JPS6169944A - Manufacture by melting and reducing of ferrochrome - Google Patents

Abstract

PURPOSE:To manufacture ferrochrome with high chrome recovery yield and inexpensively by reducing, melting an oxide with chrome ore, coke and oxygen supplied in a reaction vessel and adding Si alloy over a slag and melting. CONSTITUTION:In a melting and reducing furnace 22 provided with a top blown lance 24 and a bottom-blown tuyere 23, a coke 39, chrome are preheated by a rotary kiln 21, or a prereducing pellet 40, lime stone 41 and the like are charged and gasses including oxygen are blown upward and the oxide is reduced and melted to obtain a molten metal 27 of ferrochrome. In the method, Si alloy including 20-75% Si is added from a hopper 26 over a slag 28 and melted. The ferrochrome particles existing in the slag 28 are caught by the melt and precipitated in molten metal 27 to improve the yield of chrome recovery.

Description

Detailed Description of the Invention (Industrial Field of Application) Conventionally, high chromium alloys such as ferrochrome, which were produced using electricity, can be produced inexpensively and with a high chromium recovery yield system using a smelting reduction method using a top-bottom blown converter reactor without using staining force. The present invention relates to a method for producing chromium oxide at a high rate, and in particular to a method for efficiently transferring ferrochrome suspended in slag to a molten metal bath after smelting and reducing chromium oxide.

In this invention, a high chromium alloy refers to an alloy with a Cr content of 17% or more, which is required from the functional standpoint as a chromium source in the production of high chromium steel.

(Prior Art) Conventionally, high chromium alloys, such as ferrochrome containing 50% or more of Cr, have been disclosed in Japanese Patent Application Laid-Open No. 52-138418, for example.
As disclosed in the above publication, chromium ore or its semi-reduced product is heated, melted, and reduced in a low-shaft electric furnace to produce chromium ore.

However, this method has the following problems.

(1) Because expensive electricity is used as reduction energy, manufacturing costs are high, especially in Japan. (2) Cr% in the slag discharged outside the furnace is as high as 2-5%, resulting in chromium loss. big. Furthermore, since the Cr4 content in the slag is high, the range in which the slag can be effectively utilized is limited.

Therefore, we developed the so-called smelting reduction method, which replaces the reduction energy with electricity and cheaper primary energy (particularly the heat of combustion of carbonaceous solids such as coal and coke). If conditions could be found to sufficiently reduce the amount, the advantage would be enormous. To develop such a process, the following problems must be solved:
(1) In the smelting reduction method, heating and leakage of raw materials, energy for reducing oxides, etc. must be supplied by the oxidation heat generated by the carbon material.In that case, the amount of heat generated by the amount of carbon material supplied must be In order to increase the amount, we would like to utilize not only the reaction of c − + co but also the reaction of C − + Co→CO2 as much as possible. In other words, it is necessary to make the atmosphere oxidizing for efficient heat generation, but how can this be achieved while reducing the chromium content in the slag to a sufficiently low level?

(2) In chromium ore, the chromium content forms ship-soluble spinel and the rate of melting and reduction of the chromium content is slow. Moreover, chromium ore is MgO.

Contains large amounts of oxides such as AtO and StO□,
S The amount of slag produced is extremely large. How can we accelerate reactions that are expected to be slow?

(3) The advantage of the conventional low-shaft electric furnace is that the charge blocks the space between the high-temperature area caused by the arc and the furnace wall;
In addition, since there is almost no flow of molten material near the furnace wall, the furnace wall refractories are hardly consumed.

In comparison, in the smelting reduction method, there is less heat concentration, so if strong stirring is performed to promote the reaction or the temperature of the entire reaction group is raised, the load on the refractory increases. How can damage and damage to refractories be prevented?

By the way, the inventors proposed in Japanese Patent Application No. 53-66939 (Japanese Unexamined Patent Publication No. 54-158320) a chromium ore melt reduction process in which electrical energy was replaced with primary energy (coke, etc.) as the reduction energy. did.

