JPS6314810A - Production of pig iron - Google Patents

Abstract

PURPOSE:To produce a molten iron with high thermal efficiency from raw materials having arbitrary grain sizes by packing ore and carbonaceous material into plural units of iron making furnaces, melting and reducing the core in one iron making furnace and preheating the ore and carbonaceous material in the other iron making furnace by the by-produced gas thereof. CONSTITUTION:The ore and carbonaceous material 6 are preliminarily packed through respective charging ports 2, 2 into plural units of the iron making furnaces A, B. The by-produced gas 10 from another suitable furnace is first introduced from a tuyere 3 into the iron making furnace A to preheat the ore and carbonaceous material 6 in said furnace and thereafter, a covered gas 9 is obtd. from a gas recovering port 4. An oxygen-contg. gas 8 is introduced into the furnace from said tuyere 3 after the end of the preheating. The carbonaceous material and ore are thereby burned, reduced and melted. While the molten iron 7 formed in such a manner is discharged together with molten slag from a tap hole 5, the gas 10 to be by-produced simultaneously is recovered from the port 4. The by-produced gas 10 is blown into another iron making furnace B from the tuyere 3 thereof to preheat the ore and carbonaceous material therein. The by-produced gas 10 is exchanged with the oxygen-contg. gas 8 after the preheating and thereafter, the above-mentioned operation is repeated.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing pig iron, and in particular, to a method for producing pig iron, in particular, a method that uses a plurality of iron making furnaces filled with ore and carbonaceous materials, and separates melting and preheating. Regarding a pig iron production method characterized by (conventional technology) A method for producing hot metal by reducing and melting iron ore is:
Various methods are known today, such as:

Blast furnace method: This method is the mainstream of current ironmaking methods.
It is located in a countercurrent reactor filled with lump ore and lump coke, that is, a blast furnace, and reduction and melting are performed using reducing gas. This method has high thermal efficiency. However, since the reducing gas passes between the lump ore and the lump coke in sufficient contact with them, the raw material charge for these is a sized, high-strength material to ensure air permeability. The problem is that it requires Pretreatment of such a charge requires large-scale equipment, which is unsuitable for small-scale steel manufacturing.

Smelting reduction method: This method uses a molten iron bath furnace to burn carbonaceous material with oxygen, and uses the generated gas and heat to melt and reduce ore to produce pig iron. Since this method does not require pre-treatment of the ore, it may be easier to implement than the furnace method.

However, because the reactor is of a homogeneous mixing type, or in a state where molten iron can exist stably (temperature is about 1500℃,
Since the ratio of COt/(Co + co□) is about 20%), the thermal efficiency is low. Therefore, it is difficult to reduce the fuel ratio per ton of hot metal to less than 1000 kg/ton.

Also, if a large amount of gas is used, the fuel ratio will decrease, but
In that case, a large amount of FeO is mixed into the slag, reducing the iron yield and causing significant wear of the refractory t1.

Therefore, this method has never been put to practical use.

Functional separation method: This is a method that separates the functions of reduction and melting and smelting in the molten iron manufacturing process into two furnaces, and was developed with small-scale iron manufacturing in mind. Example: Special Publication No. 59-18453, Special Publication No. 18453, Special Publication No. 18453
-13401, Special Publication No. 59-18443.

Typical examples include the SC method, the iron casting method, and the KR method, and the relationship between the single furnace and the smelting furnace in these methods is summarized in the following table.

Table 1 Due to functional separation, gas by-produced in the smelting furnace is used for preheating and reducing raw materials in the reduction furnace, improving gas utilization efficiency.
It becomes possible to lower the fuel ratio. However, in either method, the reduction furnace and/or the smelting furnace use a specific reaction tank to fulfill a specific role, and in a specific state, such as a well-ventilated packed bed in a shaft furnace. , in a fluidized bed a fluidized bed must be maintained. In addition, the charging raw materials are charged into the smelting furnace after preliminary reduction, and transporting and handling them is a cumbersome task.

Therefore, depending on each process, pre-processing including sizing of the raw material and I1 rotation operation for stabilization are required, and as a result, large-scale and complicated equipment is required.

(Problems to be Solved by the Invention) Therefore, the purpose of the present invention is to produce hot metal without using high-strength sized raw materials as in the blast furnace method, and with thermal efficiency comparable to the blast furnace method. The aim is to provide a method that allows for

(Means for solving the problem) In order to achieve this objective, the present inventors conducted various studies and found that the concept of the above-mentioned functional separation method was the most promising. After further consideration, we found that
The present invention was completed based on the knowledge that by having the same furnace refueling function, the problem of transferring the charged material could be avoided, and the operation would become more stable by simply switching the blowing gas.

