Manufacturing method of sintered ore

Abstract

To improve a yield of a sintered ore product to be manufactured with a simpler method.SOLUTION: A manufacturing method of a sintered ore includes: charging a mixed material including an iron ore, a CaO-containing material, an auxiliary material and a coagulant material into a sintering machine; sintering the charged mixed material to produce a sinter cake; and screening the sinter cake into a sintered ore product and return fines by a classifier. The manufacturing method of a sintered ore further includes: a step of measuring the CaO concentration of the return fines; and an action execution step of executing, if the measured CaO concentration of the return fines is threshold concentration lower than target concentration, at least one of actions of adjusting the mixture amount of the CaO-containing material, adjusting the grain size of the CaO-containing material and changing the type of the CaO-containing material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing sintered ore for producing sintered ore for a blast furnace. [Background technology]

[0002] Currently, the main raw material for blast furnace pig iron production is sintered ore. Sintered ore (product sintered ore) used as a blast furnace feedstock is generally produced by sintering raw materials for sintered ore production (sintering raw materials), including iron ore, in a downward suction type Dwight Lloyd (DL) sintering machine, and then regulating the grain size to a specified size by crushing, sieving, etc.

[0003] Conventionally, in order to improve the yield of sintered ore, it has been common to carefully control the blending ratio of sintering raw materials in the sintered ore production process in accordance with fluctuations in the components of the sintered ore. Patent Document 1 describes a method for producing sintered ore in which the amount of coagulant mixed is adjusted using the results of a first measurement process in which the component concentration of at least one of the iron-containing raw material, the sintering raw material, and the granulated sintering raw material is continuously measured, and the results of a second measurement process in which the component concentration of at least one of the cooled sintered ore, the finished sintered ore, and the return ore is continuously measured. This is a technology for adjusting the amount of sintering raw material mixed and the production conditions of sintered ore based on the fluctuation in the component concentration of the sintering raw material during sintered ore production, or the change in the component concentration that changes due to the sintering reaction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-131847 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the manufacturing method described in Patent Document 1, the change in component concentration caused by the sintering reaction is monitored, and therefore, it is necessary to continuously measure the component concentrations of the sintering raw material before sintering in the first measurement step, and to continuously measure the component concentrations of the sintered ore in the second measurement step, which makes the control complicated.

[0006] The present invention provides a method for producing sintered ore, which can improve the product yield of the produced sintered ore by a simpler method. [Means for solving the problem]

[0007] [1] A method for producing sintered ore, comprising: charging a blended raw material containing iron ore, a CaO-containing raw material, and a coagulant into a sintering machine, sintering the charged blended raw material to produce a sintered cake, and sieving the sintered cake into a finished sintered ore and return ore with a classification device, the method comprising: a step of measuring the CaO concentration of the return ore; and an action implementation step of, when the measured CaO concentration of the return ore becomes a threshold concentration lower than a target concentration, carrying out at least one of an action of adjusting the blending amount of the CaO-containing raw material, an action of adjusting the particle size of the CaO-containing raw material, and an action of changing the type of the CaO-containing raw material. [2] A method for producing sintered ore as described in [1], comprising a step of measuring the reducibility of the product sintered ore, and if the reducibility falls below an operational standard value after the action implementation step, an action different from the action implemented in the action implementation step is implemented. [3] A method for producing sintered ore described in [1] or [2], which includes a step of calculating the productivity of the finished sintered ore, and if the productivity falls below an operational standard value after the action implementation step, an action different from the action implemented in the action implementation step is implemented. [4] A method for producing sintered ore, comprising: charging a blended raw material containing iron ore, a CaO-containing raw material, and a coagulant into a sintering machine, sintering the charged blended raw material to produce a sintered cake, and sieving the sintered cake into a finished sintered ore and return ore with a classification device, the method comprising the steps of: measuring the CaO concentration of the return ore; measuring the CaO concentration of the finished sintered ore; and, when the difference between the CaO concentration of the finished sintered ore and the CaO concentration of the return ore reaches a threshold value lower than an initial value, carrying out an action to adjust the particle size of the CaO-containing raw material. Effect of the Invention

