JPS6021218B2 - Ferrochrome manufacturing method - Google Patents

Description

Detailed Description of the Invention The present invention relates to a method for producing ferrochrome in a blast furnace, and more specifically, a method for producing ferrochrome with a chromium content of 40% or more, preferably 50% or more, which has a particularly high product value. It is related to.

Generally, ferrochrome is manufactured by charging chromium ore, coke reducing agent, building materials such as lime into an electric furnace, and smelting it.

This manufacturing method not only requires a large investment in manufacturing equipment, but its biggest drawback is that it requires the use of expensive electrical energy. Recently, a technology that replaces a portion of this electrical energy with inexpensive heavy oil or the like, that is, a technology that partially reduces chromium ore in a rotary kiln or the like and finally reduces it in an electric furnace, has been commercialized.

However, this technology adds a new process called a rotary kiln, which increases the cost of equipment and repair costs when including the auxiliary equipment.

Moreover, expensive electrical energy cannot be completely reduced; just under 50% is required. In addition, the operation rate decreases due to the increase in this process. In the past, research was conducted on the technology to produce ferrochrome in a blast furnace, but since chromium oxide is extremely difficult to produce and chromium ore is elutritic, it has not been decided to produce ferrochrome industrially in a blast furnace. has not been successful.

In particular, it has been difficult to manufacture ferrochrome with a high chromium content, such as 40% or more, in a blast furnace. The reason why it is easy to use an open furnace to smelt iron ore in a blast furnace is that the iron ore's carbon dioxide and carbon dioxide gases occur in the Okada area, and the melting of the reduced iron ore is also easy. be.

Therefore, the descent of the bags as they melt in the furnace and the reduction of the iron ore occur smoothly. As a result of much research into the behavior of chromium ore, the present inventor found that ferrochrome with a high chromium content, for example 40% or more Cr, and even 50% Cr.
The present invention was completed by discovering production conditions that allow ferrochrome containing the above to be industrially produced in a blast furnace.

Chromium ore is mainly C03, Fe0. Aso203
, Mg0, and Si02, and its melting point is extremely high, making it difficult to melt chromium ore using normal blast furnace operating methods. According to research conducted by the present inventors, it has been found that in order to melt and drip chromium ore in a blast furnace, it is necessary to lower the Cr203 concentration in the ore to a certain value or less3. Cr203
If the concentration is not reduced in this manner, even if the temperature inside the furnace is sufficiently high and the ore is softened or partially softened, the viscosity will be so high that the raw ore will not actually flow into the lower part of the blast furnace. Cr in chromium ore
2Q indirect reduction hardly occurs in the temperature range where the ore exists in solid form, so in normal blast furnace operation, a large amount of coke is charged and the ore is melted to make the reduction reaction proceed. It is necessary to bring the ore into contact with Cr203 to reduce the Cr203 concentration in the ore through solid-solid and solid-liquid reactions. However, even if the ore is melted, the high Cr2Q concentration in the charged 4 raw materials makes it difficult for the raw materials to fall smoothly into the furnace**, so the reaction progresses slowly, and if this happens, the Cr03 concentration remains high and falls. This hinders shelf hanging and proper coke supply, leading to a lack of heat supply. This vicious cycle occurs when chromium lump ore is put into a blast furnace with coke. For the above reasons, the present inventor has discovered that it is essential to increase the degree of reduction of chromium ore in the upper part of the lumpy zone and the softened zone in order to successfully produce ferrochrome in a blast furnace.

From this point of view, if you just charge lump ore into a blast furnace with coke, Cr203 will not be reduced, so the ore will melt and drip, and the raw material including ore will not enter the high temperature area at the bottom of the blast furnace, and eventually It can be agreed that smelting in a blast furnace is difficult unless a sufficient amount of iron source is added to the raw material to lower the melting point of the raw material. Such difficulties arise in high Cr-containing ferrite. Needless to say, the more you try to get chromium, the bigger it will become. The feature of the chromium ore reduction process according to the present invention is that in the upper part of the lumpy zone and softened zone of the ore in the blast furnace, part of the chromium oxide in the ore is reduced and produced as chromiumbide combined with carbon, and this is melted and dripped. , the degree of reduction in the softening zone is increased so that the concentration of chromium oxide in the remaining ore is below a value that allows melting and dripping of the ore.

