Boron-magnesium pellet as well as preparation method and application thereof

Abstract

The invention discloses a boron-magnesium pellet and a preparation method and application thereof, and belongs to the technical field of blast furnace ironmaking, the preparation method of the boron-magnesium pellet comprises the following steps: mixing fine iron powder and fine boron-magnesium-iron powder to obtain a mixture; the mass ratio of the fine iron powder to the fine boron-magnesium-iron powder is (5-7): (3-5); bentonite is added into the mixed material for uniform mixing, pelletizing is performed, and green pellets are obtained; the addition amount of the bentonite is 1.5%-2.5% of the mass of the mixed material; and the green pellets are sequentially subjected to screening, drying, preheating, roasting and cooling treatment, and the boron-magnesium pellets are obtained. According to the preparation method of the boron-magnesium pellets, only the fine iron powder, the fine boron-magnesium-iron powder and the bentonite are adopted as raw materials, in the production process, no magnesium additive needs to be additionally added, and the product reduction influence of the pellets is reduced. The content of MgO in the prepared boron-magnesium pellets is high, part of MgO in sintered ore can be replaced, and the quality and yield of the sintered ore can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of blast furnace ironmaking, in particular to boron-magnesium pellets and a preparation method and application thereof. Background Art

[0002] Pelletized ore is an important raw material for blast furnace ironmaking. Its application in steel is equivalent to that of sintered ore. However, the pelletizing process has advantages such as low energy consumption and environmental protection in the production process, so it is regarded as one of the technical measures for energy saving and emission reduction in blast furnace ironmaking.

[0003] "Chain grate-rotary kiln-ring cooler" is a fairly mature pellet production process. With the proposal of my country's "dual carbon" goals, the process production methods of the pellet industry are also constantly exploring, optimizing, and moving forward, developing in the direction of high quality and environmental protection. Therefore, developing a pellet ore with better metallurgical properties and lower energy consumption in the production process will help achieve high-quality development of enterprises and even the industry.

[0004] The preparation method of the existing common magnesium pellets is generally as follows: using iron ore concentrate as raw material, adding a certain proportion of magnesium additives, and then mixing with a certain amount of bentonite, granulating through a ball-making disk, when the green balls have a certain strength, screening 8-16mm qualified particle size pellets into a chain grate for drying, preheating, roasting, cooling, and obtaining magnesium pellets, whose MgO content is generally below 2.5%.

[0005] In the production of magnesium pellets, the solid fuel consumption is difficult to break through, and although the metallurgical properties (low temperature reduction differentiation rate, reduction expansion rate) and other indicators can basically meet the needs of blast furnaces, in the process of pellet production control, a slight deviation in process parameters may cause unqualified compression resistance and poor metallurgical properties. In addition, in the production of magnesium pellets, the existing technology also needs to add a part of magnesium additives to increase the MgO content in the pellets, but the magnesium additives contain a certain amount of impurities, which will affect the grade of the pellets. Summary of the invention

[0006] The object of the present invention is to provide a boron-magnesium pellet and a preparation method and application thereof, so as to solve the problems raised in the above background technology.

[0007] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0008] A method for preparing boron-magnesium pellets, comprising the following steps:

[0009] Mixing iron ore concentrate and boron magnesium iron concentrate to obtain a mixed material; the mass ratio of the iron ore concentrate and the boron magnesium iron concentrate is (5-7):(3-5);

[0010] Adding bentonite to the mixture and mixing well, then adding water to form balls to obtain green balls; the amount of bentonite added is 1.5%-2.5% of the mass of the mixture;

[0011] The green balls are sequentially screened, dried, preheated, roasted and cooled to obtain boron-magnesium pellets.

[0012] Preferably, the added amount of the bentonite is 1.8%-2% of the mass of the mixture.

[0013] Preferably, the diameter of the green balls after screening is 8-16 mm.

[0014] Preferably, the drying method is: placing the green balls at a temperature of 150-250°C, and then raising the temperature to 350-450°C at a rate of 30-35°C / min for dehydration and drying.

[0015] Preferably, the preheating method is: preheating at a temperature of 480-520°C for 1-3 minutes, preheating to 580-620°C for 1-3 minutes, preheating to 680-720°C for 1-3 minutes, preheating to 780-820°C for 2-4 minutes, preheating to 880-920°C for 2-4 minutes, preheating to 980-1020°C for 2-4 minutes, and preheating to 1050-1090°C for 3-5 minutes.

