A stratified and zoned differentiated CO2 injection system and method for blast furnaces

Abstract

This invention discloses a stratified and zoned differentiated CO2 injection system and method for blast furnaces, belonging to the field of low-carbon technology in iron and steel metallurgy. The system includes a CO2 supply and distribution system, a tuyere zone injection module, a lower and middle section injection module, and an upper section injection module. Based on the internal temperature gradient and atmosphere stratification characteristics of the blast furnace, a differentiated CO2 distribution ratio and a synergistic heat compensation strategy are adopted. An oxygen-rich CH4 synergistic injection device is configured in the tuyere zone to promote rapid CO2 conversion using a high-temperature, strong reducing atmosphere; a biomass char synergistic injection device and adjustable-angle nozzles are configured in the lower and middle section of the furnace to achieve efficient gasification; and a low-concentration CO2 mixed injection is used in the upper section of the furnace to promote indirect reduction reactions. This invention achieves a CO2 conversion rate of 65-80%, a coke ratio reduction of 15-25%, and CO2 consumption of 60-90 Nm³ per ton of iron. 3 This significantly reduces carbon emissions and improves ironmaking efficiency.

Description

Technical Field

[0001] This invention relates to the field of low-carbon technology in iron and steel metallurgy, and in particular to a blast furnace layered and zoned differentiated CO2 injection system and method. Background Technology

[0002] The steel industry, as a major carbon emitter, faces enormous pressure and challenges under the trend of energy conservation and emission reduction. The carbon emissions from the blast furnace ironmaking process account for more than 70% of the entire steelmaking process, making it a crucial link in emission reduction. As CO2 is the main carbon emission from blast furnace smelting, its resource utilization has become an important direction for low-carbon ironmaking.

[0003] CO2 can be converted into reduced CO in a blast furnace via the Boudouard reaction (CO2 + C → 2CO, ΔH = +172 kJ / mol). Theoretically, for every 1 Nm³ of CO consumed... 3 CO2 can save approximately 0.54 kg of coke. However, there are obvious temperature gradients and atmospheric stratification characteristics inside the blast furnace: the temperature in the tuyeres swirling zone is 1800-2200℃, with a CO / CO2 ratio >20, exhibiting a strongly reducing atmosphere; the temperature from the furnace belly to the lower part of the furnace body is 1200-1500℃, with a CO / CO2 ratio of 5-10 and a CO content of 25-32%; the temperature in the upper blocky zone of the furnace body is 800-1100℃, with a CO / CO2 ratio of 2-4 and a CO content of 20-28%. These temperature and atmospheric differences determine that the conversion mechanism and reaction rate of CO2 vary significantly in different regions.

[0004] In existing technologies, there are related studies on injecting CO2 into blast furnaces for recycling. CN117512237B discloses an ironmaking method that couples CO2-containing coal gas with biomass injection, but the injection is only performed at a single location, the tuyeres, resulting in a CO2 conversion rate of about 45% and a 5-8% reduction in coke ratio; CN115820954A discloses a blast furnace CO2-biomass carbon injection system that uses injection at both the tuyeres and the furnace body, but the CO2 concentration at both injection points is the same, failing to achieve differentiated control; CN114456854A discloses a hydrogen-rich carbon recycling blast furnace gas decarbonization system, but it still uses a uniform injection strategy.

[0005] However, in practical applications, existing CO2 injection technology has failed to achieve precise and differentiated control of CO2 based on the temperature gradient and atmosphere stratification characteristics inside the blast furnace, resulting in low CO2 conversion efficiency, limited reduction of coke ratio, and high risk of furnace condition fluctuations. Specifically, this manifests as: (1) poor temperature gradient adaptability, with a uniform injection strategy leading to significant differences in CO2 reaction in high-temperature and low-temperature zones; (2) heat compensation is only performed in the tuyeres, while the endothermic reaction of CO2 gasification is distributed throughout the furnace body, resulting in temperature fluctuations of 50-80℃ in the upper and middle parts of the furnace body. To maintain the furnace temperature, it is necessary to increase coke consumption by 8-12 kg / t iron, and the coke ratio decreases by <10%; (3) inaccurate control of the reducing atmosphere: the precise atmosphere is not provided according to the differentiated requirements of the CO / CO2 ratio at different reduction stages, affecting the overall reduction efficiency rate of the blast furnace; (4) CO2 injection, heat compensation, and atmosphere control are independent of each other, making it difficult to achieve a balance between efficient CO2 utilization, significant reduction of coke ratio, and stable furnace operation.

[0006] Therefore, developing a system and method for differentiated and precise CO2 injection and control based on the internal temperature gradient and atmosphere stratification characteristics of the blast furnace is of great value for improving CO2 conversion efficiency (>65%), significantly reducing coke ratio (>15%), reducing carbon emissions, and ensuring stable furnace conditions. Summary of the Invention

[0007] The technical problem this invention aims to solve is that existing blast furnace CO2 injection technologies fail to achieve differentiated and precise control based on the furnace temperature gradient and atmosphere stratification characteristics, resulting in low CO2 conversion efficiency, limited coke ratio reduction, and high risk of furnace condition fluctuations. This invention proposes a blast furnace stratified and zoned differentiated CO2 injection system and method. By employing differentiated CO2 distribution ratios, injection locations, and synergistic heat compensation strategies in different temperature zones, CO2 is fully converted and utilized in each zone, achieving a significant reduction in coke ratio and carbon emissions, thereby improving blast furnace ironmaking efficiency. Details are as follows:

[0008] A blast furnace layered and zoned differentiated CO2 injection system includes a CO2 supply and distribution system, a tuyere zone injection module, a middle and lower furnace body injection module, and an upper furnace body injection module.

