Method for producing sintered ore

Abstract

Comprising the following steps: a step for forming a lower-stage raw material filling layer (10) by charging a lower-stage mixed raw material granulated material into a sintering machine (100); a step for forming an upper-stage raw material filling layer (20) by loading an upper-stage compound raw material granulated material onto the lower-stage raw material filling layer; and a step in which the surface of the lower-stage raw material filling layer and the surface of the upper-stage raw material filling layer are ignited, and an oxygen-containing gas is introduced into the lower-stage raw material filling layer and the upper-stage raw material filling layer by lower suction (6) at atmospheric pressure. At least a part of the gas sucked from the lower side of the surface side of the upper-stage raw material filling layer after the ignition of the upper-stage raw material filling layer is set as an oxygen-rich gas having an oxygen concentration of 26-46 vol%, and the oxygen concentration of the oxygen-rich gas is greater than or equal to 26 vol% and less than or equal to 46 vol% in the machine length direction of the sintering machine. When an intermediate position (Z) is defined as an intermediate position in a section from the rear (X) of the outlet of the upper-stage ignition furnace (2C) to the ore discharge end (Y), and a section from the rear (X) of the outlet of the upper-stage ignition furnace to the intermediate position (Z) is defined as a first half section, the region to which the oxygen-rich gas is supplied is a region including a part of the first half section.

Description

Technical Field

[0001] This invention relates to a method for manufacturing sintered ore for use as raw material in blast furnaces, and particularly to a two-stage charging and two-stage ignition sintering method. Background Technology

[0002] Sinter, the main raw material for blast furnace ironmaking, is typically manufactured as follows: First, iron raw materials such as iron ore (powder), iron-containing impurities such as scale / ironmaking dust, CaO-containing by-products such as limestone, return ore, and carbon materials (binding materials) that become fuel for sintering (binding) the sinter through combustion heat are mixed (blended) in a prescribed proportion. The blended raw materials (blended raw materials) undergo granulation treatment (hereinafter referred to as granulation) to adjust their particle size distribution, forming simulated particles from the primary particle aggregates of the raw materials. Next, the granulated blended raw materials (blended raw material granules) are loaded onto the trolley (sintering trolley) of a suction belt sintering machine (DL: Dwight-Lloyd) through a hopper, forming a filling layer of blended raw materials (hereinafter referred to as the raw material filling layer or raw material layer). From the top (surface) of the formed raw material filling layer, the carbon materials in the raw material filling layer are ignited using an igniter. Then, while the trolley is continuously moved, air is drawn from below the trolley. By supplying oxygen from the air into the raw material filling layer through the drawing, the combustion of the carbon material in the raw material filling layer proceeds from top to bottom, and the heat of combustion of the carbon material sinters the raw material filling layer sequentially. The sintered part (sintered block) obtained by sintering is granulated to a specified particle size through crushing, screening, etc., and becomes sintered ore, which is used as raw material for the blast furnace.

[0003] In this method of manufacturing sintered ore based on a DL-type sintering machine, Patent Document 1 proposes a multi-stage loading and multi-stage ignition sintering method in which the raw material filling layer is formed and ignited in two or more stages. In the two-stage loading and two-stage ignition sintering method (hereinafter also referred to as the two-stage loading and two-stage ignition method), which is an example of the multi-stage loading and multi-stage ignition sintering method, the raw material granules are loaded into the sintering machine in two separate loading stages along the layer height direction to form two raw material filling layers (upper raw material filling layer and lower raw material filling layer), and the surface of each raw material filling layer is ignited, and air is drawn from below, thereby allowing the sintering reaction of each layer to proceed simultaneously and in parallel.

[0004] In the two-stage loading and two-stage ignition sintering method, the raw material filling layer is divided into two stages, and sintering is carried out simultaneously in both stages, thus roughly doubling the production capacity. Furthermore, the exhaust gas used for sintering the upper raw material filling layer (hereinafter referred to as the upper layer) is drawn from below and reused for sintering the lower raw material filling layer (hereinafter referred to as the lower layer), thus reducing (halving) the exhaust gas volume. On the other hand, the gas (exhaust gas) used for sintering the upper layer, resulting in a lower oxygen partial pressure, is used for sintering the lower layer, leading to sintering under low oxygen partial pressure. Therefore, the combustion of the charcoal in the lower layer becomes incomplete, and insufficient heat is required for sintering, hindering the sintering reaction and resulting in a decrease in the strength of the sintered ore in the lower layer.

[0005] In response, an oxygen-enriched method for pumping gas was proposed.

[0006] Patent Document 2 discloses the following technique: measuring the oxygen concentration in the main exhaust gas drawn from the sintering machine as a whole, and adjusting the oxygen concentration in the gas drawn from below the surface of the raw material layer (hereinafter referred to as the drawn gas) to make the oxygen concentration 6% or more. In the embodiments, the oxygen concentration range of 21% to 25% of the drawn gas was verified, confirming the strength improvement effect brought about by oxygen enrichment.

[0007] Furthermore, Patent Document 3 discloses a method for supplying oxygen-containing gas using differential pressure in a two-stage loading and two-stage ignition sintering process. Therefore, it is described that the oxygen concentration of the supplied oxygen-containing gas is preferably 12-40%.

[0008] Furthermore, Patent Document 4 discloses the following technique: In a loading layer (raw material filling layer) formed by a single loading stage, in addition to igniting its upper surface using an ignition furnace, a burner is also used to ignite the middle section of the upstream end of the loading layer from the side, thereby achieving a two-stage ignition sintering method. Additionally, it proposes to eliminate insufficient combustion in the lower layer by enriching the oxygen in the suction gas downstream of the ignition furnace. In the embodiments, the oxygen concentration range of 21% to 46% in the suction gas was verified, confirming the increased productivity and improved strength resulting from oxygen enrichment.

