Method for producing sintered ore

Abstract

To provide a method for producing sintered ore that can lower the emission of NOx and further reduce an environmental load, while ensuring superior productivity.SOLUTION: A method for producing sintered ore is provided, in which a carbonized wood material is used as a portion of the carbonaceous material in the sintering raw material, and sintering is performed using a sintering machine having a stand support device that supports a sinter cake resulting from sintering the sintering raw material.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing sintered ore using wood charcoal. [Background technology]

[0002] In the sintering process, there is a demand to reduce the environmental load by reducing nitrogen oxides (NOx) in the exhaust gas. As a technology for reducing NOx in the sintering process, it has been proposed to use coal such as subbituminous coal or lignite, which meets certain conditions such as reaction start temperature and volatile content, as the carbonaceous material used as fuel (Patent Document 1). In addition, methods such as adding quicklime to the sintering raw material and replacing the coke fuel with low-N anthracite have also been proposed as NOx reduction technologies. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4681688 Summary of the Invention [Problem to be solved by the invention]

[0004] In response to the above-mentioned techniques, there is a demand for a method for producing sintered ore that reduces NOx emissions in the sintering process and further reduces the environmental load. The present invention aims to provide a method for producing sintered ore that reduces NOx emissions and further reduces the environmental load while also being highly productive. [Means for solving the problem]

[0005] The present invention has been made to solve the above problems, and the gist of the invention is as follows.

[0006] (1) Wood charcoal is used as part of the sintering raw material. A method for producing sintered ore, in which sintering is carried out using a sintering machine having a stand support device for supporting a sinter cake formed by sintering raw materials.

[0007] (2) The method for producing sintered ore described above in (1) is characterized in that the wood carbonization product is a pulverized product obtained by compressing an aggregate of wood carbonization product and pulverizing the compressed product, and the volatile content of the pulverized product is 20 mass% or less.

[0008] (3) The apparent density of the pulverized material is 0.6 g / cm 3 The method for producing sintered ore according to (2) above, characterized in that Effect of the Invention

[0009] According to the present invention, it is possible to provide a method for producing sintered ore that reduces NOx emissions and further reduces the environmental load while also achieving excellent productivity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The method for producing sintered ore of this embodiment will be described. In the method for producing sintered ore of this embodiment, wood carbide is used as part of the carbonaceous material for sintering, which is the fuel for the sintering process. In the sintering process, the sintered raw material containing the wood carbide is sintered by a sintering machine having a stand support device that supports a sinter cake formed by sintering the sintered raw material.

[0011] In this embodiment, a case will be described in which a sintering carbonaceous material is used that is a mixture of a "first sintering carbonaceous material" derived from wood carbonized material and a "second sintering carbonaceous material" not derived from wood carbonized material. The first sintering carbonaceous material is the wood carbonized material of this embodiment. The "wood carbonized material" of this embodiment includes wood carbonized material described below and pulverized compressed molded products of the wood carbonized material. The second sintering carbonaceous material is a carbonaceous material produced by heating coal in an oxygen-free or low-oxygen atmosphere, such as coke powder or anthracite.

[0012] The mixing ratio of the first sintering carbonaceous material and the second sintering carbonaceous material is not particularly limited, and as long as the carbonaceous material contains the wood charcoal of this embodiment (first sintering carbonaceous material), a NOx reduction effect can be obtained. Preferably, the content of wood charcoal is less than 50% when the entire carbonaceous material is taken as 100% by mass. If it is 50% or more, the yield of the sintering process may decrease. Note that even if a small amount of wood charcoal is mixed as a coagulation material (if the mixing ratio of wood charcoal is more than 0% by mass), the CO 2 It is preferable that the content of the wood charcoal is 10% or more when the total carbonaceous material is 100% by mass. If the blending ratio of the wood charcoal is 10% or more by mass, the sintering speed is further improved.

[0013] (wood carbide) First, the carbonaceous material (first sintering carbonaceous material) used in the sintering step of this embodiment will be described. The carbonaceous material of this embodiment is wood carbonized material as described above. The wood carbonized material is, for example, charcoal produced by dry distilling wood.