[0016] Preferably, the calcination method is: calcination at a temperature of 1100-1120° C. for 4-5 minutes, heating to 1150-1170° C. for 5-6 minutes, heating to 1170-1230° C. for 16-21 minutes, and cooling to 1140-1200° C. for 4-5 minutes.

[0017] Preferably, the cooling method is: cooling for 12-15 minutes when the temperature drops to 900-1150°C, cooling for 10-12 minutes when the temperature drops to 700-900°C, cooling for 12-15 minutes when the temperature drops to 300-500°C, and naturally cooling for 11-15 minutes when the temperature drops below 150°C.

[0018] Preferably, the cooling method is air cooling.

[0019] Another object of an embodiment of the present invention is to provide a boron-magnesium pellet prepared by the above preparation method.

[0020] Another object of an embodiment of the present invention is to provide an application of the above-mentioned boron-magnesium pellets in blast furnace ironmaking.

[0021] The preparation method of the boron-magnesium pellet provided by the present invention only uses iron concentrate, boron-magnesium-iron concentrate and bentonite as raw materials. In the production process, no additional magnesium additive is added, thereby reducing the degradation effect of the pellets. In addition, the boron in the boron-magnesium-iron concentrate helps to reduce the unit consumption of coal, improve the softening temperature of the pellets, reduce the reduction expansion rate, reduce the roasting temperature, improve the compressive strength of the pellets, and improve the quality of the pellets, thereby helping to improve the permeability of the material column in the blast furnace and reduce the fuel ratio. The boron-magnesium pellets prepared by the present invention have a MgO content of 3.4%-5.5%, which can replace part of the MgO in the sintered ore, and can effectively improve the quality and output of the sintered ore. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] In one embodiment of the present invention, a method for preparing boron-magnesium pellets is provided, which comprises the following steps:

[0024] S1, mixing iron ore concentrate and boron magnesium iron concentrate to obtain a mixed material; the mass ratio of iron ore concentrate and boron magnesium iron concentrate is (5-7): (3-5);

[0025] S2, adding bentonite to the mixture and mixing it with a mixer, then transporting it to a pelletizing bin via a belt, and then transporting it to a pelletizing plate via a belt, adding water to the pelletizing plate to make balls, and obtaining green balls with a diameter of 1-20 mm; the amount of bentonite added is 1.5%-2.5% of the mass of the mixture, preferably 1.8%-2%;

[0026] S3. The raw balls are sequentially screened, dried, preheated, roasted and cooled to obtain boron-magnesium pellets.

[0027] In a preferred embodiment of the present invention, the diameter of the green balls after screening is 8-16 mm.

[0028] In practical applications, the screening method is as follows: the large ball roller screen returns the raw balls with a particle size larger than 16 mm to the pelletizing bin through the wet return system to re-participate in the pelletizing process; the small ball roller screen returns the raw balls with a particle size smaller than 8 mm and powdered materials through the wet return system to re-participate in the pelletizing process; the screened 8-16 mm raw balls enter the chain grate for drying.

[0029] In a preferred embodiment of the present invention, the drying method is: placing the green balls at a temperature of 150-250°C, and then raising the temperature to 350-450°C at a rate of 30-35°C / min for dehydration and drying. The entire drying process takes 8-10 minutes.

[0030] In a preferred embodiment of the present invention, the preheating method is: preheating for 1-3 minutes when the hood temperature is 480-520℃, preheating for 1-3 minutes when the temperature is increased to 580-620℃, preheating for 1-3 minutes when the temperature is increased to 680-720℃, preheating for 1-3 minutes when the temperature is increased to 780-820℃, preheating for 2-4 minutes when the temperature is increased to 880-920℃, preheating for 2-4 minutes when the temperature is increased to 980-1020℃, preheating for 2-4 minutes when the temperature is increased to 1050-1090℃, and preheating for 3-5 minutes when the temperature at the highest point of the bellows reaches 480-520℃.

[0031] In a preferred embodiment of the present invention, the calcination method is: calcination at a temperature of 1100-1120°C for 4-5 minutes, heating to 1150-1170°C for 5-6 minutes, heating to 1170-1230°C for 16-21 minutes, and cooling to 1140-1200°C for 4-5 minutes.

