JP2000169916A - High quality sintered ore and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive sintered ore producing technique compatible between a high reducibility and a low reduced powdering property which is impossible to obtain in the conventional sintered ore producing technique. SOLUTION: A grate type agglomerate producing apparatus is used and oxygen-enriched air having 21-50 vol.% average oxygen content is blown into the front-half range 15 of the grate and circulated exhaust gas having 13-20 vol.% average oxygen content, in the circulated exhaust gas generated from the agglomerate producing apparatus, is blown into the rear-half range 16 of the grate. Based on the above producing method, the high quality sintered ore having >70% reduction index RI, <40% reduction degradation index RDI and >=67% strength in the cold-state TI, is produced. This sintered ore contributes to a high pulverized fine coal blowing operation, low silicon molten iron producing operation and low fuel ratio operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION Recently, in the operation of a blast furnace, in order to reduce the production cost of hot metal, a technique of blowing pulverized coal into the blast furnace by reducing the amount of expensive coke used, and refining in the next steelmaking process. In order to reduce the load and reduce the production cost of molten steel, there is a strong demand for technology for improving the quality of sintered ore, which is a raw material for blast furnaces. The present invention relates to a technique for producing high-quality sintered ore, which can improve the quality of sintered ore and can contribute to reduction of the production cost of sintered ore.

[0002]

2. Description of the Related Art Among the quality characteristics of sintered ores, important ones are reducibility, reduced pulverizability and strength in a blast furnace.
Sinter is usually produced in the following process. First, iron ores unloaded from the Vessel are piled up in the fine yard by brand. Thereafter, it piled various powder ore, containing CaO auxiliary material, containing SiO ₂ auxiliary material, mixed by bedding method at a rate that is set in advance dust and carbonaceous material such as, a blending powder. This blending powder, limestone and / or quicklime, quartzite and / or serpentine, coke breeze and / or anthracite, and return ore, and in some cases, raw materials such as plain ore, are put into separate compounding tanks. A predetermined amount of each raw material is continuously cut out from each mixing tank. Then, an appropriate amount of water is added to the cut out raw materials, mixed, and granulated. The sintering raw material thus formed in the form of pseudo particles is continuously transferred from a hopper to a pallet of an endless moving great type sintering machine (Dwyroid type sintering machine) by 500-70.
It is supplied to a layer thickness of about 0 mm. Next, the carbon material in the surface layer is ignited by an ignition furnace, and the carbon material is burned while forcibly sucking air downward, and the combustion heat generated at this time sinters and agglomerates the compounded raw material. I do. After cooling the sintered cake thus baked, it is crushed, sized and 3 to 5 m.
m or more particles are charged into a blast furnace as a product sintered ore. Fine powder ore having a size of 3 to 5 mm or less generated in the crushing and sizing process is used again as a raw material for sinter ore.

[0003] The quality characteristics of the sintered ore produced as described above include cold strength, reducibility and reduced pulverizability.
These greatly affect the stable and efficient operation of the blast furnace.
Therefore, these quality characteristics are particularly strictly controlled. On the other hand, in terms of sinter production costs,
Low energy consumption per unit of electricity and high production rate
High yield is required. More recently, there has been an increasing demand for reducing slag, which is a by-product of blast furnace generation, as much as possible in response to environmental measures and energy conservation. In view of the above background, many techniques relating to sinter quality, production rate, and yield improvement have been proposed. In general, as a method for improving the reducibility and high-temperature properties of a sinter, it is known that it is effective to reduce the amount of slag in the sinter, that is, the SiO ₂ content. However, the cold strength, the yield, and the reduced pulverizability are in conflict with each other, and there are many difficulties to improve both.

