JP2023132282A - Converter heating material and method for producing the same - Google Patents

Abstract

To provide a converter heating material capable of reducing the addition amount of a binder while increasing the strength of the heating material by increasing the filling rate of a carbide, and a method for producing the same.SOLUTION: A converter heating material of a carbide molded body obtained by being molded with a carbide particulate body and a binder. A carbide in the carbide molded body has (a) a particle diameter in which the maximum particle diameter is below 1/2 of the typical length d of the carbide molded body, and (b) when it is classified so that a large particle diameter side reaches 70 vol.% and a small particle diameter side reaches 30 vol.%, a ratio between the median particle diameter D50 of the carbide on the large particle diameter side and the median particle diameter D50 of the carbide on the small particle diameter side is 1.5 to 2.3. Also provided is a method for producing a converter heating material in which a carbide raw material is subjected to one or plural screening treatments and one or plural breaking treatments so that the carbide particulate body has particulate size distributions similar to the (a) and (b).SELECTED DRAWING: Figure 7

Description

The present invention relates to a heating material for a converter, and more particularly, the present invention relates to a heating material for a converter, which increases the filling rate of carbide, which is a raw material for the heating material, and increases the strength of the heating material, while optimizing the amount of binder added. Materials and methods of manufacturing them.

A converter in the steelmaking process is a major process in which hot metal tapped in a blast furnace is decarburized by spraying high-purity oxygen at high speed to produce molten steel. At the same time, auxiliary raw materials mainly consisting of quicklime are added to remove impurities (such as phosphorus) from the hot metal.

On the other hand, hot metal pretreatment is sometimes performed as a pre-process of the converter to remove S, P, etc. from the hot metal due to material property requirements for steel products. In this case, there is a problem that the hot metal temperature decreases due to the hot metal pretreatment.

In addition, in recent years, from the perspective of environmental protection, reducing _CO2 emissions has become an important issue in the steelmaking process, and in the steelmaking process, the proportion of cold iron sources such as iron scrap (scrap iron) has been increased Attempts have been made to increase the ratio of hot metal and reduce the blending ratio of hot metal. This is because the production of hot metal in a blast furnace requires a large amount of energy to reduce and melt the iron ore and at the same time emits a large amount of CO ₂ in the production of steel products, whereas cold iron sources produce molten metal. Only heat is required, and if a cold iron source is used in the steelmaking process, the amount of energy used for the reduction heat of iron ore can be reduced, and _CO2 emissions can be significantly reduced. It is. However, in a converter, the heat source for melting the cold iron source is the sensible heat of the hot metal and the oxidation heat of carbon and silicon in the hot metal, and there is naturally a limit to the amount of cold iron source melted.

Therefore, in the dephosphorization treatment and decarburization refining of hot metal, in order to increase the thermal margin of hot metal and expand the blending ratio of cold iron sources, coal and coke powder are used as heating materials to supply an additional carbon source to hot metal. , graphite, electrode powder, SiC, etc., have been proposed in a variety of heat raising materials formed into lumps. Note that earthy graphite, which is a natural mineral product that is not molded, is also sometimes used as a heating material because it is relatively inexpensive.

Regarding such heat raising materials for converters, for example, in Patent Document 1, carbon powder (coal, coke powder, graphite, etc.) containing 30 to 70% particles with a particle size of 1 mm or less, and the rest with a particle size of 1 to 8 mm is used. Add a binder consisting of polyvinyl alcohol, carboxymethyl cellulose, alpha starch, etc. in the range of 0.5 to 1.0% by weight of the carbon powder, temper and knead so that the water content is 10% or less, By high-pressure molding and drying, it is possible to mold carbon powder into a solid material with sufficient strength.

