JPS5864344A - Manufacture of molten ferrosilicon in shaft furnace - Google Patents

Abstract

PURPOSE:To attain a higher silicon yield and a lower coke ratio in the manufacture of molten ferrosilicon by charging a siliceous starting material, coke and iron ore into a furnace and by blowing a gas with high O2 concn., by specifying the method of feeding the iron ore and the siliceous starting material. CONSTITUTION:A siliceous starting material such as silica, coke and iron ore are charged into a furnace, and by blowing a gas contg. >=70% O2 into the hearth, a part burning at a high temp. is formed to obtain molten ferrosilicon. At this time, more than halves of silicon and iron in the product are fed from briquettes of a finely pulverized uniform mixture of the siliceous starting material with the iron ore or from siliceous iron ore. For example, the siliceous starting material and the iron ore are finely pulverized, briquetted with a binder, and charged. Thus, a higher silicon yield and a lower coke ratio can be attained. The reason is considered to be that iron silicate which is a compound contg. iron oxide formed by the partial reduction of iron ore with silicic acid as the principal component of silica is melted in the early stage because of the low m.p. and droplets of the molten iron silicate are directly reduced on the surface of coke heated to a high temp.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing new ferrosilicon.

Among the ferroalloys mainly used in steel manufacturing, high carbon ferromanganese, ferrosilicon, and silicomanganese are used in large quantities in the manufacturing of ordinary steel.

Among these, high carbon ferromanganese was manufactured in shaft furnaces in ancient times, and is still produced in some cases today, but other than this, most of them are now manufactured in electric furnaces. As for ferrosilicon, there are few examples of it being produced in a simple shaft furnace that does not use electrical reduction. Since it requires a power of 2θθOKWH, it can be said to be a lump of electricity along with aluminum.

This is because extremely high temperatures and a large amount of heat are required to reduce the main raw material, such as silica stone, into metallic silicon.

The present inventor mixed a large amount of coke with a silicon raw material, for example, silica stone, which is normally used in the production of ferrosilicon, and charged the mixture into Shirt F, and melted it by sending room-temperature or preheated oxygen-enriched air through the tuyere. .

The test was conducted using a shaft furnace with an inner diameter of /θmφ and a height of 3m, and oxygen-enriched air obtained by diluting pure oxygen produced from air with a cryogenic separator with air from a blower was used as the pure oxygen content, gθθN per hour.
The performance of pumping and pumping operations was examined based on the nVh ratio. Five oxygen concentration conditions were used: /θθchi, 9θ%, 7θ%, 30%, and 33%. Table 1 shows some of the operating results obtained in this way.

Table 1 Example of operational results of silica scrap method *5i0 of silica
The yield to ferrosilicon was calculated using 2 as /θθchi.

※※The +λσ of the gas temperature variation with respect to the operating time was set as the highest.

The data in Table 1 is satisfactory in that ferrosilicon was produced using coke without directly using a large amount of electrical input, but it is unsatisfactory in that the silicon yield is low and the coke ratio is high. Met. The low silicon yield is due to the fact that it is discharged outside the furnace as slag or dust, and it was found that the amount of silicon is about the same as that of ferrosilicon.

Therefore, we tried using various solvents to solve this problem, but if iron ore was made into fine particles and mixed with silica stone and charged,
It was found that a slight decrease in coke ratio was observed. Taking a hint from this result, we tried using briquettes made by finely pulverizing iron ore and silicate raw materials and adding a caking agent, and using iron ore silicate, which is a compound in which iron ore and silicate raw materials are combined, and a remarkable improvement in performance was observed. Ta. Silica stone and iron ore were each crushed to a mesh size of /θθ mesh or less, and silica stone 37S, iron ore /, and cobaltin θ2S as a binder 7 were mixed in a weight ratio to obtain 20 van pellets using a normal manufacturing method. Table 2 shows the results of a manufacturing test for this container.

Table 2 Example of operation results for pellet method *The yield to ferrosilicon was calculated assuming 5iOz of silica stone as 108.

※※+2σ of the gas temperature fluctuation with respect to concavity during operation was set as the highest.

Based on the data in Table 1 and Table 1, the relationship between oxygen concentration, St concentration, coke ratio, and furnace top gas temperature is shown in Figure 7.2.
Show C. The coke ratio is expressed not by the amount of coke needed to hit the silicon in the ferrosilicon, but by the amount of coke required to hit the silicon in the ferrosilicon. In the figure, at the same oxygen concentration, the pellet method has a considerably lower coke ratio and a much higher Si yield. In both the silica-scrap method and the pellet method, both the coke ratio and the Si yield rapidly deteriorate when the oxygen concentration reaches the limit of 7θ.

Further, as shown in FIG. 2, in both the silica-scrap method and the pellet method, when the oxygen concentration decreases, the furnace top gas temperature increases significantly. In operation at an oxygen concentration of 7θ, the furnace top temperature is at most S
θθ°C, but it can be seen that as the oxygen concentration further decreases, the furnace top gas temperature further increases rapidly.