[0009] The tuyere zone injection module includes a tuyere CO2 injection gun and an oxygen-enriched methane co-injection device. The tuyere CO2 injection gun is installed in the water cavity after the blast furnace tuyere, with its port at an angle of 30-45° to the center line of the tuyere, and its outlet 100-200mm from the front end of the tuyere. The oxygen-enriched methane co-injection device adopts a double-layer sleeve structure, with methane flowing through the inner tube and CO2 flowing through the outer annular seam, and a spiral guide vane is installed between the inner and outer tubes.

[0010] The lower part of the furnace body includes a nozzle group, an adjustable angle mechanism, and a biomass charcoal co-injection device. The nozzle group is set 3-8 meters above the tuyer plane. One or more nozzles are arranged along the furnace body, with 8-16 nozzles per layer. Each nozzle is inclined downward at a 15-30° angle to the furnace wall normal. The adjustable angle mechanism allows the nozzle angle to be remotely adjusted within the range of 5-40°.

[0011] The upper injection module of the furnace body includes a nozzle group and a low-concentration CO2 mixing device. The nozzle group is set 8-15 meters above the tuyer plane and is evenly arranged along the circumference of the furnace body. The low-concentration CO2 mixing device mixes CO2 with N2 or low-calorific-value gas at a volume ratio of 1:(3-6) and then injects it.

[0012] Preferably, the CO2 supply and distribution system includes a CO2 gas source module, a compression and storage unit, and a three-way distribution valve group; the compression and storage unit pressurizes the CO2 to 0.5-2.0 MPa; the three-way distribution valve group distributes the CO2 to the tuyere injection pipeline, the injection pipeline in the middle and lower part of the furnace body, and the injection pipeline in the upper part of the furnace body, and each branch pipe is equipped with an independent shut-off valve, safety valve, flow meter, and pressure monitor.

[0013] Preferably, in the double-layer sleeve structure, the inner tube diameter is φ20-30mm, the outer circumferential seam diameter is φ30-45mm, and the mixed section length is 100-150mm.

[0014] Preferably, the adjustable angle mechanism uses an electric driver with an angle adjustment accuracy of ±1° and a response time of <30 seconds; an angle sensor is configured to monitor the nozzle angle in real time.

[0015] Preferably, the biochar co-injection device feeds the biochar through a combination of screw feeder and pneumatic conveying, with a biochar addition amount of 2-10 kg / t iron; the biochar undergoes pyrolysis pretreatment at 500-700℃, resulting in a fixed carbon content ≥75%, volatile matter <15%, and particle size of 0.1-3 mm.

[0016] Preferably, the nozzle on the upper part of the furnace body is lined with a wear-resistant ceramic lining; after mixing with low-concentration CO2, the local CO2 concentration is controlled at 5-15%.

[0017] Preferably, the CO2 distribution ratio in the air outlet area is 40-55% of the total injection volume, the CO2 concentration is set to 8-25% of the total injection volume, and the CO / CO2 ratio is >20;

[0018] The CO2 distribution ratio in the lower part of the furnace body is 30-45% of the total injection volume, the CO2 concentration is set to 15-35% of the total injection volume, and the CO / CO2 ratio is 5-10.

[0019] The CO2 distribution ratio in the upper part of the furnace body is 10-20% of the total injection volume, the CO2 concentration is set to 5-15% of the total injection volume, and the CO / CO2 ratio is 2-4.

[0020] Preferably, it also includes a safety protection system, including a nitrogen purging pipeline, a pressure over-limit alarm and automatic shut-off device, a nozzle blockage detection device, and an emergency relief system; when the pipeline pressure is >2.5MPa or <0.3MPa, the automatic shut-off device automatically cuts off the CO2 supply through a shut-off valve.

[0021] The present invention also proposes a jetting method for the above system, comprising the following steps:

[0022] Step 1: Initialization and baseline parameter setting. Collect the original operating parameters of the blast furnace and set the target value of the total CO2 injection rate Q_total to 20-100 Nm. 3 / t iron; Set temperature control targets: 1900-2100℃ in the tuyeres area, 1200-1500℃ in the lower and middle parts of the furnace body, and 800-1100℃ in the upper part of the furnace body; Set atmosphere control targets: CO / CO2 ratio >20 in the tuyeres area, 5-10 in the lower and middle parts of the furnace body, and 2-4 in the upper part of the furnace body;

[0023] Step 2: CO2 distribution strategy calculation. Set the distribution ratio for the vent area α1 = 0.35-0.55, the distribution ratio for the lower part of the furnace body α2 = 0.30-0.45, and the distribution ratio for the upper part of the furnace body α3 = 0.10-0.20, satisfying α1+α2+α3=1; calculate the CO2 flow rate for each area: Q1=α1×Q_total, Q2=α2×Q_total, Q3=α3×Q_total;

[0024] Step 3: CO2 injection and thermal compensation in the vent area. Mix CO2 and methane at a volume ratio of 0.2-0.8 and inject into the vent swirl zone; simultaneously increase the oxygen enrichment rate by 5-15%; increase the air temperature by 10-20℃.