Furthermore, in Patent Document 2, a converter molded with a charred material obtained by carbonizing carbon-neutral plant biomass and a binder made of starch, carboxymethyl cellulose, corn starch, etc. in an amount of 1 to 15% by mass based on the mass of the charred material. By using the heating material as an alternative to conventional heating materials for converters that are made from fossil resources such as coal, coke, and graphite, fossil resource consumption can be reduced and _CO2 , which is a greenhouse gas, can be reduced. By making it possible to reduce the generation of carbides and making the particle size of the carbide 3 mm or less, the solid material has a crushing strength of 490 N/piece or more, which is sufficient strength as a heat raising material for a converter.

Japanese Patent Application Publication No. 2-270922 Patent No. 5846289

However, since the carbon powder used as the raw material for the heating material described in Patent Document 1 has a large proportion of particles with a particle size of 1 mm or less at 30 to 70%, treatments for particle size adjustment such as pulverization of the carbon raw material are necessary. The problem is that the load is high.

Furthermore, the carbon powder used as the raw material for the heating material described in Patent Document 2 needs to be sized to a relatively narrow particle size range of 3 mm or less, and similar to the invention described in Patent Document 1, the There is a problem in that the processing load for particle size adjustment, such as pulverization of carbon raw materials, is high.

Furthermore, in the heating material described in Patent Document 1, a binder is used in a range of 0.5 to 1.0% by weight of carbon powder, and in the heating material described in Patent Document 2, a binder is used in a range of 1 to 1.0% by weight of carbon powder. Although 15% by mass of binder is used, in recent years, a problem has been that the price fluctuations of plant-derived binders, specifically corn starch derived from corn, have increased. This is due to price fluctuations linked to poor corn crops due to abnormal weather, and upward pressure on prices due to increased demand for corn-derived bioethanol to reduce environmental impact. Therefore, there is an increasing demand for technology that reduces the amount of binder used when molding heat-raising materials.

On the other hand, if the amount of binder added is less than the required amount, abnormalities such as insufficient strength of the molded carbon material will occur, leading to problems such as operational troubles during transportation and a decrease in yield. In addition, if the problem of insufficient strength of the molded carbonaceous material due to the reduction of the amount of binder is solved by ensuring the strength of the molded carbonaceous material by finely crushing all the raw material carbide, then There is a problem in that the problem of increased costs arises and the overall economic efficiency is impaired.

The present invention has been made in view of the above circumstances, and by optimizing the particle size distribution of carbide, which is a raw material for heating material, it is possible to increase the filling rate of carbide and increase the strength of heating material. The object of the present invention is to provide a heat raising material for a converter, which makes it possible to reduce the amount of binder added while increasing the amount of binder added, and a method for manufacturing the same.

[1] A heating material for converter of a carbide molded body formed by molding carbide powder and a binder, wherein the carbide in the carbide molded body has (a) a maximum particle size of the carbide molded body; It has a particle size less than 1/2 of the representative length d, and (b) the large particle size side when divided so that the large particle size side accounts for 70% by volume and the small particle size side accounts for 30% by volume. A heat raising material for a converter, characterized in that the ratio of the median particle size D50 of the carbide to the median particle size D50 of the carbide on the small particle size side is 1.5 to 2.3.
[2] The heat-raising material for a converter according to [1], wherein the heat-raising material for a converter has a crushing strength of 490 N/piece or more.
[3] A method for producing a heating material for a converter of a carbide molded body formed by molding a carbide powder and a binder, the method comprising at least one selected from the group of coal, vegetable biomass, and waste plastic. A carbide raw material is produced by carbonization, and the carbide raw material is subjected to one or more sieving treatments and one or more crushing treatments, so that (a') the carbide raw material has a maximum particle size of the carbide molded body. (b') the obtained carbide powder is obtained by dividing the carbide powder into a plurality of groups with different particle sizes within a range of less than 1/2 of the representative length d; is divided into 70 volume % on the large grain size side and 30 volume % on the small grain size side, and the median particle size D50 of the carbide on the large grain size side and the median grain size D50 of the carbide on the small grain size side. A method for producing a heat raising material for a converter, characterized in that the carbide powder before molding is prepared by blending so that the ratio is in the range of 1.5 to 2.3.
[4] The method for producing a heat-raising material for a converter according to [3], wherein the heat-raising material for a converter has a crushing strength of 490 N/piece or more.