Here, the gist of the present invention is to use a plurality of iron making furnaces filled with ore and carbonaceous materials, blow gas containing oxygen from the lower tuyere of the iron making furnace (al-), The ore is heated, reduced, and melted using the resulting force to produce hot metal, and the by-product gas is recovered from the steelmaking furnace and blown into it through the lower tuyere of another steelmaking furnace. Preheating the ore and carbonaceous material filled in the furnace, then (1)
) This is another method for producing pig iron, characterized by switching the blown gas from the lower siding of the iron-making furnace to a gas containing oxygen, and repeating the operations (al and (bl) described above.

Here, the ore and carbonaceous material have undergone preliminary treatment such as ore beneficiation and deashing as necessary, and the particle size is not particularly limited, as long as it can ensure the required air permeability when filled into the furnace. . Generally, any charging material has a diameter of 1 to 50 mm.
A particle size of about 1I11 is sufficient. Practically speaking, so-called coarse ore may be sorted through a 51 sieve and the sieved portion may be used as a raw material.

As carbonaceous material it is preferred to use a mixture of coke and coal. On the other hand, conventional auxiliary materials such as graystone are used.

In the case of the present invention, since the charge material is not transferred between the furnaces, there is no problem such as particle size deterioration of the charge material as seen in the conventional method, and the air permeability can be easily maintained at 6. The form in which these raw materials are charged into the furnace is not particularly limited, but it is preferable to charge auxiliary raw materials such as carbonaceous material and limestone first, and then place ore thereon.

Initially, from the lower part of the steelmaking furnace, the preheating gas is 8:1.
Raw gas is blown in, but after preheating is completed, the blown gas is switched to oxygen-containing gas. If sufficient time is required for preheating, the preheating time for each steelmaking furnace can be increased by using a large number of steelmaking furnaces for preheating at the same time.

The oxygen-containing gas is typically oxygen gas, which is blown into the furnace through the tuyere, but may be auxiliaryly blown in through a lance from the upper part of the furnace, if necessary.

(Operation) Next, the present invention will be described in more detail with reference to the accompanying drawings.

The illustrated example shows a case where two iron making furnaces A and B are used.

In FIG. 1, the furnaces ASB are each prefilled with ore and carbon material 6 via charging ports 2.2. When the furnace is first preheated, by-product gas from another appropriate furnace is first blown into the furnace through the tuyere 3. In the figure, reference numeral 9 indicates the recovered gas after preheating. After the preheating is completed, this gas is switched to oxygen-containing gas 8 to burn, reduce, and dissolve the carbon material. At the same time, a by-product gas 10 is recovered from the gas recovery port 4 and blown into the tuyere 3 of another furnace B.

Like the furnace A, this furnace B is also filled with ore and carbon material 6. Preheating in furnace B is continued until melting in furnace A is completed. After preheating, the blowing gas is switched, while in the furnace A, the molten iron flow 7 flows into the tap hole 5 together with the slag.
It is collected from the ground and filled with ore and carbonaceous material. After the introduction of oxygen-containing gas in furnace B is started, the operations for the furnace described above are repeated in furnace B as well.

FIG. 2 is an explanatory diagram that also shows the operating order of furnaces A and B. As can be seen from Figure 2: (1) While the raw materials (ore and carbonaceous materials) are preheated to the furnace, the preheated raw materials are melted and smelted in the furnace B, and the by-product gas is transferred to the furnace A. Used as preheating gas in

(2) When the melting and smelting operation is completed in Furnace B, the pig iron and slag are extracted, new raw materials are charged, and the roles of Furnace A are switched to smelting operation and Furnace B to preheating operation. Note that the melting and smelting operation is performed by blowing oxygen-containing gas into the furnace and using the heat generated by burning carbonaceous materials with oxygen.

As described above, according to the present invention, preheating in each steelmaking furnace,
! ! ui1! Both operations are conducted in batch mode.

Therefore, the raw material does not need to be unloaded in the furnace or undergo specific movements such as flow, so restrictions such as particle size and strength of the raw material are relaxed, and inferior quality raw materials can be used.

Furthermore, by using gas by-produced during the steelmaking operation for the preheating operation, the gas utilization rate can be improved and the fuel ratio can be lowered.

Next, the present invention will be explained in more detail with reference to Examples.

