JPH01287212A - Method for charging raw material in blast furnace - Google Patents

Abstract

PURPOSE:To improve gas permeability through the laminarily charged ores and cokes in a blast furnace and to control gas distribution to radius direction at high accuracy by charging ore and coke in the furnace while limiting quantity and grain size of a part of the coke in the core. CONSTITUTION:The ore and the coke are laminarily charged in the blast furnace and a part of coke mixed with the ore is charged in the furnace. In the above raw material charging method in the blast furnace, the coke quantity mixed with the ore is made to >=50kg/ton of pig iron. Further, the grain size of the coke mixed with the ore is made to <=20mm in the case of 50kg/ton of pig iron to the coke for mixing in order to improve the reduction reaction. On the other hand, in the case of excessing 50kg/ton of pig iron to the coke for mixing, it is made to >=30mm grain size. By this method, the reaction of this coarse grain coke is restrained and the grain size thereof is secured at >=about 20mm even at the time of reaching to drip zone at lower part of the furnace, to restrain softening fused sticking of the core. Further, the gas permeability in the blast furnace is improved and O/C distribution to the radius direction and gas flow distribution to the radius direction can be controlling at high accuracy.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a method for charging raw materials into a blast furnace, and more specifically,
In a method in which ore and coke are charged in layers and a part of the coke is mixed in the ore and charged into the furnace, the amount of coke mixed in the ore and the particle size are controlled to control the blast furnace. The present invention relates to a raw material charging method that improves air permeability and gas flow distribution within a container.

[Prior Art] Conventionally, in a method of charging ore and coke into a blast furnace in layers, a method has been implemented in which small coke is mixed in ore and the mixture is charged into the furnace. This has two main purposes:

[I] Improving air permeability in the blast furnace When coke is mixed in the ore layer, there is no noticeable difference in the air permeability of the shaft compared to when coke is not mixed in the ore layer, but in the lower part of the furnace. In particular, the air permeability in the cohesive zone is significantly improved. The reasons for this are mainly the following three points.

■ The coke mixed in the ore layer preferentially causes the trusion loss reaction shown in equation (1) with the CO2 gas generated by the reduction of the ore, suppressing the decrease in the particle size of the coke charged in layers. That's true.

C0CO2→2C○ (1)■ Unreduced Fe
Even if O melts in the ore layer and forms FeO-based slag, the coke mixed in the ore layer causes a melting reduction reaction with the FeO-based slag as shown in equation (2), and the FeO-based slag The amount of hold-up is reduced and breathability is improved.

C+FeO->Fe0CO(2) (2) Since coke is mixed in the ore layer, the coke suppresses the softening and fusion of kg ore, and the permeability of the fusion layer is improved.

[II] Cost reduction by replacing coke charged in layers with small coke mixed into ore The effect of mixing coke into ore as described above is that the small lumps are large and Moreover, since small lumps are also effective for the reason (2), the particle size of the coke mixed into the ore has conventionally been 5.about.20 mm. Conventionally, these 5 to 2
By using 0 mm small coke up to about 20 kg/pt in blast furnaces, it was attempted to improve air permeability and reduce hot metal costs.

(Problems to be Solved by the Invention) However, the conventional method of mixing and charging coke into ore has the following two problems.

The first problem is that the amount of coke mixed into the ore is limited to a maximum of 50 to 9/l)t. This is because small coke of 5 to 20 mm was used as coke to be mixed with the ore.

That is, the coke mixed into the ore had to be consumed in the reaction of formula (IX2) before reaching the dropping zone at the bottom of the furnace. If unconsumed small coke flows into the drip zone, the average diameter of the drip zone coke decreases, resulting in deterioration of the permeability of the drip zone.

A study using a one-dimensional blast furnace mathematical model shows that the maximum amount of coke that can be mixed into ore, including carburizing into hot metal, is 50 kg/
pt, and in actual operation, the maximum usage was only about 20 ki/pt. For this reason, the effect of improving air permeability by mixing coke into the ore could not be sufficiently exhibited.

The second problem is related to the fact that the movable armor is used as the main control means for the distribution of the weight ratio of ore to coke (hereinafter abbreviated as 0/C) in the radial direction.