[0008] According to the present invention, the CaO concentration of the return ore is measured, and an action is taken to increase the amount of melt generated during sintering of the sintering raw material so that the measured CaO concentration of the return ore becomes a target concentration, thereby making it possible to improve the product yield (hereinafter, also simply referred to as the yield). [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram illustrating a method for producing sintered ore according to the first embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <First embodiment> In the method for producing sintered ore according to the present embodiment, a blended raw material (sintering raw material) containing iron ore, CaO-containing raw material, auxiliary raw material, and a coagulant (carbon material) is charged into a sintering machine, the charged blended raw material is sintered to produce a sintered cake, the sintered cake is sieved into a product sintered ore and return ore by a classifier, and the sieved product sintered ore is transported to a blast furnace facility. In this method for producing sintered ore, an action is taken to increase the amount of molten liquid generated during sintering of the sintering raw material, using the CaO concentration of the return ore as an index. Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an example of a method for producing sintered ore.

[0011] As shown in Fig. 1, the method for producing sintered ore includes a raw material blending process S1, a granulation process S2, a sintering process S3, and a sizing process S4. After each process, the raw materials and semi-finished products are transported to the next process by a transport device such as a belt conveyor.

[0012] The raw material blending step S1 is a step of blending raw materials (blended raw materials) for sintered ore. The raw materials used in the blend include iron raw materials such as iron ore (powder), iron-containing miscellaneous materials such as scale and steelmaking dust, and SiO 2 The raw materials are appropriately used, such as MgO-containing auxiliary raw materials such as olivine, CaO-containing raw materials, return ore, and agglomeration materials (carbon materials) that serve as fuel for sintering (aggregation). Each blended raw material is stored in a plurality of raw material tanks, and a predetermined amount of each blended raw material is cut out onto a belt conveyor, blended in a predetermined ratio (blending ratio), and sent to the granulation process S2.

[0013] The granulation step S2 is a step of granulating the blended raw materials (adjusting the particle size distribution) for the purpose of ensuring the breathability of the raw material packed bed. The mixed raw materials transported by the belt conveyor are fed into the granulator. After mixing for a specified time in the granulator, water is added (humidity control), and granulation is performed by mixing for a specified time, and pseudo-particles are created, which are the aggregates of the primary particles of the raw materials. The mixed raw materials after granulation (hereinafter also referred to as the mixed raw material granules) are sent to the sintering process S3. In the granulation process S2, some of the mixed raw material particles become pseudo-particles. In general, as described in the 3rd Edition Iron and Steel Handbook II, Pig Iron and Steelmaking, p. 84 (Figure 2.4) [October 15, 1979], fine raw materials with a particle size of less than 0.25 mm, which are the main target of granulation, form pseudo-particles by adhering to the periphery of particles of 1.00 mm or more as core particles, but it is said that particles of intermediate particle sizes between 0.25 mm and less than 1.00 mm are difficult to granulate and are difficult to become pseudo-particles.

[0014] The sintering step S3 is a step of sintering the blended raw material granules to produce a sintered cake (sinter cake). The granulated raw materials are stored in a mixed raw material surge hopper from the belt conveyor, and then loaded onto the pallet of a Dwight Lloyd (DL) sintering machine to form a raw material packed bed. The raw material packed bed is ignited by an ignition furnace, and sintered by the combustion heat of the coagulant in the raw material packed bed. The sintered cake obtained by sintering is discharged from the ore discharge end of the sintering machine, and roughly crushed into sintered ore with a particle size of less than 200 mm by a crusher (primary crushing), and sent to the sizing process S4.

[0015] The sizing step S4 is a step of cooling and pulverizing the roughly crushed lump-shaped sintered ore, and then sizing the pulverized sintered ore for use in a blast furnace. The lump sintered ore is cooled by a cooling device to a temperature at which it can be transported on a belt conveyor, and then crushed by a crusher (secondary crushing). The crushed sintered ore is sized by screening using a multi-stage classification device. Sintered ore (product sintered ore) of a particle size suitable for blast furnace charging is selected by the sizing process. The particle size suitable for blast furnace charging is, for example, sintered ore with a particle size of 5 mm or more and less than 50 mm. Here, a particle size of 5 mm or more and less than 50 mm refers to a particle size that is an oversize particle when sieved through a 5 mm sieve and an undersize particle when sieved through a 50 mm sieve. Note that sintered ore with a particle size of 50 mm or more is crushed to a particle size of less than 50 mm, and then sized again.

