Layered, partitioned and differentiated CO2 injection system and method for blast furnace

Abstract

The invention discloses a layered, zoned and differentiated CO2 injection system and method for a blast furnace, and belongs to the technical field of ferrous metallurgy low carbon. The system comprises a CO2 supply and distribution system, a tuyere area injection module, a furnace body middle-lower part injection module and a furnace body upper part injection module. And according to the temperature gradient and atmosphere layering characteristics in the blast furnace, a differential CO2 distribution proportion and a collaborative thermal compensation strategy are adopted. An oxygen-CH4 synergistic injection device is arranged in a tuyere area, and rapid conversion of CO2 is promoted by using a high-temperature strong reducing atmosphere; a biomass charcoal synergistic injection device and an angle-adjustable nozzle are arranged at the middle lower part of the furnace body, so that efficient gasification reaction is realized; and low-concentration CO2 mixed injection is adopted at the upper part of the furnace body, so that indirect reduction reaction is promoted. According to the invention, the CO2 conversion rate is 65-80%, the coke ratio is reduced by 15-25%, the consumption of CO2 per ton of iron is 260-90Nm < 3 >, the carbon emission is obviously reduced, and the ironmaking efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-carbon steel metallurgy, and particularly relates to a layered and zoned differential CO2 injection system and method for a blast furnace. BACKGROUND

[0002] The steel industry, as a major carbon emitter, is facing great pressure and challenges under the trend of energy saving and emission reduction. Carbon emissions from the blast furnace ironmaking process account for more than 70% of the total steel process, and are the key link of emission reduction. CO2, as the main carbon emission of the blast furnace smelting process, its resource utilization has become an important direction of low-carbon ironmaking.

[0003] CO2 can be converted into reducing CO through the Boudouard reaction (CO2+C→2CO, ΔH=+172kJ / mol) in the blast furnace. In theory, 1 Nm 3 CO2 can save about 0.54 kg of coke. However, there is a significant temperature gradient and atmosphere stratification in the blast furnace: the temperature in the tuyere rotation zone is 1800-2200℃, the CO / CO2 ratio is >20, and the atmosphere is strongly reducing; the temperature in the furnace belly to the middle and lower part of the shaft is 1200-1500℃, the CO / CO2 ratio is 5-10, and the CO content is 25-32%; the temperature in the upper part of the shaft is 800-1100℃, the CO / CO2 ratio is 2-4, and the CO content is 20-28%. This temperature and atmosphere difference determines that the conversion mechanism and reaction rate of CO2 in different regions are significantly different.

[0004] In the prior art, there have been related researches on injecting CO2 into the blast furnace for recycling. CN117512237B discloses an ironmaking method coupled with CO2-containing coal gas and biomass injection, but only injects at a single position of the tuyere, the CO2 conversion rate is about 45%, and the coke ratio is reduced by 5-8%; CN115820954A discloses a blast furnace CO2-biomass char injection system, which injects at the tuyere and the shaft, but the CO2 concentration at the two injection positions is the same, and differential regulation is not achieved; CN114456854A discloses a hydrogen-rich carbon cycle blast furnace gas decarburization system, but still adopts a unified injection strategy.

[0005] However, in practical application, the existing CO2 injection technology fails to achieve differentiated and precise regulation of CO2 according to 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 fluctuation. Specifically, (1) poor temperature gradient adaptability: uniform injection strategy leads to large differences in CO2 reaction in high-temperature and low-temperature zones; (2) only thermal compensation in the tuyere zone, while CO2 gasification endothermic reaction is distributed throughout the shaft, resulting in a temperature fluctuation of 50-80℃ in the upper and middle parts of the shaft, and an increase of 8-12 kg / t of iron in coke consumption to maintain the furnace temperature, with a reduction in coke ratio of less than 10%; (3) inaccurate reduction atmosphere regulation: no precise atmosphere is provided according to the differentiated requirements of CO / CO2 ratio in different reduction stages, affecting the overall reduction efficiency of the blast furnace; (4) CO2 injection, thermal compensation, and atmosphere regulation are independent, making it difficult to balance CO2 efficient utilization, significant reduction of coke ratio, and stable operation of the furnace.

