Method for producing sintered ore

Abstract

To improve the production rate of sintered ore when the sintered ore is produced using a carbonaceous material for sintering containing biomass carbon.SOLUTION: In a method for producing sintered ore by firing a sintering raw material containing a carbonaceous material for sintering, the carbonaceous material comprises coke breeze and / or anthracite together with not more than 50 mass% of a biomass carbonaceous material. The carbonaceous material for sintering is added by 5 mass% or more of a standard blend amount thereof, for increased heat during firing. A biomass carbonaceous material may have an average particle size of 1.45 mm or more, and may be obtained by crushing a compressed molded product of a wood carbonized material.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing sintered ore using a carbonaceous material for sintering that contains a biomass carbonaceous material. [Background technology]

[0002] In Patent Document 1, oil palm kernel shell charcoal (PKS charcoal) is blended with a sintering raw material that is a blend of fine iron ores, fluxes for adjusting composition, and return ore in order to reduce carbon dioxide emissions and improve the productivity of the sintering machine. Here, oil palm kernel shell charcoal is a solid carbide produced by heat-treating oil palm kernel shell. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-237876 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to improve the productivity of sintered ore by a means different from that of Patent Document 1 in a method for producing sintered ore using a carbonaceous material for sintering containing a biomass carbonaceous material. [Means for solving the problem]

[0005] The present invention provides a method for producing sintered ore by firing raw materials containing carbonaceous material for sintering. The carbonaceous material for sintering contains coke fines and / or anthracite and 50% by mass or less of biomass carbonaceous material. To compensate for the heat increase during firing, the carbonaceous material for sintering is added in an amount of 5% by mass or more of the standard blend amount of the carbonaceous material for sintering.

[0006] The average particle size of the biomass carbonaceous material can be 1.45 mm or more. The average particle size of the biomass carbonaceous material can be 2.5 mm or more. As the biomass carbonaceous material, crushed compressed wood carbonized material can be used. [Effects of the Invention]

[0007] According to the present invention, when sintered ore is produced using a carbonaceous material for sintering containing a biomass carbonaceous material, the productivity of sintered ore can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an outline of a method for producing sintered ore. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Sintered ore manufacturing method) The outline of the sintered ore manufacturing method will be explained with reference to FIG.

[0010] A plurality of raw materials (iron ore, auxiliary raw materials, sintering carbonaceous material, etc.) that make up the sintering raw material are respectively charged into the plurality of hoppers 10. The sintering raw materials discharged from each hopper 10 move along a conveying path CP1 and are then fed into a granulator 20. The granulator 20 granulates the sintering raw materials while mixing them, and discharges the sintering raw materials as granules. The sintering raw materials discharged from the granulator 20 move along a conveying path CP2 and are charged into a sintering machine 30.

[0011] In the sintering machine 30, a sintering raw material layer A1 is formed by charging the sintering raw material layer A1. The upper surface of the sintering raw material layer A1 is ignited by the ignition furnace 31, thereby forming a molten zone A2 on the upper surface of the sintering raw material layer A1. Here, gas is drawn from the upper surface of the sintering raw material layer A1 to the lower surface, causing the molten zone A2 to expand towards the lower surface of the sintering raw material layer A1, and sintering of the sintering raw material layer A1 progresses. As a result, the sintering raw material layer A1 becomes a sintered cake A3 via the molten zone A2. The sintered cake is crushed and sized to obtain sintered ore.

[0012] (sintering raw materials) The sintering raw materials include iron ore, auxiliary materials, and sintering carbonaceous material. As the iron ore, one type of iron ore can be used, or multiple types of iron ore can be used. Examples of auxiliary materials include limestone, olivine, quicklime, and dolomite. In addition to the iron ore, auxiliary materials, and sintering carbonaceous material, the sintering raw materials can also include return ore.

[0013] (carbon material for sintering) As the carbonaceous material for sintering, at least one of coke breeze and anthracite, and a biomass carbonaceous material (described later) are used. Because the biomass carbonaceous material has a higher combustion rate than the coke breeze, the use of the biomass carbonaceous material as part of the carbonaceous material for sintering can improve the sintering rate.

