TWI842462B - Sintered ore production method - Google Patents

Abstract

The method for producing sintered ore of the present invention comprises the following steps: Loading the formulated raw material granules of the lower system into the sintering machine (100) to form a lower raw material filling layer (10); Loading the formulated raw material granules of the upper system onto the lower raw material filling layer to form an upper raw material filling layer (20); and Ignite the surface of the lower raw material filling layer and the surface of the upper raw material filling layer respectively, and introduce oxygen-containing gas into the lower raw material filling layer and the upper raw material filling layer through the lower suction (6) under atmospheric pressure; wherein, After the ignition of the upper raw material filling layer is completed, at least a portion of the gas sucked from the surface side of the upper raw material filling layer is made into oxygen-enriched gas with an oxygen concentration of 26 volume % or more and 46 volume % or less; and, in the length direction of the sintering machine, the middle position of the section from the outlet (X) of the upper ignition furnace (2C) to the ore discharge end (Y) is made the middle position (Z), and the section from the outlet (X) of the upper ignition furnace to the middle position (Z) is made the front half section. At this time, the area to which the oxygen-enriched gas is supplied is the area including a part of the front half section.

Description

Sintered ore production method

The present invention relates to a method for producing sintered ore for blast furnace raw material, and more particularly to a two-stage charging and two-stage ignition sintering method.

Sintered ore, which is the main raw material for blast furnace milling, is usually produced in the following manner. First, iron raw materials such as iron ore (powder) as raw materials for sintered ore production, iron-containing impurities such as rust scale/ironmaking dust, auxiliary materials containing CaO such as limestone, returned ore, carbon materials (agglomerates), etc. are mixed (blended) at a predetermined ratio. Among them, the carbon materials can be used as fuel to sinter (agglomerate) the sintered ore with combustion heat. In order to adjust the particle size distribution of the mixed raw materials (formulated raw materials), they are granulated (hereinafter simply referred to as granulation) to produce quasi-particles composed of aggregates of primary particles of the raw materials. Next, the granulated formula raw material (formulated raw material granules) is loaded from the feed hopper onto the tray (sintering tray) of the suction-type Dwight-Lloyd (DL) sintering machine to form a filling layer of the formula raw material (hereinafter referred to as the raw material filling layer or raw material layer). The carbon material in the raw material filling layer is ignited from the upper part (surface) of the formed raw material filling layer using an ignition furnace (igniter). Then, while the tray is continuously moved, air is sucked from under the tray. By suction, oxygen in the air is supplied to the raw material filling layer, causing the combustion of the carbon material in the raw material filling layer to proceed from the upper part to the lower part, and the raw material filling layer is sintered sequentially by the combustion heat of the carbon material. The sintered part (sintered block) obtained by sintering is sized by crushing into a predetermined particle size, screening, etc., and becomes a sintered ore as a raw material for a blast furnace.

Regarding the above-mentioned method for producing sintered ore by a DL-type sintering machine, document 1 (Japanese Patent Laid-Open No. 47-26304) proposes a multi-stage loading multi-stage ignition sintering method, which forms a raw material filling layer and ignites it in multiple stages of two or more stages. As an example of the multi-stage loading multi-stage ignition sintering method, the two-stage loading two-stage ignition sintering method (hereinafter also referred to as the two-stage loading two-stage ignition method) is the following method: the formulated raw material granules are sequentially loaded twice in the layer height direction of the sintering machine to form two stages of raw material filling layers (upper raw material filling layer and lower raw material filling layer), and ignition is performed on the surface of each raw material filling layer, and air is sucked from the bottom, so that the sintering reaction of each layer is carried out simultaneously and in parallel.

In the two-stage loading and two-stage ignition sintering method, the raw material filling layer is divided into two stages, and sintering is performed in the two stages simultaneously, so the production volume is almost doubled. In addition, since the exhaust gas used for sintering the upper raw material filling layer (hereinafter referred to as the upper stage) is reused in the sintering of the lower raw material filling layer (hereinafter referred to as the lower stage) by suction from the bottom, there is an advantage that the exhaust gas volume is reduced (halved). On the other hand, the gas (exhaust gas) whose oxygen partial pressure has been reduced by sintering the upper stage is used for sintering the lower stage, and sintering is performed under low oxygen partial pressure in the lower stage. Therefore, the combustion of the carbon in the lower layer will be incomplete, resulting in insufficient heat required for sintering, which will hinder the sintering reaction and cause the strength of the sintered ore in the lower layer to decrease.

In view of the above, some people have proposed to carry out enrichment and oxidation of the suction gas.

Document 2 (Japanese Patent Publication No. 6-43618) discloses a technique of measuring the oxygen concentration in the main exhaust gas sucked from the entire sintering machine, and adjusting the oxygen concentration in the gas sucked from the surface side of the raw material layer (hereinafter referred to as the suction gas) so that the oxygen concentration reaches 6% or more. In the embodiment, the oxygen concentration of the suction gas was verified to be in the range of 21% to 25%, and the improvement effect of the strength brought by the rich oxygen was confirmed.

Furthermore, document 3 (Japanese Patent Publication No. 2000-17343) discloses a method for supplying oxygen-containing gas by using differential pressure in a two-stage loading and two-stage ignition sintering method. It states that the oxygen concentration of the supplied oxygen-containing gas is preferably 12-40%.

Furthermore, the technology disclosed in Document 4 (Japanese Patent Publication No. 2015-157980) is that in the loading layer (raw material filling layer) formed by the single-stage loading, an ignition furnace is used to ignite the upper surface thereof, and in addition, a burner is used to ignite from the side of the middle section at the upstream end of the loading layer, thereby realizing a two-stage ignition sintering method. Moreover, it is proposed to eliminate the insufficient combustion of the lower layer by enriching the oxygen of the suction gas on the downstream side of the ignition furnace. In the embodiment, the oxygen concentration of the suction gas is verified in the range of 21% to 46%, and it is confirmed that the productivity is improved and the strength is improved by enriching the oxygen.