[0025] Step 4: CO2 injection and buffering control in the lower part of the furnace body. Mix CO2 with biochar for injection, with a biochar addition amount of 5-20 kg / t iron; adjust the nozzle angle within the range of 5-40° according to the material surface morphology.

[0026] Step 5: CO2 injection and gentle reduction on the upper part of the furnace body. CO2 and dilution gas are mixed at a volume ratio of 1:(3-6) and then injected into the blocky area; the local CO2 concentration is controlled at 5-15%.

[0027] Step 6: Dynamic optimization and feedback adjustment. Adjust the allocation strategy every 5-10 minutes based on real-time monitoring data; conduct a comprehensive evaluation and optimization adjustment every 8-12 hours.

[0028] Preferably, in step 3, the volume ratio of methane to CO2 is β_CH4=0.2-0.8; CO2 and methane are simultaneously injected through multiple air nozzles; if the theoretical combustion temperature of the air nozzle is <1900℃ or CO / CO2 <20, the methane ratio or oxygen enrichment rate is increased; if the theoretical combustion temperature of the air nozzle is >2100℃, the methane ratio or oxygen enrichment rate is decreased.

[0029] Preferably, in step 4, biochar is mixed with CO2 and injected through a screw feeder and a pneumatic conveying system; the adjustable angle mechanism automatically adjusts the nozzle angle according to the shape of the material surface: 20-25° when the material surface is flat, 15-20° when the center of the material surface is concave, and 25-30° when the edge of the material surface is low.

[0030] Preferably, in step 5, the dilution gas is N2 or low-calorific-value coal gas with a dilution ratio of 3-6; it is evenly sprayed into the upper part of the furnace body through an annular distribution pipe and multiple nozzles.

[0031] Preferably, in step 6, the allocation strategy is optimized and adjusted based on the change in coke ratio, CO2 conversion rate, furnace condition stability, and the stability of the CO / CO2 ratio in each region; if the decrease in coke ratio is not significant, the proportion α1 in the tuyeres area is increased; if the furnace condition fluctuates greatly, Q_total is decreased or the adjustment frequency is increased.

[0032] Preferably, for an effective volume of 4000-5000m³ 3 The large blast furnace has two layers of injection in the lower part of the furnace body. The first layer is located 3-4 meters above the tuyere plane, and the second layer is located 6-8 meters above the tuyere plane. The first layer injects 35-45% of Q2 with a nozzle angle of 25-30°. The second layer injects 55-65% of Q2 with a nozzle angle of 15-20°.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. This invention employs a layered and zoned differentiated CO2 injection strategy. Based on the temperature gradient and atmosphere stratification characteristics inside the blast furnace, differentiated allocation ratios of 35-55%, 30-45%, and 10-20% are used in the tuyeres, lower and middle parts of the furnace body, and upper part of the furnace body, respectively. This allows for the full conversion and utilization of CO2 in different temperature zones, achieving a CO2 conversion rate of 65-80%, far exceeding the 40-55% of existing technologies. Each ton of iron can absorb 60-90 Nm³ of CO2. 3 .

[0035] 2. This invention achieves precise heat balance in each area by configuring synergistic heat compensation devices in each region, using oxygen-enriched methane synergistic injection in the tuyere area, and biomass char synergistic injection in the middle and lower part of the furnace body. This solves the problem of temperature fluctuation in the middle and upper part of the furnace body caused by the single and concentrated heat compensation in the existing technology. The theoretical combustion temperature fluctuation in the tuyere area is controlled within ±15℃, and the pressure difference fluctuation in the whole furnace is ±5-8kPa, which significantly improves the stability of the furnace condition.

[0036] 3. This invention precisely controls the CO / CO2 ratio in each region (>20 in the tuyere area, 5-10 in the lower middle part of the furnace body, and 2-4 in the upper part of the furnace body) and provides differentiated reduction atmospheres according to the needs of different reduction stages during the descent of the furnace charge. This solves the problem of inaccurate reduction atmosphere control in existing technologies. The indirect reduction efficiency in the upper part of the furnace body is increased by 15-20%, the position of the softening zone is stabilized, and the coke ratio can be reduced by 15-25%, far exceeding the 5-10% reduction of existing technologies.

[0037] 4. This invention, through a dynamic optimization and feedback adjustment mechanism, adjusts the allocation strategy every 5-10 minutes based on real-time monitoring data, achieving system-wide coordinated optimization of CO2 injection, heat compensation, and atmosphere control. It achieves a good balance between efficient CO2 utilization, significant reduction in coke ratio, and stable furnace operation, equivalent to a reduction of 105-158 kg CO2 equivalent per ton of iron, resulting in significant economic and environmental benefits. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0039] Figure 2 Is according to Figure 1 An enlarged view of the structure of the blower module in the air outlet area shown;

[0040] Figure 3 yes Figure 2 Sectional view at point BB;

[0041] Figure 4 This is a top view of the arrangement of the injection modules in the lower middle part of the furnace body;

[0042] Figure 5 This is a cross-sectional view of the adjustable nozzle angle mechanism in the lower middle part of the furnace body;

[0043] Figure 6 This is a schematic diagram of the upper part of the furnace body's injection module structure;

[0044] Figure 7 This is a cross-sectional view of a CO2-N2 mixer;

[0045] Figure 8 This is a flowchart of the layered and zoned CO2 injection method.

