Method for different oxygen content stepwise recycling of sintering flue gas

Abstract

The present application relates to sinter production technical field, specifically disclose a kind of method for sintering flue gas different oxygen content ladder recycling, large flue circulating flue gas selection position adjustment: adjusting air intake position is adjusted from head + tail position to middle + tail portion;Sintering air bellow air intake point is air bellow down pipe, air intake bypass is set in each air intake air bellow down pipe;Oxygen supplement: set oxygen supplement fan pressurization, after mixing with sintering flue gas, the three-stage flue gas of ring cooling is introduced into the circulating seal cover on sintering pallet through return air main pipe and return air branch pipe;Oxygen enrichment: set oxygen enrichment sintering pipeline;Set circulating seal cover;The present application gives full play to the beneficial effect of high temperature, high CO content of large flue waste gas in sintering process carbon-saving and consumption-reducing;While adjusting the position of mixed circulating flue gas returning to sintering, the influence on sintering process is controlled to the minimum, emission reduction is realized while consumption is reduced.Sintering quality is stable as a whole, and multiple benefits of economy, environmental protection and social image are realized.

Description

Technical Field

[0001] This invention relates to the field of sinter production technology, specifically to a method for the stepwise recycling of sinter flue gas with different oxygen contents. Background Technology

[0002] 360m 2 The flue gas recirculation system for the sintering production line is a first-of-its-kind process upgrade project for a certain enterprise. Before the upgrade, 100% of the sintering flue gas was treated by the electrostatic precipitator at the machine head before being discharged into the desulfurization and denitrification system. In response to the national ultra-low emission and carbon reduction policy, the flue gas recirculation process upgrade was implemented.

[0003] The survey of flue gas recirculation processes and their operation within the industry, as shown in Table 1, mainly falls into the following categories:

[0004] Table 1 Comparison of Existing Flue Gas Recirculation Processes and Their Operation

[0005]

[0006] like Figure 2 As shown, the current industry practice generally concentrates the mixed flue gas in the middle of the sintering machine. Due to the low oxygen content and high temperature / low density of the flue gas, the actual amount of oxygen participating in the reaction during sintering is reduced, affecting both the sintering atmosphere and sintering speed, resulting in a generally low actual flue gas recycling rate. Therefore, it is necessary to design a method for the tiered recycling of sintering flue gas with different oxygen contents to solve the problems of low flue gas recycling rate, high energy consumption, and unstable sintering quality in existing sinter production. Summary of the Invention

[0007] To address the problems existing in the prior art, the purpose of this invention is to provide a method for the step-by-step recycling of sintering flue gas with different oxygen contents.

[0008] The technical solution adopted by this invention to solve its technical problem is: a method for the stepwise recycling of sintering flue gas with different oxygen contents, comprising the following steps:

[0009] S1. Adjustment of the location for circulating flue gas in the main flue: The air intake location is adjusted from the head + tail position to the middle + tail position;

[0010] S2. The air intake point of the sintering air box is the air box downcomer pipe, and an air intake bypass is set in each air intake air box downcomer pipe.

[0011] S3, Oxygen Supplementation: An oxygen supplementation fan is set up to pressurize and mix the flue gas from the three-stage annular cooling section with the sintering flue gas. The mixture is then led back to the circulating sealing cover on the sintering trolley through the main return air pipe and the branch return air pipe.

[0012] S4, Oxygen-enriched: Install oxygen-enriched sintering pipelines.

[0013] S5. Install a circulating sealing cover.

[0014] Specifically, the circulating flue gas in the main flue in step S1 is 360m³. 2 The sintering production line has a total of 24 sets of air boxes. The air intake positions are selected from the 24 sets of air boxes. The air intake air box combination is a middle air box + a tail air box. The middle air boxes include air box #11, air box #12 and air box #13, and the tail air boxes include air box #18, air box #19, air box #20 and air box #24.

[0015] Specifically, the No. 12, No. 13, No. 18, No. 19, No. 20 and No. 24 wind boxes are commonly used wind boxes, while No. 11 wind box is used to adjust the CO content. No. 11 wind box is selectively used depending on whether the CO content of the sintering flue gas is controlled.

[0016] Specifically, the flue gas drawn from the upper wind box of the large flue enters the multi-tube dust collector for dust removal through the sintering flue gas branch pipe and the sintering flue gas main pipe, and then enters the hot air main pipe after passing through the circulating main exhaust fan, and is sent back to the upper tail sealing cover of the sintering trolley. All wind boxes for air intake are equipped with adjustable flexible sealing devices.