[0032] In a preferred embodiment of the present invention, the cooling method is: using three blowers for cooling on a ring cooler, cooling for 12-15 minutes when the temperature drops to 900-1150°C, cooling for 10-12 minutes when the temperature drops to 700-900°C, cooling for 12-15 minutes when the temperature drops to 300-500°C, and naturally cooling for 11-15 minutes when the temperature drops below 150°C.

[0033] The composition and indicators of the boron-magnesium pellets prepared in the embodiment of the present invention are: B2O3 comprehensive grade 1%-1.7%, MgO 3.4%-5.5%, TFe 60%-62%, SiO2 4%-5%, CaO ≥ 0.7%, Al2O3 ≤ 1%, and compressive strength (10-16mm particle size) ≥ 2500N / ball.

[0034] The following embodiments are some specific implementation cases of the present invention in practical applications, but are not limited thereto.

[0035] Among them, the iron ore concentrate used in the embodiment of the present invention is the commercially available Chengde 66% single magnetite concentrate, and the boron-magnesium-iron concentrate is the commercially available Dandong boron-magnesium-iron concentrate; specifically, the composition and indicators of the iron ore concentrate and the boron-magnesium-iron concentrate are shown in Table 1.

[0036] Table 1

[0037] raw material TFe <![CDATA[SiO2]]> <![CDATA[TiO2]]> granularity Moisture S P <![CDATA[Al2O3]]> CaO MgO <![CDATA[B2O3]]> Iron powder 66.04％ 5.38％ 0.432％ 62.7μm 7.6％ 0.07％ 0.024％ 0.86％ 0.57％ 0.6％ 0 Boron magnesium iron concentrate 54.08％ 4.23％ 0.34％ 75.06μm 11.56％ 1.1％ 0.03％ 0.3％ 0.48％ 9,21％ 3.6％

[0038] Example 1: This example provides a method for preparing boron-magnesium pellets, which comprises the following steps:

[0039] S1, 5kg of iron ore concentrate and 5kg of boron magnesium iron concentrate are mixed to obtain a mixed material;

[0040] S2, add 0.18kg of bentonite to the above 10kg of the mixture and mix it with a mixer, then transport it to the ball making bin via a belt, and then transport it to the ball making plate via a belt, add an appropriate amount of water to the ball making plate to make balls, and obtain green balls with a diameter of 1-20mm;

[0041] S3. After screening the raw balls, they are transported to the chain grate for drying and preheating, then transported to the rotary kiln for roasting, and then transported to the ring cooler for cooling to obtain boron-magnesium pellets. The screening method is as follows: the large ball roller screen returns the raw balls with a particle size larger than 16 mm to the pelletizing bin through the wet return system to re-participate in the pelletizing, and the small ball roller screen returns the raw balls and powdered materials with a particle size smaller than 8 mm through the wet return system to re-participate in the pelletizing; the screened 8-16 mm raw balls enter the chain grate for drying. The drying method is as follows: the raw balls are placed at a temperature of 200°C, and then heated to 400°C at a rate of 32°C / min for dehydration and drying. The entire drying process takes 9 minutes. The preheating method is: preheating for 1 minute when the hood temperature is 500℃, preheating for 1 minute when the temperature rises to 600℃, preheating for 1 minute when the temperature rises to 700℃, preheating for 2 minutes when the temperature rises to 800℃, preheating for 2 minutes when the temperature rises to 900℃, preheating for 2 minutes when the temperature rises to 1000℃, preheating for 3 minutes when the temperature rises to 1070℃, and the highest point temperature of the bellows reaches 500℃. The roasting method is: roasting for 4 minutes when the temperature is 1100℃, roasting for 5 minutes when the temperature rises to 1170℃, roasting for 16 minutes when the temperature rises to 1230℃, and roasting for 4 minutes when the temperature drops to 1200℃. The cooling method is: using three blowers on the ring cooler for cooling, cooling for 12 minutes when the temperature drops to 1150℃, cooling for 10 minutes when the temperature drops to 900℃, cooling for 12 minutes when the temperature drops to 500℃, and naturally cooling for 11 minutes when the temperature drops below 150℃.

[0042] The composition and indicators of the boron-magnesium pellets prepared in the above embodiment 1 are as follows: B2O3 comprehensive grade 1.5%-1.7%, MgO≥5.5%, TFe≥60%, SiO2≤5%, CaO≥0.7%, Al2O3≤1%, and compressive strength (10-16mm particle size) ≥2500N / ball.

