JP2770305B2 - Feeding method for smelting reduction of iron ore - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for charging raw materials in the smelting reduction of iron ore.

[Conventional technology]

The iron smelting reduction method is a method for producing iron by reducing ore containing a metal oxide such as iron ore (iron oxide) in a molten state, and has recently attracted attention as a steelmaking technology adapted to future raw materials and energy conditions. And research and development are in progress for practical use. This smelting reduction method is expected to be a method that can realize the use of less expensive raw materials compared to the blast furnace method, omission of a pretreatment step such as agglomeration of fine ore, and downsizing of equipment.

Various processes have been proposed for the smelting reduction method, and there are various types of reduction furnaces. A typical example is a metal bath furnace type smelting reduction furnace. This is a reduction furnace for ironmaking, in which iron ore is charged together with coal and oxygen into an iron bath (molten iron) and reduced to obtain molten iron (pig iron). 10 compared to what is reduced by
It can be reduced at a rate of 0 times or more), and the equipment type is simple, so it is adopted in many processes.

An important elemental technology in the smelting reduction method is the secondary combustion ratio (% CO ₂ +% H ₂ O /% CO +% CO ₂ ) of the generated gas in the smelting reduction furnace.
+% H ₂ +% H ₂ O), high-level stabilization technology, and technology for suppressing slopping (a phenomenon in which slag, molten metal, and granular iron spurt out of the reduction furnace suddenly).

The effect of the improvement in the secondary combustion ratio is to reduce the carbon unit consumption, that is, to reduce the molten iron production cost, as shown in FIG. Further, there is an advantage that the load of the pre-reduction of iron ore by the exhaust gas is reduced, and the cost of ancillary equipment such as a pre-reduction furnace is reduced.

On the other hand, the occurrence of slopping has an adverse effect on production and molten iron production costs, such as a stoppage of operations and a decrease in iron yield. Therefore, it is necessary to eliminate slopping.

FIG. 2 schematically shows a conventional metal bath furnace type smelting reduction method, in which iron ore, carbonaceous material and flux are charged into a metal bath in a smelting reduction furnace, and a top blowing lance 2 and / or a bottom are used. DC O ₂ (for decarburization O ₂ ) and PC O ₂ (for secondary combustion)
O ₂ ) is blown, and a reduction process is performed. That is,
DC O ₂ To generate CO gas and heat, and PC O ₂ To convert CO gas into CO ₂ gas and generate a large amount of heat (Q ₂ > Q ₁ ) to secure the heat required for reduction.

Here, when the molten metal (granular iron) scatters in the region of PC O ₂ (secondary combustion zone), a reaction of CO ₂ + C (in the molten metal) = 2CO−Q ₃ (3) occurs and the secondary combustion ratio To reduce. for that reason,
Conventional secondary combustion ratio improvement measures, increasing the secondary combustion amount of O _2, in particular of reducing the scattering of improving the granulated metallic iron of PC O ₂ amount / [DC O ₂ amount + O ₂ The amount of iron ore] ratio Therefore, the amount of gas blown from the bottom blowing nozzle 1 was optimized. In order to make the secondary combustion zone higher than the area where the granular iron scatters, the height of the lance was increased.

The metal bath furnace type smelting reduction method has a high reaction rate as described above, so that the supply rate of oxygen, carbonaceous material, and iron ore can be increased, and as a result, there is a high possibility that the equipment can be downsized.

[Problems to be solved by the invention]

However, in the conventional method, as these feed rates increase, the secondary combustion ratio decreases and becomes unstable, and the slopping tends to occur more frequently.

For this reason, in the past, the supply rate of carbon materials etc. was reduced at the expense of productivity, and the productivity was secured by increasing the size of the equipment, or the target value of the secondary combustion ratio was lowered, In general, there is a method of increasing the preliminary reduction rate of iron ore by using such a method. However, these methods have disadvantages that the equipment cost is high and the equipment type is complicated.

[Means for solving the problem]

In view of the problems described above, the present inventors have repeated studies on a method capable of stably operating the smelting reduction by improving the secondary combustion ratio, stabilizing at a high level, and preventing the occurrence of slopping. As a result, the following facts were found.

