Method for producing sintered ore

Abstract

Provided is a method for producing sintered ore by increasing the yield when a carbon material having a low combustion initiation temperature is used in a sintering step. A method for producing sintered ore using a carbon material having a combustion initiation temperature of 550 DEG C or less, in which a gaseous fuel supplied above a charge layer of a sintering machine is sucked together with air from below the charge layer and introduced into the charge layer. Preferably, in the advancing direction of the sintering machine, the gas fuel is sucked within the 1 / 2 length range of the ore feeding part side on the loading layer; the carbon material having a combustion initiation temperature of 550 DEG C or less is used as either or both of an organic resource other than fossil fuel and a carbon material produced using the organic resource as a starting material; the concentration of the gas fuel contained in the air introduced into the loading layer is set to be lower than the combustion lower limit concentration; when the gas fuel is supplied, the amount of the carbon material is reduced in a range of 10% or less with respect to the total amount of all the carbon materials when the gas fuel is not supplied, in terms of heat equivalent to coke.

Description

Technical Field

[0001] The present invention relates to a method for producing sintered ore used in the field of steelmaking. Background Art

[0002] The iron ore sintering process is a process in which a substance obtained by mixing iron ore, a flux, and a carbon material as a solid fuel is sintered in a sintering machine using the combustion heat of the carbon material. Usually, coke powder is used as the carbon material. As a risk dispersion measure against price fluctuations of raw coal, failures of coke manufacturing equipment, etc., anthracite other than coke powder is sometimes used.

[0003] On the other hand, due to the increasing awareness of environmental protection in recent years, in addition to ideas such as risk dispersion, the diversification of carbon materials has been continuously promoted for the purpose of reducing the environmental burden.

[0004] For example, Patent Document 1 discloses carbon materials for iron ore sintering envisioned as sub-bituminous coal and lignite. For this carbon material, the reaction start temperature is 550°C or lower, the volatile component (VM) is 1.0% or more, the atomic ratio of hydrogen to carbon (H / C) is 0.040 or more, and the pore volume of pores with a pore diameter of 0.1 to 10 μm measured by mercury intrusion porosimetry is 50 mm 3 / g or more.

[0005] Patent Document 2 discloses the following method: when using 30% or more of high-crystalline water iron ore containing 4.0% by mass or more of crystal water, a solid fuel containing 10% by mass or more with a combustion start temperature lower than 450°C is used.

[0006] Patent Document 3 discloses the following method: in a two-stage ignition sintering method in which a sintering charging layer is formed in two stages, the surfaces of each are ignited and sintered, coke and / or anthracite, and a carbon material with a lower combustion start temperature than these are used in the raw materials on the lower stage side.

[0007] Patent Document 4 discloses the following method: a carbon material with a low combustion start temperature is blended in coke powder and / or anthracite as a coagulant in the range of 25 to 75% of the total carbon component, and at least one of a low combustion start temperature carbon material and a high combustion start temperature carbon material is added in the latter half of the granulation process.

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: International Publication No. 2010 / 087468

[0011] Patent Document 2: International Publication No. 2010 / 106756

[0012] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2020-186436

[0013] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2022-033594 Summary of the Invention

[0014] Problems to be Solved by the Invention

[0015] However, there are problems as described below in the prior art.

[0016] If a carbon material with a low combustion start temperature is used in the sintering process, the yield will decrease. The techniques disclosed in Patent Documents 1 and 2 explain the use of carbon materials with low reaction start temperatures and low combustion start temperatures. However, the deteriorating effect on the yield in the sintered ore manufacturing process when using a carbon material with a low combustion start temperature is not explained, and countermeasures for improving the yield are not considered, either.

[0017] In addition, in the technique disclosed in Patent Document 3, there is a premise of a two-stage ignition sintering method and it cannot be applied to a general sintering method. In the technique disclosed in Patent Document 4, the carbon content is uniformly controlled. On the other hand, it is not considered that there are many types of carbon materials with a low combustion start temperature and their combustion start temperatures vary, and the accompanying effect on the yield is not considered.

[0018] The present invention has been completed in view of the above circumstances, and an object thereof is to provide a method for manufacturing sintered ore with improved yield when using a carbon material with a low combustion start temperature in the sintering process.

[0019] Means for Solving the Problems

[0020] The method for manufacturing sintered ore according to the present invention, which advantageously solves the above problems, is characterized in that it is a method for manufacturing sintered ore using a carbon material having a combustion start temperature of 550°C or lower, wherein a gaseous fuel supplied above the charging layer of a sintering machine is sucked from below the charging layer together with air and introduced into the charging layer.

[0021] It should be noted that the method for manufacturing sintered ore according to the present invention has the following more preferable means for solving the problems:

[0022] (a) sucking the gaseous fuel within a range of 1 / 2 of the length on the ore feeding section side on the charging layer in the traveling direction of the sintering machine;

[0023] (b) setting the carbon material having a combustion start temperature of 550°C or lower to any one or both of an organic-based resource other than a fossil fuel and a carbon material manufactured from the organic-based resource;

[0024] (c) setting the gaseous fuel contained in the air introduced into the charging layer to a concentration lower than the lower explosion limit concentration;

[0025] (d) When supplying the aforementioned gaseous fuel, in terms of heat conversion equivalent to coke, the aforementioned carbonaceous materials are reduced in a range of 10% or less relative to the total amount of all carbonaceous materials when the aforementioned gaseous fuel is not supplied;

[0026] etc.

[0027] Effects of the Invention

[0028] In the method for manufacturing sintered ore according to the present invention, when using carbonaceous materials with a low combustion start temperature in the sintering process, the gaseous fuel supplied above the charging layer of the sintering machine is sucked from below the charging layer together with air and introduced into the charging layer, whereby the heating mode can be improved and the reduction in the yield can be suppressed. Description of the Drawings

[0029] Figure 1 is a graph showing the influence of biomass carbon and gaseous fuel on the sintering yield.

[0030] Figure 2 is a graph showing the influence of the blowing range of gaseous fuel on the sintering yield. Detailed Description of the Invention

[0031] The embodiments of the present invention will be specifically described below. The following embodiments are examples of devices and methods for embodying the technical concept of the present invention, and the constitution is not limited to the following content. That is, the technical concept of the present invention can be variously changed within the technical scope described in the claims.

[0032] In the process of diversifying carbon materials in order to reduce the environmental load, organic resources other than fossil fuels and carbonaceous materials manufactured from such organic resources (hereinafter referred to as biomass carbon) have attracted attention. Since biomass carbon absorbs carbon dioxide gas during the period before the plants used as its raw materials grow, from the perspective of carbon neutrality, when using fuels containing such biomass carbon, the amount of carbon dioxide gas discharged to the outside of the system can be regarded as zero emissions. Therefore, the use of biomass carbon has also been studied in the iron ore sintering process that usually uses coke powder. As a characteristic of biomass carbon, its combustion start temperature is lower than that of coke. The combustion start temperature of coke is in the range of 650 - 750 °C, while the combustion start temperature of biomass carbon is approximately 550 °C or lower.

[0033] ​​In this embodiment, in the sintering process, a flux and carbonaceous material as auxiliary raw materials are added to iron ore and continuously charged onto a sintering machine to form a sintering bed (charged layer). After ignition at the upper end of the sintering bed, exhaust gas is suctioned from the lower end, so that the combustion of the carbonaceous material propagates from the upper end to the lower end of the sintering bed, and the heat is used for the reaction / agglomeration of the iron ore and the flux. The suction of the exhaust gas from the lower end is performed by a blower, and the suctioned exhaust gas passes through a pipe and is discharged from a chimney via a dust collector, desulfurization, and denitration equipment.

[0034] Biomass carbon is characterized by its low combustion start temperature. This is because compared with coke powder (derived from fossil fuels) generally used in the sintering process, biomass carbon is porous and has a very large specific surface area, so a high combustion rate can be obtained even at a low temperature. Therefore, biomass carbon not only shows a low combustion start temperature but also shows a tendency of a high combustion rate after the start of combustion.