[0009] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 47-26304 Patent Document 2: Japanese Patent Publication No. 6-43618 Patent Document 3: Japanese Patent Application Publication No. 2000-17343 Patent Document 4: Japanese Patent Application Publication No. 2015-157980 Summary of the Invention

[0010] The problem that the invention aims to solve However, in the verification of the two-stage loading and two-stage ignition method in Patent Document 2, no study was conducted on areas where the oxygen concentration of the extracted gas exceeded 25%. Furthermore, in the technology of Patent Document 3, oxygen-containing gas is supplied via differential pressure, and there is no inspiration for a two-stage loading and two-stage ignition method that does not use differential pressure for extraction.

[0011] Furthermore, Patent Document 4 only discloses the verification results of applying the two-stage ignition technology to the one-stage loading method, which forms a one-stage loading layer by loading raw materials in one step, and does not disclose the verification results of the two-stage loading and two-stage ignition method. When the raw material granules are filled into the sintering machine trolley, they are loaded via a loading chute, accompanied by particle size segregation. Smaller granules are more concentrated on the upper side of the raw material layer, while larger granules are more concentrated on the lower side. As a result, for example, charcoal composed of fine particles also has a fine particle size after granulation and is largely distributed on the upper side of the raw material layer. Compared to the lower layer in the two-stage loading method, where each loading layer is formed in two separate stages, the lower layer in the one-stage loading method has a coarser particle size and a lower charcoal concentration. It is generally known that due to such differences in particle size segregation and charcoal distribution along the layer thickness (layer height), the firing conditions such as the layer temperature and ventilation during sintering change, which affects the yield and productivity.

[0012] Furthermore, in the technology of Patent Document 4, the lower layer is ignited by bringing the flame into contact with the middle section of the upstream end of the loading layer from the side. Since the loading layer on the trolley moves towards the discharge end side together with the trolley, the ignition time is inevitably shorter compared to the ignition produced by the ignition furnace in the two-stage loading and two-stage ignition method. In addition, the granulated raw material supplied from the hopper enters between the lower layer and the flame during ignition. Therefore, the heat input to the lower layer is reduced in actual operation, and the sintering reaction may not be able to proceed sufficiently. Moreover, since the flame is blown towards the inclined surface that serves as the upstream end of the loading layer, it is believed that it will also affect particle size segregation, etc. From the above, it can be seen that, based on the insights of Patent Document 4, the inventors believe that the effect of oxygen enrichment of the extracted gas in the two-stage loading and two-stage ignition method is inconceivable.

[0013] In view of the above-mentioned problems, the inventors attempted to study the impact on productivity when the oxygen concentration of the gas supplied to the lower and upper layers at atmospheric pressure by suction from below is set to a high oxygen concentration region of more than 25% in the two-stage loading and two-stage ignition method.

[0014] The purpose of this invention is to provide a method for manufacturing sintered ore that can improve productivity in a two-stage loading and two-stage ignition process.

[0015] Methods for solving problems [1] A method for manufacturing sintered ore, comprising the following steps: The process of forming a lower stage raw material filling layer by loading granulated raw materials of the lower stage system into the sintering machine; The process of forming the upper raw material filling layer by loading granulated raw materials from the upper system onto the aforementioned lower raw material filling layer; and The process involves igniting the surfaces of the lower raw material filling layer and the upper raw material filling layer, respectively, and introducing oxygen-containing gas into the lower and upper raw material filling layers under atmospheric pressure through suction from below. Specifically, after the ignition of the aforementioned upper raw material filling layer, at least a portion of the gas drawn from below from the surface side of the aforementioned upper raw material filling layer is set as an oxygen-enriched gas with an oxygen concentration of 26% by volume or more and 46% by volume or less. In the longitudinal direction of the sintering machine, the middle position is defined as the interval from the outlet of the upper ignition furnace to the end of the ore discharge, and the first half interval is defined as the interval from the outlet of the upper ignition furnace to the middle position. The area for supplying the oxygen-enriched gas is the area that includes a part of the first half interval.

[0016] [2] According to the method for manufacturing sintered ore described in [1], a portion of the aforementioned first half interval is the upstream side portion of the aforementioned first half interval.

[0017] [3] According to the sinter manufacturing method described in [1], when the interval from the middle position to the discharge end in the length direction of the sintering machine is defined as the second half interval, The region supplying the oxygen-enriched gas includes at least a portion corresponding to the first half of the interval, and the portion corresponding to the first half of the interval is longer than the portion corresponding to the second half of the interval.

[0018] [4] According to the method for manufacturing sintered ore described in [1], the region for supplying the oxygen-enriched gas is the first half of the region or a part of the first half of the region.

[0019] [5] In the method for manufacturing sinter according to any one of [1] to [4], a highly combustible carbon material with a combustion rate of 0.0022 (1 / sec) or more at 700°C is used as the raw material for the lower section filling layer.

[0020] [6] According to the method for manufacturing sintered ore described in [5], the high combustible char material comprises carbonized material (also known as coking material) obtained by dry distillation of coal with a Roga index of less than 10.

[0021] [7] According to the method for manufacturing sintered ore described in [5], wherein the above-mentioned highly combustible charcoal material comprises palm kernel shell charcoal.

