Method for producing non-sintered carbon-containing briquettes and method for blast furnace utilization of siliceous biomass

Abstract

According to the present application, it is possible to provide a non-sintered carbon-containing lump ore manufacturing method effectively using biochar from siliceous biomass and a siliceous biomass blast furnace utilization method. In the present application relating to the non-sintered carbon-containing lump ore manufacturing method, a mixed raw material containing an iron-containing raw material, a carbon-containing raw material, a gangue raw material, and a binder is used, formed into a lump, and cured for a prescribed period, thereby manufacturing a non-sintered carbon-containing lump ore. The fixed carbon and silicon oxide in the biochar obtained by subjecting the siliceous biomass to dry distillation treatment are used as part or all of the carbon-containing raw material in the mixed raw material used at this time and part or all of the silicon-containing ore in the gangue raw material. In addition, in the present application relating to the siliceous biomass blast furnace utilization method, the non-sintered carbon-containing lump ore obtained as described above is charged from the top of the blast furnace.

Description

Technical Field

[0001] This invention relates to a method for manufacturing unfired carbon-containing agglomerated ore and a method for utilizing siliceous biomass in a blast furnace. Background Technology

[0002] From the perspective of preventing global warming, reducing CO2 emissions is an urgent issue, and technologies for reducing CO2 emissions have also been developed in the steel industry. Methods for reducing CO2 emissions include (a) reducing the amount of carbon input, (b) recovering produced CO2, and (c) replacing traditional sources such as coal and oil with carbon-free carbon sources.

[0003] Previously, various iron-containing dusts and carbon-containing dusts recovered from dust collection devices in ironmaking plants were reused. This is related to resource conservation and is therefore relevant to the method of reducing the amount of carbon input mentioned in (a) above. In order to reuse the recovered iron-containing dusts and carbon-containing dusts as blast furnace feedstock (also known as blast furnace charging feedstock), there is a technology that involves adding cement-based hydraulic binders to the ore, mixing and shaping it to produce unburned agglomerates with a diameter of 8 to 16 mm. When these unburned agglomerates contain carbon materials as a reducing agent, they are also called unburned carbon-containing agglomerates, based on the clear intention of containing carbon materials.

[0004] In the production of unburnt carbonaceous agglomerates, quicklime and CaO-based cement are often used as binders, resulting in a high CaO content in the finished product. Consequently, the viscosity of the molten liquid generated from the unburnt carbonaceous agglomerate during the reaction in the blast furnace becomes excessively high. This hinders the agglomeration and molten dripping of the generated metal, leading to a deterioration in the ventilation and liquid flow of the lower part of the blast furnace.

[0005] To address this problem, the following invention is disclosed in Patent Document 1: (e.g.) Figure 1 As shown, by setting the basicity (CaO / SiO2) of the gangue component in the unburned carbonaceous agglomerate ore to 1.0-2.0, the melting point of the slag generated in the lower part of the furnace is reduced, and the aeration and liquid flow properties are improved. Furthermore, in this document, in order to achieve a basicity (CaO / SiO2) of 1.0-2.0 in the unburned carbonaceous agglomerate ore, it is preferable to adjust the amount of high SiO2 content ore (also known as silica-containing ore) in the blend.

[0006] Furthermore, in connection with the method described in (c) above of replacing conventional coal, oil, etc., with carbon-free carbon sources, various technologies for the effective utilization of biomass as a carbon-free carbon source in ironmaking plants have been developed. For example, Patent Document 2 discloses the process of pulverizing biochar obtained from the dry distillation of biomass to produce pulverized coal (PC), which is then fed from the blast furnace tuyeres 3 (see reference 3). Figure 2 This invention relates to the PCI (Pulverized Coal Injection) technology, which involves blowing in pulverized coal. It should be noted that, in the invention described in this document, the examples of applicable biomass include fir and coconut tree trunks, coconut shells, and other biomass that can be widely used to generate carbon compounds through thermal decomposition, including agricultural, forestry, livestock, aquaculture, and waste-based biomass.

