Method for recycling of furnace residue after blast furnace shutdown

Abstract

The present application relates to a kind of high furnace after furnace stop hearth waste recycling method, belong to metallurgical technology field, comprising: crushing, mixing, feeding and the like step.The high furnace after furnace stop hearth waste recycling method provided by the present application, compared with the waste of traditional method is usually directly filled or stacked not only can save land resources, but also can avoid the pollution caused by the hearth waste species harmful element to environment.

Description

Technical Field

[0001] This invention relates to a method for recycling waste from the hearth after a blast furnace shutdown, belonging to the field of metallurgical technology. Background Technology

[0002] The main process of blast furnace ironmaking involves adding coke, iron ore, and flux from the top of the furnace through a rotating charging chute, while hot air is blown into the furnace through the tuyeres. As the hot air rises, it reacts with the coke to produce CO, which reduces the iron in the iron ore. Blast furnace ironmaking is a continuous process, with a designed lifespan of over ten years. Once the blast furnace reaches its service life, it will be shut down for major overhaul. Blast furnace hearth waste is the solid waste removed from the hearth area below the tuyeres after the blast furnace is shut down. It mainly contains unreacted coke, iron ore, and slag. Traditionally, this waste is usually directly landfilled or dumped, which not only occupies a large amount of land resources but also may cause environmental pollution. In recent years, many companies have outsourced its treatment and subsequent further processing, but this also presents problems such as high costs. How to effectively treat and utilize blast furnace hearth waste has become an important research direction. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the above-mentioned technologies and provide a method to make full use of the residual value of hearth waste, increase output, reduce blast furnace fuel ratio, and reduce blast furnace carbon emissions.

[0004] To solve the above-mentioned technical problems, the technical solution proposed by this invention is: a method for recycling hearth waste after blast furnace shutdown, comprising the following steps:

[0005] Step 1: Crush and screen the waste material from the furnace hearth to obtain waste particles with uniform particle size; mix the waste particles with coke and set aside.

[0006] Step 2: Distribute the coke onto the blast furnace charge surface via a rotary chute according to the set coke distribution matrix;

[0007] Step 3: Spread the waste particles and coke mixture evenly on the iron ore on the blast furnace charging belt, and then load it together into the blast furnace top charge hopper.

[0008] A further improvement to the above scheme is that the particle size of the waste material from the furnace hearth is 13 to 25 mm.

[0009] A further improvement to the above scheme is that the mass ratio of waste particles to coke in the mixture of waste particles and coke is 0.5:1 to 1:1.

[0010] A further improvement to the above scheme is that, in step 1, the waste particles are mixed with coke and then loaded into the coke bin below the blast furnace for later use.

[0011] A further improvement to the above scheme is that, in step 3, the waste particles and coke mixture in the blast furnace top charge hopper are spread together with the iron ore on the coke bed through a rotating chute in the area between the center and edge of the blast furnace.

[0012] A further improvement to the above scheme is that the average particle size of the coke is greater than 45mm, M40 is greater than 82%, M10 is less than 6%, CRI is less than 25%, and CSR is greater than 67%; the coke shavings are coke undersize material.

[0013] A further improvement to the above scheme is that: in step 3, the iron ore includes sinter, pellets and lump ore, wherein the sinter has an iron grade greater than 55%, an basicity greater than 1.8, an average particle size greater than 20 mm, and an RDI+6.3 greater than 50%; the pellets have an iron grade greater than 62%, and the lump ore has an iron grade greater than 62%.

[0014] A further improvement to the above scheme is that in step 2, the coke is lifted to the furnace top hopper by the charging device, and a multi-ring feeding method is adopted to distribute the coke onto the blast furnace surface through a rotating chute according to the set coke distribution matrix.

