CN111809006B - Method for refining size of free magnesium oxide in steel slag of ladle furnace - Google Patents
Method for refining size of free magnesium oxide in steel slag of ladle furnace Download PDFInfo
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- CN111809006B CN111809006B CN202010566714.4A CN202010566714A CN111809006B CN 111809006 B CN111809006 B CN 111809006B CN 202010566714 A CN202010566714 A CN 202010566714A CN 111809006 B CN111809006 B CN 111809006B
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- ladle furnace
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B3/00—General features in the manufacture of pig-iron
- C21B3/04—Recovery of by-products, e.g. slag
- C21B3/06—Treatment of liquid slag
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B3/00—General features in the manufacture of pig-iron
- C21B3/04—Recovery of by-products, e.g. slag
- C21B3/06—Treatment of liquid slag
- C21B3/08—Cooling slag
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B2400/00—Treatment of slags originating from iron or steel processes
- C21B2400/02—Physical or chemical treatment of slags
- C21B2400/022—Methods of cooling or quenching molten slag
- C21B2400/024—Methods of cooling or quenching molten slag with the direct use of steam or liquid coolants, e.g. water
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B2400/00—Treatment of slags originating from iron or steel processes
- C21B2400/02—Physical or chemical treatment of slags
- C21B2400/022—Methods of cooling or quenching molten slag
- C21B2400/026—Methods of cooling or quenching molten slag using air, inert gases or removable conductive bodies
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
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- Treatment Of Steel In Its Molten State (AREA)
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- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
The invention discloses a method for refining the size of free magnesium oxide in ladle furnace steel slag, which comprises the steps of firstly adding a proper amount of crystal grain growth inhibitor into the ladle furnace steel slag, and heating to ensure that the ladle furnace steel slag is in a molten liquid state; in the process of flowing out the slag liquid through the chute, carrying out air quenching and quenching treatment on the steel slag of the ladle furnace by adopting high-pressure and high-speed air; collecting steel ladle furnace steel slag particles subjected to air quenching treatment by using a rotary cooling cylinder, and performing outer cylinder water circulation secondary cooling; and finally, collecting the treated steel slag of the ladle furnace. The invention reduces the average size of free magnesium oxide in the processed steel slag of the ladle furnace by 1 order of magnitude by carrying out primary air quenching cooling and secondary outer cylinder water circulation cooling on the molten steel slag of the ladle furnace and assisting the action of a crystal grain growth inhibitor, keeps smaller size and higher activity, is very helpful to improve the volume stability of the steel slag of the ladle furnace when the steel slag is used as a cementing material for building materials, and promotes the efficient utilization of building material resources.
Description
Technical Field
The invention relates to the technical field of resource utilization of ladle furnace refining slag, in particular to a method for refining the size of free magnesium oxide in ladle furnace steel slag.
Background
The ladle furnace refining slag is a smelting by-product generated in the process of refining scrap steel or crude steel by using a ladle refining furnace, and according to statistics, 20-50kg of ladle furnace steel slag needs to be discharged every 1t of molten steel is refined. With the accelerated advancement of steel and iron in China into depreciation times and the huge demand of China on special steel/high-quality steel, the refining demand of scrap steel and crude steel is rapidly increased year by year (the depreciation amount of scrap steel and the yield of crude steel in China reach 2 hundred million tons and 8.3 million tons respectively in 2017 < data of the China's iron and steel Association, the State statistical office), and a great amount of steel slag of ladle furnaces is generated. At present, only a small amount of steel slag of a ladle furnace is recycled as a metallurgy return material (such as a fluxing agent and a slagging material), most of the rest refining slag is discharged and accumulated, the utilization rate is low, a large amount of land is occupied, and environmental pollution is caused.
From the chemical and mineral composition, the ladle furnace steel slag mainly comprises CaO, Al2O3 and SiO2, and the mineral of the steel slag is mainly heptaaluminum dodecacalcium (C12)A7) Dicalcium silicate (C2S) and tricalcium aluminate (C3A), which are important gelling minerals for aluminate cement and portland cement. Therefore, the ladle furnace steel slag has great potential as a cementing material to be applied to building materials. However, the important value of the steel ladle furnace slag containing C12A7, C2S and other gelled minerals is not effectively utilized at present, one of the main reasons is that the steel ladle furnace slag forms overburnt free MgO and CaO with compact crystals and coarse grains in the natural cooling process under the high-temperature melting condition, the hydration process is slow, and the f-CaO and the f-MgO generate Mg (OH) in the later hydration reaction2And Ca (OH)2Significant volume expansion (148% and 98% increase in volume, respectively) can occur, severely affecting the volumetric stability of the material. Especially, the later hydration of the over-sintered f-MgO is very slow, can last for years or even more than ten years, and is the main reason causing the poor volume stability of the metallurgical slag cementing material.