[0046] In the diagram: 1. Blast furnace body; 2. CO2 gas source module; 3. Compressor; 4. Storage tank; 5. Three-way distribution valve group; 6. Tuyere; 7. Tuyere CO2 lance; 8. Direct injection pipe; 9. Oxygen enrichment device; 10. Methane lance; 11. Double-layer sleeve; 12. Spiral guide vane; 13. Blast furnace burden surface; 14. Softening zone; 15. Tuyere swirl zone; 16. Furnace belly; 17. Furnace body; 18. Furnace throat; 19. CO2 main pipe; 20. Tuyere zone branch pipe; 21. Middle and lower branch pipe of furnace body; 22. Upper branch pipe of furnace body; 23. Biomass charcoal bin; 24. Pneumatic conveying pipe; 25. 26. Adjustable angle mechanism; 27. Electric drive; 28. Angle sensor; 29. ​​Biochar conveying device; 30. Water chamber after tuyere; 31. Water chamber before tuyere; 32. Hot air passage; 33. Shut-off valve; 34. Safety valve; 35. Flow meter; 36. CO2-N2 mixer; 37. Nitrogen purging pipeline; 38. Ring distribution pipe; 39. Piping system; 40. Cooling water pipe; 41. Screw feeder; 42. Refractory material; 43. Nozzle group in the middle and lower part of the furnace body; 44. Nozzle group in the upper part of the furnace body; 45. Pulverized coal spray gun; 46. Block belt; 47. Injection port. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] A blast furnace layered and zoned differentiated CO2 injection system and method, such as Figures 1 to 8 As shown, it includes a CO2 supply and distribution system, a tuyere zone injection module, a middle and lower part injection module of the furnace body, an upper part injection module of the furnace body, and a safety assurance system.

[0049] CO2 supply and distribution system

[0050] like Figure 1 As shown, the CO2 supply and distribution system includes a CO2 gas source module 2, a compressor 3, a storage tank 4, and a three-way distribution valve group 5. The CO2 gas source module 2 provides CO2 gas with a purity of ≥95%, which is pressurized to 0.5-2.0 MPa by the compressor 3 and then stored in the storage tank 4. The CO2 enters the three-way distribution valve group 5 through the CO2 main pipe 19 and is distributed to the branch pipes 20 in the tuyeres area, the branch pipes 21 in the lower middle part of the furnace body, and the branch pipes 22 in the upper part of the furnace body. Each branch pipe is equipped with an independent shut-off valve 32, a safety valve 33, a flow meter 34, and a pressure monitor.

[0051] The three-way distribution valve group 5 achieves differentiated distribution: 35-55% in the tuyere area, 30-45% in the lower middle part of the furnace body, and 10-20% in the upper part of the furnace body. The distribution ratio is dynamically adjusted according to the temperature gradient and atmosphere characteristics of each area, with a flow control accuracy of ±2%.

[0052] Air outlet area blowing module

[0053] like Figure 2 As shown, the tuyere zone injection module is installed at the tuyere 6 of the blast furnace body 1, including the tuyere CO2 injection lance 7, the direct injection pipe 8, the oxygen enrichment device 9, the methane injection lance 10, and the double-layer sleeve 11.

[0054] The CO2 spray gun 7 is installed inside the water chamber 29 behind the air outlet. The nozzle of the spray gun forms a 30-45° angle with the center line of the air outlet 6, and the outlet is located inside the hot air channel 31, 100-200mm from the front end of the air outlet. The double-layer sleeve 11 adopts a coaxial structure. The inner tube has a diameter of φ20-30mm to transport methane, and the outer annular slit has a diameter of φ30-45mm to transport CO2. A spiral guide vane 12 is installed between the inner and outer tubes, and the mixing section has a length of 100-150mm.

[0055] The oxygen enrichment device 9 provides oxygen-enriched gas through the direct-blowing pipe 8, increasing the oxygen enrichment rate by 5-15% and the oxygen concentration by 21-36%. The volume ratio of methane to CO2 is 0.2-0.8, and they are co-injected into the vortex zone 15 of the air outlet. The temperature in the air outlet zone is 1900-2100℃, the CO / CO2 ratio is >20, and the CO2 concentration is set to 8-25% of the total amount of injected gas.

[0056] Lower middle section of the furnace body injection module

[0057] like Figure 4 and Figure 5 As shown, the lower part of the furnace body is equipped with a jetting module located 3-8 meters above the tuyeres, including a lower part of the furnace body nozzle group 42, an adjustable angle mechanism 25, and a biomass char conveying device 28.

