TW202325859A - Method for producing sintered ore - Google Patents

Abstract

The present invention provides a method for producing a sintered ore, wherein a sintering starting material which contains a flux and iron ore that is mainly composed of hematite is agglomerated with use of microwaves, the method being capable of efficiently heating the sintering starting material in a shorter time. The present invention provides a method for producing a sintered ore by agglomerating a sintering starting material which contains a flux and an iron ore powder that is mainly composed of hematite, wherein: the sintering starting material contains 3.0% by mass or more of magnetite in terms of FeO; and the sintering starting material is irradiated with microwaves so as to be heated to 1000 DEG C or higher.

Description

How to make sintered ore

The present invention relates to a method for producing sintered ore by using microwaves to heat sintered raw materials.

In recent years, for the purpose of reducing the environmental load, especially the reduction of CO ₂ emissions, the development of heating methods for sintering raw materials that do not involve the combustion of coke has been promoted in the production process of sintered ore in the iron and steel industry. As one of the heating methods of sintering raw materials without combustion, there is a method of irradiating microwaves. A microwave is a type of electromagnetic wave, and is an electromagnetic wave having a frequency in the range of 300 MHz to 300 GHz. It is known that microwaves have the effect of imparting energy to a dielectric body to heat it, and particularly a substance with a high dielectric constant tends to absorb the energy of irradiated microwaves.

Recently, the development of technology for producing sintered ore from iron ore mainly composed of hematite using microwaves is expected.

Patent Document 1 discloses a method of irradiating microwaves at a frequency of 20 GHz to 30 GHz in order to heat hematite and goethite, which are components of iron ore, for the purpose of reduction of iron ore. It is disclosed that even an iron ore raw material mainly composed of hematite or goethite can be heated or sintered if it is a high-frequency (short wavelength) microwave of 20 GHz to 30 GHz.

Patent Document 2 discloses a method of improving the quality and recovery rate of sintered ore by irradiating the surface with microwaves after exiting the ignition furnace in a conventional sintering machine utilizing combustion reaction, thereby supplying heat to the surface.

Patent Document 3 discloses that in the production of sintered ore by microwave irradiation, using a sintered raw material of an unspecified type of iron oxide and irradiating microwaves of 2.45 GHz, the sintering rate increases in proportion to the irradiation time, and is completed within 20 minutes. sintering. [Prior art literature] [Patent Document]

Patent Document 1: Japanese Patent Laid-Open No. 2011-184718 Patent Document 2: Japanese Patent Application Publication No. 2018-505965 Patent Document 3: Japanese Patent Laid-Open No. 07-268494

[Problem to be Solved by the Invention]

However, in Patent Document 1, since heating is performed using high-frequency microwaves of 20 GHz to 30 GHz, a dedicated large-scale gyrotron device is required, and the investment in equipment becomes too large in the process.

In Patent Document 2, microwaves are used for thermal compensation of the surface of the ignited sintered raw material, and the heat energy source during sintering is the combustion of carbon, so there is a problem of CO ₂ generation.

In Patent Document 3, since iron ore of which iron oxide type is not distinguished is used as a raw material for sintering, there is a problem that heating by microwave irradiation requires long-term irradiation and is inefficient.

As described above, in the sintering step, as an alternative to heating by coke combustion, several technical developments using microwave heating have been studied. However, on the other hand, the prior art has a problem that, when using iron ore mainly composed of hematite, a large-scale microwave generator or long-term microwave irradiation is required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing sintered ore that efficiently converts sintered ore in a shorter time even when microwaves with a frequency of 2.4 GHz to 2.5 GHz are used. Sintered ore is produced by heating a sintered raw material mainly composed of hematite. [Means to solve the problem]

The inventors of the present invention have made intensive studies in order to solve the above-mentioned problems, and as a result, found a method for producing sintered ore in which a certain amount of The sintering raw material including the raw material of magnetite as a dielectric body is sintered by heating by irradiating microwaves. The present invention was completed based on further research based on these findings, and the present invention is constituted as follows.