[0035] The combustion reaction of a carbon material is a gas-solid reaction. The solid carbon material reacts with oxygen in the surrounding gas and burns. In a gas-solid reaction under conditions of gas flow such as sintering, there is an extremely thin layer region called a gas boundary layer on the solid surface. The gas boundary layer maintains laminar flow without being affected by the outer turbulent flow. In the combustion of a carbon material, oxygen diffuses from the outside of the gas boundary layer into the gas boundary layer and reaches the surface of the carbon material for combustion. Among them, when the combustion rate of the carbon material is very fast, even when the oxygen concentration in the surroundings is high, the oxygen consumption rate at the surface of the carbon material based on combustion becomes larger than the oxygen supply rate based on the oxygen diffusion in the gas boundary layer, and the oxygen concentration in the gas boundary layer decreases. Therefore, incomplete combustion of the carbon material occurs and the generation amount of carbon monoxide increases. Therefore, it is considered that when the combustion rate is very fast, a part of the combustion heat of the carbon material is not utilized and is discharged out of the system in the form of carbon monoxide, so the reaction heat for sintering decreases, and thus the yield rate decreases. In addition, a fast combustion rate means a short time from the start of combustion to the end of combustion. As a result, it burns out immediately after the start of combustion and starts to cool due to the air from above. Therefore, the charged layer in the sintering machine forms a heating mode in which the temperature rises rapidly and then drops in a short time. Due to this effect, there is also an influence that the sintering reaction in the high-temperature region only proceeds for a short time and the bonding between ores becomes insufficient.

[0036] In this embodiment, the gaseous fuel above the charging layer supplied to the sintering machine is sucked from below the charging layer together with air and introduced into the charging layer. The introduced gaseous fuel burns above the combustion position of the carbonaceous material in the height direction of the charging layer, mitigating the cooling effect caused by the air flowing in from the upper layer. Thereby, the temperature drop of the charging layer is suppressed. Due to this effect, the time for maintaining the charging layer at a high temperature, i.e., the time for the sintering reaction, can be kept longer. Therefore, the binding between the ores can be made firm. This effect also appears under the conditions of using ordinary coke powder, etc. Especially in the case of carbonaceous materials such as biomass carbon with a low combustion start temperature, the sintering reaction time in the high-temperature region in the basic heating mode before injecting the gaseous fuel is short. Therefore, the effect of extending the sintering reaction time in the high-temperature region brought about by injecting the gaseous fuel appears more significantly than when using coke, etc.

[0037] In addition, the gaseous fuel burns above the start of combustion of the carbonaceous material in the charging layer, thereby consuming oxygen and reducing the oxygen concentration supplied to the carbonaceous material burning below in the charging layer. Due to this effect, there is an influence of slowing down the combustion rate of the carbonaceous material. Due to this influence, there is a possibility of production reduction due to the reduction in the combustion rate in the case of coke powder. On the other hand, in the case of biomass carbon with a high combustion rate, this adverse effect can be mitigated.

[0038] Generally, in a sintering machine, the upper part has a tendency for the yield to decrease due to insufficient heat, and the lower part has a tendency for heat excess. This is because cold air directly flows into the upper part from above the charging layer. The upper part is more susceptible to the influence of insufficient heat caused by the use of biomass carbon. Therefore, the suction of the gaseous fuel is preferably carried out within the range of 1 / 2 of the length on the ore feeding section side of the charging layer where the reaction zone exists in the upper part. The suction of the gaseous fuel is more preferably carried out within the range of 1 / 4 or more of the length on the ore feeding section side of the sintering machine, and further preferably within the range of 1 / 3 or more of the length.

[0039] The gaseous fuel is preferably diluted to a concentration lower than the lower combustion limit. This is because in the case of external ignition above the charging layer due to residual fire on the charging layer of the sintering machine, not only the effect of injecting the gaseous fuel cannot be fully obtained, but also there may be a risk of fire, etc. In addition, as the gaseous fuel, any gas such as town gas, natural gas, propane gas, coke oven gas, etc. can be used. Town gas, natural gas, propane gas, etc. without toxicity are preferred. For example, the lower combustion limit concentration of each gaseous fuel relative to air is: town gas: 4.5 vol%, natural gas: 4.4 vol%, propane gas: 2.4 vol%, etc. The lower limit of the concentration of the gaseous fuel is determined by the required heat. From the viewpoint of effectively utilizing the gaseous fuel, the lower limit of the concentration of the gaseous fuel contained in the air introduced into the charging layer is preferably greater than 0 vol%, and more preferably a concentration of 1 / 20 or more of the lower combustion limit concentration.