This process uses equipment consisting of a combination of a pre-reduction furnace such as a rotary kiln and a top-bottom blown converter reactor to produce high chromium alloys from chromium ore or chromium oxide. A process in which chromium ore or chromium oxide is pre-reduced to obtain a semi-reduced product, and the chromium ore or chromium oxide semi-reduced product, carbonaceous material, slack and oxidizing gas are subjected to a top-bottom blown converter type reaction. The method consists of a step of supplying the chromium ore or chromium oxide to a container and melting and reducing the chromium ore or chromium oxide.

(Problems to be Solved by the Invention) In the above-mentioned smelting reduction process of chromium ore, etc. using a top-bottom blown converter type reaction vessel, the smelting reduction smelting process is preferably divided into two stages.

In the first stage of smelting reduction smelting, chromium raw material.

Carbon material, slack, and oxidizing gas are charged into a top-bottom blowing converter type reaction vessel, and chromium raw material (chromium oxide) is melted and reduced.

In the second stage of smelting reduction smelting (finish reduction stage), the supply of chromium raw material is stopped, top and bottom blown acid is continued, the metal bath temperature is controlled, and the amount of free carbon material as a reducing agent is controlled. Chromium is reduced in the shortest possible time without placing an excessive load on the refractory material, and the chromium content in the slag reaches (reduces) a predetermined chromium content.

In the second stage of smelting reduction smelting (finish reduction stage), the chromium content in the slag in the top-bottom blown converter reactor is replaced by coke (carbonaceous material) suspended in the slag. ), and it is suspended in the slag as fine particles of hexachromium, several micrometers in size.

The technical problem of this invention is how to transfer this to the molten metal bath in the reaction vessel.

(Means for Solving the Problems) The technical problem of the present invention described above is that molten iron, pre-reduced chromium ore granules, and carbonaceous materials are placed in a reaction vessel capable of blowing oxygen-containing gas from the top to the bottom. In order to produce molten refurochrome by supplying oxygen and reducing oxides,
After the reduction has progressed to a state where the oxide content in the slag is 1 or less, St is added from above the St gold alloy slag containing 20 to 75% and melted. The problem is solved by a method for producing ferrochrome by melting and reduction, which is characterized in that fine particles of ferrochrome present in the ferrochrome are captured and precipitated into a metal bath in a reaction vessel.

The present invention will be explained in detail below.

This invention is implemented using, for example, the equipment shown in FIG.

An example of equipment used to carry out the present invention is shown in FIG. In the figure, 21 is a rotary kiln, 22 is a melting reduction furnace, 23 is a tuyere, 24 is a top blowing lance, 25 is a hood, 2
6 is carbon material, flux hot a4-1'l 7 is molten metal,
28 is slag, 29 is chromium pellet, 30 is carbon material, 3
1 is a bubble, 32 is a pellet storage tank, 33 is a scoop feeder for lime, 34 is a scoop feeder for coke, 35
is an air boat, 36 is a raw material chute, 37 is an exhaust fan,
38 is a pellet discharge port and a smelting reduction furnace generated gas path;
9 is coke, 40 is pellets, 41 is limestone, 42 is an air nozzle, 43 is a blower, 44 is a tuyere pressure measuring device, and 45 is an exhaust gas analyzer. This equipment consists of a combination of a rotary kiln 21 and a top-bottom blowing converter type melting reduction furnace 22. First, the rotary kiln 21 is mainly operated using exhaust gas emitted from the smelting reduction furnace as fuel, and heats various raw materials charged into the smelting reduction furnace 22. For example, after pulverizing chromium ore and carbonaceous materials such as coke, the rotary kiln 21 is formed into pellets. Preliminary reduction of some of the iron oxide and chromium oxide is achieved by heating the charcoal-filled chromium pellets to obtain preheated semi-reduced pellets. It is used for preheating, preheating lime used as flux, or roasting limestone. The rotary kiln 21 can also utilize the sensible heat of the high-temperature gas discharged from the melting reduction furnace 22, and can raise the heating temperature compared to other types of preliminary reduction furnaces, and can also reduce chromium oxide, which is difficult to reduce. Since it can advance 50 to 70 inches, it is suitable as a preheating pre-reduction furnace using exhaust gas. By using this, as a result of preheating and preliminary reduction of the raw material, it is possible to reduce the amount of heat generated per production amount required in the melting reduction furnace. For example, the chromium content in chromium ore is 7.
If 0% and 90% of the iron content can be pre-reduced and charged into the smelting reduction furnace together with coke and preheated to 1000℃, the molten This means that the required calorific value in the reduction furnace (this is generated by burning carbonaceous material with oxygen) is only about 30%. In addition, if most of the iron content in the chromium pellets charged into the smelting reduction furnace is pre-reduced, the (T, Fe%) of the slag produced when the pellets are melted in the smelting reduction furnace can be lowered. It also has the effect of reducing erosion. Furthermore, as shown in FIG. 2, the rate constant in the O (zero) order reaction zone of the pellets charged into the melting reduction furnace can be made uniform, which is advantageous in advancing the reduction reaction.