[0014] The wood charcoal of this embodiment is a carbonaceous material with a higher combustion rate at 700°C (combustion rate (700°C)) than anthracite. The combustion rate (700°C) [1 / sec] of anthracite is 0.00215 (1 / sec). Using this combustion rate of anthracite as a standard, the "wood charcoal" of this embodiment can be a carbonaceous material with a combustion rate (700°C) of 0.0022 (1 / sec) or higher. Furthermore, the wood charcoal of this embodiment can be one that has a lower combustion start temperature than coke or anthracite.

[0015] Here, the burning rate (700°C) is calculated by the thermobalance method as follows. First, 10 mg of the sample to be measured is placed on the thermobalance in the thermobalance measuring device, and after the inside of the device is thoroughly purged with nitrogen, the sample is heated at a temperature increase rate of 100°C / min with nitrogen flowing at 200 ml / min. After the sample temperature reaches 700°C, the flow gas is immediately switched from nitrogen to air at 200 ml / min, and the weight loss is measured, and the resulting reaction time t (the elapsed time since the flow gas was switched from nitrogen to air) and reaction rate X (X = [weight loss at each time - weight of unburned matter at the end of measurement] / [initial weight of sample - weight of unburned matter at the end of measurement]) are obtained. Then, the reaction rate dX / dt at each reaction rate is calculated, and the average value from X = 0 to 0.5 is calculated, and the average value is taken as the burning rate at 700°C.

[0016] The wood used in the production of wood charcoal can be, for example, woody biomass. Woody biomass can be, for example, sawmill waste, thinned wood, firewood, etc. The type of wood is not particularly limited, and various types of wood can be used. For example, cedar can be used.

[0017] (Method of manufacturing wood charcoal) The method for producing carbonized wood will now be described. The method for producing carbonized wood includes at least a carbonization step, and may also include a granulation step, if necessary.

[0018] First, in the carbonization process, wood is carbonized to produce wood charcoal. Wood may be in the form of chips pulverized to an appropriate size for easy carbonization. For example, an external combustion rotary kiln, an internal combustion rotary kiln, a fluidized bed reactor, or a moving bed reactor (shaft furnace) can be used as a device for carbonizing wood.

[0019] The volatile content of the wood carbonized material is adjusted in the carbonization process. Specifically, it is preferable to control the volatile content of the wood carbonized material in the carbonization process so that the volatile content of the entire carbon material (the first carbon material for sintering and the second carbon material for sintering) is 10 mass% or less. This is because, in the sintering process, substances derived from the volatile content may flow out of the carbon material into the exhaust gas and adhere to the electric dust collector as oil. By adjusting the volatile content of the carbon material to an appropriate range, it is possible to suppress the adhesion of volatile content to the dust collector.

[0020] The volatile content of the wood charcoal depends on the mixing ratio with the second sintering carbonaceous material, but is preferably 20 mass% or less in industrial analysis (JIS M8812:2006). The volatile content of the second sintering carbonaceous material, such as coke powder, is often much lower than the above-mentioned 10 mass%, so if the volatile content of the wood charcoal is 20 mass% or less, the volatile content of the carbonaceous material as a whole can be made the above-mentioned specified value (for example, 10 mass%) or less. When the mixing ratio of wood charcoal is high, it is sufficient to use wood charcoal with an appropriately reduced volatile content.

[0021] The conditions for the carbonization process may be appropriately set based on the target volatile content, such as the carbonization temperature and the carbonization time. For example, when cedar wood chips are carbonized at a carbonization temperature of 800°C for one hour, the volatile content of the obtained wood carbonized material can be 4.8% by mass.

[0022] Next, a sizing process is carried out as necessary. In the sizing process, the particle size distribution of the wood charcoal is adjusted, for example, by sieving. Note that a crushing process for crushing the wood charcoal may be carried out before the sizing process. The above is the method for producing wood charcoal of this embodiment.

