WO2025211234A1 - Method for producing sintered ore and method for using silicic acid biomass for blast furnace - Google Patents

Abstract

The present invention provides a method for producing a sintered ore and a method for using a silicic acid biomass for a blast furnace, the methods utilizing biochar that is derived from a silicic acid biomass. The present invention relates to a method for producing a sintered ore by a Dwight-Lloyd sintering machine, and uses a granulated starting material that is obtained by blending a powdery iron ore, a component adjusting flux, a return ore, and a carbonaceous material. Fixed carbon and silicon oxide in the biochar that is obtained by subjecting a silicic acid biomass to a dry distillation treatment are applied to some or all of the carbonaceous material and some or all of the silicon oxide content in the component adjusting flux to be blended in the granulated starting material. In this method for using a silicic acid biomass for a blast furnace, a sintered ore which is obtained as described above is charged from the furnace top of the blast furnace.

Description

Sintered ore manufacturing method and method for utilizing silica biomass in a blast furnace

The present invention relates to a method for producing sintered ore and a method for using silica biomass in a blast furnace.

In blast furnace operation, it is extremely important to adjust the basicity of the slag in the blast furnace and ensure the fluidity of the slag in order to smoothly promote the reaction in the blast furnace.
Sintered ore, which is used to produce slag in blast furnaces, is produced by sintering a granulated raw material consisting of a mixture of iron ore as the primary raw material, SiO2 _- based auxiliary raw materials such as silica, CaO-based auxiliary raw materials such as limestone, sintered ore return ore of a certain size or less, and carbonaceous materials such as coke fines. The auxiliary raw materials used in the production of sintered ore are used to adjust the sinterability of the sintered ore. Furthermore, by using the auxiliary raw materials as gangue components of the sintered ore and as a source of blast furnace slag, they are also used to increase the fluidity of the slag in the blast furnace. For example, Patent Document 1 discloses an invention in which sintered raw material is made into pseudo-particles by adding auxiliary raw materials containing _SiO2 and/or MgO to the granulated raw material at 1.5 to 6 wt % of the granulated raw material, and the pseudo-particles are then charged to the bottom layer of the sintered raw material on a sintering pallet. This document claims that this invention can ensure the necessary amounts of _SiO2 and MgO to adjust the blast furnace slag composition. Furthermore, this invention claims that it can maintain smooth blast furnace operation without lowering the furnace top temperature.

On the other hand, reducing _CO2 emissions is an urgent issue from the perspective of preventing global warming, and technological development is being carried out in the steel industry to reduce _CO2 emissions. Methods for reducing _CO2 emissions include (a) reducing the amount of carbon in inputs, (b) capturing _CO2 in outputs, and (c) replacing conventional coal, oil, etc. with carbon-free carbon sources.

In conventional bottom suction sintering machines, such as Dwight Lloyd sintering machines, large amounts of coal (anthracite) and coke breeze are used as the carbonaceous material, resulting in the generation of large amounts of carbon dioxide gas. In response to this issue, Patent Document 2 discloses an invention that uses biochar, such as oil palm kernel shell charcoal, as a carbon-free carbon source for the carbonaceous material used in sintering.

Japanese Patent Application Publication No. 08-085829 JP 2013-237876 A

Incidentally, the expanded use of biomass (also known as silicate biomass due to its high ash content), such as rice husks and straw, which are carbon-free carbon sources and are generated in Japan in quantities exceeding 2 million tons each year, is becoming a problem. This is because biochar derived from silicate biomass can be problematic due to its high ash content of around 30-50%. Furthermore, biochar derived from silicate biomass not only promises a stable supply, but also has sufficient properties as a carbon source, with a fixed carbon content of around 15-50% and a unit calorific value of around 14-28 MJ/kg.

