JPS61104014A - Method for reducing mn ore with high efficiency in oxidation refining furnace - Google Patents

Abstract

PURPOSE:To reduce extremely efficiently Mn ore in an industrial scale in the stage of reducing the Mn ore in a oxidation refining furnace permitting bottom blowing by combining a novel method for preliminary treatment of molten iron and treatment stage thereby desiliconizing stably the molten iron and dephosphorizing advantageously the same. CONSTITUTION:Gas and solid oxygen are simultaneously blown into the molten iron and the ratio of gaseous oxygen is adjusted to 10-50% to desiliconize the molten iron so that the Si concn. in the molten iron attains <=0.15% and the molten iron temp. attains 1,400-1,480 deg.C in a mixer car which is a vessel for transporting the molten iron between a blast furnace and converter. The molten iron after discharge of slag is fed out to a converter charging pan 4 and a free board 3 is inserted into the pan 4. A dephosphorizing agent as well as gas and solid oxygen are blown into the molten iron under said board. The ratio of the gaseous oxygen is adjusted to 10-50% and after the treatment, the P and S levels are decreased to the standard value for the product or below and in this stage the molten iron temp. after the treatment is maintained at >=1,300 deg.C. The molten iron is subjected to decarburization and Mn reduction refining by bottom blowing O2 or O2-contg. gas at >=0.08Nm<3>/ton min flow rate while adding the refining furnace Mn ore to the furnace inside.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for reducing Mn ore with high efficiency when refining hot metal in a smelting furnace.

Conventional technology Iron and steel manufacturers changed their refining method from the E-blowing method to the composite refining method, and as a result, strong stirring of molten steel by bottom blowing was used, which improved the base ratio of Mn ore in the furnace, resulting in composite refining. In the furnace, 5 to 10 kg of Mn ore is added to the molten steel, and by the end of the refining, 0 h is added to the molten steel.
．． Currently, the reduction is between 25% and 0.30%.

On the other hand, as a method for removing Si, P, and S, which are impurities in hot metal, at the hot metal stage, there are various hot metal pretreatment methods described in S 54.10.15 Steel Handbook published by Maruzen Co., Ltd., No. 2, pp. 4311 to 453. .

Problems to be Solved by the Invention The current Mn ore reduction and refining method described above has the following problems when carried out using general hot metal (Si% = 0.2 to Q, fi%). Ta.

・xl Because the amount of slag generated in the complex smelting furnace to remove impurities from hot metal is as high as 70~loOkg par steel, M
The reduction rate of n ore is extremely low at 25-45%.

In addition, when carrying out the hot metal pretreatment described above in a mixer car, which is a general container for transporting hot metal between a blast furnace and a converter, the Si% of the hot metal must be reduced to 0.15% or less, which is the most advantageous condition for dephosphorization. When desiliconization is attempted, slag forms during the desiliconization process in the pig iron mixer car and overflows from the pig iron mixer furnace mouth, so the amount of hot metal received by the pig iron mixer car must be much larger than the specified capacity.

Since the amount of pig iron received is small, the heat dissipated from the hot metal in the pig iron mixing car increases. After the desiliconization process, the slag removal and dephosphorization treatment carried out in the same pig iron mixer car take a considerable amount of time, and the amount of heat dissipated from the pig iron mixer car is further doubled, and the heat content of the hot metal greatly increases. descend. For this reason, there is no thermal margin to sufficiently reduce Mn ore in the combined smelting furnace, making refining work practically impossible.

Furthermore, as described above, when desanding and dephosphorization and sulfurization reactions are carried out in a pigeon mixer car, the slag cannot be completely removed because the pigtail mixer car is elongated in shape. In particular, during dephosphorization treatment, it was impossible to carry out highly efficient dephosphorization due to the residual desilicating slag. That is, impurities (Si,
When using hot metal with low P and S), there is a large decrease in the pig iron receiving capacity of the mixed pig iron car and a large decrease in the heat content of the hot metal.
l! n From the point that the ore reducing power is insufficient and efficient dephosphorization cannot be carried out, ll! It has been impossible to economically and efficiently reduce n-ore in a complex smelting furnace.

The present invention solves each of the above-mentioned problems with a new amount of hot metal @
i. The purpose is to solve this problem by combining treatment methods and treatment steps, and to achieve a method for reducing Mn ore in an oxidation smelting furnace on an industrial scale, which has extremely high reduction efficiency.

