Sinter manufacturing method

Abstract

Proposed is a method for producing a sintered ore, in which yield is improved when a carbon material with a low combustion initiation temperature is used in a sintering step. The present invention is a method for producing a sintered ore using a carbon material with a combustion initiation temperature of 550°C or below, wherein a gaseous fuel supplied above a charging layer of a sintering machine is drawn in from below the charging layer, together with air, and introduced into the charging layer. It is preferable that: the gaseous fuel is drawn in, in a direction of advancement of the sintering machine, in a one-half length range on a feed unit side over the charging layer; the carbon material with a combustion initiation temperature of 550°C or below is a non-fossil-fuel organic-based resource and / or a carbon material produced using the non-fossil-fuel organic-based resource as a raw material; the gaseous fuel included in the air introduced into the charging layer has a concentration below the lower limit of concentration for combustion; and when the gaseous fuel is being supplied, the amount of the carbon material is cut back to 10% or less, on a coke-equivalent calorie basis, of the total amount of all of the carbon material when the gaseous fuel is not being supplied.

Description

[Technical Field]

[0001] The present invention relates to a method for producing sintered ore for use in the steel industry. [Background technology]

[0002] In the iron ore sintering process, a mixture of iron ore, flux, and a carbonaceous material as a solid fuel is sintered in a sintering machine using the heat generated by the combustion of the carbonaceous material. Coke breeze is generally used as the carbonaceous material. However, other materials such as anthracite may also be used to spread the risk of fluctuations in the price of raw coal and problems with coke manufacturing equipment.

[0003] Meanwhile, in response to the growing awareness of environmental conservation in recent years, carbon materials are becoming more diversified with the intention of reducing the burden on the environment, apart from the idea of ​​risk diversification.

[0004] For example, Patent Document 1 discloses a carbon material for sintering iron ore, which is intended for subbituminous coal and lignite. The carbon material has a reaction initiation temperature of 550°C or less, a volatile matter (VM) of 1.0% or more, a hydrogen to carbon atomic ratio (H / C) of 0.040 or more, and a pore volume of 50 mm2 with a pore diameter of 0.1 to 10 μm measured by mercury porosimetry. 3 / g or more.

[0005] Patent Document 2 discloses a method in which 30% or more of high-crystallization-water iron ore containing 4.0% or more by mass of crystallization water is used, and 10% or more by mass of solid fuel having a combustion start temperature of less than 450°C is included.

[0006] Patent Document 3 discloses a two-stage ignition sintering method in which a sintering bed is formed in two stages and sintering is carried out by igniting the surface of each stage, using coke or anthracite and a carbonaceous material with a lower combustion start temperature as raw materials in the lower stage.

[0007] Patent Document 4 discloses a method in which a carbonaceous material with a low combustion initiation temperature is blended with fine coke or anthracite as a coagulant in an amount of 25 to 75% of the total carbon content, and at least one of a low combustion initiation temperature carbonaceous material and a high combustion initiation temperature carbonaceous material is added in the latter half of the granulation process. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2010 / 087468 [Patent Document 2] International Publication No. 2010 / 106756 [Patent Document 3] Japanese Patent Publication No. 2020-186436 [Patent Document 2] Japanese Patent Publication No. 2022-033594 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the conventional technology has the following problems. The use of carbonaceous materials with low combustion initiation temperatures in the sintering process reduces the yield. The technologies disclosed in Patent Documents 1 and 2 describe the use of carbonaceous materials with low reaction initiation temperatures and combustion initiation temperatures. However, they do not mention the effect of using carbonaceous materials with low combustion initiation temperatures on the yield deterioration in the sinter ore manufacturing process, nor do they consider measures to improve the yield.

[0010] Furthermore, the technology disclosed in Patent Document 3 is premised on a two-stage ignition sintering method, and cannot be used for general sintering methods. The technology disclosed in Patent Document 4 uniformly classifies materials by carbon content. However, it does not take into account that there are many types of carbonaceous materials with low combustion initiation temperatures, and that their combustion initiation temperatures vary, and therefore the impact on yield that accompanies this is not taken into account.

