A device and method for increasing the amount of graphite precipitation in molten iron

Abstract

This invention relates to the field of comprehensive resource utilization, specifically to an apparatus and method for increasing the amount of graphite precipitation in molten iron. The apparatus includes a blast furnace molten iron trough, with multiple injection pipes at the bottom. The other end of each injection pipe is connected to a pulverized coal feeding system via a conveying pipe. The method involves injecting pulverized coal into the molten iron trough through the injection pipes to increase the carbon content of the molten iron. As the molten iron cools, it becomes supersaturated with carbon, leading to graphite precipitation. This invention injects pulverized coal into the molten iron trough, utilizing the higher temperature of the molten iron and the stirring kinetic energy generated by the iron flow to promote rapid and efficient dissolution of the pulverized coal, increasing the carbon content. Furthermore, by employing a suitable blast furnace molten iron cooling rate, it significantly improves the subsequent graphite precipitation ratio under the same conditions. The carbon injected into the molten iron in the form of pulverized coal ultimately precipitates as graphite, greatly enhancing the added value of iron and steel metallurgy and resulting in significant economic benefits. It also has a significant impact on the development of emerging graphite resources.

Description

Technical Field

[0001] This invention relates to the field of comprehensive resource utilization, specifically to a device and method for increasing the amount of graphite precipitated from molten iron. Background Technology

[0002] Graphite is a non-metallic mineral resource, and large flake graphite is also produced as a byproduct in my country's iron and steel metallurgical industry. During the production of carbon-containing molten iron in blast furnaces, temperature changes can lead to supersaturation of carbon, causing the precipitation and aggregation of large flake graphite. This aggregated large flake graphite, after collection and purification, possesses properties similar to natural large flake graphite. However, currently, the iron and steel metallurgical industry generally does not consider the issue of graphite precipitation, resulting in a relatively small amount of graphite precipitated from the molten iron and low economic benefits. Summary of the Invention

[0003] To address the technical problem of low graphite precipitation in molten iron in existing technologies, this invention provides an apparatus and method for increasing the amount of graphite precipitation in molten iron. By utilizing the principle that the higher the carbon content of molten iron, the earlier and more graphite precipitates, the higher the graphite recovery rate is improved.

[0004] In a first aspect, the present invention provides an apparatus for increasing the amount of graphite precipitation in molten iron, including a blast furnace molten iron trough, the bottom of which is provided with a plurality of injection pipes, the other end of which is connected to a pulverized coal feeding system via a conveying pipe.

[0005] Furthermore, the pulverized coal feeding system includes a coal bunker, the output of which is connected to a carrier gas source.

[0006] Furthermore, the length direction of the injection pipe is at an acute angle to the length direction of the blast furnace molten iron trough, and the inclination angle of the injection pipe is consistent with the flow direction of the molten iron in the blast furnace molten iron trough; the injection pipe is made of magnesium high-temperature resistant material, the diameter of the injection pipe is 8mm, and the interval between adjacent injection pipes is 1-1.5m.

[0007] Furthermore, the diameter of the conveying pipe is 80-100mm.

[0008] Secondly, the present invention provides a method for increasing the amount of graphite precipitation in molten iron. Using the above-mentioned device, pulverized coal is injected into the molten iron trough at the tapping point of the blast furnace to increase the carbon content of the molten iron. After the molten iron is cooled, the carbon in the molten iron becomes supersaturated, and graphite is precipitated.

[0009] Furthermore, nitrogen is used as the carrier gas to transport pulverized coal; the nitrogen flow rate is 2000-3500 Nm³. 3 / h, pressure is 1.1-1.2MPa.

[0010] Furthermore, the coal powder particle size is 1-2 mm, and the dosage is 1-1.5 kg / min.

[0011] Furthermore, the temperature of the molten iron tapped from the blast furnace during pulverized coal injection is 1520℃.

[0012] Furthermore, after pulverized coal injection, the carbon content of the molten iron is higher than 4.3%.

[0013] Furthermore, the molten iron is cooled by air cooling, or by heat dissipation during transport, with a cooling rate of 0.5-50℃ / min. The amount and size of the precipitated flake graphite are affected by the cooling rate of the molten iron. When the cooling rate is greater than 50℃ / min, the amount of precipitated flake graphite is less and the size is smaller. Conversely, a slower cooling rate results in a larger quantity of precipitated flake graphite with relatively larger sizes. Therefore, a suitable cooling rate (0.5-50℃ / min) is a sufficient condition for the large-scale precipitation of flake graphite.