[1] A method for producing sintered ore, comprising agglomerating a sintered raw material comprising powdered iron ore mainly composed of hematite and a flux (flux), the sintered raw material comprising FeO The sintering raw material is heated to 1000° C. or higher by irradiating microwaves to 3.0 mass % or more of magnetite. [2] The method for producing sintered ore according to [1], wherein the sintered raw material is mixed with one or more of iron ore including magnetite, sintered ore, and dust generated in an ironworks. [3] The method for producing sintered ore according to [1], wherein the flux is one or more of limestone, quicklime, slaked lime, and slag generated in ironworks. [4] The method for producing sintered ore according to [2], wherein the flux is one or more of limestone, quicklime, slaked lime, and slag generated in ironworks. [5] The method for producing sintered ore according to any one of [1] to [4], wherein the frequency of the microwave is 2.4 GHz to 2.5 GHz. [Effect of the invention]

According to the present invention, since the sintered raw material containing 3.0% by mass or more of magnetite in terms of FeO can obtain high dielectric heating performance, the sintered raw material can be efficiently heated by microwaves in a shorter time, and it is possible to manufacture Sinter.

Hereinafter, embodiment of the manufacturing method of the sintered ore of this invention is demonstrated in detail, referring drawings. In addition, embodiment shown below is an example of embodiment of this invention, and this invention is not limited to these embodiment, and is interpreted.

[Sinter manufacturing equipment] FIG. 1 is a schematic diagram showing an example of a sintered ore manufacturing apparatus capable of implementing the sintered ore manufacturing method of this embodiment. The sintering raw material is loaded into the sintering raw material supply device 1 . The sintering raw material is continuously charged from the sintering raw material supply device 1 into an annular movable pallet (pallet) 2 to form a charging layer of the sintering raw material. Microwaves are irradiated from the microwave irradiation device 3 to heat the loaded layer of the sintering raw material, and the sintering raw material is agglomerated by liquid phase sintering to produce sintered ore.

[Sintering raw material] The raw materials for sintering include iron ore as an iron source and a flux functioning as a flux. Dust, sintered ore, and silica generated in ironworks may also be included in the sintering raw materials.

In order to further contain magnetite in an appropriate ratio in the raw material for sintering, one or more of iron ore containing magnetite, sintered ore containing magnetite, and dust generated in ironworks may be mixed. The blending of an appropriate ratio means that the magnetite is 3.0% by mass or more in terms of FeO. When the magnetite is less than 3.0% by mass in terms of FeO, it is not preferable to use microwaves with a frequency of 2.4 GHz to 2.5 GHz since long-term irradiation is required for heating to a predetermined temperature. Moreover, it is preferable that magnetite is 10.0 mass % or less in conversion of FeO. When the compounding ratio exceeds 10.0% by mass in terms of FeO, the compounded amount of raw materials other than iron ore containing hematite as a main component will increase, and thus the raw material cost for sintering will increase. A more preferable range is 4.0 mass % or more and 8.0 mass % or less. In addition, it is preferable that the sintered raw material is not formed into a block by granulation or press molding in advance. This is because, when an agglomerated object is used as a heating object, microwaves attenuate with the penetration distance, and the heating efficiency inside the agglomerated object may decrease. In addition, in the case of non-agglomeration, unlike the general sintering method using coke, there is an advantage that air supply is not required, and in the case of using moisture to form agglomerates during granulation or molding, there is a need for excess due to the evaporation heat of moisture. The disadvantage of heat.

[Iron Ore] The main component of iron ore is iron oxide, including hematite (Fe ₂ O ₃ ) and magnetite (magnetite, Fe ₃ O ₄ ). In this embodiment, powdery iron ore having a particle size of 8 mm or less is used as iron ore.

[Hematite] Hematite (hematite, Fe ₂ O ₃ ) is an iron oxide commonly used as a main raw material in the blast furnace process. The color of hematite is reddish brown or black, and it is widely distributed in rocks or soil. In the modern blast furnace method, hematite is mixed with flux or coke and sintered, thereby being used as sinter. However, the dielectric constant of hematite is low, and it is difficult to heat with microwaves of 2.4 GHz to 2.5 GHz if only hematite is used. In the present example, a raw material containing 75% by mass to 99% by mass of hematite in powdered iron ore mainly composed of hematite was used.