However, in the verification of the two-stage loading and two-stage ignition method of document 2, the region where the oxygen concentration of the pumped gas is greater than 25% was not studied. In addition, the technology of document 3 supplies oxygen-containing gas by differential pressure, and does not teach the two-stage loading and two-stage ignition method in which the pumping is performed without differential pressure.

Furthermore, document 4 only discloses a single-stage loading method, which is to load raw materials at one time to form a single-stage loading layer, and discloses the verification results of applying the two-stage ignition technology to the single-stage loading method, but does not disclose the verification results of the two-stage loading and two-stage ignition method. When the formulated raw material granules are filled into the sintering machine tray, they are loaded through the loading chute accompanied by particle size segregation. The small particles are mostly arranged on the upper layer side of the raw material layer, and the large particles are mostly arranged on the lower layer side of the raw material layer. As a result, for example, the particle size of the carbon material composed of fine particles is still very small after the granulation process, and is mostly distributed on the upper layer side of the raw material layer. Compared to the lower layer of the two-stage loading method, which forms each loading layer in two steps, the lower layer of the single-stage loading method has a coarser particle size and a lower carbon material concentration. It is generally known that due to the particle size segregation in the layer thickness (layer height) direction and the difference in carbon material distribution, the sintering conditions such as the temperature and air permeability in the layer during sintering will change, and will affect the yield and productivity.

In addition, in the technology of document 4, the ignition of the lower layer is performed by applying a flame from the side in the middle section of the upstream end of the loading layer. Since the loading layer on the pallet moves toward the discharge end side together with the pallet, the ignition time will inevitably be shortened compared to the ignition performed by the ignition furnace in the two-stage loading and two-stage ignition method. In addition, the granulated material of the formulated raw materials supplied from the feed hopper will enter between the lower layer and the flame during the ignition. Therefore, in actual mechanical operation, the input heat of the lower layer will be reduced, and the sintering reaction may not be fully promoted. Moreover, since the flame is blown toward the inclined surface of the upstream end of the loading layer, it can be inferred that it will also affect the particle size segregation and the like. Based on the above, the inventors believe that based on the knowledge of Document 4, it is impossible to foresee the effect of enriching the oxygen of the suction gas in the two-stage loading and two-stage ignition method.

In view of the above problems, the inventors of this case have tried the following research: In the two-stage loading and two-stage ignition method, the oxygen concentration of the gas supplied to the lower and upper layers through the bottom suction under atmospheric pressure is set to a high oxygen concentration area greater than 25%, and the impact on productivity (productivity) at this time.

The object of the present invention is to provide a method for producing sintered ore, which can improve productivity in a two-stage loading and two-stage ignition method. [1] A method for producing sintered ore, comprising the following steps: Loading a granulated material of a lower system with a formulated raw material into a sintering machine to form a lower raw material filling layer; Loading a granulated material of a upper system with a formulated raw material onto the lower raw material filling layer to form an upper raw material filling layer; and Ignite the surface of the lower raw material filling layer and the surface of the upper raw material filling layer respectively, and introduce oxygen-containing gas into the lower raw material filling layer and the upper raw material filling layer by suction under atmospheric pressure; wherein, After the ignition of the upper raw material filling layer is completed, at least a portion of the gas sucked from the surface side of the upper raw material filling layer is made to be an oxygen-rich gas with an oxygen concentration of 26 volume % or more and 46 volume % or less; and, In the longitudinal direction of the sintering machine, the middle position of the section from the outlet of the upper ignition furnace to the end of the ore discharge is the middle position, and the section from the outlet of the upper ignition furnace to the middle position is the front half section. At this time, the area to which the oxygen-enriched gas is supplied is the area including a part of the front half section.

[2] A method for producing sintered ore as described in [1], wherein a portion of the aforementioned front half section is an upstream side portion of the aforementioned front half section.

[3] A method for producing sintered ore as described in [1], wherein the section from the aforementioned middle position to the aforementioned ore discharge end in the longitudinal direction of the sintering machine is defined as the second half section, and in this case, the area to which the oxygen-enriched gas is supplied includes at least a portion corresponding to the aforementioned first half section, and the portion corresponding to the aforementioned first half section is longer than the portion corresponding to the aforementioned second half section.

[4] The method for producing sintered ore as described in [1], wherein the area to which the oxygen-rich gas is supplied is the first half section or a part of the first half section.

[5] A method for producing sintered ore as described in any one of [1] to [4], wherein the raw material for the lower raw material filling layer is a highly combustible carbon material having a combustion rate of 0.0022 (1/sec) or more at 700°C.

[6] A method for producing sintered ore as described in [5], wherein the highly combustible carbon material comprises char obtained by dry distillation of coal having a Roga index of less than 10.

[7] A method for producing sintered ore as described in [5], wherein the highly combustible carbon material comprises palm kernel shell charcoal.

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 sucked from the upper stage layer surface side is set to: oxygen-rich gas with an oxygen concentration of 26 volume % (vol%) or more and 46 volume % (vol%) or less, and the area supplied with the oxygen-rich gas is set to: an area including a portion of the front half of the area from the outlet of the upper stage ignition furnace to the end of the ore discharge, thereby improving productivity.

Form for implementing the invention Below, referring to FIG. 1, a two-stage loading and two-stage ignition sintering method as an implementation form of the present invention is described.