[0011] The present invention has been made in view of the above circumstances, and aims to propose a method for producing sintered ore with improved yield when using a carbonaceous material with a low combustion start temperature in the sintering process. [Means for solving the problem]

[0012] The method for producing sintered ore according to the present invention, which advantageously solves the above-mentioned problems, is a method for producing sintered ore using a carbonaceous material having a combustion start temperature of 550°C or less, and is characterized in that gaseous fuel supplied above the sintering bed of a sintering machine is sucked together with air from below the sintering bed and introduced into the sintering bed.

[0013] The method for producing sintered ore according to the present invention is as follows: (a) sucking the gaseous fuel within a half-length range of the ore feeding section on the sintering bed in the traveling direction of the sintering machine; (b) The carbonaceous material having a combustion start temperature of 550°C or less is either or both of an organic resource excluding fossil fuels and a carbonaceous material produced using the organic resource as a raw material; (c) adjusting the concentration of the gaseous fuel contained in the air introduced into the sintering bed to be less than the lower limit of flammability; (d) when the gaseous fuel is supplied, the amount of the carbonaceous material is reduced by 10% or less in terms of the calorific value equivalent to coke compared to the total amount of all the carbonaceous materials when the gaseous fuel is not supplied; This may be a more preferable solution. [Effects of the Invention]

[0014] In the method for producing sintered ore according to the present invention, when a carbonaceous material with a low combustion start temperature is used in the sintering process, the gaseous fuel supplied above the sintering bed of the sintering machine is sucked together with air from below the sintering bed and introduced into the sintering bed, thereby improving the heat pattern and suppressing a decrease in yield. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a graph showing the influence of biomass charcoal and gaseous fuel on sintering yield. [Figure 2] 1 is a graph showing the effect of the gas fuel injection range on the sintering yield. DETAILED DESCRIPTION OF THE INVENTION

[0016] The following is a detailed description of embodiments of the present invention. The following embodiments are intended to exemplify equipment and methods for embodying the technical concept of the present invention, and are not intended to limit the configuration to those described below. In other words, the technical concept of the present invention can be modified in various ways within the technical scope defined in the claims.

[0017] In an effort to diversify carbon materials to reduce environmental impact, attention is being paid to organic resources other than fossil fuels and carbonaceous materials produced from such organic resources (hereinafter referred to as biomass charcoal). Because biomass charcoal absorbs carbon dioxide during the growth of the plants that produce it, fuels made from biomass charcoal can be considered carbon-neutral and therefore emit no carbon dioxide outside the system. For this reason, the use of biomass charcoal in iron ore sintering processes, which typically use coke breeze, is being considered. A key feature of biomass charcoal is its lower combustion initiation temperature compared to coke. While the combustion initiation temperature of coke is in the range of 650–750°C, the combustion initiation temperature of biomass charcoal is generally below 550°C.

[0018] In this embodiment, flux and carbonaceous material are added to iron ore as auxiliary raw materials during the sintering process, and the materials are continuously charged onto the sintering machine to form a sintering bed (charging layer). After the sintering bed is ignited at the top, exhaust gas is drawn in from the bottom, causing the combustion of the carbonaceous material to spread from the top to the bottom of the bed, and the heat is used to cause the iron ore and flux to react and form into agglomerates. Exhaust gas is drawn in from the bottom using a blower. The drawn exhaust gas passes through a duct, passes through a dust collector, and passes through desulfurization and denitrification equipment, and is then discharged from a chimney.

[0019] A distinctive feature of biomass charcoal is its low combustion initiation temperature. This is thought to be because biomass charcoal is porous and has a very large specific surface area compared to the fine coke (derived from fossil fuels) commonly used in the sintering process, allowing for a high combustion rate even at low temperatures. Therefore, biomass charcoal not only has a low combustion initiation temperature, but also tends to have a high combustion rate once combustion has begun.

