Magnesium-carbon gas supply element, preparation method thereof and application of magnesium-carbon gas supply element in steelmaking furnace

Abstract

The invention relates to a magnesium-carbon gas supply element, a preparation method thereof and application of the magnesium-carbon gas supply element in a steel furnace, the magnesium-carbon gas supply element comprises main raw materials, and the main raw materials comprise aggregate and a matrix. The aggregate comprises 58-67 parts of fused magnesite and 5-12 parts of high-iron magnesite based on 100 parts by weight of the magnesia-carbon gas supply element. The aggregate of the magnesia-carbon gas supply element comprises high-iron magnesia, the strong substance diffusion effect of iron ions in periclase crystal lattices under the bottom blowing carbon dioxide atmosphere is utilized, pleonaste is generated through reaction on the surface / interface of fused magnesia, and the problem that the surface / interface of fused magnesia particles is difficult to sinter due to the oxidation reaction of a carbonaceous material is solved; compared with the prior art, the magnesium-carbon gas supply element has the advantages that the high temperature resistance and chemical stability of the magnesium-carbon gas supply element are enhanced, the loss of the magnesium-carbon gas supply element under high-temperature and corrosive atmosphere is reduced, the novel green low-carbon magnesium-carbon gas supply element is prepared, the performance of the magnesium-carbon gas supply element is excellent, and the comprehensive service life of the magnesium-carbon gas supply element is generally longer than that of an existing bottom blowing magnesium-carbon gas supply element.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic non-metallic materials, in particular to the technical field of preparation of magnesia-carbon gas supply elements and regulation of micro-nano structures by in-situ phase reactions of matrices, and specifically relates to a magnesia-carbon gas supply element, a preparation method thereof, and an application thereof in a steelmaking furnace. Background Art

[0002] At present, bottom blowing carbon dioxide in a steelmaking furnace has a low-cost effect that is difficult to compare with bottom blowing inert gases (nitrogen / argon). However, compared with bottom blowing inert gases, the smelting conditions of bottom blowing carbon dioxide are more complex, the metallurgical physical and chemical reactions involved are more intense, and the high-temperature oxidation property can oxidize carbonaceous materials (graphite, resin) and metal anti-oxidants, and the erosion reaction on the bottom blowing magnesia-carbon gas supply element is more serious, resulting in a large attenuation of its service life, which greatly affects the high-efficiency operation of the steelmaking process.

[0003] CN111747733A discloses an Al-MgO-ZrO 2 -C gas supply element for a top and bottom combined blowing process in a steelmaking furnace and a preparation method thereof. Specifically, it discloses that the gas supply element includes the following components in terms of mass percentage: fused magnesia powder 8-14wt%, graphite powder 8-14wt%, metallic aluminum powder 7-10wt%, zirconia powder 2-3wt%, pitch powder 0.5-1.5wt%, binder 2.3-5.5wt%, and the balance is fused magnesia. The provided gas supply element improves the performance of the gas supply element through the synergistic effect between metallic aluminum and zirconia in the raw materials, thereby enhancing the service life of the gas supply element. At the same time, the gas supply element serves in an environment of 1600-1650°C and N 2 / Ar, and this environment can be used for online firing of the gas supply element to prepare non-oxide phases (Al 4 C 3 、Zr(C,N)、(Al 2 OC) 1-x (AlN) x and Zr 2 Al 3 C 5-x (0≤x≤1)) toughening, strengthening, and life extension of a new type of Al-MgO-ZrO 2 -C gas supply element, that is, it discloses a preparation method of a gas supply element that can increase its service life in an N 2 / Ar environment.

[0004] CN111848135A discloses a refractory material, a preparation method thereof, and a gas supply element. Specifically, it discloses that the refractory material is MgAl 2 O 4The phase is a bonding phase of aggregate and matrix. Compared with the existing carbon bonding phase, it does not have decarburization reaction and pores, and has strong antioxidant ability. The air supply element prepared by refractory material is used in the converter double blowing process, which can greatly improve the service life of the air supply element. Moreover, by controlling the carbon content and using aluminum powder to react with magnesium oxide, the pore size and pore structure of the refractory material are improved, and the refractory material obtained has excellent performance. What is disclosed is to increase the service life of the air supply element prepared by refractory material when bottom blowing air.

[0005] In summary, the prior art does not disclose how to improve the service life of the gas supply component when the bottom blowing gas of the steelmaking furnace is carbon dioxide. Therefore, it is necessary to develop a magnesium-carbon gas supply component to optimize the problem of short service life of the magnesium-carbon gas supply component under the bottom blowing and stirring conditions of carbon dioxide weak oxidizing atmosphere. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a magnesium-carbon gas supply element and a preparation method thereof. The present invention optimizes and adjusts the micro-region structure system of aggregate and matrix, utilizes the strong material diffusion effect of iron ions in the periclase lattice under the bottom-blown carbon dioxide atmosphere, the low-temperature sintering characteristics of magnesium-aluminum spinel and magnesia fine powder, and the carbon dioxide and high-activity material source supply characteristics of aluminum-silicon carbide ceramic powder in the initial stage of bottom blowing, and prepares a new green and low-carbon magnesium-carbon gas supply element. The magnesium-carbon gas supply element has excellent performance, and its comprehensive service life is generally higher than that of the existing bottom-blown magnesium-carbon gas supply element.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a magnesium-carbon gas supply element, the magnesium-carbon gas supply element comprising a main raw material, the main raw material comprising an aggregate and a matrix;

[0009] Based on 100 parts by weight of the magnesium-carbon gas supply element, the aggregate includes 58-67 parts of fused magnesia and 5-12 parts of high-iron magnesia.

[0010] The weight proportion of the fused magnesia can be 58 parts, 60 parts, 62 parts, 64 parts, 66 parts or 67 parts, and the weight proportion of the high-iron magnesia can be 5 parts, 7 parts, 10 parts or 12 parts, but are not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0011] The aggregate of the magnesium-carbon gas supply element provided by the present invention includes high-iron magnesia sand, and the iron ions (Fe +2 / Fe +3)The strong material diffusion effect in the periclase lattice generates magnesium ferrite spinel on the surface / interface of fused magnesia, solving the problem of difficult sintering on the surface / interface of fused magnesia particles caused by the oxidation reaction of carbonaceous materials. At the same time, the formation of magnesium ferrite spinel can enhance the high-temperature resistance and chemical stability of the MgC gas supply element, which helps to reduce the loss of the MgC gas supply element in high-temperature and corrosive atmospheres. Secondly, good sintering performance means that the porosity of the MgC gas supply element material decreases and the density increases, thereby improving the strength and durability of the MgC gas supply element. Therefore, the service life of the MgC gas supply element in a bottom-blown carbon dioxide atmosphere can be increased.

[0012] Among them, the fused magnesia used in the present invention is made from magnesite or purified magnesite concentrate powder. After being calcined at about 1000 °C in a shaft kiln or a rotary kiln to obtain light-burned magnesium oxide powder, it is then finely ground, pressed into a blank, and finally melted at high temperature in an electric arc furnace to obtain a refractory material with high purity, high-temperature stability, and chemical stability. Its main component is magnesium oxide (MgO), and the main crystal phase is periclase, which has a high melting point (2800 °C), a large density (greater than 3.40 g / cm 3 ), a low porosity (0 - 10%), a Mohs hardness of 5.5, etc. Periclase often appears as a cube, octahedron, or irregular granular shape, with stable chemical properties and no reaction or weak reaction with various refractory materials except silica bricks at a high temperature of 1500 °C.