FIG1 is a schematic diagram showing the steps of sintering ore production by the two-stage loading and two-stage ignition sintering method. The two-stage loading and two-stage ignition sintering method is to load the granulated formula raw materials in two stages to form an upper raw material filling layer (hereinafter referred to as the upper layer) and a lower raw material filling layer (hereinafter referred to as the lower layer), and sintering is performed by igniting the upper layer and the lower layer respectively.

First, an example of a two-stage loading and two-stage ignition sintering method as a known technique will be described.

In the example shown in FIG. 1 (excluding the oxygen-enriched gas supply device 7), the upper stage formula raw materials for forming the upper stage layer 20 and the lower stage formula raw materials for forming the lower stage layer 10 are prepared in different systems (two systems) and loaded onto the pallet (not shown) of the sintering machine 100 by different systems. Specifically, the lower stage raw materials are stored in each raw material tank (1D ₁ ~1D _X ) of the lower stage raw material tank group 1D, and the required types and amounts of raw materials are cut out at a predetermined ratio for mixing. The mixed lower stage raw materials (lower stage formula raw materials) are put into the lower stage drum mixer 1A for mixing, and then water is added to be granulated. Furthermore, the raw materials for the upper stage are stored in each raw material tank (2D ₁ ~2D _y ) of the upper stage raw material tank group 2D, and the required types and quantities of raw materials are cut out at a predetermined ratio for mixing. After mixing, the raw materials for the upper stage (prescription raw materials for the upper stage) are put into the upper stage drum mixer 2A for mixing, and then water is added to be granulated. In addition, the carbon materials for the raw materials for the lower stage and the upper stage can use coke crumbs, smokeless coal, etc. For example, when using coke crumbs and smokeless coal as raw materials, they can be stored in different raw material tanks respectively, or they can be stored in one raw material tank in a state where coke crumbs and smokeless coal are mixed at a predetermined ratio.

The granulated lower stage formula raw material (lower stage formula raw material granulated material) is loaded from the lower stage feed hopper 1B onto the pallet covered with floor laid mineral to form the lower stage layer 10 (lower stage raw material filling layer). By moving the pallet in the pallet travel direction 5, the lower stage layer 10 moves to the bottom of the lower stage ignition furnace 1C, and the carbonaceous material on the surface of the lower stage layer 10 is ignited by the lower stage ignition furnace 1C. After ignition, the sintering of the lower stage layer 10 begins by the lower suction 6 that sucks air from below through the bellows (not shown) under the pallet. By continuing the lower suction 6, the sintering of the lower stage layer 10 proceeds downward to form the lower stage combustion zone 10A.

When the lower stage layer 10 that has started sintering moves to the bottom of the upper stage feed hopper 2B, the granulated upper stage formula raw materials (upper stage formula raw material granules) will be loaded from the upper stage feed hopper 2B onto the ignited lower stage layer 10 to form the upper stage layer 20 (upper stage raw material filling layer). By moving the pallet in the pallet travel direction 5, the upper stage layer 20 will move to the bottom of the upper stage ignition furnace 2C, and the carbonaceous materials on the surface of the upper stage layer 20 will be ignited by the upper stage ignition furnace 2C. After ignition, the sintering of the upper stage layer 20 will begin by the lower suction 6. By continuing the lower suction 6, the sintering of the upper stage layer 20 will proceed downward to form the upper stage layer combustion zone 20A.

As described above, in the two-stage loading and two-stage ignition method, the lower stage layer 10 is formed in the sintering machine 100, and after the surface of the lower stage layer 10 is ignited, the upper stage layer 20 is formed on the ignited lower stage layer 10 and the surface of the upper stage layer 20 is ignited. In addition, when the ignition of the lower stage layer 10 starts, the lower suction 6 is started so that the sintering of the lower stage layer 10 proceeds in the layer thickness direction. By the subsequent further lower suction 6, after the ignition of the upper stage layer 20, the lower stage layer combustion zone 10A of the lower stage layer 10 and the upper stage layer combustion zone 20A of the upper stage layer 20 will be simultaneously parallel, and the sintering will proceed and descend. When the lower layer combustion zone 10A and the upper layer combustion zone 20A reach the bottom of each layer, the sintering caused by the combustion of the carbon material will be completed, and the lower layer 10 and the upper layer 20 will become the sintering part 3. Finally, the sintering part 3 after sintering is completed will be discharged from the support plate (ore discharge end).

The manufacturing method of sintered ore of the present invention includes the following steps: Loading the formulated raw material granules of the lower system into the sintering machine to form a lower raw material filling layer; Loading the formulated raw material granules of the upper system on the lower raw material filling layer to form an upper raw material filling layer; and Ignite the surface of the lower raw material filling layer and the surface of the upper raw material filling layer respectively, and introduce oxygen-containing gas into the lower raw material filling layer and the upper raw material filling layer by suction under atmospheric pressure; wherein, After the ignition of the upper raw material filling layer is completed, at least a portion of the gas sucked from the surface side of the upper raw material filling layer is made into oxygen-enriched gas with an oxygen concentration of 26 vol% or more and 46 vol% or less; and, in the length direction of the sintering machine, the middle position of the section from the outlet of the upper ignition furnace to the end of the ore discharge is made into the middle position, and the section from the outlet of the upper ignition furnace to the middle position is made into the front half section. At this time, the area (oxygen-enriched area) for supplying oxygen-enriched gas is set as an area including a part of the front half section. As shown in FIG. 1, the sintering machine 100 used in the present invention has not only the structure of the sintering machine used in the above-mentioned known technology, but also an oxygen-enriched gas supply device 7. The oxygen-enriched gas supply device 7 has an exhaust hood 8 and a gas pipe 9 that can supply oxygen-enriched gas to the exhaust hood 8, and the oxygen-enriched gas supply device 7 can supply oxygen-enriched gas with an oxygen concentration of more than 26 vol% and less than 46 vol% above (surface side) the upper raw material filling layer. The supplied oxygen-enriched gas will be guided into the raw material filling layer by the lower suction 6 of the wind box to cause the sintering reaction to proceed, and will be recovered as exhaust gas by the wind box. In addition, in the area outside the oxygen-enriched area, the atmosphere above the surface of the upper raw material filling layer will be introduced into the upper raw material filling layer and the lower raw material filling layer from the surface side of the upper raw material filling layer due to the lower suction.