According to the present invention, the particle size distribution of carbide in a heat-raising material for a converter (carbide molded body) (hereinafter also simply referred to as a heat-raising material) is determined such that the maximum particle size of the carbide is the same as that of the heat-raising material for a converter. Carbide on the large particle size side when the particle size is less than 1/2 of the representative length d and the carbide particles are divided so that the large particle size side accounts for 70% by volume and the small particle size side accounts for 30% by volume. By setting the ratio of the median particle size D50 of the carbide to the median particle size D50 of the carbide on the small particle size side to be in the range of 1.5 to 2.3, the filling rate of the carbide is increased and the strength of the heating material is increased. It is possible to provide a heat raising material for a converter and a method for producing the same, which makes it possible to reduce the amount of binder added within an economically reasonable range.

1 is a schematic cross-sectional view of an example of converter equipment in which the heat-raising material for converter of the present invention is used. FIG. 2 is a schematic cross-sectional view showing how biomass charcoal is crushed by a roll crusher (cutter mill) used in preliminary experiments and examples leading up to the present invention. FIG. 2 is a schematic cross-sectional view showing how pulverized biomass charcoal is compression-molded using a twin-roll briquette machine used in preliminary experiments and examples leading up to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing how pulverized biomass charcoal is extruded and molded by a pelletizing machine (pelletizer) used in preliminary experiments and examples leading up to the present invention. It is a diagram obtained in preliminary experiments leading to the present invention, showing the relationship between the ratio of large grain size to small grain size of carbide in a heat raising material for a converter and the porosity of a carbide molded body of a heat raising material for a converter. FIG. 2 is a diagram summarizing the results by stratifying them according to the particle size ratio of large particles to small particles. FIG. 2 is a diagram obtained in preliminary experiments leading to the present invention, showing the particle size ratio between large and small particles of carbide in a heat-raising material for a converter, and the minimum void of a carbide molded body of a heat-raising material for a converter. FIG. 2 is a diagram summarizing the relationship between rates. It is a diagram obtained in preliminary experiments leading to the present invention, showing the ratio of the median particle size D50 of carbide on the large particle size side to the representative length d of the carbide molded body, and the ratio required when forming a heat raising material for a converter. FIG. 3 is a diagram summarizing the relationship with binder concentration. It is a figure which shows the measurement result of the particle size of the crushed biomass carbon material used in the Example of the pellet-shaped carbide molded object of this invention. It is a figure showing the measurement result of the particle size of the crushed biomass carbon material used in the example of the briquette-shaped carbide molded object of the present invention.

The present invention will be explained in detail below. First, converter equipment to which the present invention is applied will be explained. FIG. 1 is a schematic sectional view of an example of converter equipment using the heat raising material for converter of the present invention.

In FIG. 1, a top-blowing lance 2 is inserted from above into a converter body 1 containing hot metal 8, and at the same time oxygen gas is blown onto the hot metal 8 from the top-blowing lance 2. The hot metal 8 is decarburized and refined while the hot metal 8 and the slag 9 are stirred by blowing bottom blowing gas for stirring from a plurality of bottom blowing tuyeres 3 arranged at the bottom. By decarburizing the hot metal 8 and refining it, a converter exhaust gas 10 mainly consisting of CO gas is generated from inside the furnace.

A flue 4 is installed above the converter main body 1, and a primary dust collector (not shown), a secondary dust collector (not shown), and an induced fan (not shown) are installed downstream of the flue 4. They are installed in order. With such converter exhaust gas 10 processing equipment, the converter exhaust gas 10 generated inside the converter main body 1 due to decarburization and refining is cooled, dust removed, and left unburned downstream of an induced fan (not shown). It is designed to be collected in a side gas holder (not shown).