[0014] The mixing ratio of biomass carbonaceous material in the carbonaceous material for sintering is greater than 0% by mass and not more than 50% by mass. By setting the mixing ratio of biomass carbonaceous material to not more than 50% by mass, it becomes easier to improve the productivity of sintered ore. Here, the mixing ratio of biomass carbonaceous material is preferably not more than 30% by mass, and more preferably not more than 20% by mass.

[0015] (heat gain) In this embodiment, the amount of sintering carbonaceous material is increased for the purpose of increasing the heat in the sintering process. Specifically, when the amount of sintering carbonaceous material used as a sintering raw material (hereinafter referred to as the "standard amount") is taken as 100 mass%, the amount of sintering carbonaceous material used as the heat increase is set to 5 mass% or more. As a result, the amount of sintering carbonaceous material used in the sintering process is 105 mass% or more of the standard amount.

[0016] The standard blending amount is the blending amount of the sintering carbonaceous material adjusted so that the amount of coke fines and fixed carbon in a predetermined blending ratio is equal to that when only coke fines are used as the sintering carbonaceous material. Based on this, the standard blending amount can be determined for the sintering carbonaceous material containing at least one of coke fines and anthracite, and biomass carbonaceous material. Once the standard blending amount is determined, the blending amount (additional blending amount) of the sintering carbonaceous material used as the heat increase amount can be determined as described above.

[0017] Since the sintering carbonaceous material contained in the sintering raw material is a mixture of at least one of coke fines and anthracite and biomass carbonaceous material, the sintering carbonaceous material for the heat increase portion is also a mixture of at least one of coke fines and anthracite and biomass carbonaceous material, where the mixing ratio of the biomass carbonaceous material in the sintering carbonaceous material for the heat increase portion is the same as the mixing ratio of the biomass carbonaceous material in the sintering carbonaceous material contained in the sintering raw material.

[0018] (biomass carbon) Biomass carbonaceous materials are carbonized organic matter derived from living organisms (excluding fossil resources), and when used as carbonaceous materials for sintering, those with a volatile content adjusted to 20% by mass or less can be used. The volatile content can be measured in accordance with the provisions of JIS M8812:2006. An example of a biomass carbonaceous material is wood carbonized material obtained by carbonizing wood.

[0019] The biomass carbonaceous material may be in any form, including, for example, wood carbonized material itself, wood carbonized material that has been compression-molded and then crushed to a particle size suitable for producing sintered ore, or a mixture of the crushed material and a binder that has been extruded. Compression molding can prevent excessive combustion of the sintered carbonaceous material (biomass carbonaceous material), thereby improving the production rate of sintered ore.

[0020] The wood used in producing the above-mentioned wood charcoal can be, for example, woody biomass. Examples of woody biomass include sawmill waste, thinned wood, firewood, etc. The type of wood is not particularly limited, and various types of wood can be used, such as cedar.

[0021] The method for producing wood charcoal includes at least a carbonization step, and optionally a sizing step. In the carbonization step, wood is carbonized to produce wood charcoal. The wood can be in the form of chips that have been crushed to an appropriate size to facilitate carbonization. Examples of equipment that can be used for carbonizing wood include an external combustion rotary kiln, an internal combustion rotary kiln, a fluidized bed reactor, and a moving bed reactor (shaft furnace).

[0022] In the carbonization process, the volatile content of the wood carbonized material can be adjusted. Specifically, it is preferable to adjust the volatile content of the wood carbonized material in the carbonization process so that the volatile content is 20 mass% or less. In the sintering process, substances derived from the volatile content may leak from the sintering carbon material into the exhaust gas and adhere to the electrostatic precipitator as oil. However, by adjusting the volatile content of the wood carbonized material to 20 mass% or less, the adhesion of volatile content to the electrostatic precipitator can be suppressed.