[0017] Specifically, the air intake box occupies 31% of the total effective sintering area, and the flue gas circulation volume reaches a maximum of 250,000 Nm³. 3 / h.

[0018] Specifically, a three-way air intake reversing valve is installed on the downcomer and air intake bypass in step S3 to switch the operation of the sintering flue gas circulation system and the sintering main extraction system.

[0019] Specifically, in step S3, oxygen replenishment is achieved by detecting the oxygen content of the return air main pipe using an O2 content analyzer. When the oxygen content is lower than the threshold, the cold air valve is opened for adjustment.

[0020] Specifically, the oxygen-enriched sintering pipeline in step S4 is located at the first mixed flue gas branch pipe of the fume hood in the middle of the sintering machine's heat preservation furnace.

[0021] Specifically, in step S5, the circulating sealing cover is installed at the positions of the No. 22, No. 23, and No. 24 air boxes at the tail of the sintering machine. The original dust removal cover is removed and replaced with the circulating sealing cover. Two trolley gaps are reserved between the circulating sealing cover and the original dust removal cover in the middle for daily replacement of the sintering machine trolley. The mixed circulating flue gas is introduced into the tail position of the machine.

[0022] The present invention has the following beneficial effects:

[0023] This invention presents an improved method for the tiered recycling of sintering flue gas with varying oxygen content. Based on an internal and external circulation system, it fully leverages the beneficial effects of the high temperature and high CO content of the main flue gas on carbon saving and energy conservation during sintering. The method selects flue gas from the middle and tail sections of the sintering chamber, mixes it with flue gas from the three stages of the cooling system, and then circulates it for sintering. Simultaneously, the location of the mixed circulating flue gas returning to the sintering chamber is adjusted to minimize its impact on the sintering process, achieving both emission reduction and energy saving. The overall sintering quality remains stable and consistent, achieving multiple benefits in terms of economy, environmental protection, and social image. Attached Figure Description

[0024] Figure 1 This is a bar chart comparing the technical process before and after implementation in the embodiments of the present invention.

[0025] Figure 2 The diagram shows the bar chart of the air box and the schematic diagram of the flue gas destination before the technical process of this invention is put into use.

[0026] Figure 3 The diagram shows the bar chart of the air box and the schematic diagram of the flue gas destination after the technical process of this invention is put into use. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] like Figure 3 As shown, a method for the step-by-step recycling of sintering flue gas with different oxygen contents includes the following steps:

[0029] 1. Adjustment of the location for circulating flue gas in the main flue: 360m 2 The sintering production line has a total of 24 sets of air boxes. The air intake position has been adjusted from the head + tail position to the middle + tail position. The air intake position is selected from the 24 sets of air boxes. The air box combination is the middle air box + tail air box. The selected middle air boxes include air box #11, air box #12 and air box #13. The selected tail air boxes include air box #18, air box #19, air box #20 and air box #24.

[0030] The flue gas drawn from the upper wind box of the main flue enters the multi-tube dust collector for dust removal through the sintering flue gas branch pipe and the sintering flue gas main pipe. After passing through the circulating main exhaust fan, it enters the hot air main pipe and is sent back to the sealing cover at the tail of the sintering trolley. All wind boxes for air intake are equipped with adjustable flexible sealing devices, which adopt flexible bellows-style protective covers.

[0031] 2. The effective sintering area occupied by the air intake box accounts for 31% of the total effective sintering area, and the maximum flue gas circulation volume reaches 250,000 Nm³. 3 / h.

[0032] 3. The air intake point of the sintering air box is the air box downpipe, and an air intake bypass is set in each air intake air box downpipe; a three-way air intake reversing valve is set in the downpipe and the air intake bypass to switch the operation of the sintering flue gas circulation system and the sintering main extraction system.

[0033] 4. Wind boxes #12, #13, #18, #19, #20, and #24 are commonly used wind boxes. Wind box #11 is used to adjust the CO content. Wind box #11 is selectively used depending on whether the CO content of the sintering flue gas is controlled.

[0034] 5. Oxygen supplementation: Set up an oxygen supplementation fan to pressurize and mix the flue gas from the three-stage annular cooling system with the sintering flue gas. The mixture is then led back to the circulating sealing hood on the sintering trolley through the main return air pipe and the branch return air pipe. The oxygen content in the main return air pipe is detected by an O2 content analyzer. When the oxygen content is lower than the threshold, the cold air valve is opened for adjustment.