[0023] (Crushed compressed product) Next, another embodiment of the wood charcoal (first sintering carbonaceous material) will be described. As another embodiment of the carbonaceous material, crushed material of the compression molded material of the above-mentioned wood charcoal may be used. This crushed material is obtained by compressing and molding the wood charcoal to form a compression molded material, which is then crushed. By using the crushed material of the compression molded material, NOx emissions can be reduced in the same manner, while the productivity of sintered ore can be improved more than when the above-mentioned wood charcoal is used as is. In the compression molded material obtained by compressing an aggregate of wood charcoal, the pores present in the wood charcoal can be reduced by the compression process, so that excessive combustibility can be suppressed. And, by suppressing excessive combustibility, it is possible to suppress a decrease in the product yield and productivity of the sintered ore. Note that the aggregate of wood charcoal may be any material that contains a plurality of wood charcoal, and may be, for example, crushed wood charcoal or wood charcoal bonded with a binder.

[0024] The compression molded product is preferably one obtained by adding a binder to the above-mentioned wood carbonized material and compressing it. By including the binder, when the compression molded product is crushed to obtain a crushed product, the compression molded product can be prevented from being crushed excessively. In addition, the binding force of the binder makes it easier to obtain a crushed product having a desired particle size.

[0025] Examples of binders that can be used include cornstarch (starch), bentonite, coal tar, biomass tar, petroleum pitch, and cement. Some binders (such as cornstarch) can also contain additives such as alkalis and acids to produce strong molded products. The amount of binder added is preferably 1% by mass or more and 10% by mass or less (excluding numbers) when the wood carbonized material is taken as 100% by mass. Adding 1% by mass or more of binder within the above range is preferable because the strength of the compression molded product increases and handling becomes easier. If the amount exceeds 10%, the effect of improving the strength slows down and the cost increases.

[0026] The crushed product of the compression molding 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 doing so, the product yield and productivity in the production of sintered ore will be higher. The apparent density is a value (bulk density) measured by the bead volume displacement method using a density measuring device (Micromeritics / GeоPyc). The bead volume displacement method is a measurement method adopted by Micromeritics, and is a volume displacement method using DryFlо (pseudo fluid), which is a highly fluid bead, as the measurement sample. Specifically, the volume of only the beads placed in the sample chamber is measured first, and then the sample is placed in the bead layer in the sample chamber and the volume is measured. The volume of the measurement sample, including the pores and cavities, is calculated from the difference between the two volumes. The apparent density is the value obtained by dividing the mass of the measurement sample by the calculated volume.

[0027] The apparent density and the volatile matter content, which will be described later, of the compression molded wood carbonized material and its pulverized material do not change before and after pulverization and are the same.

[0028] (Method of manufacturing pulverized material of compression molded material) The manufacturing method of the pulverized product of the compression molded product will be described. The manufacturing method of the pulverized product of the compression molded product includes a dry distillation step, a compression step, a pulverization step, and a granulation step.

[0029] First, a carbonization process is carried out. Wood charcoal is produced from wood in the same manner as described above. The size of the wood to be carbonized is not particularly limited, but wood may be crushed to a size of 30 mm or less to facilitate the compression molding process described below.

[0030] The volatile content of the pulverized wood may be dry-distilled to 20% by mass or less in terms of industrial analysis, as in the case of the wood carbonized material as is, but is more preferably 15% by mass or less. As described above, in the compression step, it is preferable to mix a binder with the wood carbonized material to form a compression molded product. If the binder also contains volatile content, 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 to be, for example, 5% by mass. Therefore, taking this increase into consideration, it is preferable to set the volatile content of the wood carbonized material to 15% by mass or less, which is lower than when the above-mentioned wood carbonized material is used as a carbon material as is. As described above, when the mixing ratio of the compression molded product with the second sintering carbon material is increased, the compression molded product with the volatile content appropriately reduced may be used.

[0031] Next, a compression step is carried out. 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.

[0032] The compression and molding method is not particularly limited, and may be any method that can granulate the wood carbonized material by applying pressure to 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. In addition, a roll press method using a roll rotation type compression molding machine or a tableting method using a biaxial compression molding machine may also be used.

[0033] The compression molded product may be molded into any shape, for example, a pellet (cylindrical) or a tablet (pillow shape).

[0034] In addition, as described above, it is preferable to manufacture the compression molded product by mixing a binder with the wood carbonized material in the compression process. By mixing the binder, the compression molded product can be prevented from being excessively crushed in the subsequent crushing process, and the particle size of the crushed product can be easily controlled. The type of binder is as described above.

