JPH02263907A - Operating method for blowing powder in blast furnace tuyere - Google Patents

Abstract

PURPOSE:To reduce raw material cost under stable furnace condition in the case powdered coal and iron oxide are simultaneously blown from a tuyere by making theoretical combustion temp. before tuyere in the prescribed temp. range and further, specifying range of weight ratio of oxygen/powdered coal during blasting in the tuyere. CONSTITUTION:The blast furnace is operated by blowing >=150kg powdered coal and >=150kg iron oxide per ton of pig iron from the tuyere in a blast furnace at the same time, and making the theoretical combustion temp. before the tuyere within the range of 1800-2600 deg.C, and under such condition that the wt. ratio of oxygen/ powdered coal during blasting in the tuyere within the upper and lower limit range shown in the equation I and the equation II. Wherein, (PC): carbon content in the powdered coal (wt.%), (PH): hydrogen content in the fine powder coal. Further, it is preferable to blow about 30-60kg of slag making agent per ton of the pig iron from the tuyere in the blast furnace. By this method, combustibility of the powdered coal and smelting reduction of the sintered ore powder are secured and the operation under stable furnace condition without variation of blasting pressure and lowering of charging level can be continued.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention alleviates the raw material constraints of coal and ore and increases the blast furnace iron output ratio by injecting a large amount of pulverized coal and iron oxide through the blast furnace tuyere. and a blast furnace tuyere powder injection operation method for controlling hot metal composition.

(Prior Art) Conventionally, as a blast furnace operation mode, a liquid fuel injection operation was aimed at achieving a low coke ratio and high pig iron production ratio by injecting a large amount of liquid fuel such as heavy oil or tar through the tuyeres. However, as a result of the drastic change in the energy price system due to the sharp rise in crude oil prices in the first half of 1975, all-coke operation has become the mainstream for blast furnace operations.

Although this all-coke operation reduces fuel costs compared to liquid fuel injection operation, the theoretical combustion temperature before the tuyere is higher and the amount of hydrogen input to the blast furnace is also lower, making unloading unstable. Slips occur frequently and the Si content in the hot metal increases by 1 degree. This problem has been solved by using a large amount of humidity control, but instead,
New problems arose, including problems with coke oven production capacity due to an increase in the coke ratio, and a decrease in the maximum pig iron production ratio due to an increase in the air consumption rate and the limitations of the atrium.

Therefore, the number of blast furnaces that use pulverized coal as an inexpensive tuyere-injected fuel has increased, and in blast furnaces that have adopted such a method, a reduction in coke ratio has been achieved and a maximum iron production ratio has increased. Today, in Japan, the ratio of pulverized coal per ton of pig iron is 10
Some blast furnaces are operated at 0 kg (hereinafter expressed in the unit of r kg/ptJ) or more. Process J Vo
l, 1 (1988) p, 72).

On the other hand, today, sintered ore is used in large quantities as a raw material for blast furnace charging, accounting for 70 to 95% of the total amount of ore used, and due to its good reducibility and high temperature properties, it can be
This contributes to low fuel ratio operation.

Here, in the sintered ore manufacturing process, after sintering tlA,
In the process of crushing and sieving the sintered ore, fine grained sintered ore, that is, return ore, is generated under the sieve and is returned to the sintering machine. Usually, the amount of this return ore occupies 20 to 30% of the mixed raw material for sintering, and is linked to an increase in the energy for firing the sinter ore.

By reducing the amount of return ore of this sintered ore, the pot yield of sintered ore (
As one method of improving the product/(new raw material + return ore) Japan Iron and Steel Institute Lecture Proceedings, “Materials and Processes” νo
1.110 (1988) ρ, 110). According to this method, the amount of return ore was reduced and the sintered ore ladle yield improved from 75% to 83%. However, since the sintered ore under the sieve and the sintered ore under the sieve in the sintering factory is returned to the sintering machine as return ore, zero return ore cannot be achieved, and the sintered ore firing energy remains low. ing.