Example In this example, iron ore, carbonaceous materials, and limestone, which are summarized in Table 2 below, are charged into an apparatus equipped with two iron-making furnaces shown in Fig. 1, and iron-making is carried out. The operation was carried out. The shapes and dimensions of the steelmaking furnace were as shown in Table 3.

Table 2 " Note) Umbrella: Use No. 51 sieve top.

Furnace 1 Main body: 2 cylindrical furnaces with a diameter of 2 m and an iA width of 5 Tuyere: Diameter 50 mm φ x 4, installed on the side wall of the furnace bottom + 1° 5 m Acid feed port: 1 thrust type from the top of the furnace Inlet: 1 installed at the top of the furnace Gas recovery port: 1 installed at the top of the furnace In both furnaces, a mixture of coke, coal, and limestone was charged sequentially from the hearth, and ore was charged on top of it.

Immediately after preheating is completed, from the tuyere and acid inlet of one of the furnaces,
Refining operation was performed by blowing oxygen gas at a total rate of 688 Nm/h. During the refining operation of one of the furnaces, the refining byproduct gas recovered from the upper part of the furnace was blown into the furnace through the tuyere of the other furnace to preheat the charged raw material.

During the refining operation, all of the raw material in the refining furnace was melted down in about 2 hours, and the refining was completed. By-product gas is from the initial stage of refining to 8
00℃, final stage 1400℃, average composition: 00-70%
, CO□ ~14%, H, ~13%, H20≧5%, N2
It was ~0.5%.

When smelting furnace byproduct gas having such a composition is blown from the tuyeres,
The furnace top gas temperature is room temperature at the beginning, ~800°C at the end, and the average composition is ~52.6% CO, ~37.1% CO, ■! ~
9.7%, N, ~0.6%, amount is 2315 N+d/h
Met.

The results of this example are summarized in Table 4.

Sprout and 1 cycle operation time: Refining 2 hrs, preheating 2 hrs = 4 hrs
Oxidation: Refining 2hrs x 1375N m/hr
= 275ON g Tapping amount = 10 tons 1500℃ (C-4.5%, Si = 0.5%, Mn = 0.1
%, P = 0.12%, S = 0.03%) Slag m: = 2.1 tons 1550℃ (CaO = 4
5%, 5iOz=35%) Recovery gas: =9260 N
rrr (Calorie 1830kcal/Nr+?) Dust in gas: Total 170kg Ore ratio: 1470kg/Limestone: 177kg/Fuel: 600kg/L Coke: 300
kg/coal: 300kg/l Ot: 275N/recovered gas: 1695Mcal/rawhide 10t/cycle x cycle/4hrs x 24 =
60 kernels/d Furnace volume 16M' x 2 = 32m3.
, , Tapping ratio: 1.88 t/dm' (Effect of the invention) As clarified in the above-mentioned examples, two smelting furnaces are used according to the present invention, batch charging is performed in both furnaces, and one During refining, on the other hand, if a method is used in which hot metal is produced by preheating using refining by-product gas and repeating preheating and refining in two furnaces, (1) unloading, fluidization, etc. Since it is a batch operation mode in which there is no need to specify the movement state of the raw material within the furnace, particle size control of the raw material is relaxed, so there is no need to control the upper and lower limits of particle size as in the blast furnace method. In the example, the crude ore could be used by simply separating it with a sieve with a lower limit of 5 dia.

(2) Similarly, there is no need to limit the strength of raw materials. Therefore, lump coal can also be used. Although the coal is pulverized during preheating, there is no problem in ensuring ventilation during the preheating operation time (~2 hr).

(3) Since refining byproduct gas can be used for preheating, a gas utilization rate of ~40% is possible, resulting in a fuel ratio of ~600k.
g/l can be achieved even though it is a small furnace.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically illustrating an example of the operation of the present invention; and FIG. 2 is an explanatory diagram of the order of operation of two iron-making furnaces according to the present invention.

Claims (1)

[Claims] Using multiple ironmaking furnaces filled with ore and carbonaceous materials, (a
) A gas containing oxygen is blown from the lower tuyere of the first steelmaking furnace,
Burning the carbonaceous material and using the resulting heat to heat, reduce, and melt the ore to produce hot metal, the by-product gas is recovered from the steelmaking furnace and blown into the lower tuyere of another steelmaking furnace. , preheating the ore and carbonaceous materials filled in the furnace, then (b) switching the blowing gas from the lower tuyere of the other iron-making furnace to a gas containing oxygen, and (
characterized by repeating the operations a) and (b),
Pig iron manufacturing method.