Conventionally, it was thought that the cause of lowering the secondary combustion ratio was mainly the scattering of granular iron into the secondary combustion zone. However, in practice, the method of charging carbonaceous materials and iron ore is more important. Turned out to be.

That is, when the carbon material is charged in an amount more than the required amount, the carbon material flows into the secondary combustion zone, and the secondary combustion ratio is reduced by the reaction of the above formula (3). Here, the required amount of carbon material is the amount of supplied O ₂ (DC O ₂ + P
CO ₂ + O _{2 in} iron ore) and the secondary combustion ratio.

On the other hand, if the amount of carbonaceous material is insufficient, [C] in the molten metal is consumed and reduced by the reaction with DC O ₂ and the like, and the amount of slag (FeO) is increased. I do. In addition, slag forming and slopping make it easier for the granular iron and the carbon material to enter the secondary combustion zone, thereby lowering the secondary combustion ratio.

That is, it is very important to always supply the carbon material input amount according to the supplied O ₂ amount without excess or shortage.

Similarly, if the amount of iron ore is too large, the molten metal [C] is reduced, and slopping occurs for the same reason as described above.
On the other hand, if the amount is too small, the amount of carbonaceous material becomes relatively excessive and not only lowers the secondary combustion ratio, but also raises the temperature of the molten metal and greatly damages the refractory.

From these facts, if the supply O ₂ amount is increased, the supply amount of necessary carbonaceous materials and iron ore naturally increases, and if the supply balance is broken even a little, the secondary combustion ratio becomes unstable,
Slopping is more likely to occur.

Conventionally, such a fact has not been known at all, and even in terms of equipment, the supply hopper of the raw material is of a normal type with one brand and one hopper. In many cases, there is no consideration for continuous supply, such as an operation mode that temporarily suspends operation, and in many cases, there is no consideration for supplying raw materials at a constant speed by a continuous cutting device, etc. As a result, the supply balance of raw materials has been disrupted,
It is considered that the secondary combustion ratio became unstable and slopping also occurred.

The present invention has been made based on the above findings, and supplies iron ore and coal continuously and at a constant supply rate into a smelting reduction furnace during a main smelting reduction treatment period, so that the raw material supply balance is always constant. The operation is performed as follows.

In the present invention, iron ore and coal are supplied continuously, that is, without interruption, at a substantially constant supply rate according to the amount of O ₂ supplied. Here, the substantially constant supply speed means
It means that it is constant except for inevitable fluctuations in the supply amount by the supply device. Further, such a continuous supply of the raw material is performed over the entire period in which the raw material supply is required.

By supplying this way the iron ore and coal according to the supplied amount of O ₂ in a continuous and constant feed rate, as described above - is high regulate a secondary combustion ratio and the occurrence of slopping It can be suppressed effectively.

During operation, to supply the raw materials into the furnace without interruption and at a constant supply rate, two or more supply hoppers for iron ore and coal are provided, and when one is empty, the other hopper is used. It is necessary to be able to supply the raw material immediately, and it is preferable that these hoppers are provided with a continuous cutting device such as an electromagnetic feeder or a rotary feeder.

〔Example〕

Using a metal bath furnace type (converter type) smelting reduction furnace (5 ton, inner volume of brick: 7 m ³ ), smelting reduction was performed by a method as shown in FIG. 3 (conceptual diagram). That is, after charging the molten pig iron of 4ton the furnace, bottom-blown N ₂ gas from the nozzle 1 450Nm ³ / hr, horizontal blown N ₂ gas from the nozzle 2 250 Nm ³ / hr, top-blown from the lance predetermined amount of DC O ₂ and PC O ₂ was blown into each iron ore (particle size 1
~ 20mm) and carbon (30% volatile, FC [fixed carbon] 56
%, A particle size of 3 to 20 mm) was charged into the furnace by free fall by the following various charging methods, and the furnace was operated. The operation was performed with a slag amount of 800 kg.

Comparative Example (1) The charging method of iron ore and coal and the amount of O ₂ supplied by the top blowing lance are as follows.

 Iron ore: Continuous supply at a constant supply rate of 50 kg / min.

Coal: 15 kg / bag every 30 seconds without using a feed hopper
Bags were charged from the upper part of the furnace.