[0015] The present invention provides a method for recycling hearth waste after blast furnace shutdown. Compared with traditional methods that typically involve directly landfilling or stockpiling this waste, this method not only saves land resources but also avoids environmental pollution caused by harmful elements in the hearth waste. After blast furnace shutdown, hearth waste has little usable value besides slag, iron, and unreacted coke. Furthermore, this waste is only generated during blast furnace shutdown, resulting in discontinuous material supply and high costs for further processing. This invention provides a new technology for recycling hearth waste after blast furnace shutdown, returning it to other blast furnaces for reuse. This method is cost-effective and highly feasible. The hearth waste, along with iron ore, is distributed onto the coke bed via a rotating chute. The high reactivity of the coke in the hearth waste weakens the direct reduction reaction between the iron ore and coke. Distributing the hearth waste and iron ore together on the coke bed via a rotating chute in the area between the blast furnace center and edge results in less airflow distribution in this area, thus not affecting the smooth operation of the blast furnace. Detailed Implementation

[0016] Example: The method for recycling hearth waste after blast furnace shutdown in this example includes the following steps:

[0017] Step 1: After the blast furnace is shut down, the waste material from the hearth is crushed and screened to obtain waste particles with uniform particle size. The particle size of the crushed hearth waste material is controlled to be 13-25mm. According to the current blast furnace condition, the waste particles are mixed with coke and briquettes at an appropriate mass ratio and loaded into other coke and briquettes under the blast furnace trough for later use. This mass ratio is usually 0.5:1 to 1:1.

[0018] Step 2: Coke is distributed onto the blast furnace burden surface via a rotating chute according to a pre-defined coke distribution matrix. The average particle size of the coke is greater than 45mm, M40 is greater than 82%, M10 is less than 6%, CRI is less than 25%, and CSR is greater than 67%. M40 represents the percentage of coke with a particle size greater than 40mm after the cold coke drum test, and M10 represents the percentage of coke with a particle size less than 10mm after the cold coke drum test. Both M40 and M10 are cold-state strength indicators of coke. CRI represents the percentage of coke lost due to reaction, characterizing the reactivity of the coke. CSR represents the percentage of coke with a particle size greater than 10mm after the reaction drum test. Coke undersize particles are the same as coke undersize particles, except for particle size.

[0019] Step 3: Subsequently, by controlling the discharge sequence under the trough, the waste particles and coke granules mixture is evenly spread on the iron ore on the blast furnace charging conveyor belt, and then loaded together into the blast furnace top charge hopper. The mixture, along with the iron ore, is distributed on the coke bed through a rotating chute in the area between the center and edge of the blast furnace. This completes the recycling of hearth waste after blast furnace shutdown.

[0020] Iron ore includes sinter, pellets, and lump ore. Sinter has an iron grade greater than 55%, basicity greater than 1.8, average particle size greater than 20 mm, and RDI+6.3 greater than 50%. Pellets have an iron grade greater than 62%, and lump ore has an iron grade greater than 62%.

[0021] More specifically, in step 3, the mixture is loaded into the coke bin below the blast furnace, then evenly spread on top of the iron ore and lifted to the hopper. The angle of the feeding chute is adjusted to 28-36°, and the mixture and iron ore are distributed together on the coke bed via a multi-ring feeding method through a rotating chute in the area between the center and edge of the blast furnace. Inside the blast furnace, when the temperature is above 900-1000℃, the iron ore and coke undergo a direct reduction reaction, and the coke strength is destroyed. By distributing the mixture and iron ore together on the coke bed through a rotating chute, the coke in the mixture, being highly reactive and adjacent to the iron ore, will first undergo a direct reduction reaction with the iron ore when the temperature is above 900-1000℃, thus weakening the direct reduction reaction between the iron ore and coke. Further waste from the hearth contains iron ore, slag, and other components, all of which are detrimental to the smooth flow of air in the blast furnace. Therefore, the mixture is spread together with the iron ore on the coke bed through a rotating chute in the area between the center and edge of the blast furnace. The airflow distribution in the area between the center and edge of the blast furnace is less, which does not affect the smooth operation of the blast furnace.