[0043] Example 2: This example provides a method for preparing boron-magnesium pellets, which comprises the following steps:

[0044] S1, 7kg of iron ore concentrate and 3kg of boron magnesium iron concentrate are mixed to obtain a mixed material;

[0045] S2, add 0.18kg of bentonite to the above 10kg of the mixture and mix it with a mixer, then transport it to the ball making bin via a belt, and then transport it to the ball making plate via a belt, add an appropriate amount of water to the ball making plate to make balls, and obtain green balls with a diameter of 1-20mm;

[0046] S3. After screening the raw balls, they are transported to the chain grate for drying and preheating, then transported to the rotary kiln for roasting, and then transported to the ring cooler for cooling to obtain boron-magnesium pellets. The screening method is as follows: the large ball roller screen returns the raw balls with a particle size larger than 16 mm to the pelletizing bin through the wet return system to re-participate in the pelletizing, and the small ball roller screen returns the raw balls and powdered materials with a particle size smaller than 8 mm through the wet return system to re-participate in the pelletizing; the screened 8-16 mm raw balls enter the chain grate for drying. The drying method is as follows: the raw balls are placed at a temperature of 200°C, and then heated to 400°C at a rate of 32°C / min for dehydration and drying. The entire drying process takes 9 minutes. The preheating method is: preheating for 1 minute when the hood temperature is 500℃, preheating for 1 minute when the temperature rises to 600℃, preheating for 1 minute when the temperature rises to 700℃, preheating for 2 minutes when the temperature rises to 800℃, preheating for 2 minutes when the temperature rises to 900℃, preheating for 2 minutes when the temperature rises to 1000℃, preheating for 3 minutes when the temperature rises to 1070℃, and the highest point temperature of the bellows reaches 500℃. The roasting method is: roasting for 4 minutes when the temperature is 1100℃, roasting for 5 minutes when the temperature rises to 1170℃, roasting for 16 minutes when the temperature rises to 1230℃, and roasting for 4 minutes when the temperature drops to 1200℃. The cooling method is: using three blowers on the ring cooler for cooling, cooling for 12 minutes when the temperature drops to 1150℃, cooling for 10 minutes when the temperature drops to 900℃, cooling for 12 minutes when the temperature drops to 500℃, and naturally cooling for 11 minutes when the temperature drops below 150℃.

[0047] The composition and indicators of the boron-magnesium pellets obtained in the above embodiment 2 are as follows: B2O3 comprehensive grade 1%, MgO≥3.4%, TFe≥62%, SiO2≤5%, CaO≥0.7%, Al2O3≤1%, and compressive strength (10-16mm particle size) ≥2500N / ball.

[0048] Example 3: This example provides a method for preparing boron-magnesium pellets, which comprises the following steps:

[0049] S1, 6kg of iron ore concentrate and 4kg of boron magnesium iron concentrate are mixed to obtain a mixed material;

[0050] S2, add 0.15kg of bentonite to the above 10kg of the mixture and mix it with a mixer, then transport it to the ball making bin via a belt, and then transport it to the ball making plate via a belt, add an appropriate amount of water to the ball making plate to make balls, and obtain green balls with a diameter of 1-20mm;

[0051] S3. After screening the raw balls, they are transported to the chain grate for drying and preheating, then transported to the rotary kiln for roasting, and then transported to the ring cooler for cooling to obtain boron-magnesium pellets. The screening method is as follows: the large ball roller screen returns the raw balls with a particle size larger than 16 mm to the pelletizing bin through the wet return system to re-participate in the pelletizing, and the small ball roller screen returns the raw balls and powdered materials with a particle size smaller than 8 mm through the wet return system to re-participate in the pelletizing; the screened 8-16 mm raw balls enter the chain grate for drying. The drying method is as follows: the raw balls are placed at a temperature of 150°C, and then the temperature is raised to 350°C at a rate of 30°C / min for dehydration and drying. The entire drying process takes 10 minutes. The preheating method is: preheating for 3 minutes when the hood temperature is 480℃, preheating for 3 minutes when the temperature rises to 580℃, preheating for 3 minutes when the temperature rises to 680℃, preheating for 3 minutes when the temperature rises to 780℃, preheating for 4 minutes when the temperature rises to 880℃, preheating for 4 minutes when the temperature rises to 980℃, preheating for 5 minutes when the temperature rises to 1050℃, and the highest point temperature of the bellows reaches 480℃. The roasting method is: roasting for 5 minutes when the temperature is 1100℃, roasting for 6 minutes when the temperature rises to 1150℃, roasting for 21 minutes when the temperature rises to 1170℃, and roasting for 5 minutes when the temperature drops to 1140℃. The cooling method is: using three blowers on the ring cooler for cooling, cooling for 15 minutes when the temperature drops to 900℃, cooling for 12 minutes when the temperature drops to 700℃, cooling for 15 minutes when the temperature drops to 300℃, and naturally cooling for 15 minutes when the temperature drops below 150℃.

