JP2007138274A - Sintered ore for starting up operation after repairing blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sintered ore for starting up the operation after repairing a blast furnace with which in the case of starting up the operation after repairing a blast furnace, the gas permeability in the furnace is kept to good condition by restraining the enlargement of a fusing zone and the liquid permeability in a furnace bottom part is kept to good condition and the furnace condition of the blast furnace is stabilized and the starting-up of the operation at high speed can be achieved. <P>SOLUTION: In the case of starting up the operation in the repaired blast furnace, since the sintered ore alternately charged with coke into the blast furnace has 0.8-1.2 mass% alumina and 1.3-1.65 basicity, the deterioration of the gas permeability in the blast furnace and the liquid permeability in the furnace bottom part at the starting-up time of the blast furnace, is prevented and the blast furnace can stably be started up at high speed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a startup sintered ore after renovation of a blast furnace suitable for starting up at a high speed (short days) while stably maintaining the state of the blast furnace.

Conventionally, in starting up a blast furnace after refurbishing the blast furnace, first, coke is laid on the bottom of the furnace, and then sleepers and coke are sequentially filled, and then the sinter and coke are alternately charged in layers. In this state, hot air was supplied into the blast furnace furnace and the operation was started.
As this sintered ore, for example, as described in Patent Document 1, the component structure used in normal operation, that is, the basicity (CaO / SiO ₂ ) is 1.25 to 2.5, alumina (Al ₂ O ₃ ) having about 1.6 to 2.8 was used.

JP-A-9-13107

However, at the time of starting up the above-mentioned fire, since a large amount of coke is charged in the blast furnace furnace (approximately 10 times the normal operation), a large amount of ash remains in the furnace when the coke burns. . Due to the alumina and silica contained in this ash, the cohesive zone formed in the blast furnace furnace becomes larger than in normal operation, the pressure loss in the furnace increases, the air permeability deteriorates, and it accumulates at the bottom of the furnace. The liquid permeability of the hot metal deteriorated and it was difficult to start up the blast furnace stably and at high speed.

The present invention has been made in view of such circumstances, and at the time of start-up after blast furnace renovation, the enlargement of the cohesive zone is suppressed to maintain good air permeability in the furnace, and the liquid permeability at the bottom of the furnace is improved. An object of the present invention is to provide a sinter for start-up after renovation of a blast furnace, which can maintain a good condition and stably start the blast furnace at a high speed.

The present invention is for solving the above-mentioned problems, and means (1) is that when a modified blast furnace is started up, the sintered ore alternately charged with coke in the blast furnace is 0.1% alumina. It is 8 mass% or more and 1.2 mass% or less, and basicity is 1.3 or more and 1.65 or less.

The start-up sintered ore after the blast furnace refurbishment of the present invention is formed in the blast furnace because alumina and basicity are defined within a predetermined range when the blast furnace after the blast furnace renovation is started. While suppressing the enlargement of the cohesive zone, the pressure loss due to this cohesive zone can be suppressed more than before, preventing the deterioration of the air permeability in the furnace and the liquid permeability at the bottom of the furnace when the blast furnace is started up. Can be started stably and at high speed.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
The sinter for start-up after the blast furnace repair according to an embodiment of the present invention (hereinafter also simply referred to as sinter) is alternately charged with coke in the blast furnace when the repaired blast furnace is started up. Alumina is 0.8 mass% or more and 1.2 mass% or less, and basicity is 1.3 or more and 1.65 or less. This will be described in detail below.

When starting up the blast furnace, hot air is supplied to the furnace to burn sleepers and coke filled in the furnace, and in the process of raising the temperature inside the furnace, a cohesive zone is formed at the top of the furnace, In this operation, a core is formed in the lower part and the operation is shifted to normal blast furnace operation.
At the time of start-up, when using a very large blast furnace with a furnace internal volume exceeding 5000 m ³ , the hearth diameter reaches about 15 m. For this reason, as described above, even if hot air is supplied into the furnace and the sleepers and coke are burned, the temperature is not sufficiently high up to the center in the furnace radial direction of the furnace core formed on the hearth. Then, the melt (mixture of molten iron and slag) begins to drip from the formed cohesive zone.
For this reason, when the temperature of the melt to be dripped is low, it solidifies in the furnace core.

When the blast furnace is started up over a long period of time (about 3 to 4 days) as in the past, the amount of hot air gradually increases, so the solidified melt is re-dissolved. It wasn't.
However, when the amount of hot air supplied into the furnace is rapidly increased to start up at a high speed (about 1 day), the present inventor may cause a hindrance to air flow and deteriorate the furnace condition. It became clear from these simulations.
Therefore, as a result of further investigation by the present inventors, even if there is a relationship between the timing at which the melt starts dropping and the temperature at the center of the furnace core, if the temperature of the melt is 1400 ° C. or higher, the furnace It has been found that the melt does not solidify at the core and cause a liquid permeability failure at the bottom of the furnace.

