Carbon material for sintering, sintered ore, and method for producing carbon material for sintering

Abstract

Provided are a carbon material for sintering, a sintered ore, and a method for producing the carbon material for sintering, which are capable of reducing the environmental burden during the production of the sintered ore and suppressing a decrease in the yield of the sintered ore and equipment failure. A carbon material for sintering, which is used in a process for sintering iron ore, and which comprises coal and biomass carbon as blending materials, the proportion (mass%) of fixed carbon of the biomass carbon relative to fixed carbon of the coal and the biomass carbon after dry distillation being greater than 0 and 30 mass% or less, and the volatile component content after dry distillation being 5.0 mass% or less.

Description

Technical Field

[0001] The present invention relates to a carbon material for sintering used in the sintering process of iron ore, sintered ore, and a method for manufacturing the carbon material for sintering. Background Art

[0002] The sintering process of iron ore is a process of sintering and solidifying a sintering raw material mixed with an iron source as iron ore, fluxes, limestone and other auxiliary raw materials, and a carbon material for sintering as a solid fuel by using the combustion heat of the carbon material for sintering in a sintering machine. As the carbon material for sintering, although coke powder is generally used, considering risks such as price fluctuations of raw material carbon and malfunctions of coke manufacturing equipment, anthracite other than coke powder is sometimes used.

[0003] On the other hand, due to the recent increase in environmental protection awareness and considering the reduction of environmental load, the diversification of carbon materials for sintering is developing. As the carbon material for sintering, the use of carbon materials derived from biomass (hereinafter referred to as "biomass carbon") has begun to attract attention. Biomass carbon uses plants that absorb carbon dioxide in the atmosphere for growth as raw materials. That is, from the perspective of carbon neutrality, fuels using biomass carbon are evaluated as having zero emissions of carbon dioxide generated by combustion. Therefore, as the carbon material for sintering, the use of biomass carbon instead of the conventionally used coke powder has also begun to be studied.

[0004] Here, in Patent Document 1, a method is disclosed in which sub-bituminous coal or lignite pulverized so that 80% by mass or less becomes 10 mm or less is charged into the upper part or the bottom part of the carbon charged for coke production in a coke oven chamber and carbonized. Moreover, it is also disclosed in this document that waste plastics and woody biomass can be mixed as a part of sub-bituminous coal and lignite.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent No. 5532574 Gazette Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] Biomass carbon has the characteristic of a low combustion start temperature. Compared with coke powder from fossil fuels commonly used in the sintering process, biomass carbon has a large surface area because it is porous. Therefore, even in a state of low combustion start temperature, a fast combustion rate can be obtained due to the large contact area with the atmosphere.

[0010] The combustion reaction of the carbon material for sintering is a gas-solid reaction. Additionally, the carbon material for sintering reacts with oxygen in the surrounding gas and burns. Moreover, in a gas-solid reaction under conditions where gas is flowing, such as in a sintering process, a region called a gas boundary layer, which is a thin layer, is generated on the surface of the carbon material for sintering. The gas boundary layer is not affected by the turbulence of the outside gas and can maintain laminar flow. Oxygen invades and diffuses from the outside of the gas boundary layer into the gas boundary layer and reaches the surface of the carbon material for sintering, whereby the carbon material for sintering burns.

[0011] Here, when the combustion rate of the carbon material for sintering is high, even when the oxygen concentration in the surroundings is high, the oxygen consumption rate at the surface due to the combustion of the carbon material for sintering becomes faster than the oxygen supply rate caused by the diffusion of oxygen in the gas boundary layer, and the oxygen concentration in the gas boundary layer decreases. As a result, incomplete combustion of the carbon material for sintering occurs, and the amount of carbon monoxide generated increases.

