TW202400812A - Preparation method for lumpy desulfurizing agent avoiding the problem that the content of sulfur in molten steel cannot be reduced effectively because the desulfurizing agent is sucked by a dust collecting apparatus - Google Patents

Abstract

A preparation method for a lumpy desulfurizing agent includes the following steps: performing a hydration reaction on a first component containing calcium oxide with a particle size of 1.4mm or less with water to convert a portion of calcium oxide into calcium hydroxide to obtain a mixture containing calcium hydroxide and calcium oxide; and drying the mixture to remove the water to obtain a dry product; mixing the dry product with a second component containing aluminum dross, and performing pressurizing and molding. The lumpy desulfurizing agent prepared by using the preparation method of this invention retains its original form after storage and has good molding stability, which makes it easy to use and has good operability when being used in a steelmaking process. Meanwhile, the problem of poor desulfurization efficiency caused by a fact that the content of sulfur in molten steel can not be reduced effectively because the desulfurizing agent is sucked in by a dust collecting apparatus of a steelmaking device can be avoided when the desulfurizing agent is put into the steelmaking device.

Description

Preparation method of block desulfurizer

The present invention relates to a method for preparing a removal agent, in particular to a method for preparing a massive desulfurizer.

As the uses of steel become more and more widespread, the requirements for the performance of steel are also increasing day by day. One of the key technologies to improve the performance of steel is to improve the purity of molten steel, especially to reduce the sulfur content in the molten steel. Therefore, How to reduce the sulfur content in molten steel is a widely studied topic. Generally speaking, most methods to reduce the sulfur content in molten steel are by using desulfurizers.

Mainland China Patent Announcement No. 1074685 discloses a desulfurizer that can be used to remove H ₂ S from gaseous or liquid materials, and the preparation method of the desulfurizer includes mixing iron source powder, calcium source powder and structural aids , and then perform steps such as adding water, stirring, shaping, drying, roasting and cooling in sequence. The iron source powder is, for example, iron oxide powder, iron hydroxide powder, or iron nitrate powder. The calcium source powder is, for example, calcium oxide, calcium hydroxide, calcium bicarbonate, or calcium carbonate. The structural aids include alumina, silica, bentonite, kaolin, or bentonite.

Although the desulfurizer in this patent can be molded, generally speaking, the desulfurizer may not be sold or used immediately after production. Therefore, whether the desulfurizer will disintegrate or become powder after storage The problem of molding stability caused by desulfurization is something that producers need to consider. The reason why they need to be considered is because when the desulfurizer has poor molding stability, it will cause inconvenience and problems in the steelmaking process. The problem of poor operability arises. At the same time, due to poor molding stability, it is easy to disintegrate and produce powder. As a result, when put into steelmaking equipment, it is easily sucked into the dust collection device of the steelmaking equipment, resulting in the inability to effectively reduce the dust. The sulfur content in the molten steel causes the problem of poor desulfurization efficiency.

Therefore, the object of the present invention is to provide a method for preparing a block desulfurizer.

Therefore, the preparation method of the block desulfurizer of the present invention includes: performing a hydration reaction between the first component including calcium oxide with a particle size of 1.4 mm or less and water, so that part of the calcium oxide is converted into calcium hydroxide, and Obtain a mixture containing calcium hydroxide and calcium oxide; dry the mixture to remove moisture to obtain a dry product; mix the dry product with a second component including aluminum slag, and perform a pressure forming process, wherein, The aluminum slag includes aluminum oxide.

The effect of the present invention is: through the design of the above-mentioned process, especially the design of converting calcium oxide into calcium hydroxide, the block desulfurizer prepared by the preparation method of the block desulfurizer of the present invention can be used in an environment containing water vapor. After being stored in a medium for a period of time, calcium oxide will not easily expand due to the presence of water vapor, leading to disintegration and powdering. As a result, it still retains its original shape and has good molding stability, so that it can be used for refining. In the process of making steel, it is easy to use and has good operability, and because there will be no powdering due to disintegration after a period of storage, it can avoid being used by the steelmaking equipment when it is put into the steelmaking equipment. The dust collection device sucks in the dust and cannot effectively reduce the sulfur content in the molten steel, resulting in the problem of poor desulfurization efficiency.