In addition, in a blast furnace operating method in which sintered ore is sieved with a particle size of 5fflIm and the sintered ore on the sieve is charged from the top of the blast furnace,
The sintered ore under the sieve has a certain particle size, for example 2III! The fine sintered ore is blown into the blast furnace through the blast tuyere, and the small sintered ore is passed through the furnace together with the sieved sintered ore. A method of using sintered ore under the sieve in a blast furnace has also been proposed, which is characterized by charging the sintered ore into the furnace from the top (Japanese Patent Laid-Open No. 61-6204). According to this method, the amount of sintered ore returned is zero, leading to a reduction in sintered ore firing energy.

Furthermore, as a method for producing low-Si hot metal in a coal injection operation, an operation method has been proposed in which powdered ore is injected together with pulverized coal (Japanese Patent Application Laid-open No. 137402/1982).

According to this method, the pulverized coal ratio is 30 to 150 kg/pt
By injecting 5 to 50 kg/pt of fine ore consisting of berent feed or crushed sintered ore powder, St in the hot metal is reduced by a desiliconization reaction (Si+2FeO=SiOt+2Fe).

Furthermore, as a method for producing low Sr and low S hot metal in pulverized coal injection operations, an operation method has been proposed in which basic substances such as limestone and dolomite are injected together with pulverized coal (JP-A-5
7-137403).

(Problems to be Solved by the Invention) However, these methods described above have the following three problems.

■There are cases where large amounts of pulverized coal and sintered ore powder are injected, but pulverized coal and sintered ore powder are not simultaneously injected in large quantities, resulting in raw material waste and sintered ore firing energy. This reduction will not lead to a significant reduction in raw material costs.

■When a large amount of pulverized coal is injected, combustion of pulverized coal within the raceway does not progress sufficiently, resulting in poor ventilation, fluctuations in loading, and cooling of the furnace (sometimes).

■When a large amount of sintered ore powder is injected, smelting reduction may not progress sufficiently at the tip of the raceway, causing wind pressure fluctuations and load drop fluctuations, which may lead to furnace cooling.

The present invention aims to solve the above-mentioned problems in the powder injection operation of a blast furnace in which a large amount of pulverized coal and sintered ore powder is injected. The purpose of this project is to provide a blast furnace tuyere powder injection operation method that achieves a significant reduction in raw material costs under stable blast furnace furnace conditions.

(Means for Solving the Problems) The inventors of the present invention have found that in order to achieve the above object, as a result of conducting research through numerous experiments, (1) the theoretical combustion temperature before the tuyere is within a predetermined range; By setting the weight ratio of oxygen and pulverized coal to a predetermined value or more, the combustibility of the pulverized coal within the raceway is ensured.

(2) If the above measure (2) is taken, even if a large amount of pulverized coal and sintered ore powder are injected at the same time, the molten ore reduction will be ensured by the combustion heat of the pulverized coal.

■Therefore, when transporting pulverized coal and sintered ore powder through the blast furnace tuyere, the theoretical combustion temperature before the tuyere must be within a specified range, and the oxygen/pulverized coal weight ratio during tuyere ventilation must be If it is within the specified range, the combustion of pulverized coal in the raceway and the melting and reduction of the powdered sintered fibers at the tip of the raceway will progress sufficiently, and the operation will be possible without deterioration of furnace conditions such as wind pressure fluctuations and unloading fluctuations. It is possible to continue.

This led us to the following knowledge.

Here, the gist of the present invention is that from the blast furnace tuyere,
More than 150 kg of pulverized coal per ton of pig iron, also 1 ton of iron oxide
50 kg or more is blown at the same time, the theoretical combustion temperature before the tuyere is 1800°C or more and 2600°C or less, and the pulverized coal/oxygen weight ratio during tuyere blowing is within the upper and lower limits shown in the following formulas (1) and (2). This is a blast furnace tuyere powder injection operation method.

(PC)? Carbon in pulverized coal (weight fraction) (PH) + Hydrogen in pulverized coal (weight fraction) (effect) The reason for limiting each operating condition as described above in the present invention is as follows.

If the theoretical combustion temperature before the tuyere (hereinafter simply referred to as "temperature before the tuyere") decreases too much, it will be difficult to maintain the temperature of the hot metal due to insufficient sensible heat of the blast. On the other hand, if the temperature before the tuyere increases too much,
In the present invention, the temperature is limited to 1800 to 2600° C., where the partial pressure of metal vapor such as SiO(g) increases and shelf hanging occurs. Preferably it is 2000-2400°C.

