KR100308830B1 - Sintered ore manufacturing method for improving recovery ratio of sintered ore - Google Patents

Abstract

PURPOSE: A sintered ore manufacturing method for improving recovery ratio of sintered ore is provided in which strength and recovery ratio of sintered ore are increased on the upper part of sintering car using low quality iron oxides as sintering raw material, and sintering dust collector is hardly adversely affected even when much of oil content is adhered to the low quality iron oxides. CONSTITUTION: The sintered ore manufacturing method for improving recovery ratio of sintered ore comprises the processes of separately mixing silica ordinarily added as a sintering raw material with the low quality iron oxides in case of using low quality iron oxides such as Fe, FeO and Fe3O4 ores or low quality iron oxides such as mill scale, steelmaking sludge and metal iron generated from industrial processes such as iron manufacturing and metal working in the state that the respective ores are mixed as an iron ore sintering raw material; and charging the mixture of the low quality iron oxides and silica onto the upper part of sintering raw material layer, and sintering the mixture so that strength and recovery ratio of sintered ore are improved on the upper part of sintering layer.

Description

Sintered ore manufacturing method for improving the recovery rate of sintered ore

The present invention not only improves the recovery rate of sintered ore when manufacturing sintered ore using low iron oxides such as mill scale and metal waste generated in various metal processing processes such as steelmaking and cutting such as rolling and wire rod as iron ore sintering raw materials. The present invention relates to a method for producing a sintered ore in which oil contained in these lower iron oxides or the like hardly adversely affects the sintering dust collector.

Generally, in the dwight-lyy type sintering process in which sintered fine ore is sintered to produce a sintered ore of a size suitable for blast furnace use, limestone, serpentine, silica and fuel, which are generally raw materials, are not included in fine iron ore. Phosphorus coke or anthracite and the like are mixed at a constant ratio.

The raw material pre-processed through the mixing and assembly process is supplied to the sintered trolley as shown in FIG. 1, which is connected to the endless track as shown in FIG.

After the raw material is charged into the sinter bogie, the upper part of the charged raw material is ignited by the ignition device in the ignition furnace, and if continuously sucked from the lower part, the coke or anthracite coal in the blended raw material is burned and the flame proceeds continuously to the lower part. As a result, iron ore and limestone react with each other to form a melt, and the melt binds the fine iron ores to each other.

After the combustion zone reaches the lower part and sintering is completed, the sintered cake is discharged from the trolley and crushed into a particle size suitable for the blast furnace and supplied to the blast furnace.

In the general sintering operation by the lower suction, the raw materials in the lower part of the sinter bogie are transferred to the lower part in addition to the heat generated in the combustion of fuel contained in the lower layer of the sinter bogie, and the lower layer is lower than the upper part. Due to the high temperature, a large amount of melt is produced, resulting in high strength and recovery of the sintered ore.

On the other hand, since the upper layer is ignited by the fuel contained in the sintered raw material by the ignition furnace, the air at room temperature is sucked through the upper upper layer immediately, so it is rapidly cooled by the air, and the upper layer of the sintered truck has sufficient melt to bond the sintered raw materials together. There was a problem that the strength and recovery of the sintered ore is low because it is not produced.

In this way, in order to suppress the decrease in the strength and recovery rate of the sintered ore at the upper part of the sintering cart in the normal sintering operation, the upper part of the sintered raw material layer is compacted using rollers to suppress the flow rate of air flowing through the upper part of the sintered layer. By suppressing the rapid cooling of the upper layer due to the large inflow of air, or by preparing a calcium ferrite raw material having a relatively low melting point, it is proposed to spray this material on the upper layer.

However, in the roller method, since the load of the roller is transferred to the lower layer in addition to the upper layer, the overall flow of air in the sintered layer is largely suppressed, resulting in a decrease in productivity due to a decrease in air permeability. There was a problem in that the manufacturing cost is high because the limestone is made through a separate process such as crushing after heat melting in a separate high temperature furnace.