Therefore, eliminating or reducing the risk of poor volume stability of the steel slag of the ladle furnace is the primary key for promoting the resource utilization of the building materials, and measures of improving the structural characteristics (compactness, crystal grains and defects) of f-MgO and f-CaO in the steel slag of the ladle furnace, improving the activity of the steel slag, reducing the content of the steel slag and the like are important ways for improving the volume stability of the steel slag of the ladle furnace.
At present, steel scrap and crude steel refining enterprises do not specially treat discharged steel slag of a ladle furnace, and the steel slag is discharged and accumulated after being cooled by generally adopting a natural cooling mode, so that f-MgO is crystallized compactly and grains are coarse; for converter steel slag, at present, a thermal stewing treatment process is commonly adopted to eliminate part of f-CaO and f-MgO in the converter steel slag in advance and reduce the content of the f-CaO and the f-MgO, but water in the method can generate hydration reaction with part of gelled minerals in advance, so that the activity of the steel slag is reduced to a certain extent, particularly C in steel ladle furnace steel slag12A7The mineral reacts with water quickly, and the method can obviously reduce the gelling activity of the steel slag of the ladle furnace, so the mineral is not suitable for the steel slag of the ladle furnace. Therefore, the invention provides a method for cooling molten liquid steel slag of a ladle furnace by primary air quenching and secondary outer cylinder water circulation, and adding a grain growth inhibitorThe method has the advantages of refining the f-MgO size in the steel slag of the ladle furnace, improving the activity of the steel slag and reducing the adverse effect of the steel slag on the volume stability of the steel slag of the ladle furnace.
Disclosure of Invention
The invention aims to eliminate or reduce the risk of bad volume stability of f-MgO in the steel slag of a ladle furnace, provides a treatment method for refining the size of free magnesium oxide in the refining slag of the ladle furnace, can obviously reduce the size of the f-MgO in the steel slag of the ladle furnace, improves the hydration activity of the f-MgO, and greatly improves the volume stability of the steel slag of the ladle furnace.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method of refining the size of free magnesium oxide in ladle furnace slag, the method comprising the steps of:
s1, adding a crystal grain growth inhibitor into the steel slag of the ladle furnace, and heating to ensure that the steel slag of the ladle furnace is in molten liquid state;
s2, carrying out air quenching and quenching treatment on the slag liquid by adopting high-pressure and high-speed air in the process of flowing the slag liquid out through the chute;
s3, collecting ladle furnace steel slag particles formed by slag liquid after air quenching treatment by adopting a rotary cooling cylinder;
s4, carrying out water circulation secondary cooling on the steel ladle furnace steel slag particles in the cylinder by using the outer cylinder of the rotary cooling cylinder;
s5, collecting the steel slag particles of the ladle furnace after the secondary cooling treatment of water circulation.
Preferably, the grain growth inhibitor is one or two of LiF and NaF, and the addition amount is 0.2-3%.
Preferably, the high-pressure high-speed air is generated by a device consisting of an air compressor and a Laval nozzle or an air ejector; the pressure of the high-pressure high-speed air in the air quenching and quenching treatment is 0.6-1.6 MPa.
Preferably, the rotary cooling cylinder is arranged inclined at 5-15 ° with respect to the horizontal plane.
Preferably, the rotating speed of the rotary cooling cylinder is 10-60r/min
It needs to be further explained that the rotary cooling cylinder adopted by the invention at least comprises a cylinder body, a water spraying mechanism, a rotating motor, a negative pressure mechanism, a material inlet, a material outlet groove and a support.
Further, the cylinder body is arranged on the support, one end of the cylinder body is provided with a material inlet, and the other end of the cylinder body is provided with an outlet groove; the cylinder body consists of an outer cylinder and an inner cylinder, a water spraying space is formed between the outer cylinder and the inner cylinder, and the water spraying mechanism is arranged in the water spraying space and is used for spraying cooling water to the water spraying space; the negative pressure mechanism is arranged in the inner cylinder and can enable the inner cylinder to generate negative pressure so as to enable ladle furnace steel slag particles to rapidly flow to the outlet groove in the inner cylinder; the rotating motor is connected with the cylinder body to enable the cylinder body to rotate.
The invention has the beneficial effects that:
1. the invention has the obvious effect of reducing the average size of free magnesium oxide in the treated steel slag of the ladle furnace by 1 order of magnitude by carrying out primary air quenching cooling and secondary outer cylinder water circulation cooling on the molten steel slag of the ladle furnace and assisting the action of a crystal grain growth inhibitor, thereby being very beneficial to improving the volume stability of the steel slag of the ladle furnace as a cementing material when being used as a building material and promoting the efficient utilization of the building material resource.