Previous studies into the use of biochar as a carbon-free carbon source in steelworks have not adequately addressed the issue of high ash content in biochar derived from silicate biomass. Patent Document 2, which describes the use of biochar in a sintered ore manufacturing method, also fails to explicitly address the issue of high ash content in biochar derived from silicate biomass. The biochar described in the document is oil palm kernel shell charcoal, and the main components of the biochar exemplified in the document are 81.0-89.5% by mass fixed carbon, 7.2-9.2% by mass ash, and 3.2-9.8% by mass volatile matter. In contrast, the data disclosed in the document for the intended substitute, coke fines, have fixed carbon content of 86.0% by mass, ash content of 12.9% by mass, and volatile matter of 1.1% by mass. The intended substitute, anthracite, has fixed carbon content of 88.5% by mass, ash content of 5.0% by mass, and volatile matter of 6.4% by mass. As such, the component composition of oil palm kernel shell coal is comparable to that of the coke breeze and anthracite it replaces, so there is no need to specifically address the issue of ash content.

On the other hand, it remains to be determined whether biochar derived from silicate biomass with a high ash content can be used as is as the carbonaceous material in the granulated raw material for the sintering raw material to be made into pseudo-particles as described in Patent Document 1. If biochar derived from silicate biomass were used as a heat source for sintering to produce sintered ore, its high ash content would directly affect the adjustment of blast furnace slag basicity and slag fluidity, which are the objectives of Patent Document 1.

The present invention therefore aims to provide a method for producing sintered ore that utilizes biochar derived from silicate biomass, and a method for using silicate biomass in a blast furnace.

[1] A method for producing sintered ore by a Dwight Lloyd sintering machine using a granulated raw material containing fine iron ores, a composition-adjusting sinter material, return ore, and a carbonaceous material,
A method for producing sintered ore, in which part or all of the carbonaceous material and part or all of the silicon oxide content of the component-adjusted welding material are replaced with fixed carbon and silicon oxide in biochar obtained by dry distillation of silicic acid biomass.
[2] A method for utilizing silicic acid biomass in a blast furnace, comprising charging sintered ore produced using a granulated raw material that is a blend of fine iron ores, a composition-adjusting solder, return ore, and a carbonaceous material, in which part or all of the carbonaceous material and part or all of the silicon oxide content of the composition-adjusting solder are replaced with fixed carbon and silicon oxide in biochar obtained by dry distillation of silicic acid biomass, into the top of the blast furnace.

According to the present invention, some or all of the carbonaceous material in the granulated raw material is replaced with fixed carbon from biochar derived from silicic acid biomass, thereby contributing to the reduction of _CO2 emissions in the steel industry. Furthermore, according to the present invention, some or all of the silicon oxide content of the composition-adjusted welding material in the granulated raw material is directly replaced with silicon oxide from biochar derived from silicic acid biomass, without adversely affecting the basicity of the melt during sintering or the basicity of the melt in a blast furnace. Furthermore, according to the present invention, biochar derived from silicic acid biomass, which is produced in large quantities in Japan each year, is used as the raw material containing both the carbonaceous material in the granulated raw material and the _SiO2 -based auxiliary material in the composition-adjusted welding material, thereby providing advantages in terms of procurement. Meanwhile, according to the present invention, a new application for biochar derived from silicic acid biomass, which has previously been limited in its applications due to its high ash content, can be effectively utilized to simultaneously utilize both fixed carbon and silicon oxide.
As described above, the present invention provides a method for producing sintered ore and a method for using silica biomass in a blast furnace, which contribute to the procurement of biochar and the reduction of _CO2 emissions in the steel industry without adversely affecting the sintering reaction during sintering or the basicity of blast furnace slag.

1 is a flowchart illustrating a method for producing sintered ore according to an embodiment of the present invention.

Sintered ore according to an embodiment of the present invention is one of the raw materials charged into the top of a blast furnace. Iron ore, a raw material for a blast furnace, can be efficiently used in various forms, including lump ore that can be charged as is, or by changing its form depending on the state of the raw material. For example, fine ore, which would impair the air permeability inside the furnace if left as is, can be baked to form sintered ore, and iron-containing dust recovered within steelworks can be agglomerated with hydraulic cement to form unbaked agglomerated ore.

Sintered ore according to an embodiment of the present invention is produced in a Dwight Lloyd sintering machine using a granulated raw material that is a blend of fine iron ores, a composition-adjusting solder, return ore, and a carbonaceous material, as shown in Figure 1. In this production, part or all of the carbonaceous material and part or all of the silicon oxide content of the composition-adjusting solder are replaced by fixed carbon and silicon oxide in biochar obtained by dry distillation of silicic acid biomass.
The method for utilizing silica biomass in a blast furnace, in which the sintered ore produced in this manner is charged into the top of the blast furnace, is another embodiment of the present invention. Note that, here, the method for producing sintered ore according to this embodiment and the method for utilizing silica biomass in a blast furnace according to other embodiments will be described together without distinguishing between them.