[0004] The above-mentioned sintered ore is used as a main raw material in blast furnace operation to produce hot metal. In the production of hot metal using a blast furnace, iron ore (mainly sinter), fuel coke, and limestone as auxiliary materials are charged from the furnace top and hot blast from the lower tuyere of the furnace. Is blown to burn coke, and iron ore is reduced by the generated CO-based reducing gas and thermal energy. Thus, the iron in the iron ore becomes the main component of the hot metal, while the gangue in the iron ore and the ash in the coke become slag together with limestone and the like, and both are regularly discharged from the taphole at the bottom of the furnace. As described above, in the furnace of the blast furnace, hot metal is produced by a high-temperature reaction process between the raw material and the reducing gas. In the operation of such a blast furnace, it is desired to maintain a steady state in which the main operating characteristics are maintained in a good state, that is, to operate the blast furnace stably. Here, in order to bring the main operating characteristics to a good state, it is necessary to control the furnace heat well and to secure the gas permeability and liquid permeability in the furnace. In order to maintain the air permeability and liquid permeability in this furnace in a good state and to maintain a high production rate, it is necessary to maintain the material balance of the furnace interior materials and the furnace heat balance. In addition, it is important that the sinter has particularly high reduction properties and low reduction powderability.

Conventional production techniques for high-reduction sinter and low-reduction pulverizable sinter are as follows. According to the prior art, it is theoretically required to satisfy both characteristics at the same time as follows. Impossible.

(1) Conventional production technology of high-reduced sintered ore Conventionally, high-reduced sintered ore is prepared by mixing raw materials so that the silica content in the product sintered ore is usually 5% or less. The target sinter is obtained by producing the coke ratio under the raw fuel condition of usually 43 kg / t-sinter or less. In this case, in order to reduce the magnetite content in the product in order to obtain a highly reducible sintered ore, the FeO content is reduced to 7%.
Do the following. As described above, as a result of reducing the magnetite content which is hardly reducible, the hematite content increases. However, hematite is 500 to 600 ° C in a blast furnace.
The crystal structure changes when it is reduced to magnetite in the above temperature range, but the crystal strain is broken due to the stress strain generated at the time of this change, so-called reductive decay of the ore occurs, and the air permeability in the blast furnace is deteriorated. As described above, in order to obtain high reducibility of the product sinter in the blast furnace, the magnetite, which is hardly reducible, is reduced to hematite, and the sinter proceeds in the direction in which reduction pulverization proceeds in the blast furnace. In addition, it deteriorates air permeability in the blast furnace and makes blast furnace operation unstable. Therefore, in the case of blast furnace operation using a large amount of such sinter, since the amount of slag in the sinter is small and the air permeability and liquid permeability in the lower part of the blast furnace are good, high pulverized coal injection operation Is suitable for
Since the formation of low melting point slag via eO is suppressed, and as a result, the width and level of the blast furnace cohesive zone are reduced, the method is also suitable for low silicon operation. However, even if an attempt is made to operate at a low fuel ratio in a blast furnace, the reduction and pulverization property is further deteriorated due to the expansion of the low temperature region in the blast furnace at 500 to 600 ° C., and the permeability of the blast furnace is not secured, and stable operation is extremely difficult. Becomes

(2) Conventional production technology for low-reduction powdered sintered ore On the other hand, a conventional production method for a sintered ore that is difficult to be reduced and powdered in a blast furnace is as follows. Conventionally, low-reduced powdered sinters, contrary to the high-reduced sinters described above, are blended with raw materials so that the silica content in the product sinter is usually 5% or more, and the coke ratio is reduced. Is usually produced under raw fuel conditions of 43 kg / t-sinter or more to obtain the desired sintered ore. In this case, by increasing the magnetite content in the product in order to make the ore a low-reducible powder, the stress strain due to the change in the crystal structure from hematite to magnetite is alleviated, and the sinter structure is dense. It is trying to ensure low reduction pulverizability by forming a molten structure. However, as described above, by increasing the silica content in the sintered mineralized product, forming a dense structure, and increasing the magnetite content, reduction and powdering of the sintered ore in the blast furnace is suppressed. Conversely, the sintered ore structure is reduced because it has a dense molten structure. Therefore, in the case of a blast furnace operation using a large amount of such sinter, the permeability of the blast furnace shaft is improved, but the reducibility of the sinter is deteriorated, and the generation in the sinter is reduced. As the amount of slag increases, the gas permeability and liquid permeability in the lower part of the blast furnace deteriorate. As a result, the high pulverized coal injection operation becomes unstable. In addition, the formation of the low melting point slag raises the cohesive zone level, and the low silicon operation becomes unstable. Thus, it is extremely difficult to stably continue the high pulverized coal injection operation and the low silicon hot metal operation, for which the establishment of a stable operation technology is strongly demanded.