2. Aiming at the condition that the steel slag of the ladle furnace after primary air quenching treatment still generally has the temperature of hundreds of ℃, the invention provides and adopts a novel method of secondary outer cylinder water circulation cooling, creatively uses a rotary cooling cylinder to collect the steel slag of the ladle furnace after air quenching and further rapidly carries out non-contact water cooling on the steel slag, thereby not only having high treatment efficiency, but also avoiding the contact between the steel slag of the ladle furnace and water, reducing the risk of the hydration performance of the steel slag, and ensuring the gelling activity of the steel slag. More importantly, the treatment process is carried out in a relatively closed environment, so that the environmental pollution such as dust flying in the cooling process is reduced, and the treatment process is more environment-friendly.
3. In the treatment of the free magnesium oxide in the refined steel ladle furnace steel slag, the rapid cooling method is adopted, so the gelling activity of the treated steel ladle furnace steel slag is obviously improved, and the application of the treated steel ladle furnace steel slag in building materials is promoted.
4. Compared with the common treatment method, the method disclosed by the invention fully combines the advantages of air quenching (primary quick air cooling) and water quenching (outer cylinder non-contact secondary water cooling), and has a higher treatment effect.
5. The invention also uses a crystal grain growth inhibitor in the process of treating the steel slag of the ladle furnace, can further inhibit the crystal grain growth of free magnesium oxide in the refining slag in the cooling process of the steel slag of the ladle furnace, refines the size of the free magnesium oxide, and has innovation.
Drawings
FIG. 1 is a comparison of the morphology and size of f-MgO in steel slag of a ladle furnace of a control group and that of steel slag of example 1 of the present invention;
FIG. 2 is a comparison of the morphology and size of f-MgO in the steel slag of the ladle furnace of the control group and the steel slag of the embodiment 2 of the present invention;
FIG. 3 is a method for refining the size of free magnesium oxide in ladle furnace steel slag according to the present invention.
Detailed Description
The present invention will be further described with reference to the accompanying drawings, and it should be noted that the following examples are provided to illustrate the detailed embodiments and specific operations based on the technical solutions of the present invention, but the scope of the present invention is not limited to the examples.
As shown in FIG. 3, the present invention is a method for refining the size of free magnesium oxide in steel slag of a ladle furnace, comprising the steps of:
s1, adding a crystal grain growth inhibitor into the steel slag of the ladle furnace, and heating to ensure that the steel slag of the ladle furnace is in molten liquid state;
s2, carrying out air quenching and quenching treatment on the slag liquid by adopting high-pressure and high-speed air in the process of flowing the slag liquid out through the chute;
s3, collecting ladle furnace steel slag particles formed by slag liquid after air quenching treatment by adopting a rotary cooling cylinder;
s4, carrying out water circulation secondary cooling on the steel ladle furnace steel slag particles in the cylinder by using the outer cylinder of the rotary cooling cylinder;
s5, collecting the steel slag particles of the ladle furnace after the secondary cooling treatment of water circulation.
Preferably, the grain growth inhibitor is one or two of LiF and NaF, and the addition amount is 0.2-3%.
Preferably, the high-pressure high-speed air is generated by a device consisting of an air compressor and a Laval nozzle or an air ejector; the pressure of the high-pressure high-speed air in the air quenching and quenching treatment is 0.6-1.6 MPa.
Preferably, the rotary cooling cylinder is arranged inclined at 5-15 ° with respect to the horizontal plane.
Preferably, the rotating speed of the rotary cooling cylinder is 10-60r/min
It needs to be further explained that the rotary cooling cylinder adopted by the invention at least comprises a cylinder body, a water spraying mechanism, a rotating motor, a negative pressure mechanism, a material inlet, a material outlet groove and a support.
Further, the cylinder body is arranged on the support, one end of the cylinder body is provided with a material inlet, and the other end of the cylinder body is provided with an outlet groove; the cylinder body consists of an outer cylinder and an inner cylinder, a water spraying space is formed between the outer cylinder and the inner cylinder, and the water spraying mechanism is arranged in the water spraying space and is used for spraying cooling water to the water spraying space; the negative pressure mechanism is arranged in the inner cylinder and can enable the inner cylinder to generate negative pressure so as to enable ladle furnace steel slag particles to rapidly flow to the outlet groove in the inner cylinder; the rotating motor is connected with the cylinder body to enable the cylinder body to rotate.