The smelting reduction furnace 22 receives a supply of pre-reduced chromium pellets and carbonaceous materials such as coke, and melts them, while also removing residual chromium and iron. Proceed with the reduction reaction of the oxide, and finally molten chromium-iron alloy and Mg0-810□-CaO-A
t20. This is a device for obtaining slag whose main component is The converter shape is convenient for achieving strong stirring of the slag, which is essential for the progress of the reaction. Attached are a tuyere 23 (there may be a plurality of tuyeres) for blowing in gas containing oxygen from the bottom, and a top blow lance 24 for blowing oxygen into the furnace from above.

The function of the bottom blowing tuyere is to adjust the temperature of the metal by blowing oxygen-containing gas into the metal, and as a result, to achieve strong stirring of the slag through the stirring of the metal. Then, the carbon content of the product is adjusted by decarburizing the metal. If only stirring is required, an inert gas such as Ar or nitrogen can be used, but even in that case, it is more advantageous to use a gas containing oxygen in terms of the gas cost required for stirring and the loss of sensible heat that is carried out of the system. Dechiru. In order to blow gas containing oxygen into metal,
For example, if a double tube tuyere is used, a small amount of hydrocarbon H is released from the outer tube.
Blow a cooling gas such as Ar + N2 to protect against tuyere erosion.

Oxygen supply from the top blowing lance is the main means of controlling the exothermic conditions in the smelting reduction furnace. The nozzle shape is determined by the amount of oxygen to be supplied, the size of the furnace, exhaust gas conditions, etc. Additionally, the distance between the lance tip and the slag surface can be adjusted according to operating conditions.

The shape of the smelting reduction furnace is basically similar to that of a normal converter for steelmaking, but (1) if the amount of slab produced is large depending on the composition of the ore used, (2) If the load on the refractories in the upper part of the furnace is large, by increasing the secondary combustion rate in the furnace, reduce the relative thickness of the slag by making the diameter of the upper part where the slag aggregates small. Countermeasures are being taken, such as installing a water-cooled structure.

The refractory material in the smelting reduction furnace is magnesia carbide in the lower half of the furnace (the part that is almost always used for slag and metal).FF7! l′-optimal. The upper half of the furnace (co
Similarly, magnesia carbon bricks or chromium magnesia bricks are suitable for the parts exposed to the CO2-based high-temperature gas atmosphere. Which is the best?
What value is selected as the CO/CO2 ratio of exhaust gas? (From the operation of the smelting reduction furnace, the CO/CO2 ratio is 0.3
can take any value within the range).

Note that a pellet storage tank is provided between the rotary kill/reduction furnace and the melting reduction furnace as a buffer for matching the two, if necessary. Either the rotary kil/ is operated unsteady according to the raw material supply/4 tar/ required from the melting reduction furnace, or the two melting In the case where the operation cycles of the reduction furnaces are shifted to stabilize the raw material supply and setan as the sum of the two, the storage tank can be made smaller or even removed.

The operating method using the above equipment is as follows.

In the rotary kiln, chromium ore pellets containing carbon and coke lumps are charged, and the heat source is high-temperature gas from the smelting reduction furnace.Heavy oil and other fuels are added as necessary, and air nozzles 42 and air boats are used. Combustion is controlled by supplying air or oxygen-enriched air through the kiln 35, etc., so that the highest temperature region in the kiln is 1400° C. or higher, which is necessary to promote the reduction of chromium.

