JPS602613A - Smelting method of ferrous alloy by melt reduction - Google Patents

Abstract

PURPOSE:To obtain inexpensively a ferrous alloy of the component condition desirable for post-stages by matching a preliminary reduction furnace suitable for a stationary operation and a melt reduction furnace of a top and bottom blown converter type suitable for a non-stationary operation. CONSTITUTION:Two units of reaction vessels of a top and bottom blown converter type and a preliminary reduction furnace which preheats and preliminarily reduces ore contg. iron oxide or the molding thereof by the high temp. waste gas from said vessels are combined. The operation in said reaction vessels is then divided to the two for the period when the preheated and the preliminarily reduced ore or the molding thereof is charged and for the period when the same is not charged; at the same time, the operation cycles are shifted from each other. The preheated or preliminarily reduced ore or molding is charged into either of the reaction vessels of the top and bottom blown converter type.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing an iron-based alloy by a smelting reduction method.

The iron-based alloy referred to here is hot metal or semi-hot metal (C: 1.
Fe-C alloys such as 5-4%), Fe-X-C (X:Mn) such as ferrochrome, ferromanganese.

It refers to alloys such as Si...), and all of them have the characteristics of being intermediate products for manufacturing steel materials.

(Prior Art) All of these alloys have been manufactured by smelting ore in a furnace with strong reducing power, such as a blast furnace or an electric furnace. The common feature of these furnaces is that they are shaft-type, and the reduction reaction takes place while the molten oxide drips through a bed of coke heated to a high temperature. That is, the reaction occurs continuously.

However, these methods have the following problems.

(1) In order to maintain the permeability of the packed bed, high strength ore and carbon materials are required, and the cost required to procure them is large.

(2) When electricity is used as an energy source, the energy cost is high.

(3) When the ore is poorly soluble, as in the case of ferrochrome production, the droplet dropping method cannot advance the reduction reaction sufficiently close to the equilibrium value, and the chromium content in the discharged slag is It shows a high value of ~5.

(4) On the other hand, since there are local high-temperature parts (tuyere or arc parts) in the furnace, the reduction reaction of 5Io2 occurs, and it is difficult to reduce the Si content of the resulting product. .

(5) Unless the reduction of the ore is consciously suppressed (resulting in a decrease in metal component recovery yield), it is difficult to obtain a carbon-unsaturated iron-based alloy. Methods such as decarburizing by blowing oxidizing gas into the molten metal part of the hearth are difficult to employ in shaft furnaces.

One of the methods for solving these problems is a smelting method using a top-bottom blown converter type reaction vessel. That is, while the molten alloy and molten slag are strongly stirred by bottom-blowing gas, the ore or its pre-reduced material is supplied with carbonaceous material, flux, and oxygen as reducing agents to generate heat and melt the ore. , is a method of proceeding with the reduction reaction. (Hereinafter, this will be referred to as the smelting reduction method using a full top and bottom blown converter type vessel.)
In this method, the above-mentioned problems of the shaft furnace can be solved by introducing a means of strong stirring of the molten material.

That is, (1) Freed from the restriction of maintaining air permeability of the packed bed.

(11) Primary energy can also be used directly as reduction energy for ferroalloys.

(iill Strong reduction can be used to promote the reduction reaction of oxides and bring them closer to the equilibrium value. Also, unlike a shaft furnace), the timing of supplying oxides to the smelting reduction zone and the It can be divided into periods when the supply of water is stopped and finishing reduction is performed. This also helps to reduce the amount of these component oxides in the discharged slag.

In other words, it is not a completely continuous process, but can incorporate some of the advantages of patch processing.

(V Strong stirring promotes homogenization of the temperature inside the furnace, and there are no local high-temperature areas, so the reduction reaction of 5Io2 is suppressed, and iron-based alloys with low sl content (e.g., Si hot metal, low St ferrochrome) are obtained.