[0022] The following is an example to illustrate this:

[0023] Example 1: A steel plant with a capacity of 4070m 3During the blast furnace shutdown and major overhaul, approximately 1300 tons of hearth waste were removed from the area below the tuyeres. This hearth waste was crushed and screened to obtain lumps with a particle size of 13–25 mm. It was then returned to a 1280m³... 3 Used in blast furnaces.

[0024] The bellless top charging system is adopted. Based on the original top charging matrix of the blast furnace, coke, hearth waste and coke and iron ore are charged into the top surface of the blast furnace in a cyclical manner.

[0025] Coke is distributed onto the blast furnace burden surface via a rotating chute according to a pre-set coke distribution matrix. Hearth waste is first mixed with coke ore at a 1:1 mass ratio and loaded into the coke ore bin below the chute. Then, by controlling the discharge sequence below the chute, the mixed hearth waste is evenly spread onto the iron ore on the blast furnace charging conveyor belt, and then loaded together into the blast furnace top burden hopper. The hearth waste, along with the iron ore, is then distributed onto the coke layer in the area between the blast furnace center and the blast furnace edge via a rotating chute. This completes the recycling of hearth waste after blast furnace shutdown. 1280m 3 The physical properties of coke and iron ore used in the blast furnace are shown in Table 1, and the physical properties of waste materials from the hearth are shown in Table 2.

[0026] Table 1: 1280m 3 Properties of coke and iron ore used in blast furnaces:

[0027] coke 88.8 5.9 24.7 67.9 / / 52.3 Sintered ore / / / / 1.8 55.6 20.0 Block Ore / / / / / 62.3 /

[0028] Table 2: Physical properties of waste materials from the hearth:

[0029] Furnace waste 56.1 0.6 43.1 42.5 29.6 18.3

[0030] 1280m 3 The blast furnace uses a charge structure of 82% sintered ore and 18% lump ore. During production, when the mechanical probe reaches the set depth, the charge is added to the top of the furnace via a multi-ring distribution method through a rotating chute. 1280m 3 The blast furnace is set to a coke batch size of 8 tons. Coke is lifted to the top charge hopper via a conveyor belt and a rotary chute α is set. c With an angle of 12° to 38.5°, when the material surface reaches a set depth, the coke is evenly spread on the top surface of the furnace using a rotating material distribution chute. The 1280m... 3 The blast furnace has a series-tank top. After coke is transferred from the upper charging hopper to the lower charging hopper, the iron ore hopper and coke hopper below the hopper begin discharging. By controlling the discharging sequence of the hoppers, the hearth waste and coke are evenly spread on the iron ore and then lifted together to the top charging hopper. A rotary chute α is set. o With an angle of 28 to 36 degrees, when the material surface reaches the set depth, the waste from the blast furnace is distributed together with the iron ore onto the coke bed through a rotating material distribution chute in the area between the center and edge of the blast furnace.

[0031] A multi-ring distribution method is used to spread hearth waste along with iron ore onto the coke bed in the area between the blast furnace center and edge using a rotating chute. Inside the blast furnace, when the temperature exceeds 900–1000°C, iron ore undergoes a direct reduction reaction with coke, damaging the coke's strength. By spreading the hearth waste along with the iron ore onto the coke bed using a rotating chute, the high reactivity of the hearth waste (combined with coke) and its proximity to the iron ore ensures that it undergoes a direct reduction reaction with the iron ore first at temperatures above 900–1000°C, thus weakening the direct reduction reaction between the iron ore and coke. Furthermore, the hearth waste also contains iron ore and slag, all of which hinder smooth airflow in the blast furnace. Therefore, spreading the hearth waste along with the iron ore onto the coke bed in the area between the blast furnace center and edge using a rotating chute results in less airflow distribution in this area, thus not affecting the smooth operation of the blast furnace. 1280m 3 Table 3 shows the changes in the main indicators of the blast furnace before and after its use.