For this purpose, the present invention employs the following means '1 stitch' 3}.

(m) A specific amount of carbon reducing agent is incorporated into the chromium briquette to allow a considerable degree of reaction to proceed within the chrome briquette.

The extent of the reaction is sufficient so that the unreduced ore remaining in the softened zone can also be melted and dripped. ■ The theoretical combustion temperature at the tuyere tip (tuyere tip temperature) is 2000 to 2600℃.
Make it.

The tuyere tip temperature is determined by the child heat temperature of the air, the oxygen enrichment rate if the air is enriched with oxygen, and the moisture content of the air. The tuyere tip temperature defines the maximum temperature in the high temperature region.
The temperature at the tuyere tip is the RAMM formula: TgaS=36.70Tb
last {0.3605 10.595W + 0.0 Matsu&Q
)} -1728W + Shigeru 97 no 2) 0. Spot 60.01
902) 100.716W However, Tblast is the hot air temperature (
°C) W is moisture (kg) per 1 liter of air. (Q) is calculated by the volume ratio of oxygen to air.

The tuyere tip temperature is the heat source for the area where the reduction of chromium oxide is completed and finally produces molten slag and high-melting-point ferrochrome molten metal, and it requires a high temperature, but it cannot be heated too high. This may cause various troubles. According to experimental results by the present inventors, the desirable tuyere tip temperature is in the range of about 2000 to 2600°C. If it is less than 200 p0, the above-mentioned amount of heat and fluidity of the molten metal will not be sufficient.

Moreover, when it exceeds 2600q0, Si vapor generation increases, and this oxidizes on the surface of the lump coke, becomes silica, and adheres to the coke, and the surfaces of the lump coke are fused together, causing a so-called shelving phenomenon. Furthermore, troubles occur in the operation of the blast furnace, such as erosion of the refractory lining material inside the blast furnace. As described above, the tuyere tip temperature is determined by the three variables Tblast, W, and (02), and these may be appropriately selected to maintain a predetermined temperature range. In a practically preferable range, air having a blowing temperature (Thlast) of 200 to 120020 is used. When enriching air with oxygen, the oxygen content is preferably 41% by volume or less. In this case, the humidity is 3 to 50 m/s. {3' Set the hot air flow rate to 3 to 30 w/min·re per cross-sectional area inside the tuyere level furnace.

In the reduction of chromium ore, almost no indirect reduction occurs, so although the amount of air blown is related to the atmosphere in the furnace, it has little significance in increasing or decreasing the amount of reducing gas.

The purpose of the present invention is to adjust the temperature inside the furnace so that the reduction of the chromium ore can proceed sufficiently at the softening zone. If the air flow rate is less than 3 mm/min., the desired temperature distribution within the furnace cannot be obtained. Moreover, if the speed exceeds 30 m/min, flattening of the raw material pellets will occur and good operation will not be possible. According to the present invention, the reaction in the softening zone proceeds by the means of [1'-3'] above, and the reduction of unreduced Cr203, etc. in the softening zone is completed in the melt dripping zone and the sump section, which will be described later, to convert chromium. This made it possible to produce ferrochrome with high yield and high chromium content.

Next, the present inventor has determined that the diameter of the hearth (inner diameter of the hearth bottom) is 100 m, the height from the tuyere to the furnace head is 400 m, We will explain the condition inside the furnace where the condition of the contents was investigated and the temperature distribution inside the furnace.

Figure 1 shows the temperature distribution inside the furnace. In FIG. 1, the outline of the blast furnace is shown in a reduced size, and the points circled within this outline are the sampling positions taken to estimate the temperature, and the estimated temperature value is written next to this.

Temperature was estimated by measuring the degree of graphitization of coke.
Judging from the situation inside the furnace, the inside of the furnace can be divided into the following four zones descending from the furnace section. [1' Block zone The upper part of the blast furnace, indicated by A in the diagram, is a block zone,
Here, some of the Fe○ is indirectly reduced, but the briquette remains as it was before it was entered.

The temperature of the massive zone is below 1650 qo. '21 Softening zone (represented by B in the figure) The temperature of this softening zone is 17
Since the temperature is from 00 to 1800 o'clock, softening of the briquette occurs, but the temperature is not such a high temperature as to cause melting and dripping if the Cr203 concentration in the briquette is high.