The side of the flue 4 that connects to the furnace mouth of the converter body 1 is called a skirt 5, and has a structure that can be moved up and down.When collecting exhaust gas, the skirt 5 and the converter body In principle, it will be in close contact with the furnace mouth of No. 1. In addition, the flue 4 contains materials such as quicklime, calcined dolomite, iron ore, mill scale, manganese ore, heating materials (carbon materials such as coke and soil graphite), and ferroalloys (Fe-Mn, Fe-Si, etc.). An auxiliary raw material charging device including a hopper 6, a charging chute 7, and the like is installed for adding auxiliary raw materials to the converter main body 1. Slag 9 is formed by quicklime, calcined dolomite, iron ore, mill scale, manganese ore, etc. that are input into the furnace from an auxiliary raw material input device.

The heat-raising material for a converter of the present invention is a heat-raising material for a converter that is a carbide molded body formed by molding carbide powder and a binder, wherein the carbide in the carbide molded body is (a) maximum The particle size is less than 1/2 of the representative length d of the carbide molded body, and (b) the large particle size side is 70% by volume and the small particle size side is 30% by volume. The ratio of the median particle size D50 of the carbide on the large particle size side to the median particle size D50 of the carbide on the small particle size side is 1.5 to 2.3.

Further, the method for producing a heat-raising material for a converter of the present invention is a method for producing a heat-raising material for a converter, which is a carbide molded body formed by molding a carbide powder and a binder, and comprises using coal, vegetable biomass, etc. , producing a carbide raw material by carbonizing at least one selected from the group of waste plastics, and subjecting the carbide raw material to one or more sieving treatments and one or more crushing treatments, (a') The carbide powder is obtained from the carbide raw material, and the carbide powder is divided into a plurality of groups having different particle sizes within a range where the maximum particle size is less than 1/2 of the representative length d of the carbide molded body, and , (b') When the obtained carbide powder is divided into 70% by volume on the large particle side and 30% by volume on the small particle side, the median particle size D50 of the carbide on the large particle size side and the median particle size D50 of the carbide on the small particle size side is in the range of 1.5 to 2.3 to obtain the carbide powder before molding.

The carbide molded body (heat raising material for converter) of the present invention is produced by adding a binder and water to carbide powder as the main raw material, mixing and stirring with a known mixer (not shown), and then using a known molding device. (See FIGS. 3 and 4) and then dried to a predetermined moisture content. The main raw material, carbide powder, is produced by first carbonizing raw materials such as coal, plant-based biomass, and waste plastic using a known carbonization device (not shown) such as a rotary kiln furnace, batch furnace, or shaft furnace. Next, the obtained carbide is crushed into various particle sizes by passing it through a known cutter mill once or multiple times as necessary, and the particle size is further adjusted by sieving or the like. As the binder, inorganic bentonite, organic carboxymethyl cellulose, cornstarch, etc. can be used.

As a known cutter mill, in FIG. 2, carbon material 21 carbonized in a rotary kiln or the like is supplied from a hopper 27 of a roll crusher (cutter mill) 26 to a crusher roll 28, and is crushed into a pulverized material 22, which is then transferred to a belt. It schematically shows how it is carried out on a conveyor 29. As a molding device for the carbide molded body, a known twin-roll briquette machine, a pelletizer, or the like can be used. In FIG. 3, a mixed material 23 of carbon material, which is obtained by adding a binder and water to carbon material whose particle size has been adjusted and kneading it in a mixer, is supplied from a hopper 32 of a twin-roll briquette machine 31 to a forming roll 33, and is compressed and molded. The figure schematically shows how the charcoal material molded product 24 (briquettes 24a) is conveyed out by a belt conveyor 34. Further, in FIG. 4, a similar kneaded material 23 of carbonaceous material is supplied from a hopper 42 of a pelletizing machine (pelletizer) 41 to a screw feeder 43, compressed and extruded, and further cut into a predetermined length by a cutter 44. The molded product 24 (pellet 24b) is conveyed out by a belt conveyor 45.

