JP2853281B2 - Pig iron production method - Google Patents

Description

The present invention relates to a method for producing pig iron using a scrap and iron ore as an iron source using a cylindrical furnace having a relatively simple structure similar to a converter for steelmaking. The present invention relates to a method for producing pig iron with high thermal efficiency by preventing the occurrence of hanging and gas blow-through during operation.

(Prior art) At present, most of pig iron is manufactured by a blast furnace. The blast furnace iron making method itself has been continuously improved over the years, and has become an extremely excellent technique for mass production of pig iron. However, the blast furnace iron making method uses sintered ore as an iron source and high-quality coke as a fuel (reducing material), and there are limitations on available raw fuels. In addition, blast furnaces in recent years have become enormous, and since they cannot be easily stopped and restarted after they have been fired, they lack flexibility in responding to changes in steel material demand.

In order to solve the problems of the conventional blast furnace iron making method as described above, the present applicant uses a cylindrical furnace similar to a converter for steelmaking and uses a new iron making method using ore and scrap as an iron source. And a patent application was filed earlier (Japanese Patent Laid-Open No. 1-2907).
No. 11).

In the above pig iron manufacturing method, a cylindrical furnace 1 of a converter type as shown in FIG. 1 is used. As shown in the drawing, the cylindrical furnace 1 has an opening 2 for discharging gas inside the furnace and charging raw materials at an upper part of the furnace, a primary tuyere 3 for blowing a supporting gas and a fuel as needed at a lower part of the furnace wall, Secondary tuyere 4, injecting a supporting gas into the upper furnace wall,
A tap hole 5 for discharging hot metal and slag 8 is provided at the furnace bottom.

In order to produce hot metal using the cylindrical furnace 1, first, a coke packed bed 7 is provided at a lower part in the furnace, and a scrap 6-1 is placed thereon.
And a filling layer 6 of iron ore 6-2. The fuel is blown into the lower coke layer 7 from the primary tuyere 3 and, if necessary, fuel to cause a reaction represented by the following formula (1), and the heat of the reaction keeps the coke packed layer 7 at a high temperature.

C + 1/20 ₂ → CO + 29,400 kcal / kmol · C (1) The CO generated by the above equation (1) is used as a combustible gas blown from the secondary tuyere 4 at the packed layer 6 of scrap and iron ore. The reaction (secondary combustion) of the following equation (2) occurs. The heat of reaction is used to heat and melt the scrap and iron ore.

CO + 1/20 ₂ → CO ₂ +67,590 kcal / kmol · CO (2) The iron ore (molten iron oxide) melted by this reaction is dropped on the lower coke layer 7 and the high temperature coke and the following formula (3) Reacts immediately after reaction.

Fe ₂ O ₃ + 3C → 2Fe + 3CO −108,090 kcal / kmol · Fe ₂ O ₃ … (3) In the reaction of the above formula (3), there is no CO ₂ nearby, so the reaction of the formula (3) is inhibited by CO ₂ It will not be done. The CO generated in the equations (1) and (3) is subjected to secondary combustion in the packed bed 6 of scrap and iron ore, and is effectively used for heating and melting them to achieve high fuel efficiency. .

As described above, according to the method for producing hot metal proposed earlier by the present applicant, hot metal can be produced from scrap and iron ore with high efficiency in a converter type cylindrical furnace. It is important to charge the raw material layer into the furnace evenly. Therefore, the present inventors have also developed a method for controlling the distribution of the charge, and have applied for a patent as Japanese Patent Application No. 1-239598.

However, in the charge distribution control method described above, the charged raw material can be uniformly distributed at the time of charging the raw material, but it is not a means for correcting the uneven distribution of the raw material generated during the operation after the charging. However, it is difficult to suppress or prevent blow-by or shelving with this apparatus alone. Leaving the stairwell or shelf hanging as it is, the recovery rate of the sensible heat of the high-temperature gas decreases, and the fuel consumption rate deteriorates. Also, if you try to prevent blow-by or shelves, you can reduce the supply of supporting gas,
Alternatively, it must be stopped, resulting in a significant decrease in production efficiency.