In addition, it is also possible to spray oxygen from the gas pipe 9 toward the surface of the upper raw material filling layer without providing the exhaust hood 8, and to suck it together with the atmosphere. In this case, the supply amount of oxygen sprayed from the gas pipe 9 is adjusted in such a way 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 oxygen concentration range of the oxygen-enriched gas is set to 26 vol% or more and 46 vol% or less based on the results of the embodiment described later. In addition, in order to make the carbon material burn quickly in the lower layer and not supply unnecessary oxygen, the oxygen concentration range is preferably 36 vol% or more and 46 vol% or less.

In the following, the range (area) for supplying oxygen-enriched gas is explained by setting the middle position of the section (whole section) from X behind the outlet of the upper ignition furnace to the end Y of the ore discharge as the middle position Z, the section from X behind the outlet of the upper ignition furnace to the middle position Z as the front half section, and the section from the middle position Z to the end Y of the ore discharge as the rear half section. Here, X behind the outlet of the upper ignition furnace indicates the position on the most upstream side where the oxygen-enriched gas supply device 7 can be set. In the direction 5 of the travel of the pallet of the sintering machine 100, the position for setting the oxygen-enriched gas supply device 7, that is, the area (oxygen-enriched area) where oxygen-enriched gas is supplied on the surface side of the sintering layer and sucked from below, is set on the downstream side of the upper ignition furnace 2C. In FIG1 , a safety interval is provided between the upper ignition furnace 2C and the oxygen-enriched gas supply device 7. In the case where a safety interval must be provided, the position X after the outlet of the upper ignition furnace is: the upstream end of the oxygen-enriched gas supply device 7 provided with only the safety interval vacated, i.e., position X1. If there is no safety problem, the upper ignition furnace 2C and the oxygen-enriched gas supply device 7 can be provided continuously. In this case, the position X after the outlet of the upper ignition furnace is: the downstream end of the upper ignition furnace, i.e., position X2. The oxygen-enriched gas supply device 7 is preferably configured to continuously supply oxygen-enriched gas in the direction 5 of the pallet travel. In addition, the upper ignition furnace 2C and the oxygen-enriched gas supply device 7 may be continuously installed, and only on the upstream side of the oxygen-enriched gas supply device 7 (on the upper ignition furnace 2C side) in the direction of travel of the pallet, the oxygen concentration may be set to a lower level (for example, 26 vol% to 35 vol%) within the range of 26 vol% to 46 vol% to ensure safety.

The section where the oxygen-enriched gas supply device 7 is provided, that is, the section where the oxygen-enriched gas is supplied to the surface of the raw material filling layer (hereinafter also referred to as the oxidation-enriched section), is a section including a part of the front half section (the section from X after the outlet of the upper ignition furnace to the middle position Z) in the length direction of the sintering machine 100. Here, a part of the front half section is preferably the upstream side part of the front half section (for example, for the front half section in the direction of the movement of the pallet, when the position of the upstream end is represented as 0 and the position of the downstream end is represented as 0.5, it corresponds to the part from 0 to 0.30). In addition, the oxidation-enriched section should at least include the part corresponding to the front half section, and the part corresponding to the front half section should be longer than the part corresponding to the rear half section (the section from the middle position Z to the end of the ore discharge Y). Moreover, the oxidation-enriched section can also be the entire front half section and a part of the rear half section. Furthermore, the oxidation-rich region is preferably the first half section or a part of the first half section.

The reason why the oxygen-rich zone can be specifically designated in the above manner is as follows: in the embodiment described later, setting the supply range of the oxygen-rich gas to the range from the outlet X of the upper ignition furnace to the middle position Z (the first half section) or a part thereof (a part of the first half section) is more effective than setting it to the range from the middle position Z to the end Y of the ore discharge (the second half section). Therefore, if the oxygen-rich zone is a region including the first half section or a region including a part of the first half section, the effect can be obtained. Here, when the oxygen-rich zone is set as a part of the entire section, the reason why the oxygen-rich gas in the first half section is more effective than the oxygen-rich gas in the second half section can be inferred as follows.

The implementation of rich oxidation is to improve the situation where the combustion of the carbon material in the lower layer becomes inactive (incomplete) due to insufficient oxygen; in the section where rich oxidation is implemented, the combustion of the carbon material becomes active and the temperature inside the sintering machine can be appropriately maintained at a high temperature. When rich oxidation is implemented in the first half section, by maintaining the high temperature in the first half section, the temperature inside the sintering machine can be maintained at a high temperature and the sintering reaction can proceed even if rich oxidation is not implemented in the second half section. On the other hand, when rich oxidation is not implemented in the first half section but implemented in the second half section, the combustion of the carbon material becomes inactive in the first half section and the temperature inside the sintering machine decreases. Therefore, even if rich oxidation is implemented in the subsequent second half section, it is still difficult to fully restore the temperature inside the sintering machine. Therefore, it can be considered that rich oxidation in the first half section (or the upstream part of the first half section) will be very effective.