It is desirable that all the carbonaceous materials required in the smelting reduction furnace be supplied through a rotary kiln, except for some adjustment purposes. This is because increasing the amount of carbon in the kiln prevents re-oxidation of the pellets in the high temperature range, making it possible to maintain a high reduction rate of the chrome pellets supplied to the smelting reduction furnace. This is because the material itself is preheated, which improves the heat 74 lance of the smelting reduction furnace. However, if there is a large amount of carbon material charged into the kiln and it becomes a problem that the 00% of the gas at the kill/outlet cannot be reduced to a sufficiently low value, some of the carbon material may be removed from the middle of the kiln, e.g. It may be fed by a scoop feeder.

As a flux, depending on the composition of the chromium ore and carbon material used, lime, and if necessary, silica stone, or CaO and S
Slag containing O2 (e.g., from the stainless steel manufacturing process) is added to the smelting reduction furnace. These 7 lacs are added in approximately proportion to the amount of chrome pellets added, or in advance in proportion to the amount of chrome pellets, taking into account the time required for slag formation.

These 7 lacs may be directly charged into the smelting reduction furnace from the Hora-G-26, but they can also be preheated through a rotary kiln before being charged. In particular, it is also possible to use limestone as the lime source, roast it in a kiln, and feed the preheated quicklime to the smelter reduction furnace.

However, if there is a risk that the chromium pellets and 7lux will react in the kiln to lower the melting point and cause deposits to form in the kiln, the fluxes should be added near the bottom of the kiln through the scoop feeder 33, or A separate preheating device may be used for preheating or roasting.

Note that rotary kiln operation is difficult when the storage tank is large, or when two smelting reduction furnaces are operated with staggered operation cycles and the sum of the pellet supply amounts to them is almost constant over time. Operate close to steady state. In other cases, the raw material supply and
Unsteady operation will be carried out to match the current situation.

When starting up a smelting reduction furnace, it is charged with iron or iron-chromium molten metal obtained from another melting furnace, or with coke and mold pig iron or solid ferrochrome and blown acid to melt the metal. and use it as a seed bath. From the second heat onwards, for example, the operation is carried out in such a way that more than 80% of the slag generated in the previous heat and about 2/3 of the high chromium molten metal are tapped out, leaving about 1/3 of the rated molten metal amount in the furnace as seed metal. continue.

First phase of smelting and reduction smelting - Oxygen-containing gas is blown into the aforementioned seed water from the bottom blowing tuyere 23 and while stirring, oxygen is top blown from the top blowing lance 24, and preheated and pre-reduced chromium is produced from the rotary kiln 21. Supplying pellets, carbon materials such as coke, and flux. The oxidation exotherm of carbonaceous material (C→CO or CO□) and the reduction reaction of chromium or iron greed by carbon (solid carbonaceous material or carbon dissolved in metal), and the reduction reaction of MgO1SiO□, ht2o, min in chromium pellets. , ash in the carbonaceous material and CaO added as flux (in some cases, 5
(LO2 also) is progressing. As the raw materials are added, the amount of molten slag and molten metal increases. During this time, the raw material co-feed rate, top and bottom blown acid rates, lance height, etc. are controlled so that the metal temperature is higher than the solidification start temperature and lower than 1650°C. The purpose of setting the metal temperature above the solidification start temperature is to prevent clogging of the bottom blowing tuyere, which is important for carrying out the present invention.

In addition, under strong stirring conditions, which is a necessary condition for the present invention, the temperature difference between the metal and slag is small, and the metal temperature is 1650°C.
If managed as follows, corrosion of refractories by slag can be suppressed. The temperature of the metal may be measured with an immersion thermocouple every few minutes, but it can also be estimated to some extent by continuously measuring the pressure inside the bottom blow tuyere pipe. This is based on the phenomenon that when the metal temperature decreases, the amount of deposits on the tuyere tip (solidified metal and chromium-based oxides) increases, and the pressure inside the tuyere pipe increases. The relationship between the pressure inside the tuyere and the metal temperature is almost determined once the tuyere conditions, bottom-blown acid conditions, and metal composition are determined, so if you have determined the relationship between the two in advance, you can then use that relational expression. The metal temperature can be estimated from the measured pressure inside the tuyere.