[Magnetite] Magnetite (magnetite, Fe ₃ O ₄ ) is a type of iron oxide. Basically, most of what can be collected worldwide is low quality. It has high dielectric heating performance and is easy to use microwave for heating.

The sintered ore in this embodiment is a sintered ore produced by sintering a sintered raw material containing iron-containing raw materials such as iron ore and a flux. Sintered ore contains magnetite. In addition, the returned ore is the sintered ore obtained in the production process of the sintered ore, which is smaller than the particle size of the product, and can be added to the sintered raw material again. In addition, dust is dust containing Fe generated in an ironworks, and for example, rust scraps, converter dust, and blast furnace dust can be used. In addition, silica can also be added to adjust the alkalinity.

[Fluxing agent] The fluxing agent in this embodiment is a raw material containing a substance that becomes CaO by heating such as limestone, quicklime, and slaked lime, or slag generated in an ironworks containing CaO, and exerts the flux in the sintering raw material. The role of iron oxides to melt and strengthen each other. It is preferable to prepare so that CaO/ _SiO2 of a sintering raw material may become 1.7-2.3 about the compounding quantity of a flux. The slag containing CaO generated in an ironworks refers to, for example, blast furnace slag generated in a blast furnace or steelmaking slag generated in a steelmaking step.

[sintering] The magnetite dispersed in the sintering raw material has high dielectric heating performance, so it is heated by microwaves, and the heated magnetite becomes a heat source to heat the whole sintering raw material. CaO and iron oxide in the flux are heated and melted, and powdery iron oxide is formed into lumps.

[heating temperature] The heating temperature of the raw materials for sintering by microwaves is set to 1000° C. or higher. As an upper limit of heating temperature, it is preferable to set it as 1350 degreeC or less. This is because, if the heating temperature is higher than 1350°C, hematite will turn into magnetite, and when the temperature drops and becomes hematite again, it will become extremely poor in reduction disintegration index (RDI). secondary hematite. Furthermore, it is more preferable to set heating temperature as 1200 degreeC or more and 1300 degreeC or less.

[Microwave irradiation device] Microwaves are a type of electromagnetic waves. According to the International Safety Management (ISM) or the radio wave law, the usable frequency band is limited in a device that does not have a large-scale leakage prevention device for electromagnetic waves.

A magnetron is a small, general-purpose microwave generator used in microwave ovens and the like, and the frequency of the magnetron includes a range of 2.4 GHz to 2.5 GHz, which is regarded as the fundamental frequency of ISM. Within the range specified by the ISM basic frequency, there are no strict restrictions to prevent interference with electromagnetic waves of other frequencies. Therefore, as long as microwaves in the range of 2.4 GHz to 2.5 GHz can be used, magnetrons that are cheaper than gyrotrons can be used. Pipes are used to make sintered ore, so the manufacturing equipment of sintered ore becomes cheap. Furthermore, if it is a microwave of 2.4 GHz to 2.5 GHz, it is not necessary to use a large-scale radio wave leakage prevention facility, so it is possible to manufacture sintered ore with small and inexpensive facilities.

As a form of the microwave irradiation apparatus in this embodiment, the tunnel type shown in FIG. 1 etc. are mentioned. However, it is not limited to the shapes exemplified in this embodiment as long as it has a shape and arrangement in which microwaves can be irradiated to the loading layer of the sintering raw material.

In the method for producing sintered ore according to this embodiment, even when microwaves of 2.4 GHz to 2.5 GHz are used, the sintered raw material can be heated to 1000° C. or higher in a short time of about 135 seconds by irradiating the microwaves. Liquid-phase sintering agglomerates sintered raw materials to produce sintered ore. If a microwave irradiation device with a microwave irradiation device length 6 of 40-50 m is used, the pallet speed can be made 20 m/min. Therefore, if the pallet width 4 is set to 4-5 m and the If it is set to 100 mm, a production capacity of 3 million tons/year of sintered ore can be obtained. In this way, if sintered ore can be produced by heating the sintered raw material using microwaves, the sintered ore can be produced without using powdered coke or the like, and the amount of CO ₂ generated accompanying the production of sintered ore can also be reduced. [Example]

[Experiment 1] First, experiments using magnetite reagents were performed. Formulations are shown in Table 1. The magnetite reagent is adjusted so that it becomes 3-10 mass % in conversion of FeO. The amount of magnetite in the raw material was determined by chemical analysis as the amount of FeO in the raw material. Table 1 shows the measured values.