[0035] Water may be added together with the binder. Additives such as alkali and acid may also be added. After the wood carbonized material is kneaded with the binder and water, the kneaded material is fed to a compression molding machine to produce a compression molded product.

[0036] The wood carbonized material may be crushed (for example, to an average particle size of 1 mm or less) before kneading and compression. Also, a device capable of simultaneously crushing wood during kneading (for example, an extruder) may be used.

[0037] Next, a pulverization step is performed. In the pulverization step, the compression molded product produced in the compression step is pulverized. The pulverization 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 may be used for pulverization.

[0038] The size of the pulverized material is not particularly limited, but may be, for example, less than 10 mm in particle size (sieve size of 10 mm). The average particle size of the pulverized material is preferably 5 mm or less. If the average particle size exceeds 5 mm, the pulverized material is likely to be unevenly distributed in the lower layer of the raw material layer on the pallet, and may be burned onto the grate bar, causing equipment malfunction. The average particle size of the pulverized material is preferably 1 mm or more. If the pulverized material is too fine, less than 1 mm, it may cause a decrease in ventilation in the raw material layer, resulting in a decrease in productivity. The particle size of the pulverized material can be measured by drying the pulverized material at 105°C for 2 hours or more, shaking it for 5 minutes using a rotary tap shaker, and using a sieve conforming to JIS Z8801-1:2019. The average particle size is the arithmetic mean particle size obtained by sieving using the sieve. The arithmetic mean particle diameter means the arithmetic mean particle diameter defined as Σ(Vi×di) / Σ(Vi) (where Vi is the abundance ratio of particles with a particle diameter di, and the particle diameter di is represented by the median particle size between the meshes of each sieve).

[0039] Next, a sizing process is performed as necessary. In the sizing process, pulverized material having a particle size within a predetermined particle size range is selected to adjust the particle size distribution of the pulverized material. The pulverized material obtained by adjusting the particle size distribution can be used as the wood charcoal material for the first sintering. The predetermined particle size range can be, for example, 0.25 mm to 3.00 mm. This selection of the pulverized material can be performed using sieves with openings of 0.25 mm and 3.00 mm.

[0040] The crushed material larger than the upper limit of the predetermined particle size range selected in the sizing process can be returned to the smashing process and crushed together with the compressed molded material for reuse. The crushed material smaller than the lower limit of the predetermined particle size range can be returned to the compression process and mixed with the binder for reuse. If the sizing process is omitted, the crushed material obtained in the smashing process can be used as it is as the first sintering carbonaceous material of this embodiment.

[0041] (Sintered Ore Manufacturing Method) Next, a method for producing sintered ore using the above-mentioned wood charcoal (pulverized wood charcoal or its compressed product) will be described. In this embodiment, the above-mentioned carbonaceous material is used as part of the carbonaceous material used in the sintering process. In addition, in the sintering process of this embodiment, sintering is performed by a stand-supported sintering method.

[0042] The sintering machine used in the sintering process of this embodiment is a downward suction type Dwight Lloyd sintering machine. A plurality of connected sintering pallets move on an endless track to continuously produce sintered ore. The sintering machine of this embodiment has a stand, which is a support member that supports a sinter cake, on the pallet. As a sintering machine having a stand, a known sintering machine can be used (for example, see JP-A-4-168234). The stand is arranged at least in one or more places in the width direction of each pallet with an appropriate interval. The stand is, for example, a trapezoidal plate-shaped support member arranged upright on the pallet, and the trapezoidal surface is arranged parallel to the moving direction of the pallet. The shape, dimensions, etc. of the stand may be set appropriately.

[0043] The manufacturing method of sintered ore of the present embodiment using the above-mentioned stand-type sintering machine will be described. First, the above-mentioned wood carbide (wood carbide or crushed compressed product thereof) as the first sintering carbonaceous material, coke powder as the second sintering carbonaceous material, iron ore and auxiliary materials are mixed in a mixer and granulated to manufacture sintered raw materials.

[0044] As the iron ore, one type of iron ore may be used, or a mixture of multiple types of iron ores may be used. As the auxiliary raw materials, for example, limestone, quicklime, and peridotite (MgO source) may be used. The raw materials for sintered ore may include return ore in addition to iron ore, auxiliary raw materials, and sintering carbonaceous material.