[0013] The high-iron magnesia used in the present invention is obtained by adding iron concentrate or iron scale to magnesite and calcining at high temperature. The high-iron magnesia is reddish-brown, dark brown, massive, and its density is usually between 3.58 - 3.61 g / cm 3 After calcination and crushing, granular finished products of 0 - 3 mm or 0 - 5 mm can be obtained. The main chemical components of the high-iron magnesia are magnesium oxide (MgO) and iron oxide (Fe 2 O 3 ).

[0014] As a preferred technical solution of the present invention, the MgC gas supply element further includes auxiliary materials.

[0015] Preferably, the auxiliary material is a binder.

[0016] Preferably, based on 100 parts by weight of the MgC gas supply element, the MgC gas supply element includes 70 - 73 parts of aggregate, 24 - 26 parts of matrix, and 3 - 4 parts of binder. The weight parts of the aggregate can be 70 parts, 71 parts, 72 parts, or 73 parts, the weight parts of the matrix can be 24 parts, 25 parts, or 26 parts, and the parts of the binder can be 3 parts or 4 parts, but are not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0017] As a preferred technical solution of the present invention, the aggregate includes a first aggregate, a second aggregate, and a third aggregate.

[0018] Preferably, the aggregate includes 16-20 parts of the first aggregate, 32-35 parts of the second aggregate, and 20-25 parts of the third aggregate. The weight parts of the first aggregate can be 16 parts, 17 parts, 18 parts, 19 parts, or 20 parts. The weight parts of the second aggregate can be 32 parts, 33 parts, 34 parts, or 35 parts. The weight parts of the third aggregate can be 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, or 25 parts. However, it is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0019] Preferably, the first aggregate includes first fused magnesia and first high-iron magnesia.

[0020] Based on 100 parts by weight of the magnesium-carbon gas supply element, the first aggregate includes 14-18 parts of the first fused magnesia and 1-4 parts of the first high-iron magnesia. The weight parts of the first fused magnesia can be 14 parts, 15 parts, 16 parts, 17 parts, or 18 parts. The weight parts of the first high-iron magnesia can be 1 part, 2 parts, 3 parts, or 4 parts. However, it is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0021] Preferably, the second aggregate includes second fused magnesia and second high-iron magnesia.

[0022] Preferably, the second aggregate includes 25-30 parts of the second fused magnesia and 2-5 parts of the second high-iron magnesia. The weight parts of the second fused magnesia can be 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, or 30 parts. The weight parts of the second high-iron magnesia can be 2 parts, 3 parts, 4 parts, or 5 parts. However, it is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0023] Preferably, the third aggregate includes third fused magnesia and third high-iron magnesia.

[0024] Preferably, the third aggregate includes 17-20 parts of the third fused magnesia and 0-6 parts of the third high-iron magnesia. The weight parts of the third fused magnesia can be 17 parts, 18 parts, 19 parts, or 20 parts. The weight parts of the third high-iron magnesia can be 0 parts, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, or 6 parts. However, it is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0025] As a preferred technical solution of the present invention, the particle size of the first fused magnesia is smaller than that of the second fused magnesia, and the particle size of the second fused magnesia is smaller than that of the third fused magnesia.

[0026] Preferably, the particle size of the first fused magnesia is 4 - 8 mesh. For example, it can be 4 mesh, 5 mesh, 6 mesh, 7 mesh or 8 mesh, but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0027] Preferably, the particle size of the second fused magnesia is 9 - 14 mesh. For example, it can be 9 mesh, 10 mesh, 11 mesh, 12 mesh, 13 mesh or 14 mesh, but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0028] Preferably, the particle size of the third fused magnesia is 15 - 65 mesh. For example, it can be 15 mesh, 20 mesh, 30 mesh, 40 mesh, 50 mesh or 65 mesh, but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0029] In the preparation process of the aggregate of the present invention, fused magnesia with different particle sizes is selected. Among them, the fused magnesia with a small particle size can fill the gaps between the particles of the fused magnesia with a large particle size, thereby increasing the bulk density of the aggregate, which helps to improve the strength and density of the magnesia-carbon gas supply element, enabling it to better withstand harsh conditions such as high temperature and slag erosion during use; at the same time, by limiting the proportions of the fused magnesia with different particle sizes, the optimization of particle gradation can be achieved. A reasonable particle gradation can reduce the porosity of the material, increase the density and strength of the material. Further, the optimized particle gradation can also improve the erosion resistance and erosion resistance of the material, and extend the service life of the magnesia-carbon gas supply element.

[0030] Preferably, the particle size of the first high-iron magnesia is smaller than that of the second high-iron magnesia, and the particle size of the second high-iron magnesia is smaller than that of the third high-iron magnesia.

[0031] Preferably, the particle size of the first high-iron magnesia is 4 - 8 mesh. For example, it can be 4 mesh, 5 mesh, 6 mesh, 7 mesh or 8 mesh, but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0032] Preferably, the particle size of the second high-iron magnesia is 9 - 14 mesh. For example, it can be 9 mesh, 10 mesh, 11 mesh, 12 mesh, 13 mesh or 14 mesh, but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0033] Preferably, the particle size of the third high-iron magnesia is 15 - 65 mesh. For example, it can be 15 mesh, 20 mesh, 25 mesh, 35 mesh, 45 mesh, 55 mesh or 65 mesh, but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0034] In the preparation process of the aggregate of the present invention, high-iron magnesia sands with different particle sizes are selected. The small-particle-size high-iron magnesia sand can fill the gaps between the large-particle-size high-iron magnesia sand particles, which can also increase the bulk density of the aggregate, improve the strength and density of the magnesia-carbon gas supply element, and enable it to better withstand harsh conditions such as high temperature and slag erosion during use. At the same time, by limiting the number of parts of high-iron magnesia sands with different particle sizes, the optimization of particle grading can be achieved. A reasonable particle grading can reduce the porosity of the material, improve the density and strength of the material. Further, the aggregate is prepared together with fused magnesia sands with different particle sizes and different numbers of parts. The optimized particle grading can also improve the erosion resistance and scouring resistance of the aggregate, and extend the service life of the magnesia-carbon gas supply element.

[0035] As a preferred technical solution of the present invention, the mass percentage content of magnesium oxide in the first fused magnesia sand, the second fused magnesia sand, and the third fused magnesia sand is independently ≥97.2%, for example, it can be 97.2%, 98%, 98.5%, 99%, or 99.5%, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0036] Preferably, the mass percentage content of magnesium oxide in the first high-iron magnesia sand, the second high-iron magnesia sand, and the third high-iron magnesia sand is independently ≥94%, for example, it can be 94%, 94.2%, 94.4%, 94.6%, 94.8%, or 95%, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0037] Preferably, the mass percentage content of iron oxide in the first high-iron magnesia sand, the second high-iron magnesia sand, and the third high-iron magnesia sand is independently ≥5%, for example, it can be 5%, 5.2%, 5.4%, 5.6%, 5.8%, or 6%, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0038] Preferably, based on 100 parts by weight of the magnesia-carbon gas supply element, the matrix includes 4-5 parts of modified magnesia powder, 7-8 parts of graphite, and 8-10 parts of granulating powder, and the balance is fused magnesia powder. The number of parts by weight of the modified magnesia powder can be 4 parts, 4.2 parts, 4.4 parts, 4.6 parts, 4.8 parts, or 5 parts. The number of parts by weight of the graphite can be 7 parts, 7.2 parts, 7.4 parts, 7.6 parts, 7.8 parts, or 8 parts. The number of parts by weight of the granulating powder can be 8 parts, 8.5 parts, 9 parts, 9.5 parts, or 10 parts, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0039] Among them, the modified magnesia powder is obtained by calcining alumina powder and magnesia powder at a temperature above 1200 °C, and the content is w(Al 2 O 3)≥4%, w(MgO)≥94%.

[0040] Utilize the low-temperature sintering characteristics (around 1100 °C) of magnesia-aluminum spinel and modified magnesite powder to solve the problem that it is difficult to sinter magnesite aggregate and matrix from the non-working layer to the working layer of the magnesia-carbon gas supply element under the bottom-blowing ambient temperature, and improve the sintering strength and slag penetration resistance after oxidation of the working layer.

[0041] Preferably, the mass percentage content of alumina in the modified magnesite powder ≥4%, for example, it can be 4%, 4.5%, 5%, 5.5% or 6%, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0042] Preferably, the mass percentage content of magnesia in the modified magnesite powder ≥94%, for example, it can be 94%, 94.5%, 95%, 95.5% or 96%, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0043] Preferably, the particle size of the modified magnesite powder is 70μm ≤ D50 ≤ 100μm, for example, it can be 70μm, 75μm, 80μm, 85μm, 90μm, 95μm or 100μm, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0044] Preferably, the mass percentage content of carbon in the graphite ≥97.5%, for example, it can be 97.5%, 98%, 98.5%, 99% or 99.5%, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0045] Preferably, the particle size of the graphite is 90μm ≤ D50 ≤ 120μm, for example, it can be 90μm, 95μm, 100μm, 105μm, 110μm, 115μm or 120μm, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0046] As a preferred technical solution of the present invention, the granulating powder includes aluminum silicon carbide ceramic powder and micro-nano titanium oxide ceramic powder.

[0047] The present invention selects aluminum silicon carbide ceramic powder and micro-nano titanium oxide ceramic powder as the granulating powder. On the one hand, metallic aluminum and elemental silicon in the aluminum silicon carbide ceramic powder can capture carbon dioxide in the initial stage of bottom blowing, generate carbon, alumina and silica, and react with titanium in the later stage to generate a titanium-mullite matrix strengthening phase, avoiding the adverse generation of a large amount of liquid phase when using a single metallic aluminum or elemental silicon as the raw material; on the other hand, the aluminum silicon carbide ceramic powder can provide Si x O y (g) and Alx O y (g) A highly active substance source that continuously diffuses and mass-transfers from the low-temperature region in the magnesia-carbon gas supply element to the working end of the magnesia-carbon gas supply element, where physical vapor deposition reactions and chemical vapor deposition reactions occur under the action of high-alumina magnesia, generating low-dimensional morphology (one-dimensional and two-dimensional) non-oxides and oxides substances in addition to the conventional morphology, reconstructing the phase composition and micro-region structure of the aggregate and matrix, strengthening the pore structure between the aggregate and matrix, enhancing the bonding performance between the matrix and aggregate, matrix and matrix, and aggregate and aggregate in the magnesia-carbon gas supply element, and weakening the adverse effects such as the decrease in bulk density and the attenuation of slag erosion resistance caused by the oxidation reaction of carbonaceous materials.

[0048] Preferably, the particle size of the granulated powder is 200μm ≤ D50 ≤ 500μm. For example, it can be 200μm, 250μm, 300μm, 350μm, 400μm, 450μm or 500μm, but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0049] Preferably, based on 100 parts by weight of the granulated powder, the granulated powder includes 95 - 97 parts of aluminum silicon carbide ceramic powder and 3 - 5 parts of micro-nano titanium oxide ceramic powder. The weight parts of the aluminum silicon carbide ceramic powder can be 95 parts, 95.5 parts, 96 parts, 96.5 parts or 97 parts, and the weight parts of the micro-nano titanium oxide ceramic powder can be 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts, but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0050] Preferably, the aluminum silicon carbide ceramic powder includes 15 - 25 parts of silicon carbide, 65 - 79 parts of aluminum and 6 - 10 parts of silicon. The weight parts of the silicon carbide can be 15 parts, 17 parts, 19 parts, 20 parts, 21 parts, 23 parts or 25 parts, the weight parts of the aluminum can be 65 parts, 70 parts, 75 parts or 79 parts, and the weight parts of the silicon can be 6 parts, 7 parts, 8 parts, 9 parts or 10 parts, but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0051] Preferably, the particle size of the aluminum silicon carbide ceramic powder is 80μm ≤ D50 ≤ 100μm. For example, it can be 80μm, 85μm, 90μm, 95μm or 100μm, but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0052] Preferably, the mass percentage content of titanium dioxide in the micro-nano titanium oxide ceramic powder ≥ 99%. For example, it can be 99%, 99.2%, 99.4%, 99.6% or 99.8%, but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0053] Preferably, the particle size of the micro-nano titanium oxide ceramic powder is 0.5μm ≤ D50 ≤ 1.5μm. For example, it can be 0.5μm, 0.7μm, 0.9μm, 1.0μm, 1.1μm, 1.3μm or 1.5μm, but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0054] Preferably, the mass percentage content of magnesium oxide in the fused magnesite powder is ≥ 97.2%. For example, it can be 97.2%, 97.5%, 98%, 98.5%, 99% or 99.5%, but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0055] Preferably, the particle size of the fused magnesite powder is 70μm ≤ D50 ≤ 100μm. For example, it can be 70μm, 75μm, 80μm, 85μm, 90μm, 95μm or 100μm, but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0056] Preferably, the binder includes liquid thermosetting phenolic resin.

[0057] Preferably, the residual carbon rate of the liquid thermosetting phenolic resin is ≥ 42%. For example, it can be 42%, 45%, 50%, 55% or 60%, but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0058] In the second aspect, the present invention provides a preparation method of the magnesia-carbon gas supply element described in the first aspect. The preparation method includes the following steps:

[0059] Mix the matrix and the aggregate containing fused magnesite and high-iron magnesite, and the obtained product after mixing is successively subjected to aging, shaping and heat treatment to obtain the magnesia-carbon gas supply element.

[0060] The magnesia-carbon gas supply element provided by the present invention is green, low-carbon and has a long on-line service life; compared with the magnesia-carbon gas supply element used in the traditional bottom blowing process, this magnesia-carbon gas supply element has the advantages of carbon capture in the initial stage of bottom blowing carbon dioxide, synergistic strengthening of multi-oxide-magnesia between the surface / interface of the modified magnesia aggregate, and multi-dimensional structure composite strengthening of metal-oxide-non-oxide within the micro-nano scale between the modified matrices. It also has the characteristics of strong antioxidant ability during high-temperature service of the working-end refractory gas supply element, small decay of oxidation physical properties, and high bonding strength between aggregate and aggregate, aggregate and matrix, and matrix and matrix.

[0061] As a preferred technical solution of the present invention, the step of mixing the matrix and the aggregate containing fused magnesite and high-iron magnesite includes:

[0062] (1) Mix fused magnesia and high-iron magnesia, and conduct the first sub-mixing to obtain the aggregate; add a binder to the aggregate and conduct the second sub-mixing to obtain an intermediate aggregate product;

[0063] (2) Mix modified magnesia powder, graphite, granulating powder and fused magnesia powder, and conduct the third sub-mixing to obtain the matrix;

[0064] (3) Mix the intermediate aggregate product obtained in step (1) and the matrix obtained in step (2), and then conduct the fourth sub-mixing to obtain the post-mixing product;

[0065] There is no order preference between step (1) and step (2).

[0066] Preferably, the preparation method further includes: after mixing aluminum silicon carbide ceramic powder, micro-nano titanium oxide ceramic powder and a solvent, conducting mixing and rotary granulation in sequence, and after baking and screening, obtaining the granulating powder with a particle size of 200μm ≤ D50 ≤ 500μm. The mixing time is 0.5 - 1 min, for example, it can be 0.5 min, 0.6 min, 0.7 min, 0.8 min, 0.9 min or 1 min. The mixing temperature is 20 - 35 °C, for example, it can be 20 °C, 25 °C, 30 °C or 35 °C. The rotary granulation time is 2 - 3 min, for example, it can be 2 min, 2.2 min, 2.4 min, 2.6 min, 2.8 min or 3 min. The rotary speed of the rotary granulation is ≥ 3500 r / min, for example, it can be 3500 r / min, 4000 r / min, 4500 r / min or 5000 r / min. The particle size of the granulating powder can be 200μm, 250μm, 300μm, 350μm, 400μm, 450μm or 500μm, but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0067] Preferably, the solvent includes any one or a combination of at least two of polyvinyl alcohol, carboxymethyl cellulose or starch. Typical but non-limiting combinations include: the combination of polyvinyl alcohol and carboxymethyl cellulose, the combination of polyvinyl alcohol and starch, the combination of carboxymethyl cellulose and starch, and the combination of polyvinyl alcohol, carboxymethyl cellulose and starch.

[0068] Preferably, the volume concentration of the solvent is 30 - 40%, for example, it can be 30%, 32%, 34%, 36%, 38% or 40%, but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0069] Preferably, the mass ratio of the aluminum silicon carbide ceramic powder, the micro-nano titanium oxide ceramic powder, and the solvent is (95 - 97):(3 - 5):(7 - 9). For example, it can be 95:3:7, 96:4:7, 96:3:8, 96:5:9, or 97:5:9, but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0070] Preferably, the temperatures of the first sub-mixing, the second sub-mixing, the third sub-mixing, and the fourth sub-mixing are each independently 45 - 55°C. For example, it can be 45°C, 47°C, 49°C, 51°C, 53°C, or 55°C, but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0071] Preferably, the time of the first sub-mixing is 8 - 10 min. For example, it can be 8 min, 8.5 min, 9 min, 9.5 min, or 10 min, but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0072] Preferably, the time of the second sub-mixing is 10 - 15 min. For example, it can be 10 min, 11 min, 12 min, 13 min, 14 min, or 15 min, but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0073] Preferably, the time of the third sub-mixing is 10 - 15 min. For example, it can be 10 min, 11 min, 12 min, 13 min, 14 min, or 15 min, but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0074] Preferably, the time of the fourth sub-mixing is 30 - 40 min. For example, it can be 30 min, 32 min, 34 min, 36 min, 38 min, or 40 min, but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0075] Preferably, the temperature of the aging is 25 - 35°C. For example, it can be 25°C, 27°C, 29°C, 30°C, 31°C, 33°C, or 35°C, but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0076] Preferably, the humidity of the aging is 35 - 45%. For example, it can be 35%, 37%, 39%, 40%, 41%, 43%, or 45%, but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0077] Preferably, the aging time is 24 - 36 h, for example, it can be 24 h, 26 h, 28 h, 30 h, 32 h, 34 h or 36 h, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0078] Preferably, the forming method includes isostatic pressing or mechanical pressing.

[0079] Preferably, the forming pressure is 120 - 150 MPa, for example, it can be 120 MPa, 130 MPa, 140 MPa or 150 MPa, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0080] Preferably, the heat treatment temperature is 190 - 210 °C, for example, it can be 190 °C, 195 °C, 200 °C, 205 °C or 210 °C, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0081] Preferably, the heat treatment holding time is 30 - 36 h, for example, it can be 30 h, 32 h, 34 h or 36 h, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0082] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0083] (1) Mix the fused magnesia and the high - iron magnesia, and knead at 45 - 55 °C for 8 - 10 min to obtain the aggregate; add a binder to the aggregate and knead at 45 - 55 °C for 10 - 15 min to obtain the intermediate aggregate.

[0084] (2) After mixing the aluminum silicon carbide ceramic powder, the micro - nano titanium oxide ceramic powder and the solvent, knead and perform rotary granulation in sequence, and obtain granulated powder with a particle size of 200 μm ≤ D50 ≤ 500 μm after baking and screening; mix the modified magnesia powder, graphite, granulated powder and fused magnesia powder, and knead at 45 - 55 °C for 10 - 15 min to obtain the matrix.

[0085] (3) Mix the intermediate aggregate obtained in step (1) and the matrix obtained in step (2), and knead at 45 - 55 °C for 30 - 40 min. The kneaded product is aged, formed and heat - treated in sequence to obtain the magnesia - carbon gas supply element.

[0086] In the third aspect, the present invention provides an application of the magnesia - carbon gas supply element described in the first aspect in a steelmaking furnace.

[0087] Compared with bottom-blown inert gas, the smelting conditions of bottom-blown carbon dioxide in the steelmaking furnace are more complex, and the involved metallurgical physical and chemical reactions are more intense. The high-temperature oxidizing property can oxidize carbonaceous materials (graphite, resin) and metal anti-oxidants, and the erosion reaction on the bottom-blown magnesia-carbon gas supply element is more serious, resulting in a significant attenuation of its service life, which greatly affects the high-efficiency operation of the steelmaking process. The magnesia-carbon gas supply element provided by the present invention is green and low-carbon, and can still have a good on-line service life under the smelting conditions of bottom-blown carbon dioxide in the steelmaking furnace.

[0088] Compared with the prior art, the present invention has at least the following beneficial effects:

[0089] The aggregate of the magnesia-carbon gas supply element provided by the present invention includes high-iron magnesia sand. Utilizing the strong mass diffusion effect of iron ions in the periclase lattice under the atmosphere of bottom-blown carbon dioxide, magnesium ferrite spinel is generated on the surface / interface of the fused magnesia, solving the problem of difficult sintering on the surface / interface of the fused magnesia particles caused by the oxidation reaction of carbonaceous materials; at the same time, the formation of magnesium ferrite spinel can enhance the high-temperature resistance and chemical stability of the magnesia-carbon gas supply element, reducing the loss of the magnesia-carbon gas supply element under high temperature and corrosive atmosphere. The performance of the magnesia-carbon gas supply element prepared by the present invention meets: 2.98 g / cm 3 ≤ bulk density ≤ 3.10 g / cm 3 , 3% ≤ apparent porosity ≤ 5%, 40 MPa ≤ normal temperature compressive strength ≤ 48 MPa, 8.0 MPa ≤ high-temperature flexural strength ≤ 14 MPa. The erosion rate of the magnesia-carbon gas supply element prepared by the present invention can be controlled within 0.1 - 0.2 mm / furnace, and its campaign life can reach 2100 - 2300. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Figure 1 is the SEM image of the one-dimensional non-oxide of the magnesia-carbon gas supply element prepared in Example 1 of the present invention.

[0091] Figure 2 is the SEM image of the two-dimensional non-oxide of the magnesia-carbon gas supply element prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0092] The technical solutions of the present invention will be further described below with reference to the drawings and specific embodiments. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the protection of the present invention. The scope of protection of the present invention is subject to the claims.