[0016] Each classifier is, for example, a rocking classifier with an inclined screen (sieve mesh), and the rocking motion is imparted by an eccentric drive mechanism. The classification intensity can be adjusted by changing the rotation speed of the motor that rotates this drive mechanism. The product sintered ore selected by the classifier is transferred to the blast furnace transfer line L2, and the remaining fine sintered ore is transferred to the return ore transfer line L1 as return ore.

[0017] The return ore transport line L1 is a line that returns fine sintered ore that is not suitable for use as a blast furnace raw material to the raw material blending process S1. The return ore transport line L1 is equipped with a transport device such as a conveyor, and transports sintered ore with a particle size of less than 5 mm, which is smaller than the finished sintered ore (hereinafter, sintered ore with a particle size of less than 5 mm is also referred to as -5 mm sintered ore), into the raw material tank for return ore described above. A particle size of less than 5 mm refers to the particle size that falls under the sieve when sieved through a 5 mm sieve. The transported -5 mm sintered ore is mixed into the raw material mix as return ore.

[0018] The blast furnace transport line L2 is a line that transports the finished sintered ore to the blast furnace facility. The blast furnace transport line L2 is equipped with conveyors and other transport devices. The product sintered ore with a particle size of 5 mm or more but less than 50 mm is transported to the blast furnace equipment and used as the raw material for blast furnace iron production. The product sintered ore is charged into the blast furnace by multiple belt conveyors together with reducing materials such as coke, limestone, and olivine produced in a separate process.

[0019] Next, a method for taking an action to increase the amount of molten liquid generated during sintering of sinter raw materials using the CaO concentration of return ore as an index will be described. The product yield, which is the ratio of the actual sintered ore to the sinter cake (excluding the bedding ore), can be improved by reducing the amount of return ore generated. Conventionally, the yield has been monitored based on the information on the increase in the amount of return ore stored in the raw material tank for storing return ore (information on the rate of return ore generation).

[0020] The inventors have focused on the fact that the CaO concentration of return ore is lower than the CaO concentration of the blended raw materials and the CaO concentration of the finished sintered ore, and have invented a technology to monitor the yield by using the CaO concentration of return ore as a new detection point. Return ore is mainly generated due to the fragility of the upper layer of the sinter cake, and it is considered that this is because the amount of melt generated, which is necessary for sintering, is small due to a lack of CaO components necessary for melting. In other words, the yield of sintered ore is correlated with the amount of melt generated, and the yield increases as the amount of melt generated increases. This is because the force that binds the ores together becomes stronger as the amount of melt generated increases. On the other hand, when the amount of melt generated becomes less than a certain value (threshold value), the yield drops sharply. From this, it was thought that when the CaO concentration of the return ore becomes low, the product yield can be improved by taking action to increase the amount of melt generated during sintering of the sintering raw materials and improve the melting property of the upper layer.

[0021] A specific method for measuring the CaO concentration in the return ore and actions to be taken based on the measured CaO concentration in the return ore will be described below. (1) Measurement of CaO concentration in return fines In the sinter ore manufacturing method of this embodiment, a predetermined amount of return ore is collected in the return ore conveying line L1, for example, every 4 hours, and the CaO concentration of the return ore is measured. The CaO concentration can be measured by the method described in JIS M8206 (iron ore--ICP atomic emission spectrometry) or the method described in JIS M8205 (iron ore--X-ray fluorescence analysis). An operator checks the measured CaO concentration of the return ore. The method for measuring the CaO concentration in the return ore is not limited to the above-mentioned method, and a component analyzer capable of online analysis of the return ore on the return ore transport line L1 (while being transported by a belt conveyor, hereinafter referred to as on-belt) (hereinafter, the measurement target on the belt is also referred to as an on-belt sample) may be used.