Based on this, it was studied to increase the temperature at which the dropping of the sintered ore, which is the cause of the melt, was dropped. As a result, when the dropping start temperature of the sintered ore is increased, as shown in FIG. 1, when the temperature exceeds 1420 ° C., the dropping rate of the melt rapidly decreases from 80%. It turns out that there is a need to do. In addition, a dripping rate means the ratio of the dripped melt with respect to the sintered ore to heat.
That is, when the dripping rate is drastically lowered, the sintered ore is softened and melted in the cohesive zone so that it does not drip. Therefore, the cohesive zone formed in the blast furnace is enlarged and droops, Lower air permeability. Here, if the hot air supplied from the tuyere into the furnace is rapidly increased, the furnace condition becomes unstable, so the dropping start temperature is set to 1420 ° C. or lower.
From the above, the sintered ore used when starting up the blast furnace needs to have a composition in which the dripping start temperature is in the range of 1400 to 1420 ° C.

Next, the composition of the sintered ore related to this dripping start temperature will be examined.
There are alumina (Al ₂ O ₃ ) and basicity (CaO / SiO ₂ ) in the sintered ore as the starting temperature of the sintered ore, ie, the melting point, and this relationship was investigated. 2 shows the relationship between the sinter ore start temperature and the amount of alumina, and FIG. 3 shows the relationship between the sinter start temperature and basicity.
As apparent from FIG. 2, in order to set the dropping start temperature in the range of 1400 to 1420 ° C., the amount of alumina in the sintered ore needs to be 0.8 to 1.2 mass%. This is because when the amount of alumina in the sintered ore is less than 0.8% by mass, the dropping start temperature of the sintered ore exceeds 1420 ° C., whereas when it exceeds 1.2% by mass, the dropping start temperature is less than 1400 ° C. By becoming. Therefore, the lower limit of the amount of alumina in the sintered ore is preferably 0.9% by mass, and the upper limit is preferably 1.1% by mass.

Moreover, as shown in FIG. 3, in order to make the dripping start temperature of a sintered ore into the range of 1400-1420 degreeC under the alumina amount in a sintered ore 0.8-1.2 mass%, The basicity needs to be 1.3 to 1.65. When the basicity is less than 1.3 when the amount of alumina in the sintered ore is 1.2% by mass, the dropping start temperature of the sintered ore is less than 1400 ° C., while the amount of alumina is 0.8 When the basicity exceeds 1.65 in the case of mass%, the dropping start temperature exceeds 1420 ° C. Therefore, it is preferable to set the lower limit of basicity to 1.4, while the upper limit is preferably set to 1.6.

In producing the sintered ore shown above, as iron ore as a raw material of the sintered ore, in the ore, for example, a low Al ₂ O ₃ ore having an alumina amount of 1.0 mass% or less (for example, Carajas) and the proportion of low Al ₂ O ₃ ore in the sintered ore is increased. The amount of iron ore in the sintered raw material is increased from the amount of iron ore used during normal operation of the blast furnace, and the amount of CaO added to the sintered raw material is decreased to adjust the basicity of the sintered ore. To do.
Thus, the amount of Al ₂ O ₃ and basicity can be produced sintered ore adjusted to the range described above.

Next, in order to use the startup sinter after the blast furnace repair according to the example for the actual blast furnace startup, the dropping start temperature of the sinter was confirmed using the test apparatus 10 shown in FIG. The results will be described.
The test apparatus 10 includes a reaction tube 12 having a sample stage 11 in which holes (not shown) having a diameter of about 10 mm are formed at equal intervals, and an electric furnace 13 in which the reaction tube 12 is arranged vertically. And have. The reaction tube 12 is placed on a receiving tray 14 disposed below the electric furnace 13, and the sample disposed on the sample stage 11 is transferred to a cylinder rod 16 by an air cylinder 15 disposed above the electric furnace 13. It is possible to press through. An introduction pipe 17 for introducing a reducing gas into the reaction tube 12 is provided at the lower part of the electric furnace 13, and a discharge pipe 18 for discharging the reducing gas is provided at the upper part. The introduction pipe 17 and the discharge pipe 18 are respectively provided with pressure gauges 19 and 20 for measuring the gas pressure, and the electric furnace 13 has a temperature for measuring the temperature of the reducing gas flowing through the reaction tube 12. A total of 21 is provided.