The preparation method of the block desulfurizer of the present invention includes performing a hydration reaction between the first component including calcium oxide with a particle size of 1.4 mm or less and water, so that part of the calcium oxide is converted into calcium hydroxide, so as to obtain a calcium oxide containing hydroxide. A mixture of calcium and calcium oxide; drying the mixture to remove moisture to obtain a dry product; mixing the dry product with a second component including aluminum slag, and performing a pressure forming process, wherein the aluminum slag includes Aluminum trioxide.

The present invention will be described in detail below.

Part of the calcium oxide is converted into calcium hydroxide through the hydration reaction. There is an appropriate amount of calcium oxide in the block desulfurizer prepared by the method for preparing the block desulfurizer of the present invention. Therefore, when the block desulfurizer is After the agent is stored in an environment containing water vapor for a period of time, it is not easy for calcium oxide to expand significantly when exposed to water vapor, leading to disintegration and powdering. As a result, it still retains its original shape and has good molding. Stability. In some embodiments of the present invention, the temperature of the hydration reaction ranges from 25°C to 150°C, and the time ranges from 10 minutes to 180 minutes.

In some embodiments of the present invention, the first component further includes refining slag, and the refining slag includes calcium oxide. Since the refining slag is obtained through recycling and the refining slag includes calcium oxide, the refining slag can be used to replace natural calcium oxide and reduce the amount of natural calcium oxide in the first component. By using such This method helps the preparation method of the block desulfurizer of the present invention to achieve the advantages of waste reuse, net-zero emissions and low manufacturing cost. The refining slag is, for example, but not limited to, refining slag from a steel mill.

In some embodiments of the present invention, the weight ratio of the calcium oxide, the water and the refining slag ranges from 1:0.45 to 2: greater than 0 and less than 1.5.

The moisture in the mixture is removed through the drying process, so that the moisture content of the dried product is low, so that when there is moisture in the dried product, the moisture reacts with the aluminum slag in the second component to generate ammonia gas with a pungent smell, And there is the problem of olfactory discomfort.

Since in the past desulfurizers, natural aluminum oxide is used, which has the problem of high cost and consumption of natural resources. Therefore, in order to reduce the cost of previous desulfurizers and reduce the use of natural resources, this paper In the invention, since the aluminum slag is obtained through recycling and the aluminum slag contains aluminum oxide, the aluminum slag can be used to replace natural aluminum oxide. In this way, it helps to reduce waste reuse and net zero emissions. The aluminum slag is, for example, but not limited to, aluminum slag from an aluminum smelter. In some embodiments of the present invention, based on the total amount of the second component being 100wt%, the amount of aluminum slag ranges from 32wt% or more. In some embodiments of the present invention, the calcium oxide content in the block desulfurizer ranges from 2wt% to 18wt%, and the aluminum slag content ranges from 20wt% to 30wt%.

In some embodiments of the invention, the second component further includes an adhesive. The purpose of the adhesive is to allow the components of the second component to agglomerate together. The adhesive may be, but is not limited to, cement, calcium hydroxide or zinc stearate. In some embodiments of the present invention, the adhesive is selected from cement, calcium hydroxide, zinc stearate, or any combination of the above. In some embodiments of the present invention, based on the total amount of the second component being 100wt%, the amount of the adhesive ranges from greater than 0wt% to less than 31wt%. In some embodiments of the present invention, based on the total amount of the massive desulfurizer being 100wt%, the content of the calcium oxide in the massive desulfurizer ranges from 2wt% to 18wt%, and the content of the aluminum slag is The content range is 20wt% to 30wt%, and the content range of the adhesive is greater than 0wt% and less than 20wt%.

In some embodiments of the present invention, the second component further includes refining slag. The purpose of this refining slag is to reduce calcium oxide consumption. The refining slag is, for example, but not limited to, refining slag from a steel mill. In some embodiments of the present invention, based on the total amount of the second component being 100wt%, the amount of the refining slag ranges from greater than 0wt% to less than 53wt%. In some embodiments of the present invention, based on the total amount of the massive desulfurizer being 100wt%, the content of the calcium oxide in the massive desulfurizer ranges from 2wt% to 18wt%, and the content of the aluminum slag is The content range is 20wt% to 30wt%, and the content range of the refining slag is greater than 30wt% and less than 40wt%.

In some embodiments of the present invention, the pressure forming process ranges from 8 kg/cm ² to 15 kg/cm ² and the time ranges from 2 seconds to 90 seconds.