The total amount of oxygen gas to be supplied to the smelting reduction furnace depends on the components of the various raw materials to be supplied, the temperature conditions, the CO/CO2 ratio of the exhaust gas (this can also be arbitrarily determined if CO/CO2 is 0.3 or more), etc. It is determined based on The average acid blowing rate is determined by dividing the required total amount of oxygen gas by the time of the first stage of smelting reduction smelting. If some of these are excluded because bottom blowing, which will be described later, is performed, the average top blowing acid rate is determined. Exhaust gas CO/CO2
In order to adjust the ratio to a predetermined value, the top blow lance nozzle shape, lance height, etc. may be adjusted.

The bottom blowing gas is important in the present invention as the main stirring power for slag and metal. In order to increase the speed of the oxide reduction reaction, the temperature of the molten metal and slag is made as uniform as possible,
This is to reduce the degree of local high temperatures that cause damage to refractories. The molten metal and slag are stirred by bottom blowing gas by the expansion and rise of the generated gas. The stirring strength is expressed as a hail parameter, S (Nt/m
In, t), the relationship between the meter S and the refractory unit index in the first stage of smelting reduction smelting is shown in Figure 3. If the stirring strength, that is, the value of the parameter S, is too small, the slag temperature will locally increase, which will have an adverse effect on the refractories, and the reduction rate of iron and chromium oxides will be slow. Due to contact, etc., the unit consumption of refractories increases rapidly. On the other hand, if S is too large, the reduction rate will no longer depend on the stirring force and will remain constant, and the damage to large objects will increase due to increased slag stirring, causing the refractory unit consumption to increase again. . Therefore, S needs to be within a range that satisfies the following conditions.

100 (Nt/min, t)≦S≦2500 (NL
/min, t) (2) - Second phase of smelting reduction smelting - When the supply of raw materials containing a predetermined amount of chromium oxide (semi-reduced chromium pellets) is finished, the chromium content in the slag is reduced to a predetermined value. The process will move on to the second stage of smelting reduction smelting for the purpose of finishing reduction.

At this stage, the supply of pellets should be stopped, the top and bottom blown acid should be continued, the temperature should be controlled, and the amount of free carbon material as a reducing agent should be controlled to avoid placing an excessive load on the refractories. The challenge is to proceed with the reduction of chromium in a short period of time and reduce the chromium content in the slag to a predetermined level.

First, the metal temperature is controlled to be above the solidification start temperature and below 1650°C, and the reason is the same as in the first stage of smelting reduction smelting. 8 degrees is controlled by the top blown acid conditions (blowing rate, lancehide, etc.).

Strong stirring of the slab by bottom blowing gas is as important as in the first stage of smelting reduction smelting. A relationship almost similar to that shown in FIG. 3 also holds true for the second stage of smelting reduction smelting. Furthermore, the amount of metal particles in the slag at the end of the second stage of smelting reduction smelting is related to the amount of blown gas, as shown in FIG. this is,
If the stirring is too weak, there is little opportunity for the fine metal particles (several microns in diameter) generated from the ROMS spinel to coalesce, so they will not settle easily.On the other hand, if the stirring is too strong, the metal in the bath will be blown up into the slag. This is to increase the number of metal grains again. Such metal grains in the slag cannot be completely separated by settling before pouring, and in order to recover them, the slag must be crushed after solidification, magnetic separation, and other treatments are required.

From the relationships in Figures 3 and 4, ・9 rammeter; S is 100 (NA/ml n-t)≦S≦1800 (N
t/m1n-t) The relationship (3) must be satisfied.

Furthermore, the reduction reaction rate during this period depends on the amount of free carbon material, based on basic experimental results. In reality, the carbon content supplied to the smelting reduction furnace consists of two types: one that was contained in the pellets as internal charcoal, and the other that was added as a carbon material separately from the pellets.
There are seeds. The amount of the former is approximately equal to the amount melted into the reduced metal. Therefore, approximately, the amount of free carbon material is calculated from the carbon content in the carbon material supplied to the melting reduction furnace.
The carbon content is removed by subtracting the carbon content that has become O or CO2 gas and has escaped to the outside of the furnace. The latter can be calculated from the amount of blown acid and the CO and CO2 analysis values of exhaust gas.

