device, an annular cooler (15), and a blower (19); the sintering machine (1) is provided with an ignition section and a sintering section in sequence along the trolley running direction; the ignition and heat preservation furnace (2) is located above the ignition section; the flue hood is located above the sintering section; several wind boxes (5) are arranged at equal intervals below the ignition section and the sintering section; the outlet of each wind box (5) is connected to the first flue (7); the annular cooler (15) is located downstream of the sintering machine (1), and the annular cooler (15) is located downstream of the sintering machine (1). The system includes a high-temperature section (1501), a medium-temperature section (1502), and a low-temperature section (1503) arranged sequentially along the material running direction; the outlet of the first flue (7) is connected to the air inlet of the high-temperature section (1501); the first exhaust fan (9) and the first dust removal and purification device are both installed on the outlet pipe of the first flue (7); the air outlet of the high-temperature section (1501) is connected to at least the flue hood; the blower (19) is installed at the air inlet of the low-temperature section (1503); the air outlet of the low-temperature section (1503) is connected to the air inlet of the medium-temperature section (1502); and the air outlet of the medium-temperature section (1502) is connected to at least the flue hood.

2. The sintering system with closed-loop flue gas recirculation according to claim 1, characterized in that: The flue gas hood includes a first flue gas hood (3) and a second flue gas hood (4) arranged sequentially along the running direction of the sintering trolley; the system also includes a power generation device (18); the exhaust gas from the outlet of the high-temperature section (1501) is generated by the power generation device (18) and then introduced into the second flue gas hood (4); the outlet of the medium-temperature section (1502) is connected to the ignition and heat preservation furnace (2) and the first flue gas hood (3) respectively.

3. The sintering system with closed-loop flue gas recirculation according to claim 2, characterized in that: A first valve (20) is provided on the pipeline connecting the outlet of the medium temperature section (1502) to the first flue gas hood (3), and a second valve (21) is provided on the pipeline connecting the outlet of the medium temperature section (1502) to the ignition and heat preservation furnace (2); the first flue gas hood (3) is provided with a number of air inlets at equal intervals along its length, and a third valve (22) is provided at each air inlet.

4. The sintering system with closed-loop flue gas recirculation according to any one of claims 1 to 3, characterized in that: The system also includes a second flue (11), a second exhaust fan (13), and a second dust removal and purification device; the outlet of at least a portion of the air box (5) located below the sintering section is simultaneously connected to the first flue (7) and the second flue (11); the outlet of the second flue (11) is connected to the air inlet of the high-temperature section (1501), and the second exhaust fan (13) and the second dust removal and purification device are both installed on the outlet pipe of the second flue (11).

5. The sintering system with closed-loop flue gas recirculation according to claim 4, characterized in that: A fourth valve (23) is provided on the pipe connecting the first flue (7) and the second flue (11) of the wind box (5), and a fifth valve (24) is provided on the pipe connecting the second flue (11) of the wind box (5) of the wind box (5) of the first flue (7) and the second flue (11).

6. The sintering system with closed-loop flue gas recirculation according to any one of claims 4 to 5, characterized in that: The first dust removal and purification device includes a first dust collector (8) and a first purifier (10); the first dust collector (8), the first exhaust fan (9) and the first purifier (10) are arranged sequentially along the flue gas flow direction; the second dust removal and purification device includes a second dust collector (12) and a second purifier (14); the second dust collector (12), the second exhaust fan (13) and the second purifier (14) are arranged sequentially along the flue gas flow direction.

7. The sintering system with closed-loop flue gas recirculation according to any one of claims 1 to 6, characterized in that: Each of the air boxes (5) located below the ignition and heat preservation furnace (2) and below the first flue gas hood (3) is equipped with a first gas detection device (6), which includes an oxygen detector and a carbon dioxide detector.

8. The sintering system with closed-loop flue gas recirculation according to any one of claims 1 to 7, characterized in that: The outlet of the high-temperature section (1502) is equipped with a second gas detection device (16), which includes an oxygen detector; the outlet of the high-temperature section (1501) and the outlet of the medium-temperature section (1502) are both equipped with pressure sensors (17).

9. The sintering system with closed-loop flue gas recirculation according to any one of claims 1 to 8, characterized in that: The system also includes a central controller; the central controller is communicatively connected to the first valve (20), the second valve (21), the third valve (22), the fourth valve (23), the fifth valve (24), the first gas detection device (6), the second gas detection device (16), the pressure sensor (17), the first exhaust fan (9), the second exhaust fan (13), and the blower (19).