[0032] Table 3: Changes in key indicators of the 1280m³ blast furnace before and after its use:

[0033] Before use 45.51 188 527 3.30 After use 45.33 187 521 3.32 Effect -0.18 -1 -6 +0.02

[0034] 1280m 3 After using the waste from the blast furnace hearth, the unreacted coke and iron in the slag are utilized to improve the blast furnace utilization coefficient and reduce the fuel ratio. Simultaneously, the blast furnace pressure differential and gas utilization rate did not fluctuate significantly, indicating that the blast furnace permeability was essentially unaffected. Through the above methods and operational practices, the recycling of hearth waste after blast furnace shutdown was successfully achieved.

[0035] Example 2: A steel plant with a capacity of 3200m 3 During the blast furnace shutdown and major overhaul, approximately 1000 tons of hearth waste were removed from the area below the tuyeres. This hearth waste was crushed and screened to obtain lumps with a particle size of 13–25 mm. It was then returned to a 1580m³... 3 Blast furnace operation. Follow these steps to complete:

[0036] The bellless top charging method is adopted. Based on the original top charging matrix of the blast furnace, coke, hearth waste and coke and iron ore are charged into the top surface of the blast furnace in a cycle.

[0037] Coke is distributed onto the blast furnace burden surface via a rotary chute according to a pre-set coke distribution matrix. Hearth waste is first mixed with coke ore at a 1:3 mass ratio and loaded into the coke ore bin below the chute. Then, by controlling the discharge sequence below the chute, the mixed hearth waste is evenly spread onto the iron ore on the blast furnace charging conveyor belt, and then loaded together into the blast furnace top burden hopper. The hearth waste, along with the iron ore, is then distributed onto the coke layer via a rotary chute in the area between the blast furnace center and the blast furnace edge. This completes the recycling of hearth waste after blast furnace shutdown. 1580m 3 The physical properties of coke and iron ore used in the blast furnace are shown in Table 4, and the physical properties of waste materials from the hearth are shown in Table 5.

[0038] Table 4: 1580m 3 Properties of coke and iron ore used in blast furnaces:

[0039] coke 88.6 5.8 24.5 67.6 / / 45.6 Sintered ore / / / / 1.9 57.6 20.7 Block Ore / / / / / 62.4 /

[0040] Table 5: Physical properties of waste materials from the hearth:

[0041] Furnace waste 56.3 0.8 42.9 42.7 29.8 18.1

[0042] 1580m 3 The blast furnace uses a charge structure of 80% sinter, 15% lump ore, and 5% pellets. During production, when the mechanical probe reaches the set depth, the charge is added to the top of the furnace via a multi-ring distribution method through a rotating chute. 1580m 3 The blast furnace is set to a coke batch size of 10.5t. Coke is lifted to the top charge hopper via a conveyor belt and a rotary chute α is set. c With an angle of 12–40.5°, when the mechanical probe reaches the material surface, the coke is evenly spread on the top of the furnace using a rotating material distribution chute. The 1580m... 3 The blast furnace has a series-tank top. After coke is transferred from the upper charging hopper to the lower charging hopper, the iron ore hopper and coke hopper below the hopper begin discharging. By controlling the discharging sequence of the hoppers, the hearth waste and coke are evenly spread on the iron ore and then lifted together to the top charging hopper. A rotary chute α is set. o With an angle of 26 to 37 degrees, when the material level reaches the material line, the waste from the blast furnace is distributed together with the iron ore onto the coke bed through a rotating material distribution chute in the area between the center and edge of the blast furnace.

[0043] A multi-ring distribution method is used to spread hearth waste along with iron ore onto the coke bed in the area between the blast furnace center and edge using a rotating chute. Inside the blast furnace, when the temperature exceeds 900–1000°C, iron ore and coke undergo a direct reduction reaction, damaging the coke's strength. By spreading the hearth waste along with the iron ore onto the coke bed using a rotating chute, the high reactivity of the hearth waste (combined with coke) and its proximity to the iron ore ensures that it undergoes a direct reduction reaction with the iron ore first at temperatures above 900–1000°C, thus weakening the direct reduction reaction between the iron ore and coke. Furthermore, the hearth waste also contains iron ore and slag, all of which hinder smooth airflow in the blast furnace. Therefore, spreading the hearth waste along with the iron ore onto the coke bed in the area between the blast furnace center and edge using a rotating chute results in less airflow distribution in this area, thus not affecting the smooth operation of the blast furnace. 1580m 3 Table 6 shows the changes in the main indicators of the blast furnace before and after its use.