[0007] Existing technical documents Patent documents Patent Document 1: International Publication No. 2011 / 021577 Patent Document 2: Japanese Patent Application Publication No. 2011-117075 Summary of the Invention

[0008] The problem that the invention aims to solve However, expanding the utilization of biomass such as rice husks and straw (also known as siliceous biomass due to its high ash content), which accounts for over 2 million tons annually in China as a carbon-free source, has become problematic. This is because biochar derived from siliceous biomass sometimes has an ash content as high as 30-50%, posing a challenge. It should be noted that biochar derived from siliceous biomass not only offers a stable supply but also possesses sufficient characteristics as a carbon source, with a fixed carbon content of approximately 15-50% and a calorific value of approximately 14-28 MJ / kg.

[0009] Previous studies on the effective utilization of biochar as a carbon-free carbon source in ironmaking plants have not adequately addressed the high ash content issue of biochar derived from siliceous biomass. Even in the invention describing the effective use of biochar in the pulverized coal injection (PCI) technology described in Patent Document 2, the high ash content of biochar derived from siliceous biomass was not explicitly disclosed. This may be because, as... Figure 2 As shown in the document, the fine pulverized coal PC is blown in along with hot blast from the lower tuyeres 3 of the blast furnace 1, simultaneously generating high-temperature reducing gases in the combustion zone 5, and the ash is absorbed into the surrounding slag. Therefore, the ash content in the fine pulverized coal PC is not a problem. However, when using biochar with high ash content as a carbon material to replace fine pulverized coal PC, it is necessary to be aware that the temperature in the lower part of the furnace may decrease, potentially leading to furnace instability.

[0010] On the other hand, it is necessary to study whether the carbon material in the non-fired carbon-containing agglomerate described in Patent Document 1 can use biochar derived from siliceous biomass with a high ash content. This is because, for the non-fired carbon-containing agglomerate charged from the furnace top 2 of the blast furnace, the ash content of the non-fired carbon-containing agglomerate directly affects the gas permeability and liquid permeability around the cohesive zone 4 in the lower part of the furnace, which is the problem of Patent Document 1.

[0011] Accordingly, an object of the present invention is to provide a method for producing a non-fired carbon-containing agglomerate that effectively utilizes biochar derived from siliceous biomass, and a method for utilizing siliceous biomass in a blast furnace.

[0012] Means for Solving the Problem [1] A method for producing a non-fired carbon-containing agglomerate, which is a method for producing a non-fired carbon-containing agglomerate by forming a compounded raw material containing an iron-containing raw material, a carbon-containing raw material, a gangue raw material and a binder into an agglomerate and curing the agglomerate for a predetermined period, wherein The fixed carbon and silica in the biochar obtained by carbonizing siliceous biomass are used to replace part or all of the carbon-containing raw material and part or all of the silicon-containing ore in the gangue raw material.

[0013] [2] A method for utilizing siliceous biomass in a blast furnace, comprising: using fixed carbon and silica in biochar obtained by carbonizing siliceous biomass to replace part or all of the carbon-containing raw material and part or all of the silicon-containing ore in the gangue raw material in a compounded raw material containing an iron-containing raw material, a carbon-containing raw material, a gangue raw material and a binder, charging the non-fired carbon-containing agglomerate produced by forming the above compounded raw material into an agglomerate and curing it for a predetermined period from the furnace top of the blast furnace.

[0014] According to the present invention, since part or all of the carbon-containing raw material of the non-fired carbon-containing agglomerate is replaced with fixed carbon in biochar derived from siliceous biomass, it is possible to contribute to the reduction of CO₂ emissions in the iron and steel industry. In addition, according to the present invention, part or all of the silicon-containing ore in the gangue raw material of the non-fired carbon-containing agglomerate can be replaced with silica in biochar derived from siliceous biomass without changing the gangue components charged into the blast furnace. Therefore, no adverse effect is exerted on the gas permeability and liquid permeability around the cohesive zone in the lower part of the furnace. Further, according to the present invention, by using the biochar derived from siliceous biomass, which is produced in large quantities domestically every year, as a raw material containing both a carbon-containing raw material and a gangue raw material in the compounded raw materials of the non-fired carbon-containing agglomerate, there is an effect of being advantageous in terms of procurement. On the other hand, according to the present invention, it is possible to provide a new use that can effectively utilize both fixed carbon and silica in biochar derived from siliceous biomass whose uses are limited due to its high ash content.