[0022] (2) Implementing Actions Based on the measured CaO concentration of the return ore, the worker performs at least one of the actions described below (action performing step). Specifically, when the CaO concentration of the return ore is lower than the target CaO concentration (hereinafter referred to as the target concentration), an action is performed to increase the amount of melt generated during sintering of the sintering raw material to improve the yield. The target concentration can be set based on past production results. For example, the target concentration can be 9.5% by mass. The target concentration can be changed based on the raw material conditions, heat level, etc. The threshold concentration, which is the threshold for taking action, can be 95% of the target concentration. When the target concentration is 9.5% by mass, the threshold concentration is 9.215% by mass (≒ 9.2% by mass). When an action is carried out and the CaO concentration in the return ore reaches the target concentration, the action may be returned to its original state or may be continued as is.

[0023] Next, the details of the action to be taken when the CaO concentration of the return ore is reduced will be described. The operator can appropriately select the action to be taken from the following three actions.

[0024] (2-1) Action 1: Adjustment of particle size of CaO-containing raw materials The particle size of the CaO-containing raw material used as the sintering raw material is made fine. In other words, the particle size of the CaO-containing raw material fed from the raw material tank to the granulator is made small. This causes the CaO-containing raw material to segregate to the upper layer, improving the melting property of the upper layer and improving the yield. With regard to the particle size of the CaO-containing raw material, for example, in the production process of the CaO-containing raw material, fine particles can be selected by reducing the openings of a sieve used after pulverizing the CaO-containing raw material. (2-2) Action 2: Adjustment of the amount of CaO-containing raw materials The amount of CaO-containing raw material in the raw material mix is ​​increased. In other words, the amount of CaO-containing raw material fed from the raw material tank to the granulator is increased, and the ratio of CaO-containing raw material in the raw material mix (concentration of CaO-containing raw material) is increased. This increases the amount of CaO-containing raw material in the entire raw material packed bed, which increases the amount of molten liquid generated during sintering of the sintering raw material and reduces the brittleness of the sintered cake.

[0025] (2-3) Action 3: Change the type (brand) of CaO-containing raw materials Change the type (brand) of the CaO-containing raw material. When multiple CaO-containing raw materials are used in combination, changing the type of CaO-containing raw material also includes changing the blending ratio of those raw materials. Types of CaO-containing raw materials include limestone (CaCO 3 ), quicklime (CaO), slaked lime (Ca(OH) 2 ), dolomite (CaMg(CO 3 ) 2 ), steel slag, etc. The amount of molten liquid generated during sintering of the sintering raw materials is affected by the type of CaO-containing raw material. For example, by changing the type of CaO-containing raw material to one with high melting property, the amount of molten liquid generated can be increased. That is, in order to increase the amount of molten liquid generated during sintering of the sintering raw materials, it is necessary to change to a type with higher melting property. For example, the amount of molten liquid generated during sintering of the sintering raw materials can be increased by changing from dolomite to limestone, from steel slag to limestone, or from limestone to quicklime or slaked lime. In addition, when steelmaking slag and limestone are mixed as CaO-containing raw materials in a ratio of steelmaking slag:limestone = 20 mass%:80 mass%, the amount of molten liquid generated during sintering of the sintering raw materials can be increased by changing the mixing ratio to, for example, 100 mass% limestone.

[0026] The actions for increasing the amount of molten liquid generated during sintering of the sintering raw material have been described above. However, the operator can select an appropriate action depending on, for example, the configuration of the sintering machine.

[0027] According to the above embodiment, the CaO concentration of the return ore is measured, and at least one of the following actions is carried out so that the measured CaO concentration of the return ore becomes a target concentration: adjusting the blending amount of the CaO-containing raw material, adjusting the particle size of the CaO-containing raw material, and changing the type of the CaO-containing raw material. This makes it possible to improve the melting property of the upper layer and increase the product yield.

[0028] <Second embodiment> Next, a method for producing sintered ore according to a second embodiment of the present invention will be described. The method for producing sintered ore according to this embodiment uses the reducibility (RI) of sintered ore as an index in addition to the CaO concentration of return ore. The reducibility of sintered ore is an index showing how easily the sintered ore is reduced in the upper and middle parts of the shaft inside the blast furnace, and sintered ore with high reducibility is desired. On the other hand, it is known that if sintered ore contains a lot of CaO, the reducibility (RI) of the sintered ore decreases. The CaO melt produced at high temperatures during the sintering process blocks the pores in the sintered body, reducing the surface area that comes into contact with the reducing gas in the blast furnace, making it difficult for the reduction reaction to occur. As a result, if sintered ore contains a lot of CaO, the reducibility of the sintered ore decreases. In the first embodiment, when the CaO concentration of the return ore is decreased, the amount of melt generated during sintering of the sintering raw material is increased. However, there is a concern that the reducibility (RI) may decrease due to the increased amount of melt generated.