In addition, in the sintering machine, when the formula raw materials are loaded, there will be particle size segregation, and the concentration of carbon materials with finer particle sizes than the main raw materials such as iron ore will increase above the raw materials. Therefore, in terms of the two-stage loading and two-stage ignition method, the amount of carbon materials in the upper part of the lower layer and the upper layer is more than that in the lower part. The more carbon materials there are, the more oxygen is required for combustion, so it is advisable to carry out enriched oxidation in the first half of the combustion zone corresponding to the upper part of the layer. When the enriched oxidation zone is limited in order to suppress oxygen costs, etc., it is advisable to set it as a zone that includes at least a part of the first half of the zone based on the above reasons.

Furthermore, the formulas of the upper-stage formula raw materials and the lower-stage formula raw materials may be the same or different. Furthermore, if the formulas are the same, the upper-stage formula raw materials and the lower-stage formula raw materials may be prepared in the same system instead of in different systems (two systems).

Here, as shown in the embodiments described below, in the method for producing sintered ore of the present invention, part or all of the carbon material used as the raw material for the lower stage is preferably a high-combustibility carbon material. As shown in Table 1, the so-called high-combustibility carbon material is a carbon material (agglomerated material) having a combustion rate (combustion rate (700°C)) of 0.0022 (1/second) or more at 700°C, and carbonized coal (coal char), palm shell charcoal (PKS char), carbonized charcoal produced by dry distillation of wood, etc. meet this condition. In addition, the combustion start temperature of the high-combustibility carbon material is lower than the combustion start temperature of coke and smokeless coal. [Table 1]

Palm shell charcoal (PKS charcoal) is a solid carbide produced by heat treatment (dry distillation) of palm kernel shell. In addition, carbonized coal is a sintering carbon material (charcoal) produced by dry distilling low-fluidity coal with a Roga index of less than 10 as raw coal. Carbonized coal is produced by dry distilling coal (including mixed coal) as a raw material in a thermal decomposition furnace (such as a rotary kiln). By using low-fluidity coal with a Roga index of less than 10 as raw coal, highly combustible carbonized coal can be produced. In addition, the so-called fluidity of coal is due to the property of low molecular weight during heating. Low fluidity coal is a type of coal that has the property of not being easily decomposed during heating.

The Roga index is calculated by the Roga test method specified in JIS-M8801 (2008). The Roga test method is described below.

First, 1g of inferior coal with a particle size of less than 200µm and 5g of standard smokeless coal are thoroughly mixed in a crucible. Standard smokeless coal is smokeless coal with an ash content (water-free basis) of less than 4.0%, a volatile matter (water-free basis) of more than 5.0% and less than 6.5%, and a particle size of more than 300µm and less than 400µm. Then, a fixed load (59N) is applied to the inferior coal and standard smokeless coal in the crucible for a predetermined time (at least 30 seconds) using a heat-resistant steel weight.

Next, the crucible is placed in an electric furnace with the furnace temperature set at 850±10℃, and the inferior coal and standard smokeless coal are heated (dry distilled) for 15 minutes. Then, the heated crucible is placed on a heat-resistant plate and cooled for 45 minutes, and the mass of the crucible contents (hereinafter sometimes referred to as dry distillates) is measured, and the mass of the dry distillates on the sieve is measured using a 1mm round hole plate sieve.

Next, the crucible contents (dry pulp) are placed in the drum, which is rotated at a predetermined rotation speed (50 rpm) for 5 minutes to break the dry pulp. The drum has an inner diameter of 200 mm, a depth of 70 mm, and two blades of 70 mm in length and 30 mm in width are symmetrically arranged on the inner wall of the drum.

Next, the dried extract after the decomposition treatment was screened using a 1 mm round hole plate screen, and the mass of the sieved material was measured. The above decomposition treatment was repeated three times, and the Rockad index was calculated according to the following formula (1). In formula (1), RI is the Rockad index. _m1 is the total mass [g] of the crucible contents (dried extract) after decomposition, _m2 is the mass [g] of the dried extract on the sieve before the first decomposition treatment, _m3 is the mass [g] of the dried extract on the sieve after the first decomposition treatment. _m4 is the mass [g] of the dried extract on the sieve after the second decomposition treatment, and _m5 is the mass [g] of the dried extract on the sieve after the third decomposition treatment. ···(1)

The combustion rate (700°C) shown in Table 1 is calculated as follows.

First, 10 mg of the sample to be measured is placed on the thermobalance in the device, and the inside of the device is purged with nitrogen. Then, the sample is heated at a rate of 100°C/min while nitrogen is circulated at 200 ml/min. When the sample temperature reaches 700°C, the circulating gas is immediately switched from nitrogen to air at 200 ml/min, and the weight loss is measured to obtain the reaction time t (the time after the circulating gas is switched from nitrogen to air) and the reaction rate Xr (Xr = [weight loss at each time - unburned weight at the end of the measurement] / [initial weight of the sample - unburned weight at the end of the measurement]). Furthermore, the reaction rate dXr/dt of each reaction rate was calculated, and the average value of Xr from 0 to 0.5 was calculated, and the average value was used as the combustion rate at 700°C.