[0014] The beneficial effects of this invention are as follows:

[0015] This invention involves injecting pulverized coal into a molten iron trough. The higher temperature of the molten iron and the stirring kinetic energy generated by its flow promote the rapid and efficient dissolution of the injected pulverized coal, increasing the carbon content in the molten iron. Furthermore, by employing a suitable blast furnace molten iron cooling rate, the subsequent graphite precipitation ratio is significantly improved under the same conditions. The carbon injected into the molten iron in the form of pulverized coal ultimately precipitates as graphite, greatly enhancing the added value of iron and steel metallurgy and resulting in significant economic benefits. This invention also has a significant impact on the recovery and high-value application of by-products in the iron and steel industry, as well as the development of emerging graphite resources. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic cross-sectional view of the device along the length of the molten iron ditch in Example 1.

[0018] Figure 2 This is a cross-sectional schematic diagram of the device in Example 1.

[0019] In the diagram, 1-Iron trough, 2-Purge pipe. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0021] Example 1

[0022] A device for increasing the amount of graphite precipitation in molten iron includes a blast furnace trough. Multiple injection pipes are installed at the bottom of the blast furnace trough, with the length direction of the injection pipes forming an acute angle with the length direction of the blast furnace trough. The inclination angle of the injection pipes is consistent with the flow direction of the molten iron in the blast furnace trough. The other end of the injection pipes is connected to a pulverized coal feeding system via a conveying pipe. The pulverized coal feeding system includes a coal bunker, and the output end of the coal bunker is connected to a carrier gas source. The conveying pipe has a diameter of 80-100 mm, and the injection pipes are made of magnesium-based high-temperature resistant material with a diameter of 8 mm. The interval between adjacent injection pipes is 1-1.5 m.

[0023] Example 2

[0024] Using the apparatus described in Example 1, pulverized coal was injected into the molten iron trough at the blast furnace tapping point. The blast furnace tapping temperature was 1520℃, the pulverized coal particle size was 1-2mm, the dosage was 1-1.5kg / min, and the nitrogen flow rate was 2000-3500Nm³. 3 The pressure is 1.1-1.2 MPa per hour, which makes the carbon content of the molten iron higher than 4.3%. Then, the molten iron is air-cooled during the transfer and heat dissipation process, and the cooling rate of the molten iron is controlled at 0.5-50℃ / min. The carbon in the molten iron becomes supersaturated and graphite is precipitated.

[0025] Taking a certain steel plant 5100m 3 Taking blast furnace tapping as an example, the pulverized coal injected into the bottom of the molten iron trough has a particle size of 2.0 mm and a dosage of 1.5 kg / min; the nitrogen injection flow rate is 3000 Nm³. 3 / h, pressure of 1.2MPa; conveying pipeline Φ100mm; injection pipeline Φ8mm, adjacent injection pipelines spaced 1m apart; control the molten iron cooling rate at 0.5℃ / min; the graphite content collected in the dust removal flue gas of molten iron pretreatment reached 4.1%, which is 15% higher than that when no pulverized coal was injected, the graphite content in the molten iron desulfurization slag.

[0026] Taking a certain steel plant 3200m 3 Taking blast furnace tapping as an example, the pulverized coal injected into the bottom of the molten iron trough has a particle size of 1.0 mm and a dosage of 1 kg / min; the nitrogen injection flow rate is 2500 Nm³. 3 / h, pressure of 1.1MPa; conveying pipeline Φ80mm; injection pipeline Φ8mm, adjacent injection pipeline interval 1.2m; control the molten iron cooling rate at 0.5℃ / min; the graphite content collected in the dust removal flue gas of molten iron pretreatment reached 3.6%, which is 12% higher than the process without pulverized coal injection in the molten iron desulfurization slag.

[0027] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for increasing the amount of graphite precipitated in molten iron, characterized in that, The above method is implemented using the following apparatus, which includes: a blast furnace molten iron trough, with multiple injection pipes at the bottom of the blast furnace molten iron trough, and the other end of the injection pipes being connected to a pulverized coal feeding system via a conveying pipe. The pulverized coal feeding system includes a coal bunker, and the output end of the coal bunker is connected to a carrier gas source; The length of the injection pipe forms an acute angle with the length of the blast furnace molten iron trough, and the inclination angle of the injection pipe is consistent with the direction of molten iron flow in the blast furnace molten iron trough. The purging pipes are made of magnesium high-temperature resistant material, with a diameter of 8mm and a spacing of 1-1.5m between adjacent purging pipes; The diameter of the conveying pipeline is 80-100mm; The method includes: injecting pulverized coal into the molten iron trough at the tapping point of the blast furnace to increase the carbon content of the molten iron; then cooling the molten iron, causing it to become supersaturated with carbon and precipitate graphite; using nitrogen as the carrier gas to transport the pulverized coal; the nitrogen flow rate is 2000-3500 Nm³. 3 The pressure is 1.1-1.2 MPa; the particle size of the pulverized coal is 1-2 mm, and the dosage is 1-1.5 kg / min; the temperature of the molten iron when the pulverized coal is injected is 1520℃; after the pulverized coal is injected, the carbon content of the molten iron is higher than 4.3%; the cooling method of the molten iron is air cooling, and the cooling rate of the molten iron is 0.5-50℃ / min.

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