[0052] Example 4: This example provides a method for preparing boron-magnesium pellets, which comprises the following steps:

[0053] S1, 5.5kg of iron ore concentrate and 4.5kg of boron magnesium iron concentrate are mixed to obtain a mixed material;

[0054] S2, add 0.25kg of bentonite to the above 10kg of the mixture and mix it with a mixer, then transport it to the ball making bin via a belt, and then transport it to the ball making plate via a belt, add an appropriate amount of water to the ball making plate to make balls, and obtain green balls with a diameter of 1-20mm;

[0055] S3. After screening the raw balls, they are transported to the chain grate for drying and preheating, then transported to the rotary kiln for roasting, and then transported to the ring cooler for cooling to obtain boron-magnesium pellets. The screening method is: the large ball roller screen returns the raw balls with a particle size larger than 16mm to the pelletizing bin through the wet return system to re-participate in the pelletizing, and the small ball roller screen returns the raw balls and powdered materials with a particle size smaller than 8mm through the wet return system to re-participate in the pelletizing; the screened 8-16mm raw balls enter the chain grate for drying. The drying method is: place the raw balls at a temperature of 250℃, and then increase the temperature to 450℃ at a rate of 35℃ / min for dehydration and drying. The entire drying process takes 8 minutes. The preheating method is: preheating for 1 minute when the hood temperature is 520℃, preheating for 1 minute when the temperature rises to 620℃, preheating for 1 minute when the temperature rises to 720℃, preheating for 2 minutes when the temperature rises to 820℃, preheating for 2 minutes when the temperature rises to 920℃, preheating for 2 minutes when the temperature rises to 1020℃, preheating for 3 minutes when the temperature rises to 1090℃, and the highest point temperature of the bellows reaches 520℃. The roasting method is: roasting for 4 minutes when the temperature is 1120℃, roasting for 5 minutes when the temperature rises to 1170℃, roasting for 16 minutes when the temperature rises to 1230℃, and roasting for 4 minutes when the temperature drops to 1200℃. The cooling method is: using three blowers on the ring cooler for cooling, cooling for 12 minutes when the temperature drops to 1150℃, cooling for 10 minutes when the temperature drops to 900℃, cooling for 12 minutes when the temperature drops to 500℃, and naturally cooling for 12 minutes when the temperature drops below 150℃.

[0056] Example 5: This example provides a method for preparing boron-magnesium pellets, which comprises the following steps:

[0057] S1, 6.5kg of iron ore concentrate and 3.5kg of boron magnesium iron concentrate are mixed to obtain a mixed material;

[0058] S2, add 0.2kg of bentonite to the above 10kg of the mixture and mix it with a mixer, then transport it to the ball making bin via a belt, and then transport it to the ball making plate via a belt, add an appropriate amount of water to the ball making plate to make balls, and obtain green balls with a diameter of 1-20mm;

[0059] S3. After screening the raw balls, they are transported to the chain grate for drying and preheating, then transported to the rotary kiln for roasting, and then transported to the ring cooler for cooling to obtain boron-magnesium pellets. The screening method is as follows: the large ball roller screen returns the raw balls with a particle size larger than 16 mm to the pelletizing bin through the wet return system to re-participate in the pelletizing, and the small ball roller screen returns the raw balls and powdered materials with a particle size smaller than 8 mm through the wet return system to re-participate in the pelletizing; the screened 8-16 mm raw balls enter the chain grate for drying. The drying method is as follows: the raw balls are placed at a temperature of 200°C, and then heated to 400°C at a rate of 33°C / min for dehydration and drying. The entire drying process takes 10 minutes. The preheating method is: preheating for 2 minutes when the hood temperature is 500℃, preheating for 2 minutes when the temperature rises to 600℃, preheating for 2 minutes when the temperature rises to 700℃, preheating for 3 minutes when the temperature rises to 800℃, preheating for 3 minutes when the temperature rises to 900℃, preheating for 3 minutes when the temperature rises to 1010℃, preheating for 4 minutes when the temperature rises to 1080℃, and the highest point temperature of the bellows reaches 510℃. The roasting method is: roasting for 4 minutes when the temperature is 1110℃, roasting for 6 minutes when the temperature rises to 1160℃, roasting for 20 minutes when the temperature rises to 1210℃, and roasting for 5 minutes when the temperature drops to 1160℃. The cooling method is: using three blowers on the ring cooler for cooling, cooling for 13 minutes when the temperature drops to 1000℃, cooling for 11 minutes when the temperature drops to 800℃, cooling for 14 minutes when the temperature drops to 400℃, and naturally cooling for 12 minutes when the temperature drops below 150℃.