In addition, mill scale, metal, iron, etc. generated in various processes may have a large amount of oil, such as rolling oil, lubricating oil, and cutting oil, mainly composed of hydrocarbons, depending on the generation process. In the case of sintering by simply mixing the sintered raw materials as shown in FIG. 3, as the sintering proceeds as shown in FIG. 3, part of the oil attached to the lower iron oxide in the upper combustion zone in the raw material layer burns during the sintering process, but the oil in the lower combustion zone. Part of is heated and evaporated as the combustion zone goes to the lower part and gradually moves to the lower part of the sintering bogie. When the sintering progresses and reaches the lower part of the sinter bogie, some of the oil eventually evaporates like moisture and flows into the electrostatic precipitator. do.

Moisture is easily discharged to the outside of the dust collector without affecting the electrostatic precipitator because the temperature of the electrostatic precipitator is generally 100 ℃ or more, but the oil is attached to the high resistivity material directly integrated on the electrode plate of the dust collector or attached to the dust collector.

This oil is also known to greatly reduce the dust collection efficiency when attached to the dust collector plate because it is a high electrical resistivity material.

In addition, since the flash point of these oils is generally about 150-300 ° C, when the oil is accumulated in a large amount on the electrode plate of the electrostatic precipitator, the precipitator is flashed by the hot exhaust gas generated during the sintering process or the spark generated by the electrode of the electrostatic precipitator. There was a problem that it is easy to be burned out and the dust collector is lost.

Accordingly, the present invention uses the lower iron oxide as a sintering raw material to increase the strength and recovery of the sintered ore at the top of the sintered bogie, and to improve the recovery rate of the sintered ore to have little effect on the sintered dust collector even when oil is attached to the lower iron oxide. The purpose is to provide a sintered ore manufacturing method.

In order to achieve the above object, the present invention provides a mill scale and steel sludge produced in an industrial process such as iron and metal processing in the state of mixing each lower iron oxide such as Fe, FeO, Fe ₃ O ₄ or these minerals. When using lower iron oxides, such as metal iron, as iron ore sintering raw materials, silica is added separately to these lower iron oxides, which are usually added as sintering raw materials, and then charged into the upper part of the sintering raw material layer and sintered to sinter ore at the top of the sintering layer. It is characterized in that to improve the strength and recovery of character.

1 is a perspective view of a sintered trolley for loading raw materials

2 is a block diagram of a sintering apparatus according to a conventional sintering method

Figure 3 is a state diagram showing the state of sintered ore production according to the sintering progress in the sintering cart

4A is a low melting point composition region distribution diagram below 1300 ° C. in a CaO—SiO ₂ —Fe ₂ O ₃ system

4B is a low melting point composition region distribution diagram at 1300 ° C. or less in a CaO—SiO ₂ —FeO system.

5 is an X-ray diffraction distribution model of mill scale used for iron ore sintering raw materials

6 is a state diagram showing the distribution of the mill scale when the mill scale is simply mixed with other iron ore raw materials and charged into the sintering cart.

7 is a state diagram showing the distribution of mill scale and silica when charging the mixed raw material of mill scale and silica on top of the sintered raw material;

8 is a block diagram of a sintering machine equipped with a separate hopper and a charging device for supplying a mixed raw material of mill scale and silica to the upper portion of the sintered raw material

<Explanation of symbols for main parts of the drawings>

1: Sintered trolley sidewall 2: Grate bar

3: Sintered trolley 4: Caterpillar wheel

5: Wind Box 6: Upper Light Hopper

7: compounding material charging hopper 8: ignition furnace

9: main exhaust pipe 10: electric dust collector

11: Main Blower 12: Stack

13: General Formulation Material 14: Mill Scale

15: Mill scale charging hopper 16: Quartz

In iron ore sintering, it is known that there are generally two system of melt formation paths at the beginning of the sintering reaction. FIG. 4A shows the distribution of the low melting point composition region of the melt at 1300 ° C. or lower in the CaO—SiO ₂ —Fe ₂ O ₃ system. As shown in the figure, the limit tube is a calcium ferrite region and the other is a silicate region. However, the actual sintering reaction is carried out in a small reducing atmosphere in the early stage of combustion due to the generation of reducing gas due to the coke combustion reaction, and the low melting point composition region of the silicate system as shown in FIG. It can be seen that the formation of the ferritic melt was rather suppressed.

