Method for preparing carbon-free tundish covering agent from magnesium reducing slag

Abstract

The invention relates to the field of comprehensive utilization of steel smelting, in particular to a method for preparing a carbon-free tundish covering agent from magnesium reducing slag. The method for preparing the carbon-free tundish covering agent by using the magnesium reducing slag comprises the following steps: carrying out water quenching and magnetic separation on the high-temperature magnesium reducing slag to obtain the magnesium reducing slag subjected to magnetic separation; and the magnesium reducing slag obtained after magnetic separation is evenly mixed with a tempering agent and a binding agent and then subjected to compression molding, then curing and crushing are conducted, and the carbon-free tundish covering agent is obtained. The carbon-free tundish covering agent is finally prepared by carrying out water quenching cooling and magnetic separation on the high-temperature magnesium reducing slag to remove an iron element, mixing the high-temperature magnesium reducing slag with a hardening and tempering agent and a binder, carrying out compression molding and then carrying out maintenance. The method has the characteristics of simple process, low cost and environmental protection.

Description

Technical Field

[0001] The present invention relates to the field of comprehensive utilization of iron and steel smelting, and particularly to a method for preparing a carbon-free tundish covering agent from magnesium reduction slag. Background Art

[0002] Magnesium reduction slag is a solid waste generated during the smelting of metallic magnesium, and its main components are magnesium oxide, calcium oxide, and a small amount of impurities such as iron and silicon. Due to the large discharge amount of magnesium reduction slag, and it is usually directly stacked after being discharged at high temperature, which is likely to cause problems such as dust flying and environmental pollution, affecting the surrounding ecological environment. At the same time, magnesium reduction slag contains relatively high contents of magnesium oxide and calcium oxide, and these components have certain industrial utilization values.

[0003] Patent CN108580821A discloses a calcium-magnesium tundish heat-insulating covering agent and a preparation method thereof, in which calcium-magnesium particles and plant ash are pulverized and ground and then mixed to prepare the tundish covering agent. This patent uses the common method for preparing the tundish covering agent, and the covering agent produced after combustion generates a large amount of carbon dioxide and other harmful gases, which is not conducive to environmental protection. Patent CN105033207B discloses a tundish covering agent produced from calcined vanadium extraction slag and a preparation method thereof. This patent uses calcined vanadium extraction tailings to compound with other raw materials to prepare the tundish covering agent, and the process is complex and the cost is relatively high. Summary of the Invention

[0004] Based on the above, the present invention provides a method for preparing a carbon-free tundish covering agent from magnesium reduction slag. The present invention utilizes the high alkalinity characteristics of magnesium reduction slag to realize the secondary utilization of magnesium reduction slag, and has the characteristics of simple process and low production cost.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention, a method for preparing a carbon-free tundish covering agent from magnesium reduction slag, includes the following steps:

[0007] Subject the high-temperature magnesium reduction slag to water quenching and magnetic separation to obtain the magnesium reduction slag after magnetic separation;

[0008] Mix the magnesium reduction slag after magnetic separation with a conditioning agent and a binder, then press and mold, and then cure and crush to obtain the carbon-free tundish covering agent.

[0009] Another technical solution of the present invention, a carbon-free tundish covering agent prepared according to the above method.

[0010] Another technical solution of the present invention, the application of the carbon-free tundish covering agent in iron and steel smelting.

[0011] The present invention discloses the following technical effects:

[0012] In the present invention, the magnesium reduction slag is quenched and cooled by high temperature, the iron element is removed by magnetic separation, combined with a conditioning agent and a binder, and after being pressed into shape, it is cured, and finally a carbon-free tundish covering agent is prepared. The method of the present invention has the characteristics of simple process, low cost and environmental protection. Specific Embodiments

[0013] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and implementation embodiments of the present invention.

[0014] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0015] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0016] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and embodiments of the present invention are only exemplary.

[0017] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, that is, they are meant to include but not limited to.

[0018] In the embodiments of the present invention, the "%" used, unless otherwise specified, all represent mass percentages.

[0019] The present invention sets requirements for the iron content in magnesium reduction slag, controls the proportion and addition amount of the conditioning agent, and further sets requirements for the component content of the conditioning agent. When preparing the tundish covering agent, requirements are put forward for the components and addition amount of the binder, as well as for the curing time and temperature. A method for preparing a carbon-free tundish covering agent from magnesium reduction slag with simple process, safe operation and easy implementation is designed, which can effectively improve the utilization rate of magnesium reduction slag and has important significance in practical applications.