[0008]

As described above, it is theoretically impossible with the conventional sinter ore production technology to produce sinter having both high reduction properties and low reduction pulverizability. is there.
Therefore, the present inventors have studied new conditions to be provided for the sintered ore in order to achieve both high reduction properties and low reduction powdering properties. As a result, in order to maintain high reducibility, the sintered ore has micropores dispersed throughout the structure as a sintered ore structure, and the constituent minerals are mainly composed of diffusion type hematite, diffusion type magnetite and calcium ferrite. And the amount of the slag component in the sintered ore must be within a range necessary and sufficient for maintaining the strength of the sintered ore structure. It has been inspired that it is necessary to establish raw fuel and manufacturing process conditions for producing a sintered ore in which a consolidation structure is formed and has a slag component and the intended purpose can be achieved.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to develop and provide a technique for producing a sintered ore having both a high reducing property and a low reducing pulverizing property.

[0010]

Means for Solving the Problems From the above-mentioned viewpoints, the present inventors have intensively studied to develop a technique for producing high quality sintered ore. Generally, in order to obtain a highly reduced (high RI) and low reduction powdered (low RDI) sintered ore, it is important to control the amount and morphology of magnetite in the structure. In a normal sinter production process, a structure is formed by the combustion heat of coke breeze. At this time, when the content of the slag component and coke breeze in the sinter material is higher than the normal level, a dense slag phase is formed in the sinter structure,
The reduction ratio of the magnetite phase, which has good powdering properties but is inferior to the reducing properties, inevitably increases. Therefore,
Achieving high RI becomes impossible.

Accordingly, the present inventors have drastically reviewed the concept of the conventional sinter production process. And, while assuming the raw fuel conditions at the time of high RI sinter production,
By controlling the form of magnetite by reducing the produced hematite to magnetite on a sintering machine while maintaining the porous form of the material, a high R
I conceived a method for producing a sintered ore with low RDI. That is, sintering is performed under the raw fuel conditions during the production of the high RI sintered ore, and sintering is performed in a high oxygen potential atmosphere by supplying oxygen-enriched air in the first half of the great area. In, sintering is performed in an atmosphere having a low oxygen potential. By such a method, the hematite generated in the first half region of the great is reduced to magnetite in the second half region of the great to obtain the magnetite which retains the porosity, so that the mineral structure is accompanied by reduced powderization while maintaining high RI. It is possible to transform into no magnetite.

The present invention has been made on the basis of the above-mentioned findings. According to the first aspect of the present invention, there is provided a method for producing a high-quality sintered ore using a great-type agglomerate ore producing facility, wherein an average oxygen content is contained in a first half region of the great ore. Oxygen-enriched air having a rate in the range of 21 to 50% by volume is blown, and the circulated exhaust gas having an average oxygen content in the range of 13 to 20% by volume of the circulated exhaust gas generated from the agglomerate ore production equipment in the latter half of the great area It has a feature in injecting.

[0013] The high quality sinter of claim 2 is
An oxygen-enriched air having an average oxygen content in the range of 21 to 50 vol% is blown into the first half of the great area using the great type agglomerate production equipment, and the circulating exhaust gas generated from the agglomerate ore production equipment is injected into the second half area of the great. Of which the average oxygen content is 1
A sintered ore produced by injecting circulating exhaust gas in the range of 3 to 20 vol%, wherein the reduction ratio RI exceeds 70%, the reduction powdering ratio RDI is less than 40%, and the cold strength TI
Is 67% or more. However, the reduction ratio RI and the cold strength TI are measurement methods of the tumbler strength TI _{+10 mm} specified in JIS, and the reduction powdering ratio RDI is the measurement method recommended by the Iron and Steel Institute of Japan Iron and Steel Working Group. Point.