[0022] According to the present invention, in the two-stage loading and two-stage ignition method, after the upper stage ignition is completed, at least a portion of the gas drawn from the surface side of the upper stage layer is set as oxygen-enriched gas with an oxygen concentration of 26% by volume (vol%) or more and 46% by volume (vol%) or less, and the area for supplying the oxygen-enriched gas is set as a region including a portion of the first half of the interval from the outlet of the upper stage ignition furnace to the end of the ore discharge, thereby improving productivity. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating a sinter manufacturing process using a two-stage loading and two-stage ignition sintering method according to one embodiment of the present invention.

[0024] Figure 2 This is a graph showing the relationship between the oxygen concentration of oxygen-enriched gas and the yield of finished products.

[0025] Figure 3 It is a graph showing the relationship between oxygen concentration in oxygen-enriched gas and productivity. Detailed Implementation

[0026] The following is for reference Figure 1 The two-stage loading and two-stage ignition sintering method, which is one embodiment of the present invention, will be described.

[0027] Figure 1 This is a schematic diagram illustrating the sinter manufacturing process using a two-stage loading and two-stage ignition sintering method. In this method, granulated raw materials are loaded into two stages to form an upper raw material filling layer (hereinafter referred to as the upper stage layer) and a lower raw material filling layer (hereinafter referred to as the lower stage layer). The upper stage layer and the lower stage layer are ignited separately to carry out sintering.

[0028] First, an example of the two-stage loading and two-stage ignition sintering method, which is an existing technology, will be explained.

[0029] exist Figure 1 (Except for the oxygen-enriched gas supply device 7) In the example shown, the upper section raw materials forming the upper layer 20 and the lower section raw materials forming the lower layer 10 are prepared in different systems (two systems) and loaded onto the trolley (not shown) of the sintering machine 100 in different systems. Specifically, the raw materials for the lower section are stored in each raw material tank (1D1~1D) of the lower section raw material tank group 1D. X Within the mixing chamber, the required types and quantities of raw materials are taken out in a prescribed ratio and blended. The blended raw materials for the lower stage (lower stage blended raw materials) are fed into the lower stage drum mixer 1A for mixing, and water is added for granulation. Meanwhile, the raw materials for the upper stage are stored in the various raw material tanks (2D1~2D) of the upper raw material tank group 2D. yWithin the mixing chamber, the required types and quantities of raw materials are taken out in a prescribed ratio and blended. The blended raw materials for the upper stage (upper stage blended raw materials) are fed into the upper stage rotary drum mixer 2A for mixing, and water is added for granulation. Furthermore, the charcoal materials for the lower stage and upper stage raw materials can be pulverized coke or anthracite, etc. For example, when using pulverized coke and anthracite as raw materials, they can be stored separately in different raw material tanks, or they can be mixed in a prescribed ratio and stored in one raw material tank.

[0030] The granulated lower-stage raw materials (lower-stage raw material granules) are loaded from the lower-stage hopper 1B onto a trolley lined with bottom ore, forming the lower-stage layer 10 (lower-stage raw material filling layer). The lower-stage layer 10 is moved to the lower-stage ignition furnace 1C by moving the trolley in the trolley travel direction 5. Here, the carbon material on the surface of the lower-stage layer 10 is ignited by the lower-stage ignition furnace 1C. After ignition, the lower-stage layer 10 begins sintering through the bellows under the trolley (not shown) and the lower suction 6, which draws air from below. The sintering of the lower-stage layer 10 then proceeds downwards through the lower suction 6, forming the lower-stage combustion zone 10A.

[0031] As the lower layer 10, which begins sintering, moves to the upper hopper 2B, the granulated upper-stage feed material (upper-stage feed material granules) is loaded from the upper hopper 2B onto the ignited lower layer 10, forming the upper layer 20 (upper-stage feed material filling layer). The upper layer 20 is moved to the upper-stage ignition furnace 2C by moving the trolley in the trolley travel direction 5. Here, the carbon material on the surface of the upper layer 20 is ignited by the upper-stage ignition furnace 2C. After ignition, sintering of the upper layer 20 begins through the lower suction 6. The sintering of the upper layer 20 then proceeds downwards through the lower suction 6, forming the upper-stage combustion zone 20A.

[0032] In this two-stage loading and two-stage ignition method, a lower layer 10 is formed within the sintering machine 100. After igniting the surface of the lower layer 10, an upper layer 20 is formed on the ignited lower layer 10, and the surface of the upper layer 20 is also ignited. Furthermore, at the start of ignition of the lower layer 10, a downward suction 6 is initiated to facilitate sintering of the lower layer 10 along its thickness direction. Through further downward suction 6, after ignition of the upper layer 20, the lower combustion zone 10A of the lower layer 10 and the upper combustion zone 20A of the upper layer 20 are simultaneously and parallelly sintered and descend. When the lower combustion zone 10A and the upper combustion zone 20A reach the bottom of their respective layers, sintering using the combustion of carbon material ends, and the lower layer 10 and the upper layer 20 become the sintered section 3. Finally, the sintered section 3, after sintering, is discharged from the trolley terminal (discharge end).