Therefore, the present inventors further studied and, as means for preventing shelves hanging in the furnace during operation and preventing blow-through, the furnace body was repeatedly tilted to the left and right during the operation of the cylindrical furnace, so that the furnace interior was Developed a method of uniforming the distribution of incoming materials and unloading of furnace interior materials, and a method of preventing blow-through by increasing or decreasing the gas flow rate according to the height of the raw material layer in the furnace when the furnace body tilts.
A patent application was filed as Japanese Patent Application No. 1-333227.

However, in the above method, since the furnace body can be repeatedly tilted only in one direction, the uniformity of the charge distribution in the direction perpendicular to the direction becomes insufficient, and the unbalance of unloading is completely prevented. Can not.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for producing pig iron from scrap and iron ore using a cylindrical furnace, by suppressing preferential melting of a material in front of a tuyere, so as to prevent gas blow-through or shelf. The purpose is to produce pig iron efficiently by preventing the formation of suspension, and the specific purpose is to use a sinusoidal wave to measure the flow rate of fuel and supporting gas blown from each tuyere of the primary tuyere and / or the secondary tuyere. It is an object of the present invention to provide a method for producing pig iron by blowing air out of phase and out of phase.

(Means for Solving the Problems) The present inventors have repeated the melting test of the cylindrical furnace and advanced the investigation, and as a result, obtained the following knowledge.

(A) A raceway similar to that of the blast furnace is formed in front of the primary tuyere of the coke packed bed in the cylindrical furnace, and the raw material preferentially dissolves before the secondary tuyere of the ore and scrap packed bed, and the ore A raceway in which the particles circulate is formed.

(B) When the tuyere supporting gas flow rate is increased, the raceway grows more than necessary and gas blow-through occurs. Therefore, the number of tuyere is increased to reduce the supporting fuel gas flow per tuyere. As a result, the raceway becomes smaller, and blow-by is prevented.

(C) However, when the number of tuyeres is increased, the refractories around the tuyeres are preferentially melted, so that the entire furnace wall is melted, the refractory costs are increased, and the equipment costs are increased.

The present invention has been made based on the above findings,
The gist lies in the following methods (1) and (2) for producing pig iron.

(1) Using a cylindrical furnace having a structure as shown in FIG. 1, a coke packed layer is formed from the furnace bottom to a level including the primary tuyere, and scrap is formed to a level including the secondary tuyere on the upper part. And forming a packed bed mainly composed of iron ore, and then injecting fuel and combustible gas from a primary tuyere and blowing a combustible gas from a secondary tuyere to produce hot metal, comprising: Changing the flow rate of the combustion supporting gas or the flow rates of the combustion supporting gas and fuel from each tuyere constituting the mouth in a sinusoidal manner so as to satisfy the following equation (a); and the flow rate from each tuyere. Give the change a phase shift,
A method for producing pig iron, characterized in that air is blown so that the total sum of the tuyere flow rates is always constant.

(2) A method for producing pig iron which basically performs the same operation as the above (1), wherein the flow rate of the supporting gas blown from each tuyere constituting the secondary tuyere satisfies the following expression (b). , Sinusoidally, and the flow rate change from each tuyere with a phase shift,
A method for producing pig iron, characterized in that air is blown so that the total sum of the tuyere flow rates is always constant.

It is.

In the method of the present invention, as the ore charged from the upper opening of the furnace, Mn, Cr, Mo, Ni
Ore containing a large amount of or the like or oxides thereof can be used. In addition to these ores and coke, auxiliary raw materials such as quartzite, limestone, serpentine, and fluorite can be charged. As the scrap, it is possible to use a high alloy scrap such as a stainless steel scrap to reuse useful elements therein.

Iron ore can be blown from the primary and / or secondary tuyeres as well as fine ore as well as from the upper opening of the furnace. The injection of the fine ore from each tuyere may be performed by changing the total amount of the injection in a sinusoidal manner and distributing it in proportion to the ratio of the flow rate of the supporting gas at each tuyere.

The supporting gas blown from the primary and secondary tuyeres is
Although it is an oxygen-containing gas as described above, it is desirable to blow gas or liquid fuel such as pulverized coal, heavy oil, or natural gas together with the supporting gas from the primary tuyere. Further, a low sulfur pig iron can be produced by blowing a desulfurizing agent such as CaO from the tuyere.