The carbide in the carbide molded body of the present invention has a maximum particle size of less than 1/2 of the representative length d of the carbide molded body during the production of the heat raising material for a converter. This is to prevent the binder concentration from increasing unnecessarily. In other words, when granulating carbide powder, contrary to the expectation that small particles will fit between large particles and form a dense packing, there may be some areas where small particles do not fit between large particles. However, as will be explained later in the preliminary experiment results, such a phenomenon becomes particularly noticeable when the maximum grain size is 1/2 or more of the representative length d of the carbide molded body. Therefore, although such large particles are bound together by the liquid bridge adhesive force of water containing a binder, when the maximum particle size is 1/2 or more of the representative length d of the carbide molded body, there are large spaces between the large particles. This is because if the distance becomes wider, a greater liquid crosslinking adhesive force will be required, and the binder concentration will need to be increased.

Here, the representative length d of the carbide molded body (heat raising material for converter) of the present invention will be explained. In other words, the representative length d is the length that represents the external shape of the converter heating material when dealing with the balance between the gravity applied to the converter heating material and the drag force received from the converter exhaust gas depending on its external shape. It is. Using this representative length, for example, if a heating material of a representative length is used whose gravity is smaller than the drag force received from the converter exhaust gas, the heating material will float together with the converter exhaust gas and rise It is possible to consider in advance that it will not be possible to introduce the heating material to the molten metal. In addition, when the heat-raising material for a converter is in the form of pellets, the representative length d is represented by the pellet diameter, and when the heat-raising material for the converter is in the shape of a briquette, the representative length d is the maximum diagonal length. can be represented.

In addition, when the carbide in the carbide molded body of the present invention is divided so that the large particle size side is 70% by volume and the small particle size side is 30% by volume, the median particle size D50 of the carbide on the large particle size side and the small Setting the ratio of the median particle size D50 of the carbide on the particle size side to be 1.5 to 2.3 is because, as explained in the preliminary experiments and examples below, the voids are smaller than when large and small particles are not mixed. The rate of change in porosity is small and the allowable range of porosity has a wide range, so even if manufacturing variations are taken into account, abnormalities in carbide molded bodies do not occur and product yields are maintained at a high level. This is because it is possible.

Here, measurement of the ratio of the median particle size of carbide particles in the heat raising material for a converter (carbide molded body) of the present invention will be explained. First, the heat-raising material (carbide molded body) for converter is soaked in water to dissolve the binder, then filtered to collect the carbide, washed with pure water or methanol, and then subjected to laser diffraction particle size distribution measurement (JIS Z 8825 :2013 Determine the particle size distribution of carbide particles by particle size analysis (laser diffraction/scattering method). Next, by computer analysis of the particle size distribution, when the large particle size side is divided into 70 volume % and the small particle size side is 30 volume %, the median particle size D50 of the carbide on the large particle size side and the small The ratio of the median particle size D50 of carbides on the particle size side can be determined. Note that the median particle size D50 here refers to a volume-based integrated distribution curve in which the horizontal axis represents the particle size and the vertical axis represents the cumulative value of particle amount in volume percentage (%). It is determined by reading the particle size corresponding to %.

On the other hand, in the method for producing a heat raising material for a converter of the present invention, the ratio of the median particle size of the carbide powder, which is the main raw material of the carbide molded body, is measured by The particle size distribution of the carbide powder is determined by sieving the particles, and the particle size distribution can be determined in the same manner as the method for determining the median particle size ratio of the carbide particles in the carbide molded body described above. In addition, the measurement results of the ratio of the median particle size of the carbide powder, which is the raw material for the carbide molded body, and the ratio of the median particle size of the carbide particles in the carbide molded body manufactured from the carbide powder and granule. can be treated as being equivalent both in principle and statistically.