[0033] The method for manufacturing sintered ore according to the present invention includes the following steps: forming a lower raw material filling layer by feeding granulated raw materials of the lower stage system into a sintering machine; forming an upper raw material filling layer by feeding granulated raw materials of the upper stage system onto the lower raw material filling layer; and igniting the surfaces of the lower raw material filling layer and the upper raw material filling layer respectively, and introducing oxygen-containing gas into the lower raw material filling layer and the upper raw material filling layer under atmospheric pressure by downward suction. Specifically, at least a portion of the gas drawn downward from the surface side of the upper raw material filling layer after ignition of the upper raw material filling layer is an oxygen-enriched gas with an oxygen concentration of 26 vol% or more and 46 vol% or less. Furthermore, in the longitudinal direction of the sintering machine, when the middle position of the interval from the outlet of the upper stage ignition furnace to the discharge end is defined as the middle position, and the first half interval is defined as the interval from the outlet of the upper stage ignition furnace to the middle position, the area for supplying oxygen-enriched gas (oxygen-enriched area) is defined as a region including a portion of the first half interval. Figure 1 As illustrated, the sintering machine 100 used in this invention, in addition to the configuration of the sintering machine used in the prior art described above, also includes an oxygen-enriched gas supply device 7. The oxygen-enriched gas supply device 7 has a hood 8 and a gas pipe 9 for supplying oxygen-enriched gas into the hood 8, supplying oxygen-enriched gas with an oxygen concentration of 26 vol% or more and 46 vol% or less to the upper section of the raw material filling layer. The supplied oxygen-enriched gas is introduced into the raw material filling layer for sintering reaction via a lower suction 6 from the bellows, and is recovered as exhaust gas via the bellows. Furthermore, in areas outside the oxygen-enriched region, the atmosphere located above the surface of the upper section of the raw material filling layer is introduced from the surface side of the upper section of the raw material filling layer into the upper section of the raw material filling layer and the lower section of the raw material filling layer via a lower suction.

[0034] Alternatively, oxygen can be injected from the gas pipe 9 onto the surface of the upper raw material filling layer without the cover 8, and drawn in together with the atmosphere. In this case, the supply of oxygen injected from the gas pipe 9 is adjusted so that the oxygen concentration on the surface of the upper raw material filling layer is 26 vol% or more and 46 vol% or less. Here, the range of oxygen concentration of the oxygen-enriched gas being 26 vol% or more and 46 vol% or less is based on the results of the embodiments described later. It should be noted that, in order to ensure rapid combustion of the charcoal material in the lower layer without supplying unnecessary oxygen, the oxygen concentration range is more preferably 36 vol% or more and 46 vol% or less.

[0035] The following description of the range (area) for supplying oxygen-enriched gas is as follows: in the longitudinal direction (cart travel direction 5) of the sintering machine 100, the middle position Z is defined as the interval from X immediately following the outlet of the upper ignition furnace to the discharge end Y; the first half of the interval is defined as the interval from X immediately following the outlet of the upper ignition furnace to the middle position Z; and the second half of the interval is defined as the interval from the middle position Z to the discharge end Y. Here, X immediately following the outlet of the upper ignition furnace indicates the upstream position where the oxygen-enriched gas supply device 7 can be installed. In the car travel direction 5 of the sintering machine 100, the location where the oxygen-enriched gas supply device 7 is installed, i.e., the area where oxygen-enriched gas is supplied to the surface of the sintered layer and suctioned downwards (the oxygen-enriched area), is located downstream of the upper ignition furnace 2C. Figure 1 In this configuration, a safety-considered gap is provided between the upper-stage ignition furnace 2C and the oxygen-enriched gas supply device 7. When a safety-considered gap is required, X immediately following the outlet of the upper-stage ignition furnace becomes the upstream end (X1) of the oxygen-enriched gas supply device 7, separated only by the safety-considered gap. If safety is not an issue, the upper-stage ignition furnace 2C and the oxygen-enriched gas supply device 7 can be installed continuously. In this case, X immediately following the outlet of the upper-stage ignition furnace becomes the downstream end (X2) of the upper-stage ignition furnace. The oxygen-enriched gas supply device 7 is preferably configured to continuously supply oxygen-enriched gas in the trolley travel direction 5. It should be noted that the upper-stage ignition furnace 2C and the oxygen-enriched gas supply device 7 can also be installed continuously, with the oxygen concentration set relatively low (e.g., 26 vol% or more and 35 vol% or less) only on the upstream side (upper-stage ignition furnace 2C side) of the oxygen-enriched gas supply device 7 in the trolley travel direction, within the range of 26 vol% or more and 46 vol% or less, to ensure safety.

[0036] The area where the oxygen-enriched gas supply device 7 is installed, i.e., the area where oxygen-enriched gas is supplied to the surface of the raw material filling layer (hereinafter also referred to as the oxygen-enriched region), is a region that includes a portion of the first half of the sintering machine 100 (the section from X immediately after the outlet of the upper ignition furnace to the intermediate position Z) in the length direction of the sintering machine 100. Here, it is preferable that the portion of the first half is the upstream side portion of the first half (for example, the portion corresponding to 0 to 0.30 when the upstream position is denoted as 0 and the downstream position as 0.5 in the direction of trolley travel). Furthermore, it is preferable that the oxygen-enriched region at least includes the portion corresponding to the first half, and that the portion corresponding to the first half is longer than the portion corresponding to the second half (the section from the intermediate position Z to the discharge end Y). Furthermore, the oxygen-enriched region may also be the entire first half and a portion of the second half. More preferably, the oxygen-enriched region is either the first half or a portion of the first half.

[0037] As described above, in the embodiments described later, determining the oxygen-enriched zone is more effective by defining it as the range from immediately following the outlet of the ignition furnace X to the intermediate position Z (the first half of the zone) or a portion thereof (a part of the first half of the zone) than by defining the oxygen-enriched gas supply range as the range from the intermediate position Z to the discharge end Y (the second half of the zone). Therefore, the effect can be obtained if the oxygen-enriched zone is a region that includes the first half of the zone or a region that includes a part of the first half of the zone. Here, the reason why oxygen enrichment in the first half of the zone is more effective than oxygen enrichment in the second half of the zone when the oxygen-enriched zone is considered as part of the entire zone is as follows.