Actually, when the amount of free carbon material is defined by equation (4) and the relationship with (T, Cr%) of the slag after each time is shown, the relationship is shown in FIG. It can be seen that in order to obtain a sufficiently low chromium content in the slag, it is desirable that the amount of free carbon material satisfies the condition of equation (5).

That is, since the free carbonaceous material is reduced by blowing acid, if necessary, for example, carbonaceous material hollow 4'
-26 supplies carbonaceous material to the melting reduction furnace.

In order to control the reduction reaction rate (that is, the rate of decrease of T and Cr in the slag) during this period, the slag components and (At20
3%)≦22chi The condition (6) must be satisfied. In order to satisfy this component condition through the second stage of smelting reduction smelting, the flux in the first stage of smelting reduction smelting must be adjusted so that the slag composition satisfies this component condition at the latest at the end of the first stage of smelting reduction smelting. The amount added must be adjusted.

When the above conditions are satisfied, the chromium content in the slag can be reduced to a predetermined value by continuing the treatment for the necessary time. For example, slag T, Cr
It is also possible to reduce it to t-0.5% or less.

When the chromium content in the slag can be reduced to a predetermined value, it is discharged. Furthermore, metal hot water is also available. At that time, the amount of metal generated is left as a seed water for the next heat. Incidentally, after the slag is drawn, the metal discharge operation may be omitted, and the first and second stages of the smelting reduction smelting process may be repeated again to discharge the produced metal for two slags.

The discharged metal can usually be solidified and then crushed to produce a finished product, as in the case of 7erochromium, but it is also possible to transport the molten metal to a steelmaking factory and use sensible heat to reduce stainless steelmaking costs. The discharged slag is either allowed to solidify naturally or is rapidly cooled by water pulverization, and if necessary, it is crushed and magnetically separated to recover metal particles and then used for various purposes such as landfill material, roadbed material, and soil improvement. Can be covered with drugs etc.

In the process described above, the inventors researched a means to transfer the ferrochrome fine particles suspended in the slab to the metal bath after the second stage of smelting reduction smelting (finish reduction smelting), and as a result, they found that si 81 alloy, such as ferrosilicon, containing in the range of 20 to 75% by weight, is added onto the molten slag in the reaction vessel, melted, and the ferrochrome floating in the slag is captured by this melt, and it settles into the metal bath. It has been found that metal fine particles in the slag can be transferred into the metal bath with extremely high efficiency.

In the present invention, the Si content of the St alloy added from above the molten slab is set to be in the range of 20 to 75%.In this range, the melting point must be 1300C or less, and in the process of the present invention, the Si content can be easily melted. This is because the metal particles can settle in the molten slag, trapping fine metal particles in the process and transferring them into the metal bath.

When the St alloy is added and melted from above the molten slag, the degree of reduction of chromium oxide in the top-bottom blowing converter type reaction vessel is as follows: The oxide content therein is 1 or less, preferably 0.
From the viewpoint of increasing the chromium oxide content by allowing the reduction of oxides in the slab to proceed until it becomes 5% or less,
is necessary.

(Example) The rated molten metal ffi amount (i.e. the molten metal amount immediately before tapping) is 5
Two 0-ton top-bottom blowing converters were used as reaction vessels, and semi-reduced chromium pellets were used as raw materials. Two-thirds (approximately 33 tons) of the produced ferrochrome was tapped out, and the remaining two were operated semi-continuously. Ta. Four bottom blowing tuyeres (double tubes with an inner diameter of 20 mm) are installed at the bottom of the melting reduction furnace.The inner tube uses pure oxygen and the outer tube uses professional gas as a protective gas. Flow. The top blowing lance has a total of 7 nozzles (1 hole in the center and 6 holes around the periphery).