Supply O ₂ amount DC O ₂ : 1000 Nm ³ / hr PC O ₂ : 1000 Nm ³ / hr FIG. 4 shows the change in the secondary combustion ratio during operation.
The secondary combustion ratio fluctuates greatly between 0.2 and 0.4. In this comparative example, slopping occurred 6 minutes after the start of the operation, and the operation was interrupted.

Comparative Example (2) The charging method of iron ore and coal and the amount of O ₂ supplied by the top blowing lance are as follows.

 Iron ore: Continuous supply at a constant supply rate of 50 kg / min.

Coal: As shown in Fig. 5, the feed rate is 20 minutes every 2 minutes.
The feed was changed at kg / min and 40 kg / min.

Supply O ₂ amount DC O ₂ : 1000 Nm ³ / hr PC O ₂ : 1000 Nm ³ / hr FIG. 5 shows the change in the secondary combustion ratio during operation.
The secondary combustion ratio fluctuates greatly between 0.1 and 0.5. In this comparative example, slopping occurred 15 minutes after the start of operation.

Comparative Example (3) The charging method of iron ore and coal and the amount of O ₂ supplied by the top blowing lance are as follows.

 Iron ore: Continuous supply at a constant supply rate of 50 kg / min.

Coal: After continuous supply at a constant supply rate of 30 kg / min,
As shown in the figure, the supply was interrupted on the assumption that the supply hopper became empty.

Supply O ₂ amount DC O ₂ : 1000 Nm ³ / hr PC O ₂ : 1000 Nm ³ / hr FIG. 6 shows the change in the secondary combustion ratio during operation, in which coal was supplied continuously and at a constant supply rate. During the period, the secondary combustion ratio was stable at a high level of 0.5 to 0.6, but about 2 minutes after the supply of coal was interrupted, the secondary combustion ratio dropped sharply to 0.2 to 0.3 and slopping occurred. did.

Comparative Example (4) The charging method of iron ore and coal and the amount of O ₂ supplied by the top blowing lance are as follows.

Iron ore: As shown in Fig. 7, the feed rate is 40
The input was changed at kg / min and 60 kg / min.

 Coal was continuously supplied at a constant supply rate of 30 kg / min.

Supply O ₂ amount DC O ₂ : 1000 Nm ³ / hr PC O ₂ : 1000 Nm ³ / hr FIG. 7 shows the change in the secondary combustion ratio during operation.
The secondary combustion ratio fluctuated greatly between 0.3 and 0.6, and slopping occurred 30 minutes after the start of operation.

Comparative Example (5) The charging method of iron ore and coal and the amount of O ₂ supplied by the top blowing lance are as follows.

 Iron ore: continuously fed at a constant feed rate of 35 kg / min.

Coal: The feed rate was changed every 11 minutes at 11 kg / min and 25 kg / min.

Supply O ₂ amount DC O ₂ : 700 Nm ³ / hr PC O ₂ : 700 Nm ³ / hr If the supply O ₂ amount is small as in this comparative example, the operation is performed for 2 hours or more even if the supply amount of the raw material fluctuates to some extent. No slopping occurs, and the secondary combustion ratio is 0.5 to
0.6, which is stable at a high level.

The productivity in this comparative example was 4.7 ton / D · m ³ (the number of hot metal tons that can be produced per day per 1 m ^{3 of the} brick volume).

Example (1) The charging method of iron ore and coal and the amount of O ₂ supplied by the top blowing lance are as follows.

 Iron ore: Continuous supply at a constant supply rate of 50 kg / min.

 Coal was continuously supplied at a constant supply rate of 30 kg / min.

Supplying O ₂ amount ^{_{DC O 2: 1000Nm 3 / hr}} PC O 2: 1000Nm 3 / hr 8 figure shows a change in the secondary combustion ratio in the operation, in this embodiment was carried out for 2 hours operation, No slopping occurred, and the secondary combustion ratio was as high as 0.55 to 0.65. The productivity was 6.7ton / D · m ^3.

Example (2) The charging method of iron ore and coal and the amount of O ₂ supplied by the top blowing lance are as follows.

 Iron ore: Continuous supply at a constant supply rate of 60 kg / min.

 Coal: continuously supplied at a constant supply rate of 35 kg / min.