The results of preliminary experiments regarding such a range of carbide particle sizes will be explained next.
The present inventors first studied the relationship between the crushing strength of a carbide molded body (heat raising material for a converter) obtained by molding carbide powder and the filling rate of carbide particles. In general, when the filling rate is high, mechanical bonding effects such as an increase in the capillary suction force between particles and particles bonding to each other's uneven parts occur, so the crushing strength and filling rate (= 1 - porosity ) is known to be proportional.

Regarding the filling rate, the filling model by Horsfield is known, and when true spherical particles with a single particle diameter φ are hexagonally close-packed, the porosity is 25.9%. Furthermore, by filling the remaining space between the true spherical particles with true spherical particles having a true spherical particle diameter φ of 0.414φ, the porosity can be set to 20.7%. However, when molding carbide, it is difficult to apply Horsfield's filling model because the packing structure is not hexagonal close-packed, the grain shape is not a true sphere, and the grain size is not uniform and has a distribution. .

Therefore, as a preliminary experiment to increase the filling rate of carbide and increase the crushing strength of the carbide molded body, we first conducted an integer division equivalent (1/ A carbide group having an average particle size of 2A, 1/3A, 1/4A, 1/5A, 1/6A) was prepared by adjusting the particle size by grinding and sieving the raw material carbide. Among these carbide groups, the carbide groups on the large particle size side are 1/2A, 1/3A, 1/4A, and 1/5A, and the carbide groups on the small particle size side are 1/2A, 1/3A, 1/4A, and 1/5A. We decided to study 10 combinations shown in Table 1 as four groups: 3A, 1/4A, 1/5A, and 1/6A. FIG. 5 shows, as an example, four types of particle size ratios (1.3, 2.0, 2.5, 3.0) among these 10 carbide combinations, and the graph shows the difference in each group. This shows the results of measuring the porosity (=1-filling ratio) of each sample with varying volume ratios (mixing ratios) of small particles. In addition, each sample for each condition at this time was prepared by adding cornstarch containing 8% by mass of carbide as a binder and appropriate water for each carbide mixture in which the volume ratio (mixing ratio) of small particles in each set was changed. The material was added and kneaded, and then molded with a pelletizer to obtain a pellet molded product, which was further dried to a moisture content of 3% by mass or less to obtain a test material. Table 1 also lists the minimum porosity that can be read from FIG. 5 and a diagram equivalent to FIG. 5 (including data at particle diameter ratios not shown in FIG. 5).

It can be seen from FIG. 5 that the porosity changes depending on the blending ratio of small particle size and large particle size, and takes a minimum value when the volume ratio of small particles is around 0.3. Furthermore, from FIG. 5, it can be seen that the change in porosity can be organized by stratification based on the ratio of particle diameters. Figure 6 shows the minimum particle size ratio of the carbide molded body of the heat-raising material for a converter, with the horizontal axis plotting the particle size ratio between large and small grains of the carbide in the heat-raising material for a converter, which can be stratified and organized in this way. FIG. 2 is a diagram summarizing these relationships with the porosity as the vertical axis. It can be seen from FIG. 6 that the minimum porosity can be reduced by increasing the particle size ratio (large particle size/small particle size) of carbide. From this, it was presumed that the amount of water added to fill the voids could be further reduced.

However, group no. In samples 3 and 4, the particle diameter ratio is large and the minimum porosity can be greatly reduced to 0.32 and 0.25, respectively, but as can be seen from Figure 5, the porosity changes greatly depending on the blending ratio of carbide particles. . Therefore, due to variations during manufacturing, the amount of added water may be higher than the appropriate value, and there is a concern that abnormalities such as lamination may occur in the carbide molded product after molding and before drying, resulting in a decrease in product yield. On the other hand, group no. 1, 2, 5 to 10, the porosity is group No. Although it is inferior to 3 and 4, the rate of change in porosity near the mixing ratio that minimizes porosity is small, and the allowable range of porosity has a wide range, even when manufacturing variations are taken into account. It is expected that no abnormalities will occur in the carbide molded body and that a high product yield will be obtained. Therefore, the porosity of group No. Although inferior to 3 and 4, the porosity is 2 to 5% lower than when large and small particles are not mixed (porosity 0.39), and even when manufacturing variations are taken into account, abnormalities in the carbide molded body are not observed. Group No. 1, which does not occur and does not cause a decrease in product yield. I decided that 1, 2, 7, and 9 were appropriate.