[0029] In the sintered ore manufacturing method according to the second embodiment, the reducibility of the product sintered ore is measured, for example, every 4 hours on the blast furnace conveying line L2. The reducibility of the product sintered ore can be measured, for example, by a method described in JIS M8713 (iron ore-reducibility test method). The worker checks the CaO concentration of the return ore and the reducibility of the product sintered ore.

[0030] The operator takes action based on the measured CaO concentration of the return ore and the reducibility of the product sinter so that the CaO concentration becomes the target concentration. Specifically, when the CaO concentration of the return ore becomes lower than the target concentration, the operator takes the first action.

[0031] If the reducibility of the product sintered ore becomes lower than the operational reference value after the first action is carried out, the first action is reversed and a second action different from the first action is carried out. The operational standard value of reducibility can be set based on past production results. The operational standard value of reducibility can be, for example, 65%. The threshold value for implementing the second action can be 95% of the operational standard value.

[0032] According to the above embodiment, by taking an action to increase the amount of melt generated during sintering of the sintering raw material using the reducibility of the product sintered ore as an index in addition to the CaO concentration of the return ore, it is possible to improve the product yield while suppressing the decrease in reducibility.

[0033] <Third embodiment> Next, a method for producing sintered ore according to a third embodiment of the present invention will be described. The method for producing sintered ore according to this embodiment uses the productivity of sintered ore as an index in addition to the CaO concentration of return ore. As the first action, for example, by carrying out Action 1 of reducing the particle size of the CaO-containing raw material, it is possible that the permeability of the raw material packed bed deteriorates and the productivity decreases. In response to this, the productivity is monitored in order to suppress the decrease in productivity.

[0034] As shown in the following formula (1), productivity is determined by the sintering speed (thickness of the raw material packed bed (m) / time to complete sintering (days)) and the insertion density of the mixed raw materials (t / m 3 ) and the yield (proportion of +5mm sintered ore). Productivity (t / day / m 2 ) = sintering speed (m / day) x charging density (t / m 3 ) × yield (1)

[0035] If the productivity becomes lower than the operation standard value after the first action is implemented, the first action is reversed and a second action different from the first action is implemented. The productivity operation standard value can be set based on past production results. The productivity operation standard value is, for example, 30 t / day / m 2 The threshold for implementing an action different from the first action may be 95% of the operational baseline.

[0036] According to the above embodiment, by adding productivity as an index, it is possible to improve product yield while suppressing a decrease in productivity.

[0037] <Fourth embodiment> Next, a method for producing sintered ore according to a fourth embodiment of the present invention will be described. The method for producing sintered ore according to this embodiment uses the difference between the CaO concentration of the return ore and the CaO concentration of the product sintered ore as an index instead of the CaO concentration of the return ore. In the sinter ore manufacturing method of the present embodiment, the CaO concentration of the return ore is measured, for example, every 4 hours on the return ore transport line L1, and the CaO concentration of the product sinter ore is measured, for example, every 4 hours on the blast furnace transport line L2.

[0038] The operator performs action 1 (adjustment of particle size of CaO-containing raw material) described in the first embodiment based on the difference between the measured CaO concentration of the return ore and the CaO concentration of the finished sintered ore. Specifically, when the difference between the CaO concentration of the return ore and the CaO concentration of the finished sintered ore becomes high compared to the initial value, the operator performs action 1 so that the difference between the CaO concentration of the return ore and the CaO concentration of the finished sintered ore returns to the initial value. The threshold for implementing action 1 can be, for example, 140% of the initial value. If the initial value is 0.5% by mass, the threshold is 0.7% by mass.

