Method for manufacturing sintered ore

Abstract

To provide a method for manufacturing sintered ore which uses exhaust gas of a sintering machine as suction gas of the sintering machine, in which a production rate of the sintered ore is maintained and NOx emission is reduced.SOLUTION: A method for manufacturing sintered ore uses exhaust gas of a sintering machine as suction gas of the sintering machine. A charcoal material for sintering included in sintering raw material includes a biomass charcoal material. The concentration of oxygen contained in the suction gas is 16 vol.% or more and less than 21 vol.%. By mixing oxygen gas into the exhaust gas, the concentration of oxygen contained in the suction gas can be adjusted to 16 vol.% or more and less than 21 vol.%. Crushed compression molded product of a wood carbide can be used as the biomass charcoal material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing sintered ore by reusing exhaust gas from a sintering machine as suction gas during firing of raw materials for sintering. [Background technology]

[0002] There is a method for producing sintered ore by circulating the exhaust gas from a sintering machine as the suction gas for the sintering machine (for example, Patent Documents 1 and 2). In Patent Document 1, when the exhaust gas from the sintering machine is used as the suction gas for the sintering machine, the temperature and moisture content of the suction gas are adjusted to meet predetermined conditions. This increases the preheating rate of the raw materials and improves the productivity of sintered ore.

[0003] In addition, in Patent Document 2, when pseudo-particles are fired in an endless moving grate sintering machine, the exhaust gas discharged during sintering is circulated, thereby reducing the oxygen partial pressure in the system, suppressing combustion of the carbonaceous material while promoting sintering and reduction, and improving the productivity of highly reducible sintered ore. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 64-68430 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-226920 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, Patent Documents 1 and 2 focus on the productivity of sintered ore, but it is also important to reduce NOx emissions emitted during the production of sintered ore. An object of the present invention is to reduce NOx emissions while maintaining the productivity of sintered ore in a sintering ore production method that uses exhaust gas from a sintering machine as the suction gas for the sintering machine. [Means for solving the problem]

[0006] The present invention relates to a method for producing sintered ore by using exhaust gas from a sintering machine as suction gas for the sintering machine, in which the sintering carbonaceous material contained in the sintering raw materials includes biomass carbonaceous material, and the oxygen concentration contained in the suction gas is 16% by volume or more and less than 21% by volume.

[0007] The sintering machine may be a Dwight Lloyd type sintering machine, which moves pallets loaded with sintering materials along multiple wind boxes arranged in a predetermined direction. Here, exhaust gas discharged from the wind boxes located between the BRP (Burn Rising Point) and the ore discharge position can be used as suction gas.

[0008] By mixing oxygen gas into the exhaust gas, the oxygen concentration in the suction gas can be adjusted to 16% by volume or more and less than 21% by volume. As the biomass carbon material, crushed compressed wood carbonized material can be used. [Effects of the Invention]

[0009] According to the present invention, in a method for producing sintered ore in which exhaust gas from a sintering machine is used as suction gas for the sintering machine, NOx emissions can be reduced while maintaining the productivity of sintered ore. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an outline of a manufacturing process for sintered ore. [Figure 2] FIG. 2 is a diagram showing the configuration of a sintering machine. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Sintered ore manufacturing process) The outline of the sintered ore manufacturing process will be explained using Figure 1.

[0012] 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.

[0013] 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, 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 toward 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 passes through the molten zone A2 and becomes a sintered cake A3.

[0014] The exhaust gas discharged from the sintering machine 30 travels along the circulation path CR and is reused as the suction gas for the sintering machine 30. The suction gas can be either exhaust gas alone or a mixture of exhaust gas and oxygen-containing gas such as air. In this embodiment, the oxygen concentration contained in the suction gas is set to a predetermined concentration range (16% by volume or more and less than 21% by volume). If the oxygen concentration in the exhaust gas is within the predetermined concentration range, the exhaust gas alone can be used as the suction gas. On the other hand, if the oxygen concentration in the exhaust gas is lower than the lower limit (16% by volume) of the predetermined concentration range, the oxygen concentration can be adjusted to fall within the predetermined concentration range by mixing oxygen gas such as air into the exhaust gas.

[0015] (sintering machine) A specific structure (one example) of the sintering machine 30 will be described with reference to Fig. 2. Fig. 2 is a schematic diagram showing the structure of a DL (Dwight Lloyd) type sintering machine 30.