[0044] Table 6: Changes in key indicators of the 1580m³ blast furnace before and after its operation:

[0045] Before use 46.78 183 519 3.21 After use 46.30 184 517 3.22 Effect -0.48 +1 -2 +0.01

[0046] 1580m 3 After using the waste from the blast furnace hearth, the iron elements in the unreacted coke and slag iron contained within it promote an increase in the blast furnace utilization coefficient and a decrease in the fuel ratio. Simultaneously, the blast furnace pressure differential and gas utilization rate did not fluctuate significantly, indicating that the blast furnace permeability was essentially unaffected. Through the above methods and operational practices, the recycling of hearth waste after blast furnace shutdown was achieved, eliminating the need for outsourcing solid waste disposal.

[0047] Example 3: A steel plant with a capacity of 2600m 3 During the blast furnace shutdown and major overhaul, approximately 800 tons of hearth waste were removed from the area below the tuyeres. This hearth waste was crushed and screened to obtain lumps with a particle size of 13–25 mm. It was then returned to a 3200m³... 3 Blast furnace operation. Follow these steps to complete:

[0048] The bellless top charging method is adopted. Based on the original top charging matrix of the blast furnace, coke, hearth waste and coke and iron ore are charged into the top surface of the blast furnace in a cycle.

[0049] Coke is distributed onto the blast furnace burden surface via a rotating chute according to a pre-set coke distribution matrix. Hearth waste is first mixed with coke ore at a 1:1 mass ratio and loaded into the coke ore bin below the chute. Then, by controlling the discharge sequence below the chute, the mixed hearth waste is evenly spread onto the iron ore on the blast furnace charging conveyor belt, and then loaded together into the blast furnace top burden hopper. The hearth waste, along with the iron ore, is then distributed onto the coke layer via a rotating chute in the area between the blast furnace center and the blast furnace edge. This completes the recycling of hearth waste after blast furnace shutdown. 3200m 3 The physical properties of coke and iron ore used in the blast furnace are shown in Table 7, and the physical properties of waste materials from the hearth are shown in Table 8.

[0050] Table 7: 3200m 3 Properties of coke and iron ore used in blast furnaces:

[0051] coke 89.11 5.90 20.95 69.25 / / 49.54 Sintered ore / / / / 1.9 56.33 20.6 Block Ore / / / / / 62.5 / Pellet Ore 63.72 /

[0052] Table 8: Physical properties of waste materials from the hearth:

[0053] Furnace waste 55.8 0.7 43.6 43.1 28.6 18.8

[0054] 3200m 3 The blast furnace feed composition is 73% sinter, 13% lump ore, and 14% pellets. During production, when the mechanical probe reaches the set depth, the feed is added to the furnace top surface via a multi-ring distribution method through a rotating chute. 3200m 3 The blast furnace is set to a coke batch size of 18.8t. Coke is lifted to the top charge hopper via a conveyor belt, and a rotary chute α is set. c With an angle of 14° to 40°, when the mechanical probe reaches the material surface, the coke is evenly spread on the top of the furnace using a rotating material distribution chute. The 3200m... 3 The blast furnace has a series-tank top. After coke is transferred from the upper charging hopper to the lower charging hopper, the iron ore hopper and coke hopper below the hopper begin discharging. By controlling the discharging sequence of the hoppers, the hearth waste and coke are evenly spread on the iron ore and then lifted together to the top charging hopper. A rotary chute α is set. o With an angle of 28 to 38 degrees, when the material level reaches the material line, the waste from the blast furnace is distributed together with the iron ore onto the coke bed through a rotating material distribution chute in the area between the center and edge of the blast furnace.