Means for Solving the Problems The present invention solves the above problems, and in order to efficiently reduce Mn ore in an oxidation smelting furnace, the following steps are taken: Gaseous oxygen and solid oxygen are used as the main desiliconizing agents and are injected into the hot metal.The gaseous oxygen ratio is 10% so that the Si concentration in the hot metal is 0.15% or less and the hot metal temperature is 1400-1480℃.
The desiliconization process is adjusted in the range of ~50%. After the slag is removed, a immersed freeboard is charged into the hot metal charging pot, and lime, fluorite, etc., which are dephosphorization cracks, and gaseous oxygen, which is an oxidizing agent, are charged. When injecting solid oxygen into hot metal, the gaseous oxygen ratio is adjusted within the range of 10% to 50%, and the P and S levels after treatment are within the product standard values, and the hot metal temperature after treatment is 1300℃ or higher. Dephosphorization process.

・■ After the above treatment, the hot metal is put into a smelting furnace, and Mn ore is not added into the furnace, and then a gas containing G or 02 is turned on at 0.08Nm'pa.
The steps of bottom blowing for more than 1 minute, decarburization, and Mn reduction refining are sequentially performed.

In other words, the conditions for reducing Mn ore at a high reduction rate in a combined smelting furnace are: ・Minimizing the slag j generated in p smelting, ・2) Keeping the amount of heat that can reduce Mn ore in the smelting furnace in hot metal reserve This condition can be achieved by improving the hot metal preparation method and by optimizing the process steps.
The present invention is intended to prevent a decrease in the heat content of hot metal as much as possible and to carry out the reduction of Mn ore in a smelting furnace extremely efficiently on an industrial scale.

action The above-mentioned means will be explained below along with their functions.

(1) Desiliconization process The technical issues in the desiliconization process when using a pig iron mixer car as a transport container are to receive a specified volume of molten metal into the mixer car and minimize heat loss through forming, slopping, etc. Low Si levels (0,15
The key point is how to remove silicate stably, down to % or less. Figure 1 shows 300 tons of hot metal mixed with CaO powder: C
aF2 powder: CaCL12 powder Niscale powder = 4.5:
This is a diagram showing the relationship between the Si value before dephosphorization and the dephosphorization efficiency in the dephosphorization treatment in which a dephosphorizing agent consisting of 1.0: 0.5: 4.0 was injected. It shows the degree to which phosphorus efficiency is improved.

Common desiliconization methods include blast furnace casthouse desiliconization, monoacid injection desulfurization, and monoacid or acid-free top blowing desulfurization, but all of these methods are used during the desulfurization process, especially up to the Si<0.20% level. When the desulfurization process is carried out, the desiliconization slag forms in the pig iron mixer car and overflows from the mixer car furnace mouth, making it impossible to perform the work.
%do not become).

We investigated the causes of slag foaming that occurs when the dephosphorization process reaches a low Si level, which is most advantageous for dephosphorization, and found that: 1) slag fluidity and CO gas release properties depending on slab temperature; 2) Amount of CO gas (decarburization amount) generated during desiliconization treatment, 3)
It was found that T a Fe% in the slag was the main cause.

Furthermore, we carried out desiliconization treatment by simultaneously injecting one acid (scale, iron ore powder, etc.) and an acid-free (oxygen-containing gas), and further carried out the air catalytic ratio (gaseous oxygen amount (kg) in the non-acid)/
Total amount of oxygen in solid acid (kg) x 100 to 10
The temperature after treatment was adjusted to 140% while adjusting in the range of ~50%.
By controlling the temperature between 0°C and 1480°C, the above-mentioned 1)
3) It was confirmed that it is possible to control the problem to an area where no slopping or forming occurs. Figure 2 shows the forming limit when 520T of hot metal is charged into a 600-gun pig iron mixer and desiliconization is performed by injection. Si value after desiliconization and T in treated slag @
The relationship diagram with the Fe concentration shows that when only one acid is used, the Si value after treatment falls into the forming region at 0.20% or less.

Even in injection desiliconization, if the acid-free ratio is less than 10%, the temperature after treatment is generally lower than 1400℃.
1, the slag fluidity deteriorates, the CO gas removal property worsens, and foaming occurs. On the other hand, in order to ensure the specified temperature in the dephosphorization process, the acid-free ratio in the dephosphorization process is set to 5.
If it exceeds 0%, it is not industrially viable.

In addition, if the acid-free ratio exceeds 50%, the temperature after treatment will be 148%.
When the temperature exceeds 0°C, the decarburization reaction occurs preferentially, and CO gas generation becomes large, causing foaming. If the acid-free ratio is too high, the refractory of the injection lance will melt and become unfeasible industrially. Become. Figure 3 is a diagram showing the relationship between lance life (total injection immersion time) and acid-free ratio during desiliconization treatment when iron ore powder is conveyed with 02 gas in the inner pipe and N2 gas in the outer pipe in a double-pipe lance. .

