A method for reducing the fuel ratio of scrap steel entering the furnace

Abstract

The present invention relates to the technical field of blast furnace ironmaking, and specifically to a method for reducing the fuel ratio of scrap steel entering the furnace. The method comprises the following steps: hot-melting the scrap steel into blocks, adopting a furnace raw material paving technology, adjusting the scrap steel paving rate, controlling the delay, adding the scrap steel to the center and edge of the blast furnace, and stabilizing the two airflows at the center and edge. The present invention makes full use of iron-containing raw materials, improves the comprehensive furnace quality, reduces the slag ratio, gradually improves the gas utilization rate, reduces the water temperature difference, and finally adjusts the fuel ratio according to an empirical formula on the basis of stabilizing the blast furnace airflow. The adjustment range is small, and the fuel ratio can be effectively reduced, and it is particularly suitable for large blast furnaces with long smelting cycles. In addition, the scrap steel entering the furnace effectively replaces the amount of scrap steel added in the converter process, increases the molten iron output, and effectively alleviates the iron-steel ratio pressure in the subsequent process.

Description

Technical Field

[0001] The invention relates to the technical field of blast furnace ironmaking, and in particular to a method for reducing the fuel ratio of scrap steel entering the furnace. Background Art

[0002] Green, environmental protection and low carbon have become the theme of the times. Carbon consumption in blast furnace ironmaking accounts for an important share in the steel smelting process. Reducing the blast furnace fuel ratio is of great significance to guiding green technology innovation. In addition, coal prices continue to rise, environmental factors are gradually increasing, and high-yield, high-quality, and low-consumption smelting models are particularly important. Blast furnace fuel plays the role of heating agent, reducing agent, carburizing agent, and material column skeleton in the smelting process. Simply reducing the fuel ratio will inevitably cause abnormal furnace conditions and even cause furnace cooling accidents. Therefore, it is necessary to gradually reduce the fuel ratio under the premise of stabilizing various production technical indicators.

[0003] Chinese invention patent application CN113667781A discloses a method for reducing the fuel ratio of a blast furnace. By drawing the Riester operating line, a calculation formula and a relationship curve are obtained, and the furnace condition is adjusted according to the curve. This method requires statistics on operating parameters under various furnace shapes and various working conditions, which is difficult to implement. Moreover, only conclusive indicators such as gas utilization rate can be obtained through the relationship curve, which has no guiding significance for actual production. Another example is Chinese invention patent application CN111748667A, which discloses an ironmaking method for reducing the fuel ratio of the European metallurgical furnace. This patent belongs to the field of molten reduction ironmaking. The charge structure adopts sintered ore: pellet ore = 35%: 65%. The proportion of pellet ore is high, which increases the cost of pig iron and has poor technical and economic indicators. Summary of the invention

[0004] In view of the technical problems that the existing methods for reducing the fuel ratio of blast furnace ironmaking are difficult to implement and are not conducive to the requirements of enterprises for reducing costs and increasing efficiency, the present invention provides a method for reducing the fuel ratio by feeding scrap steel into the furnace. The present invention makes full use of iron-containing raw materials, improves the comprehensive furnace taste, reduces the slag ratio, and gradually improves the gas utilization rate and reduces the water temperature difference on the basis of stabilizing the blast furnace airflow. Finally, the fuel ratio is adjusted according to the empirical formula. Its adjustment range is small, which can effectively reduce the fuel ratio, and is particularly suitable for large blast furnaces with long smelting cycles. In addition, the feeding of scrap steel into the furnace effectively replaces the amount of scrap steel added in the converter process, increases the output of molten iron, and effectively alleviates the pressure of the iron-steel ratio in the subsequent process.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A method for reducing the fuel ratio by feeding scrap steel into a furnace comprises the following steps: after the scrap steel is hot-melted and pressed into blocks, a furnace raw material flattening technology is used to adjust the scrap steel flattening rate, control the delay, add the scrap steel into the center and edge of the blast furnace, and stabilize the two airflows at the center and the edge.