[0045] The granulated sintering raw material is then loaded from the hopper into the sintering machine using a drum feeder, and a raw material packed bed is continuously formed on the moving pallet. The raw material is packed so that the raw material packed bed is higher than the height of the stand. The upper part of the formed raw material packed bed is ignited, and the raw material packed bed is burned to produce a sinter cake. At this time, the sinter cake is supported by the stands of each pallet, so that the ventilation of the lower part of the raw material packed bed is maintained, and sintered ore can be produced without a decrease in production efficiency.

[0046] The sintered sinter cake is cooled by suction from below. When the pallet reaches the ore discharge position and moves from the top to the bottom on the caterpillar track, the sinter cake breaks and falls with the rotation of the pallet, and is discharged as sintered ore from the sinter machine. This is the manufacturing method of sintered ore.

[0047] According to the method for producing sintered ore of this embodiment, wood charcoal or crushed compressed wood charcoal is used as the carbonaceous material, so that NOx emissions can be reduced compared to the case where only other carbonaceous materials such as coke powder are used. Furthermore, the use of the wood charcoal improves the oxygen utilization efficiency, so that the amount of oxygen-containing gas such as air supplied during sintering can be reduced. Therefore, the amount of exhaust gas during the sintering process can be reduced. Therefore, according to the method for producing sintered ore of this embodiment, the environmental load can be further reduced.

[0048] Furthermore, according to the method of this embodiment, the sintering raw material containing the wood charcoal of this embodiment as a carbonaceous material is sintered using a stand-supported sintering method, so that productivity can be improved more effectively than when a normal carbonaceous material such as coke powder is used. Specifically, the inventors' research has revealed that when the wood charcoal of this embodiment or a crushed product of its compression molding is used as a carbonaceous material, the sintering raw material is more easily densified than when other carbonaceous materials such as coke powder are used. That is, although the wood charcoal of this embodiment is very excellent in terms of reducing NOx, it is densified during sintering compared to coke powder, and hot air permeability is more likely to decrease, and productivity is more likely to decrease.

[0049] In contrast, by using the wood charcoal of this embodiment and sintering it by the stand support sintering method, it is possible to greatly improve the decrease in air permeability caused by the tendency of the wood charcoal to be easily sintered. In other words, when the wood charcoal of this embodiment is used as the carbon material and sintering is performed by the stand support sintering method, productivity can be improved more than when only a normal carbon material such as coke powder is used by the stand support sintering method. Therefore, according to the manufacturing method of sintered ore of this embodiment, it is possible to manufacture sintered ore with higher productivity while reducing NOx emissions, etc.

[0050] Furthermore, when pulverized compressed wood charcoal is used as the wood charcoal, it is possible to produce sintered ore with further increased productivity while similarly reducing NOx emissions. EXAMPLES

[0051] The embodiment will be further described with reference to examples. Two types of carbonaceous materials were prepared: wood charcoal and crushed compressed wood charcoal. These carbonaceous materials were used to produce sintered ore by the above-mentioned sintered ore production method using a sintering pot tester equipped with a stand. The productivity (production rate), air permeability, oxygen utilization efficiency, and NOx concentration of exhaust gas in the sintering process were measured and calculated to evaluate the productivity and reduction of environmental load. For comparison, a sintering process using only coke powder as the carbonaceous material and a sintering process using a sintering pot tester without a stand were also tested.

[0052] (wood carbide) Wood crushed to a size of 30 mm or less was dry-distilled in a rotary kiln to produce wood charcoal with a volatile content of 15% by proximate analysis. The wood charcoal samples were obtained by sieving to obtain the particle size distribution shown in Table 1 below.

[0053] [Table 1]

[0054] The apparent density of this wood charcoal is 0.3 g / cm 3 The apparent density was measured by the bead volume displacement method using a density measuring device (Micromeritics / GeоPyc). The wood carbonized sample was placed in a layer of DryFlо (pseudo fluid), and the volume (apparent volume) of the sample, including the pores and cavities, was measured. The apparent density was then calculated from the apparent volume and the mass of the sample.

[0055] The combustion rate (700°C) of the wood charcoal was 0.00421 (1 / sec). The combustion rate (700°C) was measured by the thermobalance method using the thermobalance measuring device described in the above embodiment.