[0012] That is, when the combustion rate of the carbon material for sintering is high, a part of the combustion heat of the carbon material for sintering is discharged in the form of carbon monoxide, so the reaction heat supplied to the sintering process decreases. That is, the combustion heat for sintering the sintering raw materials (iron source and auxiliary raw materials) is insufficient, resulting in a decrease in the yield in the production of sintered ore. Therefore, when using biomass carbon with a high combustion rate as the carbon material for sintering, there is a problem of a decrease in the yield of sintered ore due to insufficient combustion heat for sintering the sintering raw materials.

[0013] In addition, a large amount of tar, which is a by-product, is generated (volatilized) from biomass carbon through a thermal reaction. The generated (volatilized) tar adheres to the inside of pipes, filters for dust removal, impellers of blowers, etc. in the sintering machine, so there is also a problem of causing equipment failures.

[0014] The present invention has been completed in view of the above circumstances, and an object thereof is to provide a carbon material for sintering, a sintered ore, and a method for manufacturing a carbon material for sintering that can reduce the environmental load in the production of sintered ore, and can suppress a decrease in the yield of sintered ore and equipment failures.

[0015] Means for Solving the Problem

[0016] The main configuration of the present invention for solving the above problems is as follows.

[0017] [1] A carbon material for sintering, which is a carbon material for sintering used in the sintering process of iron ore, wherein the carbon material for sintering has coal and biomass carbon as compounding materials, and the ratio (mass%) of the fixed carbon of the biomass carbon to the fixed carbon of the coal and the biomass carbon after dry distillation is greater than 0 and 30 mass% or less, and the content of the volatile component after dry distillation is 5.0 mass% or less.

[0018] [2] Sintered ore, which is manufactured using the carbon material for sintering described in [1].

[0019] [3] Method for manufacturing a carbon material for sintering, which is a method for manufacturing a carbon material for sintering used in the sintering process of iron ore. In this method, an agglomerate is formed using coal and biomass carbon as blending materials, and the aforementioned agglomerate is carbonized by maintaining it at a temperature of 1000 °C or higher for 6 hours or more in a nitrogen atmosphere.

[0020] [4] The method for manufacturing a carbon material for sintering according to [3], wherein the carbonization is carried out using a coke oven.

[0021] Advantages of the Invention

[0022] According to the present invention, in the manufacture of sintered ore, it is possible to reduce the environmental load, and to suppress a decrease in the yield of sintered ore and equipment failures. Detailed Embodiments

[0023] Hereinafter, the present invention will be described by way of embodiments of the present invention.

[0024] The carbon material for sintering used in the sintering process of iron ore uses coal and biomass carbon as blending materials. Compared with the conventional blending that only blends coal formed from coke powder, anthracite, etc., by partially replacing (blending) biomass carbon, it is possible to reduce the relative use of coal and reduce the environmental load.

[0025] Moreover, for the carbon material for sintering, the ratio (mass%) of the fixed carbon of biomass carbon to the fixed carbon of coal and biomass carbon after carbonization is set to be greater than 0 and 30 mass% or less. Here, "fixed carbon" means the carbon component contained in the agglomerate after carbonizing the agglomerate using coal and biomass carbon as blending materials. The more the blending ratio of biomass carbon, the more the relative blending ratio of coal decreases, and the more the environmental load can be reduced. However, as the amount of biomass carbon with a fast combustion rate increases, the yield of sintered ore decreases. Therefore, by setting the ratio (mass%) of the fixed carbon of biomass carbon to be greater than 0 and 30 mass% or less, it is possible to suppress a decrease in the yield of sintered ore. Moreover, it is possible to maximize the ratio of the fixed carbon of biomass carbon while suppressing a decrease in the yield of sintered ore, and to minimize the ratio of the fixed carbon of coal, thereby maximizing the reduction of carbon dioxide emissions.