[0006] Therefore, developing a system and method for differentiated and precise regulation of CO2 according to the temperature gradient and atmosphere stratification characteristics inside 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

[0007] The technical problem to be solved by the present application is that the existing CO2 injection technology for blast furnaces fails to achieve differentiated and precise regulation according to the temperature gradient and atmosphere stratification characteristics inside the furnace, resulting in low CO2 conversion efficiency, limited reduction of coke ratio, and high risk of furnace condition fluctuation. To solve this problem, a blast furnace layered and zoned differentiated CO2 injection system and method are proposed, which uses differentiated CO2 distribution ratio, injection position, and coordinated thermal compensation strategy in different temperature zones to fully utilize CO2 in each zone, significantly reduce coke ratio and carbon emissions, and improve blast furnace ironmaking efficiency. Specifically:

[0008] A blast furnace layered and zoned differentiated CO2 injection system, comprising a CO2 supply and distribution system, a tuyere injection module, a middle and lower shaft injection module, and an upper shaft injection module;

[0009] The tuyere injection module comprises a tuyere CO2 injection lance and an oxygen-rich-methane coordinated injection device. The tuyere CO2 injection lance is arranged in the rear water cavity of the blast furnace tuyere, with a 30-45° angle between the port and the tuyere center line, and the outlet is 100-200 mm away from the front end surface of the tuyere. The oxygen-rich-methane coordinated injection device adopts a double-layer sleeve structure, with methane flowing through the inner pipe and CO2 flowing through the outer annular gap, and spiral guide vanes are arranged between the inner and outer pipes;

[0010] The middle and lower part of the shaft injection module comprises a nozzle group, an adjustable angle mechanism and a biomass charcoal synergistic injection device, the nozzle group is arranged at 3-8 meters above the tuyere plane, the nozzles are arranged in one or more layers along the shaft, 8-16 nozzles per layer, each nozzle has a downward inclination angle of 15-30° to the normal line of the shaft wall, and the adjustable angle mechanism allows remote adjustment of the nozzle angle within a range of 5-40°.

[0011] The upper part of the shaft injection module comprises a nozzle group and a low-concentration CO2 mixing device, the nozzle group is arranged at 8-15 meters above the tuyere plane and uniformly along the circumference of the shaft, and 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 comprises a CO2 gas source module, a compression and storage unit and a three-way distribution valve group; the compression and storage unit pressurizes CO2 to 0.5-2.0 MPa; the three-way distribution valve group distributes CO2 to the tuyere injection pipeline, the middle and lower part of the shaft injection pipeline and the upper part of the shaft injection pipeline, and each branch pipeline is provided with an independent shut-off valve, a safety valve, a flowmeter and a pressure monitor.

[0013] Preferably, in the double-layer sleeve structure, the inner tube has a diameter of φ20-30 mm, the outer ring gap has a diameter of φ30-45 mm, and the mixing section has a length of 100-150 mm.

[0014] Preferably, the adjustable angle mechanism adopts an electric drive, the angle adjustment accuracy is ±1°, the response time is <30 seconds, and an angle sensor is configured to monitor the nozzle angle in real time.

[0015] Preferably, the biomass charcoal synergistic injection device feeds through a combination of a screw feeder and pneumatic conveying, the biomass charcoal addition amount is 2-10 kg / t of iron; the biomass charcoal is pretreated by pyrolysis at 500-700℃, the fixed carbon content is ≥75%, the volatile matter is <15%, and the particle size is 0.1-3 mm.

[0016] Preferably, the upper part of the shaft nozzle adopts a wear-resistant ceramic lining; and the local CO2 concentration after mixing is controlled at 5-15%.

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

[0018] The CO2 distribution proportion in the middle and lower part of the shaft is 30-45% of the total injection amount, the CO2 concentration is set to 15-35% of the total injection gas amount, and the CO / CO2 ratio is 5-10;

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

[0020] Preferably, the safety guarantee system further comprises a nitrogen purging pipeline, a pressure overrun alarm and automatic cut-off device, a nozzle blockage detection device, and an emergency relief system; when the pipeline pressure is > 2.5 MPa or < 0.3 MPa, the automatic cut-off device automatically cuts off the CO2 supply through a cut-off valve.