On the other hand, since the temperature of the softening zone is higher than the melting point of chromium carbide, the reduced chromium melts and drips. As a result of demolition, no reduced chromium carbide was found in the softened zone, and some unreduced briquettes and slag remained. It is easily inferred that if the operation continues further, the reduction of this briquette will progress and it will melt and drip. '3} Dripping zone (represented by C in the figure) The dripping zone is the highest temperature zone in the furnace, and is 190
The temperature is between 0 and 2200 o'clock.

The drip zone was made up mostly of lump coke.

This is because the metal and slag melted and dripped between the lump coke, and all of them had flowed down from the dripping zone between the time the blast furnace was shut down and the time it was dismantled. [
4} Reservoir section (represented by D in the figure) The moat section is the section below the tuyere where the molten material accumulates, and its temperature is slightly lower than that of the dripping zone, at 1800 to 2100°C.

Some coke lumps remained in the pool, and the hot water consisted of ferrochrome metal and slag containing less than 5% OCr203.

Therefore, most of the unreduced chromium oxide in the slag sent from the softening zone is reduced by the coke in the dripping zone, and the small amount of chromium oxide that remains is further reduced by the residual coke in the sump, and finally Oxidized chlorine in slag. It is thought that the amount of water is extremely small. What can be seen from the condition of the charge in the furnace as described above is that reduction in the briquette progresses to a considerable extent up to the upper part of the softening zone, and by melting and dripping, the viscosity of the slag containing the remaining unreduced Cr203 is reduced. It is necessary to pass these materials through the drip zone to ensure continuous flow of the materials.

The proportion of chromium oxide in the softening zone must be sufficiently reduced to enable such continuous operation. The degree of reduction of chromium in the softening zone needs to be 80% or more based on the weight of chromium oxide in the ore.
Next, conditions other than the above-mentioned '1 stitch {3} for realizing the reduction reaction process of chromium ore in the blast furnace as described above will be explained.

Chrome ore is produced in lump or powder form, but in the former case, the lump ore is turned into powder and then briquettes are made.

Chromium ore is Cr, which is usually used in smelting in electric furnaces, etc.
/Fe=1.5 to 3.5 is used, but in order to increase the Cr content in ferrochrome, the Cr/Fe ratio is not limited to this range, and a higher Cr/Fe ratio can be used. A typical example of chromium ore has the following composition in weight percent: Cr203Fe〇A〆203Mg〇Si〇2Ca
〇44.618.813.09.77.30ace.

The particle size of the chromium ore powder is preferably pongee grains of 45 mesh or less, preferably 150 mesh or less, in order to facilitate dripping in the softened zone.

The carbonaceous powder used in the present invention is a well-known powder of carbon-containing substances such as coal coke, petroleum coke, and calcined anthracite.

Pongee grains with a particle size of 45 mesh or less are suitable for the carbonaceous powder, and 1
Vertical grains of 50 mesh or less are desirable. Thoroughly mix the chromium ore powder and the carbonaceous material powder.

Of course, the chromium ore lump and the carbon material lump may be mixed and then crushed. The ratio of carbon to chromium ore affects both the strength of the briquette and the ease with which the briquette undergoes reduction reactions in the blast furnace.

In order to determine the carbon proportion from the viewpoint of ease of reduction reaction of briquette, it is necessary to study the reaction formula of carbon in chromium ore.

There are various forms of this reaction formula, but here we assume the following reaction formula, which is considered to be the most main reaction among them, and use it as the standard for calculating the theoretical carbon content. 7Cr203 127C → 2Cr7C3
121C0... 27 moles of carbon according to the '1''1' formula are required per 14 moles of Cr, and 27/14 moles of carbon are required per mole of Cr.

In terms of weight, it corresponds to about 0.45k9 of carbon per Crlk9. Fe○ (Fe203) in chromium ore
Since Cr203 is indirectly reduced, there is no need to mix solid carbon, but it is necessary to reduce 80% of Cr203 before the softening zone, and the amount of carbon is 0.8 times the theoretical amount in equation {1). This is the lower limit.