However, in order to put into practical use the smelting reduction method using a top-bottom blowing converter type vessel instead of the conventional shaft type method, the following problems must be solved0 (1) From the smelting reduction furnace It is necessary to combine this with a method that effectively utilizes the sensible heat and latent heat of the exhaust gas outside the furnace.

In a shaft furnace, the charge is efficiently preheated and pre-reduced in the shaft section. In the smelting reduction method, when exhaust gas is once led out of the furnace and equipment such as a rotary kiln is used to preheat and pre-reduce the charge, it is necessary to find optimal conditions from the viewpoint of matching. Pre-reduction furnaces are originally suitable for continuous, steady-state operation. This and
The question is how to match the operation of the top-bottom blowing converter type, which can take advantage of its advantages by incorporating patch elements.

(2) Since strong agitation is a prerequisite in a smelting reduction furnace, damage to the refractory is much easier than in the case of a shaft (5) where a temperature gradient can be created. Therefore, in order to prevent damage to refractories, the slag component should be adjusted to one that is not highly corrosive (in particular, (T, Fe%) should be lowered).
It is desirable to keep the slag temperature and the slag temperature as low as possible.

-The lower the temperature, the lower the reduction amount of oxide per 10,000 units of time, and the lower the reduction amount of oxide of the component in the slag (FeO + Cr
2O5' + MnO, etc.), the lower the content. Therefore, the above measures for preventing damage to refractories may reduce the productivity of the smelting reduction furnace. The question is how to reduce the load on refractories and increase the productivity of a single furnace.

(Objective of the Invention) The object of the present invention is to put into practical use a smelting reduction method using a top-bottom blowing converter type vessel instead of the conventional shaft type method for smelting and smelting iron-based alloys. It is an object of the present invention to provide a smelting reduction refining method which can solve various problems that arise in the process and can produce iron-based alloys at low cost.

(6) (Structure and operation of the invention) The gist of the present invention is to provide two top-bottom blown converter type reaction vessels, and to supply iron oxide to the high-temperature exhaust gas from the top-bottom blown converter type reaction vessels. When manufacturing iron-based alloys in combination with a pre-reduction furnace that preheats and pre-reduces the ore containing ore or its molded product,
The operation in each of the above-mentioned top-bottom blown converter type reaction vessels is divided into two periods: a period in which preheated and pre-reduced ore or its molded product is charged, and a period in which it is not charged. An iron manufacturing method characterized in that the operation cycle is shifted between the reaction vessels and the operation is carried out with preheated and prereduced ore or its molded product being charged into one of the top-bottom blown converter type reaction vessels. In the smelting reduction method using a top-bottom blown converter type reaction vessel in the smelting reduction smelting method for O-based alloys, the idea for solving the above-mentioned problems is as follows.

(1) The equipment for preheating and pre-reduction is operated in a steady state, and the pre-reduction of Fe0 is carried out as much as possible to lower the FeO content supplied to the smelting reduction furnace. The reason is slag F
This is because eO has a large influence on the corrosion resistance of refractories.

(2) On the other hand, the smelting reduction furnace is operated at a time when the component oxide content is relatively high but the molten slag temperature is low (first stage of smelting reduction), and when the molten slag temperature is higher than that, F' The conflict between preventing damage to refractories and maintaining high productivity is resolved by dividing the process into a period in which the eO content is low (melting reduction second stage). This can be realized by charging the raw material containing oxides into the melting reduction furnace only in the first stage.

(3) Matching of a pre-reduction furnace that is operated continuously in a steady state and a smelting reduction furnace that is operated with patchy elements in an unsteady state for one pre-reduction furnace and two smelting reduction furnaces.
This will be achieved by adopting equipment conditions such as a combination of bases and optimizing the operating pattern.

Hereinafter, the case where ferrochrome is smelted by the smelting reduction method will be explained as an example. The equipment consists of one rotary kiln used for preliminary reduction and two top-bottom blown converter reactors used for melt reduction.