Supply O ₂ amount DC O ₂ : 1200Nm ³ / hr PC O ₂ : 1100Nm ³ / hr In this example, the operation was performed for 2 hours or more, but no slopping occurred, and the secondary combustion ratio was as high as 0.55 to 0.65. It was stable. The productivity was 8.0ton / D · m ^3.

Example (3) The charging method of iron ore and coal and the amount of O ₂ supplied by the top blowing lance are as follows.

 Iron ore: continuously fed at a constant feed rate of 40 kg / min.

 Coal: Continuous supply at a constant supply rate of 23 kg / min.

Supply O ₂ amount DC O ₂ : 800Nm ³ / hr PC O ₂ : 800Nm ³ / hr In this example, the operation was performed for 2 hours or more, but no slopping occurred, and the secondary combustion ratio was as high as 0.55 to 0.65. It was stable. The productivity was 5.3ton / D · m ^3.

Example (4) The charging method of iron ore and coal and the amount of O ₂ supplied by the top blowing lance are as follows.

 Iron ore: Continuously fed at a constant feed rate of 75 kg / min.

 Coal: continuously supplied at a constant supply rate of 40 kg / min.

Supply O ₂ amount DC O ₂ : 1350 Nm ³ / hr PC O ₂ : 1350 Nm ³ / hr In this embodiment, no slopping occurs even if the operation is performed for 2 hours or more, and the secondary combustion ratio is as high as 0.55 to 0.65. It was stable. The productivity was 10.0ton / D · m ^3.

As can be seen from each of the comparative examples, when the supply rate of the raw material fluctuates or the supply is interrupted, slopping occurs and the secondary combustion ratio also fluctuates greatly, so that high-order stability cannot be expected. However, even if the raw material supply amount fluctuates as in Comparative Example (5), stable operation is possible if the supply O ₂ amount is small. However, if the supply O ₂ amount is small, the productivity naturally increases. Deteriorate.

On the other hand, by supplying the raw material continuously and at a constant supply rate as in each of the above-described embodiments, stable operation and high productivity can be obtained.

〔The invention's effect〕

According to the present invention described above, it is possible to stabilize the secondary combustion ratio at a high level while ensuring high productivity, reduce the production cost of molten iron, prevent slopping, and stably operate the smelting reduction. Can be realized. In particular, according to the method of the present invention, higher productivity of molten iron can be obtained as compared with the conventional blast furnace method and smelting reduction method. Sunawa was, productivity of ordinary blast furnace process is about 2.0~2.3ton / D · m ^3, also O instead of hot air
_The so-called oxygen blast furnace method with the addition of ₂ (Ref.
7], in S80), reports have been made that max5.1ton / D · m ^3. Further, as shown in Comparative Example (5), the production amount that can be operated by the conventional smelting reduction method is at most 4 to 5 ton / D · m ³ . On the other hand, according to the method of the present invention, 6ton / D
A productivity of m ³ or more can be easily obtained. Further, according to the present invention, since such high productivity is stably obtained, the smelting reduction furnace and its accompanying equipment can be miniaturized, and the equipment cost can be kept low.

[Brief description of the drawings]

FIG. 1 shows the effect of the secondary combustion ratio in the smelting reduction on the basic unit of carbon material. FIG. 2 schematically shows a conventional metal bath furnace type smelting reduction method. FIG. 3 schematically shows a processing method in the embodiment. 4th
The figure shows a change in the secondary combustion ratio during operation in Comparative Example (1). FIG. 5 shows a change in the secondary combustion ratio during operation in Comparative Example (2). FIG. 6 shows a change in the secondary combustion ratio during operation in Comparative Example (3). FIG. 7 shows a change in the secondary combustion ratio during operation in Comparative Example (4). FIG. 8 shows a change in the secondary combustion ratio during operation in the embodiment (1).

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-201406 (JP, A) JP-A-63-140010 (JP, A) JP-A-63-195206 (JP, A) (58) Investigation Field (Int.Cl. ⁶ , DB name) C21B 11/00-13/14

Claims (1)

(57) [Claims] 1. A method for charging raw materials in the smelting reduction of iron ore using coal as a carbon material, comprising continuously and substantially constant supply of iron ore and coal into a smelting reduction furnace during a main smelting reduction process. A raw material charging method for smelting reduction of iron ore, characterized in that the raw material is supplied at a speed.