Naturally, in order to handle high-temperature gases, a refractory lining would be sufficient, but as will be explained later, when this shaft furnace is charged with raw materials such as coke, it is sealed from the atmosphere, so the lining creates a seal. breaking bad. However, if the structure is without lining, the device will be easily damaged.

Therefore, it has been found that it is preferable to set the oxygen concentration to 7θ or higher from the viewpoints of coke ratio, St rate, and top gas. It was also revealed that the pellet method, in which silica stone and iron ore are crushed and charged as pellets, has significantly better results than the method in which silica stone and succinite are charged.

The reason for this difference is not clear, but iron silicate, which is a compound with iron oxide produced by partial reduction of silicic acid iron ore, which is the main component of silica stone, has a low melting point, so it melts at an early stage. This is thought to be because the molten iron silicate droplets are directly reduced on the surface of the high-temperature coke.

Therefore, we conducted tests by changing the particle size of the coke.

In the experiments described so far, all coke had a particle size of 30~
! Omm blast furnace lump coke is used, but fine-grained breeze coke is generally used in ferroalloy production, and is also inexpensive. The test was /θ~30mm, 3θ~j Omm.

The conditions for obtaining ferrosilicon of 5i7j% or more were investigated using three types of coke of 50 to /θθmm, sending θθVAf to the above-mentioned furnace to blow 2θ oxygen, and using the above-mentioned pellets. The results are as follows.

Effect of coke particle size Coke particle size /θ~3θmrn 3θ~SorIL
msθ~/θθmm coke ratio 11. '17
32/ 3θS silicon yield 79
．． 2 93.0 93 B As can be seen from the above, those in the /θ to 3θ range have extremely high coke ratios and are therefore poor. Although it is better for the coke particle size to be coarse, it is clear that a particle size of at least 30 mm or more is required.

Example/゛With the flow sheet configuration shown in Fig. 3, the inner diameter/θmφ
Using a shaft furnace lined with refractories with a height of 3 m, an oxygen-containing gas with a purity of θ% produced from air by a molecular sieve type oxygen generator is used as oxygen.
It passed into the furnace at a rate of Nd/h. From the upper part of the furnace, the above-mentioned pellets manufactured in advance and blast furnace coke with a particle size of 3θ to 30 mm were alternately charged in a ratio of large holes /:/ in terms of weight ratio.

Charging was performed by alternately opening and closing double seal valves to ensure airtightness from the atmosphere. Oxygen is introduced into the furnace through water-cooled tuyeres.

Since the ferrosilicon produced by the reduction accumulated at the bottom of the furnace, the refractory spout was opened intermittently to take it out of the furnace and solidify it on a cast iron mold.

Organizing the operating data, the ferrosilicon production rate is 419/kg/h, the pellet supply rate is //3'l'4/hour, and the coke supply rate is //ggk/hour.
The St concentration in 7 erosilicon is 7 x q. Therefore, the required coke per Si/l is 32/l. The furnace top gas had an average temperature of 22.2°C and produced 3θgAv/hour.

When this gas was analyzed at the measurement points shown in Figure 3, it was found that
．． It was found that it had a calorific value of 2 Kcal/'t-.

The latent sensible heat of the furnace top gas of 9, including the sensible heat of the generated gas, is /, 33fX107 Kcal
/ls i. Furthermore, there is a sulfur content in the gas generated from the shaft furnace. It was found that it was included. When this gas is combusted, about θ/vo1% of the 802 is contained in the combustion gas. This is the case for the oxygen concentration θ in Table 2.

Example 2 The apparatus shown in FIG. 3 was used, and the same operating conditions as in Example 2 were adopted. The raw material was crushed to s-2θmm.
e2. ! ;, /'llr, 5iO2J5! ／'＊、
Iron silicate, whose main component is A203θ, is mixed with 6θ per hour, silica of the same particle size is mixed with 6θ per hour, and divided with coke of 6θ per hour. and charged alternately. The Si concentration in the obtained ferrosilicon was Huffj/chi, and the production rate was 67 gin per hour.

A sicoke that calculates Si/ from the data will require 3417t. Further, when calculating silica stone by /θθ%5i02, the yield of St is 9//%.

In Example 2, exactly half of the iron+silicon in ferrosilicon is supplied from pyrite. This is because silica is more common as a raw material, but iron seems to have a higher yield. The coke ratio of Example 2, 3gua t/lai, is much lower than that of Example 32/t/l s i in Table 1, corresponding example 3 t/l s i . In addition, the St yield is 9//%, 93θ bung6.
Compared to the 2nd wheel, the middle distance has been significantly improved.

As described above, when the method of this embodiment is compared with the scrap silica method, both the Si yield and the coke ratio are improved. This method is a compromise between the method of Example 1 and the scrap-silica method.