[0020] The combustion reaction of carbon materials is a gas-solid reaction. Solid carbon materials react with oxygen in the surrounding gas and burn. In gas-solid reactions under flowing gas conditions, such as sintering, a very thin layer called a gas film exists on the solid surface. The gas film maintains a laminar flow unaffected by external turbulence. Oxygen diffuses from the outside of the gas film through the gas film and reaches the surface of the carbon material, where it is used for combustion. However, if the combustion rate of a carbon material is very fast, even in high ambient oxygen concentrations, the rate of oxygen consumption at the surface due to combustion of the carbon material is greater than the rate of oxygen supply due to oxygen diffusion within the gas film, resulting in a decrease in the oxygen concentration within the gas film. This causes incomplete combustion of the carbon material and increases the amount of carbon monoxide produced. Therefore, if the combustion rate is very fast, some of the heat of combustion of the carbon material is not utilized and is emitted as carbon monoxide outside the system. This is thought to result in a decrease in yield due to a decrease in reaction heat used for sintering. Furthermore, a fast combustion rate indicates a short time from the start of combustion to the end of combustion. The material burns out quickly after the start of combustion, and cooling begins due to air coming from above. Therefore, the sintering bed in the sintering machine forms a heat pattern in which the temperature rises rapidly and then falls in a short time, which has the effect of causing the sintering reaction in the high temperature region to occur only in a short time, resulting in insufficient bonding between the ores.

[0021] In this embodiment, gaseous fuel is supplied above the sintering bed of the sintering machine and, together with air, is sucked into the sintering bed from below. The introduced gaseous fuel burns above the burning carbonaceous material in the vertical direction of the sintering bed, mitigating the cooling effect of the air flowing in from the upper layer. This prevents the temperature of the sintering bed from dropping. This effect extends the time the sintering bed is maintained at a high temperature, i.e., the sintering reaction time. This also strengthens the bonding between the ores. This effect is also achieved when using conventional coke breeze. In particular, with carbonaceous materials with low combustion initiation temperatures, such as biomass charcoal, the sintering reaction time in the high-temperature region of the base heat pattern before gaseous fuel injection is short. Therefore, the effect of gaseous fuel injection in extending the sintering reaction time in the high-temperature region is greater than when using coke.

[0022] Furthermore, the combustion of gaseous fuel above the point where the carbonaceous material in the sintering bed begins consumes oxygen, which can reduce the oxygen concentration supplied to the carbonaceous material burning below in the sintering bed. This has the effect of slowing down the combustion rate of the carbonaceous material. As a result, there is a possibility of reduced production of coke breeze due to the slower combustion rate. On the other hand, this adverse effect can be mitigated with biomass charcoal, which has a high combustion rate.

[0023] Generally, in sintering machines, the upper layer tends to have a low yield due to insufficient heat, while the lower layer tends to have excessive heat. This is because cold air flows directly into the upper layer from above the sintering bed. The upper layer is more susceptible to the effects of insufficient heat due to the use of biomass coal. Therefore, it is preferable that the gaseous fuel be drawn within a range of half the length of the ore feed section above the sintering bed where the reaction zone is located in the upper layer. It is more preferable that the gaseous fuel be drawn within a range of at least one-quarter of the length of the ore feed section of the sintering machine, and even more preferably within a range of at least one-third of the length.

[0024] It is preferable to dilute the gaseous fuel below its lower flammable concentration. This is because if residual fires on the sintering bed ignite outside above the sintering bed, the effect of gaseous fuel injection will be insufficient and it may even lead to a fire. Furthermore, any gas, such as city gas, natural gas, propane gas, or coke oven gas, can be used as the gaseous fuel. Non-toxic city gas, natural gas, or propane gas is preferred. For example, the lower flammable concentration of each gaseous fuel relative to air is 4.5 vol% for city gas, 4.4 vol% for natural gas, and 2.4 vol% for propane gas. The lower flammable concentration of the gaseous fuel is determined by the required calorific value. From the perspective of effective use of the gaseous fuel, the lower flammable concentration of the gaseous fuel contained in the air introduced into the sintering bed is preferably greater than 0 vol%, and more preferably at least 1 / 20 of the lower flammable concentration.