The method for producing sintered ore according to an embodiment of the present invention is primarily comprised of substituting biochar obtained by dry distillation of silicate biomass for the silicon oxide portion of the carbonaceous material and component-adjusted flux used as the granulation raw material, but is otherwise the same as a typical method for producing sintered ore. Therefore, we will begin by explaining the typical method for producing sintered ore, which is the premise of this embodiment.

As shown in Figure 1, the raw material for sintered ore is prepared by blending fine iron ore, a composition-adjusted solder, return ore (sintered ore powder of a size that cannot be used as a blast furnace feedstock), and carbonaceous material. The blend is then granulated in a drum mixer while adjusting the moisture content to form pseudo-particles, which are then sintered. By converting the granulated raw material, the raw material for sintered ore, into pseudo-particles, the permeability of the pseudo-particles can be improved when the pseudo-particles are loaded into a sintering machine, such as a Dwight Lloyd sintering machine, and sintering proceeds smoothly. These pseudo-particles are composed of core particles of granulated raw material, primarily granular iron ore with a particle size of approximately 10 mm to 1 mm. These pseudo-particles are composed of core particles surrounded by powder particles such as fine iron ore, composition-adjusted solder, sintered ore powder (return ore), and coke powder, each with a particle size of 1 mm or less, which adhere to the core particles due to added moisture. Fine iron ore refers to iron ore powder, iron-containing dust, scale, and other raw materials that contain a large amount of iron. In order to average out the different compositions of iron ores from each mine, the iron ore in fine iron ore is usually blended with other fine ores. The composition-adjusting slag material mainly consists of CaO-based auxiliary materials such as limestone and _SiO2- based auxiliary materials such as silica and various smelting slags. The carbonaceous material serves as fuel for the combustion reaction during sintering, and anthracite, coke powder, etc. are used.

This pseudo-granulated sinter raw material is loaded onto the pallet of a moving grate sinter machine, and a burner in an ignition furnace on the entry side ignites the carbonaceous materials such as coke present on the surface of the packed bed. In a bottom-suction sinter machine, air is sucked in from above the packed bed and ventilated below, and the heat of combustion of the carbonaceous materials is transferred from the upper layer to the lower layer, progressing the sintering process, which is completed when the pallet moves to the exit side of the sinter machine. The resulting sinter cake is crushed and sized to produce sintered ore with an average particle size of 3 to 5 mm.

The main component composition of the granulated raw material used as the sintering raw material is typically 55-57% by mass of total iron, 9-10% by mass of CaO, 5-5.3% by mass of SiO ₂ , 1.7-1.8% by mass of Al ₂ O ₃ , and 1-20% by mass of MgO. The amount of carbonaceous material added as a heat source is approximately 5% by mass of the granulated raw material. When a sintered raw material with this component composition is heated and sintered, CaO and iron oxide (Fe ₂ O _{3 )} react with each other at around 1200°C to generate an initial molten liquid. Subsequently, as the temperature rises, gangue (slag) components such as SiO ₂ , Al ₂ O ₃ , and MgO, as well as iron oxide, melt (assimilate) into the molten liquid, and the coarse iron ore particles are bonded together through this molten liquid, resulting in sintering.

As mentioned above, the main reactions in the sintering reaction are the initial melt formation caused by the reaction between _Fe2O3 in the iron ore _and CaO in the limestone, followed by the melting reaction of this melt with the auxiliary materials and gangue components such as _SiO2 and iron oxide in the iron ore. This reaction is called the assimilation reaction. For example, if the assimilation reaction proceeds excessively and the amount of melt generated increases dramatically, uneven sintering occurs due to poor permeability in the sintered layer, significantly reducing yield and strength. On the other hand, if the assimilation reaction does not proceed, the amount of melt that bonds unmelted iron ore particles together decreases, resulting in a decrease in product yield and strength of the sintered ore. This sintering reaction can be controlled by controlling the basicity (CaO/SiO2 ₎ of the melt generated during sintering within a predetermined range using a composition-adjusting flux in the granulation raw material.