[0007] Further, the method comprises:

[0008] (1) The scrap steel is hot melt briquetting technology, with a melt-clearing water rate of ≥85.0%, S≤0.09%, and a particle size of 10mm≤≤70mm;

[0009] (2) The charge structure is sintered ore: pelletized ore: lump ore: scrap steel = 72%: 13%: 13.58%~13.65%: 1.35%~1.42%;

[0010] (3) The technology of laying out the raw materials into the furnace is adopted, the belt speed under the trough is 2m / s, the laying time is 180 seconds and the laying length is 360m based on sintered ore; the delay time of pelletized ore is 38-40 seconds, the laying time is 68.4-75.6 seconds, and the laying rate is 38%-42%; the delay time of lump ore is 40 seconds, the laying time is 63-81 seconds, and the laying rate is 35%-45%; the delay time of scrap steel is 0 seconds, the laying time is 9-10.8 seconds, and the laying rate is 5%-6%;

[0011] (4) Using a Mineral Distribution Matrix

[0012] (5) Adjust the fuel ratio according to the empirical formula: fuel ratio = coke ratio + coal ratio.

[0013] Coal ratio=M+{(etaCo-eta1Co)*0.3+(etaCo-eta2Co)*0.7}*100*3+{(ΔT-ΔT1)*0.85+(ΔT-ΔT2)*0.15}*2.5,

[0014] Where, M: base coal ratio, average value of three smelting cycles;

[0015] ηCo: benchmark gas utilization, the average value of two smelting cycles;

[0016] η1Co: current gas utilization rate;

[0017] η2Co: Gas utilization rate 1.2 hours ago;

[0018] ΔT: Base water temperature difference, average value of a smelting cycle;

[0019] ΔT1: current water temperature difference;

[0020] ΔT2: Water temperature difference 40 minutes ago.

[0021] Furthermore, the charge structure adopts sintered ore: pelletized ore: lump ore: scrap steel = 72%: 13%: 13.58%: 1.42%.

[0022] Furthermore, the pelletizing delay is 40 seconds and the laying time is 68.5 seconds.

[0023] Furthermore, the block ore delay is 40 seconds and the laying time is 78 seconds.

[0024] Furthermore, scrap steel is added at the head and tail of the material, with the head of the material being distributed for 4 to 5.8 seconds and the tail of the material being distributed for 5 seconds.

[0025] Furthermore, the material feeding time is 5.4 seconds.

[0026] Furthermore, the seven gears of the ore distribution matrix correspond to the distribution chute angles of 42.3°, 40°, 37.5°, 34.5°, 31.5°, 27.5°, and 26° respectively.

[0027] The beneficial effects of the present invention are:

[0028] (1) Traditional methods of stabilizing furnace conditions and reducing fuel ratios mostly use methods such as improving the quality of raw fuels and increasing the proportion of pellets to improve the overall furnace quality. However, the cost of pellets is relatively high, which is not conducive to the requirements of enterprises to reduce costs and increase efficiency. The present invention makes full use of iron-containing waste and adopts scrap steel feeding technology to improve the furnace quality by adding scrap steel, reduce the slag ratio, and ultimately achieve the purpose of reducing the fuel ratio.

[0029] (2) In traditional steel smelting, scrap steel is added in the converter process to increase the output by reducing the iron-steel ratio. However, the addition of scrap steel will cause the converter temperature to drop, resulting in insufficient heat, which is not conducive to the subsequent converter process smelting. In addition, the molten iron splashes during the addition of scrap steel, which can easily cause safety accidents. The present invention adds scrap steel in the blast furnace smelting process, directly mixes the hot-melt briquetting scrap steel into the charge structure, and effectively ensures the heat of the molten iron through the reduction reaction in the furnace, thereby increasing the molten iron output and providing a strong guarantee for the efficient production of the subsequent converter process.

[0030] (3) The charge paving technology adopted by the present invention takes sintered ore as the basis, and adjusts the delay and the material dropping time before the charge enters the furnace to accurately adjust the radial distribution of lump ore, pellets and scrap iron and steel in the furnace, thereby achieving the purpose of improving the utilization rate of coal gas and increasing direct reduction.