In the two-stage loading and two-stage ignition method, the oxygen concentration of the gas supplied to the lower layer will be lower than the oxygen concentration of the gas supplied to the upper layer. Since the combustion starting temperature of the highly combustible carbon material is low, it will still burn under the low temperature condition caused by the low oxygen environment, and poor combustion (the situation where the carbon material is not burned and remains) can be suppressed. Here, if a highly combustible carbon material is used in the lower layer and combined with rich oxygen as shown in the embodiment described later, the productivity will be greatly improved. The following reasons can be considered for this effect. As shown in Table 1, the combustion speed of highly combustible carbon material is fast. However, even if high-combustibility carbon materials are used, poor combustion can be suppressed without implementing rich oxidation, but the combustion rate is not fast enough and is not active due to insufficient oxygen, making it difficult to maintain an appropriately high temperature inside the sintering machine. On the other hand, if rich oxidation is implemented, the combustion rate of high-combustibility carbon materials can be adjusted by the oxygen concentration. By implementing rich oxidation, the sintering rate can be increased to make the carbon material burn actively, and the temperature inside the sintering machine can be maintained at an appropriately high temperature. In addition, the combustion rate of high-combustibility carbon materials (700°C) is very fast, so if high-combustibility carbon materials are used in the sintering step, the time until all the carbon materials are burned will be shortened, and the time until sintering is completed will also be shortened. Since the time until sintering is completed is shortened, the amount of sintered ore produced per unit time will increase, and the productivity (t-sintered ore/day/m ² (t/d/m ² )) will be improved. Therefore, actively mixing high-combustibility carbon materials into the lower layer can effectively improve productivity (increase the sintering speed). High-combustibility carbon materials should be more than 30% by mass and less than 100% by mass relative to the total amount of carbon materials used. If it is less than 30% by mass, it will be related to the combustion speed of carbon materials other than high-combustibility carbon materials and will not increase the sintering speed. If the use of high-combustibility carbon materials is increased to 100% by mass, the combustion speed will increase according to the use amount and the sintering speed will increase.

Mix the highly combustible carbon material into the lower layer as follows.

As shown in FIG1 , the upper section formula raw materials used to form the upper section layer 20 and the lower section formula raw materials used to form the lower section layer 10 are set as different systems (two systems). In addition, in the raw material tanks (1D ₁ ~1D _X ) of the lower section raw material tank group 1D, raw material tanks for storing high-combustibility carbon materials are set. For example, carbon materials other than high-combustibility carbon materials (for example, coke and/or smokeless coal) are stored in the raw material tank 1D ₁ (the first carbon material tank) of the lower section raw material tank group 1D, and high-combustibility carbon materials (for example, carbonized coal and/or PKS carbon) are stored in the raw material tank 1D ₂ (the second carbon material tank). When using more than two kinds of carbon materials other than high-combustibility carbon materials or more than two kinds of high-combustibility carbon materials, raw material tanks for storage can also be set according to various types.

Examples The following are examples that demonstrate the effects of the present invention. In addition, the present invention is not limited to the following examples.

The inventors conducted a sintering pot test (diameter 300mm) to verify the effect of the present invention. The sintering pot test can simulate the sintering of a DL-type sintering machine. Although the sintering pot test device does not use a pallet to move the raw material filling layer like the DL-type sintering machine, the sintering pot test device is a test device that puts the formula raw materials into a container of a predetermined size and ignites them from the upper surface and performs sintering by suction from the bottom.

14 experiments of Comparative Examples 1 to 5 and Inventive Examples 1 to 9 were conducted as shown in Table 3 described below. (Raw material mixing)

Table 2 lists the raw materials and their blending ratios. As shown in Table 2, two kinds of formula raw materials are prepared, namely, formula raw material a and formula raw material b. Among the formula raw materials, iron ore A~D, olivine, quicklime and limestone as new raw materials are blended in the ratios shown in Table 2. Iron ore A~D uses iron ore from different origins. In addition, the condensing material (carbon material) is made of 100% by mass of new raw materials and 4.5% by mass is blended in an additional amount. As carbon material, coke shavings are blended into formula raw material a, and half the amount of coke shavings and PKS carbon as a highly combustible carbon material are blended into formula raw material b. In addition, as shown in Table 3 described later, formula raw material b is used only in the lower layer of Comparative Example 5 and Invention Examples 8 and 9. That is, in Comparative Example 5 and Inventive Examples 8 and 9, PKS carbon is mixed in the lower layer as a condensing material. [Table 2] (Granulation method)

The raw materials of the upper layer and the raw materials of the lower layer were granulated separately. After mixing the formula raw materials for 4 minutes using a drum mixer (diameter 600mm, rotation speed 25rpm), 7.2% of water was added relative to the formula raw materials, and granulation was further performed for 4 minutes. (Test level)

The test level is shown below. As shown in the upper part of Table 3, in Comparative Examples 1 to 5 and Inventive Examples 1 to 9, the following conditions were changed within the range of 21 vol% (no oxygen enrichment) and within 50 vol%, that is, the oxygen concentration conditions of the suction gas supplied from the surface side of the upper layer and sucked from the bottom under atmospheric pressure were changed to implement the two-stage loading and two-stage ignition method. In addition, the details will be explained later, but regarding the supply of oxygen-rich gas, in the sintering boiler tests of Comparative Examples 2, 4, and Inventive Examples 1~3, 6~9, it is set to a height range (position) corresponding to the front half section of the actual machine (the front half of the section from the outlet of the upper ignition furnace to the end of the ore discharge), in Comparative Example 3 it is set to a height range corresponding to the rear half section (the rear half of the section from the outlet of the upper ignition furnace to the end of the ore discharge), in Inventive Example 4 it is set to a height range corresponding to a part of the front half section, and in Inventive Example 5 it is set to a height range corresponding to both the front half section and the rear half section (the entire section). In addition, the so-called part of the first half section of Example 4 is specifically the upstream part of the first half section of the actual machine. When the length of the first half section is 0.5, the part of the first half section is set to the area where the length of the upstream part reaches 0.28. In addition, no rich oxidation is performed in Comparative Examples 1 and 5. [Table 3] (Firing conditions)

The thickness of each layer of the two-stage loading is set to 500mm for the lower layer and 300mm for the upper layer. The pot tanks are prepared in two pieces: a cylindrical pot tank for the lower stage with a height of 500mm (diameter 300mm) and a cylindrical pot tank for the upper stage with a height of 300mm (diameter 300mm).