The present invention will be further described with reference to the following examples, but it should be understood that these examples are only for illustration and should not be construed as limitations on the implementation of the present invention.

Example 1

Step (a): Mix the first component including 31.5 grams of calcium oxide with a particle size of less than 0.27mm (brand: CHONEYE PURE CHEMICAL) and 36 grams of refining slag with 14.2 grams of water, wherein the calcium oxide The weight ratio of the water and the refining slag is 1:0.45:1.15, and the refining slag comes from a Taiwan steelmaking plant and contains 55.4wt% calcium oxide (CaO), 4.8wt% magnesium oxide (MgO), 2.7 wt% aluminum oxide, 27.2wt% silica, 7.0wt% calcium fluoride (CaF ₂ ), 1.9wt% iron monoxide (FeO), 0.4wt% manganese monoxide (MnO) , and 0.6wt% sulfur. Then, a hydration reaction was performed at 25° C. for 30 minutes to obtain a mixture containing calcium hydroxide and calcium oxide.

Step (b): Place the mixture in an oven set at a temperature of 110° C. for 60 minutes to dry to remove moisture, and obtain 74.6 grams of dry matter.

Step (c): Introduce the dried product and the second component including 10 grams of calcium hydroxide (as a binder) and 22.5 grams of aluminum slag into a molding equipment (model: PM-20) for mixing, and Pressure forming treatment was carried out for 2 seconds at a pressure of 15kg/ ^cm2 to obtain an ingot-shaped desulfurizer with a length of 4.5cm, a width of 3.8cm and a height of 6cm. The aluminum slag came from a Taiwan aluminum smelting plant and contained 4.4wt% magnesium oxide (MgO), 73.6wt% aluminum oxide, 5.2wt% metallic aluminum, 0.3wt% silicon dioxide, 0.2wt% potassium oxide (K ₂ O), and 16.3wt% of aluminum nitride (AlN).

Examples 2 to 4

The preparation methods of Examples 2 to 4 are substantially the same as those of Example 1, and the main difference is that in Example 2, there is no calcium hydroxide. In Examples 3 to 4, the calcium hydroxide in Example 1 was replaced with zinc stearate (brand: CHONEYE PURE CHEMICAL) and cement (brand: Nanxing) in sequence, and the dosages were 10 grams and 10 grams.

Example 5

Step (a): Mix the first component including 31.5 grams of calcium oxide with a particle size of less than 0.27mm (brand: CHONEYE PURE CHEMICAL) and 36 grams of refining slag with 14.2 grams of water, wherein the calcium oxide The weight ratio of the water and the refining slag is 1:0.45:1.15, and the refining slag comes from a Taiwan steelmaking plant and contains 55.4wt% calcium oxide (CaO), 4.8wt% magnesium oxide (MgO), 2.7 wt% aluminum oxide, 27.2wt% silica, 7.0wt% calcium fluoride (CaF ₂ ), 1.9wt% iron monoxide (FeO), 0.4wt% manganese monoxide (MnO) , and 0.6wt% sulfur. Then, a hydration reaction was performed at 25° C. for 30 minutes to obtain a mixture containing calcium hydroxide and calcium oxide.

Step (b): Place the mixture in an oven with a temperature set to 110°C for 60 minutes to dry, to obtain 74.6 grams of dried product.

Step (c): The dry material and the second component including 10 grams of calcium hydroxide (as a binder) and 22.5 grams of aluminum slag are introduced into a molding equipment (model: PM-20) for mixing, and Pressure forming treatment was carried out for 2 seconds at a pressure of 15kg/ ^cm2 to obtain an ingot-shaped desulfurizer with a length of 4.5cm, a width of 3.8cm and a height of 6cm. The aluminum slag came from a Taiwan aluminum smelting plant and contained 4.4wt% magnesium oxide (MgO), 73.6wt% aluminum oxide, 5.2wt% metallic aluminum, 0.3wt% silica, 0.2wt% potassium oxide (K ₂ O), and 16.3wt% of aluminum nitride (AlN).

Examples 6 to 13

The preparation methods of Examples 6 to 13 are substantially the same as those of Example 5, and the main difference lies in changing the particle size of the calcium oxide or/and the dosage ratio of the water. See Table 1 and Table 2.

