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

Abstract

The present invention provides a method for producing sintered ore using biochar derived from silicic acid biomass and a method for utilizing silicic acid biomass in a blast furnace. In the method for producing sintered ore using a Dwight Lloyd sinter machine, a granulated raw material containing fine iron ores, a composition-adjusting solder, return ore, and a carbonaceous material is used. Some or all of the carbonaceous material and some or all of the silicon oxide content of the composition-adjusting solder blended in the granulated raw material are replaced by fixed carbon and silicon oxide in biochar obtained by carbonizing silicic acid biomass. In the method for utilizing silicic acid biomass in a blast furnace, the sintered ore obtained as described above is charged into the top of a blast furnace.

Description

[Technical Field]

[0001] The present invention relates to a method for producing sintered ore and a method for utilizing silica biomass in a blast furnace. [Background technology]

[0002] 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 mixture of iron ore, SiO2-based auxiliary materials such as silica, CaO-based auxiliary materials such as limestone, sintered ore return ore of a certain size, and carbonaceous materials such as coke fines. The auxiliary materials added during the production of sintered ore are used to adjust the sinterability of the sintered ore. Furthermore, by using the auxiliary materials as gangue components of the sintered ore and as a source of blast furnace slag, they are also used to improve the fluidity of the slag in the blast furnace. For example, Patent Document 1 discloses an invention in which sintered raw material is made by adding auxiliary materials containing SiO2 and / or MgO to the granulated raw material at 1.5 to 6 wt% of the granulated raw material to form pseudo-particles, which 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 also claims to maintain smooth blast furnace operation without lowering the furnace top temperature.

[0003] 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.

[0004] In a typical downward suction type sintering machine such as a Dwight Lloyd type sintering machine, a large amount of coal (anthracite) and coke breeze are used as the carbonaceous material, which generates a large amount of carbon dioxide gas. In response to this problem, Patent Document 2 discloses an invention that uses biochar, oil palm kernel shell charcoal, as a carbon-free carbon source for the carbonaceous material during sintering. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 08-085829 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-237876 Summary of the Invention [Problem to be solved by the invention]

[0006] Meanwhile, expanding the 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, has become a problem. This is because biochar derived from silicate biomass can be problematic due to its high ash content of approximately 30-50%. Furthermore, biochar derived from silicate biomass not only promises a stable supply, but also possesses sufficient properties as a carbon source, with a fixed carbon content of approximately 15-50% and a unit calorific value of approximately 14-28 MJ / kg.

[0007] Previous studies of biochar as a carbon-free carbon source in steelworks have not fully 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 production process, also fails to explicitly address the issue of high ash content in biochar derived from silicate biomass. The biochar described in this document is oil palm kernel shell charcoal, and the major components of the biochar exemplified in this 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 this document for the target coke breeze are 86.0% by mass fixed carbon, 12.9% by mass ash, and 1.1% by mass volatile matter. The target anthracite coal has 88.5% by mass fixed carbon, 5.0% by mass ash, and 6.4% by mass volatile matter. This is probably because the component composition of oil palm kernel shell coal is the same as that of its substitutes, coke breeze and anthracite, and there is no need to particularly address the issue of ash content.

[0008] 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 is used as a heat source for sintering in the production of 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.

[0009] Therefore, an object of the present invention is 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. [Means for solving the problem]

[0010] [1] A method for producing sintered ore by a Dwight Lloyd sintering machine using a granulated raw material containing fine iron ore, 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 silicate biomass in a blast furnace, comprising charging the sintered ore produced from a granulated raw material containing a blend of fine iron ores, composition-adjusted solder, return ore, and 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 carbonizing silicate biomass, into the top of the blast furnace.

[0011] According to the present invention, the fixed carbon in the biochar derived from silicic acid biomass replaces part or all of the carbonaceous material in the granulation raw material, thereby contributing to the reduction of CO2 emissions in the steel industry. Furthermore, according to the present invention, the silicon oxide in the composition-adjusted welding material in the granulation raw material is replaced part or all of the silicon oxide in the biochar derived from silicic acid biomass, without adversely affecting the basicity of the melt during sintering or in the 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 granulation raw material and the SiO2-based auxiliary material in the composition-adjusted welding material, thereby providing an advantage 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 the 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. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a flowchart illustrating a method for producing sintered ore according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The sintered ore according to the embodiment of the present invention is one of the raw materials charged into the top of a blast furnace. Iron ore as a blast furnace raw material can be efficiently used in various forms, such as lump ore that can be charged as is, or by changing the form depending on the state of the raw material. For example, fine ore that would otherwise impair the air permeability inside the furnace can be sintered to form sintered ore, or iron-containing dust recovered in a steelworks can be agglomerated with hydraulic cement to form unsintered agglomerated ore.

[0014] 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, composition-adjusted solder, return ore, and carbonaceous material, as shown in Figure 1. In this process, some or all of the carbonaceous material and some or all of the silicon oxide content of the composition-adjusted 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.

[0015] The method for producing sintered ore according to the embodiment of the present invention is essentially the same as a conventional method for producing sintered ore, except that biochar obtained by dry distillation of silicate biomass is used to replace the silicon oxide content of the carbonaceous material and the composition-adjusting melting material used as granulation raw materials. Therefore, the conventional method for producing sintered ore, which is the premise of this embodiment, will be described first.

[0016] As shown in Figure 1, the raw material for sintering is a mixture of fine iron ore, composition-adjusted solder, return fines (sintered ore powder of a size that cannot be used as blast furnace feed), and carbonaceous material. The mixture 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, which is the raw material for sintering, into pseudo-particles, the permeability during sintering in a sintering machine such as a Dwight-Lloyd sintering machine is improved, resulting in better sintering. These pseudo-particles are made from granular iron ore core particles with a particle size of approximately 10 mm to 1 mm or more. These pseudo-particles are formed by adding moisture to the core particles and attaching fine particles such as fine iron ore, composition-adjusted solder, sintered ore powder (return fines), and coke powder with a particle size of 1 mm or less to the core particles. Fine iron ore refers to iron-rich raw materials such as iron ore fines, iron-containing dust, and scale generated during the steelmaking process. In order to average out the different compositions of iron ore from each mine, the iron ore in fine iron ore is usually blended with other fine ores. The composition-adjusting materials consist mainly of CaO-based auxiliary materials such as limestone, and SiO2-based auxiliary materials such as silica and various smelting slags. The carbonaceous material is the fuel for the combustion reaction during sintering, and anthracite, coke breeze, etc. are used.

[0017] This pseudo-granulated sinter raw material is loaded onto a pallet in a moving-grate sinter machine, and a burner in an ignition furnace on the inlet side ignites the carbonaceous material, 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 passed downward, and the heat of combustion of the carbonaceous material is transferred from the upper layer to the lower layer, progressing the sintering process, which is completed when the pallet moves to the outlet 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.

[0018] The main components of the granulated raw material used as the sintering material are typically 55-57% by mass of T.Fe, 9-10% by mass of CaO, 5-5.3% by mass of SiO2, 1.7-1.8% by mass of Al2O3, 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 sintered raw materials with this composition are heated and sintered, CaO and iron oxide (Fe2O3) react with each other at around 1200°C, generating an initial molten liquid. Subsequently, as the temperature rises, gangue (slag) components such as SiO2, Al2O3, 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.

[0019] As mentioned above, the main reaction in the sintering process is the reaction between Fe2O3 in the iron ore and CaO in the limestone to form an initial melt. This melt then melts with the auxiliary materials, gangue components such as SiO2 in the iron ore, and iron oxide. This reaction is called the assimilation reaction. For example, if the assimilation reaction proceeds excessively and the amount of melt produced increases dramatically, the permeability of the sintered layer decreases, resulting in uneven sintering and a significant decrease in 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 sinter strength. This sintering reaction can be controlled by using a composition-adjusting flux in the granulation raw material to maintain the basicity (CaO / SiO2) of the melt produced during sintering within a specified range.

[0020] The method for producing sintered ore according to this embodiment involves controlling the basicity (CaO / SiO2) of the sintered ore melt within a predetermined range by using silicon oxide contained in biochar derived from silicic acid biomass as an SiO2-based auxiliary material in a 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, along with the silicon oxide, is also utilized as a carbonaceous material blended with the granulated raw material and used as a heat source.

[0021] In the biochar derived from silicic acid biomass according to the present embodiment, the fixed carbon as the carbonaceous material and the silicon oxide as the silicon oxide component of the composition-adjusting flux are already mixed together, but this does not pose any problems. The biochar derived from silicic acid biomass according to the present embodiment can also be mixed with other granulated raw materials such as fine iron ore by going through the steps of a conventional method for producing sintered ore.

[0022] Silica biomass refers to plants containing silica (silica plants) or parts thereof such as their leaves and stems, including rice and wheat husks and straw, bamboo leaves, and corn leaves and stems. Biochar derived from silica biomass is a carbonaceous material obtained by dry distillation of silica biomass. While any dry distillation method can be used, dry distillation using a rotary kiln is an example. As mentioned above, silica biomass-derived biochar has a fixed carbon content of approximately 15 to 50% by mass, an ash content of approximately 30 to 50% by mass, and a unit calorific value of approximately 14 to 28 MJ / kg.