[0056] (Crushed compressed wood charcoal) The wood charcoal produced by the above method was finely pulverized to a size of 5 mm or less, and cornstarch (addition amount: 8 mass%) and water were added as a binder, mixed, and compression molded to produce a cylindrical compression molded product with a diameter of 8 mm (length 10 to 30 mm). The compression molded product produced was pulverized using a jaw crusher (compression type crusher) to adjust the particle size to a specified size. Then, in the same way as the wood charcoal, the product was sieved to adjust the particle size distribution in Table 1 above, and a sample of the pulverized compression molded product was obtained. The apparent density of this pulverized product was 0.7 g / cm 3 The combustion rate (700°C) of the pulverized material, measured in the same manner as above, was 0.0035 (1 / sec).

[0057] (Coke breeze) Coke breeze was used as the carbonaceous material to be mixed with the base and comparative carbonaceous materials and the wood charcoal. The coke breeze was also sized by sieving to have the particle size distribution shown in Table 1. The apparent density of the sized coke breeze was 1.3 g / cm. 3 The combustion rate of the coke powder (700℃) was 0.00112 (1 / sec).

[0058] (Preparation of sintering materials) As the sintering raw materials, raw materials in which iron ore, auxiliary raw materials, return ore, and carbonaceous materials were mixed were prepared for each type of carbonaceous material.

[0059] As the iron ore, a mixture of iron ores of brands A to F was used. In addition, limestone, quicklime, and an MgO source (peridotite) were used as auxiliary materials. The blending amounts [mass%] of the iron ore, auxiliary materials, and return ore are shown in Table 2 below. The return ore was blended at 15 mass% (excluding numbers) when the total of the iron ore and auxiliary materials was 100 mass%.

[0060] [Table 2]

[0061] The amount of carbonaceous material in each test example was adjusted so that the amount of fixed carbon (proximate analysis value) was equal to 4.5% by mass of coke fines, based on the case where the total amount of iron ore and auxiliary materials was 100% by mass (base test example), and 4.5% by mass of coke fines was used as the standard. Specifically, the carbonaceous material in each test example was prepared by replacing a part of the 100% coke fines with the above-mentioned wood charcoal or its compressed powder. The blending ratio of coke fines and wood charcoal in each test example is as shown in Table 3 below. For the test examples using carbonaceous material containing wood charcoal, the amount of carbonaceous material (excluding the amount) was added so that the amount of fixed carbon input was equal to that of the base test example in which only coke fines was added at 4.5% by mass, and sintering was performed.

[0062] The sintering raw materials were prepared as follows. First, iron ore, auxiliary raw materials, return ore and carbonaceous material were charged into a drum mixer (diameter 1 m, rotation speed 23 rpm) and mixed for 1 minute. Next, a specified amount of water was added to the charged raw materials into the drum mixer. For test examples in which the carbonaceous material was only coke powder, 7.2 mass% (excluding figures) of water was added to the raw materials. For test examples containing wood charcoal, an additional amount of water was added, the amount of water being increased according to the centrifugal moisture equivalent of the wood charcoal. The mixture in the drum mixer was then mixed for an additional 4 minutes and granulated to obtain the sintering raw materials.

[0063] (Sintering test) Using a sintering pot testing machine, a miniaturized version of a sintering machine, sintering tests were conducted on sintering raw materials containing each blend of carbonaceous materials, and the production rate, permeability index, oxygen utilization efficiency, and NOx concentration in the exhaust gas were evaluated for each.

[0064] The sintering pots used were 300mm in diameter, with a pot equipped with a stand and a pot without a stand for comparison. The pot with a stand had a single stand 300mm high placed at the bottom of the pot. Sintering tests were carried out in these sintering pots, with each sintering raw material being filled to a layer thickness of 600mm. The sintering test was carried out with a combustion gas suction pressure of 14kPa. The above sintering tests were carried out to evaluate the productivity, permeability index, oxygen utilization efficiency, and NOx concentration of exhaust gas.