[0060] In the embodiment of the present invention, no additional magnesium additive is required in the preparation of boron-magnesium pellets, which reduces the degradation effect of the pellets. Since boron-magnesium iron concentrate contains boron, its roasting temperature and coal consumption are reduced accordingly; through experiments, in the process of preparing boron-magnesium pellets in the embodiment of the present invention, the unit consumption of solid fuel used is reduced by 0.92-1.03kg / ton, and the highest roasting temperature is 1230℃, which is 40-60℃ lower than the traditional ordinary pellets, which can reduce CO2, SO2, NO x Equal emissions; and the average compression resistance is increased by more than 200N / piece, and no other adverse factors are found in the subsequent preheating, roasting and cooling processes. Moreover, "low temperature" roasting prolongs the ring formation cycle of the rotary kiln, and the operation control in the production process is easier to control. In addition, the MgO content of the boron-magnesium pellets prepared in the embodiment of the present invention reaches 3.4%-5.5%, which can replace part of the MgO in the sintered ore, and can effectively improve the quality and output of the sintered ore.

[0061] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing boron-magnesium pellets, characterized in that: The following steps are involved: Mixing iron ore concentrate and boron magnesium iron concentrate to obtain a mixed material; the mass ratio of the iron ore concentrate and the boron magnesium iron concentrate is (5-7):(3-5); Adding bentonite to the mixture and mixing well, then adding water to form balls to obtain green balls; the amount of bentonite added is 1.5%-2.5% of the mass of the mixture; The green balls are sequentially screened, dried, preheated, roasted and cooled to obtain boron-magnesium pellets.

2. The method for preparing boron-magnesium pellets according to claim 1, characterized in that: The added amount of the bentonite is 1.8%-2% of the mass of the mixed material.

3. The method for preparing boron-magnesium pellets according to claim 1, characterized in that: The diameter of the green balls after screening is 8-16mm.

4. The method for preparing boron-magnesium pellets according to claim 1, characterized in that: The drying method is: placing the green balls at a temperature of 150-250°C, and then raising the temperature to 350-450°C at a rate of 30-35°C / min for dehydration and drying.

5. The method for preparing boron-magnesium pellets according to claim 1, characterized in that: The preheating method is: preheat for 1-3 minutes at 480-520℃, preheat for 1-3 minutes at 580-620℃, preheat for 1-3 minutes at 680-720℃, preheat for 1-3 minutes at 780-820℃, preheat for 2-4 minutes at 880-920℃, preheat for 2-4 minutes at 980-1020℃, and preheat for 3-5 minutes at 1050-1090℃.

6. The method for preparing boron-magnesium pellets according to claim 1 or 5, characterized in that: The roasting method is as follows: roasting at a temperature of 1100-1120° C. for 4-5 minutes, heating to 1150-1170° C. for 5-6 minutes, heating to 1170-1230° C. for 16-21 minutes, and cooling to 1140-1200° C. for 4-5 minutes.

7. The method for preparing boron-magnesium pellets according to claim 6, characterized in that: The cooling method is: cooling for 12-15 minutes when the temperature drops to 900-1150°C, cooling for 10-12 minutes when the temperature drops to 700-900°C, cooling for 12-15 minutes when the temperature drops to 300-500°C, and naturally cooling for 11-15 minutes when the temperature drops below 150°C.

8. The method for preparing boron-magnesium pellets according to claim 7, characterized in that: The cooling method is air cooling.

9. Boron-magnesium pellets prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the boron-magnesium pellets as claimed in claim 9 in blast furnace ironmaking.