[0038] Oxygen enrichment is implemented to improve the situation where the combustion of charcoal in the lower layer is inactive (incomplete) due to insufficient oxygen. In the oxygen-enriched zone, the combustion of charcoal becomes more active, and the temperature inside the sintering machine can be appropriately maintained at a high temperature. When oxygen enrichment is implemented in the first half of the zone, by maintaining the high temperature in the first half, the temperature inside the sintering machine can be maintained at a high temperature even if oxygen enrichment is not implemented in the second half, allowing for the sintering reaction to proceed. On the other hand, if oxygen enrichment is implemented in the second half of the zone without oxygen enrichment in the first half, the combustion of charcoal in the first half is inactive, and the temperature inside the sintering machine decreases. Therefore, even if oxygen enrichment is implemented in the second half, it is difficult to fully restore the temperature inside the sintering machine. Therefore, oxygen enrichment in the first half of the zone (or the upstream part of the first half of the zone) is considered effective.

[0039] Furthermore, in the sintering machine, particle size segregation occurs during the loading of the raw materials. Compared to main raw materials such as iron ore, finer-grained charcoal has a higher concentration at the top. Therefore, in the two-stage loading and two-stage ignition method, the amount of charcoal in the upper layer is greater than that in the lower layer. The more charcoal, the more oxygen is required for combustion. Therefore, it is preferable to enrich the oxygen in the first half of the combustion zone above the layer. When limiting the oxygen-enriched area to control oxygen costs, etc., based on the above reasons, it is preferable to designate a region that includes at least a portion of the first half of the zone (the regions described in the three paragraphs preceding this one).

[0040] Furthermore, the raw materials used in the upper and lower stages can be the same or different. Alternatively, under the same conditions, the raw materials used in the upper and lower stages can be prepared using the same system instead of two separate systems.

[0041] Here, as illustrated in the embodiments described later, in the method for manufacturing sintered ore according to the present invention, it is preferable to use a portion or all of the charcoal material for the raw materials used in the next stage as highly combustible charcoal material. As exemplified in Table 1, highly combustible charcoal material (binder material) has a combustion rate (at 700°C) of 0.0022 (1 / sec) or higher, including coal coke, palm kernel shell charcoal (PKS charcoal), and charcoal produced by dry distillation of wood. Furthermore, highly combustible charcoal material has a lower combustion start temperature compared to coke and anthracite.

[0042] Palm kernel shell charcoal (PKS charcoal) is a solid carbide produced by heat treatment (dry distillation) of palm kernel shells. Additionally, coke is a sintering charcoal material (carbonized material) produced by dry distilling low-flowability coal with a Rhoga index below 10 as the raw coal. Coke is produced by dry distilling coal (including blended coal) as raw material using a pyrolysis furnace (e.g., a rotary kiln). By using low-flowability coal with a Rhoga index below 10 as the raw coal, highly combustible coke can be produced. Furthermore, the flowability of coal refers to the degree of low molecular weight reduction during heating; low-flowability coal is coal that is difficult to undergo low molecular weight reduction during heating.

[0043] The Roga index is calculated using the Roga test method specified in JIS-M8801 (2008). The Roga test method is explained below.

[0044] First, 1 g of low-grade coal with a particle size of less than 200 μm and 5 g of standard anthracite are thoroughly mixed in a crucible. The standard anthracite is selected based on an ash content (dry basis) of less than 4.0%, a volatile matter content (dry basis) of more than 5.0% and less than 6.5%, and a particle size of more than 300 μm and less than 400 μm. Next, a certain load (59 N) is applied to the low-grade coal and standard anthracite in the crucible for a specified time (at least 30 seconds) using a heat-resistant steel weight.

[0045] Next, the aforementioned crucible was placed in an electric furnace with the furnace temperature set at 850±10℃, and low-grade coal and standard anthracite were heated (dry distilled) for 15 minutes. Then, the heated crucible was placed on a heat-resistant plate and cooled for 45 minutes. The mass of the contents of the crucible (hereinafter sometimes referred to as the dry distillate) was measured, and the mass of the dry distillate on the sieve was measured using a 1 mm perforated plate sieve.

[0046] Next, the contents of the crucible (the distillate) are placed into the drum, and the drum is rotated at a specified speed (50 rpm) for 5 minutes to decompose the distillate. The drum has an inner diameter of 200 mm and a depth of 70 mm. Two blades with a length of 70 mm and a width of 30 mm are symmetrically arranged on the inner circumferential wall of the drum.

[0047] Next, the pyrolyzed product after the destructive treatment was sieved using a 1 mm perforated plate sieve, and the mass on the sieve was measured. The above destructive treatment was repeated 3 times, and the Rhoga index was calculated based on the following formula (1). In formula (1), RI is the Rhoga index. m1 is the total mass [g] of the contents of the crucible after destructive treatment (pyrolyzed product), m2 is the mass [g] of the pyrolyzed product on the sieve before the first destructive treatment, m3 is the mass [g] of the pyrolyzed product on the sieve after the first destructive treatment, m4 is the mass [g] of the pyrolyzed product on the sieve after the second destructive treatment, and m5 is the mass [g] of the pyrolyzed product on the sieve after the third destructive treatment.

[0048] [Mathematical Expression 1] The combustion rate (700℃) shown in Table 1 is calculated as follows.