[0039] When action 1 is implemented to reduce the particle size of the CaO-containing raw material, the CaO concentration in the upper layer increases and the CaO concentration in the middle and lower layers decreases. As a result, the difference in CaO concentration between the upper and lower layers becomes smaller, and the CaO concentration in the upper layer, which was recovered as return ore before action 1 is implemented, increases, increasing the amount of molten liquid generated, and some of it becomes product sintered ore. On the other hand, although the CaO concentration in the lower layer becomes lower than before action 1 is implemented, it is still higher than the threshold value and the reduction in yield is small. As a result, the total yield improves.

[0040] (Analysis of Onbelt samples) The blast furnace conveying line L2 and the return ore conveying line L1 are each provided with a component analyzer (not shown), and the product sinter and return ore (on-belt sample) on the belt conveyor are directly (while being conveyed) analyzed by the component analyzer. The component analyzer is, for example, a laser analyzer, an infrared analyzer, a neutron analyzer, a microwave analyzer, or the like. By continuously measuring the components of the on-belt sample and performing online analysis, it is possible to sequentially obtain component content data of the on-belt sample. Here, continuous measurement means a form in which an object to be analyzed is continuously irradiated with electromagnetic waves, neutrons, or the like, and measurement values ​​are continuously obtained. When the electromagnetic waves are a pulsed laser, etc., the time interval between pulses may be on the order of microseconds to seconds depending on the number of pulse repetitions. In addition, continuous measurements may be performed intermittently. There may be a finite rest period between consecutive measurements. Such a rest period can be appropriately selected so that the desired control is possible. From another point of view, continuous measurement may be a form in which the analysis target moving on a conveying means such as a belt conveyor or a pallet is measured in a non-contact manner without picking up (sampling) the analysis target from the conveying means.

[0041] For example, if the component contents of an on-belt sample are measured and analyzed using a LIBS (Laser Induced Breakdown Spectroscopy) analyzer, a laser with a peak output per pulse of 10 mJ to 150 mJ, a pulse width of 1 to 10 nm, and a repetition frequency of about 10 to 100 Hz is irradiated onto the on-belt sample to be analyzed using an optical system such as lenses and mirrors, and the resulting light emission is introduced into a spectrometer directly or using an optical fiber, etc., and the light emission spectrum is analyzed to identify the elements and quantify their concentrations. When the on-belt sample has a high moisture content or contains a large amount of fine powder, a pretreatment is performed to remove surface deposits and / or moisture from the on-belt sample by irradiating the on-belt sample with a laser beam separate from that for analysis, and then at least a part of the area irradiated with the laser beam in the pretreatment is irradiated with a laser beam for analysis to perform a component analysis by laser-induced breakdown spectroscopy analysis, thereby obtaining component content data for the on-belt sample. This pretreatment is a process to remove surface deposits and moisture from on-belt sample particles by so-called laser ablation.

[0042] The LIBS analysis device is equipped with the components necessary for measurement and analysis, such as a pre-processing laser light source and an analytical laser light source arranged in sequence in the conveying direction, a spectrometer (e.g., AvanSpec-ULS2048CL-EVO manufactured by Avantes) that detects the wavelengths and intensity of light contained in the emission caused by the analytical laser light, a processing unit, and a control device.The processing unit acquires measurement data regarding the emission generated from the on-belt sample (data regarding the emission intensity at each wavelength) output from the spectrometer, and analyzes the component composition of the on-belt sample using LIBS based on this measurement data.

[0043] It is also preferable to measure the position of the analysis portion to be irradiated with the analytical laser light (e.g., the height from the conveying surface of a conveying facility such as a belt conveyor) and irradiate the analysis portion with the analytical laser light based on the measured position information. Methods for measuring the position include laser ranging and acoustic ranging, but in the case of a belt conveyor, laser ranging is more preferable because acoustic disturbances are large. It becomes possible to identify the analysis position of the on-belt sample to be analyzed, and it becomes possible to more reliably focus the analytical laser light on the analysis portion (surface) of the on-belt sample particle to be analyzed. As a result, it becomes possible to measure the component content of the on-belt sample with even greater accuracy.