As mentioned above, from Figure 6, it is inferred that by increasing the particle size ratio of carbide, the minimum porosity can be lowered, and the amount of water added to fill the voids can be further reduced. We decided to take this further and investigate the possibility of reducing the amount of binder required when molding heat raising materials for converters. FIG. 7 is a diagram summarizing the relationship between the ratio of the median particle size D50 of carbide on the large particle size side to the representative length d of the carbide molded body and the binder concentration required when forming a heat raising material for a converter. be. According to FIG. 7, it was found that when particles having a large diameter such as 1/2A were used as the large particles, the required binder concentration increased. The following is presumed to be the cause of this. That is, during granulation, small particles enter between the large particles, so it is expected that they will be tightly packed, but depending on the location, there will inevitably be areas where the small particles do not enter between the large particles. In this part, the particles are bonded together by the liquid bridge adhesive force of water containing a binder between the large particles. It is presumed that the wider the spacing between the large particles, the greater the liquid bridge adhesion force required, and therefore the need to increase the binder concentration. In fact, group no. In the case where 1/2A is used for large particles as in case No. 2, group No. 7, a higher binder concentration was required compared to the case where 1/3A was used for large particles. For this reason, group no. Group No. 2 is better than Group No. 2. The amount of binder was lower in No. 7.

From the above preliminary experimental results and the examples described later, it is clear that the carbides contained in the heat raising material for converters of the present invention are (a) It shall have a particle size less than 1/2 of the representative length d of the heating material for the furnace (carbide molded body), and at the same time, in order to ensure a preferable control range, (b) 70% by volume on the large particle size side, When divided so that the small particle size side is 30% by volume, the ratio of the median particle size D50 of the carbide on the large particle size side to the median particle size D50 of the carbide on the small particle size side is 1.5 to 2.3. so that it is.

It is preferable that the crushing strength of the heat raising material for a converter of the present invention is 490 N/piece or more. If the crushing strength of the heating material is less than 490N/piece, the heating material will be crushed into dust before it reaches the molten steel and will be scattered with the converter exhaust gas, making it difficult to feed the heating material into the molten metal with a high yield. This is because it is not possible to do so.

Examples of the present invention will be described below.

As the carbide raw material, we decided to use woody raw materials such as lumber scraps and forest residues, and we decided to use biomass charcoal material that was heated and carbonized at 650° C. for the molded object.

The shapes of the temperature increasing materials for a converter used in the examples were a pellet shape with a diameter of 20 mm and a briquette shape with a side of 50 mm. At this time, the target value of the particle size of the pulverized biomass carbonaceous material is set such that the diameter In the case of a pellet shape of 20 mm, the diameter was determined to be 9 mm or less, and in the case of a briquette shape of 50 mm on a side, the diameter was determined to be 22 mm or less.

According to the target value of the particle size of the pulverized material, the biomass carbonaceous material is passed through the roll crusher (cutter mill) 26 shown in FIG. 2 once or multiple times, and then sieved. Pulverized biomass charcoal with various average particle diameters was prepared. Furthermore, when these crushed biomass chars with various average particle sizes are combined and divided into 70% by volume on the large particle size side and 30% by volume on the small particle size side, the median of the charcoal on the large particle size side is Five sets of carbide powder mixtures were prepared in which the ratio of the particle size D50 to the median particle size D50 of the carbide on the small particle size side ranged from 1.3 to 2.5 as shown in Table 2. The particle size distributions of the five sets of prepared carbide powders are shown in FIGS. 8 and 9.