In addition, in the present invention, in order to inject the carbon-containing briquette into the blast furnace without strengthening the briquette by heating, the maximum amount of carbon is determined without considering the loss of carbon due to heating. It's fine.

The maximum amount of carbon in the briquette varies depending on the size of the blast furnace, but is generally 1.4 times, preferably 1.2 times, the theoretical amount of the formula {1}. If the maximum carbon content is exceeded, the strength of the briquette decreases and it becomes powder, causing problems with the blast furnace such as hanging on shelves. In other words, if the amount of carbon is limited to below the above-mentioned ratio, the blast furnace can be operated without trouble even if the briquette contains carbon. The lack of reduced carbon is compensated by coke which is simultaneously supplied to the blast furnace. When coal coke or the like is used as the carbon powder, the m-type carbon is of course a fixed carbon component. To make briquette from mixed powder, inorganic binders such as bentonite, water glass and cement,
Or starch, CMC (carboxymethyl cellulose)
and an organic binder such as PVA, alone or in combination with an inorganic or organic substance, and the mixture is granulated using a bread pelletizer or the like, or made into a lump using a briquette machine, an extruder, or the like. The shape of the briquette is not particularly limited to a spherical shape. The size of the briquette varies depending on the inner diameter of the furnace, but 10 to 5 briquettes is appropriate in order to facilitate melt dripping in the softening zone.

Within this range, in order to improve the air permeability between the packed briquette grains, it is preferable that the briquettes are uniform in size to avoid dense packing. The green briquette obtained by granulation etc. is then dried or cured (in the case of cement). This drying process may be performed in the raw material preheating chamber at the top of the blast furnace, but depending on the strength, briquette, or type of binder, a separate drying process may be provided and the drying process may be carried out in advance. is desirable. In that case, the drying temperature is a temperature at which the carbon powder is not substantially combusted, for example, about 500° C. or less. There is a known drying device such as a grate kiln. It is desirable that the lump coke that is charged into the blast furnace together with the briquettes be of high strength, as in the case of pig iron smelting, but unlike in the case of pig iron, indirect reduction is extremely low, so there is no need to increase the height of the blast furnace. Therefore, strength is not required as strictly as in the case of pig iron.

The size of the lump coke is not particularly limited and varies depending on the size of the blast furnace, but generally 30 to 100 mm is appropriate. It is desirable that the particle size varies as much as possible within that range. The amount of lump coke is also related to the amount of carbon in the briquette, but approximately 150 to 500 k9 per ton of briquette is appropriate. When the amount of lump coke is less than 150 k9, the heat source is insufficient, the vertical position of the softening zone in the blast furnace is lowered, and the reduction of chromium ore does not proceed, making it impossible to realize the reduction process of the present invention. The toning agent is mainly lime (quicklime or limestone), and silica stone may be added in some cases.

In this case, alkali metal and alkali metal fluorophores, which are generally used to increase the fluidity of slag in electric furnace smelting of ferrochrome, and to promote solid-state reduction in preliminary reduction in rotary kilns, are also used. It is also possible to include additives such as compounds and carbonates in the forming agent. Furthermore, it is of course possible to include lime, silica stone, and additives in the aforementioned briquette. Therefore, the ripple-forming agent may be charged separately from the briquette, or may be included in the briquette and included in the briquette, or a combination of these charging methods may be used. In electric furnace smelting, the composition of the slag-forming agent is quite strictly limited because it is also related to the gas resistance, but in the method of the present invention, it can be determined by taking into account the viscosity and melting point of the slag to be produced. Ca○/Si02 (hereinafter referred to as C/S) of the generated slag is 0.4 to 1.3:A2030M or /Ca0
It is preferable to set 10Si020Mg01A203 (hereinafter referred to as AMF) to be 0.4 to 0.8. The reason for this is that if the AM circle is less than 0.4, the capacity of the slag will increase, which will lead to an increase in the sensible heat produced by the slag, and will also be negative in terms of contact between the active ingredients (carbon, chromium oxide, iron oxide). The reaction in and below the softening zone becomes insufficient. If the AMF is higher than 0.8, the melting point of the slag will become high, which is not favorable for melting, and the fluidity of the molten metal will deteriorate, causing problems in the separation of metal and slag. C/S is selected so as to provide a slag with a low melting point and low viscosity, but is generally preferably in the range of 0.4 to 1.3.