Chromium ore, which is the main raw material for smelting and reduction, is extracted from a mixed powder frame and granulated together with coke to be left. 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 and reduction furnace as a heating source. Ta. 80% of the carbon material supplied to the smelting reduction furnace is charged into the rotary kiln as outer coal to improve the reduction rate of the semi-reduced pellets and to preheat the carbon material supplied to the smelting reduction furnace. The rotary kiln operates normally. (kiln rotation speed 0.4 r, plm-1 < let steady continuous discharge). The pellets are fed to either of the two smelting reduction furnaces using a distribution device.

The average composition and temperature of the semi-reduced chromium pellets supplied to the smelting reduction furnace are as follows.

T, Cr: 35%, T, Fe: 23%, Cr content reduction rate = 66%, iron content reduction rate: 92%, MgO: 10%
, At20. : 10%.

5in2: 9 inches, temperature: 1300℃.

- First phase of smelting reduction smelting - While blowing oxygen-containing gas from the top to bottom of the remaining 17 tons of hot water, preheated red to be reduced, carbonaceous material, and stone fire are charged.

Blowing speed v is top blowing 1400ONm3/hr, bottom blowing 16
o.

Nm 3/hr x 4. The charging rate of the prereduced pellets is adjusted so that the temperature of the molten alloy phase is controlled between 1580 and 1630°C.

64 tons of semi-reduced pellets, 20 tons of carbonaceous material, and 7.0 tons of coal in 45 minutes.
Charge O5. The parameter of the carbon material to be charged in this period: S is in the range of 500 to 700, and the formula (2)
During the period when the following conditions were satisfied, the secondary combustion rate was maintained at 40 by controlling the blowing acid circuit.The slag components, amount, and temperature at the end of this period were as follows.

CaO: 25%, SlO□: 26%, MgO: 19
%, At203: 19%, T, Cr: 6.8
%, T, Fe: 1.1%, slag amount: 36t, @ degree: 1
630℃.

The amount of metal is 45t1 and the amount of free carbon material is 3t.

2nd phase of smelting reduction smelting - Stop the supply of semi-reduced pellets, and feed 1001 # of carbonaceous materials into the smelting reduction furnace every 3 minutes. The amount of oxygen blown from the bottom was kept constant, and the amount of top blown acid was changed to 8500 Nm'/hr and 400 ONm'/h every 5 minutes.
r, ONm'/h r, Cr in the slag
Proceed with the refund of the amount. Metal temperature is 1600-1630℃
maintained within the range.・Mother meter: S is 1200-15
00 and satisfies the condition of formula (3).

Amount of free carbon material/amount of molten slag = 60 to 1.0 OK! i'
/l satisfies the condition of formula (5).

The final slag composition of the smelting reduction furnace is Cab: 28%, st
o□: 28%, MgO: 20chi, At203: 20%
, T, Cr: 0.6%, T, Fe: 0.7%.

The slag throughout this period was (Sio2%) +1. t s (%Az2o,)At2
0. = 18 to 20%, satisfying the condition of formula (6). During this time, the secondary combustion rate was maintained at 40 inches.

When the second phase of smelting reduction smelting progresses and the chromium content in the slag reaches 0.5%, the top and bottom blowing acid is stopped, and ferrosilicon is added to 500 and 51 from above the molten slag, and the slag is melted. The ferrochrome fine particles floating in the slag were captured and transferred to the metal bath.

The components of the tapped metal are as follows:

Cr: 53%, Fe: 37%, C: 6.5%,
St: 1.0%, S: 0.015chi, P: 0.035
%.

In this way, the first stage of smelting reduction smelting takes 45 minutes, while the second stage of smelting reduction smelting takes 15 minutes, the decarburization stage takes 20 minutes, and the slag and output @1
The time for feeding pellets to each smelting reduction furnace is 45 minutes, and the time for not feeding pellets is 45 minutes, and the operation of one rotary kiln and two smelting reduction furnaces is 0 minutes. They are matching.