[0040] In addition, when the yield is increased by introducing gaseous fuel into the charged layer, the blending amount of carbon materials can also be reduced within the range of 10% or less relative to the total blending amount of all carbon materials. This is because the heat shortage in the upper part of the charged layer is eliminated by blowing in gaseous fuel, so that the amount of heat surplus in the lower part can be reduced.

[0041] Examples

[0042] (Example 1)

[0043] A batch-type sintering test apparatus was used to verify the effects of the present invention. T1 is the level of using only the commonly used coke, and T3 is the level of replacing 20% of the coke with biomass carbon. In T2, T4 to T7, town gas was adjusted as the gaseous fuel to a concentration of 0.4% by volume relative to the aspirated air, and blown in for 7 minutes starting from 30 seconds after the ignition furnace was extinguished. It should be noted that the same blending amounts of ore and auxiliary raw materials were used. The test conditions and results are shown in Table 1, Figure 1 . Compared with T1 using only coke as a reference example, the yield increased by about 3% in T2 with town gas blown in. On the other hand, in T3 where 20% of the coke was replaced with biomass carbon, the yield decreased by about 8% relative to the base (T1). In contrast, the yield increased by about 10% in T4 with town gas blown in. In T4, an effect greater than that of T2, which is the level of blowing in town gas relative to T1 under the same heat condition, was confirmed. On the other hand, T5, T6, and T7 are the levels reduced in increments of 0.2% starting from T4 in terms of the heat equivalent to coke. It should be noted that at this time, the reduction was carried out in such a way that the ratio of coke to biomass carbon remained unchanged. In T5, T6, and T7, as the reduction amplitude increased, the yield decreased. In T7 where 12% was reduced relative to the total coke amount, the result was a yield lower than that of the base (T1).

[0044] [Table 1]

[0045]

[0046] ※ Mass percentage after heat equivalent conversion to coke relative to the charged raw materials

[0047] (Example 2)

[0048] Next, the blowing range of the gaseous fuel was verified. Since this test was a batch test, the blowing of the total length on the charging layer was simulated as the blowing during the total sintering time. The town gas was adjusted to a concentration of 0.4 vol% relative to the aspirated air and blown in. It should be noted that the same compounding amounts of ore and auxiliary raw materials were used. The test conditions and results are shown in Table 2, Figure 2 . Based on T3 of Example 1, the gaseous fuel blowing for T4 was 7 minutes, which was 25% of the overall sintering time. In T8 - T10, the gaseous fuel blowing time was made 50%, 75%, and 100% of the overall sintering time. As a result, an increase effect in the yield was confirmed until the gaseous fuel blowing time reached 50% of the overall sintering time, but the effect basically stagnated under the conditions of 75% and 100%. It is considered that in the latter half of the sintering time, the reaction zone reaches the lower part of the charging layer, and since sufficient heat has already been obtained, it is difficult to exhibit the effect of blowing in the town gas.

[0049] [Table 2]

[0050]

[0051] ※ Mass percentage after heat conversion equivalent to coke relative to the charged raw materials

Claims

1. A method for manufacturing sintered ore, which is a method for manufacturing sintered ore using a carbon material with a combustion start temperature of 550 °C or lower, wherein, The gaseous fuel supplied above the charging layer of the sintering machine is sucked from below the charging layer together with air and introduced into the charging layer.

2. The method for manufacturing sintered ore according to claim 1, wherein, The gaseous fuel is sucked within a range of 1 / 2 of the length on the ore feeding section side on the charging layer in the traveling direction of the sintering machine.

3. The method for manufacturing sintered ore according to claim 1, wherein, The carbon material with a combustion start temperature of 550 °C or lower is either one or both of an organic-based resource other than fossil fuel and a carbon material manufactured from the organic-based resource.

4. The method for manufacturing sintered ore according to claim 1, wherein, The gaseous fuel contained in the air introduced into the charging layer is set to a concentration lower than the lower explosive limit concentration.

5. The method for manufacturing sintered ore according to claim 1, wherein, When supplying the gaseous fuel, in terms of heat conversion equivalent to coke, the carbon material is reduced within a range of 10% or less relative to the total amount of all the carbon materials when the gaseous fuel is not supplied.

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