[0049] First, a 10 mg sample, to be tested, was placed on a thermal balance inside the apparatus. After thoroughly purging the apparatus with nitrogen, it was heated at a rate of 100 °C / min with nitrogen flowing at a rate of 200 ml / min. Once the sample temperature reached 700 °C, the flowing gas was immediately switched from nitrogen to air at a rate of 200 ml / min, and the weight loss was measured. The resulting data included the reaction time t (the time elapsed after switching the flowing gas from nitrogen to air) and the reaction rate Xr (Xr = [weight loss in each time period - weight of unburned material at the end of the test] / [initial weight of the sample - weight of unburned material at the end of the test]). Then, the reaction rate dXr / dt was calculated for each reaction rate, and the average value of Xr from 0 to 0.5 was taken as the combustion rate at 700 °C.

[0050] In the two-stage loading and two-stage ignition method, the oxygen concentration of the gas supplied to the lower stage is lower than that of the upper stage. Highly combustible charcoal has a low combustion initiation temperature, thus it will burn even at low temperatures in a low-oxygen environment, thereby suppressing incomplete combustion (combustion residue of the charcoal). Here, as shown in the embodiments described later, if oxygen enrichment is combined with the use of highly combustible charcoal in the lower stage, productivity is significantly improved. This effect is based on the following reasons. As shown in Table 1, highly combustible charcoal burns quickly. However, even when using highly combustible charcoal, incomplete combustion can be suppressed without oxygen enrichment, but due to insufficient oxygen, the combustion rate cannot reach a sufficient speed and is inactive, making it difficult to maintain an appropriate high temperature inside the sintering machine. On the other hand, if oxygen enrichment is implemented, the combustion rate of the highly combustible charcoal can be adjusted by the oxygen concentration. By implementing oxygen enrichment, the sintering speed can be accelerated, making the charcoal combustion more active, and the temperature inside the sintering machine can be appropriately maintained at a high temperature. Furthermore, due to the rapid combustion rate (700℃) of highly combustible charcoal, using it in the sintering process shortens the time until the total amount of charcoal has burned out, and also shortens the time until sintering is complete. By shortening the time until sintering is finished, the amount of sinter produced per unit time increases, and productivity (t-sinter / day / m³) improves. 2 (t / d / m) 2 Therefore, actively using highly combustible charcoal in the lower layers is effective in improving productivity (increasing sintering speed). The preferred percentage of highly combustible charcoal relative to the total charcoal usage is 30% to 100% by mass. If it is below 30% by mass, the sintering speed will not increase due to the combustion rate of the charcoal other than the highly combustible charcoal. However, if the percentage of highly combustible charcoal is increased to 100% by mass, the combustion rate and sintering speed will increase accordingly.

[0051] The high-combustibility charcoal material is applied to the lower section layer as follows.

[0052] like Figure 1 As shown, the upper-stage raw materials forming the upper layer 20 and the lower-stage raw materials forming the lower layer 10 are from different systems (two systems). Furthermore, the raw material tanks (1D1~1D) in the lower-stage raw material tank group 1D... X The system includes raw material tanks for storing highly combustible charcoal. For example, raw material tank 1D1 (first charcoal tank) in the lower raw material tank group 1D stores charcoal other than highly combustible charcoal (e.g., coke and / or anthracite), while raw material tank 1D2 (second charcoal tank) stores highly combustible charcoal (e.g., coal coke and / or PKS char). When using two or more types of charcoal other than highly combustible charcoal, or two or more types of highly combustible charcoal, raw material tanks can also be set up for storage by type.

[0053] Example Examples demonstrating the effects of the present invention will be described below. It should be noted that the present invention is not limited to the following examples.

[0054] The inventors conducted a sintering pot test (300 mm in diameter) capable of simulating sintering in a DL-type sintering machine, verifying the effectiveness of the invention. The sintering pot test apparatus does not utilize a trolley to move the raw material filling layer as in a DL-type sintering machine; instead, it is a test apparatus in which the raw materials are loaded into a container of a specified size, ignited from above, and sintered by suction from below.

[0055] As shown in Table 3 below, there are 14 experiments comparing Examples 1 to 5 and Examples 1 to 9 of the invention.

[0056] (Raw material formulation) Table 2 shows the raw materials and their proportions. As shown in Table 2, two types of raw materials, compound material a and compound material b, were prepared as the compounding raw materials. Iron ore A-D, peridotite, quicklime, and limestone, as new raw materials, were compounded in the proportions shown in Table 2. Iron ore A-D used iron ore from different origins. Furthermore, the new raw materials were set at 100% by mass, and the additive amount (excluding binder material, charcoal) was 4.5% by mass. As charcoal, coke powder was added to compound material a, and half coke powder and PKS charcoal as a highly combustible charcoal were added to compound material b. Additionally, as shown in Table 3 described later, compound material b was used only in the lower layer of Comparative Example 5 and Invention Examples 8 and 9. That is, in Comparative Example 5 and Invention Examples 8 and 9, PKS charcoal was used as a binder material in the lower layer.

[0057] (Granulation method) The raw materials from the upper and lower layers were granulated separately. The raw materials were mixed for 4 minutes using a drum mixer (600 mm in diameter, 25 rpm), and then 7.2% by mass of water was added relative to the raw materials, followed by further granulation for 4 minutes.