[0035] 6. Oxygen Enrichment: An oxygen-enriched sintering pipeline is installed. This pipeline is located at the first mixing flue gas branch pipe of the fume hood in the middle of the sintering machine's holding furnace. Through valve control and oxygen content detection, the oxygen content can be increased to 21-25% in the early stages of sintering, mitigating the impact of low-oxygen flue gas on the sintering process.

[0036] 7. Install circulating sealing covers: The circulating sealing covers are installed at the tail of the sintering machine at the positions of the No. 22, No. 23 and No. 24 air boxes. Remove the original dust removal covers and install the circulating sealing covers. Leave two trolley gaps between the circulating sealing covers and the original dust removal covers in the middle for daily replacement of sintering machine trolleys. The mixed circulating flue gas is introduced into the tail of the machine.

[0037] The system solution of this invention:

[0038] System operation and monitoring are automated in the main control room. Start-up and shutdown procedures are operated and monitored through the central control room.

[0039] Process system: including gravity and bipolar multi-tube dust collectors and supporting facilities, circulating fans, oxygen supplement fans, three-way valves, electric valves, and flues.

[0040] Ash removal system: Ash is transported to the return conveyor belt and ash silo through dust collectors, ash discharge valves and pneumatic ash conveying system.

[0041] Electrical System: In this invention, a 10kV power supply is drawn from the newly built high-voltage room to the frequency converter room. The low-voltage power supply is drawn from the transformer in the high-voltage distribution room to the low-voltage distribution cabinet in the low-voltage distribution room.

[0042] Instrumentation and control systems: local and remote pressure, temperature, flow, and O2 content analyzers, and PLC control systems.

[0043] Example:

[0044] 1. Summary of parameters after commissioning: Table 2 shows a comparison of parameters before and after commissioning.

[0045] Table 2 Comparison of parameters before and after the commissioning of the three sets of bellows

[0046]

[0047] The flue gas recirculation capacity of the three sets of air boxes is 185,000 Nm³. 3 / h, fan current 83A, annular cooling oxygen supplement fan air volume 150,000 Nm³ / h 3 / h, fan current 11A, average oxygen content in the fume hood 18.7%, flue gas temperature in the fume hood 162℃, fume hood pressure -1.5Pa, no smoke overflow, no significant changes in the production process, stable sintered ore quality, changes in key sintering parameters, increased fan current by 94A, increased power consumption by 3.3KWh / t, decreased main extraction current from 2×245A to 2×222A, decreased desulfurization and denitrification booster fan current from 256A to 236A, decreased power consumption by 2.3KWh / t, increased overall power consumption by 1KWh / t, decreased fuel ratio by 0.1-0.2%, decreased fuel consumption by 1-2Kg / t, increased exhaust gas volume from 1.9 million Nm³ 3 / h reduced to 1.75 million Nm 3 / h, reducing flue gas emissions by 150,000 Nm³ 3 / h, the CO content in the flue gas decreased from 7941 mg / Nm³ 3 Each decreased to 7079 mg / Nm 3 Reduced by 862 mg / Nmm 3 .

[0048] Table 3 shows a comparison of parameters before and after commissioning:

[0049] Table 3. Parameter Comparison Table Before and After Putting in 4-5 Sets of Wind Boxes

[0050]

[0051] Four sets of bellows were put into operation, with a circulation volume of 215,000 Nm³. 3 / h, 170,000 Nm³ / h, annular cooling and oxygen supplementation air volume 3 / h, the hood pressure is 0Pa with slight smoke overflow, the average oxygen content of the hood is 16.5%, and the flue gas temperature is 155℃. Due to the low oxygen content, the combustion temperature during the sintering process is reduced, and the sintering endpoint temperature is reduced from 450℃ to 400℃. The ore unloading intensity is reduced, and the drum index is reduced by 1.2% compared with the sintering machine not in use.

[0052] Five sets of bellows were put into operation, with a circulation volume of 242,000 Nm³. 3 / h, 150,000 Nm³ / h, annular cooling and oxygen supplementation air volume 3 / h, the hood pressure is 0.2Pa and there is smoke overflow. The average oxygen content in the hood is 14.7%. The flue gas temperature is 150℃. The sintering temperature continues to decrease, and the final temperature drops to 370℃. The strength and particle size of the sintered ore deteriorate significantly, reaching 40% in the 5-10mm stage, which is 15% higher than normal, affecting the smooth operation of the blast furnace.

