JPS61133306A - Production of pig iron controlled of silicon content - Google Patents

Abstract

PURPOSE:To permit the control of the Si content of the molten iron to be tapped from a blast furnace in blast furnace operation by incorporating part of the coke used at a prescribed coke ratio in the form of middle lump coke into an ore layer and controlling the incorporating ratio thereof. CONSTITUTION:Part of the amt. of the coke used in the blast furnace operation in which iron ore and lump coke are alternately charged at the prescribed coke ratio into the blast furnace is incorporated as 5-25mm middle lump coke into the ore layer and the balance is charged alternately with the ore in the laminar state into the blast furnace. The Si content in the molten iron to be tapped from the blast furnace can be adjusted as desired to the value approximate to a target value by controlling the ratio of the middle lump coke to be incorporated into the ore layer. The amt. of the middle lump coke to be incorporated into the ore is made 10-25% of the total amt. of the coke, by which the Si content in the molten iron to be tapped is made to value as low as 0.08-0.10%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing pig iron with controlled silicon content, and a method for producing pig iron with appropriately controlled silicon content, and also enables production of such pig iron at low cost. I am trying to provide a method.

Industrial applications and production of pig iron with controlled content Conventional technology Controlling the amount of pig iron extracted from the blast furnace has been extensively studied for a long time.

That is, the following two situations can be considered as the mechanism by which & is transferred into the pig iron in the blast furnace.

■ StOt in the slag is CK in the pig! is reduced to L of the following formula, and & is present in the hot metal.

SLO, (4)+20 4St+ 2CO. (2)■
SLO2 in the ash of the coke directly reacts with the coke at high temperature to form the following formula, producing L-StO gas, a. i0 gas is reduced to C in the pig iron and & enters into the hot metal.

sto, (t.s) 10(s)−+sto(g)
+CO(g)sto(X)+C4,! W +
Co(g) In addition, in all of the above ■■, in the lower region of the feather loe, 34 + 2 Fao 45tOH + 2 Fg, M + 2
&0→,! 0. As shown in + 2 &, & is oxidized and the & in the pig iron decreases, but the & in the pig iron is determined by taking into account the balance of these reactions.

Therefore, in order to control the amount of sintered ore in this process, the amount of sintered ore added to the charge was increased, or the basicity of the sintered ore was increased, and 114i0 was added to the charge. Improving the properties of the charge, such as adding moisture to the blast or reducing the blast by 1 degree at the tuyere tip, increasing O slag basicity, decreasing hot metal temperature, mill scale from the tuyere tip, etc. Some methods have been proposed, such as oxide injection.

Problems to be Solved by the Invention However, the above-mentioned conventional techniques have their own problems and cannot be considered as a preferred control method. That is ■
However, it increases the cost, and there is an upper limit to the increase in basicity in sintered ore, so it has the disadvantage that there is no precise control. Either increasing the amount of gold is necessary and increasing the cost, or there are restrictions on equipment, resulting in the same disadvantages as in (2). However, θ is naturally limited because it affects the viscosity of the slag, and method (2) is limited in terms of both tapping and slag tapping, so a sufficient reduction in Sc cannot be achieved. Not only is the operation considerably complicated, but it is also subject to the same restrictions as [phase] and cannot be controlled freely and accurately.

``Structure of the Invention'' The present invention has been devised after repeated studies in view of the above-mentioned actual circumstances, and is a method of forming an ore layer and a coke layer in a blast furnace. In tapping the ore to coke ratio necessary for stable operation by alternating charging and forming, -Ht-5 to 25 m of the tth total coke amount to obtain the above ore to coke ratio.
+ Use the medium lump coke as a medium lump coke, mix the medium lump coke into the above-mentioned ore layer, and control the reduced pig iron content obtained by increasing the ratio q° of the mixed medium lump coke amount to the total coke amount. This is a method for producing pig iron with controlled silicon content.

The medium coke of f'L 95 to 25 m1 mixed into the working ore layer is uniformly distributed in the ore layer, and when the coke layer reaches the softened cohesive zone in the lower part of the blast furnace. The load of L is borne by the upper charging material.

thus avoiding close contact between molten metal and coke,
Limit zero carbon into the metal in the zone. If zero carbon into the metal is restricted in this way, the amount of carbon in the pig iron will also be restricted due to the amount of carbon in the metal. In the experiment, as mentioned above, the amount of nt medium lump coke mixed in ore I- and this pig iron & Jl show a nearly regular change, and therefore, the mixing of this medium lump coke in the total coke amount. It is possible to appropriately control and predict the amount of inkstone in the pig iron that can be obtained at a certain rate.

EXAMPLES The present invention will be further explained in accordance with the above-mentioned work.The present inventors have made detailed studies and speculations regarding tapping low-stack hot metal from a blast furnace. & Migration mechanism ■■ In any case, it can be said that those reactions do not proceed unless the C in the pig iron reaches a certain level. However, in a blast furnace, ore and coke are charged from the top of the furnace and are gradually sent to the bottom, where the ore is preheated, reduced, softened, and melted to be tapped. However, if the coal speed is controlled to 1-5tt in the pig iron,
- Estimated to be controllable.