[0093] Example 1

[0094] This embodiment provides a magnesia-carbon gas supply element. Based on 100 parts by weight of the magnesia-carbon gas supply element, the magnesia-carbon gas supply element includes 70 parts of aggregate, 26 parts of matrix, and 4 parts of binder. Among them, the aggregate includes 18 parts of the first aggregate, 32 parts of the second aggregate, and 20 parts of the third aggregate. The first aggregate includes 16 parts of the first fused magnesia with a particle size of 6 mesh and a magnesia mass percentage of 98%, and 2 parts of the first high-iron magnesia with a particle size of 5 mesh, a magnesia mass percentage of 94.5%, and an iron oxide mass percentage of 5.4%. The second aggregate includes 27 parts of the second fused magnesia with a particle size of 12 mesh and a magnesia mass percentage of 99%, and 5 parts of the second high-iron magnesia with a particle size of 13 mesh, a magnesia mass percentage of 94%, and an iron oxide mass percentage of 6%. The third aggregate includes 19 parts of the third fused magnesia with a particle size of 50 mesh and a magnesia mass percentage of 97.2%, and 1 part of the third high-iron magnesia with a particle size of 40 mesh, a magnesia mass percentage of 94.6%, and an iron oxide mass percentage of 5.2%. The matrix includes 4.5 parts of modified magnesia powder with a particle size of 90 μm, an alumina mass percentage of 5%, and a magnesia mass percentage of 95%, 7.5 parts of graphite with a particle size of 100 μm and a carbon mass percentage of 98%, 9 parts of granulating powder with a particle size of 300 μm, and 5 parts of fused magnesia powder with a particle size of 80 μm and a magnesia mass percentage of 98%. Based on 100 parts by weight of the granulating powder, the granulating powder includes 96 parts of aluminum silicon carbide ceramic powder with a particle size of 90 μm and 4 parts of micro-nano titanium oxide ceramic powder with a particle size of 1 μm and a titanium dioxide mass percentage of 99.6%. The aluminum silicon carbide ceramic powder includes 25 parts of silicon carbide, 65 parts of aluminum, and 10 parts of silicon. The binder is a liquid thermosetting phenolic resin (grade PF-5325) with a residual carbon rate of not less than 42%.

[0095] This embodiment also provides a preparation method of the magnesia-carbon gas supply element. The preparation method includes the following steps:

[0096] (1) Mix the fused magnesia and the high-iron magnesia, and knead them at 50 °C for 9 min to obtain the aggregate; add the liquid thermosetting phenolic resin to the aggregate, and knead them at 48 °C for 12 min to obtain an intermediate aggregate;

[0097] (2) After mixing the aluminum silicon carbide ceramic powder, the micro-nano titanium oxide ceramic powder, and polyvinyl alcohol (grade MQ-35), knead them at 25 °C for 0.6 min, then perform rotary granulation at a rotation speed of 4000 r / min for 2.5 min, and obtain granulating powder with a particle size of 300 μm after baking and screening; mix the modified magnesia powder, graphite, granulating powder, and fused magnesia powder, and knead them at 52 °C for 13 min to obtain the matrix;

[0098] (3) Mix the aggregate intermediate obtained in step (1) and the matrix obtained in step (2), and knead them at 50 °C for 35 min. The kneaded product is aged for 30 h under the conditions of a temperature of 30 °C and a humidity of 40%, then isopressed at 130 MPa, and then heat-treated at 200 °C for 32 h to obtain the magnesium-carbon gas supply element; and test the morphologies of the one-dimensional non-oxides and two-dimensional non-oxides of the magnesium-carbon gas supply element, as Figure 1 and Figure 2 shown;

[0099] There is no order of priority between step (1) and step (2).

[0100] Example 2

[0101] This example provides a magnesium-carbon gas supply element. Based on 100 parts by weight of the magnesium-carbon gas supply element, the magnesium-carbon gas supply element includes 72 parts of aggregate, 25 parts of matrix, and 3 parts of binder. Among them, the aggregate includes 18 parts of the first aggregate, 34 parts of the second aggregate, and 20 parts of the third aggregate. The first aggregate includes 17 parts of the first fused magnesia with a particle size of 4 mesh and a magnesium oxide mass percentage of 97.2% and 1 part of the first high-iron magnesia with a particle size of 8 mesh, a magnesium oxide mass percentage of 94%, and an iron oxide mass percentage of 6%. The second aggregate includes 30 parts of the second fused magnesia with a particle size of 14 mesh and a magnesium oxide mass percentage of 98% and 4 parts of the second high-iron magnesia with a particle size of 9 mesh, a magnesium oxide mass percentage of 94.5%, and an iron oxide mass percentage of 5.4%. The third aggregate includes 17 parts of the third fused magnesia with a particle size of 15 mesh and a magnesium oxide mass percentage of 97.2% and 3 parts of the third high-iron magnesia with a particle size of 65 mesh, a magnesium oxide mass percentage of 94%, and an iron oxide mass percentage of 6%. The matrix includes 4 parts of modified magnesia powder with a particle size of 70 μm, an alumina mass percentage of 4%, and a magnesium oxide mass percentage of 96%, 8 parts of graphite with a particle size of 90 μm and a carbon mass percentage of 97.5%, 8 parts of granulating powder with a particle size of 200 μm, and 5 parts of fused magnesia powder with a particle size of 70 μm and a magnesium oxide mass percentage of 97.2%. Based on 100 parts by weight of the granulating powder, the granulating powder includes 97 parts of aluminum silicon carbide ceramic powder with a particle size of 100 μm and 3 parts of micro-nano titanium oxide ceramic powder with a particle size of 0.5 μm and a titanium dioxide mass percentage of 99%. The aluminum silicon carbide ceramic powder in the granulating powder includes 20 parts of silicon carbide, 70 parts of aluminum, and 10 parts of silicon. The binder is a liquid thermosetting phenolic resin (grade PF-5325) with a residual carbon rate of not less than 42%.

[0102] This example also provides a preparation method of the magnesium-carbon gas supply element. The preparation method includes the following steps:

[0103] (1) Mix the fused magnesia and the high-iron magnesia, and knead them at 45 °C for 10 min to obtain the aggregate; add liquid thermosetting phenolic resin to the aggregate and knead it at 55 °C for 10 min to obtain the intermediate aggregate;

[0104] (2) After mixing aluminum silicon carbide ceramic powder, micro-nano titanium oxide ceramic powder and carboxymethyl cellulose (Sinopharm carboxymethyl cellulose 300 - 800), knead them at 35 °C for 0.5 min, then perform rotary granulation at a rotation speed of 3500 r / min for 3 min, and obtain granulated powder with a particle size of 200 μm after baking and screening; mix modified magnesia powder, graphite, granulated powder and fused magnesia powder, and knead them at 45 °C for 10 min to obtain the matrix;

[0105] (3) Mix the intermediate aggregate obtained in step (1) and the matrix obtained in step (2), and knead them at 55 °C for 30 min. The kneaded product is aged at a temperature of 25 °C and a humidity of 35% for 36 h, then molded by mechanical pressing at 150 MPa, and then heat-treated at 190 °C for 36 h to obtain the magnesia-carbon gas supply element;

[0106] There is no order of precedence between step (1) and step (2).