Next, under the mixing conditions shown in Table 2, corn starch and water as a binder were added to each of the five sets of carbide powder and granules and mixed, using a twin roll briquette machine shown in FIG. 3 or a pelletizer shown in FIG. 4. Compression molded into briquettes or pellets. After molding, the molded material was allowed to stand at room temperature for 5 days and dried to a moisture content of approximately 3%, thereby producing a heat-raising material for a converter.

In Comparative Example 1, as shown in Table 2 and FIG. 8(a), the particle size ratio was small at 1.3, and there were few small particles filling the gaps between large particles, so it was almost impossible to reduce the minimum porosity. The amount of water added to fill the gaps between large particles increased, and the amount of binder added became the largest among the five sets. Furthermore, in Comparative Example 1, the crushing strength of the dried carbide molded body obtained by sampling n=10 could not achieve the crushing strength of 490 N or more required for operation.

In addition, in Comparative Example 2, as shown in Table 2 and FIG. 9(b), the particle size ratio is large at 2.5, and the minimum porosity is low, and the amount of water added to fill the gaps between large particles is small. Accordingly, the amount of added binder was the smallest among the five sets together with Invention Example 3. However, since the particle size ratio is large, the porosity changes greatly depending on the blending ratio of carbide particles (see Figure 5), and the amount of added water tends to be higher than the appropriate value due to variations in manufacturing. Abnormalities such as lamination occurred in the carbon material before drying, resulting in a significant drop in product yield, to the point that it was not possible to prepare materials for crushing strength testing.

On the other hand, in Examples 1 to 3 of the present invention, the amount of binder could be reduced while maintaining the crushing strength and yield required for operation, regardless of the difference in shape between pellets and briquettes.

1 Converter main body 2 Top blowing lance 3 Bottom blowing tuyere 4 Flue 5 Skirt 6 Hopper 7 Charge chute 8 Hot metal 9 Slag 10 Converter exhaust gas 21 Carbon material (biomass carbon material) (carbonized product)
22 Pulverized carbon material (biomass carbon material) 23 Kneaded material of carbon material (biomass carbon material) 24 Molded material of carbon material (biomass carbon material) 24a Briquette 24b Pellet 26 Roll crusher (cutter mill)
27 Hopper 28 Crusher roll 29 Belt conveyor 31 Twin roll briquette machine 32 Hopper 33 Forming roll 34 Belt conveyor 41 Pellet making machine (pelletizer)
42 Hopper 43 Screw feeder 44 Cutter 45 Belt conveyor

Claims (4)

A heating material for a converter of a carbide molded body formed by molding a carbide powder and a binder,
The carbide in the carbide molded body is
(a) The maximum particle size is less than 1/2 of the representative length d of the carbide molded body,
(b) Median particle size D50 of carbide on the large particle size side and median particle size D50 of carbide on the small particle size side when divided so that the large particle size side is 70 volume % and the small particle size side is 30 volume % A heat raising material for a converter, characterized in that the ratio of The heat-raising material for a converter according to claim 1, wherein the heat-raising material for a converter has a crushing strength of 490 N/piece or more. A method for producing a heating material for a converter of a carbide molded body formed by molding a carbide powder and a binder, the method comprising:
producing a carbide raw material by carbonizing at least one selected from the group of coal, plant biomass, and waste plastic;
The carbide raw material is subjected to one or more sieving treatments and one or more crushing treatments,
(a') Obtaining from the carbide raw material the carbide powder which is divided into a plurality of groups with different particle sizes within a range where the maximum particle size is less than 1/2 of the representative length d of the carbide molded body. In addition,
(b') When the obtained carbide powder is divided into 70% by volume on the large particle side and 30% by volume on the small particle side, the median particle size D50 of the carbide on the large particle size side A converter, characterized in that the carbide powder before molding is prepared so that the ratio of the median particle size D50 of the carbide on the small particle size side is in the range of 1.5 to 2.3. Method of manufacturing heat-raising material for use. 4. The method for producing a heat-raising material for a converter according to claim 3, wherein the heat-raising material for a converter has a crushing strength of 490 N/piece or more.

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