[0058] (Experimental level) The test levels are shown below. As shown in the upper part of Table 3, in Comparative Examples 1-5 and Invention Examples 1-9, the oxygen concentration of the gas supplied from the surface side of the upper layer and drawn from below under atmospheric pressure was varied within the range of 21 vol% (without oxygen enrichment) to 50 vol%, and the two-stage loading and two-stage ignition method was implemented. In addition, as detailed later, the supply of oxygen-enriched gas was set to the layer height range (position) of the first half of the actual machine (the first half of the section from the outlet of the upper ignition furnace to the end of the ore discharge) in the sintering pot tests of Comparative Examples 2, 4, and Invention Examples 1-3, 6-9; in Comparative Example 3, it was set to the layer height range of the second half of the section (the second half of the section from the outlet of the upper ignition furnace to the end of the ore discharge); in Invention Example 4, it was set to the layer height range of a part of the first half of the section; and in Invention Example 5, it was set to the layer height range of both the first and second half of the section (the entire section). Furthermore, in Example 4, the first half of the interval specifically refers to the upstream portion of the first half of the interval in the actual machine. When the length of the first half of the interval is set to 0.5, the upstream portion is defined as a region with a length of 0.28. Additionally, oxygen enrichment was not performed in Comparative Examples 1 and 5.

[0059] (Firing conditions) The thickness of each layer in the two sections is set as follows: 500mm for the lower section and 300mm for the upper section. For the pots, two cylindrical pots are prepared: one for the lower section (300mm in diameter) with a height of 500mm and the other for the upper section (300mm in diameter) with a height of 300mm.

[0060] First, granulated raw materials for the lower and upper sections are loaded into the lower and upper section pots, respectively, to achieve a layer height of 500 mm for the lower section and 300 mm for the upper section. Then, the lower section pot with a layer height of 500 mm is set up, and the surface of the lower section layer is ignited for 1 minute. Next, the upper section pot with a layer height of 300 mm is placed on top of the lower section pot. To ensure sintering of both sections, after confirming the temperature rise at a position of 320 mm (320 mm from the lower surface of the lower section) (measured using a thermocouple as described later), the surface of the upper section layer is ignited for 1 minute. The suction pressure is set to a constant 1200 mmAq (11.8 kPa) from the start of ignition.

[0061] (Sintering time) Thermocouples were inserted at heights of 440mm, 320mm, 230mm, and 170mm to measure the temperature within each layer. The slower of the two sintering processes (upper and lower layers) was considered the sintering completion time for the entire raw material filling layer. Therefore, the longer of the time required from the start of the second temperature rise at the thermocouple at the 440mm position (sintering completion of the upper layer) to the peak exhaust temperature at the wind box position (sintering completion of the lower layer) was taken as the sintering time for the entire raw material filling layer. Suction was stopped 3 minutes after the sintering completion time, marking the end of sintering.

[0062] (Oxygen-rich) As shown in Table 3, oxygen enrichment was implemented in four modes: a portion of the first half of the test zone, the first half of the test zone, the second half of the test zone, and the entire test zone. In the first half of the test zone, oxygen enrichment was implemented from the moment the upper ignition began (more than 0 seconds but less than 2 seconds) until the temperature rose to 230 mm. In the first half of the test zone, oxygen enrichment was implemented from the moment the upper ignition began until the temperature rose to 170 mm, approximately half the height of the upper layer. In the second half of the test zone, oxygen enrichment was implemented from the moment the temperature rose to 170 mm until the end of the experiment. In the entire test zone, oxygen enrichment was implemented from the moment the upper ignition began until the end of the experiment.

[0063] (Finish rate) The yield was determined as follows. After sintering, the sintered blocks were dropped from a height of 2m four times. Particles with a diameter of +5mm (greater than 5mm) were considered finished sintered products, and their mass was calculated. The proportion (mass%) of this finished product relative to the total mass of the sintered blocks was defined as the yield (+5mm%).

[0064] (productivity) Productivity is calculated based on the sintering time determined as described above, using the following equation (2).

[0065] Productivity (t / d / m) 2 = Sintered product quantity (t) / Sintered area (0.07m²) 2 (2) / Sintering time (days) (Sinter strength) The strength of the sinter was determined based on JIS M8712 (2009) according to the cold strength (rotational strength index TI). The mass of the test sample was set at 15 kg (15 mm to 40 mm in size). Furthermore, the strength was measured only on the lower section of the sinter (the sinter in the lower section of the boiler). The apparatus used for the measurement was a cylindrical container (1000 mm in diameter, 500 mm in depth), in which the test sample was placed and rotated at 25 rpm for 8 minutes. The mass of the recovered sinter after rotation (+6 mm) was calculated, and the ratio (mass%) of this sinter to the 15 kg test sample was taken as the cold strength.

[0066] (Experimental Results) The test results are shown in the lower part of Table 3. Figure 2 and Figure 3 The test results shown in Table 3 are plotted as a graph. Figure 2 This is a graph showing the relationship between the oxygen concentration (vol%) of oxygen-enriched gas and the yield of finished products (mass%). Figure 3 This represents the relationship between oxygen concentration (vol%) and productivity (t / d / m³) in oxygen-enriched gas. 2 A diagram showing the relationship between ). Furthermore, in Figure 3 The dashed line shown represents the straight line connecting the data points of Comparative Example 1 and Comparative Example 2, shifted parallel to the line in the positive direction by 0.5 (t / d / m). 2 The test case located above the dotted line is taken as the invention example.