[0016] In the sintering machine 30, a plurality of pallets 32 are connected endlessly and hung between two gear wheels 33, 34, and the gear wheels 33, 34 rotate in the directions of arrows D1 and D2, respectively, causing the plurality of pallets 32 to move in the direction of arrow D3. A raw material supply hopper 35 that supplies sintering raw material to the pallets 32, and the above-mentioned ignition furnace 31 are provided at the top of the sintering machine 30.

[0017] Below the plurality of pallets 32 arranged on the upper side of the sintering machine 30, a plurality of air boxes 36 are arranged along the direction of movement of the pallets 32, and the air boxes 36 take in air from below the pallets 32 on which the sintering raw materials are loaded. Each air box 36 is connected to an air intake pipe 37, and the air taken in from the air box 36 is led to the air intake pipe 37. At least a part of the air intake pipe 37 constitutes the circulation path CR (see FIG. 1) described above.

[0018] After the upper part of the sintering raw material layer A1 is ignited by the ignition furnace 31, the pallet 32 ​​is transported in the longitudinal direction of the sintering machine 30 (from left to right in Figure 2), and the sintering reaction progresses from the top to the bottom of the sintering raw material layer A1 due to the intake air from multiple air boxes 36.

[0019] While the pallet 32 ​​moves along the upper path of the sintering machine 30, firing of the sintering raw material layer A1 loaded on the pallet 32 ​​is completed, and as the pallet 32 ​​moves along the gear wheel 34, the sintered ore is discharged from the pallet 32. Here, the position where the sintered ore is discharged from the pallet 32 ​​is referred to as the "ore discharge position." The pallet 32, which has been emptied of the sintered ore after being discharged, moves along the lower path of the sintering machine 30 and returns to the position of the raw material supply hopper 35. Sintered ore can be continuously produced in accordance with the movement of the pallet 32 ​​described above.

[0020] The sintering raw material layer A1 in the pallet 32 ​​is ignited by the ignition furnace 31, and while the pallet 32 ​​moves a given distance, the temperature of the exhaust gas is maintained at a temperature of around 100°C, after which the temperature of the exhaust gas rises rapidly and reaches the maximum temperature. Here, the position immediately after the temperature of the exhaust gas starts to rise rapidly is called BRP (Burn Rising Point).

[0021] The exhaust gas discharged from the wind box 36 located between the BRP generation position and the ore discharge position generally has an oxygen concentration of about 18% by volume, which is within the above-mentioned predetermined concentration range (16% by volume or more and less than 21% by volume), so this exhaust gas can be reused as suction gas. By assigning numbers (hereinafter referred to as "wind box numbers") to multiple wind boxes 36, it is possible to classify the wind boxes 36 that discharge exhaust gas to be reused from wind boxes 36 that discharge exhaust gas that is not reused. Then, the above-mentioned circulation path CR can be connected to the wind box 36 that discharges exhaust gas to be reused.

[0022] As a method of allocating wind box numbers, for example, "1" can be allocated to the wind box located at a position where the sinter raw material is fed from the raw material feeding hopper 35 to the pallet 32 ​​and then ignited in the sinter raw material layer A1 by the ignition furnace 31 (hereinafter referred to as "ignition position"). Then, wind box numbers "2", "3" and so on can be allocated in the order from the ignition position toward the discharge position.

[0023] (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, quicklime, peridotite, and serpentine. In addition to the iron ore, auxiliary materials, and sintering carbonaceous material, the sintering raw materials can also include return ore.

[0024] In this embodiment, biomass carbonaceous material is used as at least a part of the carbonaceous material for sintering. Biomass carbonaceous material is a carbonized organic material derived from living organisms (excluding fossil resources), and when used as a carbonaceous material for sintering, it is possible to use one with a volatile content adjusted to 20 mass% or less. Examples of biomass carbonaceous material include PKS charcoal obtained by carbonizing coconut shell kernels and wood charcoal obtained by carbonizing wood. The volatile content can be measured in accordance with the provisions of JIS M8812:2006.

[0025] As the carbonaceous material for sintering, biomass carbonaceous material alone can be used, or other carbonaceous materials (e.g., coke breeze or anthracite) can be used in combination with biomass carbonaceous material. The biomass carbonaceous material may be in any form, such as wood charcoal itself, wood charcoal that has been compressed and then crushed to a particle size suitable for producing sintered ore, or a mixture of the crushed wood charcoal and a binder that has been extruded. Compression molding can prevent excessive combustion of the carbonaceous material for sintering (biomass carbonaceous material), thereby improving the production rate of sintered ore.