The method for producing sintered ore according to this embodiment involves controlling the basicity (CaO/SiO2 ₎ of the melt produced during sintering within a predetermined range by using silicon oxide contained in biochar derived from silicic acid biomass as the _SiO2 -based auxiliary material in the composition-adjusting flux blended with the granulated raw material. The predetermined range for the basicity (CaO/SiO2 ₎ is, for example, 1.0 to 2.0. At the same time, in this embodiment, the fixed carbon contained in the biochar derived from silicic acid biomass, together with the silicon oxide, is also utilized as a carbonaceous material blended with the granulated raw material and used as a heat source.

In the case of the biochar derived from silicic acid biomass according to this embodiment, the fixed carbon as a carbonaceous material and the silicon oxide as the silicon oxide component of the component-adjusted flux can already be said to be mixed together, but this does not pose any problems. The biochar derived from silicic acid biomass according to this embodiment can also be mixed with other granulated raw materials such as fine iron ore by going through the steps of a conventional sintered ore manufacturing method.

Silicate biomass refers to plants containing silica (silica plants) or parts thereof such as their leaves and stems, and includes rice and wheat husks and straw, bamboo leaves, and corn leaves and stems. Biochar derived from siliceous biomass is a carbonaceous material obtained by dry distilling siliceous biomass. The dry distillation method is not important, but dry distillation using a rotary kiln is an example. As mentioned above, biochar derived from siliceous biomass has a fixed carbon content of approximately 15-50% by mass, an ash content of approximately 30-50% by mass, and a unit calorific value of approximately 14-28 MJ/kg.

The carbonaceous material in the granulated raw material serving as the sintering raw material related to this embodiment, which is to be replaced with fixed carbon in biochar derived from silicic acid biomass in this embodiment, is the same anthracite pulverized coal and coke breeze that are commonly used in sinter ore manufacturing methods. In this embodiment, some or all of these are replaced with fixed carbon in biochar derived from silicic acid biomass and used as the carbonaceous material. The fixed carbon in biochar derived from silicic acid biomass used here is a carbon-free carbon source and has the effect of reducing _CO2 emissions generated by the coal-derived carbonaceous material before replacement.

In blast furnace operation, ensuring the air permeability and liquid permeability around the cohesive zone is one of the most important management issues. Therefore, the amounts of auxiliary materials, such as limestone and silica, blended with raw materials such as iron ore, are usually adjusted to keep the basicity (CaO/SiO2 ₎ of the melt of all raw materials charged to the blast furnace within a predetermined range. The amount of the composition-adjusting melt in this embodiment is preferably controlled so that the basicity (CaO/SiO2 ₎ of the melt in the blast furnace falls within a predetermined range, even for sintered ore alone. Therefore, it is preferable to prioritize the adjustment of the basicity of the melt during the assimilation reaction of sintered ore, while also taking into consideration the basicity of the melt in the blast furnace.

The basicity (CaO/ _SiO2 ) of the entire sintering raw material can be adjusted by adjusting the blending pattern of each raw material so that the basicity calculated from the total amount of CaO and _SiO2 contained in each of the fine iron ores and the composition-adjusted melt is within a predetermined range.

In this embodiment, some or all of the silicon oxide content of the composition-adjusted welding material is replaced with silicon oxide in biochar derived from silicate biomass, without changing the silicon oxide content of the entire sintered ore. Therefore, using biochar derived from silicate biomass in sintered ore does not adversely affect the assimilation reaction during the production of sintered ore.

In the sinter ore manufacturing method according to this embodiment, a specific preferred embodiment that maximizes the use of biochar derived from silicic acid biomass will be described. First, because the fixed carbon and silicon oxide amounts per unit amount of biochar derived from silicic acid biomass are expected to fluctuate, the fixed carbon and silicon oxide amounts per unit amount of the incoming biochar derived from silicic acid biomass are confirmed. Next, of the confirmed fixed carbon and silicon oxide amounts, any of the fully applicable blended raw materials for the granulated raw material to be used as the sintering raw material is completely substituted, while the other blended raw material that is insufficient is partially substituted, thereby determining the blending ratio of the raw materials. It goes without saying that in this embodiment, the fixed carbon and silicon oxide amounts of the biochar derived from silicic acid biomass may each be used as part of the blended raw materials for the sinter ore.