[0014]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an endless moving bed type sintering machine for explaining one embodiment of the present invention. FIG.
In the figure, reference numeral 10 denotes an endless moving bed type sintering machine main body (hereinafter referred to as “sintering machine main body”), which comprises an endless moving bed type grate (called “great”) 11 and a wind box 12. The powdery sintering raw material 7 charged into the great 11 from the sintering raw material supply tank 1 is ignited in the ignition furnace 2 and then supplied from the upper oxygen-enriched air supply hood 8 and the circulating exhaust gas blowing hood 9. The coke breeze in the sintering raw material is burned by the oxygen in each gas of the gas and the air leaked from the hood, and sintering proceeds. On the other hand, exhaust gas generated from the sintering material layer is sucked and exhausted downward by the lower wind box 12. Then, the cake-like sintered ore 7 ′, which has been calcined, is crushed and sieved to produce a product sintered ore. As shown in FIG. 1, the great 11 is divided into a raw material charging region 13, an ignition region 14, a first half region 15 and a second half region 16 in order from the raw material charging side to the mining side.

In the sinter production process, the mixing ratio of the raw material fuel of the sinter, ie, the main raw material such as ore, the carbon material such as coke breeze, and the auxiliary raw material such as the SiO ₂ -containing material and the CaO-containing material, Adjust to high RI sintered ore production conditions. The raw fuel conditions for the high RI sinter were such that the SiO ₂ content in the product was 5.0% or less, and the coke breeze ratio was 43%.
It is desirably set to kg / t or less. Great first half area 1
The oxygen content in the oxygen-enriched air supplied to 5 was 21 vol.
%, But not more than 50 vol%, and if it is not necessary to raise the production rate specially, usually set it to 30 vol% or less,
It is desirable to operate stably. The oxygen enrichment rate is increased within the above range according to the required production rate. As described above, air having a high oxygen potential is supplied in the first half region, whereas gas supplied to the great second region 16 must be limited to a gas having a low oxygen potential. Therefore, it is desirable to utilize the circulating exhaust gas of the sintering machine sucked from the wind box 12. Second half area 16
The oxygen content in the circulating exhaust gas supplied to the furnace is within the range of 13 vol% to 20 vol%, and in the operation of a sintering machine at a normal production rate, the oxygen content is limited to 18 vol% or less for stable operation. desirable. In this case, it is only necessary to adjust the average oxygen concentration in the gas supplied to the latter half region to satisfy the above concentration, and there is no particular limitation on which great region the circulating exhaust gas is supplied to the latter half region.

The definition of the first half region and the second half region of the present invention requires that the sintering reaction be carried out in the sintering raw material layer,
From this point of view, the ignition region 14
From 0 to 10% of the front of the effective firing great area excluding
A range of up to 60% is suitable. The second half area is a remaining great area obtained by subtracting the first half area.

The reason why the oxygen content in the gas supplied to the sintering material layer is set to the above-mentioned condition is that, in the first half of the great region, the amount of magnetite is reduced by setting the production conditions of the high RI sinter to reduce the amount of hematite. The reaction to increase
This is because the hematite is reduced to magnetite in the great second half region. Even by this reduction, the micropores of hematite are inherited and retained by magnetite without disappearing. Since this magnetite has micropores, it has good reducibility,
Since transformation from hematite to magnetite does not occur at -600 ° C, reduced powdering does not occur. By causing the magnetite to have the effect of preventing the reduction powdering from occurring, the reduction powdering of the sintered ore due to the low slag content due to the restriction of the SiO ₂ content in the sintering raw material to 5% or less is compensated. ing.