[0058] The nozzle group 42 in the lower middle part of the furnace body has 8-16 nozzles evenly arranged along the circumference of the furnace body, and is connected to the branch pipe 21 in the lower middle part of the furnace body through the annular distribution pipe 37. The nozzles are inclined downward at an angle of 15-30° to the normal of the furnace wall, and are covered with refractory material 41 on the outside.

[0059] The adjustable angle mechanism 25 uses an electric drive 26, with an angle adjustment range of 5-40°, an accuracy of ±1°, and a response time of <30 seconds. The biochar conveying device 28 includes a hopper 23, a screw feeder 40, and a pneumatic conveying pipe 24. The biochar addition amount is 5-20 kg / t iron, the fixed carbon content is ≥75%, and the particle size is 0.1-3 mm.

[0060] The temperature in this area is 1200-1500℃, the CO / CO2 ratio is 5-10, the CO content is 25-32%, and the CO2 concentration is set at 15-35% of the total amount of injected gas.

[0061] upper blower module of furnace body

[0062] like Figure 6 As shown, the upper spray module of the furnace body is set at 8-15 meters above the air outlet plane, including the upper nozzle group 43, CO2-N2 mixer 35, and annular distribution pipe 37.

[0063] The upper nozzle group 43 of the furnace body has 6-12 nozzles evenly arranged around the circumference of the furnace body, and uses a wear-resistant ceramic lining. The CO2-N2 mixer 35 mixes CO2 with N2 or low-calorific-value gas at a volume ratio of 1:(3-6) and then sprays it into the annular distribution pipe 37, and then into the nozzles from the annular distribution pipe 37. The local CO2 concentration is controlled at 5-15%.

[0064] The temperature in this area is 800-1100℃, the CO / CO2 ratio is 2-4, the CO content is 20-28%, and the CO2 concentration is set at 5-15% of the total amount of injected gas.

[0065] Security system

[0066] The system includes a nitrogen purging pipeline 36, a pressure over-limit alarm and automatic shut-off device, a nozzle blockage detection device, and an emergency relief system. The nitrogen purging pipeline 36 connects to each branch of the pipeline system 38 and is used to purge the injection pipeline during boiler shutdown, maintenance, or malfunction to prevent backfire. When the pipeline pressure is >2.5MPa or <0.3MPa, the automatic shut-off device automatically cuts off the CO2 supply via shut-off valve 32. The nozzle blockage detection device monitors and determines the blockage status using a differential pressure sensor and flow meter 34, and performs online cleaning using high-pressure gas pulses or mechanical drill rods.

[0067] To better understand the above method, the following specific embodiments are provided.

[0068] Example 1

[0069] 2500m 3 Medium-intensity CO2 injection in blast furnace

[0070] 1. Initial parameter settings

[0071] Basic parameters of the blast furnace: Effective volume: 2500 m³; Designed daily output: 5200 t / d; Raw coke ratio: 350 kg / t; Raw coal ratio: 160 kg / t; Blast flow: 3800 Nm³ / min; Blast temperature: 1180℃; Oxygen enrichment rate: 3.5%

[0072] 2. Implementation of Operating Procedures

[0073] Step S1: Initialization settings

[0074] Set the total CO2 injection target Q_total = 50 Nm 3 / t; Set temperature control targets: T1_target=2000℃ for the tuyeres area, T2_target=1350℃ for the lower middle part of the furnace body, and T3_target=950℃ for the upper part of the furnace body; Set constraints: Total furnace pressure difference Δp<190kPa, material velocity v<28kg / (min·m²), and top gas CO utilization rate η_CO=47-50%.

[0075] Step S2: CO2 allocation strategy calculation

[0076] Based on Q_total=50Nm 3 / t, select distribution coefficients α1=0.45, α2=0.40, α3=0.15; calculate the flow rate of each area: wind gap area Q1=22.5Nm 3 / t (approximately 2925 Nm) 3 / h), Q2=20.0Nm in the lower part of the furnace body. 3 / t (approximately 2600 Nm) 3 / h), Q3=7.5Nm on the upper part of the furnace body. 3 / t (approximately 975 Nm) 3 / h).

[0077] Step S3: CO2 injection and thermal compensation in the air outlet area

[0078] Given a methane to CO2 volume ratio of β_CH4 = 0.20, the calculated methane injection rate is 4.5 Nm³. 3 / t; Calculate the oxygen enrichment rate increment ΔO2_rate = 1.5%, new oxygen enrichment rate = 5.0%; raise the air temperature to 1200℃; inject CO2 2925Nm through 24 air nozzles. 3 / h, synchronously inject CH4585Nm 3 / h; Monitor the theoretical combustion temperature of the air outlet, and stabilize it at around 2050℃.

[0079] Step S4: CO2 injection and buffer control in the lower middle part of the furnace body

[0080] The calculated biochar addition rate is a = (20 × 0.18) / (0.08 × 19.5) ≈ 2.3 kg / t (approximately 300 kg / h); CO2 2600 Nm³ is injected through 12 nozzles at a downward angle of 20°. 3 / h and biochar 300kg / h; real-time monitoring of the temperature in the area, maintaining it at around 1340℃, with fluctuations controlled within ±25℃; monitoring the pressure difference contribution, which increased by about 8kPa, within a controllable range.

[0081] Step S5: CO2 injection and gentle reduction on the upper part of the furnace body

[0082] CO2 and N2 were mixed at a volume ratio of 1:5 and then injected into the upper part of the furnace. The CO2 concentration after mixing was approximately 8.3%. The mixed gas was injected at a concentration of 5850 Nm through eight nozzles. 3 / h (of which CO2 975 Nm 3 / h); Monitor the CO utilization rate of the furnace top gas and maintain it at around 48%.

[0083] Step S6: Dynamic optimization and feedback adjustment

[0084] Data is collected every 10 minutes, and the flow rate in each area is fine-tuned based on real-time temperature and pressure difference; a comprehensive evaluation is conducted every 12 hours: the coke ratio is reduced to 318 kg / t (a decrease of 32 kg / t, or 9.1%), the coal ratio is reduced to 148 kg / t, and the CO2 consumption is 50 Nm³. 3 / t, CO2 conversion rate 68%, and the pressure difference of the whole furnace is stable at 98±6kPa.

[0085] 3. Running effect

[0086] After 72 hours of stable operation, the system entered intelligent optimization mode, where a deep reinforcement learning algorithm took over the allocation decisions. Final stable parameters: Total CO2 55 Nm³. 3 / t, distribution ratios α1=0.43, α2=0.42, α3=0.15, methane 19Nm 3 / t, oxygen enrichment rate 7.2%, biochar 11kg / t. Stabilization effect: coke ratio 295kg / t (reduced by 55kg / t, a decrease of 15.7%), coal ratio 135kg / t (reduced by 25kg / t), CO2 consumption 55Nm³. 3 / t, CO2 conversion rate 72%, total furnace pressure difference 100±5kPa, feed rate 25kg / (min·m 2 The molten iron temperature was 1485℃.

[0087] Example 2

[0088] 4500m 3 High proportion of CO2 injection in large blast furnaces

[0089] 1. Initial parameter settings

[0090] Blast furnace basic parameters: effective volume 4500m³ 3 The design capacity is 10,000 t / d, with a raw coke ratio of 330 kg / t, a raw coal ratio of 180 kg / t, and a target CO2 injection rate of 80 Nm³. 3 / t, target focal ratio ≤280kg / t.

[0091] 2. System Expansion Design

[0092] The furnace has 42 tuyeres and 38 CO2 spray guns; the lower part of the furnace body has two layers of spraying, with 16 nozzles in the first layer (3.5 meters above the tuyeres) and 16 nozzles in the second layer (7 meters above the tuyeres); the upper part of the furnace body has 12 nozzles (12 meters above the tuyeres); the total designed CO2 flow rate is 33,000 Nm³. 3 / h.

[0093] 3. Implementation of Operating Procedures

[0094] Step S1: Initialization settings

[0095] Set the total CO2 injection target Q_total = 80 Nm 3 / t; Set temperature control target: T1_target=2050℃ for the tuyere area, and T1_target=2050℃ for the first layer in the lower middle part of the furnace body. 21 _target=1450℃, second layer T in the lower middle part of the furnace body 22 _target=1280℃, T3_target=1000℃ on the upper part of the furnace body;

[0096] Set constraints: total furnace pressure difference Δp < 200 kPa, target coke ratio ≤ 280 kg / t (reduction ≥ 15%), target CO2 conversion rate ≥ 65%.

[0097] Step S2: CO2 allocation strategy calculation

[0098] Based on Q_total=80Nm 3 / t, using a four-zone allocation strategy, with allocation coefficients α1=0.38 and α 21 =0.20、α 22 =0.25, α3=0.17;

[0099] Calculate the flow rate in each region:

[0100] Wind gap area Q1=30.4Nm 3 / t (approximately 12668 Nm) 3 / h, 335Nm per spray gun 3 / h)

[0101] The first layer of Q in the lower middle part of the furnace body 21 =16.0Nm 3 / t (approximately 6400 Nm) 3 / h)

[0102] The second layer of Q in the lower middle part of the furnace body 22 =20.0Nm 3 / t (approximately 9600 Nm) 3 / h)

[0103] Q3 = 13.6 Nm on the upper part of the furnace body 3 / t (approximately 5600 Nm) 3 / h).

[0104] Step S3: CO2 injection and thermal compensation in the air outlet area

[0105] The heat absorbed by CO2 vaporization in the wind tunnel area = Q1 × 7.68 = 30.4 × 7.68 = 233.5 MJ / t;

[0106] With the methane mixing ratio β_CH4 = 0.44, the calculated methane injection rate is 35 Nm³. 3 / t (of which 60% of the heat is compensated by methane and 40% by oxygen enrichment);

[0107] The calculated oxygen enrichment rate increment ΔO2_rate = 7.5%, and the new oxygen enrichment rate = 11.5%;

[0108] The air temperature was raised to 1240℃; CO2 12668 Nm³ was injected through 38 air nozzles. 3 / h, synchronously inject CH414583Nm 3 / h; Monitor the theoretical combustion temperature of the air outlet, and stabilize it at around 2050℃.