[0065] (Production rate) Production rate is 1 m2 of firing area. 2 It represents the mass of sinter production [t] per day (d). Production rate P [t / d / m 2 ] can be calculated by the following formula (1). P = Ms / (S × ts) × 60 × 24 (1)

[0066] In this test, Ms [t] is the mass of the sintered ore on the sieve obtained by dropping the sinter cake obtained after sintering from a height of 2 m four times and then sieving it through a sieve with a mesh size of 5 mm. S [m 2 ] is the effective area of ​​the sintering pot in a plan view, and ts [min] is the sintering time. The sintering time was determined by measuring the temperature of the exhaust gas discharged from the bottom of the sintering pot and counting the time from ignition to the point at which this temperature reached its peak.

[0067] (Breathability Index) The permeability index (JPU) is a value calculated by the following formula (2) using the flow rate of gas (air) and the suction negative pressure during the sintering test, and a higher value indicates better permeability. The permeability index indicates the ratio of the permeability index of the other test examples (permeability index of test example / permeability index of base) when the permeability index of the base test example shown in Table 3 below is set to 1.

[0068] Breathability index JPU=F / A×(h / s) 0.6 (2) where F is the gas flow rate [Nm 3 / min], A is the effective area of ​​the sintering pot [m 2 ], h is the thickness of the raw material layer [m], s is the negative suction pressure [mH 2 O].

[0069] (oxygen utilization efficiency) The oxygen utilization efficiency is the ratio of the amount of oxygen consumed in the sintering process to the amount of oxygen supplied. Specifically, it is a value calculated from the oxygen concentrations in the supply gas and the exhaust gas according to the following formula (3). Oxygen utilization efficiency [%] = [(oxygen concentration in supply gas (vol%)) - (oxygen concentration in exhaust gas (vol%))] / (oxygen concentration in supply gas (vol%)) × 100 (3) In this test, air was supplied, so the oxygen concentration of the supply gas was 20.9 vol%. If the oxygen utilization efficiency is higher, the amount of oxygen-containing gas supplied in the sintering process can be reduced, and the amount of exhaust gas in the sintering process can be reduced, thereby further reducing the environmental load.

[0070] (NOx concentration) The NOx concentration was measured by using a chemiluminescence concentration measuring device to measure the NOx concentration contained in the exhaust gas during the sintering test.

[0071] Table 3 shows the test conditions and test results for each test example of the sintering pot test.

[0072] [Table 3]

[0073] The test results showed that Example 1, which used wood charcoal as the carbon material and had a stand, had a higher oxygen utilization efficiency than the base, which used only coke powder, and also had a lower NOx concentration.

[0074] On the other hand, in the case of Comparative Example 1 using 100% coke breeze and a stand, although the productivity improved, the oxygen utilization efficiency did not improve and the NOx concentration also increased.

[0075] In Comparative Example 2, in which wood charcoal was used and sintered without a stand, the particle size distribution and fixed carbon content of the carbonaceous material were the same, but the air permeability was lower than that of the base, and the productivity was also lower than that of the base. In contrast, in Example 1 with a stand, the air permeability was improved and the productivity was also improved. The improvement in productivity from Comparative Example 2 to Example 1 (39.8-34.1=5.7) was greater than the improvement in productivity (41.6-37.8=3.8) when 100% coke powder was used and the stand was changed from no stand (base) to stand (Comparative Example 1). Therefore, it was confirmed that by combining wood charcoal with stand sintering, the productivity can be improved more effectively while reducing the environmental load, such as reducing NOx.

[0076] Moreover, in Example 2, in which the wood carbonized material in Example 1 was replaced with crushed compressed molded material as the carbon material, the productivity was further improved compared to Example 1. The oxygen utilization efficiency and NOx concentration were also equivalent to or improved compared to Example 1, and it was confirmed that they were greatly improved compared to the base and Comparative Example 1.

Claims

1. Wood charcoal is used as part of the sintering raw material. A method for producing sintered ore, in which sintering is carried out using a sintering machine having a stand support device for supporting a sinter cake formed by sintering raw materials.

2. 2. The method for producing sintered ore according to claim 1, wherein the wood carbonized material is a pulverized product obtained by compressing an aggregate of wood carbonized material and pulverizing the compressed material, and the volatile content of the pulverized product is 20 mass% or less.

3. The apparent density of the pulverized material is 0.6 g / cm ３ The method for producing sintered ore according to claim 2,

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