The amount of pulverized coal and iron oxide injected is 150 kg each5.
This is because, from the viewpoint of actual production, if the amount is smaller than this, the purpose of injecting a large amount from the blast furnace tuyere will not be achieved, and no practical benefit will be obtained in the powder injection operation.

Regarding the weight ratio of oxygen and pulverized coal, the lower limit shown in equation (2) is the oxygen concentration at which the carbon in the pulverized coal will be incompletely combusted if the amount of oxygen is less than this, and if the oxygen concentration is less than this, the carbon in the pulverized coal will burn incompletely. A large amount of unburned pulverized coal is brought in, resulting in poor ventilation.
On the other hand, the upper limit shown in equation (1) is the oxygen concentration at which the carbon and hydrogen in the pulverized coal are completely combusted, and the amount of oxygen exceeding this is not necessary for the combustion of the pulverized coal. It is.

The theoretical combustion temperature before the tuyere and the oxygen/pulverized coal weight ratio are each determined within the predetermined upper and lower limit ranges defined by the present invention, depending on the blast furnace operating rate such as the coke ratio and the tapping ratio.

Therefore, when transporting pulverized coal and iron oxide (e.g. sintered ore powder) through the blast furnace tuyeres, the theoretical combustion temperature before the tuyere should be in the range of 1800 to 2600°C, and then The lower limit of the weight ratio of oxygen in the coal to pulverized coal is determined using the above formula (2
) The upper limit of the oxygen concentration at which carbon in pulverized coal undergoes incomplete combustion, as specified by equation (1), shall be within the upper and lower limits of the oxygen concentration at which carbon and hydrogen in pulverized coal undergo complete combustion, as specified by equation (1). For example, the combustion of pulverized coal in the raceway and the melting and reduction of the sintered ore powder at the tip of the raceway have progressed sufficiently, and it is possible to continue operation without deterioration of furnace conditions such as wind pressure fluctuations or unloading fluctuations. Yes, leading to a significant reduction in raw material and fuel costs.

According to a preferred embodiment of the present invention, 30 to 60 kg/pt of a sludge-forming agent may be injected from the blast furnace tuyere if necessary. Examples of the sludge-forming agent include limestone, dolomite, etc. They may be blown together through the same tuyere.

(Example) An embodiment of the present invention will be described based on FIG.

The right side of the center line of the blast furnace 19 shows the injection process of sintered ore powder as an example of iron oxide, and the sintered ore produced in the sintering machine 2 is Multiple i! screens, cold screens, etc. The powder is sieved by i3, and the undersieve is supplied to the powder blowing system 11. on the other hand,
The upper part of the sieve is sieved by a plurality of sieves 4 to 7 installed in the sintering factory, and finally the lower part of sieve 6 is supplied to powder blowing systems 11 to 18, and the sieve part of sieve 6 is sieved by a plurality of sieves 4 to 7 installed in the sintering factory. The upper part is charged as lump raw material from the top of the blast furnace.

The powder supplied to the powder blowing system is stored in a service hopper 11 and then introduced into a blowing tank 13 via an intermediate tank 12. The powder in the blowing tank 13 is fluidized by the gas 14 introduced from the bottom of the tank, transported by the carrier gas 15, and passed through the distributor 16.
The blowing nozzle 18 attached to the tuyere 17
It is blown into the blast furnace 19 through.

Although not shown, a powder blowing nozzle 18 is installed at each blowing tuyere 17, and a plurality of distributors 16 may be installed as necessary, or in some cases, in multiple stages. The number of stages of the inner sieves 4 to 7 may be increased or decreased as necessary.

Next, the left half of the center line of the blast furnace 19 shows the process of blowing pulverized coal and slag forming agent. The coal 20 piled in the yard is
After being stored in the coal hopper 22, a predetermined amount is continuously supplied to the crusher 26 by a rotary feeder 24 installed at the bottom of the hopper.

In the crusher 26, the 150~
It is dried with hot air at a predetermined temperature within the range of 500°C. This hot air may be obtained by burning B gas or the like generated within the steelworks.