[0053] In summary, the above information is as follows:

[0054] ① Three sets of air boxes are used for flue gas recirculation, with a recirculation volume of 180,000 Nm³. 3 / h, with an oxygen content of over 18%, has no impact on sintering yield and quality, reduces fuel consumption by 1-2 kg / t, increases electricity consumption by 1 kWh / t, and reduces emissions by 150,000 Nm³. 3 / h, CO content decreased by 862 mg / Nm 3 .

[0055] ② When 4-5 sets of wind tunnel flue gas are used, the oxygen content is reduced to 16.5% and 14.7% respectively. When the oxygen content is below 17%, the combustion temperature during sintering decreases, the ferrous oxide content becomes artificially high, the quality of sintered ore deteriorates, and the drum index decreases by 1.2%, failing to meet the requirements for stable and smooth operation of the blast furnace. If the circulation volume reaches 250,000 Nm³... 3 At a rate of / h, six sets of air boxes need to be put into operation. At that time, the oxygen content will be further reduced, which will cause the quality of sintered ore to deteriorate. It is necessary to supplement oxygen enrichment to meet the needs of sintering production.

[0056] ③As required by the technical appendix of this project, the sintering flue gas recirculation volume is 180,000 m³ / h. 3 When running at / h (standard conditions), the oxygen content of the air drawn by the ring cooler after mixing with the sintering flue gas is not less than 18%.

[0057] ④ A new oxygen-enriched system has been added, based on a sintering flue gas circulation volume of 250,000 m³ / h. 3 When running at / h (standard conditions), after mixing with the annular cooling flue gas, the oxygen content can be ≥18% through the oxygen enrichment system.

[0058] 2. A summary of the RDI of sintered ore after commissioning is shown in Table 4:

[0059] Table 4 Comparison of Sintered Ore Sampling Analysis After Commissioning

[0060]

[0061] like Figure 1 As shown, from March 29 to April 1, 2025, the RDI of sinter was compared by adjusting the position of the flue gas recirculation return material surface. The average improvement of RDI was 1.31% when comparing the three sets of data.

[0062] 3. Expected effects after implementation

[0063] Based on a preliminary comparison of post-commissioning parameters and indicators, it is estimated that flue gas emissions will be reduced by 18%, and sintering solid fuel consumption will be reduced by 1.5 kg / t, demonstrating significant economic, environmental, and social benefits. (See Table 5.)

[0064] Table 5 Comparison of Benefits After Commissioning

[0065]

[0066] After April 2024, the 360 ​​dual-unit flue gas recirculation system was gradually put into operation. Through nearly a year of debugging, adjustment and optimization, by the first half of 2025, the solid fuel consumption of high-alkali and low-alkali sintering units had decreased by 0.62 and 0.71 kg / t respectively compared with 2023-2024; sintering power consumption had decreased by 2.13 kWh / t. Based on the fuel and electricity prices in the first half of the year, the total benefit for the first half of the year was estimated at 6.0318 million yuan.

[0067] This invention is at 360m 2 The sintering production line (with a total of 24 sets of air boxes) intercepts sintering flue gas in the middle air boxes (11#, 12#, 13#) and the tail air boxes (18#, 19#, 20#, 24#), mixes it with the hot air from the three-stage annular cooling system, and forms high-temperature, low-oxygen flue gas. This flue gas is then returned to the middle and tail sections of the sintering machine to participate in the sintering reaction again. This process can achieve a maximum flue gas circulation rate of 25% and a conventional flue gas circulation rate of 18%. By adjusting the position of the air boxes and the proportion of annular cooling flue gas, controlling the oxygen content and temperature of the circulating flue gas within a suitable range, and allocating the sintering positions for the circulating flue gas to participate in the reaction, it is possible to reduce flue gas emissions by 150,000 Nm³ / h while reducing sintering solid fuel consumption by 1.5 kg / t, and maintaining overall stable sintering quality, achieving multiple benefits in terms of economy, environmental protection, and social image.