An important feature of the present invention is that porous hematite produced by treating the first half of the sintering process under the raw fuel conditions for producing highly reducible sintered ore is used in the latter half of the sintering process. The point is that only the proportion is reduced under the combustion of the low oxygen potential gas to produce porous magnetite. The sintered ore produced by satisfying the conditions of the present invention has a structure in which micropores are dispersed and distributed throughout the structure as a sintered ore structure, and the constituent mineral is mainly composed of diffusion type hematite, diffusion type magnetite and calcium ferrite. And the amount and morphology of magnetite in the sinter structure is controlled. That is, the constituent mineral components of the sintered ore are mainly of diffusion type hematite, diffusion type magnetite and calcium ferrite, and the composition thereof is diffusion type hematite: 40-6.
0%, the diffusion magnetite: 10-30% and calcium ferrite _{(CaO · 2Fe 2 O 3)} : 20~40
%, And slag: desirably in the range of 3 to 10%. Here, the operation and effect of the diffusion type hematite and the diffusion type magnetite in the sintered ore in the blast furnace are as described above. Since calcium ferrite does not proceed in a low temperature region of 600 ° C. or lower, reduction is not performed. Exhibits the effect of suppressing powdering.

The sintered ore thus produced is excellent in both high reduction properties and low reduction pulverizability, and is also excellent in cold strength. That is, the reduction ratio RI exceeds 70%, the reduction powdering ratio RDI is less than 40%, and the cold strength TI _{+10 mm} is 67%.
% Or better. When the reduction ratio RI exceeds 70%, the reduction load is reduced because the blast furnace does not reach the lower part of the blast furnace in an unreduced state, and when the reduction powdering ratio RDI is less than 40%, particularly in the low temperature region at the top of the blast furnace. Since there is little reduction powdering and good air permeability in the blast furnace shaft, stable blast furnace operation is performed. Also,
The use of the sintered ore having the above quality contributes to stabilization of the blast furnace operation. Cold strength TI
_{If +10 mm} exceeds 67%, the yield is good without collapse during the sinter transfer process, and the blast furnace operation is stable because it does not collapse when dropped from the top of the blast furnace. By using such a high-quality sintered ore as a raw material for the blast furnace, a high pulverized coal injection operation, a low silicon hot metal operation, and a low fuel ratio operation can be stably performed.

[0020]

Next, the present invention will be described in more detail by way of examples. Using the sinter production facility shown in FIG. 1, high-quality sinter was produced by a production method within the scope of the present invention. As comparative examples, high RI sintered ore and low RD
Sinters were manufactured according to the manufacturing conditions of I sinter.
Production rate of 1.65 to sintering machine with great area 450m ²
A test operation of 1.98 t / m ² · h was performed. Table 1 shows an overview of the test conditions, and Table 2 shows the results.

[0021]

[Table 1]

[0022]

[Table 2]

The test operation conditions of the embodiment are such that the raw fuel blending ratio and other raw fuel conditions are in accordance with the production conditions of the conventional low silica / low coke ratio sintered ore, and the inlet side of the great after the ignition region. Oxygen content 2 in the first half of 0-25%
Oxygen-enriched air in the range of 5-30% was supplied, while circulating exhaust gas in the range of 17-20% average oxygen content was supplied to the second half of 75-100% of the remaining great. On the other hand, in Comparative Examples 1 and 2 according to the prior art,
According to a conventional method, air having an oxygen content of 21.0% in the supply gas to the latter half region of the great gas was supplied.

The properties of the obtained sintered mineral product are as follows. Example: In the example, the SiO ₂ content of the sintered ore was low, the basicity was also a predetermined value, and a slag component having a target was obtained. The microstructure opening in the mineral structure and the particle surface of the sinter was analyzed by image processing. As a result, in the example, the magnetite phase is greatly increased from 4.3% of the high RI sintered ore of Comparative Example 1 to 17.9%. However, the distribution amount of the micropores was kept at the same level as in Comparative Example 1. On the other hand, with the increase in the magnetite phase, the hematite phase of the example was greatly reduced to 58.9%, and was further smaller than 63.1% of the low RDI sintered ore of Comparative Example 2. And the calcium ferrite phase is maintained at a high level. Further, in the example, the amount of slag is maintained at the same low level as that of the high RI sintered ore of Comparative Example 1.