[0020] In a first aspect of the present invention, a method for preparing a carbon-free tundish covering agent from magnesium reduction slag is provided, comprising the following steps:

[0021] Subject the high-temperature magnesium reduction slag to water quenching and magnetic separation to obtain the magnesium reduction slag after magnetic separation;

[0022] Mix the magnesium reduction slag after magnetic separation with a conditioning agent and a binder, then press and form, and then cure and crush to obtain the carbon-free tundish covering agent.

[0023] In a preferred embodiment of the present invention, the high-temperature magnesium reduction slag refers to the solid residue remaining after the high-temperature reduction reaction in the production process of metallic magnesium; the component composition of the high-temperature magnesium reduction slag includes: CaO 50wt% - 55wt%, SiO2 20wt% - 25wt%, MgO 5wt% - 10wt%, Al2O3 3wt% - 5%, Fe2O3 3wt% - 5% and the balance ash.

[0024] The water quenching is specifically to rapidly cool the high-temperature magnesium reduction slag (temperature about 1200 - 1400 °C) by high-pressure water flow (water pressure 0.5 - 1.0 MPa) to form glassy particles. During the water quenching process, the slag liquid flows through the nozzle and is atomized and then falls into the water tank. The cooling rate needs to be controlled at 100 - 200 °C / s, and the water temperature is controlled at 30 - 40 °C to ensure the formation of an amorphous structure inside the slag particles and reduce the difficulty of subsequent magnetic separation.

[0025] After the water quenching and before the magnetic separation, there is also a step of crushing the magnesium reduction slag obtained by water quenching so that the proportion of the part with a particle size not greater than 74 μm accounts for 80wt% - 90wt%.

[0026] The magnetic separation is specifically to use a permanent magnet roll-type magnetic separator (magnetic field strength ≥ 1.2 T) to separate the crushed magnesium reduction slag. The magnetic separation process is divided into two stages: rough separation: removing the metal iron particles with strong magnetism in the slag (Fe content > 1wt%); fine separation: further separating the weakly magnetic iron oxide to ensure that the iron element content in the magnesium reduction slag after magnetic separation is ≤ 1wt%, and the preferred range is the iron element content of 0.2wt% - 0.8wt%.

[0027] In a preferred embodiment of the present invention, by mass percentage, the iron element content in the magnesium reduction slag after magnetic separation does not exceed 1wt%.

[0028] In some embodiments of the present invention, the iron element content in the magnesium reduction slag after magnetic separation is 0.2 wt% - 0.8 wt%.

[0029] In a preferred embodiment of the present invention, the conditioning agent includes bauxite and fluorite; the mass ratio of bauxite to fluorite is (3 - 7):1; the addition amount of the conditioning agent is 20% - 30% of the mass of the magnesium reduction slag after magnetic separation.

[0030] In a preferred embodiment of the present invention, the Al2O3 content in the bauxite is 65 wt% - 75 wt%; the CaF2 content in the fluorite is 70 wt% - 85 wt%.

[0031] In a preferred embodiment of the present invention, the binder is high-alumina cement; the addition amount of the binder is 5% - 10% of the mass of the magnesium reduction slag after magnetic separation.

[0032] In a preferred embodiment of the present invention, the curing temperature is 30 - 45 °C and the time is 7 - 10 days.

[0033] In a preferred embodiment of the present invention, the crushing specifically means crushing to a particle size of not more than 1.2 mm for 70 wt% - 95 wt% of the material.

[0034] The present invention prepares a carbon-free tundish covering agent with moderate particle size and excellent performance through the above method.

[0035] The second aspect of the present invention provides a carbon-free tundish covering agent prepared according to the above method.

[0036] The third aspect of the present invention provides the application of the carbon-free tundish covering agent in steel smelting.

[0037] The technical solutions of the present invention are all conventional solutions in the art unless otherwise specified, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0038] The main component composition of the magnesium reduction slag used in the examples of the present invention is as follows: CaO 54 wt%, SiO2 23%, MgO 8%, Al2O3 4%, Fe2O3 3% and the balance ash.

[0039] The main component composition of the bauxite used in the examples of the present invention is as follows: Al2O3 72 wt%, SiO2 11%, TiO2 4% and impurities; the main component composition of the fluorite is as follows: CaF2 83 wt%, SiO2 5% and impurities.