As a result, hematite (Fe ₃ O ₄ ), ustite (FeO), and metal Fe, which have low iron oxidation, are used instead of hematite-based iron ore raw materials containing Fe ₂ O ₃ as the main mineral. When the lower iron oxide is used as a sintered raw material, it is easy to generate a reducing atmosphere than when the lower iron oxide is not used, and thus, a silicate-based melt having a low melting point can be easily produced.

Such low iron oxide raw materials include mill scales generated in steelmaking processes such as crushing, hot rolling, thick plates, castings, wire rods, etc., dust generated in steelmaking processes, or metal irons generated in metal processing processes such as cutting. In addition, these waste resources are partially used to replace iron ore as a sintering raw material in terms of recycling.

Mill scale is generally an iron oxide formed on the surface of steel products during the heating process of steel products at a high temperature, and contains a large amount of minerals such as low iron oxides such as ustite (FeO) and magnetite (Fe ₃ O ₄ ). Dust generated from is composed mainly of metal iron (Fe) as fine particles, and materials generated from metal processing processes such as cutting are made of metal iron, and when sintered by mixing them with iron ore as a sintering raw material Lower iron oxides, such as mill scales and metals, can oxidize during the sintering process, causing exothermic reactions, which can replace significant amounts of coke added as sintered fuel.

Therefore, the present invention intends to provide a method of securing strength of sintered ore and recovering sintered ore at the top of the sintered bogie by using a silicate-based low melting point solution well formed in the reducing sintering atmosphere as described above.

When iron ore is sintered, low-grade iron oxides such as steelmaking dust or mill scale and silica sand containing SiO ₂ as a main component are mixed with each other in order to form a reducing component and silicate-based melt composition. It is a method to greatly increase the strength of sintered ore and recovery rate of sintered ore at the top of the sintered bogie by promoting the binding of ferrite ore by forming strong reducing atmosphere in the upper layer and thus promoting the formation of lower iron oxide and silica.

(Example)

In this embodiment, the effect of the present invention was confirmed by using a small apparatus for testing before use in a large sintering machine that produces a large amount of sintered ore.

In order to understand the effects of sintered ore recovery and changes in oil content in the sintered flue gas when the low iron oxide is simply mixed and the low iron oxide is separately mixed with silica, the iron ore, serpentine, limestone, ore, Table 1 shows the compounding ratios when 4% of the scale is added in the blending of raw materials in the manufacture of general sintered ore such as silica coke.

As the lower iron oxide used in the test, a mill scale containing about 0.3% of oil was used. As a result of X-ray diffraction analysis, it was found to have a rotation distribution model as shown in FIG. 5, and the mill scale mainly consisted of wustite, magnetite and a small amount of hematite. It can be seen that consists of.

Sintered test ingredient mix ratio (unit: wt%) Type of raw materials Compounding ratio (%) ironstone 55.75 scale 4 Limestone 11.85 quicklime 1.01 Serpentine 1.54 burr 0.85 Sintered Glow 21.35 Bunk coke 3.65 sum 100.00

The oil scale containing mill scale is used by simple mixing with other sintered raw materials (see Fig. 6) and after mixing the mill scale and silica in a separate mixer according to the present invention, it is only at the top of the pot (Fig. 7). Sintering was performed by sintering and the sintering test was performed under the conditions shown in Table 2 below.