[0015] As described above, according to the present invention, a method for manufacturing non-calcined carbonaceous agglomerates that does not adversely affect the aeration and liquid flow in the fusion zone at the bottom of the furnace, and a method for utilizing siliceous biomass in blast furnaces can be provided. Attached Figure Description

[0016] Figure 1 The graph is a representation of the relationship between CaO / SiO2 and metal dripping rate in unburned carbonaceous agglomerates disclosed in Patent Document 1.

[0017] Figure 2 It is a schematic longitudinal cross-sectional view of a blast furnace used to illustrate the general process of producing molten iron from iron ore in a blast furnace.

[0018] Figure 3 This is a flowchart illustrating a method for manufacturing non-calcined carbonaceous agglomerate ore according to embodiments of the present invention. Detailed Implementation

[0019] The non-burnt carbonaceous agglomerate ore (hereinafter, sometimes simply referred to as carbonaceous agglomerate ore, or further simply referred to as agglomerate ore) in embodiments of the present invention is one of the raw materials charged from the top of the blast furnace. Besides lump ore that can be directly charged, the iron ore used as raw material for the blast furnace can be efficiently utilized by changing its form according to its condition. For example, sintered ore, which directly impairs the aeration of the furnace (iron ore fines), can be sintered and solidified; and non-burnt agglomerate ore, which is formed by using hydraulic cement to form iron-containing dust recovered from the ironmaking plant, can be efficiently utilized by changing its various forms.

[0020] Here, use Figure 2 A brief overview of the process of producing molten iron from iron ore using a blast furnace is provided. In blast furnace operation, iron ore and coke are first charged into the furnace 1 from the top 2 in an alternating layered manner, allowing them to descend within the furnace in a way that minimizes disruption to the layer structure (not shown). Hot blast and pulverized coal, serving as a supplementary reducing agent to the coke, are blown in from the tuyeres 3 located at the bottom of the furnace. In the combustion zone 5 formed by this hot blast (also called the swirling zone), the pulverized coal and coke burn to produce high-temperature reducing gases such as carbon monoxide and hydrogen. These reducing gases become a violently rising airflow that blows through the furnace, heating the descending iron ore and thus indirectly reducing it.

[0021] As the iron ore melts and descends within the furnace, a dense, semi-molten fusion zone 4, appearing as a ring when viewed from above, forms between the solid and liquid layers. This fusion zone 4 acts as a rectifier for the rising high-temperature gas. A relatively large amount of high-temperature gas flows through the thinner layer of iron ore in the center, thus preferentially forming a fusion layer from the upper center of the furnace, resulting in an inverted V-shaped layer. The rising high-temperature gas flows along the inverted V-shaped fusion zone 4 towards the upper center, and the gas, initially concentrated at the central axis, is redistributed evenly to the periphery of the furnace via the coke layer.

[0022] As the molten iron drips down the coke layer, it comes into contact with the carbon in the coke and is further directly reduced, becoming molten iron containing less than 5% carbon, which accumulates in the hearth 6 at the bottom of the furnace. This molten iron is taken out from the taphole 7 located horizontally at the bottom of the furnace and transported to the next steelmaking process. Simultaneously with tapping the iron, slag, obtained from the melting and separation of impurities in the iron ore such as silica and alumina, is also discharged and reused as a byproduct in cement materials, etc.

[0023] like Figure 3 As shown, for the non-fired carbonaceous agglomerates of the embodiments of the present invention, a compound containing iron-containing raw materials, carbonaceous raw materials, gangue raw materials, and binders is formed into agglomerates and cured for a specified period. The specified curing period can be exemplified as approximately 1 to 3 weeks. During this time, fixed carbon and silicon dioxide from biochar obtained by dry distillation of siliceous biomass are used as part or all of the carbonaceous raw materials and part or all of the silica-containing ore in the gangue raw materials.