[0031] (4) The scrap steel adding position of the present invention is controlled at the head and tail of the material, and high-grade scrap steel is added to the center and the edge, which can clean the dead coke pile in the center, stabilize the two airflows in the center and the edge, and ensure the long-term stable and smooth operation of the blast furnace.

[0032] (5) The present invention provides an empirical formula for fuel ratio, which calculates the benchmark coal ratio, gas utilization rate, and water temperature difference within 1 to 3 smelting cycles. Compared with the Rist curve, it is less difficult to calculate and more operable.

[0033] (6) The present invention has a small daily adjustment range, which can effectively reduce the fuel ratio and is particularly suitable for large blast furnaces with long smelting cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 This is the fuel ratio trend chart for 2021 in Example 1.

[0036] Figure 2 This is a picture of the scrap steel after hot melt briquetting in Example 1. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0038] Example 1

[0039] After July 2021, the scrap steel will be hot melted and briquetted, with a melt-clear water rate of ≥85.0%, S≤0.09%, and a particle size of 10mm≤≤70mm. Then, the raw material flattening technology will be used to adjust the scrap steel flattening rate and control the delay. The scrap steel will be added to the center and edge of the blast furnace to stabilize the two airflows at the center and edge. The specific methods are as follows:

[0040] (1) The charge structure is sintered ore: pelletized ore: lump ore: scrap steel = 72%: 13%: 13.58%: 1.42%;

[0041] (2) The technology of laying out the raw materials into the furnace is adopted, the belt speed under the trough is 2m / s, the laying time is 180 seconds and the laying length is 360m based on sintered ore; the delay of pelletizing is 40 seconds, the laying time is 68.5 seconds and the laying rate is 38%; the delay of lump ore is 40 seconds, the laying time is 78 seconds and the laying rate is 43%; the scrap steel is added at the head and tail of the material, the control delay is 0 seconds, the laying of the head of the material is 5.4 seconds, the laying of the tail of the material is 5 seconds, and the laying rate is 5.8%;

[0042] (3) Adopting a mining matrix The corresponding cloth angles are 42.3°, 40°, 37.5°, 34.5°, 31.5°, 27.5°, and 26°, and the numbers of cloth loops are 4, 3, 3, 3, 3, 3, 2, and 2 respectively;

[0043] (4) Adjust the fuel ratio according to the empirical formula: fuel ratio = coke ratio + coal ratio.

[0044] Coal ratio=M+{(etaCo-eta1Co)*0.3+(etaCo-eta2Co)*0.7}*100*3+{(ΔT-ΔT1)*0.85+(ΔT-ΔT2)*0.15}*2.5,

[0045] Where, M: base coal ratio, average value of three smelting cycles;

[0046] ηCo: benchmark gas utilization, the average value of two smelting cycles;

[0047] η1Co: current gas utilization rate;

[0048] η2Co: Gas utilization rate 1.2 hours ago;

[0049] ΔT: Base water temperature difference, average value of a smelting cycle;

[0050] ΔT1: current water temperature difference;

[0051] ΔT2: Water temperature difference 40 minutes ago.

[0052] Through the above adjustments, the blast furnace fuel ratio will be reduced by an average of 8kg / t after July 2021.

[0053] Example 2

[0054] A method for reducing the fuel ratio by adding scrap steel to a furnace, wherein the scrap steel is hot-melted and pressed into blocks, the melt-cleared water rate is ≥85.0%, S is ≤0.09%, and the particle size is 10 mm ≤70 mm. Then, a furnace raw material flattening technology is adopted to adjust the scrap steel flattening rate, control the delay, add the scrap steel to the center and edge of the blast furnace, and stabilize the two airflows at the center and edge. The specific method is as follows:

[0055] (1) The charge structure is sintered ore: pelletized ore: lump ore: scrap steel = 72%: 13%: 13.65%: 1.35%;

[0056] (2) The technology of laying out the raw materials into the furnace is adopted, the belt speed under the trough is 2m / s, the laying time is 180 seconds and the laying length is 360m based on sintered ore; the delay of pelletizing is 40 seconds, the laying time is 72 seconds, and the laying rate is 40%; the delay of lump ore is 40 seconds, the laying time is 74 seconds, and the laying rate is 41%; the scrap steel is added at the head and tail of the material, the control delay is 0 seconds, the laying of the head of the material is 5.6 seconds, the laying of the tail of the material is 5 seconds, and the laying rate is 5.9%;