[0107] Example 3

[0108] This embodiment provides a magnesia-carbon gas supply element. Based on 100 parts by weight of the magnesia-carbon gas supply element, the magnesia-carbon gas supply element includes 72 parts of aggregate, 24 parts of matrix, and 4 parts of binder. Among them, the aggregate includes 20 parts of first aggregate, 32 parts of second aggregate, and 20 parts of third aggregate. The first aggregate includes 17 parts of first fused magnesia with a particle size of 8 mesh and a magnesia mass percentage of 99.5%, and 3 parts of first high-iron magnesia with a particle size of 4 mesh, a magnesia mass percentage of 95%, and an iron oxide mass percentage of 5%. The second aggregate includes 28 parts of second fused magnesia with a particle size of 9 mesh and a magnesia mass percentage of 99%, and 4 parts of second high-iron magnesia with a particle size of 14 mesh, a magnesia mass percentage of 94%, and an iron oxide mass percentage of 6%. The third aggregate includes 18 parts of third fused magnesia with a particle size of 65 mesh and a magnesia mass percentage of 98%, and 2 parts of third high-iron magnesia with a particle size of 15 mesh, a magnesia mass percentage of 94.5%, and an iron oxide mass percentage of 5.5%. The matrix includes 5 parts of modified magnesia powder with a particle size of 100 μm, an alumina mass percentage of 6%, and a magnesia mass percentage of 94%, 7 parts of graphite with a particle size of 120 μm and a carbon mass percentage of 99.5%, 8 parts of granulating powder with a particle size of 500 μm, and 4 parts of fused magnesia powder with a particle size of 100 μm and a magnesia mass percentage of 99.5%. Based on 100 parts by weight of the granulating powder, the granulating powder includes 95 parts of aluminum silicon carbide ceramic powder with a particle size of 80 μm and 5 parts of micro-nano titanium oxide ceramic powder with a particle size of 1.5 μm and a titanium dioxide mass percentage ≥99.8%. The aluminum silicon carbide ceramic powder in the granulating powder includes 20 parts of silicon carbide, 70 parts of aluminum, and 10 parts of silicon. The binder is a liquid thermosetting phenolic resin (grade PF-5325) with a residual carbon rate of not less than 42%.

[0109] This embodiment also provides a preparation method of the magnesia-carbon gas supply element. The preparation method includes the following steps:

[0110] (1) Mix the fused magnesia and the high-iron magnesia, and knead at 55 °C for 8 min to obtain the aggregate; add the liquid thermosetting phenolic resin to the aggregate, and knead at 45 °C for 15 min to obtain an intermediate of the aggregate;

[0111] (2) After mixing the aluminum silicon carbide ceramic powder, the micro-nano titanium oxide ceramic powder, and starch (Zhonglian reagent, soluble starch), knead at 30 °C for 1 min, then perform rotary granulation at a rotation speed of 5000 r / min for 2 min, and obtain granulating powder with a particle size of 500 μm after baking and screening; mix the modified magnesia powder, graphite, granulating powder, and fused magnesia powder, and knead at 55 °C for 15 min to obtain the matrix;

[0112] (3) Mix the aggregate intermediate obtained in step (1) and the matrix obtained in step (2), and knead them at 45°C for 40 min. The kneaded product is aged for 24 h under the conditions of a temperature of 35°C and a humidity of 45%, then press-molded at 120 MPa, and then heat-treated at 210°C for 30 h to obtain the magnesium-carbon gas supply element;

[0113] There is no sequence distinction between step (1) and step (2).

[0114] Example 4

[0115] This example provides a magnesium-carbon gas supply element. The difference from Example 1 is that, except that the particle size of the second fused magnesia is 6 mesh, the others are the same as those in Example 1.

[0116] Example 5

[0117] This example provides a magnesium-carbon gas supply element. The difference from Example 1 is that, except that the particle size of the second high-iron magnesia is 5 mesh, the others are the same as those in Example 1.

[0118] Example 6

[0119] This example provides a magnesium-carbon gas supply element. The difference from Example 1 is that, except that the first aggregate only includes 18 parts of high-iron magnesia, the others are the same as those in Example 1.

[0120] Example 7

[0121] This example provides a magnesium-carbon gas supply element. The difference from Example 1 is that, except that the second aggregate only includes 32 parts of fused magnesia, the others are the same as those in Example 1.

[0122] Example 8

[0123] This example provides a magnesium-carbon gas supply element. The difference from Example 1 is that, except that the aluminum silicon carbide ceramic powder in the granulation powder is replaced with metallic aluminum powder, the others are the same as those in Example 1.

[0124] Example 9

[0125] This example provides a magnesium-carbon gas supply element. The difference from Example 1 is that, except that the aluminum silicon carbide ceramic powder in the granulation powder is replaced with elemental silicon powder, the others are the same as those in Example 1.

[0126] Comparative Example 1

[0127] This comparative example provides a magnesium-carbon gas supply element. The difference from Example 1 is that, except that the aggregate only contains fused magnesia, the others are the same as those in Example 1.

[0128] Comparative Example 2

[0129] This comparative example provides a magnesia-carbon gas supply element, which is only different from Example 1 in that, except that the aggregate includes 40 parts of fused magnesia and 30 parts of high-iron magnesia, the rest are the same as those in Example 1.

[0130] Comparative Example 3

[0131] This comparative example provides a magnesia-carbon gas supply element, which is only different from Example 1 in that, except that the aggregate includes 69 parts of fused magnesia and 1 part of high-iron magnesia, the rest are the same as those in Example 1.

[0132] Comparative Example 4

[0133] This comparative example provides a commercial magnesia-carbon gas supply element (MT-12).

[0134] The bulk density of the prepared magnesia-carbon gas supply element was tested by the Archimedes method (hydrostatic weighing method); the apparent porosity of the prepared magnesia-carbon gas supply element was tested by the immersion method; the normal temperature compressive strength of the prepared magnesia-carbon gas supply element was tested using a microcomputer-controlled electro-hydraulic servo pressure testing machine. The magnesia-carbon gas supply element was placed in the heating furnace of a high-temperature flexural strength testing machine, heated to 1400 °C, and held for 0.5 h. The heated magnesia-carbon gas supply element was placed on the lower knife edge of the bending device to ensure good contact between the magnesia-carbon gas supply element and the knife edge. Adjust the position of the upper knife edge so that it is located in the middle of the pressure surface of the magnesia-carbon gas supply element and perpendicular to the magnesia-carbon gas supply element. Apply a tensile stress to the magnesia-carbon gas supply element, record the maximum load at the moment when the magnesia-carbon gas supply element breaks, and calculate the high-temperature flexural strength R = F / (L×b×d 2 ), where F is the maximum load (N) at the moment when the magnesia-carbon gas supply element breaks, L is the distance between the lower knife edges (mm), b is the width (mm) of the magnesia-carbon gas supply element, and d is the height (mm) of the magnesia-carbon gas supply element; the erosion rate test of the magnesia-carbon gas supply element specimen was carried out using the test method for slag resistance of refractories GB 8931-1988, and the service lives of Examples 1-9 and Comparative Examples 1-3 were calculated based on the service life and erosion rate of MT-12.

[0135] According to the above test methods and calculation formulas, the bulk density, apparent porosity, normal temperature compressive strength, high-temperature flexural strength, erosion rate and campaign life of the magnesia-carbon gas supply element were obtained. The test results are shown in Table 1.

[0136] Table 1

[0137]

[0138] It can be seen from the test results that:

[0139] (1) As can be seen from Examples 1 to 3, by optimizing and adjusting the microstructural system of the aggregate and matrix, and utilizing the strong mass diffusion effect of iron ions in the periclase lattice under the bottom-blown carbon dioxide atmosphere, the low-temperature sintering characteristics of magnesia-aluminum spinel and magnesite fine powder, as well as the characteristics of aluminum silicon carbide ceramic powder to capture carbon dioxide and high-activity substance sources at the initial stage of bottom blowing, the technical effect of improving the service life of the gas supply element can be achieved.