[0055] A multi-ring distribution method is used to spread hearth waste along with iron ore onto the coke bed in the area between the blast furnace center and edge using a rotating chute. Inside the blast furnace, when the temperature exceeds 900–1000°C, iron ore and coke undergo a direct reduction reaction, damaging the coke's strength. By spreading the hearth waste along with the iron ore onto the coke bed using a rotating chute, the high reactivity of the hearth waste (combined with coke) and its proximity to the iron ore ensures that it undergoes a direct reduction reaction with the iron ore first at temperatures above 900–1000°C, thus weakening the direct reduction reaction between the iron ore and coke. Furthermore, the hearth waste also contains iron ore and slag, all of which hinder smooth airflow in the blast furnace. Therefore, spreading the hearth waste along with the iron ore onto the coke bed in the area between the blast furnace center and edge using a rotating chute results in less airflow distribution in this area, thus not affecting the smooth operation of the blast furnace. 3200m 3 Table 9 shows the changes in the main indicators of the blast furnace before and after its use.

[0056] Table 9: Changes in key performance indicators of the 3200m³ blast furnace before and after its operation:

[0057] Before use 48.3 194 514 2.50 After use 48.4 193 512 2.52 Effect +0.1 -1 -2 +0.02

[0058] 3200m 3 After using the waste from the blast furnace hearth, the iron elements in the unreacted coke and slag iron contained within it promote an increase in the blast furnace utilization coefficient and a decrease in the fuel ratio. Simultaneously, the blast furnace pressure differential and gas utilization rate did not fluctuate significantly, indicating that the blast furnace permeability was essentially unaffected. Through the above methods and operational practices, the recycling of hearth waste after blast furnace shutdown was achieved, eliminating the need for outsourcing solid waste disposal.

[0059] This invention is not limited to the embodiments described above. All technical solutions formed by equivalent substitutions fall within the scope of protection claimed by this invention.

Claims

1. A method for recycling hearth waste after blast furnace shutdown, characterized in that, Includes the following steps: Step 1: Crush and screen the waste material from the furnace hearth to obtain waste particles with uniform particle size; mix the waste particles with coke and set aside. Step 2: Distribute the coke onto the blast furnace charge surface via a rotary chute according to the set coke distribution matrix; Step 3: Spread the waste particles and coke mixture evenly on the iron ore on the blast furnace charging belt, and then load it together into the blast furnace top charge hopper.

2. The method for recycling hearth waste after blast furnace shutdown according to claim 1, characterized in that: The particle size of the waste material from the furnace hearth is 13 to 25 mm.

3. The method for recycling hearth waste after blast furnace shutdown according to claim 2, characterized in that: In the mixture of waste pellets and coke, the mass ratio of waste pellets to coke is 0.5:1 to 1:

1.

4. The method for recycling hearth waste after blast furnace shutdown according to claim 3, characterized in that: In step 1, the waste particles are mixed with coke and then loaded into the coke bin below the blast furnace for later use.

5. The method for recycling hearth waste after blast furnace shutdown according to claim 4, characterized in that: In step 3, the waste particles and coke mixture in the blast furnace top charge hopper are distributed together with the iron ore on the coke bed in the area between the center and edge of the blast furnace through a rotating chute.

6. The method for recycling hearth waste after blast furnace shutdown according to claim 1, characterized in that: The coke has an average particle size greater than 45 mm, M40 greater than 82%, M10 less than 6%, CRI less than 25%, and CSR greater than 67%; the coke shavings are coke undersize.

7. The method for recycling hearth waste after blast furnace shutdown according to claim 1, characterized in that: The iron ore in step 3 includes sinter, pellets, and lump ore. The sinter has an iron grade greater than 55%, an basicity greater than 1.8, an average particle size greater than 20 mm, and an RDI+6.3 greater than 50%. The pellets have an iron grade greater than 62%, and the lump ore has an iron grade greater than 62%.

8. The method for recycling hearth waste after blast furnace shutdown according to claim 1, characterized in that: In step 2, the coke is lifted to the top of the furnace using a feeding device, and then distributed to the blast furnace surface via a rotating chute according to a multi-ring feeding method and a set coke distribution matrix.