[0057] (3) Adopting a mining matrix The corresponding cloth angles are 42.3°, 40°, 37.5°, 34.5°, 31.5°, 27.5°, and 26°, and the numbers of cloth loops are 4, 3, 3, 3, 3, 3, 2, and 2 respectively;

[0058] (4) Adjust the fuel ratio according to the empirical formula: fuel ratio = coke ratio + coal ratio.

[0059] Coal ratio=M+{(etaCo-eta1Co)*0.3+(etaCo-eta2Co)*0.7}*100*3+{(ΔT-ΔT1)*0.85+(ΔT-ΔT2)*0.15}*2.5,

[0060] Where, M: base coal ratio, average value of three smelting cycles;

[0061] ηCo: benchmark gas utilization, the average value of two smelting cycles;

[0062] η1Co: current gas utilization rate;

[0063] η2Co: Gas utilization rate 1.2 hours ago;

[0064] ΔT: Base water temperature difference, average value of a smelting cycle;

[0065] ΔT1: current water temperature difference;

[0066] ΔT2: Water temperature difference 40 minutes ago.

[0067] Although the present invention has been described in detail with reference to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.

Claims

1. A method for reducing the fuel ratio of scrap steel entering a furnace, characterized in that: After the scrap steel is hot-melted and pressed into blocks, the raw material flattening technology is used to adjust the scrap steel flattening rate and control the delay, so that the scrap steel is added to the center and edge of the blast furnace to stabilize the two airflows at the center and edge; Methods include: (1) Scrap steel adopts hot melt briquetting technology, with a melt-clearing water rate of ≥85.0%, S≤0.09%, and a particle size of 10mm≤≤70mm; (2) The charge structure is sintered ore: pellet ore: lump ore: scrap steel = 72%: 13%: 13.58%~13.65%: 1.35%~1.42%; (3) The technology of laying raw materials into the furnace is adopted, the belt speed under the trough is 2m / s, the laying time is 180 seconds and the laying length is 360m based on sintered ore; the delay time of pelletized ore is 38~40 seconds, the laying time is 68.4~75.6 seconds, and the laying rate is 38%~42%; the delay time of lump ore is 40 seconds, the laying time is 63~81 seconds, and the laying rate is 35%~45%; the delay time of scrap steel is 0 seconds, and scrap steel is added at the head and tail of the material. The laying time of the head of the material is 4~5.8 seconds, the laying time of the tail of the material is 5 seconds, and the laying rate is 5%~6%; (4) Using a mining matrix , the seven gears of the ore distribution matrix correspond to the distribution chute angles of 42.3°, 40°, 37.5°, 34.5°, 31.5°, 27.5°, and 26° respectively; (5) Adjust the fuel ratio according to the empirical formula: fuel ratio = coke ratio + coal ratio. Coal ratio = M+{(ηCo-η1Co)*0.3+(ηCo-η2Co)*0.7}*100*3+{(ΔT-ΔT1)*0.85+(ΔT-ΔT2)*0.15}*2.5, Where, M: base coal ratio, average value of three smelting cycles; ηCo: benchmark gas utilization, the average value of two smelting cycles; η1Co: current gas utilization rate; η2Co: Gas utilization rate 1.2 hours ago; ∆T: Base water temperature difference, average value of a smelting cycle; ∆T1: current water temperature difference; ∆T2: Water temperature difference 40 minutes ago.

2. The method according to claim 1, characterized in that The charge structure is sintered ore: pelletized ore: lump ore: scrap steel = 72%: 13%: 13.58%: 1.42%.

3. The method according to claim 1, characterized in that The pelletizing delay is 40 seconds and the laying time is 68.5 seconds.

4. The method according to claim 1, characterized in that The block ore delay is 40 seconds and the laying time is 78 seconds.

5. The method according to claim 1, characterized in that The material is cut and laid in 5.4 seconds.

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