Example 1
Firstly, adding 0.5 percent of NaF into the steel slag of the ladle furnace, and heating to 1450 ℃ to ensure that the steel slag of the ladle furnace is in a molten liquid state; then, in the process of flowing out the slag liquid through the chute, high-pressure high-speed air with the ejection pressure of 0.8MPa is adopted to carry out air quenching and quenching treatment on the steel slag of the ladle furnace; then collecting the steel slag particles of the ladle furnace after wind quenching treatment by adopting a rotary cooling cylinder which is inclined by 10 degrees relative to the horizontal plane and has the rotating speed of 48r/min, and performing outer cylinder water circulation secondary cooling; and finally, collecting the treated steel slag particles of the ladle furnace.
Example 2
Firstly, adding 0.5 percent of LiF into the steel slag of the ladle furnace, and heating up to 1500 ℃ to ensure that the steel slag of the ladle furnace is in a molten liquid state; then, in the process of flowing out the slag liquid through the chute, high-pressure high-speed air with the ejection pressure of 1.0MPa is adopted to carry out air quenching and quenching treatment on the steel slag of the ladle furnace; then collecting the steel slag particles of the ladle furnace after wind quenching treatment by adopting a rotary cooling cylinder which is inclined by 10 degrees relative to the horizontal plane and has the rotating speed of 48r/min, and performing outer cylinder water circulation secondary cooling; and finally, collecting the treated steel slag particles of the ladle furnace.
The shape and size of the free magnesium oxide in the ladle furnace steel slag obtained in the above examples 1 and 2 were observed using untreated ladle furnace steel slag as a control group, and compared with the free magnesium oxide in the ladle furnace steel slag of the control group, and the results are shown in fig. 1 and 2.
As can be seen from FIGS. 1 and 2, the f-MgO in the untreated control ladle furnace steel slag was distributed in a rhombus shape and an irregular shape at four sides, and the size thereof was in the range of 20 to 45 μm; compared with the steel slag obtained in the examples 1 and 2 of the invention, the f-MgO in the steel slag of the ladle furnace is distributed in irregular particles, and the size of the f-MgO is obviously smaller and is within the range of 2-3.5 μm. Therefore, the treatment method can obviously reduce the size of the f-MgO in the steel slag of the ladle furnace by about one order of magnitude, and the small-size f-MgO has low dead burning or over burning degree and higher hydration activity, can be hydrated and digested when the gelled material is hydrated in early stage, is very favorable for reducing the adverse effect of the f-MgO on the stability of the gelled material and improving the volume stability of the gelled material.
Various corresponding changes and modifications can be made by those skilled in the art based on the above technical solutions and concepts, and all such changes and modifications should be included in the protection scope of the present invention.
Claims (5)
1. A method for refining the size of free magnesium oxide in steel slag of a ladle furnace is characterized by comprising the following steps:
s1, adding a crystal grain growth inhibitor into the steel slag of the ladle furnace, and heating to ensure that the steel slag of the ladle furnace is in molten liquid state;
s2, carrying out air quenching and quenching treatment on the slag liquid by adopting high-pressure and high-speed air in the process of flowing the slag liquid out through the chute;
s3, collecting ladle furnace steel slag particles formed by slag liquid after air quenching treatment by adopting a rotary cooling cylinder;
s4, carrying out water circulation secondary cooling on the steel ladle furnace steel slag particles in the cylinder by using the outer cylinder of the rotary cooling cylinder;
s5, collecting the steel slag particles of the ladle furnace after the secondary cooling treatment of water circulation.
2. The method for refining the size of free magnesium oxide in steel slag of a ladle furnace as claimed in claim 1, wherein the grain growth inhibitor is one or two of LiF and NaF, and the addition amount is 0.2-3%.
3. The method for refining the size of free magnesium oxide in steel slag of ladle furnace as claimed in claim 1, wherein the high pressure high velocity air is generated by an air compressor and laval nozzle device or by an air ejector; the pressure of the high-pressure high-speed air in the air quenching and quenching treatment is 0.6-1.6 MPa.
4. The method for refining the size of free magnesium oxide in ladle furnace steel slag according to claim 1, wherein the rotary cooling drum is disposed at an inclination of 5-15 ° with respect to a horizontal plane.
5. The method for refining the size of free magnesium oxide in steel ladle furnace slag according to claim 1, wherein the rotating speed of the rotary cooling drum is 10-60 r/min.
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| CN202010566714.4A CN111809006B (en) | 2020-06-19 | 2020-06-19 | Method for refining size of free magnesium oxide in steel slag of ladle furnace |
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| CN109517933A (en) * | 2018-12-10 | 2019-03-26 | 中山大学 | A kind of wind quenching fast cooling device of LF furnace refining slag |
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