The first reason for combining a pre-reduction furnace is to reduce the heat load required on the smelting-reduction furnace by preheating and pre-reducing the charging material using the high-temperature exhaust gas emitted from the smelting-reduction furnace. It is. For example, 70% of the chromium content in chromium ore
If chromium ore can be charged into the smelting reduction furnace with 90% of the iron content pre-reduced and preheated to 1000°C, the required heat generation in the smelting reduction furnace will be lower than when chromium ore is charged without being pre-reduced. The amount should be approximately 30%. Further, if most of the iron content in the raw material to be charged is pre-reduced, the T and Fa percentages in the generated slag can be lowered, and corrosion of the refractory can be reduced.

FIG. 1 shows an example of equipment for a melting reduction furnace. Melting reduction furnace 2
receives the pre-reduced chromium pellets, melts them and reduces the remaining chromium and iron, and finally produces molten chromium-iron alloy and molten slag mainly composed of gangue. This is a device for obtaining. The reason why the converter was used was to achieve strong stirring of the slag-metal, which is an essential condition for the reaction to proceed in this case (9). A tuyere 3 (there may be more than one) for blowing oxygen-containing gas from the bottom and a lance 4 for blowing oxygen into the furnace from above are attached.

Reference numeral 12 denotes a pellet distribution device located between the rotary kiln 1 and the smelting reduction furnace 2, and used to feed pellets into the semi-reduced chromium supplied from the rotary kiln 1 to any of the predetermined smelting and reduction furnaces.

The operating method is as follows.

In a rotary kiln, chromium ore pellets containing carbon and outer charcoal (e.g. coke lumps) are charged to promote reduction, and the high-temperature exhaust gas from the smelting reduction furnace is used as a heat source to heat 4 pellets to a maximum of 1450°C. Perform solid-phase preliminary reduction.

The smelting reduction furnace performs semi-continuous, semi-batch type operation.

That is, the description will be made from a state in which more than 80% of the slag generated in the previous heat and about 2 A of high chromium molten metal were tapped, and about 173 liters of the rated molten metal remained in the furnace.

In the first stage of melting and reduction, gas containing oxygen (for example, the tuyere is made into a double pipe, and propane gas, Ar, etc. is injected into the molten metal from the bottom blowing tuyeres (10) 3 to protect the siding, such as propane gas or Ar from the outer pipe). chromium pellets, carbonaceous material, and flux (mainly lime) that have been preheated and pre-reduced from the rotary kiln 1 while blowing oxygen from the top-blowing lance 4
is supplied to the melting reduction furnace. The fermentation heat of carbonaceous material (C→CO or Co2), the reduction reaction of carbon (solid carbonaceous material or carbon dissolved in metal) and chromium or iron oxide, and slag formation using gangue and 7 lacs proceed.

A gas containing oxygen is supplied into the molten metal from the bottom blowing tuyere 3 (for example, the tuyere is made of a double pipe, and the outer pipe supplies propane gas, tuyere protective gas such as Ar, and the inner pipe supplies oxygen gas). Infuse. The effects of this bottom blowing gas are: (i) Strongly stirring the metal and the generated slag layer to increase the reduction reaction rate of chromium oxide; (11) Burning the carbon in the metal and heating the metal bath. and then heat the metal to a moderate temperature (20° below the freezing point).
℃ or higher and 100℃ or lower); (ii)
i+ If necessary, in order to obtain carbon-unsaturated product bath water, there are three steps: partial removal of slag and decarburization by blowing acid.

After charging a predetermined amount of semi-reduced chromium 4lets, the smelting reduction shifts to the second stage. In the second period, the semi-reduced chromium pellets are not supplied, and blowing acid and stirring are continued (charcoal material is replenished as necessary).

In the second stage, unlike in the first stage, there is no supply of chromium oxide into the smelting reduction furnace, so the amount of chromium present as oxides in the slag decreases with the processing time. The amount of chromium thi (present as oxide) in the slag is low. This value can be lowered to a range of 0.7 to 0.05%, but in practice it depends on the chromium yield, economic efficiency, purpose of using the generated slag, and the first and second stages as described below. Targets (T, Cr4) are set from various points such as time adjustment.