Example 14

Step (a): Mix 31.5 grams of calcium oxide with a particle size of less than 1.4 mm and 31.5 grams of water. Then, a hydration reaction was performed at 25° C. for 90 minutes to obtain a mixture containing calcium hydroxide and calcium oxide.

Step (b): Place the mixture in an oven with a temperature set to 110° C. for 60 minutes to dry, to obtain 40.5 grams of dried product.

Step (c): Introduce the dried product and the second component including 10 grams of calcium hydroxide (as a binder), 22.5 grams of aluminum slag and 36 grams of refining slag into a molding equipment (model: PM-20 ), and perform a pressure molding process at a pressure of 15kg/ ^cm2 for 2 seconds to obtain an ingot-shaped desulfurizer with a length of 4.5cm, a width of 3.8cm and a height of 6cm. The aluminum slag comes from Taiwan. Aluminum smelter, and contains 4.4wt% magnesium oxide (MgO), 73.6wt% aluminum oxide, 5.2wt% metallic aluminum, 0.3wt% silicon dioxide, 0.2wt% potassium oxide (K ₂ O ), and 16.3wt% aluminum nitride (AlN), and the refining slag comes from a Taiwan steelmaking plant and contains 55.4wt% calcium oxide (CaO), 4.8wt% magnesium oxide (MgO), 2.7wt% Aluminum trioxide, 27.2wt% silica, 7.0wt% calcium fluoride (CaF ₂ ), 1.9wt% iron monoxide (FeO), 0.4wt% manganese monoxide (MnO), and 0.6 wt% sulfur.

Comparative Example 1 Tablet Desulfurizer

Introduce 31.5 grams of calcium oxide with a particle size of less than 0.27mm, 36 grams of refining slag, 10 grams of calcium hydroxide (as a binder) and 22.5 grams of aluminum slag into a molding equipment (model: PM-20) Mix and perform pressure molding treatment at a pressure of 15kg/ ^cm2 for 2 seconds to obtain a tablet-shaped desulfurizer with a length of 4.5cm, a width of 3.8cm and a height of 6cm. Among them, the refining slag comes from a Taiwan steelmaking plant and contains 55.4wt% calcium oxide (CaO), 4.8wt% magnesium oxide (MgO), 2.7wt% aluminum oxide, 27.2wt% silica, 7.0wt% calcium difluoride (CaF ₂ ), 1.9wt% iron monoxide (FeO), 0.4wt% manganese monoxide (MnO), and 0.6wt% sulfur, and the aluminum slag comes from Taiwan aluminum smelting factory, and contains 4.4wt% magnesium oxide (MgO), 73.6wt% aluminum oxide, 5.2wt% metallic aluminum, 0.33wt% silicon dioxide, 0.17wt% potassium oxide (K ₂ O), and 16.28wt% aluminum nitride (AlN).

Comparative Examples 2 to 4

The preparation methods of Comparative Examples 2 to 4 are substantially the same as those of Comparative Example 1, and the main difference is that in Comparative Example 2, there is no calcium hydroxide. In Comparative Examples 3 to 4, the calcium hydroxide in Comparative Example 1 was replaced with zinc stearate and cement in sequence, and the dosages were 10 grams and 10 grams respectively.

Comparative Examples 5 to 6

The preparation methods of Comparative Examples 5 to 6 are substantially the same as the preparation methods of Comparative Example 1, and the main difference is that in Comparative Examples 5 to 6, the amounts of calcium hydroxide used are 15 grams and 20 grams respectively.

Comparative Examples 7 to 8

The preparation methods of Comparative Examples 7 to 8 are approximately the same as those of Example 5, and the main difference lies in changing the particle size of the calcium oxide or/and the dosage ratio of the water, see Table 3.

Evaluation items

Molding stability: Leave the tablet-shaped desulfurizers of Examples 1 to 14 and the tablet-shaped desulfurizers of Comparative Examples 1 to 8 for a period of time in an atmospheric environment with a temperature of 25°C and a relative humidity of 60% to 99%. , and apply an external force to observe whether there is disintegration or powdering.