It is preferable that the amount of the desulfurizing agent blown from each tuyere is blown from each tuyere in the same manner as the above-mentioned powder ore blowing, with the whole amount being proportionally distributed to the ratio of the flow rate of the combustible gas at each tuyere.

(Operation) The method of the present invention will be specifically described based on test results of a cylindrical furnace.

The raceway depth formed in the raw material packed layer in front of the tuyere by acid supply from the tuyere was measured using the same cylindrical furnace as in Examples described later, and the relationship with the occurrence of blow-through was investigated.

The raceway depth was measured using a measuring device shown in FIG. 2 developed for measuring the raceway depth of a blast furnace. This measuring device has a sound 10, a drive device 11 and a load cell 12. In the measurement, the sonde 10 is moved forward by the driving device 11, passes through the packing box 13 and the gate valve 14, and is inserted into the raceway 16 from the tuyere 15 (the tuyere in FIG. 2 is for a blast furnace). The insertion load is measured by the load cell 12, and the raceway depth (D in FIG. 2) is measured from the sonde insertion length when the tip of the sonde 10 hits the raw material filling layer at the raceway tip and the insertion load rises sharply.

The raceway depth D indicates the distance from the tuyere tip to the raceway tip.

FIG. 3 is a diagram showing the relationship between the oxygen flow rate per primary tuyere or secondary tuyere, the raceway depth and the presence or absence of blow-through, and FIG. When the primary tuyere oxygen flow rate is changed while the oxygen flow rate is kept constant at 250 Nm ³ / Hr, FIG. 3 (b) shows the secondary tuyere oxygen flow rate where the oxygen flow rate per primary tuyere is kept constant at 500 Nm ³ / Hr. Is changed.

As shown in FIG. 3 (a), a coke raceway similar to that of the blast furnace is formed in front of the primary tuyere of the coke packed bed, and when the primary tuyere oxygen flow exceeds 500 Nm ³ / Hr. Becomes 400 mm or more, and blow-through occurs.

Further, as shown in FIG. 3 (b), formation of a raceway in which the raw material preferentially dissolves and the ore particles float and circulate was confirmed in front of the secondary tuyere of the ore and scrap packed bed,
When the secondary tuyere oxygen flow exceeds 300 Nm ³ / Hr · line, the raceway depth becomes 200 mm or more and blow-through occurs.

When the above-mentioned blow-through occurs, the gas flow distribution in the furnace becomes extremely uneven, and in places where the gas does not easily flow, heating and melting of the scrap and ore are delayed, so-called shelf hanging is formed, and the unloading of the raw material stagnates. Sometimes.

In the method of the present invention, in order to prevent blow-by and shelves hanging during operation, the flow rate of the supporting gas from each tuyere is changed sinusoidally, and when the flow rate is large, an appropriate raceway is formed to form a furnace. It promotes uniform distribution of the internal gas flow, and when the flow rate is small, reduces the raceway and promotes the unloading of raw materials.

First, the flow rate of the fuel and the supporting gas blown from the primary tuyere in the invention of (1) will be specifically described with an example in which the primary tuyere is constituted by four tuyeres.

1, 2, 3, 4 for the four primary tuyeres (i = 4)
Supporting gas flow from the tuyere (Nm ³ / Hr) And the air is blown out of phase.

FIG. 4 shows the change over time in the flow rate of the combustible gas of each tuyere constituting the primary tuyere and all tuyeres. As shown in the figure, the flow rate of the supporting gas from each tuyere is Is periodically changed, so that when the flow rate of the supporting gas is small, the load of the raw material packed layer overcomes the pressure loss caused by the gas, and the raw material falls into the raceway space to reduce the raceway. On the other hand, the raceway expands when the flow rate of the supporting gas is large. As described above, since the raceway repeatedly shrinks and expands, the unloading of the raw material proceeds smoothly, and the raceway does not become large and does not blow through. Also, since there is a phase shift between the four tuyeres, the total flow rate of the supporting gas at the primary tuyeres (1200 Nm ³ / Hr) is kept constant. Therefore, air can be blown without lowering the productivity. When the supporting gas is blown from the primary tuyere, since the fuel burns with the supporting gas, it is necessary to blow the fuel in proportion to the ratio of the supporting gas flow of each tuyere whose sinusoidal waveform is changed. desirable. In other words, it is preferable to match the combustion supporting gas blowing method.