[0023] The volatile content of coke fines used as carbonaceous material for sintering is often significantly lower than 10% by mass, but if the volatile content of wood charcoal is adjusted to 20% by mass or less, adhesion of volatile content to an electrostatic precipitator can be suppressed when coke fines and wood charcoal are used in combination as carbonaceous material for sintering. Here, the higher the mixing ratio of wood charcoal in the carbonaceous material for sintering, the more preferable it is to use wood charcoal with an appropriately reduced volatile content.

[0024] The conditions for the carbonization process, such as the carbonization temperature and time, can be set appropriately based on the target volatile content of the carbonaceous material to be sintered. For example, when cedar wood chips are carbonized at a temperature of 800°C for one hour, the volatile content of the resulting wood charcoal can be set to 4.8% by mass.

[0025] Next, in the sizing step, which is performed as needed, the particle size distribution of the carbonized wood is adjusted by, for example, sieving. Note that a crushing step of crushing the carbonized wood may be performed before the sizing step.

[0026] The carbonaceous material for sintering may be crushed wood charcoal produced as described above by compression molding (compression molded product). This crushed product can be obtained by compressing and molding wood charcoal to form a compression molded product, and then crushing this compression molded product. By using crushed compression molded products, the productivity of sintered ore can be improved compared to when wood charcoal is used as is.

[0027] In the case of compressed wood charcoal, the compression process can reduce the pores present in the wood char, thereby suppressing excessive combustion of the wood char. Furthermore, by suppressing excessive combustion, a decrease in the productivity of sintered ore can be suppressed. The aggregate of wood char before the compression molding is produced may contain multiple pieces of wood char, and may be, for example, a simple collection of crushed wood char or crushed wood char bound with a binder.

[0028] The compression-molded product is preferably produced by adding a binder to wood carbonized material and then compression-molding the material. By adding the binder, excessive crushing of the compression-molded product can be suppressed when crushing the compression-molded product to obtain crushed material. Furthermore, the binding force of the binder makes it easier to obtain crushed material having a desired particle size.

[0029] Examples of binders that can be used include cornstarch (starch), bentonite, coal tar, biomass tar, petroleum pitch, and cement. When using certain binders (such as cornstarch), additives such as alkalis and acids can be added to produce a strong compression-molded product. The amount of binder added is preferably a blend ratio (excluding figures) of 1% to 10% by mass, where the wood carbonized material is taken as 100% by mass. If the amount of binder added is 1% by mass or more, the strength of the compression-molded product increases and the handling of the compression-molded product improves as the blend ratio increases within the above blend ratio range. If the amount of binder added exceeds 10% by mass, the effect of improving the strength of the compression-molded product decreases, resulting in increased costs.

[0030] The crushed material of the compression molded product has an apparent density of 0.6 g / cm 3 It is preferable that the apparent density is 0.6 g / cm or more. 3 By achieving this, the productivity of sintered ore can be improved. Apparent density is a value (bulk density) measured by the bead volume displacement method using a density measurement device (Micromeritics / GeоPyc). The bead volume displacement method, adopted by Micromeritics, is a volume displacement method using DryFlo (pseudo-fluid), a highly fluid bead. Specifically, the volume of only the beads placed in the sample chamber is measured first, and then the measurement sample is placed on the bead layer in the sample chamber and the volume is measured. The difference between the two volumes calculates the volume of the measurement sample, including the pores and cavities. Apparent density is the mass of the measurement sample divided by the calculated volume of the measurement sample.

[0031] The apparent density and volatile matter content of the compression-molded wood carbonized material and the crushed material of this compression-molded material are the same before and after crushing.

[0032] Next, a method for producing crushed material of a compression-molded product will be described. The method for producing crushed material of a compression-molded product includes a dry distillation step, a compression step, and a crushing step, and may also include a sizing step as needed.

[0033] First, in the carbonization step, wood charcoal is produced from wood in the same manner as in the carbonization step described above. The size of the wood used in the carbonization step is not particularly limited, but wood that has been crushed to a size of 30 mm or less can be used, for example, to facilitate the compression step described below.