Here, we will explain the results of calculations in which the carbonaceous material in the normal granulated raw material used as the sintering raw material and the _SiO2 -based auxiliary material in the component-adjusting flux are equivalently replaced with the fixed carbon and silicon oxide in the biochar derived from silicic acid biomass.

The raw materials to be blended into the normal granulated raw materials, which are the sinter raw materials used in the calculations, are assumed to be mixed iron ore as fine iron ore and limestone and silica as composition-adjusting sintering materials. Furthermore, regarding the silicon oxide content and _SiO2 and CaO used to calculate the basicity of the entire granulated raw materials, which are the subject of the calculations, strictly speaking, the contents in the fine iron ore and return ore must also be taken into account. However, for simplicity, the calculations were made using only the raw materials for composition-adjusting sintering materials. Furthermore, carbonaceous materials are consumed as a heat source for sintering and do not remain in the final sintered ore product, so they are shown as separate quantities relative to the other granulated raw materials.

The components and overall properties of the normal granulated raw material that will be used as the sintering raw material for the specific calculation are as follows:
Fine iron ore (mixed iron ore): 58.1% by mass
・Component adjustment welding materials (the following two types)
・・Limestone: 17.9% by mass
・・Silica stone: 5.0% by mass
・Return ore: 19.0% by mass
Carbon material (coke powder) (extraneous number): 4.0% by mass
Overall properties of granulated raw material Basicity CaO/SiO2: _2.0

The biochar derived from silicate biomass was rice husk charcoal dry-distilled at 500°C, and its composition was as follows:
・Fixed carbon: 28% by mass
Volatile content: 35% by mass
・Ash content: 38% by mass (including SiO ₂ : 34% by mass)

Under the above preconditions, of the 40 kg of carbonaceous material and 50 kg of silica ( _SiO2 ) in 1 ton of granulated raw material to be used as sintering raw material, if we first try to use the fixed carbon in biochar to cover all of the 40 kg of carbonaceous material, the amount of biochar required will be 143 kg.
Biochar as a substitute for carbon: 40 (kg) / 28 (%) = 143 (kg)
In this case, ₄₉ kg of SiO2 in the biochar will also be blended at the same time, but including errors, this is equivalent to the required amount of 50 _kg of SiO2 to be substituted and the basicity CaO/SiO2 of _2.0 , and it can be seen that it is possible to use biochar to fill the gap.
Simultaneously blended SiO ₂ : 143 (kg) × 34 (%) = 49 (kg)
CaO in limestone: 179 (kg) x 56 (%) = 100 (kg)
Basicity CaO/SiO ₂ : 100 (kg)/49 (kg)=2.0

Just to be sure, we calculated the case where, of the 40 kg of carbonaceous material and 50 kg of silica ( _SiO2 ) in 1 ton of granulated raw material used as sintering raw material, all 50 kg of silica was replaced with silicon oxide in biochar, but the results were the same as when the carbonaceous material was replaced with fixed carbon in biochar.
・Biochar as a substitute for silica: 50 (kg) / 34 (%) = 147 (kg)
In this case, 41 kg of fixed carbon in biochar is also blended in at the same time, and it can be seen that almost the entire amount of 40 kg of the required carbon material to be replaced can be used.
Fixed carbon simultaneously blended: 147 (kg) x 28 (%) = 41 (kg)

Claims (2)

A method for producing sintered ore by a Dwight Lloyd sintering machine using a granulated raw material that is a blend of fine iron ores, a composition-adjusted melting material, return ore, and a carbonaceous material,
A method for producing sintered ore, in which part or all of the carbonaceous material and part or all of the silicon oxide content of the component-adjusted welding material are replaced with fixed carbon and silicon oxide in biochar obtained by dry distillation of silicate biomass. A method for utilizing silicic acid biomass in a blast furnace, comprising: charging sintered ore produced from a granulated raw material that is a blend of fine iron ores, a composition-adjusted solder, return ore, and a carbonaceous material, in which part or all of the carbonaceous material and part or all of the silicon oxide content of the composition-adjusted solder are replaced with fixed carbon and silicon oxide in biochar obtained by dry distillation of silicic acid biomass, into the top of a blast furnace.