Next, the primary tuyere and the secondary tuyere each have four flow rates of the combustion supporting gas from the primary tuyere and the secondary combustion tuyere. This will be specifically described by taking the case of (1) as an example.

The blowing flow rate of the flammable gas from each tuyere constituting the primary tuyere is as described above, but the blowing from each tuyere constituting the secondary tuyere is the installation of the primary tuyere and the secondary tuyere. It is desirable to change the phase shift depending on the relationship with the position.

FIG. 5 is a diagram showing a relative arrangement relationship of the primary tuyere and the secondary tuyere in the furnace circumferential direction. FIG. 5 (a) shows that the primary tuyere 3 and the secondary tuyere 4 are in the height direction. FIG. 5B shows a case where the primary tuyere and the secondary tuyere 4 are arranged in series in the height direction.

In the case of FIG. 5 (a), the secondary tuyeres 4-1, 4-2, 4
-3 and 4-4, the flow rate of the supporting gas from the tuyeres (Nm ³ / H
r) And the primary tuyeres 3-1, 3-2, 3-3 and 3
As in the case of -4, the air is blown out of phase.

In this case, the CO gas generated in front of the tuyere of the primary tuyere 3-1 rises in the furnace, and is generated by the in-phase combustible gas supplied from the adjacent secondary tuyere 4-1 above the furnace. Since the fuel burns, the combustion proceeds without any trouble. Moreover, since the primary tuyere 3-1 and the secondary tuyere 4-1 are arranged in a staggered arrangement, the gas pressure loss in the furnace is reduced as compared with the serial arrangement, so that occurrence of blow-through can be prevented.

In the case of FIG. 5 (b), the secondary tuyeres 4-1, 4-2, 4
-3 and 4-4, the flow rate of the supporting gas from the tuyeres (Nm ³ / H
r) And the primary tuyeres 3-1, 3-2, 3-3 and 3
The air is blown with the flow rate of -4 shifted by 1/2 cycle.

In this case, the primary tuyere and the secondary tuyere are arranged in series in the height direction, and the CO gas generated in front of the primary tuyere rises in the furnace and shifts by 1/2 cycle from the secondary tuyere. It is burned by the supporting gas. Even if there is a shift of 1/2 cycle, the gas in the furnace is mixed quickly, so that there is almost no hindrance to combustion, and the pressure loss in the furnace gas is reduced by the amount of the shift, thereby preventing the occurrence of blow-through.

According to this blowing method, the raceway immediately before and after the primary tuyere and the secondary tuyere are repeatedly reduced and enlarged, so that the raceway does not enlarge and blow through.

As described above, the feature of the method of the present invention lies in that the flow rate of the supporting gas is blown sinusoidally and out of phase.
By repeatedly reducing and enlarging the raceway immediately before the tuyere, it is possible to promote the unloading of raw materials and the uniformity of the gas flow distribution in the furnace, and prevent the hanging of shelves and the occurrence of blow-through.

Hereinafter, the effects of the present invention will be specifically described with reference to examples in comparison with comparative examples.

(Example) The furnace used was the cylindrical furnace shown in Fig. 1, which can be repeatedly tilted around a trunnion shaft as a rotation axis. Furnace size is 1.5m in diameter, furnace diameter is 1.2m, height from furnace bottom to furnace mouth is 3.8
m, a furnace capacity 6.0 m ^3, from the furnace bottom 0.8m top of the furnace wall 90
90 degrees on the four primary tuyeres and the furnace wall 1.8 m above the furnace bottom
Four secondary tuyeres are provided at an interval of degrees. The primary tuyeres and secondary tuyeres were arranged in a staggered manner in the height direction as shown in FIG. 5 (b).

Iron source, the maximum dimension 400 mm, the scrap bulk density 3.5t / m ³ (iron purity of 99%), the compositions shown in Table 2 using the lump ore particle size 10 mm, the fuel is described in Table 2 Lump coke and pulverized coal were used.

In the embodiment, as shown in FIG. 1, a coke layer 7 and a scrap and iron ore layer 6 are first charged into a furnace to perform a startup operation.
When a certain amount of each layer descended, a new coke layer 7 'and a scrap and iron ore layer 6' were added to control the layer height to 3.2 m, and the semi-continuous operation was started.