10. A sintering method with closed-loop flue gas recirculation, characterized in that: A sintering system with closed-loop flue gas recirculation as described in any one of claims 1 to 9; the method includes: The sintering raw material is fed into the sintering machine (1) for sintering to obtain high-temperature material, and then the high-temperature material is fed into the ring cooler (15) for cooling. The flue gas generated by sintering is purified by dust removal and then transported to the high-temperature section (1501) of the ring cooler (15). The exhaust gas discharged from the high-temperature section (1501) is then transported to the power generation device for power generation. After power generation, the exhaust gas is then transported to the second flue gas hood (4). Cold air is delivered to the low-temperature section (1503) of the ring cooler (15), and the exhaust gas after heat exchange in the low-temperature section (1503) is passed into the medium-temperature section (1502). Then the exhaust gas after heat exchange in the medium-temperature section (1502) is delivered to the ignition and heat preservation furnace (2) and the first flue gas hood (3). The material is cooled to a preset temperature by passing it sequentially through the high-temperature section (1501), medium-temperature section (1502) and low-temperature section (1503) of the ring cooler (15) and then discharged.

11. The sintering method with closed-loop flue gas recirculation according to claim 10, characterized in that: The process of delivering cold air to the low-temperature section (1503) of the annular cooler (15), and then passing the exhaust gas after heat exchange in the low-temperature section (1503) into the medium-temperature section (1502), and then delivering the exhaust gas after heat exchange in the medium-temperature section (1502) to the ignition and heat preservation furnace (2) and the first flue gas hood (3), includes: The central controller judges whether the ignition effect of the ignition and heat preservation furnace (2) on the sintering raw materials is qualified based on the oxygen content information and carbon dioxide content information fed back by the first gas detection device (6) located below the ignition and heat preservation furnace (2). If it fails to meet the requirements, the central controller will control the opening of the first valve (20) to decrease and the opening of the second valve (21) to increase. If qualified, the central controller controls the first valve (20) and the second valve (21) to maintain their existing openings.

12. The sintering method with closed-loop flue gas recirculation according to claim 11, characterized in that: The process of delivering cold air to the low-temperature section (1503) of the annular cooler (15), and then passing the exhaust gas after heat exchange in the low-temperature section (1503) into the medium-temperature section (1502), and then delivering the exhaust gas after heat exchange in the medium-temperature section (1502) to the ignition and heat preservation furnace (2) and the first flue gas hood (3), further includes: The central controller determines whether the exhaust gas supply above the wind box (5) meets the sintering requirements based on the oxygen content information and carbon dioxide content information fed back by the first gas detection device (6) located below the first flue gas hood (3); If not, the central controller controls the opening of the third valve (22) above the air box (5) to increase; If so, the central controller controls the third valve (22) above the air box (5) to maintain its current opening.

13. The sintering method with closed-loop flue gas recirculation according to claims 10-12, characterized in that: The method further includes: The central controller determines whether the air pressure at the outlet of the high-temperature section (1501) is lower than the first preset air pressure value based on the air pressure information fed back by the pressure sensor (17) located at the outlet of the high-temperature section (1501). If so, the central controller controls the first exhaust fan (9) and / or the second exhaust fan (13) to increase power; If not, the central controller controls the first exhaust fan (9) and / or the second exhaust fan (13) to maintain the current power.

14. The sintering method with closed-loop flue gas recirculation according to claims 10-13, characterized in that: The method further includes: The central controller determines whether the air pressure at the outlet of the medium temperature section (1502) is lower than the second preset air pressure value based on the air pressure information fed back by the pressure sensor (17) located at the outlet of the medium temperature section (1502). If so, the central controller controls the blower (19) to increase power; If not, the central controller controls the blower (19) to maintain its current power.

15. The sintering method with closed-loop flue gas recirculation according to claims 10-13, characterized in that: The method further includes: The central controller determines whether the oxygen content at the outlet of the high-temperature section (1501) is lower than the preset oxygen content based on the oxygen content information fed back by the second gas detection device (16). If so, the central controller controls the blower (19) to increase the damper opening, so that the oxygen content at the outlet of the high-temperature section (1501) increases to 18%~21%; If not, the central controller controls the blower (19) to maintain the current damper opening.

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