The coal pulverized to a predetermined particle size or less is directed to the tuyere 34 by hot air from the hot blast furnace 27 in the blowing system 28.29.3.
The gas is transported to each tuyere 3 via a distributor 33.
4 is distributed and gaseously transported. Then, it is blown into the blast furnace 19 from the tuyere 34 through the blowing nozzle 35. In this case, it is also possible to add hot air and/or cold air to the blowing system after the crusher 26 via the piping 32, if necessary.

In addition, if necessary, after storing the slag-forming agent 21 such as dolomite and limestone loaded in the yard in the slag-forming agent hopper 23, the rotary feeder 2 installed at the bottom of the hopper
5, a predetermined amount of coal is continuously added to the crusher 26.
It is also possible to supply both at the same time. Coal and slag-forming agent supplied at the same time at a predetermined ratio are crushed and mixed in the crusher 26 and blown into the blast furnace through the blast furnace tuyere 34 .

Although not shown, a powder blowing nozzle 35 is installed at each blowing tuyere 34, and a plurality of distributors 33 may be installed as needed, or in some cases, in multiple stages. Although not shown, the systems leading from the yard 21 to the hopper 23 are installed depending on the number of types of slag forming agents used.

In the examples, dolomite, limestone, etc. are used as the slag forming agent, but it may also contain other MgO sources or CaO sources. Alternatively, a slag forming agent containing both MgOa and CaOB may be used.

Below, the powder injection operation of a blast furnace based on the present invention will be explained as follows.
The results of an experiment conducted in a blast furnace (inner volume: 2,700 n) will be explained by comparing them with the results of an experiment based on a conventional method.

First, in carrying out the method of the present invention, the upper and lower limits of the theoretical pre-tuyere combustion temperature were determined based on the operational experience of a conventional B blast furnace (furnace internal volume: 5050%). Figure 2 shows the results.The lower limit set value of the theoretical combustion temperature before the tuyere is determined by the lowest temperature at which it is difficult to secure the hot metal temperature due to insufficient sensible heat of the blast. A value of 1800°C was obtained. On the other hand, the upper limit setting value of the theoretical combustion temperature before the tuyere is S
It was determined by the maximum temperature at which the partial pressure of metal vapor such as iO(g) becomes high and it becomes difficult to lower the load due to shelf hanging, and 2600° C. was obtained as the theoretical combustion temperature before the tuyere.

In addition, the upper and lower limits of the (oxygen/pulverized coal) ratio were determined by conducting various hot tests in a lower experimental blast furnace. Third
The figure shows the test results, and the lower limit of the (oxygen/pulverized coal) ratio is determined by the lower limit of the (oxygen/pulverized coal) ratio, which increases the amount of soot in the packed gas passing through the bed due to a decrease in the combustion rate of pulverized coal, causing unloading problems. Determined from the lowest value, the (oxygen/pulverized coal) reduction limit value is the incomplete combustion of all carbon in the pulverized coal (c+1/20x =
1.5 times the oxygen ffi +4/3 X (weight fraction of carbon in pulverized coal) 1 required for co) was obtained. on the other hand,
The upper limit of the (oxygen/pulverized coal) ratio is such that the pulverized coal combustion rate at the tuyere level is 100%, and even if the oxygen ratio is increased beyond that, it will not contribute to improving the pulverized coal combustion rate and will be wasted. Become(
The upper limit of the (oxygen/pulverized coal) ratio is the complete combustion of all carbon and hydrogen in the pulverized coal (C+0.-CO, H, ÷ 1/20x = HtO). The amount of oxygen required for [(8/3×(weight fraction of carbon in pulverized coal)+8×(weight fraction of hydrogen in pulverized coal)]l was obtained.

The experimental results of the blast furnace tuyere powder injection operation conducted in this way are shown in Table 1. Furthermore, the particle size distribution of the sintered ore under the sieve and the particle size distribution of the pulverized coal used in the experiment are shown in Table 2. The powder used in this example was 1311111 for sintered ore and 110t for pulverized coal + 90% esh, but if necessary, finer sintered ore or coarser coal may be injected. .