[0026] Here, in the biomass carbon, a large number of pores remain from the vascular bundles of the plants used as raw materials, and moisture in the air is adsorbed in the pores. Moreover, due to the thermal reaction in the sintering process, along with the volatilization of moisture and the like remaining in the pores, a large amount of tar as a by-product also volatilizes. Therefore, it is necessary to pre-mix coal and biomass carbon as carbon materials for sintering to form an agglomerate, and then subject the agglomerate to carbonization to completely remove volatile components such as moisture contained in the biomass carbon. However, the pores inherent in the biomass carbon are complex and numerous, so it is difficult to completely remove the volatile components by carbonization.

[0027] Therefore, for the carbon material for sintering, the carbonization of the agglomerate containing coal and biomass carbon is carried out until the content of volatile components (mass%) of the carbon material for sintering after carbonization becomes 5.0 mass% or less. Thus, even if the carbon material for sintering is used in the sintering process, the volatilization of moisture and the like accompanying the thermal reaction can be suppressed, and the volatilization of tar can also be suppressed. As a result, equipment failures caused by the adhesion of tar and the like can be suppressed.

[0028] Regarding the manufacturing method of the carbon material for sintering used in the sintering process of iron ore, first, an agglomerate is formed using coal and biomass carbon as the blending materials. Then, the agglomerate is carbonized at a temperature of 1000 °C or higher for 6 hours or more in a nitrogen atmosphere. The carbonization can be carried out using a coke oven. By carrying out the carbonization of the carbon material for sintering using a coke oven, there is no need to set up special equipment for carrying out the carbonization of the carbon material for sintering, and the effect of reducing equipment costs can be obtained.

[0029] The sintering process of iron ore is carried out using a sintering machine. Regarding the sintering process, first, the sintering raw material obtained by adding auxiliary raw materials such as fluxes and the carbon material for sintering to the iron source of the iron ore is continuously charged onto the sintering machine to form a sintering bed. Then, after igniting the carbon material for sintering at the upper end of the sintering bed, the exhaust gas is sucked from the lower end, whereby the combustion of the carbon material for sintering spreads from the upper end to the lower end of the sintering bed, and the combustion heat causes the combustion reaction of the iron source and the auxiliary raw materials, and the sintering raw material is sintered and solidified. The suction of the exhaust gas from the lower end of the sintering bed is carried out using a blower. The sucked exhaust gas flows through the pipeline via the blower, and is discharged from the chimney after passing through a dust collector, a desulfurization device, a denitration device, etc.

[0030] Examples

[0031] Hereinafter, examples using the carbon material for sintering and the manufacturing method of the carbon material for sintering according to the present embodiment will be described.

[0032] <Example 1> As biomass carbon, a biomass material of wood chips (hereinafter referred to as "biomass A") and a biomass material of coconut shells (hereinafter referred to as "biomass B") were prepared, and each was mixed with coal in a specified ratio and subjected to carbonization using a carbonization furnace (coke oven) to produce a carbon material for sintering. The carbonization was carried out under the condition of maintaining at a temperature of 1000 °C or higher for 6 hours or more in a nitrogen atmosphere. The proportion (mass%) of the fixed carbon of the biomass carbon relative to the fixed carbon of the carbonized coal and biomass carbon, and the volatile component content (mass%) of the carbon material for sintering were measured based on the JIS standard "Industrial Analysis Method for Coals and Cokes" (JIS M8812).

[0033] Next, as the sintering process, iron ore (iron source) and limestone (auxiliary raw material) were mixed with the produced carbon material for sintering and return fines, and a certain amount of water was added for granulation. Then, the granulated sintering raw material was charged into a sinter pot test device for a sintering test. The sinter pot test device has: a sinter pot with a diameter of 300 mm and a height of 600 mm; an ignition furnace; and exhaust equipment such as a wind box and a blower. In the sinter pot test device, a test simulating an actual sintering machine can be carried out in such a way that the combustion reaction proceeds from the upper layer of the raw material layer of the sintering raw material and the combustion reaction reaches the lower layer of the raw material layer to complete the firing. Moreover, in the sintering test, after the charged sintering raw material was sintered to produce sinter, a drop test was carried out in which the sinter was dropped 4 times from a height of 2 m. For the sinter after dropping, the sinter with a size of 5 mm or more remaining was regarded as the finished product, and the proportion of the finished product was evaluated as the finished product rate (%). In addition, for the evaluation of the finished product rate (%), the following three-stage evaluation (finished product rate evaluation) was carried out: it was evaluated as "good (○)" when it was 70% or more, "ordinary (△)" when it was 65% or more and less than 70%, and "poor (×)" when it was less than 65%. It should be noted that when biomass carbon is not incorporated into the carbon material for sintering, the finished product rate (%) mostly shows a value of about 80%.