When the chromium concentration in the slag is reduced to a predetermined value, the furnace is tilted and the slag is discharged. Depending on the shape of the furnace used and the conditions such as the ore and carbonaceous materials used, if it is difficult to operate without intermediate slag, use intermediate slag (i.e., tapping the molten metal once in two or more of the above cycles). become). After the slag is discharged and before the metal is tapped, carbon-unsaturated metal can be obtained by decarburizing the metal mainly using bottom-blown oxygen, if necessary. Next, the produced metal is tapped out, and the operation is repeated while protecting the bottom blowing tuyeres by leaving the metals 30 to 501 in the furnace.

In addition, the period when semi-reduced chromium pellets are supplied to the smelting reduction furnace (the above-mentioned smelting reduction first stage) and the other times (the above-mentioned smelting reduction second stage, decarburization period, slag, tapping, etc.) #7 is made equal, and by shifting the operating cycles of the two smelting and reducing furnaces in operation, the semi-reduced chromium pellets are charged into either of the smelting and reducing furnaces.

In addition, the exhaust gas from the two melting reduction furnaces is combined into one,
Use (for example, for preliminary reduction).

Example Rated amount of molten metal (i.e. amount of molten metal just before tapping) is 50 tons
Two upper-bottom blowing converters are used as reaction vessels (13), and 2A (approximately 33 tons) of ferrochrome produced using semi-reduced chromium pellets as raw material is tapped out, leaving IA for semi-continuous operation. went. At the bottom of the melting reduction furnace, four bottom blowing tuyeres (double pipes with an inner diameter of 20mm) are installed, and the inner pipes flow pure oxygen and the outer pipes flow zolopane as a protective gas. . The top blow lance has a total of 7 nozzles (one hole in the center,
(6 holes around the circumference).

Chromium ore, which is the main raw material for smelting reduction, is made into pellets by extracting the mixed powder together with coke and granulating it, and after drying, it is charged into a rotary kiln, where it is pre-reduced and preheated using the high-temperature gas emitted from the smelting reduction furnace as a heating source. . The 80 pieces of carbon material supplied to the smelting reduction furnace are charged into the rotary kiln as outer coal to improve the reduction rate of the semi-reduced pellets and to preheat the carbon material to be supplied to the smelting reduction furnace. The rotary kiln performs steady operation (kiln rotation speed: 0.4 r, p, m e d, steady continuous discharge). Using a dispensing device, the pellets are
It is supplied to either one of the two melting reduction furnaces.

The semi-reduced chromium pellets (14
) The average components and temperatures are as follows.

T, Cr: 36%, T, Fe: 189J, C
r content reduction rate: 66%, iron content reduction rate: 92chi, MgO:
10%, At203: 10%, 5in2: 9
q6, temperature: 1000tl::.

-First phase of melting and refining- Preheated pre-reduced pellets, carbonaceous materials, and lime are charged into 17 tons of remaining hot water while blowing oxygen-containing gas from the top and bottom.

The acid blowing speed is 14000 Nm3/hr for top blowing and 1 for bottom blowing.
60ONm'/hr x 4. The charging rate of the pre-reduced 4-lets is adjusted so that the temperature of the molten alloy phase is controlled between 1580-1630°C.

64 tons of semi-reduced pellets in 45 minutes, 20 tons of carbon material.

Lime7. Charge Ot. Of the carbon materials to be charged in this period, 80 inches are ordinary lump coke (carbon material C above), and 10 inches are
The above carbon material A was passed through a four-tally kiln, and the remaining carbon material A was passed through a four-tally kiln.
In the case of 0-chi, the above-mentioned carbon material B is directly charged into the melting reduction furnace from the carbon material's arm.

-Second phase of smelting reduction smelting- Stop the supply of semi-reduced pellets and supply carbonaceous material Honno 4
- Inject 100 kg into the melting reduction furnace every 3 minutes. The bottom blown oxygen amount was kept constant, and the top blown acid amount was 8500 Nm3/hr and 4000 Nm3 every 5 minutes.
/hr sQ Nm /hr to proceed with the reduction of Cr in the slag. (Figure 2 shows an example of changes in T and Cr% in slag during melt reduction).