[0034] The volatile content of the wood charcoal can be adjusted to 20% by mass or less by proximate analysis, even in the case of crushed wood charcoal, as with the wood charcoal itself described above, but 15% by mass or less is more preferable. As described above, in the compression process, it is preferable to mix a binder with the wood charcoal to produce a compression-molded product. If the binder also contains volatile matter, the volatile content of the entire compression-molded product will also increase. The increase in volatile content due to the addition of a binder can be estimated at, for example, 5% by mass. Therefore, taking into account the increase in volatile content due to the addition of a binder, the volatile content of the wood charcoal can be reduced by 5% by mass to 15% or less, compared to when the wood charcoal is used directly as a carbonaceous material for sintering. Note that the higher the mixing ratio of the compression-molded product in the carbonaceous material for sintering, the more preferable it is to use a compression-molded product with an appropriately reduced volatile content.

[0035] Next, in the compression process, the aggregate of wood carbonized material produced in the dry distillation process is compressed to produce a compression molded product. If a binder is used, a kneading process is performed before the compression process. The compression molded product may be molded into any shape, such as a pellet (cylindrical) or a tablet (pillow shape).

[0036] The method for the compression step is not particularly limited, and any method can be used as long as it can apply pressure to the wood carbonized material to granulate it and produce a compression-molded product such as pellets. For example, compression molding can be performed using a roller-type (ring die type, flat die type) molding machine or a screw-type extrusion molding machine. Furthermore, compression molding can also be performed using a roll press method using a roll rotation compression molding machine or a tableting method using a biaxial compression molding machine.

[0037] As described above, in the compression process, it is preferable to mix a binder with the wood carbonized material to produce a compression-molded product. By mixing a binder, excessive crushing of the compression-molded product in the subsequent crushing process can be suppressed, and the particle size of the crushed product can be easily adjusted. The type of binder, etc., is as described above.

[0038] Water may be added together with the binder, or additives such as alkali or acid may be added. After kneading the wood carbonized material with the binder, water, etc., the kneaded material can be supplied to a compression molding machine to produce a compression-molded product. The wood carbonized material may be crushed (for example, crushed to an average particle size of 1 mm or less) before kneading and compression. Alternatively, a device (for example, an extruder) that can simultaneously crush the wood carbonized material during kneading may be used.

[0039] Next, in the crushing step, the compression-molded product produced in the compression step is crushed. The crushing method is not particularly limited, but for example, a rod mill, a hammer crusher, a roll crusher, a super sander, a jaw crusher, or a fret mill can be used.

[0040] Next, in the sizing step, which is performed as needed, crushed material having a particle size within a predetermined particle size range is selected to adjust the particle size distribution of the crushed material. The crushed material (wood carbonized material) obtained by adjusting the particle size distribution can be used as a carbon material for sintering.

[0041] The average particle size of the biomass carbonaceous material is not particularly limited, but is preferably less than 10 mm (under a 10 mm sieve). The average particle size of the biomass carbonaceous material can be 1.45 mm or more, and is preferably 2.50 mm or more. If the average particle size of the biomass carbonaceous material is less than 1.45 mm, this may cause a decrease in the air permeability within the sintering raw material layer, resulting in a decrease in the productivity of sintered ore.

[0042] The average particle size of biomass carbon can be measured by drying the biomass carbon for at least two hours at 105°C, shaking it for five minutes using a rotary shaker, and using a sieve in accordance with JIS Z8801-1:2019. The average particle size is the arithmetic mean particle size determined by sieving, and is defined as "Σ(wi × xi) / Σ(wi)". Here, particle size xi is the median particle size (representative value) between the sieve openings, and wi is the proportion of particles with particle size xi. [Example]

[0043] Examples of the present invention will be described below, but the present invention is not limited to the examples described below.

[0044] (Sintering test) The firing process was carried out using a small-scale experimental facility (hereinafter referred to as the "pot"), which was a sintering machine. The diameter of the pot was 300 mm, and the height of the pot was 600 mm. The ignition and re-ignition times were both 1 minute (heat amount 25 MJ / ton of raw material), and the combustion gas suction pressure during the firing process was 1200 mmAq (11.8 kPa).