[0034] In addition, the sinter pot test device is equipped with a blower in the same way as an actual sintering machine. Therefore, after the sintering test, the adhesion state of tar in the blower was confirmed, and as an evaluation of the exhaust equipment, the following two-stage evaluation was also carried out: it was evaluated as "poor (×)" when it became a state where cleaning was required or equipment failure occurred, and "no problem (○)" in other states.

[0035] [Table 1]

[0036]

[0037] [Table 2]

[0038]

[0039] Comparative Examples 1 and 6 in Tables 1 and 2 are examples showing a sintering process using a carbon material for sintering that does not incorporate biomass carbon. Comparative Examples 5 and 10 are examples showing a sintering process using only biomass carbon as the carbon material for sintering. Therefore, for Comparative Examples 5 and 10, the carbon dioxide emission amount is set to "0". The blending ratio (mass %) of Biomass A or Biomass B in Tables 1 and 2 refers to the ratio (mass %) of the mass of biomass carbon to the mass of the agglomerate in the state before the carbon material for sintering is carbonized, that is, in the state of forming an agglomerate with coal and biomass carbon as blending materials.

[0040] As shown in Table 1, in Invention Examples 1 to 3 where Biomass A (wood chips) is used as biomass carbon and the proportion of fixed carbon in Biomass A after carbonization is greater than 0 and 30 mass % or less, it was confirmed that the yield evaluation was "good (○)". In this case (Invention Examples 1 to 3), it was confirmed that the carbon dioxide emission amount (kg-CO2 / t-sinter) could be suppressed by up to about 20%. In addition, in Invention Examples 1 to 3, it was confirmed that the volatile component content (mass %) after carbonization was 5.0 mass % or less. Therefore, it was confirmed that the exhaust equipment evaluations for Invention Examples 1 to 3 were all "good (○)".

[0041] It should be noted that in Comparative Examples 2 to 5 where the proportion of fixed carbon in Biomass A after carbonization was 40 mass % or more, it was confirmed that the yield evaluation was "poor (×)". In Comparative Examples 2 to 4, not only was the yield evaluation in the "poor (×)" state, but also the carbon dioxide emission amount increased in order to maintain the production volume of sinter. In addition, in Comparative Examples 2 to 5, it was confirmed that the volatile component content (mass %) after carbonization was a value greater than 5.0 mass %, and the exhaust equipment evaluation was "poor (×)".

[0042] In addition, as shown in Table 2, in Invention Examples 4 to 6 where Biomass B (coconut shell) is used as biomass carbon and the proportion of fixed carbon in Biomass B after carbonization is greater than 0 and 30 mass % or less, it was confirmed that the yield evaluation was "good (○)" or "ordinary (△)". In this case (Invention Examples 4 to 6), it was confirmed that the carbon dioxide emission amount (kg-CO2 / t-sinter) could be suppressed by up to about 15%. In addition, in Invention Examples 4 to 6, it was confirmed that the volatile component content (mass %) after carbonization was 5.0 mass % or less. Therefore, the exhaust equipment evaluations for Invention Examples 4 to 6 were all "good (○)".