(Example 1) While the scrap and the iron ore are melted semi-continuously while feeding.

(Example 2) While the scrap and the iron ore are melted semi-continuously while feeding.

(Comparative Example 1) In this case, scrap and iron ore are melted semi-continuously while the furnace body is repeatedly tilted within the range of the maximum tilting angle of 30 ° while supplying iron.

(Comparative Example 2) Melting was performed under the same conditions as Comparative Example 1 except that the furnace body was not tilted.

 Table 3 shows the operating results of the examples and comparative examples.

In Examples 1 and 2, as compared with Comparative Example 2 in which the furnace was fixed, the occurrence frequency of blow-through and shelf hanging was reduced by 80 to 90%, so that the heat exchange efficiency was improved, and the average furnace top gas temperature was 27 to 30 ° C.
It has been reduced and the variation has been reduced. As a result, the average unit fuel consumption was 10.9-12.7%, and the average oxygen unit 11.2-13.0%
The average hot metal production rate increased by 12.5-15.3%.

Also, as compared with Comparative Example 1 in which the furnace body was repeatedly tilted, the fuel consumption rate, oxygen consumption rate, and hot metal production rate improved, and no decrease in the furnace top gas recovery rate was observed.

(Effects of the Invention) According to the method of the present invention, a cylindrical furnace that is much smaller and simpler than a blast furnace is used, and scrap is used together with iron ore as an iron source, thereby providing a highly flexible pig iron. It can be performed. Moreover, the blowing method from the primary and secondary tuyeres,
Only by sinusoidally displacing, it is possible to reduce the occurrence of shelves hanging during operation, gas blow-through, and the like. As a result, hot metal can be produced with high thermal efficiency, and the economical effect by reducing the fuel consumption unit and oxygen consumption unit is large. Further, the operation is stabilized and the productivity is improved, so that an effect of increasing the production can be obtained.

[Brief description of the drawings]

FIG. 1 is a view for explaining a cylindrical furnace used in the pig iron manufacturing method of the present invention and a state in which raw materials are charged. FIG. 2 is a diagram illustrating an example of a raceway depth measuring device. FIG. 3 is a diagram showing the relationship between the oxygen flow rate per primary or secondary tuyere, the raceway depth, and the presence or absence of blow-through. FIG. 3 (a) shows the secondary tuyere oxygen flow rate. FIG. 3 (b) shows the case where the primary tuyere oxygen flow rate is kept constant and the secondary tuyere oxygen flow rate is kept constant. FIG. 4 is a diagram showing a change over time in the flow rate of the combustible gas of each tuyere constituting the primary tuyere and all tuyeres in the blowing method of the present invention. FIG. 5 is a diagram showing the relative arrangement of the primary tuyere and the secondary tuyere in the circumferential direction and the height direction of the furnace when the method of the present invention is carried out. FIG. In case of type arrangement,
FIG. 5 (b) shows a case of a serial arrangement.

Claims (2)

(57) [Claims] 1. An opening for charging raw materials and discharging gas at an upper part of a furnace, a primary tuyere, a discharge port and a taphole at a furnace bottom and / or a lower furnace wall, and a secondary tuyere at an upper furnace wall. Using a cylindrical furnace having respectively, a packed bed of coke is formed from the furnace bottom to a level including the primary tuyere, and a packed bed mainly composed of scrap and iron ore up to a level including the secondary tuyere. After forming, the fuel and the supporting gas from the primary tuyeres,
A method for producing hot metal by blowing a supporting gas from a secondary tuyere, wherein the flow rate of the supporting gas or the flow of the supporting gas and the fuel from each tuyere constituting the primary tuyere is defined as (a) ) Is changed sinusoidally so as to satisfy the expression, and the above flow rate change from each tuyere has a phase shift.
A method for producing pig iron, characterized in that air is blown so that the sum of the tuyere flow rates is always constant. 2. The flow rate of the supporting gas blown from each tuyere constituting the secondary tuyere is changed sinusoidally so as to satisfy the following equation (b), and the phase of the change in the flow rate from each tuyere is changed. The method for producing pig iron according to claim 1, wherein the air is blown so that the total sum of the tuyere flow rates is always constant with a deviation.