(Effects of the Invention) As described above, the present invention enables the production of ferrochrome, which has conventionally been carried out using expensive electric power as energy.
Using a smelting reduction method that uses inexpensive carbonaceous material and oxygen as a heat source, the chromium recovery yield can be higher than that of the conventional electric furnace method, making it possible to supply ferrochrome that is cheaper than the conventional method. This has great industrial effects.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of an apparatus for carrying out this invention, and FIG.
A diagram showing the relationship between kl and ° temperature, Figure 3 shows the effect on the refractory corrosion index. - Main meter 5 (S = bottom blowing gas amount / (molten metal amount + molten slag amount) NA / m1n-t) Figure 4 shows the effect of
Fig. 5 is a diagram showing the influence of (free carbon content)/(molten slag Jl) on the reduction process of chromium in slag in the second stage of smelting reduction smelting. The amount of carbon material is calculated from the carbon content in the carbon material charged into the smelting reduction furnace.
o or CO2ff (defined as the next order of carbon content). Procedural amendment band (voluntary) December 20, 1980 Manabu Shiga, Commissioner of the Patent Office1, Indication of the case Patent Application No. 190637 of 19822, Name of the invention Process for manufacturing ferrochrome by melting reduction3, Amendments to be made Relationship with the case Patent applicant: Nippon Steel Corporation, 2-6-3 Otemachi, Chiyoda-ku, Tokyo (665), and one other representative: Takeshi
1) Yutaka 4, Agent 2-4-1-6 Marunouchi, Chiyoda-ku, Tokyo 100, Detailed description of the invention of the specification subject to amendment and drawings (1) Specification 9
Page 5-6 lines "70 units for chrome" are corrected to "50 units for chrome." (2) ``co7co2≧0.3'' on page 12, line 7, is l'-
Co/CO2≧0.1”. (3) Page 17, line 13 r Co/CO2 0.3 or more.”
is corrected to "CO/CO2 is 0.1 or more." (4) The fourth line from the bottom of page 21, "Relationship with (T, Cr%) of slag" is corrected to "Relationship with the amount of chromium present as oxide in slag." (7) Page 22, line 3 r Cr: Free carbon content -”
Corrected to f2 free carbon material weight. (8) On page 22, lines 3 to 2 from the bottom, change “and must” to “and (Atzes)≦O,08T-1
It is desirable to satisfy the conditions of 05(6). ”. (9) On page 23, line 8, "T and Cr in the slag" is corrected to "the amount of chromium present as an oxide in the slag." (G) Lines 5 to 8 of page 25, “Melted slag... is necessary” is changed to “reduction until the amount of chromium present as an oxide in the molten slag is 1aIb or less, preferably 0.5T or less.” It is necessary to allow the Si-containing alloy to proceed from the viewpoint of effectively using the Si-containing alloy for the purpose of the present invention.'' (b) Correct Figure 5 on a separate sheet. Fig. 5 Zego bird meeting material quantity/slak quantity (kg/l) procedural amendment form
(Spontaneous) September 21, 1985 Patent Application No. 190637 of 1988 2, Name of the invention 7 Manufacturing method by smelting reduction of erotic chrome 3, Person making the amendment 5, Date of amendment order 1979 Month, day (1) The scope of claims is amended as shown in the attached sheet. (The third line from the bottom of page 6 of the 27 Specification, “molten iron,” is amended to “chromium ore.” Claims: 7. Chromium melting in a reaction vessel capable of blowing oxygen-containing gas from the top and bottom;
In producing erochrome, after the reduction has progressed to a slag state, the St gold alloy slag containing Si in the range of 20 to 75% is added and melted, and this melt reduces the ferrochrome fine particles present in the slag. capture,
1. A method for producing ferrochrome by melt reduction, characterized by precipitation in a metal bath in a reaction vessel.

Claims (1)

[Claims] In order to produce ferrochrome by supplying molten iron, pre-reduced chromium ore granules, carbonaceous materials, and oxygen to a reaction vessel that can blow oxygen-containing gas from the top to the bottom, the oxides are reduced and melted. After the reduction has progressed to a state where the oxide content is 1% or less, a Si alloy containing Si in the range of 20 to 75% is added from above the slag and melted, and the molten material is added to the slag. A method for producing ferrochrome by melt reduction, characterized by capturing fine particles of ferrochrome and allowing them to settle in a metal bath in a reaction vessel.