[0021] The present application also proposes a blowing method of the above-mentioned system, comprising the following steps:

[0022] Step 1: initialization and reference parameter setting, collecting the original operation parameters of the blast furnace, setting the total CO2 injection amount target value Q_total to 20-100 Nm 3 / t iron; set the temperature control target: 1900-2100℃ for the tuyere area, 1200-1500℃ for the middle and lower part of the shaft, and 800-1100℃ for the upper part of the shaft; set the atmosphere control target: CO / CO2 ratio > 20 for the tuyere area, CO / CO2 ratio 5-10 for the middle and lower part of the shaft, and CO / CO2 ratio 2-4 for the upper part of the shaft;

[0023] Step 2: CO2 distribution strategy calculation, setting the distribution ratio of the tuyere area α1 = 0.35-0.55, the distribution ratio of the middle and lower part of the shaft α2 = 0.30-0.45, and the distribution ratio of the upper part of the shaft α3 = 0.10-0.20, satisfying α1 + α2 + α3 = 1; calculating the CO2 flow of each area: Q1 = α1 × Q_total, Q2 = α2 × Q_total, Q3 = α3 × Q_total;

[0024] Step 3: CO2 injection and heat compensation in the tuyere area, mixing CO2 and methane with a volume ratio of 0.2-0.8 and injecting into the tuyere convective zone; simultaneously increasing the oxygen enrichment rate by 5-15%; increasing the wind temperature by 10-20℃;

[0025] Step 4: CO2 injection and buffer control in the middle and lower part of the shaft, mixing CO2 and biomass charcoal and injecting, with the biomass charcoal addition amount being 5-20 kg / t iron; adjusting the nozzle angle within the range of 5-40° according to the material surface morphology;

[0026] Step 5: CO2 injection and mild reduction in the upper part of the shaft, mixing CO2 and dilution gas with a volume ratio of 1:(3-6) and injecting into the lump zone; controlling the local CO2 concentration to be 5-15%;

[0027] Step 6: dynamic optimization and feedback adjustment, adjusting the distribution strategy every 5-10 minutes according to the real-time monitoring data; performing 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 synchronously sprayed through multiple tuyere lances; if the theoretical combustion temperature of the tuyere is <1900℃ or CO / CO2 is <20, the methane ratio or oxygen enrichment rate is increased; if the theoretical combustion temperature of the tuyere is >2100℃, the methane ratio or oxygen enrichment rate is reduced.

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

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

[0031] Preferably, in step 6, the distribution strategy is optimized and adjusted according to the coke ratio change amount, CO2 conversion rate, furnace condition stability, and CO / CO2 ratio stability in each region; if the coke ratio does not decrease significantly, the tuyere zone proportion α1 is increased; if the furnace condition fluctuates greatly, Q_total is reduced or the adjustment frequency is increased.

[0032] Preferably, for a large-scale blast furnace with an effective volume of 4000-5000m 3 , two layers of injection are arranged in the middle and lower parts of the shaft, the first layer is located 3-4m above the tuyere plane, and the second layer is located 6-8m above the tuyere plane; the first layer injection Q2 is 35-45%, and the nozzle angle is 25-30°; the second layer injection Q2 is 55-65%, and the nozzle angle is 15-20°.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] 1. The present application adopts a layered and zoned differential CO2 injection strategy, and according to the internal temperature gradient and atmosphere stratification characteristics of the blast furnace, 35-55%, 30-45%, and 10-20% differential distribution proportions are respectively used in the tuyere zone, the middle and lower parts of the shaft, and the upper part of the shaft, so that CO2 is fully converted and utilized in different temperature regions, the CO2 conversion rate can reach 65-80%, which is much higher than the 40-55% of the prior art, and 60-90Nm 3 of CO2 can be consumed per ton of iron.

[0035] 2. The present application configures a collaborative heat compensation device in each region, adopts oxygen-rich-methane collaborative injection in the tuyere zone, and adopts biomass char collaborative injection in the middle and lower parts of the shaft, so that the heat in each region is accurately balanced, the problem of temperature fluctuation in the middle and upper parts of the shaft caused by the single and centralized heat compensation of the prior art is solved, the theoretical combustion temperature fluctuation in the tuyere zone is controlled within ±15℃, the pressure difference fluctuation of the whole furnace is ±5-8kPa, and the furnace condition stability is significantly improved.

[0036] 3. The present application solves the problem of inaccurate reduction atmosphere regulation in the prior art by precisely controlling the CO / CO2 ratio in each region (more than 20 in the tuyere area, 5-10 in the middle and lower part of the shaft, and 2-4 in the upper part of the shaft), and providing differentiated reduction atmosphere according to the needs of different reduction stages during the descent of the furnace charge. The indirect reduction efficiency in the upper part of the shaft is increased by 15-20%, the softening zone position is stable, the coke ratio can be reduced by 15-25%, which is much higher than the 5-10% reduction range of the prior art.