[0140] (2) As can be seen from Example 1 and Examples 4-7, in the aggregate of the magnesia-carbon gas supply element in Example 1, three different particle sizes and different amounts of fused magnesia and three different particle sizes and different amounts of high-iron magnesia are used. The prepared magnesia-carbon gas supply element has a room-temperature compressive strength of 41 MPa, a high-temperature flexural strength of 8.8 MPa, an erosion rate of 0.18 mm / furnace campaign, and a campaign life of 2255. Compared with Example 1, in the aggregate of the magnesia-carbon gas supply element in Example 4, there are only two different particle sizes of fused magnesia. The prepared magnesia-carbon gas supply element has a room-temperature compressive strength of 39 MPa, a high-temperature flexural strength of 7.8 MPa, an erosion rate of 0.21 mm / furnace campaign, and a campaign life of 1933. In the aggregate of the magnesia-carbon gas supply element in Example 5, there are only two different particle sizes of high-iron magnesia. The prepared magnesia-carbon gas supply element has a room-temperature compressive strength of 37 MPa, a high-temperature flexural strength of 7.6 MPa, an erosion rate of 0.21 mm / furnace campaign, and a campaign life of 1933. In the aggregate of the magnesia-carbon gas supply element in Example 6, only 18 parts of high-iron magnesia are included in the first aggregate. The prepared magnesia-carbon gas supply element has a room-temperature compressive strength of 38 MPa, a high-temperature flexural strength of 7.3 MPa, an erosion rate of 0.22 mm / furnace campaign, and a campaign life of 1845. In the aggregate of the magnesia-carbon gas supply element in Example 7, only 32 parts of fused magnesia are included in the second aggregate. The prepared magnesia-carbon gas supply element has a room-temperature compressive strength of 40 MPa, a high-temperature flexural strength of 7.4 MPa, an erosion rate of 0.21 mm / furnace campaign, and a campaign life of 1933. This shows that in the preparation process of the aggregate of the present invention, fused magnesia and high-iron magnesia with different particle sizes are selected. The small-particle-size fused magnesia or high-iron magnesia can be filled in the gaps between its large-particle-size particles, which can increase the packing density of the aggregate, improve the strength and density of the magnesia-carbon gas supply element, and enable it to better withstand harsh conditions such as high temperature and slag erosion during use. At the same time, by limiting the amounts of fused magnesia and high-iron magnesia with different particle sizes, the optimization of particle gradation can be achieved. A reasonable particle gradation can reduce the porosity of the material, increase the density and strength of the material. Further, the optimized particle gradation can also improve the erosion resistance and erosion resistance of the material, and extend the service life of the magnesia-carbon gas supply element.

[0141] (3) It can be seen from Example 1 and Examples 8 - 9 that the granulated powder of the MgO-C gas supply element in Example 1 includes aluminum silicon carbide ceramic powder and micro-nano titanium oxide ceramic powder. The prepared MgO-C gas supply element has a room temperature compressive strength of 41 MPa, a high temperature flexural strength of 8.8 MPa, an erosion rate of 0.18 mm per furnace campaign, and a campaign life of 2255. For the MgO-C gas supply element in Example 8, the granulated powder includes metallic aluminum powder and micro-nano titanium oxide ceramic powder. The prepared MgO-C gas supply element has a room temperature compressive strength of 45 MPa, a high temperature flexural strength of 5.6 MPa, an erosion rate of 0.22 mm per furnace campaign, and a campaign life of 1845. For the MgO-C gas supply element in Example 9, the granulated powder includes metallic silicon powder and micro-nano titanium oxide ceramic powder. The prepared MgO-C gas supply element has a room temperature compressive strength of 40 MPa, a high temperature flexural strength of 8.2 MPa, an erosion rate of 0.24 mm per furnace campaign, and a campaign life of 1691. This shows that the present invention selects aluminum silicon carbide ceramic powder and micro-nano titanium oxide ceramic powder as the granulated powder. The metallic aluminum and elemental silicon in the aluminum silicon carbide ceramic powder can capture carbon dioxide at the initial stage of bottom blowing, avoiding the adverse formation of a large amount of liquid phase when using a single metallic aluminum or elemental silicon as the raw material. At the same time, the aluminum silicon carbide ceramic powder can provide Si x O y (g) and Al x O y (g) and other high-activity substance sources, enabling them to continuously diffuse and mass transfer from the low-temperature zone inside the MgO-C gas supply element to the working end of the MgO-C gas supply element. Under the action of high-iron magnesite, physical vapor deposition reactions and chemical vapor deposition reactions occur, reconstructing the phase composition and micro-region structure of the aggregate and matrix, strengthening the pore structure between the aggregate and the matrix, enhancing the bonding performance between the matrix and the aggregate, the matrix and the matrix, and the aggregate and the aggregate in the MgO-C gas supply element, and weakening the adverse effects such as the decrease in bulk density and the attenuation of slag erosion resistance caused by the oxidation reaction of carbonaceous materials.

[0142] (4) It can be seen from Example 1 and Comparative Example 1 that the present invention adds high-iron magnesite to the aggregate of the MgO-C gas supply element, optimizes and adjusts the micro-region structure system of the aggregate and the matrix, and utilizes the strong mass diffusion effect of iron ions in the periclase lattice under the bottom-blown carbon dioxide atmosphere, the low-temperature sintering characteristics of magnesium aluminate spinel and magnesite fine powder, as well as the characteristics of the aluminum silicon carbide ceramic powder to capture carbon dioxide at the initial stage of bottom blowing and supply high-activity substance sources, so as to achieve the technical effect of improving the life of the gas supply element.

[0143] (5) It can be seen from Example 1 and Comparative Examples 2-3 that by limiting the contents of fused magnesia and high-iron magnesia in the aggregate, i.e., the aggregate includes 58-67 parts of fused magnesia and 5-12 parts of high-iron magnesia, the microstructural system of the aggregate and the matrix is optimized and adjusted. By utilizing the strong mass diffusion effect of iron ions in the periclase lattice under the bottom-blown carbon dioxide atmosphere, the low-temperature sintering characteristics of magnesium aluminate spinel and magnesia fine powder, and the characteristics of aluminum silicon carbide ceramic powder to capture carbon dioxide and high-reactivity substance sources in the initial stage of bottom blowing, the technical effect of improving the service life of the gas supply element can be achieved.

[0144] (6) It can be seen from Example 1 and Comparative Example 4 that the commercial magnesia-carbon gas supply element (MT-12) used in Comparative Example 4 has a room-temperature compressive strength of 40 MPa, a high-temperature flexural strength of 7.8 MPa, an erosion rate of 0.20 mm per furnace campaign, and a campaign life of 2030. That is, the strength and service life of the magnesia-carbon gas supply element prepared by the present invention are superior to those of the commercial magnesia-carbon gas supply element, and the magnesia-carbon gas supply element prepared by the present invention can improve its campaign life under the condition of bottom blowing carbon dioxide in the steelmaking furnace.

[0145] In summary, by adding high-iron magnesia to the magnesia-carbon gas supply element, the present invention utilizes the strong mass diffusion effect of iron ions in the periclase lattice under the bottom-blown carbon dioxide atmosphere to generate magnesium iron spinel on the surface / interface of the fused magnesia, which can solve the problem of difficult sintering on the surface / interface of the fused magnesia particles caused by the oxidation reaction of the carbonaceous material; and can enhance the high-temperature resistance and chemical stability of the magnesia-carbon gas supply element, which helps to reduce the loss of the magnesia-carbon gas supply element under high-temperature and corrosive atmospheres. The present invention prepares a new type of green and low-carbon magnesia-carbon gas supply element, and the performance of the magnesia-carbon gas supply element is excellent. The comprehensive service life is generally higher than that of the existing bottom-blown magnesia-carbon gas supply element. The performance of the magnesia-carbon gas supply element meets the following requirements: 2.98 g / cm 3 ≤ bulk density ≤ 3.10 g / cm 3 , 3% ≤ apparent porosity ≤ 5%, 40 MPa ≤ room-temperature compressive strength ≤ 48 MPa, 8.0 MPa ≤ high-temperature flexural strength ≤ 14 MPa.