[0068] This invention optimizes the internal circulation air intake box by using a central and tail air box. This avoids excessive humidity in the front air box, which could negatively impact system lifespan. Simultaneously, adjusting the opening and position of the central air box allows for the regulation of oxygen content and temperature in the internal circulation flue gas. Compared to conventional integrated sealed hoods for flue gas circulation, this process adds a sealed hood at the tail end, enabling low-oxygen flue gas to circulate and sinter, which helps suppress the formation of secondary hematite during cooling on the sintering machine and improves the RDI of the sintered ore. Adding oxygen-enriched pipes to the central sealed hood and increasing oxygen enrichment in the holding furnace section after ignition improves the oxidizing atmosphere in the early stages of sintering, mitigating the impact of low oxygen content in the circulating flue gas on sintering speed and quality. By monitoring the oxygen content within the sealed hood and adjusting the number and position of the circulating flue gas intake boxes, the proportion of oxygen incorporated into the annular cooling and supplementary oxygen fans, and the use of oxygen enrichment in stages, the flue gas circulation ratio can be adjusted. Simultaneously, step-wise control of the circulating flue gas oxygen content achieves both emission reduction and energy saving.

[0069] This invention is not limited to the above-described embodiments. Anyone should know that any structural changes made under the guidance of this invention, and any technical solutions that are the same as or similar to this invention, fall within the protection scope of this invention.

[0070] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A method for the stepwise recycling of sintering flue gas with different oxygen contents, characterized in that, Includes the following steps: S1. Adjustment of the location for circulating flue gas in the main flue: The air intake location is adjusted from the head + tail position to the middle + tail position; S2. The air intake point of the sintering air box is the air box downcomer pipe, and an air intake bypass is set in each air intake air box downcomer pipe. S3, Oxygen Supplementation: An oxygen supplementation fan is set up to pressurize and mix the flue gas from the three-stage annular cooling section with the sintering flue gas. The mixture is then led back to the circulating sealing cover on the sintering trolley through the main return air pipe and the branch return air pipe. S4, Oxygen-enriched: Install oxygen-enriched sintering pipelines. S5. Install a circulating sealing cover.

2. The method for step-by-step recycling of sintering flue gas with different oxygen contents according to claim 1, characterized in that, The circulating flue gas in step S1 is 360m³. 2 The sintering production line has a total of 24 sets of air boxes. The air intake positions are selected from the 24 sets of air boxes. The air intake air box combination is a middle air box + a tail air box. The middle air boxes include air box #11, air box #12 and air box #13, and the tail air boxes include air box #18, air box #19, air box #20 and air box #24.

3. The method for stepwise recycling of sintering flue gas with different oxygen contents according to claim 2, characterized in that, The No. 12, No. 13, No. 18, No. 19, No. 20 and No. 24 wind boxes are commonly used wind boxes, while No. 11 wind box is used to adjust the CO content. No. 11 wind box is selectively used depending on whether the CO content of the sintering flue gas is controlled.

4. The method for stepwise recycling of sintering flue gas with different oxygen contents according to claim 2, characterized in that, The flue gas drawn from the upper air box of the main flue enters the multi-tube dust collector for dust removal through the sintering flue gas branch pipe and the sintering flue gas main pipe. After passing through the circulating main exhaust fan, it enters the hot air main pipe and is sent back to the upper tail sealing cover of the sintering trolley. All air boxes are equipped with adjustable flexible sealing devices.

5. The method for stepwise recycling of sintering flue gas with different oxygen contents according to claim 2, characterized in that, The air intake box occupies 31% of the total effective sintering area, and the flue gas circulation volume reaches a maximum of 250,000 Nm³. 3 / h.

6. The method for stepwise recycling of sintering flue gas with different oxygen contents according to claim 1, characterized in that, In step S3, a three-way air intake reversing valve is installed on the downcomer and the air intake bypass to switch the operation of the sintering flue gas circulation system and the sintering main extraction system.

7. The method for stepwise recycling of sintering flue gas with different oxygen contents according to claim 1, characterized in that, In step S3, oxygen replenishment is achieved by detecting the oxygen content in the return air main pipe using an O2 content analyzer. When the oxygen content is lower than the threshold, the cold air valve is opened for adjustment.

8. The method for stepwise recycling of sintering flue gas with different oxygen contents according to claim 1, characterized in that, The oxygen-enriched sintering pipeline in step S4 is located at the first mixed flue gas branch pipe of the fume hood in the middle of the sintering machine's heat preservation furnace.

9. The method for stepwise recycling of sintering flue gas with different oxygen contents according to claim 1, characterized in that, In step S5, the circulating sealing cover is installed at the positions of the No. 22, No. 23, and No. 24 air boxes at the tail of the sintering machine. The original dust removal cover is removed and replaced with the circulating sealing cover. Two trolley gaps are reserved between the circulating sealing cover and the original dust removal cover in the middle for daily replacement of the sintering machine trolley. The mixed circulating flue gas is introduced into the tail position of the machine.

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