Table 1 Example 1 2 3 4 5 6 7 first component calcium oxide Dosage 31.5 31.5 31.5 31.5 31.5 31.5 31.5 Particle size (mm) 0.27 or less 0.27 or less water 14.2 14.2 14.2 14.2 14.2 31.5 63 Refining slag 36 36 36 36 36 36 36 Weight ratio of calcium oxide, water and refining slag 1:0.45:1.15 1:0.45:1.15 1:1:1.15 1:2:1.15 hydration reaction Temperature(℃) 25 25 25 25 25 25 25 time (minutes) 30 30 30 30 30 30 30 mixture Calcium hydroxide (g) 29.2 29.2 29.2 29.2 29.2 32.9 37.8 Calcium oxide(g) 9.4 9.4 9.4 9.4 9.4 6.6 2.9 dry matter 74.6 74.6 74.6 74.6 74.6 75.5 76.7 second component Aluminum dross 22.5 22.5 22.5 22.5 22.5 22.5 22.5 Refining slag 0 0 0 0 0 0 0 calcium hydroxide 10 0 0 0 10 10 10 hard fatty acid 0 0 10 0 0 0 0 cement 0 0 0 10 0 0 0 Sticky desulfurizer (wt%) Refining slag 33.6 37.1 33.6 33.6 33.6 33.3 33.0 Aluminum dross 21.0 23.2 21.0 21.0 21.0 20.8 20.6 Adhesive 9.3 0 9.3 9.3 9.3 9.3 9.2 calcium oxide 8.8 9.7 8.8 8.8 8.8 6.1 2.6 calcium hydroxide 27.3 30.0 27.3 27.3 27.3 30.5 34.6 Forming stability No disintegration or powdering after 180 days of standing No disintegration or powdering after 90 days of resting

Table 2 Unit: Gram Example 8 9 10 11 12 13 14 first component calcium oxide Dosage 31.5 31.5 31.5 31.5 31.5 31.5 31.5 Particle size(mm) Greater than 0.27 and less than 1.18 Greater than 1.18 and less than 1.4 1.4 or less water 14.2 31.5 63 14.2 31.5 63 31.5 Refining slag 36 36 36 36 36 36 0 Weight ratio of calcium oxide, water and refining slag 1:0.45:1.15 1:1:1.15 1:2:1.15 1:0.45:1.15 1:1:1.15 1:2:1.15 1:1:0 hydration reaction Temperature(℃) 25 25 25 25 25 25 25 time (minutes) 30 30 30 30 30 30 30 mixture Calcium hydroxide (g) twenty one 32.9 37.8 16.9 32.9 37.8 37 Calcium oxide(g) 15.6 6.6 2.9 18.7 6.6 2.9 3.5 dry matter 72.6 75.5 76.7 71.6 75.5 76.7 40.5 second component Aluminum dross 22.5 22.5 22.5 22.5 22.5 22.5 22.5 Refining slag 0 0 0 0 0 0 36 calcium hydroxide 10 10 10 10 10 10 10 hard fatty acid 0 0 0 0 0 0 0 cement 0 0 0 0 0 0 0 Sticky desulfurizer (wt%) Refining slag 34.3 33.3 33.0 34.6 33.3 33.0 33.0 Aluminum dross 21.4 20.8 20.6 21.6 20.8 20.6 20.6 Adhesive 9.5 9.3 9.2 9.6 9.3 9.2 9.2 calcium oxide 14.9 6.1 2.6 18.0 6.1 2.6 3.2 calcium hydroxide 19.9 30.5 34.6 16.2 30.5 34.6 34.0 Forming stability No disintegration or powdering after 7 days of resting No disintegration or powdering after 90 days of resting No disintegration or powdering after 5 days of standing No disintegration or powdering after 90 days of resting No disintegration or powdering after 180 days of standing