From the above, when the conditions for achieving a high RI are examined on the basis of the characteristics of the high RI sintered ore of Comparative Example 1, the SiO ₂ content is low and the slag amount is low in the examples. And that it has been made porous has become an advantageous condition. However, the increased magnetite phase is disadvantageous. Therefore, the level of reducibility of the sinter of the example is determined by the overall effect of the degree of improvement due to the change to the porosity and the degree of deterioration due to the increase in the magnetite phase. According to the measurement results of the JIS-RI value, it can be seen that high RI sintered ore of the same level as in Comparative Example 1 was obtained in the examples.

Similarly, when the conditions for achieving a low RDI in the examples are examined based on the characteristics of the low RDI sintered ore of Comparative Example 2, the reduced slag amount is a disadvantageous condition. I have. However, the increased magnetite phase is an advantageous condition. Therefore, the level of reducible pulverizability of the sintered ore of the example is determined by the overall effect of the degree of deterioration due to the decrease in the amount of slag and the degree of improvement due to the increase in the magnetite phase. According to the measurement result of the predetermined RDI value, it is understood that low RDI sintered ore having the same level as that of Comparative Example 2 was obtained in the example.

Further, since the sintered ore of the embodiment has the above-mentioned component composition and properties such as a mineral structure, the cold strength TI
_{+ 10mm} maintains the level of conventional high quality sinter. As described above, the greatest feature of the sintered ore of the present invention produced by the method of the present invention is that the amount and form of magnetite in the mineral structure are appropriately controlled, and as a result,
The intended goal of the present invention has been achieved.

Comparative Example: On the other hand, in the case of the sintered ore produced by the method of the prior art which is out of the scope of the present invention, in Comparative Example 1, the conventional high quality sintered ore with emphasis on the reducibility was obtained. Further, in Comparative Example 2, a conventional high-quality sintered ore with emphasis on reduction pulverizability was obtained, but a sintered ore satisfying both reduction and reduction pulverizability was obtained. I couldn't.

Next, an operation test of hot metal production was conducted using the high-quality sintered ore produced in the above-described embodiment as a raw material for iron making in a real blast furnace. As a result, the following items were confirmed. That is, it was found that the high pulverized coal injection operation, the low silicon hot metal production operation, and the low fuel ratio operation were performed stably over a long period of time.

[0030]

As described above, according to the present invention,
High RI and low RDI that could not be achieved conventionally
It is possible to produce sinter at low cost, and as a result, blast furnace charging which enables stable operation of high pulverized coal injection operation, low silicon hot metal production operation and low fuel ratio operation in blast furnace operation It is possible to provide a high-quality sintered ore as a raw material for use and a method for producing the same, which brings about an industrially useful effect.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an endless moving bed type sintering machine for explaining an embodiment for producing a high quality sintered ore of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sintering raw material supply tank 2 Ignition furnace 3 Oxygen-enriched air line 4 Exhaust gas circulation line 5 Blower 6 Dust collector 7 Sintering raw material 7 'Cake-shaped sintered ore 8 Oxygen-enriched air supply hood 9 Circulating exhaust gas blowing hood 10 Sintering Machine body 11 Great 12 Wind box 13 Raw material charging area 14 Ignition area 15 First half area 16 Second half area 17 Chimney 18 Main exhaust fan

Claims (2)

[Claims] An oxygen-enriched air having an average oxygen content in the range of 21 to 50 vol% is blown into the first half of the great area using a great-type agglomerate manufacturing facility, A high-quality sintered ore having high reducibility, low reduction pulverizability, and high strength, characterized by injecting recirculated exhaust gas having an average oxygen content in the range of 13 to 20 vol% of the generated recirculated exhaust gas. Manufacturing method. 2. A great-type agglomerate production facility, wherein oxygen-enriched air having an average oxygen content in the range of 21 to 50 vol% is blown into the first half of the great area, and the agglomerate production facility is blown into the second half of the great area. A sintered ore produced by blowing a circulating exhaust gas having an average oxygen content in the range of 13 to 20 vol% of the generated circulating exhaust gas, wherein the reduction ratio RI exceeds 70% and the reduction powdering ratio RDI is High quality sintered ore characterized by having a cold strength TI of less than 40% and 67% or more.