[0040] In the embodiments of the present invention, the binder used is high-aluminum cement, with the main parameters: the Al2O3 content is 58wt%, the modulus is 1.2, the initial setting time > 30 minutes, and the compressive strength (28 days) > 40MPa.

[0041] The test method involved in the present invention is as follows:

[0042] According to the YB / T 6283-2024 standard, for the melting temperature, the heating headspace method is adopted. The tundish covering agent sample is filled in a crucible and placed in an electric resistance furnace to be gradually heated. The starting melting point is determined by observing the morphological changes of the sample.

[0043] For the spreading time, during the pouring process of the tundish, after the covering agent is added once, the time when the surface covering agent just melts is taken as the standard.

[0044] The average temperature drop of the molten steel is measured using a fast micro-heating type thermocouple probe. One thermocouple is inserted into the tundish for temperature measurement every 5 minutes.

[0045] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0046] Example 1

[0047] The high-temperature magnesium reduction slag is subjected to water quenching treatment and then crushed to a particle size of 74μm. After magnetic separation of the crushed magnesium reduction slag, the iron content is reduced to 0.8wt%. The conditioning agent consists of bauxite and fluorite, and the mass ratio of bauxite to fluorite is 4:1. The addition amount of the conditioning agent is 25% of the mass of the magnetically separated magnesium reduction slag, and the addition amount of the binder is 6% of the mass of the magnetically separated magnesium reduction slag. The magnetically separated magnesium reduction slag is mixed with the conditioning agent and the binder, and then pressed into a cylindrical briquette using a hydraulic press (the pressing pressure is 80MPa), with a diameter of 30±2mm and a height of 15±1mm. The formed briquette is cured at 40°C for 7 days with a relative humidity of 80%. After curing, it is crushed to obtain a carbon-free tundish covering agent, and the proportion of particles with a size less than 1.2mm is 70wt%.

[0048] The composition of the carbon-free tundish covering agent prepared in this example is as follows (by mass percentage): the CaO content is 50%, Al2O3 22wt%, SiO2 18wt%, CaF2 8wt%, and the remaining components are impurities. The melting point of this carbon-free tundish covering agent is 1310°C, the spreading time is 35S, and the average temperature drop of the molten steel is 2.5°C / furnace.

[0049] Example 2

[0050] After subjecting high-temperature magnesium reduction slag to water quenching treatment, it is crushed to a particle size of 74 μm. After magnetic separation of the crushed magnesium reduction slag, the iron content is reduced to 0.5 wt%. The conditioning agent consists of bauxite and fluorite, and the mass ratio of bauxite to fluorite is 5:1. The addition amount of the conditioning agent is 20% of the mass of the magnesium reduction slag after magnetic separation, and the addition amount of the binder is 10% of the mass of the magnesium reduction slag after magnetic separation. After mixing the magnesium reduction slag after magnetic separation with the conditioning agent and the binder, a hydraulic press (pressing pressure is 100 MPa) is used to press it into a cylindrical briquette with a diameter of 30 ± 2 mm and a height of 15 ± 1 mm. The formed block is cured at 35 °C for 7 days with a relative humidity of 70%. After curing, it is crushed to obtain a carbon-free tundish covering agent, and the proportion of particles smaller than 1.2 mm is 80 wt%.

[0051] The composition of the carbon-free tundish covering agent prepared in this example is as follows (by mass percentage): CaO 46%, Al2O3 25 wt%, SiO2 16 wt%, CaF2 6 wt%, and the remaining components are impurities. The melting point of this carbon-free tundish covering agent is 1323 °C, the spreading time is 30 S, and the average temperature drop of the molten steel is 2.3 °C / furnace.

[0052] Example 3

[0053] After subjecting high-temperature magnesium reduction slag to water quenching treatment, it is crushed to a particle size of 74 μm. After magnetic separation of the crushed magnesium reduction slag, the iron content is reduced to 0.6 wt%. The conditioning agent consists of bauxite and fluorite, and the mass of bauxite and fluorite is 7:1. The addition amount of the conditioning agent is 30% of the mass of the magnesium reduction slag after magnetic separation. After mixing the magnesium reduction slag after magnetic separation with the conditioning agent and the binder, a hydraulic press (pressing pressure is 70 MPa) is used to press it into a cylindrical briquette with a diameter of 30 ± 2 mm and a height of 15 ± 1 mm. The formed block is cured at 45 °C for 7 days with a relative humidity of 90%. After curing, it is crushed to obtain a carbon-free tundish covering agent, and the proportion of particles smaller than 1.2 mm is 75 wt%.