[0037] 4. The present application realizes the system collaborative optimization of CO2 injection, heat compensation and atmosphere regulation by dynamically optimizing and feedback adjusting mechanism, adjusting the distribution strategy every 5-10 minutes according to real-time monitoring data, achieving a good balance between efficient utilization of CO2, significant reduction of coke ratio and stable operation of the furnace, equivalent to reducing 105-158 kg of CO2 equivalent per ton of iron, with significant economic and environmental benefits. BRIEF DESCRIPTION OF DRAWINGS

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

[0039] Figure 2 is a schematic diagram of the overall structure of the present application; Figure 1 is an enlarged view of the structure of the tuyere area injection module shown in

[0040] Figure 3 is a sectional view of B-B in Figure 2

[0041] Figure 4 is a top view of the arrangement of the middle and lower part of the shaft injection module;

[0042] Figure 5 is a sectional view of the adjustable angle mechanism of the middle and lower part of the shaft nozzle;

[0043] Figure 6 is a schematic diagram of the structure of the upper part of the shaft injection module;

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

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

[0046] ​In the figure: 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, straight blow pipe; 9, oxygen enrichment device; 10, methane lance; 11, double-layer sleeve; 12, helical guide vane; 13, blast furnace charge surface; 14, soft melting zone; 15, tuyere rotation zone; 16, furnace bosh; 17, shaft; 18, furnace throat; 19, CO2 main pipe; 20, tuyere zone branch pipe; 21, middle and lower shaft branch pipe; 22, upper shaft branch pipe; 23, biomass charcoal bin; 24, pneumatic conveying pipe; 25, adjustable angle mechanism; 26, electric driver; 27, angle sensor; 28, biomass charcoal conveying device; 29, tuyere rear water cavity; 30, tuyere front water cavity; 31, hot blast channel; 32, cut-off valve; 33, safety valve; 34, flow meter; 35, CO2-N2 mixer; 36, nitrogen purging pipeline; 37, annular distribution pipe; 38, pipeline system; 39, cooling water pipe; 40, screw feeder; 41, refractory material; 42, middle and lower shaft nozzle group; 43, upper shaft nozzle group; 44, pulverized coal lance; 45, lump zone; 46, injection port. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0048] A blast furnace layered and zoned differential CO2 injection system and method, as shown in Figures 1 to 8 , comprises a CO2 supply and distribution system, a tuyere zone injection module, a middle and lower shaft injection module, an upper shaft injection module, and a safety guarantee system.

[0049] CO2 supply and distribution system

[0050] As shown in Figure 1 , the CO2 supply and distribution system comprises 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 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 tuyere zone branch pipe 20, the middle and lower shaft branch pipe 21, and the upper shaft branch pipe 22, each of which is provided with an independent cut-off valve 32, a safety valve 33, a flow meter 34, and a pressure monitor.

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

[0052] Tuyere area injection module

[0053] As shown in Figure 2 , the tuyere area injection module is arranged at the tuyere 6 of the blast furnace body 1, and includes a tuyere CO2 injection lance 7, a straight blow pipe 8, an oxygen enrichment device 9, a methane injection lance 10, and a double-layer sleeve 11.

[0054] The tuyere CO2 injection lance 7 is installed in the tuyere rear water cavity 29, the lance port is at an angle of 30-45° with the center line of the tuyere 6, the outlet is located in the hot blast channel 31, and is 100-200 mm away from the tuyere front end face. The double-layer sleeve 11 adopts a coaxial structure, the inner pipe has a diameter of φ20-30 mm to transport methane, the outer ring gap has a diameter of φ30-45 mm to transport CO2, and a spiral guide vane 12 is arranged between the inner pipe and the outer pipe, and the mixing section length is 100-150 mm.

[0055] The oxygen enrichment device 9 provides oxygen-enriched gas through the straight blow pipe 8, the oxygen enrichment rate is increased by 5-15%, the oxygen concentration is 21-36%, the volume ratio of methane to CO2 is 0.2-0.8, and the two are injected into the tuyere swirl area 15 in cooperation. The temperature of the tuyere area 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] Middle and lower part of shaft injection module

[0057] As shown in Figure 4 and Figure 5 , the middle and lower part of shaft injection module is arranged 3-8 meters above the tuyere plane, and includes a middle and lower part of shaft nozzle group 42, an adjustable angle mechanism 25, and a biomass charcoal conveying device 28.

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

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

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

[0061] Upper shaft injection module

[0062] As shown in Figure 6 , the upper shaft injection module is arranged 8-15 meters above the tuyere plane, and includes an upper shaft nozzle group 43, a CO2-N2 mixer 35, and an annular distribution pipe 37.