Mn0, which is known as a component that reduces the viscosity of slag during the production of ferrochrome, does not need to be used in the present invention.

The slag in the softened zone is Aso203, Mg○, Si02
It is conceivable that Ca○ dissolves Cr203, which is the main component in the briquette, into the slag. Therefore, the viscosity of slag is
C03 decomposes to become Ca0), and is affected by oxides of Mg○, A〆203, Si02, and Cr203 (unreacted) generated from briquettes. In order for the slag to have a viscosity low enough to melt and drip in the softening zone, reduction of chromium oxide in the softening zone should proceed sufficiently so that the following condition is satisfied. Cr203(
%) AZ203 (%) 10Mgq%) + sio2 (%) 10cao (%) ≦0.05 Incidentally, the preferred slag composition range is A〆203: 26-29 Mg○: 21-24, S
i02:27-37, Ca○:15-30, Cr203
: 3 to 4, Fe○: 1 to 1.5 (all weight %).

As mentioned earlier, hot air affects the amount of heat required for melting the bags and the reactions between the components of the charge, so in order to increase the productivity of the blast furnace, the amount of hot air (heat amount) must be increased. Must be. This increases the gas flow rate.
When the gas flow rate becomes extremely high, well-known phenomena such as flooding occur. If the gas flow rate is high enough to avoid such inconvenient phenomena, indirect reduction by gas will occur to a considerable extent in the reduction of iron ore, and the reduction reaction rate will increase with the gas flow rate, increasing productivity. Since the reduction of chromium ore mainly involves direct reduction, the reduction reaction rate does not increase, and only accelerates dissolution. Therefore, in order to increase the productivity of chromium ore, it is not effective to increase the amount of hot air beyond the required amount of heat to be supplied. Furthermore, CO gas is generated by direct reduction of chromium ore, and this invention gas increases the total gas amount by about 20%, and furthermore, the gas generated by reduction is heated by the combustion heat of coke and expands. In this way, in the reduction of chrome ore, an increase in the gas flow rate and an increase in the gas volume occur in the furnace, similar to increasing the amount of hot air, so increasing the amount (volume) of hot air is not necessary as described above. This may lead to inconvenient phenomena. For the reasons mentioned above, in order to increase the amount of heat transferred to the metal in the furnace, instead of increasing the amount of hot air, measure at a high pressure, preferably at the top pressure of the furnace. 3. Operations should be carried out with no more than 9/enemies.

That is, from the viewpoint of air blowing, it can be said that the characteristics of the present invention are that the blowing amount (capacity) is reduced to send high-pressure gas, and as described above, the theoretical combustion temperature at the tuyere tip is increased. Such air blowing characteristics are due to the high chromium content (40
%Cr or more, and 50%Cr or more) is considered to be important for producing ferrochrome in a blast furnace. The use of high pressure increases the pressure difference between the tuyere and the top of the furnace, making it easier for the furnace gas to pass through the filled bags, making it possible to use small-sized briquettes. In other words, even if a part of the briquette is pulverized, the blast furnace can be operated. As already mentioned, the characteristics of the situation inside the blast furnace according to the method of the present invention are that indirect reduction of chromium oxide hardly occurs, and direct reduction occurs only when the bagged material has descended to near the softening zone. .

This feature is in contrast to the case of iron ore, where indirect reduction is highly advanced and melt dripping starts relatively high in the furnace, whereas in the case of ferrochrome, dripping starts relatively low in the furnace. are doing. Therefore, the briquette must descend through the furnace over a relatively long distance while being exposed to the risk of being pulverized, and it is better for the briquette to be fine in terms of melting.
The significance of adopting high-pressure operation in ferrochrome production is significant.
Furthermore, the dripping of chromium ore in the softening zone occurs rapidly, and the more you try to increase the dripping amount, the worse the ventilation inside the furnace will be due to the molten material.
High pressure operation is very important for the production of r-containing ferrochrome. Hereinafter, the main parts of the equipment used in the present invention will be explained in detail based on the drawings.

FIG. 2 is a diagram showing an embodiment of a blast furnace and its ancillary equipment for carrying out the present invention.

