Method for preparing charcoal materials

Abstract

The present invention provides a carbonaceous material which is used for the production of a sintered ore, and is capable of preventing troubles in the exhaust gas system caused by exhaust gas processing, the troubles including, for example, the generation of tar in pipes and the occurrence of white smoke in an electric dust collector. This carbonaceous material is a solid fuel for the production of a sintered ore, and has an electrical conductivity of 1.0 × 10-9 S / m or more and a volatile content (VM) of 15% or less. In cases where this carbonaceous material is composed of a plurality of kinds of carbonaceous materials, 80% or more of the plurality of kinds of carbonaceous materials have an electrical conductivity of 1.0 × 10-9 S / m or more at 80°C to 200°C, and the weighted average of the volatile contents (VM) is 15% or less.

Description

Technical Field

[0001] The present invention relates to a carbon material as a solid fuel used in the production of sintered ore.

Background Art

[0002] In the production process of sintered ore, a mixture of iron ore, flux, and a carbon material as a solid fuel is sintered in a sintering machine using the combustion heat of the carbon material to produce sintered ore. Generally, pulverized coke is used as the carbon material, but anthracite or the like other than pulverized coke may also be used as a risk dispersion against price fluctuations of raw coal and troubles in coke production facilities.

[0003] On the other hand, in recent years, due to the increasing awareness of environmental protection, apart from the idea of risk dispersion, diversification of carbon materials has been progressing with the intention of reducing the environmental burden. As an example, in Patent Document 1, a carbon material for producing sintered ore assuming sub-bituminous coal or lignite has been proposed. This carbon material has properties such that the reaction start temperature is 550 °C or lower, the volatile matter (VM) is 1.0% or more, the atomic ratio of hydrogen to carbon (H / C) is 0.040 or more, and the pore volume with a pore diameter of 0.1 to 10 μm measured by mercury intrusion porosimetry is 50 mm 3 / g or more. Further, in Patent Document 2, when using 30% or more of high crystal water iron ore containing 4.0 mass% or more of crystal water, the use of a sintering raw material containing 10 mass% or more of a solid fuel with a combustion start temperature of less than 450 °C has been proposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the use of carbon materials described in Patent Document 1 and the use of solid fuels described in Patent Document 2 focused on the productivity of sintered ore and NOx, and did not take into account the effects of exhaust gas treatment. Therefore, the use of carbon materials described in Patent Document 1 and the use of solid fuels described in Patent Document 2 could not prevent problems in the exhaust gas system caused by exhaust gas treatment, such as tar generation in piping and white smoke generation in electrostatic precipitators.

[0006] The object of the present invention is to solve the above-mentioned problems and provide a carbon material that, when used in the production of sintered ore, can prevent problems in the exhaust gas system caused by exhaust gas treatment, such as tar generation in piping and white smoke generation in electrostatic precipitators. [Means for solving the problem]

[0007] The present invention relates to a carbon material as a solid fuel for the production of sintered ore, and to a method for preparing a carbon material consisting of multiple types of carbon materials. The volatile content (VM) of each individual carbon material of multiple types is measured according to the measurement method of JIS M8812, and the electrical conductivity of each carbon material is determined as the reciprocal of the electrical resistivity measured according to JIS B9915. The weighted average of the volatile matter (VM) of multiple types of carbon materials is 15% or less, and the electrical conductivity of multiple types of carbon materials is 1.0 × 10⁻⁶ -9 This is a method for preparing charcoal material, characterized by adjusting it to contain 80% or more of material with a density of S / m or higher. [Effects of the Invention]

[0009] The carbon material used in the production of sintered ore according to the present invention prevents the adhesion of thermal decomposition products generated during combustion and substances generated by subsequent gas-phase reactions to piping and equipment in the exhaust gas system, as well as their failure, by using carbon material within the scope of these constraints. Furthermore, it prevents a decrease in dust collection efficiency and the generation of white smoke when dust in the exhaust gas generated during the use of the carbon material is collected by an electrostatic precipitator. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing an example of a manufacturing facility for sintered ore using carbon material according to this embodiment. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described in detail below. The following embodiments are illustrative examples of devices and methods for realizing the technical concept of the present invention, and do not 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 described in the claims.

[0012] <Regarding the manufacturing equipment for sintered ore using carbon material for sintered ore production according to the present invention> Figure 1 is a schematic diagram showing an example of a sintered ore manufacturing facility 1 using carbon material according to this embodiment. The sintered ore manufacturing facility 1 includes a drum mixer 2 which is a granulator, a sintering machine 3, a crusher 4, a cooler 5, and a sieving device 6. Sintering raw materials, including iron-containing raw materials, auxiliary raw materials, and agglomerating agents such as carbon material and coke powder, are granulated in the drum mixer 2 with the addition of granulation water. The granulated sintering raw materials are then transported to the sintering machine 3.