[0026] The use of biomass carbonaceous material can improve the sintered ore production rate and reduce NOx emissions compared to coke breeze. When the exhaust gas from the sintering machine 30 is reused as the suction gas, firing is carried out in a low-oxygen atmosphere. However, since biomass carbonaceous material has a higher combustion rate than coke breeze, it can improve the sintered ore production rate even in a low-oxygen atmosphere. Furthermore, since the nitrogen content of biomass carbonaceous material is lower than that of coke breeze, it can reduce NOx emissions.

[0027] The mixing ratio of the biomass carbonaceous material to other sintering carbonaceous materials is not particularly limited. The effect of reducing NOx emissions can be achieved by including the biomass carbonaceous material of this embodiment as part of the sintering carbonaceous material. Here, the biomass carbonaceous material content is preferably less than 50% when the total sintering carbonaceous material is taken as 100% by mass. This is because a biomass carbonaceous material content of 50% by mass or more may result in a decrease in the yield of the sintering process. Even a small amount of biomass carbonaceous material (a biomass carbonaceous material content greater than 0% by mass) can contribute to a reduction in NOx emissions. This is because biomass carbonaceous material has a lower nitrogen content than coal-based sintering carbonaceous materials. On the other hand, the biomass carbonaceous material content is preferably 10% by mass or more when the total sintering carbonaceous material is taken as 100% by mass. A biomass carbonaceous material content of 10% by mass or more can further enhance the effect of reducing NOx emissions.

[0028] 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.

[0029] (Method of manufacturing wood carbonized material) The method for producing wood carbonized material will be described. The method for producing wood carbonized material includes at least a dry distillation step, and may also include a sieving step as needed.

[0030] In the carbonization process, wood is carbonized to produce wood charcoal. Wood chips crushed to an appropriate size for easy carbonization can be used. Examples of equipment that can be used to carbonize wood include an external combustion rotary kiln, an internal combustion rotary kiln, a fluidized bed reactor, and a moving bed reactor (shaft furnace).

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] (Crushed compressed wood charcoal) The carbonaceous material for sintering may be crushed wood charcoal produced as described above. This crushed material can be obtained by compressing and molding the wood charcoal into a compression molded product, and then crushing the compression molded product. Using crushed compression molded products can improve the productivity of sintered ore while reducing NOx emissions compared to using wood charcoal as is. In the compression molded wood charcoal, the compression process can reduce the pores present in the wood charcoal, thereby suppressing excessive combustion of the wood charcoal. Furthermore, suppressing excessive combustion can prevent a decrease in the productivity of sintered ore. The aggregate of wood charcoal before producing the compression molded product may contain multiple pieces of wood charcoal, and may be, for example, a simple collection of crushed wood charcoal pieces or crushed wood charcoal pieces bound together with a binder.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] (Method of manufacturing crushed material of compression molded material) 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.

[0041] 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.

[0042] 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.

[0043] Next, in the compression step, the aggregate of wood carbonized material produced in the dry distillation step is compressed to produce a compression molded product. When a binder is used, a kneading step is carried out before the compression step.

[0044] 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.

[0045] The compression molded product may be molded into any shape, for example, pellets (cylindrical) or tablets (pillow-shaped).

[0046] As described above, it is preferable to produce a compression-molded product by mixing a binder with the wood carbonized material in the compression process. By mixing a binder, excessive crushing of the compression-molded product in the subsequent crushing process can be prevented, and the particle size of the crushed product can be easily adjusted. The type of binder is as described above.

[0047] Water may be added together with the binder, and additives such as alkalis and acids may also be added. After kneading the wood carbonized material with the binder and water, the kneaded mixture can be supplied to a compression molding machine to produce a compression molded product.

[0048] The wood charcoal 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 charcoal during kneading may be used.

[0049] 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.

[0050] The size of the crushed material is not particularly limited, but can be, for example, less than 10 mm in particle size (under a 10 mm sieve). The average particle size of the crushed material is preferably 5 mm or less. If the average particle size exceeds 5 mm, the crushed material tends to be concentrated in the lower layer of the sintering raw material layer in the pallet, which may cause malfunctions in the sintering machine. The average particle size of the crushed material is preferably 1 mm or more. If the average particle size of the crushed material is less than 1 mm, it may cause a decrease in the air permeability of the sintering raw material layer, resulting in a decrease in the sinter ore production rate. The particle size of the crushed material can be measured by drying the crushed material at 105°C for 2 hours or more, shaking it for 5 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. The arithmetic mean particle size is defined as Σ(Vi × di) / Σ(Vi). Here, Vi is the abundance ratio of particles having a particle diameter di, and the particle diameter di is represented by the median particle size between the sieve openings of each sieve.