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

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

[0065] Safety assurance system

[0066] The safety assurance system includes a nitrogen purge pipeline 36, a pressure overrun alarm and automatic cut-off device, a nozzle blockage detection device, and an emergency relief system. The nitrogen purge pipeline 36 is connected to each branch of the pipeline system 38, and is used to purge the injection pipeline when the furnace is stopped, maintained, or fails, to prevent backfiring. When the pipeline pressure is >2.5MPa or <0.3MPa, the automatic cut-off device automatically cuts off the CO2 supply through the cut-off valve 32. The nozzle blockage detection device monitors and judges the blockage state through a differential pressure sensor and a flowmeter 34, and uses high-pressure gas pulses or mechanical drill rods for online cleaning.

[0067] In order to better understand the above method, the following specific examples are provided.

[0068] Example 1

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

[0070] 1. Initial parameter setting

[0071] Blast furnace basic parameters: effective volume: 2500m³; design daily output: 5200t / d; raw coke ratio: 350kg / t; raw coal ratio: 160kg / t; air volume: 3800Nm³ / min; air temperature: 1180℃; oxygen enrichment rate: 3.5%

[0072] 2. Operation step implementation

[0073] Step S1: initialization setting

[0074] Set the total CO2 injection amount target Q_total = 50 Nm 3 ; Set the temperature control target: tuyere zone T1_target = 2000℃, middle and lower shaft T2_target = 1350℃, upper shaft T3_target = 950℃; Set the constraint condition: total furnace pressure difference Δp < 190 kPa, material speed v < 28 kg / (min·m²), top gas CO utilization rate η_CO = 47-50%.

[0075] Step S2: CO2 distribution strategy calculation

[0076] According to Q_total = 50 Nm 3 / t, select distribution coefficients α1 = 0.45, α2 = 0.40, α3 = 0.15; Calculate the flow rate of each zone: tuyere zone Q1 = 22.5 Nm 3 / t (about 2925 Nm 3 / h), middle and lower shaft Q2 = 20.0 Nm 3 / t (about 2600 Nm 3 / h), upper shaft Q3 = 7.5 Nm 3 / t (about 975 Nm 3 / h).

[0077] Step S3: CO2 injection and heat compensation in the tuyere zone

[0078] Set the volume ratio of methane to CO2 β_CH4 = 0.20, calculate the methane injection amount as 4.5 Nm 3 / t; Calculate the oxygen enrichment rate increment ΔO2_rate = 1.5%, new oxygen enrichment rate = 5.0%; The blast temperature is raised to 1200℃; Inject CO2 2925 Nm 3 / h through 24 tuyere lances, simultaneously inject CH4 585 Nm 3 / h; Monitor the tuyere theoretical combustion temperature, which is stabilized at about 2050℃.

[0079] Step S4: CO2 injection and buffer control in the middle and lower shaft

[0080] Calculate the biomass carbon addition amount a = (20 × 0.18) / (0.08 × 19.5) ≈ 2.3 kg / t (about 300 kg / h); Inject CO2 2600 Nm 3 / h and biomass carbon 300 kg / h through 12 nozzles at a downward angle of 20°; Real-time monitor the temperature in this zone, which is maintained at about 1340℃, with a fluctuation control within ±25℃; Monitor the pressure difference contribution, which increases by about 8 kPa, within the controllable range.

[0081] Step S5: CO2 injection in the upper part of the furnace and mild reduction

[0082] CO2 and N2 were mixed at a volume ratio of 1:5 and injected into the upper part of the furnace, with a CO2 concentration of about 8.3% after mixing; 5850 Nm 3 / h (where CO2 975 Nm 3 / h) was injected through 8 nozzles; the utilization rate of CO2 in the furnace top gas was monitored and maintained at about 48%.

[0083] Step S6: Dynamic optimization and feedback adjustment

[0084] Data was collected every 10 minutes, and the flow rates of each region were adjusted according to real-time temperature and pressure difference; comprehensive evaluation was performed every 12 hours: coke ratio decreased to 318 kg / t (decreased by 32 kg / t, with a decrease of 9.1%), coal ratio decreased to 148 kg / t, CO2 consumption was 50 Nm 3 / t, CO2 conversion rate was 68%, and the overall furnace pressure difference was stable at 98 ± 6 kPa.

[0085] 3. Operation effect

[0086] After 72 hours of stable operation, the system entered the intelligent optimization mode, and the deep reinforcement learning algorithm took over the distribution decision. The final stable parameters: total CO2 55 Nm 3 / t, distribution ratio α1=0.43, α2=0.42, α3=0.15, methane 19 Nm 3 / t, oxygen enrichment rate 7.2%, and biomass char 11 kg / t. Stable effect: coke ratio 295 kg / t (decreased by 55 kg / t, with a decrease of 15.7%), coal ratio 135 kg / t (decreased by 25 kg / t), CO2 consumption 55 Nm 3 / t, CO2 conversion rate 72%, overall furnace pressure difference 100 ± 5 kPa, material speed 25 kg / (min·m 2 ), and molten iron temperature 1485℃.

[0087] Example 2

[0088] 4500m 3 Large-scale high proportion CO2 injection in a blast furnace

[0089] 1. Initial parameter setting

[0090] Basic parameters of the blast furnace: effective volume 4500m 3 , design daily output 10000 t / d, original coke ratio 330 kg / t, original coal ratio 180 kg / t, target CO2 injection amount 80 Nm 3 / t, target coke ratio ≤280 kg / t.

[0091] 2. System expansion design

[0092] The number of tuyeres is 42, and the number of CO2lances is 38; the middle and lower parts of the shaft are blown by two layers of nozzles, the first layer (3.5 meters above the tuyere) has 16 nozzles, and the second layer (7 meters above the tuyere) has 16 nozzles; the upper part of the shaft has 12 nozzles (12 meters above the tuyere); the total design flow of CO2is 33000Nm 3 / h.

[0093] 3. Operation step implementation

[0094] Step S1: initialization setting

[0095] The total CO2blowing amount target Q_total is set to 80Nm 3 / t; the temperature control target is set to: tuyere area T1_target=2050℃, the first layer of the middle and lower parts of the shaft T 21 _target=1450℃, the second layer of the middle and lower parts of the shaft T 22 _target=1280℃, and the upper part of the shaft T3_target=1000℃.

[0096] The constraint condition is set to: the total furnace pressure difference Δp<200kPa, the target coke ratio ≤280kg / t (decrease ≥15%), and the target CO2conversion rate ≥65%.

[0097] Step S2: CO2distribution strategy calculation

[0098] According to Q_total=80Nm 3 / t, a four-zone distribution strategy is adopted, and the distribution coefficients are selected as α1=0.38, α 21 =0.20, α 22 =0.25, and α3=0.17.

[0099] The flow of each zone is calculated:

[0100] The tuyere area Q1 is 30.4Nm 3 / t (about 12668Nm 3 / h, and each lance has 335Nm 3 / h)

[0101] The first layer of the middle and lower parts of the shaft Q 21 =16.0Nm 3 / t (about 6400Nm 3 / h)

[0102] The second layer of the middle and lower parts of the shaft Q 22 =20.0Nm 3 / t (about 9600Nm 3 / h)

[0103] Q3= 13.6 Nm 3 Q1= 5600 Nm 3 / h).

[0104] Step S3: CO2 injection in tuyere area and heat compensation

[0105] Heat absorption of CO2 gasification in tuyere area = Q1 x 7.68 = 30.4 x 7.68 = 233.5 MJ / t

[0106] Set the methane mixing ratio β_CH4= 0.44, and calculate the methane injection amount as 35 Nm 3 / t (where 60% of the heat is compensated by methane, and 40% is compensated by oxygen enrichment);

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

[0108] The blast temperature is raised to 1240℃; inject CO2 2668 Nm 3 / h through 38 tuyere lances, and simultaneously inject CH4 14583 Nm 3 / h; Monitor the theoretical combustion temperature of the tuyere, which stabilizes at about 2050℃.

[0109] Step S4: Double-layer CO2 injection in the middle and lower parts of the shaft and buffer control

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

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

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

[0113] The total biomass carbon is 14 kg / t (about 5833 kg / h); The temperature in this area is monitored in real time, the first layer is maintained at about 1450℃, and the second layer is maintained at about 1280℃, with a fluctuation control within ±30℃.

[0114] Step S5: CO2 injection in the upper part of the shaft and gentle reduction

[0115] After mixing CO2 and N2 at a volume ratio of 1:5, inject into the upper part of the shaft (12 meters above the tuyere), the CO2 concentration after mixing is about 16.7%, and the actual local concentration is about 10-12%.

[0116] Through 12 nozzles, mixed gas 33600 Nm 3 / h (where CO2 5600 Nm 3 / h, N2 2800 Nm 3 / h), each nozzle flow 2800 Nm 3 / h; maintain CO / CO2 ratio in the range of 2-4, prevent carbon deposition and ore low-temperature reduction pulverization.