[0109] Step S4: Double-layer CO2 injection and buffer control in the lower middle part of the furnace body

[0110] Adopting a double-layer injection design to adapt to the characteristics of large blast furnaces

[0111] The first layer is located 3.5 meters above the vent (temperature 1400-1500℃), and CO2 6400Nm is injected through 16 nozzles at a downward angle of 27°. 3 / h, calculate the biochar addition amount a1=8kg / t;

[0112] The second layer is located 7 meters above the vent (temperature 1200-1350℃), and injects CO2 at a downward angle of 18° through 16 nozzles, producing 9600 Nm³ of CO2. 3 / h, biochar addition amount a2=6kg / t;

[0113] The total biochar production is 14 kg / t (approximately 5833 kg / h); the temperature in the area is monitored in real time, with the first layer maintained at around 1450℃ and the second layer maintained at around 1280℃, with fluctuations controlled within ±30℃.

[0114] Step S5: CO2 injection and gentle reduction on the upper part of the furnace body

[0115] CO2 and N2 were mixed at a volume ratio of 1:5 and then sprayed into the upper part of the furnace (12 meters above the tuyeres). The CO2 concentration after mixing was approximately 16.7%, and the actual local concentration was approximately 10-12%.

[0116] 33600 Nm of mixed gas was injected through 12 nozzles. 3 / h (of which CO2 5600 Nm 3 / h, N228000 Nm 3 / h), with a flow rate of 2800 Nm per nozzle. 3 / h; Maintain the CO / CO2 ratio within the range of 2-4 to prevent carbon deposition and low-temperature reduction and pulverization of ore.

[0117] Step S6: Dynamic optimization and feedback adjustment

[0118] Data is collected every 10 minutes, and the flow rate in each area is fine-tuned based on real-time temperature and pressure difference; a comprehensive evaluation is conducted every 12 hours: the coke ratio is reduced to 278 kg / t (a decrease of 52 kg / t, or 15.8%), the coal ratio is reduced to 125 kg / t, and the CO2 consumption is 80 Nm³. 3 / t, CO2 conversion rate 70%, and the pressure difference of the whole furnace is stable at 105±7kPa.

[0119] 4. Performance

[0120] After stable operation, the system entered intelligent optimization mode. Final stable parameters: Total CO2 80 Nm³. 3 / t, allocation ratio α1=0.38, α 21 =0.20、α 22 =0.25, α3=0.17, methane 35Nm 3 / t, oxygen enrichment rate 11.5%, biochar 14kg / t. Stabilization effect: coke ratio 278kg / t (reduced by 52kg / t, a decrease of 15.8%), coal ratio 125kg / t (reduced by 55kg / t), CO2 consumption 80Nm³. 3 / t, CO2 conversion rate 70%, annual CO2 emission reduction of approximately 400,000 tons, total furnace pressure difference 105±7kPa, feed rate 27kg / (min·m 2 The furnace operation was stable and smooth.

[0121] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A blast furnace layered and zoned differentiated CO2 injection system, characterized in that, This includes a CO2 supply and distribution system, a tuyere zone injection module, a lower and middle section injection module, and an upper section injection module. The CO2 supply and distribution system includes a CO2 gas source module, a compressor, a storage tank, and a three-way distribution valve group. The CO2 gas source module provides CO2 gas with a purity of ≥95%, which is pressurized by the compressor and stored in the storage tank. The CO2 enters the three-way distribution valve group through the CO2 main pipe and is distributed to the branch pipes in the tuyere area, the branch pipes in the middle and lower part of the furnace body, and the branch pipes in the upper part of the furnace body. Each branch pipe is equipped with an independent shut-off valve, safety valve, flow meter, and pressure monitor. The tuyere zone injection module is located at the tuyere of the blast furnace body. The module includes a tuyere CO2 lance, a direct-fired pipe, an oxygen enrichment device, a methane lance, and a double-layered sleeve. The CO2 lance is installed in the water chamber behind the tuyere, with its port at a 30-45° angle to the tuyere centerline. The outlet is located within the hot blast channel, 100-200 mm from the front end of the tuyere. The double-layered sleeve has a coaxial structure; the inner tube delivers methane, and the outer annular seam delivers CO2. A spiral guide vane is installed between the inner and outer tubes. The oxygen enrichment device provides oxygen-enriched gas through the direct-fired pipe. The lower part of the furnace body's injection module is located 3-8 meters above the tuyeres and includes a lower part of the furnace body nozzle assembly, an adjustable angle mechanism, and a biomass char conveying device. The lower part of the furnace body nozzle assembly has 8-16 nozzles evenly arranged around the circumference of the furnace body and is connected to the lower part of the furnace body branch pipe through a ring distribution pipe. The nozzles are inclined downwards at a 15-30° angle to the furnace wall normal and are covered with refractory material on the outside. The adjustable angle mechanism is driven by an electric motor and allows the nozzle angle to be remotely adjusted within the range of 5-40°. The biomass char conveying device includes a hopper, a screw feeder, and a pneumatic conveying pipe. The upper injection module of the furnace body is set at 8-15 meters above the vent plane, including the upper nozzle group of the furnace body, CO2-N2 mixer, and annular distribution pipe; the upper nozzle group of the furnace body has 6-12 nozzles evenly arranged around the circumference of the furnace body; the CO2-N2 mixer mixes CO2 with N2 or low calorific value gas at a volume ratio of 1:(3-6) and then injects it into the annular distribution pipe, and then enters the nozzle from the annular distribution pipe.