[0013] The sintering machine 3 is, for example, a Dwight-Loyd type sintering machine. The sintering machine 3 includes a sintering material supply device 11, an endless mobile pallet trolley 12, an ignition furnace 13, and a window box 14. The granulated sintering material is charged from the sintering material supply device 11 to the pallet trolley 12, forming a charged layer of sintering material. The ignition furnace 13 ignites the binder contained in the surface layer of the charged layer, and air in the charged layer is drawn downward through the window box 14, causing the combustion molten zone in the charged layer to move downward. This movement of the combustion molten zone causes the charged layer to be sintered and become a sintered cake.

[0014] When drawing air downwards from the charging bed through the window box 14, oxygen-enriched air enriched with gaseous fuel and / or oxygen may be supplied from above the charging bed. The gaseous fuel is any combustible gas selected from blast furnace gas, coke oven gas, converter gas, city gas, natural gas, methane gas, ethane gas, propane gas, and mixtures thereof.

[0015] The sintered cake is crushed by a crusher 4 and cooled in a cooler 5. The crushed sintered cake is sieved in a sieving device 6 into sintered ore with a particle size of 5 mm or larger and return ore with a particle size of less than 5 mm. The return ore is used again as a sintering raw material. In this way, sintered ore is produced.

[0016] <Regarding the carbon material used in the production of sintered ore according to the present invention> In diversifying charcoal materials to reduce environmental impact, biomass-derived charcoal (hereinafter referred to as biomass charcoal) is attracting attention. Since biomass absorbs carbon dioxide during the growth of the plants that serve as its raw material, fuels using biomass can be counted as having no carbon dioxide emissions outside the system from the perspective of carbon neutrality. For this reason, the use of biomass charcoal is being considered even in iron ore sintering processes that normally use powdered coke. A characteristic of biomass charcoal is that its combustion start temperature is lower than that of coke (600-800°C), generally below 550°C. Furthermore, it is known that the isothermal decomposition reaction of biomass is greatly influenced by the plants that serve as its raw material, and even when grouped together with heat-treated biomass charcoal, its properties differ greatly, and it cannot be categorized solely by combustion start temperature.

[0017] In the sintering process in the sintering machine 3 described above, flux and carbon material are added to iron ore and continuously charged onto the sintering machine 3 to form a sintering bed consisting of a charged layer of sintering raw materials. After ignition at the top of the sintering bed, exhaust gas is drawn in from the bottom, causing the combustion of the carbon material to propagate from the top to the bottom of the bed. This heat is used to react and agglomerate the iron ore and flux. Exhaust gas is drawn in from the bottom using a blower, and the drawn exhaust gas passes through a duct, a dust collector, and desulfurization / denitrification equipment before being discharged from the chimney.

[0018] When heating biomass, hydrocarbons having benzene rings more than naphthalene are called tar, and biomass has a very large amount of this tar generated. A large amount of generated tar adheres to pipes, dust filters for dust removal, impellers of blowers, etc., which may cause problems. Therefore, in the selection of biomass charcoal, it is necessary to keep the tar content generated, that is, the volatile matter (VM) generated by pyrolysis, low. Note that VM conforms to the measurement method of JIS M8812.

[0019] In addition, a lot of used charcoal materials are included in the dust in the exhaust gas, and they are recovered in an electrostatic precipitator. When collecting dust with low electric conductivity using an electrostatic precipitator, the surface of the dust collecting electrode is covered with dust with low electric conductivity, making it difficult to remove by hammering or the like. Also, sparks due to dielectric breakdown occur in the coated dust layer, inducing white smoke troubles in the electrostatic precipitator. Therefore, it is necessary to add biomass charcoal to be used with a certain level or more of electric conductivity as a condition. Note that for electric conductivity, the reciprocal of the electrical resistivity measured by JIS B9915 was used.

[0020] Based on the above premises, in the present invention, in order to suppress the generation of tar during the production of sintered ore and suppress the white smoke trouble of the electrostatic precipitator due to the exhaust gas generated during the production of sintered ore, the electric conductivity at 80°C to 200°C is 1.0×10 ―9 S / m or more, and the volatile matter (VM) is 15% or less.

[0021] In the charcoal material used for the production of sintered ore of the present invention, as a specific method for adjusting the electric conductivity and volatile matter, select those that satisfy the volatile matter (VM) and electric conductivity when selecting the charcoal material, or lower the volatile matter (VM) by carbonization treatment or the like. methods can be considered. Also, when using multiple types of charcoal materials, examples include adjusting the blending so that the weighted average of the volatile matter (VM) satisfies the above conditions and the electric conductivity contains 80% or more of those that satisfy the above conditions. Hereinafter, the measurement methods of the electric conductivity and volatile matter in the present invention will be described in more detail.