[0023] The carbonaceous material in the granulated raw material used as the sintering raw material in this embodiment, which is to be replaced with fixed carbon in biochar derived from silicate biomass, 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 silicate biomass and used as the carbonaceous material. The fixed carbon in biochar derived from silicate 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.

[0024] In blast furnace operation, ensuring the gas 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 molten liquid of all raw materials charged to the blast furnace within a predetermined range. The blending amount of the composition-adjusting melt in this embodiment is preferably controlled so that the basicity (CaO / SiO2) of the molten liquid in the blast furnace is within a predetermined range, even for sintered ore alone. Therefore, it is preferable to prioritize the adjustment of the basicity of the molten liquid during the assimilation reaction of sintered ore, while also taking into consideration the basicity of the molten liquid in the blast furnace.

[0025] The basicity (CaO / SiO2) of the entire sintering raw materials 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 falls within a predetermined range.

[0026] In this embodiment, a part or all of the silicon oxide content of the composition-adjusted welding material is replaced with silicon oxide in biochar derived from silicic acid biomass without changing the silicon oxide content of the entire sintered ore. Therefore, even if biochar derived from silicic acid biomass is used for sintering, it does not adversely affect the assimilation reaction during the production of sintered ore.

[0027] In the method for producing sintered ore 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, if any of the blended raw materials can be fully used as a blended raw material for the granulated raw material to be sintered, the blended raw material ratio is determined by completely substituting the remaining blended raw material, and partially substituting the remaining blended raw material. It goes without saying that in this embodiment, the fixed carbon and silicon oxide amounts of the biochar derived from silicic acid biomass may be partially used as a blended raw material for the sintered ore.

[0028] 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 replaced equivalently with the fixed carbon and silicon oxide in the biochar derived from silicic acid biomass.

[0029] The raw materials used to blend the normal granulated raw materials, which serve as the sintering raw materials for this calculation, are assumed to be mixed iron ore as fine iron ore, and limestone and silica as composition-adjusting materials. Strictly speaking, the silicon oxide content and SiO2 and CaO used to calculate the basicity of the entire granulated raw materials, which are the subject of this calculation, also need to be taken into account in the content of fine iron ore and return ore. However, for simplicity's sake, this calculation only covers the raw materials used in composition-adjusting 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.

[0030] 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: 5.0% by mass ·Return ore: 19.0 mass% Carbon material (coke powder) (extraneous value): 4.0% by mass Overall properties of granulation raw materials Basicity CaO / SiO2: 2.0

[0031] 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 SiO2: 34% by mass)

[0032] Based on the above assumptions, if we were to first use the fixed carbon in biochar to cover all 40 kg 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, then the amount of biochar required would 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 mixed in 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, so it is clear that it is possible to use biochar to fill the gap. SiO2 simultaneously blended: 143 (kg) x 34 (%) = 49 (kg) CaO in limestone: 179 (kg) x 56 (%) = 100 (kg) Basicity CaO / SiO2: 100 (kg) / 49 (kg) = 2.0

[0033] Just to be sure, we calculated what would happen if the 40 kg of carbonaceous material and 50 kg of silica (SiO2) in 1 ton of granulated raw material used as sintering material were replaced entirely with silicon oxide from biochar, but the results were the same as when the carbonaceous material were replaced with fixed carbon from biochar. Biochar as a substitute for silica: 50 kg / 34% = 147 kg In this case, 41 kg of fixed carbon in biochar is also mixed in, meaning that almost the entire 40 kg of required carbon material can be used as a replacement. Fixed carbon added simultaneously: 147 (kg) x 28 (%) = 41 (kg)

Claims

1. 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 silicic acid biomass, which is a plant containing silica, including rice husks and straw of rice, wheat, etc., bamboo leaves, corn leaves and stalks, etc.

2. A granulated raw material is a blend of fine iron ores, a composition-adjusted solder, return ore, and a carbonaceous material, and a part or all of the carbonaceous material and a part or all of the silicon oxide content of the composition-adjusted solder are filled with fixed carbon and silicon oxide in biochar obtained by dry distillation of silica biomass, which is a plant containing silica, including rice husks and straw of rice, wheat, etc., bamboo leaves, corn leaves and stalks, etc. When sintered ore is produced using the granulated raw material, it is charged from the top of a blast furnace, The method for utilizing silicate biomass in a blast furnace involves adjusting the blending amount of auxiliary materials into the blast furnace so that the basicity CaO / SiO 2 of the molten liquid of all raw materials charged into the blast furnace falls within a predetermined range depending on the amount of silicon oxide contained in the sintered ore.

Images