[0045] The sintering raw materials used in the sintering test are shown in Table 1 below. As the iron ore, iron ores of brands A to F were prepared, and the blending ratios [mass%] of these iron ores are as shown in Table 1 below. As the auxiliary raw materials, limestone, olivine, quicklime, and dolomite were prepared, and the blending ratios [mass%] of these auxiliary raw materials are as shown in Table 1 below.

[0046] [Table 1]

[0047] The sintering carbonaceous material was blended with the iron ore and auxiliary raw materials. As the sintering carbonaceous material, only coke fines and a mixture of coke fines and biomass carbonaceous material at a predetermined blending ratio were prepared. The blending ratio of the sintering carbonaceous material consisting of only coke fines was 4.5 mass% (excluding figures) with respect to the total mass (100 mass%) of the iron ore and auxiliary raw materials. The blending ratio when coke fines and biomass carbonaceous material are mixed will be described later.

[0048] The analytical values ​​(proximate analysis values ​​and elemental analysis values) of the coke breeze and biomass carbonaceous materials are shown in Table 2 below. The proximate analysis values ​​(ash content, volatile matter, fixed carbon) can be measured in accordance with the provisions of JIS M8812:2006, and the elemental analysis values ​​(C, H, N, TS (total sulfur)) can be measured in accordance with the provisions of JIS M8813:2004.

[0049] [Table 2]

[0050] The biomass charcoal was prepared by crushing compressed wood charcoal. First, cedar wood was crushed to a size of 30 mm or less, and then the crushed material was dry-distilled (pyrolyzed) to produce wood charcoal, which was then crushed to 1.5 mm. Water and a binder were added to the crushed material, and the mixture was extrusion-molded to produce a compressed wood charcoal. This compressed material was then crushed to produce crushed compressed wood charcoal.

[0051] When a mixture of coke fines and biomass carbonaceous material was used as the carbonaceous material for sintering, the mixture ratio of the coke fines and biomass carbonaceous material was adjusted as shown in Table 3 below.

[0052] [Table 3]

[0053] When a mixture of coke fines and biomass carbonaceous materials was used as the sintering carbonaceous material, the blending ratio of the coke fines and biomass carbonaceous materials in the sintering raw material was adjusted so that the amount of fixed carbon was equal to the above-mentioned 4.5 mass% of coke fines. Specifically, the blending ratio of the coke fines and biomass carbonaceous materials was determined as shown in Table 4 below.

[0054] [Table 4]

[0055] As the biomass carbonaceous material, biomass carbonaceous material having the particle size distribution shown in the following Table 5 was prepared. The average particle size shown in the following Table 5 is the above-mentioned arithmetic average particle size (Σ(wi×xi) / Σ(wi)).

[0056] [Table 5]

[0057] The particle size distribution shown in Table 5 above was measured using sieves with mesh sizes of 5, 3, 1.0, 0.5, and 0.25 mm. The mass wi of the biomass carbonaceous material contained in each particle size range i is the mass of the biomass carbonaceous material that falls under the sieve with the upper mesh size of each particle size range i and is present on the sieve with the lower mesh size of each particle size range i. For example, biomass carbonaceous material with a particle size range of "3-1.0" mm is biomass carbonaceous material that falls under the sieve with 3 mm mesh and is present on the sieve with 1.0 mm mesh.

[0058] The above-mentioned coke fines and biomass carbonaceous materials were used to prepare the carbonaceous materials for sintering shown in Table 6. Table 6 shows the blending ratio of the coke fines and biomass carbonaceous materials that make up the carbonaceous materials for sintering, the blending amount of the carbonaceous materials for sintering as the heat increase (heat increase amount: mass %), and the average particle size of the biomass carbonaceous materials.