[0022] (Regarding the method of measuring electrical conductivity) For measuring electrical conductivity, the electrical resistivity obtained according to the parallel plate electrode method (JIS B9915) is used. The reciprocal of the electrical resistivity obtained according to the parallel plate electrode method (JIS B9915) is used as the electrical conductivity.

[0023] (Regarding the measurement method of volatile matter (VM)) Volatile matter (VM) is measured in accordance with JIS M8812. Specifically, the sample is placed in a lidded crucible and heated at 900°C for 7 minutes, avoiding contact with air. The mass fraction (%) of the loss during heating relative to the sample is then determined, and the water content, which is quantified simultaneously, is subtracted from this to obtain the volatile matter (VM). [Examples]

[0024] Batch-type sintering tests were conducted using several carbon materials. Table 1 shows the properties of the carbon materials used. Here, volatile matter (VM) was measured according to JIS M8812, and the reciprocal of the electrical resistance value measured according to JIS B9915 was used for electrical conductivity.

[0025] [Table 1]

[0026] Two batch-type sintering tests were conducted on the single and combined carbon materials listed in Table 1. The first involved a maximum of 100 continuous tests, investigating the number of times the blower's current (normal operation) exceeded the upper limit of 75A, with a rated current of 60A. The second involved treating the exhaust gas from the batch-type sintering test using a small dust collector adjusted to an electric field strength of 3.4kV / cm, similar to that of a real machine, and determining whether the adhering dust could be hammered away. Table 2 shows the test conditions, including the carbon material blending ratio, the weighted average of VM, and the results from the two evaluation methods. The same ore raw material was used for both tests.

[0027] [Table 2]

[0028] Table 2 shows powdered coke commonly used in sintering as a reference example. With a VM of 0.7%, the upper limit current was not exceeded even after 100 tests, and dust hammering was possible. Examples 1 and 2, and Comparative Examples 1 and 2, are all classified as anthracite. However, while anthracite A with a VM of 14.7% in Example 1 was able to withstand 100 tests, anthracite B with a VM of 15.6% in Comparative Example 1 exceeded the upper limit current after 33 tests, and furthermore, dust removal by hammering was difficult. Compared to Example 1, Example 2 had a lower VM and a higher electrical conductivity, and was also able to withstand 100 tests, and dust removal by hammering was possible. On the other hand, Comparative Example 2 had a VM that was not significantly different from Example 2, but there was a large difference in electrical conductivity, and although 100 tests were possible, dust removal by hammering was difficult. Furthermore, in Comparative Example 3, which used only biomass with 77.0% VM, the material became unusable after 17 cycles, but dust removal by hammering was possible. In Example 3 and Comparative Example 4, powdered coke and anthracite B, which could not be fired 100 times on its own and whose dust removal by hammering was difficult, were blended. In Example 3, where powdered coke was 80% and the weighted average VM was 3.7%, 100 tests were possible, and dust removal by hammering was also possible. On the other hand, in Comparative Example 4, where powdered coke was 70% and the weighted average VM was 5.2%, although the number of tests reached 100, dust removal by hammering was difficult. In Example 5 and Comparative Example 5, all of the charcoal materials used in this study were blended. In Example 5, where the weighted average VM was 12.6%, 100 tests were possible, and dust removal by hammering was also possible. On the other hand, in Comparative Example 5, where the weighted average of VM was 9.7%, 100 tests were possible, but dust hammering removal was difficult. [Industrial applicability]

[0029] The carbon material used in the production of sintered ore according to the present invention can prevent problems in the exhaust gas system caused by exhaust gas treatment, such as tar generation in piping and white smoke generation in electrostatic precipitators, and is therefore industrially useful. [Explanation of Symbols]

[0030] 1. Manufacturing equipment for sintered ore 2 Drum Mixer 3. Sintering machine 4. Crusher 5. Cooler 6 Sieving device 11 Raw material supply device 12 pallet trolleys 13 Ignition furnace 14 Window Box

Claims

[Claim 1] A method for preparing carbon material as a solid fuel for the production of sintered ore, comprising a plurality of types of carbon material, The volatile matter (VM) of each type of carbon material is measured according to the measurement method of JIS M8812, and the electrical conductivity of each carbon material is determined as the reciprocal of the electrical resistivity measured according to JIS B9915. A method for preparing charcoal materials, characterized by adjusting the weighted average of the volatile matter (VM) of multiple types of charcoal materials to be 15% or less, and by adjusting the charcoal materials so that 80% or more of the multiple types of charcoal materials have an electrical conductivity of 1.0 × 10⁻⁹ S / m or higher.

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