[0067] The test results without using highly combustible charcoal are shown in Table 3. Figure 2 and Figure 3As shown, compared to Comparative Examples 1 and 2, the yield and productivity of Invention Examples 1 to 7 are significantly improved. Furthermore, regarding strength, it is approximately the same as Comparative Examples 1 and 2 in Invention Example 1, but improved in Invention Examples 2 to 7. In Comparative Example 4 with an oxygen concentration of 50 vol%, the yield, strength, and productivity are reduced compared to Invention Example 7 with an oxygen concentration of 46 vol%. Therefore, excessive oxygen enrichment is unnecessary, and the preferred oxygen concentration is 26 vol% to 46 vol%. Oxygen enrichment incurs costs for oxygen production (e.g., in methods for separating oxygen from air, air compression and cooling are required, as well as electricity costs), resulting in low cost efficiency. Therefore, Comparative Example 4 with an oxygen concentration of 50 vol% is a comparative example rather than an invention example. Furthermore, the results from Invention Examples 3 to 5 and Comparative Example 3, where the oxygen concentration is kept constant at 36 vol% and the oxygen enrichment position is changed, indicate the following: Oxygen enrichment in the first half (Invention Example 3) is more effective than in the latter half (Comparative Example 4). Furthermore, compared to the first half of the interval (Example 3), the value of a portion of the first half of the interval (Example 4) is lower, but when calculating the improvement rate of yield, strength, and productivity relative to the length of the oxygen-enriched interval (based on Comparative Example 1), the portion of the first half of the interval can more effectively enjoy the effect. In particular, it is known that in Example 4, it is preferable to perform oxygen enrichment in the upstream portion of the first half of the interval, and to perform oxygen enrichment in a certain interval immediately following the outlet of the ignition furnace in the upper section.

[0068] The test results using highly combustible charcoal are as follows. In Comparative Example 5, which did not undergo oxygen enrichment but incorporated highly combustible charcoal (PKS charcoal) in the lower layer, both yield and productivity decreased compared to Comparative Example 1, which did not incorporate PKS charcoal. In contrast, in Invention Example 8, which incorporated PKS charcoal in the lower layer and underwent oxygen enrichment, productivity and yield were significantly improved compared to Comparative Example 5, which did not undergo oxygen enrichment but incorporated highly combustible charcoal (PKS charcoal) in the lower layer, and Comparative Example 1, which did not undergo either oxygen enrichment or PKS charcoal. Furthermore, in Invention Example 9, which incorporated PKS charcoal to increase the oxygen concentration of the supply gas, thereby achieving oxygen enrichment, productivity and yield were significantly improved compared to Comparative Example 5, which did not undergo oxygen enrichment but incorporated highly combustible charcoal (PKS charcoal) in the lower layer. In Example 9 of this invention (oxygen concentration 46 vol%), compared with Example 8 of this invention (oxygen concentration 26 vol%), which incorporated PKS char in the lower layer and underwent oxygen enrichment, productivity and yield were improved, with productivity being the highest among all test examples. It should be noted that the same effect was observed not only with PKS char but also with coal coke, a highly combustible charcoal material. Based on these results, it is clear that the combination of using highly combustible charcoal materials and oxygen enrichment is effective.

[0069] Explanation of reference numerals in the attached figures 100: Sintering machine; 1A: Drum mixer for lower section; 1B: Hopper for lower section; 1C: Ignition furnace for lower section; 1D: Raw material tank assembly for lower section (raw material tanks 1D1~1D) X 2A: Upper section uses a rotary drum mixer; 2B: Upper section uses a hopper; 2C: Upper section uses an ignition furnace; 2D: Upper section uses a raw material trough assembly (upper section raw material troughs 2D1~2D). y ), 3: Sintering section, 5: Carriage travel direction, 6: Lower suction, 7: Oxygen-enriched gas supply equipment, 8: Cover, 9: Gas pipe, 10: Lower section, 10A: Lower section combustion zone, 20: Upper section, 20A: Upper section combustion zone, X (X1, X2): Immediately after the outlet of the upper section ignition furnace, Y: Ore discharge end, Z: Middle position.

Claims

1. A method for manufacturing sintered ore, comprising the following steps: The process of forming a lower stage raw material filling layer by loading granulated raw materials of the lower stage system into the sintering machine; The process of forming the upper raw material filling layer by loading the upper raw material granules into the lower raw material filling layer; and The process involves igniting the surfaces of the lower and upper raw material filling layers, respectively, and introducing oxygen-containing gas into the lower and upper raw material filling layers under atmospheric pressure through suction from below. in, After the ignition of the upper raw material filling layer is completed, at least a portion of the gas drawn from below from the surface side of the upper raw material filling layer is set as an oxygen-enriched gas with an oxygen concentration of 26% by volume or more and 46% by volume or less. In the longitudinal direction of the sintering machine, when the middle position of the interval from the outlet of the upper ignition furnace to the end of the ore discharge is defined as the middle position, and the interval from the outlet of the upper ignition furnace to the middle position is defined as the first half interval, the area for supplying the oxygen-enriched gas is the area that includes a part of the first half interval.

2. The method for manufacturing sintered ore according to claim 1, wherein, A portion of the first half of the interval is the upstream portion of the first half of the interval.

3. The method for manufacturing sintered ore according to claim 1, wherein, When the section from the middle position to the discharge end in the length direction of the sintering machine is defined as the second half of the section, The region supplying the oxygen-enriched gas includes at least a portion corresponding to the first half of the interval, and the portion corresponding to the first half of the interval is longer than the portion corresponding to the second half of the interval.

4. The method for manufacturing sintered ore according to claim 1, wherein, The region that supplies the oxygen-enriched gas is either the first half of the interval or a portion thereof.

5. The method for producing sintered ore according to any one of claims 1 to 4, wherein, As a raw material for the lower section filling layer, it is combined with highly combustible charcoal material with a combustion rate of 0.0022 (1 / sec) or higher at 700°C.

6. The method for manufacturing sintered ore according to claim 5, wherein, The highly combustible charcoal material comprises carbonized material obtained by dry distillation of coal with a Roga index of less than 10.

7. The method for manufacturing sintered ore according to claim 5, wherein, The highly combustible charcoal material contains palm kernel shell charcoal.

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