The final slag composition of the melting reduction furnace is Cab: 19%, 5I
O2: 20chi, MgO: 24chi, At203:22
T, T, Cr: 0.6%, T, Fe: 0.7
%Met.

Next, after approximately 90% of the produced slag is removed as slag, the molten metal is decarburized by continuing to blow acid for 20 minutes. The components of the tapped metal are as follows:

Cr:53! %, Fe: 37%, C: 6.5%, S
l: 0.5chi, S: 0.0015%, P: 0.
0035%.

In this way, the first stage of smelting reduction takes 45 minutes, while the second stage takes 15 minutes, the decarburization stage takes 20 minutes, and the slag and hot water taps take 10 minutes.The time required to supply pellets to each smelting reduction furnace is The time during which pellets were not fed was 45 minutes, and the operations of one rotary kiln and two melting reduction furnaces were matched.

Note that the number of melting reduction furnaces (2) mentioned in the present invention refers to those that are in operation. Therefore, if one of the smelting reduction furnaces is undergoing furnace maintenance such as replacing refractories, the combination of 1 rotary kiln, 2 smelting reduction furnaces in operation, and 1 smelting reduction furnace undergoing maintenance Become.

The above was described using ferrochrome as an example, but the preliminary reduction furnace
Other ferrous alloys (hot metal, semi-hot metal, ferromanganese, etc.) that can be melted and reduced using a top-bottom blowing converter type smelting reduction furnace.
The present invention can also be applied to. The present invention can also be applied to cases where a solid phase pre-reduction furnace (eg, shaft type, fluidized bed type) other than a rotary kiln is used.

(Effects of the Invention) As described above, the present invention provides a pre-reduction furnace suitable for steady operation and a top-bottom blown converter melting reduction furnace that can exhibit its advantages in unsteady operation. This method has great economic effects, such as making it possible to use iron-based alloys as intermediate products for manufacturing steel materials at low cost and with desirable composition conditions for subsequent processes (17). .

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing a top-bottom blowing converter type smelting reduction furnace used to carry out the present invention, and Fig. 2 shows an example of changes in T and Cr contents in slag during operation of the smelting reduction furnace. FIG. 1: Rotary kiln 2: Melting reduction furnace 3: Tuyere 4:
Top blowing lance 5: Hood 6: Carbon material, flux E, B μ7
: Molten metal 8 Varnish slag 9 Nichrome pellet 10 : Carbon material 11 : Bubbles 12 : Bullet distribution device. (1g) P Terama (rnjn) Continued from page 1 C Inventor: Riki Saito Kitakyushu City, Nippon Steel Corporation, Industrial Technology Laboratory, 1-1-1 Edamitsu, Hatto-ku Inventor: Noriyuki Inoue, Kitakyushu City 2142-3 Oaza Maeda, Horoka, Hatato-ku Japan Heavy Chemical Industries, Ltd. 2142-3 Oka 2142-3 Japan Heavy Chemical Industries, Ltd., Kyushu Plant, Ru Applicant: Japan Heavy Chemical Industries, Ltd. 8, Nihonbashi Koami-cho, Chuo-ku, Tokyo number 4

Claims (1)

[Claims] Two top-bottom blown converter type reaction vessels and a pre-reduction furnace for preheating and pre-reducing ore containing iron oxide or its molded product using high-temperature exhaust gas from the top-bottom blown converter type reaction vessel. In combination, when manufacturing iron-based alloys, the operation in each of the above-mentioned top-bottom blown converter reactors is divided into two periods: a time when preheated and pre-reduced ore or its molded product is charged, and a time when it is not charged. At the same time, the operation cycle is shifted between each top-bottom blown converter type reaction vessel, and the preheated and pre-reduced ore or its molded product is charged to one of the top-bottom blown converter type reaction vessels. This is a smelting reduction smelting method for iron-based alloys that is characterized by operating in a state of