[0024] Another embodiment of the invention is the blast furnace utilization method of unburned carbonaceous agglomerates, which are thus manufactured, being charged from the top of the blast furnace into siliceous biomass. It should be noted that, here, both are described together without distinction.

[0025] exist Figure 3In this example, the raw materials, including iron-containing raw materials, carbon-containing raw materials, and gangue raw materials, are mixed using a ball mill to adjust the particle size distribution to an appropriate range before blending. It should be noted that in the biochar from siliceous biomass of this embodiment, the fixed carbon as the carbon-containing raw material and the ash as the gangue raw material are already mixed, but this is not a problem. The biochar from siliceous biomass of this embodiment also undergoes the conventional process of mixing with other raw materials, such as iron-containing raw materials, while adjusting the particle size. Then, a binder and approximately 5-15% moisture, corresponding to the amount of binder, are added to the mixed raw materials, and the mixture is blended using a mixer. The blended raw materials are further granulated using a disc granulator (also called a rotary disc granulator) to form granules. The curing of the formed green pellets is typically about 2 weeks under natural curing conditions, but is not limited to this; it can be adjusted to a period of about 1-3 weeks depending on the raw material blending ratio, curing conditions such as temperature and humidity, and the necessary characteristics of the agglomerate.

[0026] Examples of iron-containing raw materials used in this embodiment include sintering dust and blast furnace dust generated during the ironmaking process, pellet feed with a particle size smaller than that of sintering powdered iron ore, and micro-powdered iron ore produced by crushing and / or granulating sintering powdered iron ore. By reusing various iron-containing dusts recovered from the ironworks and effectively utilizing powdered ore (iron fines) not used for sintering, CO2 emissions can be reduced.

[0027] In this embodiment, the carbon-containing raw materials used, which are replaced by fixed carbon from biochar derived from siliceous biomass, are the same as those typically used in unburned agglomerated ore, such as blast furnace primary ash (dry dust collection), coke powder, micronized coke, and anthracite. In this embodiment, some or all of these are replaced by fixed carbon from biochar derived from siliceous biomass and used as carbon-containing raw materials. The fixed carbon in the biochar derived from siliceous biomass used here is a carbon-free carbon source, directly serving as a substitute raw material that reduces CO2 emissions.

[0028] Siliceous biomass refers to plants (silicic acid plants) or their leaves and stems containing silica, including rice husks and straw from rice and wheat, bamboo leaves, and corn leaves and stems. Biochar from siliceous biomass is a carbon material obtained by dry distillation of siliceous biomass. There are no restrictions on the distillation method; rotary kiln distillation is an example. As mentioned above, biochar from siliceous biomass has a fixed carbon content of approximately 15-50%, an ash content of approximately 30-50%, and a calorific value of approximately 14-28 MJ / kg.

[0029] However, ensuring proper ventilation and liquid flow around the fusion zone is one of the most critical management considerations in blast furnace operation. Therefore, adjustments are typically made by increasing or decreasing the amount of by-products mixed with iron ore or other raw materials to bring the basicity (CaO / SiO2) of the molten metal in the blast furnace within a specified range. Even for unburned carbonaceous agglomerates, it is preferable to control the basicity (CaO / SiO2) of the molten metal at, for example... Figure 1 The specified range is shown. However, the basicity of the molten metal in the blast furnace can also be adjusted by using by-products from other blast furnaces, so sometimes it is not necessary to adjust the non-calcined carbonaceous briquettes separately.

[0030] The gangue components commonly used in unburned carbonaceous agglomerates are CaO, SiO2, Al2O3, and MgO. These components are also found in iron-bearing raw materials, carbon-bearing raw materials, and binders.

[0031] In typical unburned carbonaceous agglomerates, hydraulic binders such as CaO-based cement are used to achieve sufficient cold compressive strength for agglomerates. In this embodiment, commonly used micro-powders primarily composed of blast furnace slag, aging binders composed of alkali stimulants, quicklime, Portland cement, bentonite, etc., can also be used as such binders. The amount of binder added can be appropriately determined considering other formulation conditions. If the amount of binder added is too small, it is difficult to maintain sufficient cold compressive strength of the unburned carbonaceous agglomerates. On the other hand, if the amount of binder added is too large, the amount of slag in the unburned carbonaceous agglomerates increases, and the aeration in the lower part of the furnace becomes unstable. As a result, a stable reduction in the reducing material ratio cannot be obtained.