[0117] Step S6: Dynamic optimization and feedback adjustment

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

[0119] 4. Operation effect

[0120] After stable operation, the system enters intelligent optimization mode. The final stable parameters are: total CO2 amount 80 Nm 3 / t, distribution ratio α1=0.38, α 21 =0.20, α 22 =0.25, α3=0.17, methane 35 Nm 3 / t, oxygen enrichment rate 11.5%, and biomass charcoal 14 kg / t. Stable effect: coke ratio 278 kg / t (reduced by 52 kg / t, with a decrease of 15.8%), coal ratio 125 kg / t (reduced by 55 kg / t), CO2 consumption 80 Nm 3 / t, CO2 conversion rate 70%, annual CO2 emission reduction about 400,000 tons, overall furnace pressure difference 105±7 kPa, and material speed 27 kg / (min·m 2 ).

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

Claims

1. A blast furnace layered zoned differentiated CO2 injection system characterized in that, The system comprises a CO2 supply and distribution system, a tuyere zone injection module, a middle and lower shaft injection module, and an upper shaft injection module. The tuyere zone injection module comprises a tuyere CO2 injection lance and an oxygen-methane injection device, the tuyere CO2 injection lance is arranged in the rear water chamber of the blast furnace tuyere, the port is at an angle of 30-45° with the tuyere center line, and the outlet is 100-200 mm away from the front end surface of the tuyere. The middle and lower shaft injection module comprises a nozzle group, an adjustable angle mechanism, and a biomass charcoal injection device, the nozzle group is arranged 3-8 meters above the tuyere plane, the nozzles are arranged in one or more layers along the shaft, each nozzle is at a downward angle of 15-30° with the normal line of the shaft wall, and the adjustable angle mechanism allows the nozzle angle to be remotely adjusted within a range of 5-40°. The upper shaft injection module comprises a nozzle group and a low-concentration CO2 mixing device, the nozzle group is arranged 8-15 meters above the tuyere plane and uniformly along the shaft circumference, and the low-concentration CO2 mixing device mixes CO2 and N2 or low-calorific-value gas at a volume ratio of 1:(3-6) and then injects the mixture.

2. The differential CO2 injection system for blast furnace according to claim 1, wherein, The CO2 supply and distribution system comprises a CO2 gas source module, a compression and storage unit, and a three-way distribution valve group, the compression and storage unit pressurizes CO2 to 0.5-2.0 MPa, the three-way distribution valve group distributes CO2 to the tuyere injection pipeline, the middle and lower shaft injection pipeline, and the upper shaft injection pipeline, and each branch pipeline is provided with an independent shut-off valve, a safety valve, a flowmeter, and a pressure monitor.

3. The differential CO2 injection system for blast furnace according to claim 1, wherein, In the double-layer sleeve structure, the inner pipe has a diameter of φ20-30 mm, the outer ring gap has a diameter of φ30-45 mm, and the mixing section has a length of 100-150 mm.

4. The differential CO2 injection system for blast furnace according to claim 1, characterized in that: The adjustable angle mechanism adopts an electric drive, the angle adjustment accuracy is ±1°, the response time is less than 30 seconds, and an angle sensor is configured to monitor the nozzle angle in real time.

5. The differential CO2 injection system for blast furnace according to claim 1, wherein, The biomass charcoal injection device feeds biomass charcoal through a combination of a screw feeder and pneumatic conveying, the biomass charcoal addition amount is 2-10 kg / t of iron, the biomass charcoal is pretreated by pyrolysis at 500-700 ℃, the fixed carbon content is ≥75%, the volatile content is <15%, and the particle size is 0.1-3 mm.

6. The differential CO2 injection system for blast furnace according to claim 1, wherein, The upper shaft nozzle is provided with a wear-resistant ceramic lining, and the local CO2 concentration after mixing of low-concentration CO2 is controlled to be 5-15%.

7. The differential CO2 injection system for blast furnace according to claim 1, wherein, The tuyere zone CO2 distribution proportion is 35-55% of the total injection amount, the CO2 concentration is set to 8-25% of the total injection gas amount, and the CO / CO2 ratio is >20; The middle and lower shaft CO2 distribution proportion is 30-45% of the total injection amount, the CO2 concentration is set to 15-35% of the total injection gas amount, and the CO / CO2 ratio is 5-10; The upper shaft CO2 distribution proportion is 10-20% of the total injection amount, the CO2 concentration is set to 5-15% of the total injection gas amount, and the CO / CO2 ratio is 2-4.