[0044] According to the above embodiment, by using the difference between the CaO concentration of the return ore and the CaO concentration of the product sintered ore as an index, it is possible to eliminate the influence of fluctuations in the CaO concentration of the raw material blend and to more directly correct changes in yield, as compared with a method that uses only the CaO concentration of the return ore as an index.

[0045] In this embodiment, the CaO concentration of the finished sintered ore on the blast furnace conveying line L2 is used as the CaO concentration of the finished sintered ore. However, this is not limited to this, and the difference between the CaO concentration of the return ore and the CaO concentration of the finished sintered ore may be calculated using the CaO concentration of the finished sintered ore estimated from the blending ratio of the blended raw materials, or a target value set when determining the blending ratio of the blended raw materials. Furthermore, the method for measuring the CaO concentration in the product sintered ore and the CaO concentration in the return ore is not limited to the above-mentioned method, and a component analyzer capable of online analysis of the on-belt product sintered ore and return ore may be used. EXAMPLES

[0046] Example 1 Next, an embodiment of the present invention will be described. In Example 1, a blended raw material containing iron ore, CaO-containing raw material, auxiliary raw material, and coagulant was charged into a sintering machine, and the charged blended raw material was sintered to produce a sintered cake. In the return ore conveying line L1, return ore was collected every 4 hours, and the CaO concentration was measured by the method described in JIS M8205 (iron ore-fluorescent X-ray analysis method). The CaO concentration of the return ore was 9.5% by mass, which was set as the target concentration, and the threshold concentration was set to 9.2% by mass. The product yield was 77.8% by mass.

[0047] In the production of sintered ore, the blending ratio of the blended raw materials may be changed depending on the type (brand) of iron ore. When the blending ratio of the blended raw materials was changed in this example, the CaO concentration of the return ore became less than the threshold concentration of 9.2 mass%, and the product yield also decreased to 77.5%. In response to this, the amount of CaO-containing raw materials (proportion of new raw materials (incl. total) not including return ore or carbonaceous materials) was increased from 11.0% by mass to 11.4% by mass. This action increased the CaO concentration in the return ore to 9.5% by mass, the same as before the change in the blending ratio. As a result, the yield, which had been on a downward trend after the change in the blending ratio, recovered to 77.8%, the same as before the change.

[0048] Example 2 In Example 2, similarly to Example 1, return ore was collected every 4 hours on the return ore transport line L1, and the CaO concentration was measured by fluorescent X-ray analysis. The CaO concentration of the return ore was 9.8% by mass, which was set as the target concentration, and the threshold concentration was set to 9.4% by mass. In addition, product sinter was collected every 4 hours on the blast furnace transport line L2, and the reducibility of the product sinter was measured. The operational standard value of the reducibility of the product sinter was set to 65%, and the threshold value was set to 62%. The product yield was 77.9% by mass.

[0049] When the blending ratio of the raw materials was changed, the CaO concentration of the return fines decreased to less than 9.4 mass%, which is below the threshold concentration, and the product yield also decreased to 77.6 mass%. In response to this, an action was taken to increase the amount of CaO-containing raw materials (ratio to new raw materials (incl. number) not including return ore or carbonaceous materials) from 11.5% by mass to 11.9% by mass. This action increased the CaO concentration of the return ore to 9.8% by mass, the same as before the blending change. However, the reducibility of the finished sintered ore began to decrease, falling below the threshold of 62%, so the amount of CaO-containing raw materials was returned to the original amount (11.5% by mass) and the particle size of the CaO-containing raw materials was reduced from 4 mm to 3.5 mm. This action increased the CaO concentration of the return ore to 9.8% by mass, the same as before the blending change, without causing any particular deterioration in permeability. As a result, the yield, which had been on a downward trend after the blending ratio change, recovered to 77.9% by mass, the same as before the change.

[0050] Example 3 In Example 3, similarly to Example 1, return ore was collected every 4 hours on the return ore transport line L1, and the CaO concentration was measured by fluorescent X-ray analysis. The CaO concentration of the return ore was 9.7% by mass, which was set as the target concentration, and the threshold concentration was set as 9.3% by mass. In addition, product sintered ore was collected every 4 hours on the blast furnace transport line L2, and the productivity of the product sintered ore was measured. The operational standard value for the productivity of the product sintered ore was 30 t / day / m 2 The threshold is set at 29 t / day / m 2 The product yield was 77.9% by mass.