[0032] As described above, the binder composition of the unburned carbonaceous agglomerate increases the basicity (CaO / SiO2) of the molten unburned carbonaceous agglomerate, which may worsen the aeration and liquid flow around the fusion zone of the blast furnace. While both iron- and carbonaceous feedstocks contain gangue components, the basicity (CaO / SiO2) is high primarily due to the binder composition. Therefore, in this embodiment, the unburned carbonaceous agglomerate is combined with silica-containing ores, such as silica, as a gangue raw material to reduce this basicity. Silica is a typical silica-containing ore, but it is not limited to this.

[0033] In this embodiment, without altering the gangue composition charged into the blast furnace, a portion or all of the silica-containing ore is replaced with silica from biochar derived from siliceous biomass and used as gangue raw material. Therefore, even if biochar from siliceous biomass is used for unburned carbonaceous agglomerate ore, it will not adversely affect the aeration and liquid flow properties of the fusion zone at the bottom of the furnace.

[0034] Here, the content of gangue components such as SiO2 varies greatly depending on the brand of the original ore, such as the ore from which dust is generated or the ore blended in the sinter. Therefore, it is preferable to adjust the CaO / SiO2 value by selecting the ore brand used in the ironmaking plant. In particular, the CaO / SiO2 value is significantly affected by the amount of ore with high SiO2 content blended in the plant.

[0035] In the method for manufacturing unburned carbonaceous agglomerates according to this embodiment, a preferred embodiment for effectively utilizing biochar from siliceous biomass will be described. First, considering that the fixed carbon content and ash content per unit of biochar from siliceous biomass can vary, the fixed carbon content and ash content per unit of the incoming biochar from siliceous biomass are confirmed. Next, if the confirmed fixed carbon content can be fully utilized as the carbonaceous raw material in the blending raw material of the unburned carbonaceous agglomerates, full replacement is directly performed; if insufficient, partial replacement is performed, and the blending ratio of the raw materials is determined. As a result, the silica component in the biochar incidentally serves as part or all of the silica-containing ore in the gangue raw material of the unburned carbonaceous agglomerates. Here, depending on the amount of silica in the biochar from siliceous biomass, it can sometimes affect the variation in the basicity of the molten metal in the blast furnace. It is preferable to adjust the basicity separately using the unburned carbonaceous agglomerates, but it can also be adjusted using byproducts from other blast furnaces, so it is not necessary.

[0036] (Example of composition calculation for agglomerated minerals containing biochar derived from siliceous biomass) Here, we explain the trial calculation results when the carbonaceous raw material of ordinary unburned carbonaceous agglomerates is replaced by fixed carbon in biochar from siliceous biomass in equal amounts.

[0037] To simplify the calculation, the raw materials consist of only three types: biochar (A ton), iron ore powder (B ton), and binder (C ton). Their total is directly equivalent to the unburned carbonaceous agglomerate ore (D ton).

[0038] A+B+C=D (1) The typical reduction reaction of iron ore is shown in the following equation.

[0039] Fe2O3+3 / 2C→2Fe+3 / 2CO2 (2) According to the reaction formula (2), theoretically, 3 / 2 moles of carbon are needed for 1 mole of iron ore. However, considering the reaction yield, etc., 3 moles of carbon are needed for 1 mole of iron ore. In addition, the atomic weight of carbon is set to 12 and the molecular weight of iron ore (Fe2O3) is set to 160, which is the premise of the trial calculation.

[0040] Biochar derived from siliceous biomass is rice husk char produced by dry distillation at 500°C, and its specific composition is as follows.

[0041] • Fixed carbon: 28.0% by mass • Volatile components: 34.5% by mass • Ash content: 37.5% by mass (of which SiO2: 33.6% by mass) Based on the consideration of Equation (2) and the carbon composition of 3 moles relative to 1 mole of iron ore, the amount of fixed carbon in biochar, etc., the quantitative relationship between the amount of biochar A (ton) and the amount of iron ore powder B (ton) is expressed by Equation (3).