[0059] [Table 6]

[0060] The sintering raw materials (excluding the carbonaceous material for sintering) were placed in a drum mixer (diameter 600 mm, rotation speed 25 rpm) and mixed for 1 minute. Next, water was added to the drum mixer to achieve a target moisture content of 7.5 mass% (excluding all figures), and the mixture was mixed (granulated) for 3 minutes and 45 seconds. Next, the carbonaceous material for sintering was placed in the drum mixer and mixed (granulated) for 15 seconds. The sintering raw materials obtained in this manner were subjected to the sintering test described above.

[0061] The sintering rate and productivity of the sintered ore obtained in the sintering test were evaluated.

[0062] The sintering speed [mm / min] is the value obtained by dividing the thickness of the sintering raw material layer (the size in the height direction of the pot) when the sintering raw material is filled in the pot by the time from the time when ignition of the sintering raw material layer is started to the time when the combustion zone reaches the bottom of the sintering raw material layer (referred to as the arrival time). In this example, the arrival time was the time when the temperature of the exhaust gas reached the point where it shows the highest temperature (BTP; Burn Through Point).

[0063] The production rate is the production rate of sinter [t / d / m 2 The productivity P is calculated by dropping the sinter cake obtained after the sintering test from a height of 2 m four times, and then sieving it through a sieve with a mesh size of 5 mm. The mass of the sintered ore on the sieve, Ms [t], is multiplied by the effective area S [m 2 ] and sintering time ts [min], and is calculated based on the following formula (1).

[0064]

number

[0065] Table 7 below shows the sintering speed and productivity in the sintering test for the base, Examples 1 to 10, and Comparative Examples 1 to 5 shown in Table 6 above.

[0066] [Table 7]

[0067] In assessing the production rate, the base production rate (37.5 t / d / m 2 90% (33.8 [t / d / m 2 ]) was used as the evaluation criterion. Here, if 90% of the base productivity can be achieved, the remaining 10% of the productivity can be secured by other known technologies. For example, JP 2022-43500 A, JP 2018-178166 A, and JP 2022-33594 A disclose technologies for improving the productivity of sintered ore, and these technologies can be used in combination.

[0068] As shown in Comparative Examples 1 and 2, when the mixing ratio of biomass carbonaceous material in the sintering carbonaceous material was 30 or 50 mass%, the sintered ore production rate was lower than the evaluation standard without increasing the temperature using the sintering carbonaceous material. Also, as shown in Comparative Examples 3 to 5, when the mixing ratio of biomass carbonaceous material in the sintering carbonaceous material was 70 mass%, the sintered ore production rate was lower than the evaluation standard regardless of whether or not increasing the temperature using the sintering carbonaceous material (heat increase amount: 0, 5, 10 mass%).

[0069] On the other hand, as shown in Examples 1 to 10, when the mixing ratio of biomass carbonaceous material in the sintering carbonaceous material was 20, 30, and 50% by mass, the productivity of sintered ore was higher than the evaluation standard by setting the heat increase to 5 and 10% by mass. Also, as shown in Examples 4, 7 to 10, when the mixing ratio of biomass carbonaceous material was 30% by mass and the heat increase to 10% by mass, the productivity of sintered ore improved as the average particle size of the biomass carbonaceous material increased. [Explanation of symbols]

[0070] 10: Hopper, 20: Granulator, 30: Sintering machine, 31: Ignition furnace, A1: Sintering raw material layer, A2: molten zone, A3: sintered cake

Claims

1. A method for producing sintered ore by firing a sintering raw material containing a sintering carbonaceous material, comprising: The carbonaceous material for sintering contains coke breeze and / or anthracite and 50 mass% or less of biomass carbonaceous material, A method for producing sintered ore, characterized in that the carbonaceous material for sintering is added in an amount of 5 mass % or more of the standard blend amount of the carbonaceous material for sintering to compensate for the heat increase during firing.

2. 2. The method for producing sintered ore according to claim 1, wherein the biomass carbonaceous material has an average particle size of 1.45 mm or more.

3. 2. The method for producing sintered ore according to claim 1, wherein the biomass carbonaceous material has an average particle size of 2.5 mm or more.

4. 2. The method for producing sintered ore according to claim 1, wherein the biomass carbonaceous material is obtained by crushing a compressed wood carbonized material.

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