On the sample stage 11 of the test apparatus 10, after placing a sample in which a sintered ore 22 having a particle size of 10 to 15 mm is sandwiched between coke 23 having a particle size of 40 to 50 mm, the air cylinder 15 is operated, A load was applied to the sample via the cylinder rod 16.
In this state, the temperature in the electric furnace 13 is raised, a reducing gas is introduced into the reaction tube 12 by the introduction pipe 17, and the reducing gas that has contacted the sample through the hole of the sample stage 11 is discharged from the discharge pipe 18. Discharged to the outside. Note that the temperature of the reducing gas in contact with the sample is controlled by the electric furnace 13 while monitoring the thermometer 21 so that the temperature of the reducing gas is raised according to the temperature rising pattern shown in FIG.
The test results are shown in Table 1.

In Table 1, the dripping start temperature is measured by a thermometer 24 attached to the reaction tube 12 in the vicinity of the saucer 14, by melting the sintered ore 22 on the sample stage 11 and dropping it on the saucer 14. It is the value.
The softening start temperature is a measured value of the thermometer 21 when the cylinder rod 16 moves downward in accordance with the softening of the sintered ore 22 in the process of increasing the temperature of the reducing gas.
The total pressure loss is the total pressure loss from the time when the sintered ore 22 starts to soften until the reducing gas passing through the electric furnace 13 reaches 1500 ° C. The pressure difference between the pressure gauge 19 and the pressure gauge 20 It is. The total pressure loss is a value obtained by integrating the pressure difference of the sample layer from the start of softening to the start of dropping until the reducing gas reaches 1500 ° C. at intervals of 15 seconds.

It was confirmed that the sinters of Examples 1 to 3 in which the alumina amount and the basicity are within the range of the present invention have the dropping start temperature within the target range of 1400 to 1420 ° C. On the other hand, the dropping start temperature of the sintered ore of Conventional Example 1 in which the alumina amount exceeds 1.2% by mass does not reach the target lower limit of 1400 ° C., and the sintering of Conventional Example 2 in which the basicity exceeds 1.65. The ore dropping start temperature exceeded the target upper limit of 1420 ° C.
In addition, it was confirmed that Examples 1 to 3 had a smaller total pressure loss and better air permeability than Conventional Examples 1 and 2.
Further, it was confirmed that Examples 1 to 3 had less pressure loss of sintered ore and better air permeability than Conventional Examples 1 and 2. This seems to be because the difference between the softening start temperature and the dripping start temperature of the sintered ore became narrow.

Next, the Example which used the manufactured sintered ore for the burning operation of the blast furnace with an internal volume of 5700 m < ³ > is described.
As with the conventional blast furnace start-up, prior to firing, sintered ore having the components shown in Example 3 in Table 1 was filled into the furnace, and supply of hot air into the blast furnace furnace was started to perform the firing operation. . As a result, in a stable state without any trouble, it became possible to shift to a blast volume level equivalent to normal operation on the third day from the start of the ignition.
From the above, at the time of start-up of the blast furnace, by using the sintered ore of the present invention, the enlargement of the cohesive zone formed in the blast furnace furnace is suppressed, the air permeability in the blast furnace furnace and It was confirmed that liquid permeability was secured and the blast furnace could be started up stably and at high speed.

As described above, the present invention has been described with reference to one embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and is described in the claims. Other embodiments and modifications conceivable within the scope of the above are also included. For example, a case where the start-up sintered ore after the blast furnace repair of the present invention is configured by combining some or all of the above-described embodiments and modifications is also included in the scope of the present invention.

It is explanatory drawing which shows the relationship between the dripping rate of the melt by use of a sintered ore, and dripping start temperature. It is explanatory drawing which shows the relationship between the amount of alumina of a sintered ore, and dripping start temperature. It is explanatory drawing which shows the relationship between the basicity of a sintered ore, and dripping start temperature. It is explanatory drawing of the test apparatus for measuring the dripping start temperature of the sintered ore which concerns on an Example. It is explanatory drawing which shows the temperature rising pattern of the reducing gas of the test apparatus.

Explanation of symbols

10: test apparatus, 11: sample stage, 12: reaction tube, 13: electric furnace, 14: pan, 15: air cylinder, 16: cylinder rod, 17: introduction tube, 18: discharge tube, 19, 20: pressure gauge , 21: thermometer, 22: sintered ore, 23: coke, 24: thermometer

Claims (1)

When the modified blast furnace is started up, the sintered ore alternately charged with coke in the blast furnace is composed of 0.8 mass% or more and 1.2 mass% or less of alumina, and a basicity of 1.3 or more and 1.65. Start-up sintered ore after blast furnace refurbishment, characterized by:

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