[0051] Next, in the optional sizing step, 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 carbon material for sintering. The predetermined particle size range can be, for example, 0.25 mm to 3.00 mm. This crushed material can be selected using sieves with openings of 0.25 mm and 3.00 mm. [Example]

[0052] Examples of the present invention will be described below, but the present invention is not limited to the examples described below.

[0053] (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 pot had a diameter of 300 mm and a height of 500 mm. The combustion gas suction pressure during the firing process was set to 1200 mmAq (11.8 kPa).

[0054] The raw materials used in the sintering test are shown in Table 1 below.

[0055] [Table 1]

[0056] As the iron ore, iron ores of brands A to D were prepared. The blending ratios [mass %] of these iron ores were as shown in Table 1 above, and the particle size of the iron ores (brands A to D) was 10 mm or less. As the auxiliary raw materials, peridotite, quicklime, and limestone were prepared. The blending ratios [mass %] of these auxiliary raw materials were as shown in Table 1 above, and the particle size of the peridotite and limestone was 5 mm or less, and the particle size of the quicklime was 1 mm or less.

[0057] On the other hand, sintering carbonaceous material was blended with the iron ore and auxiliary raw materials. The blending ratio of the sintering carbonaceous material was adjusted so that the amount of coke fines and fixed carbon was equal to 4.5 mass% relative to the total mass of the iron ore and auxiliary raw materials. Coke fines and biomass carbonaceous material were prepared as the sintering carbonaceous material, and the particle size of the sintering carbonaceous material was set to 5 mm or less.

[0058] The biomass charcoal materials used were PKS charcoal and crushed compressed wood charcoal. PKS charcoal was produced by pyrolysis of coconut kernels. To produce the crushed compressed wood charcoal, cedar wood was first crushed to a size of 30 mm or less, and then the crushed material was dry-distilled (pyrolyzed) to produce wood charcoal. Water and a binder were added to the crushed material, and the mixture was extrusion-molded to produce the compressed charcoal. The crushed compressed charcoal was then crushed to produce the crushed compressed charcoal (particle size of 5 mm or less).

[0059] The sintering raw materials were placed in a drum mixer (diameter 600 mm, rotation speed 25 rpm) and mixed for 4 minutes. Next, water was added to the drum mixer to achieve a target moisture content of 7.2 mass% (excl. mass), and the mixture in the drum mixer was mixed (granulated) for 4 minutes.

[0060] The above-mentioned sintering raw materials were charged into a pot and ignited, and then sintering was carried out for 1 minute at the above-mentioned (constant) suction pressure. Next, to simulate the use of exhaust gas from the sintering machine as the suction gas, simulated exhaust gas with adjusted oxygen concentration, moisture content, and temperature was supplied from above the pot for a period of 2 to 16 minutes, and suction using air was carried out from the 16th minute onwards. Here, the oxygen concentration was set to 21.0 vol%, 18.5 vol%, 16.0 vol%, and 13.0 vol%, respectively. The moisture content was set to 5%, and the temperature was set to 160°C.

[0061] The productivity of the sintered ore obtained by the above-mentioned sintering test was evaluated. The productivity is defined as the productivity of sintered ore [t / d / m 2 The productivity P is calculated by dropping the sinter cake obtained after sintering from a height of 2 m four times, sieving it through a sieve with a mesh size of 5 mm, and multiplying the mass of sinter Ms [t] on the sieve by the effective area S [m 2 ] and sintering time ts [min], and is calculated based on the following formula (1).

[0062]

number

[0063] Table 2 below shows the types of carbonaceous materials for sintering and the oxygen concentrations in the suction gas in Examples 1 to 4 and Comparative Examples 1 to 6. Table 3 below shows the productivity of sintered ore and the amount of NOx emissions in Examples 1 to 4 and Comparative Examples 1 to 6.

[0064] [Table 2]

[0065] [Table 3]

[0066] In Examples 1 and 3 and Comparative Example 2, the oxygen concentration in the suction gas was 18.5% by volume, but by using biomass carbonaceous material (PKS carbonaceous material or crushed compressed wood charcoal) as part of the carbonaceous material for sintering as in Examples 1 and 3, the productivity was improved and NOx emissions were reduced compared to Comparative Example 2. Furthermore, when Examples 1 and 3 are compared, Example 3, which used crushed compressed wood charcoal, showed a higher productivity and lower NOx emissions.