[Table 1] Comparative example 1 Example 1 Example 2 Example 3 hematite ore 86.2 76.0 65.8 55.6 CaO reagent 10.5 10.5 10.5 10.5 _SiO2 reagent 3.3 3.5 3.7 3.9 Magnetite reagent 0.0 10.0 20.0 30.0 ※ FeO in the raw material 0.2 3.3 6.4 9.4 (quality%)

The CaO and _SiO2 in the raw materials are the amount used to simulate the actual operation by using reagents. SiO ₂ is prepared for the purpose of adjusting the composition of the slag in the blast furnace in the next step and controlling the alkalinity.

The mass of each sample was set to 36 g to 38 g in total, and a mortar and a pestle were used for mixing, and the mixture was sufficiently mixed until the color of the test body became uniform visually. Each sample was filled to a height of about 2 mm from the upper end of the alumina crucible 8 while lightly vibrating. The outline of the device is shown in FIG. 2 . An apparatus was used in which alumina crucible 8 was placed in microwave oven 7 and thermocouple 9 was incorporated at a position where thermocouple insertion height 12 was 18 mm. The inner diameter 10 on the upper surface side of the crucible was set to φ30 mm, and the crucible height 11 was set to 27 mm.

The frequency of the microwave was set to 2.45 GHz, and the output (wattage) of the microwave was controlled by a program so that the temperature increase rate became 1000° C./min during heating. After reaching 1300° C., the heating by the microwave was stopped, and the alumina crucible 8 was air-cooled together.

The experimental results are shown in Table 2. The presence or absence of sintering is judged based on the compressive strength and the rearrangement of pores. In addition, the compressive strength was measured using the precision electronic universal testing machine (Autograph) (speed: 1 mm/min). Since the compressive strength of sintered ore used as a raw material for a blast furnace is 2 MPa to 4 MPa, it is judged to be acceptable for practical use if it has a strength of 2 MPa or more.

[Table 2] Comparative example 1 Example 1 Example 2 Example 3 reached temperature (°C) 366 1090 1310 1260 Compressive strength (MPa) - 2.6 3.3 3.1 With or without sintering None (powder) Yes (blocky) Yes (blocky) Yes (blocky)

In Examples 1 to 3, the temperature of the raw materials for sintering was raised to 1000° C. or higher. The samples of Examples 1 to 3 immediately after the test were in a molten state. Fig. 3(b) to Fig. 3(d) show photographs of the upper surface of the crucible after heating in Examples 1 to 3 (upper figure) and observation photographs of the sintered structure (lower figure). As shown in FIG. 3 , it can be seen that Example 1(b), Example 2(c), and Example 3(d) were melted, and the sintering reaction proceeded in view of rearrangement of pores. In Examples 1 to 3, magnetite contained 3.3% by mass, 6.4% by mass, and 9.4% by mass in terms of FeO, respectively. Therefore, these raw materials are heated by microwaves with a frequency of 2.45 GHz, and the whole raw materials are sintered to a temperature of 1000°C or higher, and the sintering reaction proceeds to form agglomerates, thereby producing sintered ore with a predetermined strength.

In Comparative Example 1, the temperature rise stopped halfway, and microwave absorption was not observed, so the test was terminated. As shown in Figure 3(a), it can be seen that the test body of Comparative Example 1 remains in a powder state after the test, and when the microstructure is observed, the pores in Comparative Example 1 are not rearranged, and the original ore particles remain as they are, without further investigation. sintering reaction. It is considered that since no magnetite was added in Comparative Example 1 and the magnetite contained only 0.2% by mass in terms of FeO, the sintering reaction did not proceed because microwaves with a frequency of 2.45 GHz could not be heated.