8. The differential CO2 injection system for blast furnace according to claim 1, wherein, Safety system including nitrogen purging pipeline, pressure overrun alarm and automatic cut-off device, nozzle blockage detection device and emergency relief system, when the pipeline pressure > 2.5 MPa or < 0.3 MPa, the automatic cut-off device automatically cuts off the CO2 supply through the cut-off valve.

9. A method for differentiating CO2 injection in different zones of a blast furnace by layers by using the system according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: Step 1: initialization and reference parameter setting, collecting original operation parameters of blast furnace, setting the total CO2 injection amount target value Q_total as 20-100 Nm 3 / t iron, setting temperature control target: 1900-2100℃ for tuyere zone, 1200-1500℃ for middle and lower part of shaft, 800-1100℃ for upper part of shaft, setting atmosphere control target: CO / CO2 ratio >20 for tuyere zone, CO / CO2 ratio 5-10 for middle and lower part of shaft, CO / CO2 ratio 2-4 for upper part of shaft; Step 2: CO2 distribution strategy calculation, set the tuyere zone distribution ratio α1 = 0.35-0.55, the middle and lower part of the shaft distribution ratio α2 = 0.30-0.45, the upper part of the shaft distribution ratio α3 = 0.10-0.20, meet α1 + α2 + α3 = 1; Calculate the CO2 flow of each area: Q1 = α1 × Q_total, Q2 = α2 × Q_total, Q3 = α3 × Q_total; Step 3: CO2 injection and heat compensation in the tuyere zone, mix CO2 and methane with a volume ratio of 0.2-0.8 and inject into the tuyere swirl zone, simultaneously increase the oxygen enrichment rate by 5-15%, and the wind temperature by 10-20℃; Step 4: CO2 injection and buffer control in the middle and lower part of the shaft, mix CO2 and biomass char and inject, biomass char addition amount 5-20 kg / t iron, nozzle angle adjusted within 5-40° according to the material surface morphology; Step 5: CO2 injection and mild reduction in the upper part of the shaft, mix CO2 and dilution gas with a volume ratio of 1:(3-6) and inject into the lump zone; Control the local CO2 concentration to be 5-15%; Step 6: Dynamic optimization and feedback adjustment, adjust the distribution strategy every 5-10 minutes according to real-time monitoring data; comprehensive evaluation and optimization adjustment every 8-12 hours.

10. The method according to claim 9, wherein the method is characterized by, In step 3, the volume ratio of methane to CO2 is β_CH4 = 0.2-0.8, CO2 and methane are injected synchronously through multiple tuyere lances, if the tuyere theoretical combustion temperature < 1900℃ or CO / CO2 < 20, increase the methane ratio or oxygen enrichment rate, if the tuyere theoretical combustion temperature > 2100℃, reduce the methane ratio or oxygen enrichment rate.

11. The method according to claim 9, wherein the method is characterized by, In step 4, biomass char is mixed with CO2 and injected through a screw feeder and a pneumatic conveying system, and the adjustable angle mechanism automatically adjusts the nozzle angle according to the material surface morphology: 20-25° when the material surface is flat, 15-20° when the material surface center is concave, and 25-30° when the material surface edge is low.

12. The differential CO2 injection method for blast furnace according to claim 9, characterized in that, In step 5, the dilution gas is N2 or low-calorific-value gas, and the dilution ratio is 3-6, which is uniformly injected into the upper part of the shaft through an annular distribution pipe and multiple nozzles.

13. The differential CO2 injection method for blast furnace according to claim 9, characterized in that, In step 6, the distribution strategy is optimized and adjusted according to the coke ratio change amount, CO2 conversion rate, furnace condition stability, and stability of the CO / CO2 ratio in each area, if the coke ratio does not decrease significantly, increase the tuyere zone proportion α1, if the furnace condition fluctuates greatly, reduce Q_total or increase the adjustment frequency.

14. The method according to claim 9, wherein the method is characterized by, For large blast furnace with effective volume 4000-5000m 3 , two layers of injection are arranged in the middle and lower part of the shaft, the first layer is located 3-4 meters above the tuyere plane, the second layer is located 6-8 meters above the tuyere plane, the first layer injection Q2 is 35-45%, the nozzle angle is 25-30°, the second layer injection Q2 is 55-65%, the nozzle angle is 15-20°.

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