First, the lower section formula raw materials and upper section formula raw materials after granulation are loaded into the lower section pot and the upper section pot, and the layer height of the lower section layer is made into 500mm, and the layer height of the upper section layer is made into 300mm. Then, the lower section pot with a layer height of 500mm is installed, and the surface of the lower section layer is ignited for 1 minute. After that, the upper section pot with a layer height of 300mm is installed on the lower section pot; in order to realize the sintering process in the upper and lower sections, after confirming that the temperature at the layer height of 320mm (the position of 320mm from the lower surface of the lower section layer) rises (the temperature is measured by the thermocouple described later), the surface of the upper section layer is ignited for 1 minute. The suction pressure is set to be fixed at 1200mmAq (11.8kPa) from the start of ignition. (Sintering time)

Insert thermocouples at the positions of 440mm, 320mm, 230mm, and 170mm in layer height to measure the temperature inside the layer. Since the slower of the upper layer sintering completion and the lower layer sintering completion is regarded as the sintering completion for the entire raw material filling layer (upper layer and lower layer), the longer of the two times, the time required to reach the start of the second temperature rise of the thermocouple at the 440mm position (sintering completion of the upper layer) and the time required to reach the peak of the exhaust temperature at the bellows position (sintering completion of the lower layer), is taken as the sintering time for the entire raw material filling layer. Stop the suction 3 minutes after the sintering completion time point, and the sintering is terminated. (Rich Oxide)

As shown in Table 3, rich oxidation is implemented in four modes: a part of the first half section, the first half section, the second half section, and the entire section. Under the condition of a part of the first half section, rich oxidation is implemented from the beginning of the upper section ignition (more than 0 seconds and less than 2 seconds) until the temperature rises at the 230mm position. Under the condition of the first half section, rich oxidation is implemented from the beginning of the upper section ignition until the temperature rises at the 170mm position corresponding to almost half of the upper section layer height. Under the condition of the second half section, rich oxidation is implemented from the time point when the temperature rises at the 170mm position until the end of the experiment. Under the condition of the entire section, rich oxidation is implemented from the beginning of the upper section ignition until the end of the experiment. (Yield)

The yield is measured as follows. After sintering, the obtained sintered cake is dropped from a height of 2m 4 times, and the particle size +5mm (greater than 5mm) is taken as the sintered finished product and the mass is calculated. The ratio of the sintered finished product to the total mass of the sintered cake (mass %) is defined as the finished product yield here (+5mm%). (Productivity)

The productivity is calculated from the sintering time measured in the above manner using the following formula (2). Productivity (t/d/m ² ) = sintered product quantity (t) / sintering area (0.07m ² ) / sintering time (day) ... (2) (Sintered ore strength)

The strength of sintered ore is measured by cold strength (rotational strength index TI) according to JIS M8712 (2009). However, the mass of the test sample is set at 15kg (15mm-40mm size). In addition, only the lower sintered ore (sintered ore in the lower pot) is measured in the strength measurement. The device used for the measurement is a cylindrical container (diameter 1000mm, depth 500mm), the test sample is placed in the container and rotated at a rotation speed of 25rpm for 8 minutes. For the sintered ore recovered after rotation, the mass of +6mm is calculated, and the ratio of the sintered ore to the 15kg test sample (mass %) is set as the cold strength. (Test results)

The test results are listed in the lower part of Table 3. Figures 2 and 3 are obtained by making graphs of the test results shown in Table 3. Figure 2 is a graph showing the relationship between the oxygen concentration (vol%) of the oxygen-enriched gas and the finished product yield (mass %). Figure 3 is a graph showing the relationship between the oxygen concentration (vol%) of the oxygen-enriched gas and the productivity (t/d/m ² ). In addition, the dotted line shown in Figure 3 is: the line obtained by moving the straight line connecting the plotted points of Comparative Example 1 and the plotted points of Comparative Example 2 in parallel in the direction of increasing 0.5 (t/d/m ² ); and the test example located above the dotted line is defined as the invention example.

As shown in Table 3, Figure 2 and Figure 3, in the test results of the case where the high combustibility carbon material is not used, the yield of Invention Examples 1 to 7 is greatly improved and the productivity is also improved compared to Comparative Examples 1 and 2. In addition, regarding the strength, Invention Example 1 is roughly the same as Comparative Examples 1 and 2, but the strength is improved in Invention Examples 2 to 7. Compared with Invention Example 7 with an oxygen concentration of 46vol%, the yield, strength and productivity are reduced in Comparative Example 4 with an oxygen concentration of 50vol%. From this point, it can be seen that too much oxygen enrichment is not required and an oxygen concentration of 26vol% to 46vol% is more ideal. In order to perform oxygen enrichment, it costs money to produce oxygen (for example, in the method of separating oxygen from air, it is necessary to compress and cool the air, which costs electricity, etc.), so the cost-effectiveness is low. Therefore, Comparative Example 4 with an oxygen concentration of 50 vol% is defined as a comparative example rather than an inventive example. In addition, from the results of Inventive Examples 3 to 5 and Comparative Example 3, which fixed the oxygen concentration at 36 vol% and changed the position of oxygen enrichment, the following can be seen. Regarding oxygen enrichment, the first half period (Inventive Example 3) is more effective than the second half period (Comparative Example 4). Furthermore, although the value of a part of the first half section (invention example 4) is lower than that of the first half section (invention example 3), if the improvement rate of the yield, intensity, and productivity relative to the length of the section in which the rich oxidation is performed is calculated (based on comparative example 1), the effect can be more efficiently enjoyed in a part of the first half section. In particular, in invention example 4, the rich oxidation is performed in the upstream part of the first half section, and it can be seen that the rich oxidation is preferably performed in a fixed section after the outlet of the upper stage ignition furnace.