First, test period A to test period C in Table 1 are comparative examples using the conventional method. In test period A, the sintered ore was sieved with a sieve size of 3 mm, and the sintered ore above the sieve was charged from the top of the blast furnace, and the entire sintered ore under the sieve was blown into the furnace through the tuyeres by gas transport. The theoretical combustion temperature before the tuyere was set to 2022°C by the action of raising the temperature of the air, but since the sinter was injected with only sinter, the temperature of the powder was not raised sufficiently (smelting reduction did not progress sufficiently, Fluctuations in blowing pressure and unloading occurred frequently, leading to furnace cooling.In addition, in test period B, pulverized coal was blown into the furnace through the tuyere by gas transport.The theoretical combustion temperature before the tuyere was 1763℃, and Since the oxygen/pulverized coal ratio was also low at 1.29, pulverized coal was not sufficiently combusted, resulting in poor air permeability and frequent unloading fluctuations, which led to furnace cooling.Furthermore, during test period C, The sintered ore sifter (-3suw) was blown into the furnace through the tuyere along with pulverized coal to raise the air blowing temperature and increase the enriched oxygen, but the theoretical combustion temperature before the tuyere was 1764'C. and low,
In addition, since the oxygen/pulverized coal ratio was low at 1.43, the combustion of pulverized coal and the melting and reduction of fine ores did not progress sufficiently, resulting in poor ventilation inside the furnace, frequent fluctuations in blowing pressure, and fluctuations in loading. It got cold.

On the other hand, the test period 1 is an example in which the method of the present invention is applied, and the point that the sintered ore sifter (-3+ms) is blown into the furnace through the tuyeres together with pulverized coal is the same as in the case of the above-mentioned period C. In the same way, actions were taken to increase the blowing temperature and enriched oxygen so that the theoretical combustion temperature before the tuyere and the oxygen/pulverized coal ratio fell within the predetermined ranges. As a result, the combustion of pulverized coal and the melting and reduction of fine ore have progressed sufficiently, blast furnace operation has been continued under stable wind pressure and unloading conditions, a significant reduction in raw material and fuel costs has been achieved, and an increase in the pig iron production ratio has been achieved. I was teased.

(The following are blank spaces) Table 1 Table 2 (Effects of the Invention) As stated above, according to the present invention, the blast furnace powder injection operation in which pulverized coal and sintered ore are injected through the blast furnace tuyeres by gas transport It is now possible to continue operations without wind pressure fluctuations or unloading fluctuations, which alleviates coke oven production constraints, reduces sinter calcination energy, and improves production flexibility by increasing the blast furnace tap ratio. It has brought extremely useful effects industrially, such as making it possible to

[Brief explanation of drawings]

Figure 1 is a block diagram showing an example of a device configuration suitable for carrying out the present invention. Figure 2 is the upper and lower limits of the theoretical combustion temperature before the tuyere obtained from the preliminary test results in the example. and FIG. 3 are graphs showing the upper and lower limits of the (oxygen/pulverized coal) weight ratio obtained from the preliminary test results in the example. 2: Sintering machine 17: Tuyere 19: Blast furnace 20: Coal 21: Slag forming agent 27: Hot blast furnace 34: Tuyere

Claims (2)

[Claims] (1) From the blast furnace tuyere, 150 kg or more of pulverized coal and 150 kg or more of iron oxide are simultaneously blown per ton of pig iron, the theoretical combustion temperature before the tuyere is set to 1800°C or more and 2600°C or less, and the pulverized coal/oxygen weight during tuyere blowing. A blast furnace tuyere powder injection operation method that keeps the ratio within the upper and lower limits shown below. [(oxygen/pulverized coal)]_m_a_x=(8/3)×(P
C)+8×(PH) [(oxygen/pulverized coal)]_m_i_n
= (4/3) x (PC) x 1.5 (PC): Carbon in pulverized coal (weight fraction) (PH): Hydrogen in pulverized coal (weight fraction) (2) From the blast furnace tuyere, 30-60k of slag forming agent per ton of pig iron
2. The blast furnace tuyere powder injection operating method according to claim 1, wherein g is blown into the blast furnace tuyere.