[Experiment 2] Next, a total of 36 g to 38 g of samples was used using industrially used magnetite concentrate and rust scraps as raw materials. In Examples 4 to 6, the blending in which sintering was confirmed in Example 1 was used as a reference, and the blending rate was 3% by mass in terms of FeO. In addition, in Reference Example 1, the same raw material as in Example 5 was used, and the raw material obtained by granulating and drying in advance was filled. Table 3 shows the preparation of Comparative Example 2, Examples 4 to 6, and Reference Example 1. Table 4 shows the ratio of the existing form of Fe element in each raw material. These samples were heated by irradiating microwaves with a frequency of 2.45 GHz at 3 kW.

[table 3] Comparative example 2 Example 4 Example 5 Example 6 Reference example 1 hematite ore 87.5 56.0 83.8 69.4 83.8 quicklime reagent 9.2 10.5 8.7 10.0 8.7 Silica reagent 3.3 3.1 3.1 3.3 3.1 magnetite concentrate 0.0 30.4 0.0 15.1 0.0 Rust 0.0 0.0 4.4 2.2 4.4 ※ FeO in the raw material 0.7 3.3 3.3 3.3 3.3 Raw material status at the time of loading pink pink pink pink into pieces (quality%)

[Table 4] T.Fe FeO metal iron Rust 72.9 63.8 4.8 magnetite concentrate 66.2 9.5 - hematite ore 64.7 0.2 - (quality%)

The measured temperature profile is shown in FIG. 4 . In Comparative Example 2 in which no magnetite concentrate or rust was prepared, the magnetite contained only 0.7% by mass in terms of FeO, and therefore it took about 180 seconds (3 minutes) to reach 1000° C. at which sintering started. On the other hand, in Examples 4 to 6 in which magnetite concentrate or iron rust was blended, magnetite was contained in an amount of 3.0% by mass or more, so the heating rate was fast, reaching 1000°C in 135 seconds (2 minutes and 15 seconds). °C for sintering. In addition, in Reference Example 1, the rate of temperature increase was higher than that of Comparative Example 2, but when compared with Example 5 using the same raw material, the rate of temperature increase was very low as a result.

1: Sintering raw material supply device 2: pallet 3: Microwave irradiation device 4: Pallet width 5: Pallet loading layer height 6: Length of microwave irradiation device 7: Microwave oven 8: Alumina crucible 9: Thermocouple 10: Inner diameter of the upper surface of the crucible (Example: φ30 mm) 11: Crucible height (Example: 27 mm) 12: Thermocouple insertion height (Example: 18 mm)

FIG. 1 is a schematic diagram showing an example of a sintering machine capable of implementing the method for producing sintered ore of the present invention. (a) of FIG. 2 is a schematic diagram which shows the production of sintered ore in one experimental example of this invention. (b) of FIG. 2 is a schematic diagram showing the shape of an alumina crucible and the arrangement of thermocouples. Figure 3 is the photo of the upper surface of the crucible after heating (upper picture) and the observation photo of the sintered structure (lower picture). (a) is Comparative Example 1, (b) is Example 1, (c) is Example 2, and (d) is Example 3. FIG. 4 is a graph showing the relationship between the microwave irradiation time and the temperature change of the sintered raw material in Experiment 2. FIG.

1: Sintering raw material supply device

2: pallet

3: Microwave irradiation device

4: Pallet width

5: Pallet loading layer height

6: Length of microwave irradiation device

Claims (5)

A method for producing sintered ore, which comprises agglomerating sintered raw materials, said sintered raw materials comprising powdered iron ore mainly composed of hematite and a flux, The sintering raw material contains 3.0 mass % or more of magnetite in terms of FeO, and the sintering raw material is heated to 1000° C. or higher by irradiating microwaves. The method for producing sintered ore according to claim 1, wherein the sintered raw material is mixed with one or more of iron ore including magnetite, sintered ore, and dust generated in ironworks. The method for producing sintered ore according to claim 1, wherein the flux is one or more of limestone, quicklime, slaked lime, and slag generated in ironworks. The method for producing sintered ore according to claim 2, wherein the flux is one or more of limestone, quicklime, slaked lime, and slag generated in ironworks. The method for producing sintered ore according to any one of claim 1 to claim 4, wherein the frequency of the microwave is 2.4 GHz-2.5 GHz.