The blast furnace 18 has an internal reaction space 19 formed by the furnace bottom 1 and side walls 2.
This is a vertical reactor similar to that used for iron ore, where the In the lower part of the furnace body, tuyeres 3 are evenly distributed around the outer periphery of the furnace wall 2 and are closed into the furnace interior 19. The furnace bottom 1 is made of carbon, graphite brick, silicon carbide brick, chamotte brick, furnace wall 2, etc.
may be a refractory brick of magnesia type, alumina type, chamotte type, etc. The side wall part may be shorter than the iron ore right side. As for the raw material charging method, as illustrated in FIG. 2, it is preferable to layer each raw material as is well known in pig iron production.

This is because the briquette 5 and the lump coke 4 generally have different sizes, so if they are mixed, they will become tightly packed and gas permeability will be poor. Bulquette 5 and lump coke 4
The grain size is made as uniform as possible by dividing the grain, etc.
Even so, some variation is unavoidable. In general, gas passes through the periphery of a blast furnace more easily than the center, so in order to equalize the gas flow inside the furnace, use the above-mentioned barracks to fill the periphery of the blast furnace with small particles such as briquettes, etc. It is better to fill it with coke. By way of example, the well-known bell bagging device 17 is suitable for this purpose. A wind box 13 passes through the tuyere 3 to uniformly distribute the hot air received from the preheater 11 around the furnace.

The regenerative preheater 11 is connected to the oxygen tank 12 via the valve 14 as well as the oxygen tank 12. oxygen tank 12
When the operation is continued by adjusting the temperature at the tuyere tip using the preheater 11, most of the chromium and iron in the ore fall into the reduced pool 10'. The gangue part in the chromium ore and the slag agent are also melted to form a slag layer 21, and the slag layer 21 is formed.
0, it accumulates on the metal layer 20. In this way, the reduction reaction and dissolution proceed smoothly, and as the reaction progresses, the raw material layer naturally moves downward, so that the raw material can be charged in accordance with this movement. When a certain amount of slag and metal have accumulated, remove the slag tap 6 and metal tap port 1 respectively.
Hot water starts from 5. The yield of chromium reaches over 90%.
That is, more than 90% of the chromium in the ore is recovered in the metal layer. The Cr203 content in the slag is 5% or less. The embodiments of the present invention are described above.

The compositions of the raw materials used in the examples were as shown in the table below. Table 1 The blast furnace used had a shape as shown in Figure 2, and the hearth diameter (
The inner diameter of the furnace bottom is 100 m, and the height from the tuyere to the furnace top is 4.
The ship was 3.0 m wide and had an internal volume of about 3.2 m.

Example 1 Blast furnace charging materials were prepared in the order shown in Table 2 below.

Table 2 Remarks [1' Carbon factor = 1.0 means that there is just the right amount of carbon necessary for the reaction in the chromium reduction formula '1 mentioned above.

The above formulation was C/S=0.5 and AMF=0.5.

The raw material was charged into the blast furnace in layers. The hot air temperature of the blast furnace was 70,000. Oxygen enriched with 02 content of 30%
air was used. The temperature at the tuyere tip is 2400oo, the air flow rate is 10〆/min, the furnace top pressure (
Gauge pressure) was 0.1k9/m. When the operation was performed under these conditions, ferrochrome metal paper was obtained. A product was obtained in the proportion of 5 parts by weight of slag and 40.2 parts by weight of slag. The yield of chromium was 90%. The analytical values of ferrochrome metal are 837%C, 8.8%C, 0.7%Sj, 0.01
It was high carbon ferrochrome with %S, 0.04%P, and the balance iron. The average slag composition is Si〇235-8%, A
Evening 2〇313-5%, Mg〇23.7%, Ca015.
9%, Cr203.1%, and Fe01.2%.
The production amount was 3.0 tons/day. Example 2 Blast furnace raw materials were prepared in the order shown in Table 3 below.

C/S = 1.25, AMF = 0.5 with the combinations in Table 3 and above
The resulting raw materials were placed in bags in layers in a blast furnace.