[0042] {A×28[%]÷12[g / mol]}×3=B÷160[g / mol] B = 11.2A (3) The amount of binder is usually about 3 to 10% by mass of the total carbon material and iron ore powder, but here it is set to 10% by mass, and equation (3) is also considered as shown in equation (4) below.

[0043] C=(A+B)×0.1=(1+11.2)×0.1×A C=1.22A(4) As a result, the production amount D (ton) of unburned carbonaceous agglomerate is expressed by equations (1), (3), and (4), and the amount of biochar A (ton) is expressed by equation (5).

[0044] D=A+B+C=A+11.2A+1.22A≈13.4A (5) The ratio s (mass%) of silica (SiO2) in the unburned carbonaceous agglomerate is expressed by the following formula (6), with reference to the amount of silica (SiO2) in the biochar.

[0045] s=A×33.6[%]÷D=A×33.6[%]÷13.4A s=2.5[%] (6) In addition, the ratio f (mass%) of iron ore (Fe2O3) in the unburned carbonaceous agglomerate is expressed by the following formula (7).

[0046] f=B÷D=11.2A÷13.4A=83.6[%] (7) (A trial calculation example of adjusting blast furnace feedstock by effectively utilizing agglomerated ore containing biochar from siliceous biomass) Next, the results of calculating the amount of silica in the by-products that were replaced in equal amounts and the amount of sinter that could be reduced were explained by using the above-mentioned unburned carbonaceous agglomerate containing silicon oxide and iron ore as raw material to charge the blast furnace.

[0047] Here, when sintered ore c1 (ton) is charged into the blast furnace, a trial calculation is performed for the case where silica (SiO2 is set to 100%) b (ton) is charged into the blast furnace as a by-product, and agglomerated ore a (ton) containing biochar from siliceous biomass is used instead. It should be noted that the biochar contained in the agglomerated ore here is the same as the rice husk char used in the above trial calculation.

[0048] When silica b (ton) before replacement is replaced by an equal amount of silica in agglomerated ore a (ton), referring to the above formula (6), the following formula (8) holds. That is, according to formula (8), by loading agglomerated ore a (ton) with 40 times the weight of silica b (ton) of the auxiliary raw material into the blast furnace, the silica of the auxiliary raw material can be replaced in an equal amount.

[0049] b = a × 2.5 [%] Therefore, a = 40b (8) Furthermore, if the iron ore content in the agglomerates that are replaced here can be directly reduced from the amount of sinter charged, then referring to formula (7), the following formula (9) holds. That is, according to formula (9), it can be seen that 0.836 times the weight of sinter (33.4 times the weight of silica b (ton) of the by-product raw material) can be reduced from the amount of agglomerates a (ton) replaced by silica.

[0050] c1-c2=0.836a=0.836×40b=33.44b (9) Explanation of reference numerals in the attached figures 1: Blast Furnace 2: Furnace top 3: Air supply vent 4: Fusion zone 5: Combustion Zone (Swirl Zone) 6: Furnace Heart 7: Taphole

Claims

1. A method for manufacturing unburned carbonaceous agglomerate ore, comprising forming a compound containing iron-bearing raw material, carbon-bearing raw material, gangue raw material and binder into agglomerates and curing them for a specified period, wherein, The fixed carbon and silicon dioxide in the biochar obtained by dry distillation of siliceous biomass are used as part or all of the carbon-containing raw material and part or all of the silicon-containing ore in the gangue raw material.

2. A method for utilizing siliceous biomass in a blast furnace, comprising: The fixed carbon and silicon dioxide in biochar obtained by dry distillation of siliceous biomass are used as part or all of the carbonaceous raw material and part or all of the silica-containing ore in the gangue raw material, which comprises iron-containing raw material, carbonaceous raw material, gangue raw material and binder. Unburned carbonaceous agglomerates, which are formed into briquettes using the aforementioned raw materials and cured for a specified period, are charged from the top of the blast furnace.

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