[0025] In addition, if the yield increases due to the introduction of gaseous fuel into the sintering bed, the amount of carbonaceous material may be reduced within a range of 10% or less of the total amount of all carbonaceous materials. This is because the injection of gaseous fuel eliminates the heat shortage in the upper layer of the sintering bed, thereby reducing the excess heat in the lower layer. [Example]

[0026] Example 1 The effects of the present invention were verified using a batch-type sintering test apparatus. T1 was a test using only commonly used coke, while T3 was a test using 20% ​​biomass charcoal instead of the coke. In T2, T4, and T7, city gas was used as the gaseous fuel, adjusted to a concentration of 0.4% by volume relative to the intake air, and injected for 30 seconds to 7 minutes after the ignition furnace was extinguished. The same amounts of ore and auxiliary materials were used. The test conditions and results are shown in Table 1 and Figure 1. Compared to T1, which uses only coke as a reference example, T2, which injected city gas, showed an approximately 3% improvement in yield. On the other hand, T3, which replaced 20% of the coke with biomass charcoal, showed an approximately 8% decrease in yield compared to the base (T1). In contrast, T4, which injected city gas, showed an approximately 10% improvement in yield. A greater effect was confirmed in T4 than in T2, which injected city gas but with the same calorific value. On the other hand, T5, T6, and T7 were reduced by 0.2% each in terms of heat equivalent to coke from T4. The reductions were made so that the ratio of coke to biomass coal remained unchanged. As the reduction range increased for T5, T6, and T7, the yield decreased. T7, which reduced the total coke amount by 12%, resulted in a yield lower than the base (T1) yield.

[0027] [Table 1]

[0028] Example 2 Next, the gaseous fuel injection range was examined. Since this test was a batch-type test, injection over the entire length of the sintering bed was simulated as injection over the entire sintering time. The city gas was injected at a concentration of 0.4% by volume relative to the aspirated air. The same amounts of ore and auxiliary materials were used. The test conditions and results are shown in Table 2 and Figure 2. Based on T3 in Example 1, T4 involved 7 minutes of gaseous fuel injection, accounting for 25% of the total sintering time. In T8 to T10, the gaseous fuel injection time was 50%, 75%, and 100% of the total sintering time. The results showed that the gaseous fuel injection time increased yield up to 50% of the total sintering time, but remained almost unchanged at 75% and 100%. It is believed that the effect of city gas injection was not fully realized in the latter half of the sintering time because the reaction zone had already reached the lower part of the sintering bed and sufficient heat was already being generated.

[0029] [Table 2]

Claims

1. A method for producing sintered ore using a carbonaceous material having a combustion start temperature of 550°C or less, wherein the gaseous fuel supplied to the upper part of the sintering machine's sintering bed is sucked together with air from below the sintering bed and introduced into the sintering bed, The gaseous fuel is introduced by diluting it to a concentration below the lower limit of combustion in an amount sufficient to ensure a sintering reaction time in a high temperature range that is reduced by using the carbonaceous material instead of the coke powder in the heat pattern, The gaseous fuel is any one of city gas, natural gas, and propane gas. Here, the heat pattern refers to a temperature change in which the temperature of the charging bed in the sintering machine rises sharply and then falls in a short time. A method for producing sintered ore.

2. 2. The method for producing sintered ore according to claim 1, wherein the gaseous fuel is sucked within a range of half the length of the ore feeding section on the sintering bed in the traveling direction of the sintering machine.

3. 2. The method for producing sintered ore according to claim 1, wherein the carbonaceous material having a combustion start temperature of 550°C or less is either or both of an organic resource excluding fossil fuels and a carbonaceous material produced using the organic resource as a raw material.

4. 2. The method for producing sintered ore according to claim 1, wherein, when the gaseous fuel is supplied, the carbonaceous material is reduced by 10% or less in terms of heat equivalent to coke relative to the total amount of all carbonaceous materials when the gaseous fuel is not supplied.

Images