[0067] In Examples 2 and 4 and Comparative Example 3, the oxygen concentration in the suction gas was 16.0% by volume, but by using biomass carbonaceous material (PKS carbonaceous material or crushed compressed wood charcoal) as part of the carbonaceous material for sintering as in Examples 2 and 4, the productivity was improved and NOx emissions were reduced compared to Comparative Example 3. Furthermore, when Examples 2 and 4 were compared, Example 4, which used crushed compressed wood charcoal, showed a higher productivity and lower NOx emissions.

[0068] In Comparative Examples 4 and 5, the oxygen concentration in the suction gas was 13.0% by volume, and by using biomass carbonaceous material (PKS carbonaceous material) as part of the carbonaceous material for sintering as in Comparative Example 5, the productivity was improved and NOx emissions were reduced compared to Comparative Example 4. However, when comparing Comparative Example 5 with Examples 1 and 2, which have the same composition of the carbonaceous material for sintering, Comparative Example 5 showed a reduced NOx emissions compared to Examples 1 and 2, but the productivity was significantly lower than Examples 1 and 2. For this reason, it is preferable that the oxygen concentration in the suction gas be 16.0% by volume or more.

[0069] In Comparative Examples 1 and 6, the oxygen concentration in the suction gas was 21.0% by volume, and by using biomass carbonaceous material (PKS carbonaceous material) as part of the carbonaceous material for sintering as in Comparative Example 6, the productivity was improved and NOx emissions were reduced compared to Comparative Example 1. However, when comparing Comparative Example 6 with Examples 1 and 2, which have the same composition of the carbonaceous material for sintering, Comparative Example 6 had the same productivity but significantly increased NOx emissions compared to Examples 1 and 2. For this reason, it is preferable that the oxygen concentration in the suction gas is less than 21.0% by volume.

[0070] When the exhaust gas from the sintering machine is not used as the suction gas for the sintering machine, but air is used as the suction gas, the oxygen concentration in the air is generally 21.0% by volume. In addition, coke breeze is generally used as the carbonaceous material for sintering. Taking this into consideration, the productivity (30.2 t / d / m) in Comparative Example 1 2 ]) and NOx emissions (163 [ppm]) are the standards (hereinafter referred to as "evaluation standards") for evaluating production rate and NOx emissions.

[0071] In Examples 1 to 4, it was possible to reduce NOx emissions while maintaining the production rate relative to the evaluation standard. On the other hand, in Comparative Example 5, it was possible to reduce NOx emissions relative to the evaluation standard, but it was not possible to maintain the production rate. In addition, in Comparative Example 6, it was possible to maintain the production rate relative to the evaluation standard, but it was recognized that the effect of reducing NOx emissions was insufficient.

[0072] As described above, in the method for producing sintered ore using the exhaust gas of a sintering machine as the suction gas of the sintering machine, by using biomass carbonaceous material as at least a part of the carbonaceous material for sintering and setting the oxygen concentration contained in the suction gas to 16% by volume or more and less than 21% by volume, it is possible to reduce NOx emissions while suppressing a decrease in productivity. [Explanation of symbols]

[0073] 10: Hopper, 20: Granulator, 30: Sintering machine, 31: Ignition furnace, 32: Pallet, 33, 34: gear wheels, 35: raw material feeding hopper, 36: wind box, 37: intake pipe, CP1, CP2: conveying path, CR: circulation path, A1: sintering material layer, A2: melting zone, A3: Sintered cake

Claims

1. A method for producing sintered ore by using exhaust gas from a sintering machine as a suction gas for the sintering machine, The sintering carbonaceous material contained in the sintering raw materials includes biomass carbonaceous material, A method for producing sintered ore, characterized in that the oxygen concentration contained in the suction gas is 16% by volume or more and less than 21% by volume.

2. The sintering machine moves a pallet loaded with sintering raw materials along a plurality of wind boxes arranged in a predetermined direction, 2. The method for producing sintered ore according to claim 1, wherein exhaust gas discharged from the wind box located between the position where a BRP (Burn Rising Point) occurs and the ore discharge position is used as the suction gas.

3. 2. The method for producing sintered ore according to claim 1, wherein the oxygen concentration contained in the suction gas is adjusted to 16% by volume or more and less than 21% by volume by mixing oxygen gas with the exhaust gas.

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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