2. The blast furnace layered and zoned differentiated CO2 injection system according to claim 1, characterized in that, In the double-layer casing, the inner tube diameter is φ20-30mm, the outer circumferential seam diameter is φ30-45mm, and the mixed section length is 100-150mm.

3. The blast furnace layered and zoned differentiated CO2 injection system according to claim 1, characterized in that: The adjustable angle mechanism has an angle adjustment accuracy of ±1° and a response time of <30 seconds. It is equipped with an angle sensor to monitor the nozzle angle in real time.

4. The blast furnace layered and zoned differentiated CO2 injection system according to claim 1, characterized in that, In the biochar conveying device, the amount of biochar added is 2-10 kg / t iron. The biochar undergoes pyrolysis pretreatment at 500-700℃, with a fixed carbon content of ≥75%, volatile matter of <15%, and particle size of 0.1-3 mm.

5. A blast furnace layered and zoned differentiated CO2 injection system according to claim 1, characterized in that, The CO2 distribution ratio in the air outlet area is 35-55% of the total injection volume, the CO2 concentration is set at 8-25% of the total injection volume, and the CO / CO2 ratio is >20; The CO2 distribution ratio in the lower part of the furnace body is 30-45% of the total injection volume, the CO2 concentration is set to 15-35% of the total injection volume, and the CO / CO2 ratio is 5-10. The CO2 distribution ratio in the upper part of the furnace body is 10-20% of the total injection volume, the CO2 concentration is set to 5-15% of the total injection volume, and the CO / CO2 ratio is 2-4.

6. A method for differentiated CO2 injection in a blast furnace using the system described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Initialization and baseline parameter setting. Collect the original operating parameters of the blast furnace and set the target value of the total CO2 injection rate Q_total to 20-100 Nm. 3 / t iron, set temperature control targets: 1900-2100℃ in the tuyere zone, 1200-1500℃ in the middle and lower part of the furnace body, and 800-1100℃ in the upper part of the furnace body; set atmosphere control targets: CO / CO2 ratio >20 in the tuyere zone, 5-10 in the middle and lower part of the furnace body, and 2-4 in the upper part of the furnace body; Step 2: CO2 distribution strategy calculation. Set the distribution ratio for the vent area α1 = 0.35-0.55, the distribution ratio for the lower part of the furnace body α2 = 0.30-0.45, and the distribution ratio for the upper part of the furnace body α3 = 0.10-0.20, satisfying α1+α2+α3=1; calculate the CO2 flow rate for each area: Q1=α1×Q_total, Q2=α2×Q_total, Q3=α3×Q_total; Step 3: CO2 injection and thermal compensation in the air outlet area. CO2 and methane are mixed at a volume ratio of 0.2-0.8 and injected into the air outlet swirl area to simultaneously increase the oxygen enrichment rate by 5-15% and raise the air temperature by 10-20℃. Step 4: CO2 injection and buffering control in the lower part of the furnace body. Mix CO2 with biochar for injection. The amount of biochar added is 5-20 kg / t iron. The nozzle angle is adjusted within the range of 5-40° according to the shape of the material surface. Step 5: CO2 injection and gentle reduction on the upper part of the furnace body. CO2 and dilution gas are mixed at a volume ratio of 1:(3-6) and then injected into the blocky area; the local CO2 concentration is controlled at 5-15%. Step 6: Dynamic optimization and feedback adjustment. Adjust the allocation strategy every 5-10 minutes based on real-time monitoring data; conduct a comprehensive evaluation and optimization adjustment every 8-12 hours.

7. The blast furnace layered and zoned differentiated CO2 injection method according to claim 6, characterized in that, In step 3, the volume ratio of methane to CO2 is β_CH4=0.2-0.

8. CO2 and methane are injected simultaneously through multiple duct spray guns. If the theoretical combustion temperature of the duct is <1900℃ or CO / CO2 <20, the methane ratio or oxygen enrichment rate is increased. If the theoretical combustion temperature of the duct is >2100℃, the methane ratio or oxygen enrichment rate is decreased.

8. The blast furnace layered and zoned differentiated CO2 injection method according to claim 6, characterized in that, In step 4, biochar is mixed with CO2 and injected through a screw feeder and pneumatic conveying pipe. The adjustable angle mechanism automatically adjusts the nozzle angle according to the shape of the material surface: 20-25° when the material surface is flat, 15-20° when the center of the material surface is concave, and 25-30° when the edge of the material surface is low.

9. The blast furnace layered and zoned differentiated CO2 injection method according to claim 6, characterized in that, In step 5, the dilution gas is N2 or low-calorific-value coal gas with a dilution ratio of 3-6, and it is evenly sprayed into the upper part of the furnace body through an annular distribution pipe and multiple nozzles.

10. The blast furnace layered and zoned differentiated CO2 injection method according to claim 6, characterized in that, For an effective volume of 4000-5000m³ 3 The large blast furnace has two layers of injection in the lower part of the furnace body. The first layer is located 3-4 meters above the tuyere plane, and the second layer is located 6-8 meters above the tuyere plane. The first layer injects 35-45% of Q2 with a nozzle angle of 25-30°, and the second layer injects 55-65% of Q2 with a nozzle angle of 15-20°.

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