On the other hand, a method can be considered in which only solid acid is injected and the non-acid that causes problems in terms of corrosion of refractories is top-blown, but the temperature of the top-blown non-acid becomes high and the decarburization reaction occurs preferentially, resulting in carbon
Large amount of O gas generated → Not only does foaming occur, but the slag pressure rises on the slag surface, resulting in a high SOx concentration in the exhaust gas, etc., and the exhaust gas treatment equipment becomes enormous, making it uneconomical. Therefore, it is not commercially viable.

(2) DeP process The technical issue in the deP process is that after removing the desulfurization slag from the hot metal that has been desiliconized, the deP process is carried out to reduce the product to a level below the finished product standard (smelting furnace Before charging), the hot metal temperature 1 is the necessary thermal level to reduce Mn ore in the smelting furnace.
The problem is how to ensure a temperature of 300°C or higher using an industrially viable method.

After discharging the above hot metal into a converter charging ladle, we charged an immersed freeboard (Fig. 4) into the ladle, and deposited CaO1CaF2, Ca, which is a dephosphorization crack, inside the hot metal under the freeboard.
It has been found that this can be achieved extremely advantageously by adjusting and injecting monoacid and gas acid into Cl2 or the like at a gas ratio of 10% to 50%.

One method of dephosphorization treatment is to perform it inside the pig iron mixer car. In order to maintain the pre-hot metal temperature at 1,300℃ or higher, the acid-free ratio in the dephosphorization and sulfurization of the mixed pig iron car must be approximately 80% or higher, which is not commercially viable for the injection lance refractory hot-rubbing industry, and it cannot be used at extremely high temperatures. The dephosphorization efficiency is poor because of the dephosphorization process.

Another method is to perform injection dephosphorization in a large hot metal ladle without using an immersion freeboard, but this method increases the total amount of refractories in contact with the hot metal by about 40% or more compared to an immersion freeboard. , the amount of heat dispersed increases, and unless the acid-free ratio at the time of dephosphorization and sulfurization is about 70% or more, the specified hot metal temperature cannot be ensured and it is also not commercially viable.

The reason why the acid-free ratio is regulated in the range of 10% to 50% is that if the temperature after the desulfurization treatment can be maintained at 1400°C or higher, the acid-free ratio is 50% or less, which is advantageous for injection lance refractories. By the way, when using immersion freeboard, the temperature after dephosphorization treatment can be maintained at 1300℃ or higher, and in addition, the temperature of CaO1CaF
2. This is because it has been found that when injecting GaCl2, etc., an acid, and an acid-free into hot metal, the dephosphorization efficiency is highest when the acid-free ratio is about 10% to 30%. FIG. 5 shows the relationship between the acid-free ratio during dephosphorization and the dephosphorization efficiency.

゛ It is not clear why this range has the highest dephosphorization efficiency, but calcium ferrite (Ca
It is assumed that the production state of O-Fete is the best.

Furthermore, with regard to the P and S levels after dephosphorization and sulfurization treatment, the overall profit of the combined smelting furnace will be maximized by reducing them to below the standard values for finished products. Figure 6 shows the dephosphorization treatment P level and the smelting furnace Mn.
The relationship with the return rate is shown.

To summarize the features of the desulfurization and phosphorus sulfurization process that we have developed, we can compensate for the thermal level required for Mn ore reduction in the oxidation smelting furnace by combining solid and non-acid injection in the desulfurization and dephosphorization processes. Between N(
When the acid-free ratio exceeds 50%, the deterioration occurs rapidly), the desiliconization process,
By approximately evenly distributing the most desirable gas for the reaction in each process, and by using the immersion freeboard method to reduce the amount of heat dissipated during processing,
- It is possible to work with an acid-free ratio of 50% or less.

`` Various types of nozzles for desulfurization and dephosphorization injection lances are possible, such as single hole and double tuyere, but in our experiments, we used a double tube tuyere with no acid in the inner tube and desulfurizing agent or dephosphorization in the outer tube. It has been found that the method of flowing the fracture with a carrier gas results in the least corrosion of the refractory during acid-free use. Figure 7 shows an example of the special injection lance structure.

(3) Combined smelting furnace Mn ore reduction process The hot metal that has passed through the steps (1) and (2) basically does not require slag to remove P and S in the smelting furnace. The interior is slagless refining, but a small amount of basic additives such as CaQ and dolomite are naturally used to control slag components generated from impurities contained in the Mn ore.

The bottom-blown stirring gas used was 02 gas or a gas containing a can (a gas or air in which 02 was mixed with an inert gas such as Co, CO2, Ar, N, etc.), and the bottom blowing amount was 0.08 N/g.
If it is TON・min or more, 70 to 75% of the h ore will be reduced during refining.