Sintering test condition of sintering simulation tester Port diameter 240 (mm) After Sintered Layer 500 (mm) Ignition temperature 1,100 ℃ Ignition time 2 minutes Negative pressure at ignition 1,000mmAq Negative pressure after ignition 1500 mmAq

As a result of the test, there was little difference in the quality of sintered ore when sintered by simple mixing of oil scale milled scale and when the mixed raw material of mill scale and silica was loaded on top of the sintered raw material layer. When the sample mixed with the scale and the silica was charged on the upper part of the sintered raw material layer, the sample was improved by about 5% compared to the case of simply mixing and blending the mill scale.

On the other hand, the amount of oil discharged by evaporating from the lower part of the sintered bed when sintering by simply mixing the mill scale with oil and sintering by charging the raw material of the mill scale and silica with the upper part of the sintered raw material layer For comparison, the gas discharged from the bottom was continuously sucked at a constant pressure during the sintering time using a filter attached device, and then the filter was separated to analyze the oil.

As a result of analysis, oil was detected about 50ppm when sintered by simply mixing the mill scale with oil, but oil was not detected when the raw material mixed with mill scale, silica, and coke was charged to the top of the raw material layer.

As described above, in a batch type small sintering apparatus for sintering test, a raw material in which mill scale and silica are mixed at the top of the pot can be easily loaded. However, in the commercial Dwight Lloyd type sintering apparatus in which the sintering bogie continuously rotates the caterpillar phase, it is difficult to continuously supply the raw material of mill scale and silica to the top of the bogie, as shown in FIG. A hopper and a charging device for separately supplying a mixed raw material of mill scale and silica were installed separately, and then sintering was carried out after charging a raw material mixed with scale and silica containing a lot of oil in the upper layer of the sinter truck.

As a result, when the sintered mill scale with oil was sintered by simple mixing, the average dust concentration of dust in the sintering machine electrostatic precipitator was about 55 mg / Nm ³ . Was about 30mg / Nm ³ , and the collection efficiency was improved, and the recovery rate of sintered ore was also improved by about 3% compared with the case of using simple blended mill scale with oil.

In the present invention as described above, by charging the raw material mixed with mill scale and silica on the upper part of the raw material loading layer, the melt is easily formed by generating a reducing atmosphere by supplying lower iron oxide and promoting reaction between silica and lower iron oxide. In addition to the effect of increasing the recovery rate of sintered ore in the upper part of the sintered layer, as well as lower iron oxides with a lot of oil content, the negative pressure sucked below the normal pressure when mixed with the silicate mineral on the upper part of the sintered bogie as in the present invention is 1500 mmAq. As compared to the above, it is about 1000mmAq when ignited, and because the pressure is low, not only the rate of oil flows to the lower part is lower but also the oil contained in the lower iron oxide is burned directly by the burner's flame. Low iron oxides with a large amount of oil attached to them are also bad for electric dust collectors. There is an effect that can be sintered operation without compromising the flavor.

In addition, when the lower iron oxide is used as a sintering raw material, the lower iron oxide is reduced to NO generated in the combustion process such as coke to N to suppress the generation of NO or the lower iron oxide is burned due to oxidation during the combustion of coke or the like. By lowering the oxygen partial pressure in the bed, it is possible to suppress the reaction between nitrogen in the fuel and oxygen in the air, thereby suppressing the generation of NO in the sintered flue gas.

Claims (1)

Low iron oxides such as Fe, FeO, Fe ₃ O ₄ or lower iron oxides such as mill scale, steel sludge, and metal iron that occur in industrial processes such as iron and metal processing, with their respective minerals mixed. When used as a sintering raw material, these low iron oxides are separately mixed with silica, which is usually added as a sintering raw material, and then charged into the upper part of the sintered raw material layer and sintered to improve the strength and the yield of the sintered ore at the upper part of the sintered layer. Sintered ore manufacturing method for improving the recovery rate of sintered ore characterized in that.

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