The change width of the normal movable armour-notch is 0 in the radial direction.
/C distribution changes greatly, the radial gas flow distribution inside the furnace cannot be controlled with high precision, and even if coke is mixed into the ore, the radial gas flow distribution is inappropriate, resulting in kg There were cases where breathability was not improved.

In this conventional mixed coke charging method for ore, there are problems in that the amount of mixed coke is limited and that the radial O/C distribution and radial gas flow distribution cannot be controlled with high precision. Ta.

This invention was made in view of the problems of the conventional technology, and its purpose is to significantly increase the amount of coke mixed in ore and to significantly improve the ventilation inside the blast furnace. The purpose of this paper is to propose a method for charging blast furnace raw materials that can control the radial O/C distribution and the radial gas flow distribution with high precision.

(Means for Solving the Problems) The present invention, as a means to solve the above-mentioned conventional problems, increases the amount of coke mixed with ore to 50 to 9 or more per ton of pig iron, and increases the particle size of coke mixed with ore. , 20mm for mixing coke of 50kCJ per ton of hot metal
The gist is as follows, and for mixing coke exceeding 50 kg per ton of pig iron, the length shall be 30 mm or more.

[Function] The reason why the amount of coke mixed with the ore is set to 50 yen or more per ton of pig iron is to improve the ventilation inside the furnace by significantly increasing the amount of coke mixed in the ore. .

Of this coke for mixing, 50kq/l)t has a particle size of 20
The reason why the small coke size is less than mm is to preferentially cause the reaction of formula (IX2).

In addition, the reason for using lump coke with a particle size of 30 mm or more for mixing coke exceeding 50 kq/l)t is that the reaction of equations (1) and (2) above is suppressed compared to the small lump coke. Highly effective in suppressing softening and adhesion of kg ore
- Save money.

In addition,! The reason why the lower limit of the particle size of the coke for mixing exceeding i0 kg/pt is set to 30 nnn is to ensure a coke particle size of 20 mm when it reaches the dropping zone in the lower part of the furnace.゛In other words, the coke particle size in the dropping zone at the bottom of the furnace is 20 mm.
This is because stable operation of the blast furnace can be maintained if the above conditions are met.

Further, the reason why the method of controlling the radial 0/C eros by adjusting the amount of mixing coke exceeding 50 lag/pt was adopted is as follows.

When we conducted a model experiment of 1/10 of the amount of coke that falls outside the furnace, we found that the fine particles of the coke mixed in kg ore are shown in Figure 1, showing the cumulative rate of mixed coke that falls in the radial position inside the furnace. The coarse grains on the wall side showed a tendency to segregate toward the center.

In other words, by adjusting the amount of coke +30mm, the ore deposition profile remains almost constant and only the amount of coke in the core can be controlled, making it possible to control the O/C distribution with much higher precision than with movable armor. This is because the gas flow distribution in the radial direction can be controlled with high precision as a result.

FIG. 2 is a schematic diagram showing an example of the configuration of an apparatus for carrying out the method of this invention.

In other words, in the blast furnace raw material storage tank, the ore is stored in the ore tank (3).
50 kq/pt of coke is mixed with kg of ore from the small coke tank (4), and +
50 kq/pt from 30 nun lump coke tank (5)
The amount of mixing coke exceeding 100 m is cut out at the same time, placed on the charging belt conveyor (6), and conveyed to the top of the blast furnace.

The next kg of coke (particle size + 20 mm) to be charged in layers is temporarily stored in the lump coke tank (7), and the coke with particle size + 30 mm is transferred to the mixing coke tank (5) or the coke tank for layer charging (7) by switching the damper. Store and cut out.

In addition, if the amount of mixing coke of 5 to 20 mm is less than 50 kq/l)t due to coke balance, the coke size is adjusted to 5 to 20 mm by transporting it from another furnace or crushing large coke.

The blast furnace raw material (2) cut out from each raw material tank is transferred to the blast furnace (1).
After being transported to the top of the furnace and temporarily stored in the fixed hopper (8), the small bell (1
0) evenly in the circumferential direction, and by opening the small bell (10), the large bell (11) is charged.

When the raw material accumulation level (12) in the furnace reaches a predetermined level, the movable armor (13) is set to a predetermined notch, the large bell (11) is opened, and the raw material is charged into the furnace.