Blast furnace hot air temperature 500 pm, oxygen enriched air with 02 content of 34%, air flow rate 30/min, furnace top pressure (
gauge pressure) 2.0kg/re, wing tip theoretical combustion temperature 240
The operation was carried out at 0qo. As a result, ferrochrome 39
．． A product was obtained in a ratio of part by weight of base to 41.0 parts by weight of slag, and the analytical value of ferrochrome was 55.2% Cr, 7.
9%C, 0.5%Si, 0.02%S and 0.22%P
, the balance was Fe. The yield of chromium is 95%. In addition, the slag composition is SiQ21.8~26.5%, A20
311.8-14.2%, Mg021.8-24.6%
, Ca024.6-26.8%, Cr2033.0-4
．． 1%, Fe00.9-1.4. The production amount was 6.5 tons/day. Comparative Example 1 (Example using granulated pellets of chromium ore powder not mixed with carbon reducing agent) Blast furnace raw materials were prepared in the order shown in Table 4.

Table 4 In this example, lump coke was used instead of the carbon reducing agent in the pellet in Example 1, but AM circle = 0.5
, C/S=0.5 are the same as in the first embodiment.

The blast furnace was operated under the same operating conditions as in Example 1 using this charged raw material. As a result, hot water could not be tapped, and the furnace operation was unsuccessful. After dismantling the furnace (furnace moat), some metal slag was found in the sump, but small droplets of metal were suspended in the slag. The reaction of the ore did not proceed beyond this point. Comparative Example 2 (Example using chromium lump ore) The grade of the lump ore used was as shown in Table 5 below.

The ores listed in Table 5 and above were divided into coarsely crushed ages, and those of 10 to 3 Q were used.

The formulation was as follows.

Ore C 35. Mother weight part Cr/Fe weight ratio=2.
6 Ore D 64.4 Lump coke 1000″ Lime right 23 parts by weight AMF=0.5 Silica stone 1
6. Part by weight C/S=0.5 The open furnace conditions were the same as in Example 1.

As a result, hot water could not be tapped, and the furnace operation was unsuccessful. Furthermore, in this example, when the furnace was excavated after completion, almost no metal slag was found in the pool. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a drawing for explaining the position and temperature at which the temperature in the blast furnace is measured according to the method of the present invention, and Fig. 2 is a diagram showing the method of smelting ferrochrome using the blast furnace according to the method of the present invention. FIG. 2 is a schematic diagram showing one embodiment of the equipment.

1... Blast furnace bottom, 2... Side wall, 3... Tuyere, 4
... lump coke, 5 ... group key, 9 ... blower,
11... Subheater, 12... Oxygen tank, 13... Wind box, 15... Metal tap opening, 16... Slagtatsu Pro, 17... Bag-filled bell, A... Massive zone, B... Softening zone, C... Melt dripping zone, D... Water pool part.

Figure 1 Figure 2

Claims (1)

[Claims] 1 Adding carbonaceous reducing agent powder to chromium ore powder using the following formula: 7r_
2O_3 + 27C → 2Cr_7C_3 + 21CO is mixed at 0.8 to 1.4 times the required amount to form a briquette, and this briquette is charged into a blast furnace together with lump coke, so that the theoretical combustion temperature at the tip of the tuyere from the tuyere of the blast furnace is 2000 to 2600.
Reduction is performed by blowing preheated oxygen-containing gas at a flow rate of 3 to 30 m^3/m^2 min per cross-sectional area of the tuyere level furnace to reduce the Cr_2O_3 in the slag.
The concentration of chromium in ferrochrome is 40% or less.
% or more. 2. The method for producing ferrochrome according to claim 1, characterized in that the absolute pressure at the top of the blast furnace is set to a high pressure of more than 1 kg/cm^2 and less than 3 kg/cm^2 by the injected preheated oxygen-containing gas. . 3. The ferrochrome ore powder has a fine particle size of 45 mesh or less, the carbonaceous material has a particle size of 45 mesh or less, the briquette size is 10 to 50 mm, and the lump coke size is 30 mm or less. 100mm to 100mm, and this lump coke is 150 to 500k per ton of briquette.
3. The method for producing ferrochrome according to claim 1 or 2, characterized in that ferrochrome is charged. 4 The (CaO (wt%))/(SiO_2 (wt%)) ratio of the slag is 0.4 to 1.3, and (Al
_2O_3 (weight%) + MgO (weight%)) / (CaO
(weight%) + SiO_2 (weight%) + MgO (weight%)
+Al_2O_3 (wt%)) is charged into the slag material so that it is 0.4 to 0.8. .