[0054] The composition of the carbon-free tundish covering agent prepared in this example is as follows (by mass percentage): the CaO content is 43%, Al2O3 33 wt%, SiO2 14 wt%, CaF2 4 wt%, and the remaining components are impurities. The melting point of this carbon-free tundish covering agent is 1380 °C, the spreading time is 42 S, and the average temperature drop of the molten steel is 3.1 °C / furnace.

[0055] Comparative Example 1

[0056] The difference from Example 2 is only that the addition amount of the conditioning agent is 10% of the mass of the magnesium reduction slag, and the remaining steps and parameters are the same as those in Example 2.

[0057] Comparative Example 2

[0058] The difference from Example 2 is only that the addition amount of the tempering agent is 40% of the mass of the magnesium reduction slag, and the remaining steps and parameters are the same as those in Example 2.

[0059] Comparative Example 3

[0060] The difference from Example 2 is only that the addition amount of the tempering agent is 50% of the mass of the magnesium reduction slag, and the remaining steps and parameters are the same as those in Example 2.

[0061] The test results of the carbon-free tundish covering agents prepared in Comparative Example 1, Comparative Example 2 and Comparative Example 3 are shown in Table 1.

[0062] Table 1

[0063] Comparison items Comparative Example 1 Comparative Example 2 Comparative Example 3 Melting point, °C 1280 1380 1410 Spreading time, s 52S 48S 58S Average temperature drop, °C 6.5 5.3 7.1

[0064] It can be seen from Table 1 and the effect data of the examples that the carbon-free tundish covering agent prepared in the examples of the present invention has excellent spreading property and heat insulation ability. The carbon-free tundish covering agent of the present invention meets the requirements of smelting production and can effectively solve the problem of utilization of magnesium reduction slag resources.

[0065] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a carbon-free tundish covering agent from magnesium reduction slag, characterized in that, It includes the following steps: The high-temperature magnesium reduction slag is quenched with water and subjected to magnetic separation to obtain the magnesium reduction slag after magnetic separation; The magnesium reduction slag after magnetic separation is mixed with a conditioning agent and a binder, then pressed into a shape, and after curing and crushing, the carbon-free tundish covering agent is obtained.

2. The method for preparing a carbon-free tundish covering agent from magnesium reduction slag according to claim 1, characterized in that, By mass percentage, the composition of the high-temperature magnesium reduction slag includes: 50wt% - 55% of CaO, 20wt% - 25% of SiO2, 5wt% - 10% of MgO, 3wt% - 5% of Al2O3, 3wt% - 5% of Fe2O3, and the balance of ash.

3. The method for preparing a carbon-free tundish covering agent from magnesium reduction slag according to claim 1, characterized in that, The iron element content in the magnesium reduction slag after magnetic separation does not exceed 1wt%.

4. The method for preparing a carbon-free tundish covering agent from magnesium reduction slag according to claim 1, wherein, The conditioning agent includes bauxite and fluorite; the mass ratio of the bauxite to the fluorite is (3 - 7):1; the addition amount of the conditioning agent is 20% - 30% of the mass of the magnesium reduction slag after magnetic separation.

5. The method for preparing a carbon-free tundish covering agent from magnesium reduction slag according to claim 4, wherein, The Al2O3 content in the bauxite is 65wt% - 75wt%; the CaF2 content in the fluorite is 70wt% - 85wt%.

6. The method for preparing a carbon-free tundish covering agent from magnesium reduction slag according to claim 1, characterized in that, The binder is high-alumina cement; the addition amount of the binder is 5% - 10% of the mass of the magnesium reduction slag after magnetic separation.

7. The method for preparing a carbon-free tundish covering agent from magnesium reduction slag according to claim 1, wherein The curing temperature is 30 - 45°C and the time is 7 - 10 days.

8. The method for preparing a carbon-free tundish covering agent from magnesium reduction slag according to claim 1, characterized in that, The crushing specifically means crushing until 70wt% - 95wt% of the material particle size does not exceed 1.2 mm.

9. The carbon-free tundish covering agent prepared by the method according to any one of claims 1 - 8.

10. The application of the carbon-free tundish covering agent according to claim 9 in steel smelting.