[0146] The applicant declares that the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A magnesium-carbon gas supply element, characterized in that: The magnesium-carbon gas supply element comprises a main raw material, and the main raw material comprises an aggregate and a matrix; Based on 100 parts by weight of the magnesium-carbon gas supply element, the aggregate includes 58-67 parts of fused magnesia and 5-12 parts of high-iron magnesia.

2. The magnesium-carbon gas supply element according to claim 1, characterized in that: The magnesium-carbon gas supply element also includes auxiliary materials; Preferably, the auxiliary material is a binder; Preferably, based on 100 parts by weight of the magnesium-carbon gas supply element, the magnesium-carbon gas supply element includes 70-73 parts of aggregate, 24-26 parts of matrix and 3-4 parts of binder.

3. The magnesium-carbon gas supply element according to claim 1 or 2, characterized in that: The aggregate includes a first aggregate, a second aggregate and a third aggregate; Preferably, the aggregate includes 16-20 parts of the first aggregate, 32-35 parts of the second aggregate and 20-25 parts of the third aggregate; Preferably, the first aggregate includes first fused magnesia sand and first high-iron magnesia sand; Based on 100 parts by weight of the magnesium-carbon gas supply element, the first aggregate includes 14-18 parts of the first fused magnesia sand and 1-4 parts of the first high-iron magnesia sand; Preferably, the second aggregate comprises a second fused magnesia sand and a second high-iron magnesia sand; Preferably, the second aggregate includes 25-30 parts of the second fused magnesia sand and 2-5 parts of the second high-iron magnesia sand; Preferably, the third aggregate includes third fused magnesia sand and third high-iron magnesia sand; Preferably, the third aggregate includes 17-20 parts of the third fused magnesia sand and 0-6 parts of the third high-iron magnesia sand.

4. The magnesium-carbon gas supply element according to claim 3, characterized in that: The particle size of the first fused magnesia is smaller than that of the second fused magnesia, and the particle size of the second fused magnesia is smaller than that of the third fused magnesia; Preferably, the particle size of the first fused magnesia is 4-8 mesh; Preferably, the particle size of the second fused magnesia is 9-14 mesh; Preferably, the particle size of the third fused magnesia is 15-65 mesh; Preferably, the particle size of the first high-iron magnesia sand is smaller than that of the second high-iron magnesia sand, and the particle size of the second high-iron magnesia sand is smaller than that of the third high-iron magnesia sand; Preferably, the particle size of the first high-iron magnesia sand is 4-8 mesh; Preferably, the particle size of the second high-iron magnesia sand is 9-14 mesh; Preferably, the particle size of the third high-iron magnesia sand is 15-65 mesh.

5. The magnesium-carbon gas supply element according to claim 3 or 4, characterized in that: The mass percentage of magnesium oxide in the first fused magnesia, the second fused magnesia and the third fused magnesia is independently ≥ 97.2%; Preferably, the mass percentage of magnesium oxide in the first high-iron magnesia sand, the second high-iron magnesia sand and the third high-iron magnesia sand is independently ≥94%; Preferably, the mass percentage of iron oxide in the first high-iron magnesia sand, the second high-iron magnesia sand and the third high-iron magnesia sand is independently ≥5%; Preferably, based on 100 parts by weight of the magnesium-carbon gas supply element, the matrix includes 4-5 parts of modified magnesia powder, 7-8 parts of graphite and 8-10 parts of granulation powder, and the balance is fused magnesia powder; Preferably, the particle size of the modified magnesia powder is 70 μm ≤ D50 ≤ 100 μm; Preferably, the particle size of the graphite is 90 μm ≤ D50 ≤ 120 μm.

6. The magnesium-carbon gas supply element according to claim 5, characterized in that: The granulated powder includes aluminum silicon carbide ceramic powder and micro-nano titanium oxide ceramic powder; Preferably, the particle size of the granulated powder is 200 μm ≤ D50 ≤ 500 μm; Preferably, based on 100 parts by weight of the granulated powder, the granulated powder comprises 95-97 parts of aluminum silicon carbide ceramic powder and 3-5 parts of micro-nano titanium oxide ceramic powder; Preferably, the particle size of the aluminum silicon carbide ceramic powder is 80 μm ≤ D50 ≤ 100 μm; Preferably, the particle size of the micro-nano titanium oxide ceramic powder is 0.5 μm≤D50≤1.5 μm; Preferably, the particle size of the fused magnesia powder is 70 μm ≤ D50 ≤ 100 μm.

7. A method for preparing a magnesium-carbon gas supply element according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: The matrix and aggregates containing fused magnesia and high-iron magnesia are mixed and kneaded, and the obtained mixed product is subjected to aging, molding and heat treatment in sequence to obtain the magnesium-carbon gas supply element.

8. The preparation method according to claim 7, characterized in that: The step of mixing the matrix and the aggregate containing fused magnesia and high-iron magnesia comprises: (1) mixing fused magnesia and high iron magnesia, and performing a first sub-mixing to obtain the aggregate; adding a binder to the aggregate and performing a second sub-mixing to obtain an aggregate intermediate; (2) mixing modified magnesia powder, graphite, granulated powder and fused magnesia powder, and performing a third sub-mixing to obtain the matrix; (3) mixing the intermediate aggregate obtained in step (1) and the matrix obtained in step (2) and performing a fourth sub-mixing to obtain the mixed product; There is no order of precedence between step (1) and step (2); Preferably, the preparation method further comprises: mixing aluminum silicon carbide ceramic powder, micro-nano titanium oxide ceramic powder and solvent, performing mixing and rotary granulation in sequence, and obtaining the granulated powder having a particle size of 200 μm ≤ D50 ≤ 500 μm after baking and sieving; Preferably, the solvent comprises any one or a combination of at least two of polyvinyl alcohol, carboxymethyl cellulose or starch; Preferably, the temperatures of the first sub-mixing, the second sub-mixing, the third sub-mixing and the fourth sub-mixing are independently 45-55° C.; Preferably, the first sub-mixing time is 8-10min; Preferably, the second mixing time is 10-15min; Preferably, the third sub-mixing time is 10-15 minutes; Preferably, the fourth sub-mixing time is 30-40 minutes.

9. The preparation method according to claim 7 or 8, characterized in that: The preparation method comprises the following steps: (1) mixing the fused magnesia and the high iron magnesia, and kneading them at 45-55° C. for 8-10 minutes to obtain aggregate; adding a binder to the aggregate, and kneading them at 45-55° C. for 10-15 minutes to obtain an aggregate intermediate; (2) mixing aluminum silicon carbide ceramic powder, micro-nano titanium oxide ceramic powder and solvent, kneading and rotary granulation in sequence, and obtaining granulated powder with a particle size of 200 μm ≤ D50 ≤ 500 μm after baking and sieving; mixing modified magnesia powder, graphite, granulated powder and fused magnesia powder, and kneading at 45-55° C. for 10-15 minutes to obtain the matrix; (3) The intermediate aggregate obtained in step (1) and the matrix obtained in step (2) are mixed and kneaded at 45-55° C. for 30-40 min. The kneaded product is then aged, formed and heat treated in sequence to obtain the magnesium-carbon gas supply element.

10. Use of the magnesium-carbon gas supply element according to any one of claims 1 to 6 in a steelmaking furnace.

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