[0051] When the blending ratio of the raw materials was changed, the CaO concentration in the return ore decreased to less than 9.3 mass%, which is below the threshold concentration, and the product yield also decreased to 77.5 mass%. In response to this, an action was taken to reduce the particle size of the CaO-containing raw material from 3.5 mm to 3.0 mm. This action increased the CaO concentration in the return ore to 9.7 mass%, the same as before the blending change. However, the productivity of the finished sintered ore began to decline, and the threshold value of 29 / day / m was exceeded. 2Since the particle size of the CaO-containing raw material was lower than the original value, the particle size of the CaO-containing raw material was returned to the original (3.5 mm) and the type of CaO-containing raw material was changed. Specifically, the CaO-containing raw material ratio of steelmaking slag:limestone = 20% by mass:80% by mass was changed to steelmaking slag:limestone = 0% by mass:100% by mass. This action increased the CaO concentration of the return ore to 9.7% by mass, the same as before the mix change. As a result, the yield, which had been on a downward trend after the mix ratio change, recovered to 77.9% by mass, the same as before the change.

[0052] Example 4 In Example 4, return ore was collected every 4 hours on the return ore transport line L1, and product sintered ore was collected every 4 hours on the blast furnace transport line L2, and the CaO concentration was measured by fluorescent X-ray analysis. The initial value of the difference between the CaO concentration of the return ore and the CaO concentration of the product sintered ore was 0.5 mass%, and the product yield was 77.8 mass%.

[0053] When the blending ratio of the raw materials was changed, the difference between the CaO concentration of the return ore and the CaO concentration of the sintered ore increased from 0.5 mass% to the threshold value of 0.7 mass%, and the product yield also decreased to 77.6 mass%. In response to this, the particle size of the CaO-containing raw materials was reduced from 4 mm to 3.5 mm. This action reduced the difference between the CaO concentration of the return ore and the CaO concentration of the finished sintered ore to 0.5 mass%, the same as before the mix change, without causing any particular deterioration in aeration. As a result, the yield, which had been on a downward trend after the mix ratio change, rose to 77.9 mass%, higher than before the change.

[0054] Although the present invention has been described in detail above with reference to the drawings, it is of course not limited to the above-mentioned configurations and various modifications can be made without departing from the gist of the present invention. [Explanation of symbols]

[0055] L1...Return ore conveyance line, L2...Blast furnace conveyance line, S1...Raw material blending process, S2...Pelletization process, S3...Sintering process, S4...Sizing process.

Claims

1. A blended raw material including iron ore, a CaO-containing raw material, and a coagulant is charged into a sintering machine; Sintering the charged blended raw materials to produce a sintered cake; In the method for producing sintered ore, the sintered cake is sieved into product sintered ore and return ore by a classification device, Measuring the CaO concentration of the return fines; and an action implementation step of implementing at least one of an action of adjusting the blending amount of the CaO-containing raw material, an action of adjusting the particle size of the CaO-containing raw material, and an action of changing the type of the CaO-containing raw material, when the measured CaO concentration in the return ore becomes a threshold concentration lower than a target concentration.

2. A step of measuring the reducibility of the product sintered ore, The method for producing sintered ore according to claim 1 , further comprising the step of: implementing an action different from the action implemented in the action implementation step when the reducibility falls below an operational reference value after the action implementation step.

3. A step of calculating the productivity of the product sintered ore, The method for producing sintered ore according to claim 1 or 2, further comprising the step of: implementing an action different from the action implemented in the action implementation step when the productivity falls below an operational reference value after the action implementation step.

4. A blended raw material including iron ore, a CaO-containing raw material, and a coagulant is charged into a sintering machine; Sintering the charged blended raw materials to produce a sintered cake; In the method for producing sintered ore, the sintered cake is sieved into product sintered ore and return ore by a classification device, Measuring the CaO concentration of the return fines; Measuring the CaO concentration of the product sinter; and an action implementation step of implementing an action to adjust the particle size of the CaO-containing raw material when a difference between the CaO concentration of the product sintered ore and the CaO concentration of the return ore becomes a threshold value lower than an initial value.

Images