Now, as seen from Example/, the gas discharged from the shaft furnace contains a large amount of sulfur. Also, a lot of dust containing combustible substances is generated. The gas contains a lot of carbon monoxide and has an extremely large amount of heat. In consideration of these characteristics of the shaft furnace in this system, it has been found that it is desirable to have the equipment configuration as shown in FIG. 7 as an actual equipment. That is, the shaft furnace is directly supplied with oxygen from the oxygen generator. The shaft furnace is configured to be airtight from the atmosphere up to the combustion chamber, and raw materials such as silica coke scrap are supplied in a manner that prevents the introduction of the atmosphere into the furnace as much as possible. This is an advantage that arises from the fact that a large amount of coarse coke can be used, unlike the conventional ferrosilicon production method using an electric furnace, and there is less shelf hanging and shelf falling in the oven. The combustible gas generated from the furnace is mixed with air in the combustion chamber and combusted, the heat is recovered in the boiler, the dust is removed by a dry electrostatic precipitator, the gas is desulfurized, and it is released into the atmosphere from the chimney via an induced blower. This configuration is a facility for implementing the method of the present invention, in which a large amount of generated heat is recovered by power generation. It is optimal in terms of utilizing the operational safety of a shaft furnace. The modification method for this configuration is to install a dry type coarse dust remover after the shaft furnace, change the order of the dry type electrostatic precipitator and desulfurization equipment, and place the desulfurization equipment in front and the wet type electrostatic precipitator after it. Possible options include turning off the exhaust fan and using the pressure from the oxygen generator to push the gas up the chimney.

Now, if gas heat recovery is performed using such an actual flow sheet, the operation will be performed at the raw material consumption rate shown in Table 3. Table 3 shows the raw material units of the actual machine obtained from the experimental results of Example/. Table 3 shows examples of production results in electric furnace production of general 7-ero silicon for comparison. From Table 3, the general electric furnace method hits Si/, /, 2,3θθKW
Although this method uses about 9 times as much coke as it requires H, the amount of electricity used is covered by the recovered electricity. Calculating the operating cost by multiplying the values in Table 3 by the unit price by the market price at the time of application, the cost for this method is "2.j~" compared to the electric furnace method.
It becomes 3. Although the relative advantages and disadvantages of costs change depending on evaluation methods, location conditions, and economic conditions, such large cost differences do not change even with slight changes in conditions, and in most cases the advantages cannot be realized. This can be seen as an essential effect of this method.

This method is a method of producing ferrosilicon in a non-electric furnace, which was previously unknown, using a gas containing 70 cm or more of oxygen, appropriate shaft furnace dimensions, and coarse coke. It has a large economic effect.

Looking at examples of shaft furnace and shaft furnace methods in the production of ferroalloys, we find that the shaft furnace method is used for ferromanganese, but manganese is different from silicon and involves indirect reduction to reduce it from oxides, as well as direct reduction. Reduction can also be done at θθ℃; all silicon requires about /SSθ℃ for direct reduction, and when viewed as a ferroalloy, this difference is extremely large as it is the difference between whether it exceeds the melting point of iron or not. There is a difference.

Further, the amount of heat required for reduction per unit weight of silicon is about X<Z times that of manganese, and these differences can be said to be essentially different fields rather than similarities. .

Furthermore, it is known that iron ore and silica raw materials are supplied in the form of nodules in the production of ferrosilicon in an electric furnace, but it is well known that this method places emphasis on the reduction mechanism within the electric furnace. In a shaft furnace, the high temperature zone spreads widely, and iron silicate melts and drips onto the red-hot coke and is directly reduced. Electric furnaces and shaft furnaces that use a lot of coke have completely different effects even though they are similar.

Fig. 1 shows the relationship between the blown oxygen concentration, the Si concentration in the product, and the coke ratio in the silica-scrap method and the pellet method of the present invention, which were obtained from a pilot plant experiment in which oxygen gas θθ and Vh were supplied. It is a diagram. Figure 2 also shows θθW for oxygen.
This is a diagram showing the relationship between the blown oxygen concentration and the furnace top gas temperature, obtained from a pipette plant experiment with a /h supply. Figure 3 is a flow sheet for the experimental equipment, and Figure 9 is a flow sheet assuming an actual machine.

1st m 1t-tL&(%) 211I ・Conquest fl/L (%)

Claims (1)

[Claims] When producing molten ferrosilicon by charging silicic acid-containing raw materials such as silica stone, coke, and iron ore into a shaft furnace, the silicic acid raw material in which the majority of the silicon content and iron content of the finished product is pulverized and the iron ore are uniformly mixed. Production of molten ferrosilicon using a shaft furnace, which is supplied from nodules or iron silicate, and which introduces a gas containing 7θ or more of oxygen to form a high-temperature combustion zone in the hearth. Method.