table 3 "--": Not in progress Unit: grams Comparative example 1 2 3 4 5 6 7 8 calcium oxide Dosage 31.5 31.5 31.5 31.5 31.5 31.5 31.5 31.5 Particle size (mm) 0.27 or less greater than 1.4 water 0 0 0 0 0 0 14.2 31.5 Refining slag 36 36 36 36 36 36 36 36 hydration reaction Temperature(℃) -- -- -- -- -- -- 25 25 time (minutes) -- -- -- -- -- -- 30 30 mixture Calcium hydroxide (g) -- -- -- -- -- -- 6.2 8.2 Calcium oxide(g) -- -- -- -- -- -- 26.8 25.3 dry matter -- -- -- -- -- -- 69 69.5 Aluminum dross 22.5 22.5 22.5 22.5 22.5 22.5 22.5 22.5 Refining slag 0 0 0 0 0 0 0 0 calcium hydroxide 10 0 0 0 15 20 10 10 hard fatty acid 0 0 10 0 0 0 0 0 cement 0 0 0 10 0 0 0 0 Sticky desulfurizer (wt%) Refining slag 36.0 40.0 36.0 36.0 34.3 32.7 35.5 35.3 Aluminum dross 22.5 25.0 22.5 22.5 21.4 20.5 22.2 22.1 Adhesive 10.0 0 10.0 10.0 14.3 18.2 9.9 9.8 calcium oxide 31.5 35.0 31.5 31.5 30.0 28.6 26.3 24.7 calcium hydroxide 0 0 0 0 0 0 6.1 8.1 Forming stability Let stand for 1 day to powder

In summary, through the design of the above process, especially the design of converting part of the calcium oxide into calcium hydroxide, the block desulfurizer prepared by the method for preparing the block desulfurizer of the present invention can be used in an environment containing water vapor. After being stored in a medium for a period of time, calcium oxide will not easily expand due to the presence of water vapor, leading to disintegration and powdering. As a result, it still retains its original shape and has good molding stability, so that it can be used for refining. In the process of making steel, it is easy to use and has good operability, and because there will be no powdering due to disintegration after a period of storage, it can avoid being used by the steelmaking equipment when it is put into the steelmaking equipment. The dust collecting device sucks in the dust and cannot effectively reduce the sulfur content in the molten steel, resulting in the problem of poor desulfurization efficiency. Therefore, the purpose of the present invention can indeed be achieved.

However, the above are only examples of the present invention and should not be used to limit the scope of the present invention. All simple equivalent changes and modifications made based on the patent scope of the present invention and the content of the patent specification are still within the scope of the present invention. within the scope covered by the patent of this invention.

without.

Claims (11)

A method for preparing block desulfurizer, including: Perform a hydration reaction between the first component including calcium oxide with a particle size of 1.4 mm or less and water, so that part of the calcium oxide is converted into calcium hydroxide, and a mixture containing calcium hydroxide and calcium oxide is obtained; The mixture is dried to remove moisture and obtain a dry product; The dried product is mixed with a second component including aluminum slag, and subjected to pressure forming treatment. The preparation method of block desulfurizer according to claim 1, wherein the first component also includes refining slag, and the refining slag includes calcium oxide. The preparation method of block desulfurizer according to claim 1, wherein the second component further includes a binder. The method for preparing a block desulfurizer according to claim 3, wherein the adhesive is selected from cement, calcium hydroxide, zinc stearate, or any combination of the above. The preparation method of block desulfurization agent as described in claim 1, wherein the temperature range of the hydration reaction is 50°C to 150°C, and the time range is 10 minutes to 180 minutes. The preparation method of block desulfurizer as described in claim 1, wherein the pressure range of the pressure forming process is 8kg/cm ² to 15kg/cm ² , and the time range is 2 seconds to 90 seconds. The preparation method of block desulfurizer as described in claim 2, wherein the weight ratio of the calcium oxide, the water and the refining slag ranges from 1:0.45 to 2: greater than 0 and less than 1.5. The preparation method of block desulfurizer as described in claim 1, wherein the second component also includes refining slag. The preparation method of block desulfurizer as described in claim 1, wherein, based on the total amount of the block desulfurizer being 100wt%, the content of calcium oxide in the block desulfurizer ranges from 2 wt% to 18wt%, and the content of the aluminum slag ranges from 20wt% to 30wt%. The preparation method of block desulfurizer as described in claim 3, wherein, based on the total amount of the block desulfurizer being 100wt%, the content range of the calcium oxide in the block desulfurizer is 2wt% to 18wt%, the content of the aluminum slag ranges from 20wt% to 30wt%, and the content of the adhesive ranges from greater than 0wt% to less than 20wt%. The preparation method of block desulfurizer as described in claim 8, wherein, based on the total amount of the block desulfurizer being 100 wt%, the content range of the calcium oxide in the block desulfurizer is 2 wt% to 18wt%, the content of the aluminum slag ranges from 20wt% to 30wt%, and the content of the refining slag ranges from greater than 30wt% to less than 40wt%.