[Example] Table 1 shows the results of applying the present invention to a blast furnace (internal volume: 2700 m3) that performs all-coke operation with a coke ratio of 500 W/I)t in comparison with the conventional method.

In this example, commonly used coke was sieved into the sizes of 20 mm and 30 mm used in the present invention.

In addition, conventionally, in Pope, small coke of 5 to 20 mm 20
kg/pt was used by mixing it with the ore, and in the same case (2), the movable armour-knot was changed from C401 to C400, and the furnace wall 0/C was used as a power intensifying port to suppress the flow of waste on the furnace wall. Here, the subscript indicates a movable armour-notch, and the smaller the number, the closer the armor plate was set to the furnace wall, and the falling position of the raw material was moved toward the furnace wall. Then, the mixed coke amount was kept constant (20 ks/l), and the sensitivity of the radial gas flow distribution control by changing the movable armor in the conventional method was investigated.

At that time, when we measured the center gas temperature of the shaft gas sampler and the furnace wall waste temperature as indicators of gas flow distribution, we found that the gas temperature changed significantly from +80°C at the center to -20°C at the furnace wall. Although it is possible to suppress the gas flow on the furnace wall, high-precision control has been difficult.

In the conventional method (2), the movable armour-notch was the same as the conventional method, and the amount of mixed coke was increased to 60 kl/pt. However, the pressure loss in the lower part of the furnace increased rapidly, the slip frequency more than doubled, and the coke ratio deteriorated to 520/1/pt.

It was found from the results of coke sampling from the bottom of the blast furnace when the blast furnace was shut down that this was because some of the small coke for mixing with a size of 5 to 20 mm flowed into the dripping zone and the average coke diameter in the lower part of the furnace decreased. .

On the other hand, in the present invention IV, the mixed coke amount is 100 kg/p.
t, 5-20mm is 50kg/pt, +30
mm was used at 50 kg/pt. The movable armour-notch was operated at -.

As a result, the coke ratio and air blowing specifications were almost the same as the conventional Pope, and the decrease in pressure loss at the bottom of the furnace was small, but the pressure loss at the bottom of the furnace decreased significantly from 0.75 to 0.65 k, 3.7 . The frequency of slips was also less than half that of previous popes. From the temperature distribution of the shaft gas sampler, it was found that the central gas flow rose only slightly, making it possible to control the gas flow distribution with high precision compared to the conventional method ①, which uses movable armour.

In the present invention (■), the amount of mixed coke is 120 ki/pt,
Among these, particle size 5 to 20 + nm to 50 + 1/pt 1
+30mm was used for 70 +1/pt. The movable armouring was operated at a constant rate.

As a result, compared to Invention IV, due to the increase in the mixed coke depth, the pressure drop in the lower part of the furnace is drastically reduced, the slip frequency is also significantly reduced, and from the temperature distribution of the shaft gas sampler, the central gas flow is further increased only slightly. It turned out that it did.

Table 1 [Effects of the Invention] As described above, according to the present invention, the permeability of a blast furnace can be improved by controlling the particle size of coke mixed with ore and significantly increasing the amount of mixed coke. .

Further, by controlling the amount of lump coke in the mixed coke, it is also possible to control the radial O/C distribution with high precision. Therefore, in addition to the above-mentioned air permeability, the gas flow distribution in the kg radial direction can be greatly improved, which is a great effect.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the mixed coke accumulation rate at a radial position in the furnace using a scale model. FIG. 2 is a schematic diagram illustrating an example of the configuration of an apparatus for carrying out the method of this invention. 1... Blast furnace 2... Raw material 3... Ore tank 4... Coke tank for mixing with particle size 5 to 20 mm 5...
Coke tank T for mixing with particle size of 30 mm or more Furnace radial position Wall notch A

Claims (1)

[Claims] In a method in which ore and coke are charged in layers into a blast furnace, and a part of the coke is mixed with the ore and charged into the furnace, the amount of coke mixed with the ore is 50% per ton of pig iron.
20 kg or more for mixing coke with a particle size of 50 kg per 1 ton of hot metal and mixed with ore.
A method for charging raw materials into a blast furnace, characterized in that the diameter is 30 mm or more for mixing coke exceeding 50 kg per ton of pig iron.