[0043] Note that in Comparative Examples 7 to 10 where the proportion of fixed carbon in the biomass B after carbonization is 40% by mass or more, it was confirmed that although the carbon dioxide emission decreased, the yield was evaluated as "poor (×)". Moreover, it was confirmed that the content of volatile components (mass%) after carbonization was a value greater than 5.0 mass%, and the exhaust equipment evaluation was all "poor (×)".

[0044] From the above, it can be confirmed that as the carbon material for sintering used in the sintering process, in the case of using coal and biomass carbon as the compound materials, the proportion (mass%) of the fixed carbon of biomass carbon relative to the fixed carbon of coal and biomass carbon after carbonization is greater than 0 and 30% by mass or less, and the content of volatile components (mass%) after carbonization is 5.0% by mass or less. Thus, it is possible to reduce the environmental load and suppress the decrease in the yield of sinter and equipment failures.

[0045] <Example 2> As the biomass carbon, a biomass material of wood chips (biomass A) was prepared. The blending ratio (mass%) of the biomass carbon (biomass A) was set to 30%, and the blending ratio (mass%) of coal was set to 70% to form a briquette. Then, in a carbonization furnace (coke oven), under a nitrogen atmosphere, carbonization was carried out under various conditions in which the temperature and carbonization time were changed. During carbonization, the heating rate and the cooling rate were set to 10 °C / minute.

[0046] The proportion (mass%) of the fixed carbon of biomass carbon relative to the fixed carbon of coal and biomass carbon after carbonization, and the content of volatile components (mass%) of the carbon material for sintering were measured based on the JIS standard "Industrial Analysis Method for Coals and Cokes" (JIS M8812) in the same manner as in the previous examples. For the carbon material for sintering after carbonization, the proportion (mass%) of the fixed carbon of biomass carbon relative to the fixed carbon of coal and biomass carbon was 30% by mass. For the evaluation of the content of volatile components (mass%), it was evaluated as "good (○)" when it was 5.0% by mass or less, and as "poor (×)" when it was greater than 5.0% by mass.

[0047] [Table 3]

[0048] Temperature (°C) Carbonization time (H) Content of volatile components after carbonization (mass%) Evaluation Comparative Example 11 800 3 7.7 × Comparative Example 12 800 6 7.1 × Comparative Example 13 1000 3 6.1 × Inventive Example 7 1000 6 5.0 ○ Comparative Example 14 1200 3 5.2 × Inventive Example 8 1200 6 4.3 ○

[0049] As shown in Table 3 (Results of Examples Using Biomass A), in the case of using biomass A as the biomass carbon (Inventive Examples 7 to 8), all the examples were carbonized under the condition of maintaining at a temperature of 1000 °C or higher for 6 hours or more, whereby the content of volatile components (mass%) after carbonization could be made 5.0% by mass or less.

[0050] It should be noted that as the conditions for dry distillation, when the temperature is less than 1000 °C or when the holding time for dry distillation is less than 6 hours (Comparative Examples 11 to 14), it was confirmed that the content of volatile components after dry distillation (mass %) could not be made 5.0 mass % or less.

Claims

1. Carbon material for sintering, which is a carbon material for sintering used in the sintering process of iron ore. Among them, The carbon material for sintering has coal and biomass carbon as compounding materials, The proportion (mass %) of the fixed carbon of the biomass carbon relative to the fixed carbon of the coal and the biomass carbon after carbonization is greater than 0 and 30 mass % or less, The content of volatile components after carbonization is 5.0 mass % or less.

2. Sintered ore, which is manufactured using the carbon material for sintering described in claim 1.

3. Manufacturing method of carbon material for sintering, which is a manufacturing method of carbon material for sintering used in the sintering process of iron ore. Among them, A agglomerate is formed with coal and biomass carbon as compounding materials, The agglomerate is carbonized by holding at a temperature of 1000 °C or higher for 6 hours or more in a nitrogen atmosphere.

4. The manufacturing method of carbon material for sintering according to claim 3, wherein, The carbonization is carried out using a coke oven.

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