In addition, the slag after refining generated in the step (3) has extremely low P and S, and contains Mn01Cab and MgO1.
Since FeO etc. are the main components, after the pulverization process, the sintering process,
It can be used as part of the solid acid in the dephosphorization process, as shown in (3)
) In the case where the slag generated in the process (1) and C2) is recycled, the -Kn reduction rate is 80 to 85%, which is a high reduction rate that exceeds that of the Fe-Mn electric furnace.

Example 800) Desulfurization treatment was performed as shown in Table 1 in a hot metal mixer car, and the hot metal was received into a 340-ton hot metal ladle, and then a immersion freeboard was charged and dephosphorization treatment was performed.

When h ore was reduced in a complex refining furnace, an extremely high Mn reduction yield was obtained as shown in the lower row of Table 1.

Table 1 also shows the cases in which the hot metal was not pretreated (Comparative Example 1) and the case in which the hot metal was pretreated with only one acid (Comparative Example 2). In Comparative Example 1, only desulfurization treatment was performed, but slagless blowing is not possible, so the Mn yield is low.In Comparative Example 2, slagless blowing is possible, but the margin is small, so the Mn yield of the invention, in which a large amount of Mn ore is introduced, is low. Effect The present invention performs solid and non-acid injection at the optimum acid-free ratio in both the desiliconization and dephosphorization processes, and maintains the hot metal temperature after hot metal treatment at a high level while suppressing refractory erosion. The immersion freeboard method can significantly shorten the hot metal treatment time, reduce the amount of heat dissipated during treatment, and reduce the unit consumption of large materials. temperature) and latent heat (
The P and S levels of the hot metal can be kept below the standard values for products that allow slagless decarburization in the combined smelting furnace, while maintaining the C concentration above 1300°C.

It becomes possible to secure the necessary and sufficient input amount of manganese ore. For this reason, the Mu yield in the complex refining furnace increases, and the M
The n value rises to the finished product Mn value, resulting in expensive Fe-M
The effects of the invention are extremely large, such as the ability to save a large amount of n-alloy iron, the amount of refractories used, and the ability to significantly save resources, save energy, and reduce costs throughout the entire process.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the Si value before dephosphorization and the dephosphorization efficiency in the dephosphorization process, Figure 2 is a diagram showing the forming limit during injection desorption in a pig iron mixing car, and Figure 3 is a diagram showing the relationship between the Si value before dephosphorization and the dephosphorization efficiency. Figure 4 is a schematic elevation view of immersed freeboard, Figure 5 is a diagram of the relationship between acid-free ratio and dephosphorization efficiency during dephosphorization, and Figure 6 is P after dephosphorization. Figure 7 is a diagram showing the relationship between the level and the Mn reduction rate of the combined refining furnace, and is a diagram showing an example of the special injection lance structure (double pipe).
A) is a cross-sectional view, and (b) is a side view. 1φ...Desulfurizing phosphor agent conveyance line, 2-1 injection lance 3 e e a immersion freeboard, 4φ fist・
Hot metal silver, 5... Hot metal, 6... Lu dephosphorization slag, 7...
Inner pipe, 8. Fist/outer pipe, 9. Injection lance made of refractory, 10. -% ugly introduction pipe, 11. Desiliconizing agent or dephosphorization removal introduction pipe.

Claims (1)

[Claims] When reducing Mn ore in the furnace using a bottom-blowing oxidation smelting furnace, (1) As the main desiliconizing agent in the pig iron mixer car, which is a container for transporting hot metal between the blast furnace and the converter, Gaseous oxygen and solid oxygen are simultaneously injected into hot metal, and the Si content of hot metal is 0.15.
% or less, a desiliconization process in which the gaseous oxygen ratio is adjusted in the range of 10% to 50% so that the hot metal temperature is 1400℃ to 1480℃, and (2) desiliconization slag is removed from the hot metal after desiliconization treatment. After that, the immersion freeboard is charged into the hot metal charging pot, and when injecting the dephosphorizing agent and the oxidizing agent gaseous oxygen and solid oxygen into the hot metal, the gaseous oxygen ratio is set in the range of 10% to 50%. and (3) a dephosphorization process in which the hot metal temperature after treatment is adjusted to 1300°C or higher while reducing the P and S levels after treatment to below the product standard values, and (3) the above desiliconization and dephosphorization. After treatment, the hot metal is sent to a smelting furnace to produce Mn.
A process of performing decarburization and Mn reduction refining by bottom-blowing O_2 or a gas containing O_2 at a flow rate of 0.08 Nm^3/TON・min or more while adding ore into the furnace. Highly efficient reduction method for Mn ore in an oxidation smelting furnace.