The test results of the case using a highly combustible carbon material are as follows. Compared with Comparative Example 1 in which PKS carbon is not mixed, the yield and productivity of Comparative Example 5 in which high combustible carbon material (PKS carbon) is mixed in the lower layer without oxygen enrichment are both reduced. In contrast to this result, compared with Comparative Example 5 in which high combustible carbon material (PKS carbon) is mixed in the lower layer without oxygen enrichment, and Comparative Example 1 in which oxygen enrichment and PKS carbon are not mixed, in Inventive Example 8 in which PKS carbon is mixed in the lower layer and oxygen enrichment is performed, the productivity and yield are significantly improved. Moreover, compared to Comparative Example 5 in which no oxygen enrichment was performed and a highly combustible carbon material (PKS carbon) was mixed in the lower layer, the productivity and yield were greatly improved in Invention Example 9 in which PKS carbon was mixed and the oxygen concentration of the supply gas was increased to perform oxygen enrichment. Compared to Invention Example 8 in which PKS carbon was mixed in the lower layer and oxygen enrichment was performed (oxygen concentration 26 vol%), the productivity and yield were improved in Invention Example 9 (oxygen concentration 46 vol%), and in particular, the productivity was the highest among all the test examples. In addition, not limited to PKS carbon, the same effect can be observed in carbonized coal as a highly combustible carbon material. From these results, it can be seen that the combination of the use of highly combustible carbon materials and oxygen enrichment is very effective.

3: Sintering section 5: Direction of movement of the support plate 6: Suction from below 7: Oxygen-enriched gas supply equipment 8: Exhaust hood 9: Gas pipe 10: Lower layer 20: Upper layer 100: Sintering machine 1A: Drum mixer for lower layer 1B: Feed hopper for lower layer 1C: Ignition furnace for lower layer 1D: Lower raw material tank group 1D ₁ ~1D _X ,2D ₁ ~2D _y : Raw material tank 2A: Drum mixer for upper layer 2B: Feed hopper for upper layer 2C: Ignition furnace for upper layer 2D: Upper raw material tank group 10A: Lower layer combustion zone 20A: Upper layer combustion zone X, X1, X2: After the outlet of the upper ignition furnace Y: Ore discharge end Z: Middle position

FIG. 1 is a schematic diagram showing the steps of producing sintered ore using a two-stage loading and two-stage ignition sintering method as an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the oxygen concentration of the oxygen-enriched gas and the product yield.

FIG. 3 is a graph showing the relationship between the oxygen concentration of oxygen-enriched gas and the production rate.

3: Sintering section

5: Pallet movement direction

6: Suction from below

7: Oxygen-enriched gas supply equipment

8: Exhaust hood

9: Gas pipe

10: Lower layer

20: Upper layer

100: Sintering machine

1A: Use a drum mixer for the lower stage

1B: Feed hopper for the lower section

1C: Use ignition furnace for the lower section

1D: Lower section raw material tank group

1D ₁ ~1D _x , 2D ₁ ~2D _y : Raw material tank

2A: Use a drum mixer for the upper stage

2B: Upper section with feed hopper

2C: Use ignition furnace for the upper part

2D: Upper raw material tank group

10A: Lower layer burning zone

20A: Upper layer burning zone

X, X1, X2: After the upper stage ignition furnace exit

Y: Mining end

Z: Middle position

Claims (7)

A method for manufacturing sintered ore, comprising the following steps: Loading the formulated raw material granules of the lower system into a sintering machine to form a lower raw material filling layer; Loading the formulated raw material granules of the upper system onto the aforementioned lower raw material filling layer to form an upper raw material filling layer; and Ignite the surface of the aforementioned lower raw material filling layer and the surface of the aforementioned upper raw material filling layer respectively, and introduce oxygen-containing gas into the aforementioned lower raw material filling layer and the aforementioned upper raw material filling layer by suction from below under atmospheric pressure; wherein, After the ignition of the aforementioned upper raw material filling layer is completed, at least a portion of the gas sucked from the surface side of the aforementioned upper raw material filling layer is made to be oxygen-rich gas with an oxygen concentration of 26 volume % or more and 46 volume % or less; and, In the longitudinal direction of the sintering machine, the middle position of the section from the outlet of the upper ignition furnace to the end of the ore discharge is the middle position, and the section from the outlet of the upper ignition furnace to the middle position is the front half section. At this time, the area to which the oxygen-enriched gas is supplied is the area including a part of the front half section. A method for producing sintered ore as claimed in claim 1, wherein a portion of the aforementioned front half section is an upstream side portion of the aforementioned front half section. In the method for manufacturing sintered ore as claimed in claim 1, the section from the aforementioned middle position to the aforementioned ore discharge end in the length direction of the sintering machine is defined as the second half section. At this time, the area to which the oxygen-enriched gas is supplied includes at least a portion corresponding to the aforementioned first half section, and the portion corresponding to the aforementioned first half section is longer than the portion corresponding to the aforementioned second half section. The method for producing sintered ore as claimed in claim 1, wherein the area to which the oxygen-rich gas is supplied is the first half section or a portion of the first half section. A method for producing sintered ore as claimed in any one of claims 1 to 4, wherein the raw material for the lower raw material filling layer is a highly combustible carbon material having a combustion rate of 0.0022 (1/second) or more at 700°C. A method for producing sintered ore as claimed in claim 5, wherein the highly combustible carbon material comprises carbon obtained by dry distillation of coal having a Roga index of less than 10. A method for producing sintered ore as claimed in claim 5, wherein the highly combustible carbon material comprises palm shell carbon.

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