Therefore, we have repeatedly studied how to control the rate of decoalization into the metal during the above-mentioned process, and have experimentally determined that the load after the ore layer between the coke layers has shrunk to about 70 to 80% and has softened and fused after 90 minutes. It is known that this phenomenon occurs when the metal and coke are brought into close contact during compression. Therefore, the process is designed to apply almost no load, which is the cause of the 8 coal, and to at least reduce the contact between the metal and coke. ．． 'By eliminating the cause of close contact, Elimetal's meltdown can be avoided and 8 coals can also be avoided, and by controlling such loads, S
Can control Lf.

In other words, in this process, there is a load iL?
! - As a result of considering a control method, we came up with the idea of mixing an appropriate amount of coke into the above-mentioned solid ore layer, and using this mixed coke to support the load, the metal If close contact between coke and coke under high temperature conditions is avoided, no special additives are required.
Also, I am fully aware that it is possible to avoid or limit 8 carbon to metal by a simple construction method, and prevent the accompanying migration to metal.

It goes without saying that it is preferable that the amount of coke mixed into the above-mentioned solid ore layer be at least a certain amount, but it is also preferable to use medium lump coke of 251111 or less in a range that does not impede the permeability. It can be said that it is significant in achieving the above objective by uniformly distributing it in the ore J4 with a relatively small amount of mixing. In other words, it has been said that coke of 251111 or higher should be used as the coke for use in blast furnaces, and specifically, when producing this coke TL, it is sieved at 25111m and 1'F:
Below is a by-product that can be used for purposes other than blast furnace charging as coke that is less than half the cost and is sufficiently low to be charged into a blast furnace. This product can advantageously achieve the object of the present invention when used as the coke mixed with the ore layer, and can also be effectively applied to the purpose of tapping iron at low cost. In this case, the coke particle size is generally 5 to 251a1. Preferably it is 8 to 25 ml (hereinafter referred to as t'Lt-medium lump coke). Regarding the amount of coke mixed in, it is natural that it is not preferable to use extra coke, and the fuel ratio is 500 to 9/T-Pig or less, especially 490 Yu/T-P.
ig or less, 460 latitude/T-Pig or more is stable in the conventional method. It has been confirmed that a reduction in iron content of around 20% can be obtained by mixing about 2% of the total coke into the ore layer and using the above-mentioned L-sized coke gold even when the content is 71%. Regarding the upper limit, as the amount of coke mixed in the ore layer increases in this process, the amount of coke layer between the ore layers decreases, which affects the original I-ss passage characteristics of the coke. It is preferable to set the food content to 30% of the amount. The results of experiments conducted by specifically varying the amount of coke mixed in the ore layer in this range are summarized together with comparative examples (coke mixed in the ore layer: 5$), as well as the range of variation. This is the attached drawing, which shows the amount of coke mixed in.
f) It is obvious to obtain a well-ordered low & pig iron.

Non-inventive method K J: To explain a specific operational example of
1 Taku/T-Pig and 7 is ore to coke ratio (0/C)
When operating at 1 in 1, the pig iron SL il'z 0.
In order to set 18% -p, 3.5% of the total amount of coke according to the previous I0/C was mixed into the ore layer as 8~25111110 medium lump coke and operated. The coke as coke snow between ore layers is conventional L coke of 25101 or higher.

However, the result of the &minute tljIII determination for the pig iron tapped from the blast furnace operated in this manner was 0.18%, which approximately hit the target st value.

In addition to this, the total coke amount t as a charging raw material
-483H7T-pig and 7to/CKJ: When operating, the aim is to set the pig iron volume & amount to 0.10%, and 10% of the total coke amount according to the above 0/CVc.
It was poured into the ore layer as medium coke of t-8 to 251111 and introduced into the furnace.

The coke for the coke layer is the same as above, but it is operated in this way,
We measured 3 minutes of the iron tapped from the blast furnace and 7 tons
The yield was 0.105%, and it can be said that the target and amount were fully met as described above.

It is clear from the attached drawing that if the target is 0.10% or less, the mixture rate of medium lump coke will increase, but the decrease in & will be small.For example, if the mixture rate of medium lump coke is 25 Even if the percentage is 5trio and os%8i degrees, the actual coke mixing rate is within the range of 10 to 25%, and in both cases, the & in the pig iron is 0.0.
In addition, as the amount of coke mixed in the ore layer increases, the gas flow distribution in the blast furnace tends to be a central flow. ``Effects of the Invention'' As explained above, when the present invention is applied, the central flow is suppressed.
It is possible to tap iron with appropriate control, and the total amount of coke is equal to or less than that of the conventional method, and the control objective is achieved without the need for special additives or complicated control operations. Since favorable control results can be obtained by using medium-sized coke kumquats of 25 or less in the bed, it is an invention that can sufficiently reduce costs and has great industrial effects.

[Brief explanation of the drawing]

The drawing shows the technical contents of the present invention, and is a chart summarizing the relationship between the percentage of lump coke mixed in the ore layer and the feces in the pig iron, as well as the range of variation, according to the method of the present invention and the conventional method. Patent applicant: Nippon Kokan Co., Ltd. Inventor: Kazuhiro Furukawa Unit weight: Kodo Wata Hideomi Kamanaka

Claims (1)

[Claims] When tapping the ore to coke ratio necessary for stable operation by charging ore layers and coke layers alternately in the blast furnace, a part of the total amount of coke to obtain the ore to coke ratio is Use it as a medium lump coke of 5 to 25 mm, mix the medium lump coke into the above-mentioned ore layer, and control the Si content in the pig iron obtained by the ratio of the mixed medium lump coke amount to the total coke amount. A method for producing pig iron with controlled silicon content, characterized by: